An Ecological
Assessment of USEPA
r
Region 8
Streams and Rivers
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
An Ecological Assessment of
USEPA Region 8
Streams and Rivers
This Report was prepared by the following USEPA Region 8, State, and USGS Staff:
Thomas Johnson1'11, Karl Hermann1, Sarah Spaulding2, Blake Beyea3, Chris Theel3, Rosie Sada4,
Wease Bollman5, Jennifer Bowman5, Aaron Larsen6, Kevin Vining7, Jeff Ostermiller8, Dave
Peterson9, Eric Hargett10, and Jeremy Zumberge10.
1 U.S. Environmental Protection Agency, Region 8, Denver, CO
2 U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO
3 Colorado Department of Public Health and Environment, Denver, CO
4 Montana Department of Environmental Quality, Helena, MT
5 Rhitron Associates, Inc., Missoula, MT
6 North Dakota Department of Health, Bismarck, ND
7 U.S. Geological Survey, Bismarck, ND
8 Utah Department of Environmental Quality, Salt Lake City, UT
9 U.S. Geological Survey, Cheyenne, WY
10 Wyoming Department of Environmental Quality, Cheyenne, WY; Sheridan, WY
11 point of contact for this Report
ii
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Additional Participants
The following organizations participated in the development of the EMAP-West project and/or in
data collection and analysis for EMAP-West as it relates to this regional report:
U.S. EPA, Office of Research and Development in Corvallis, OR; Duluth, MN; Las Vegas, NV
Colorado Division of Wildlife, Denver, CO
South Dakota Department of Environment and Natural Resources, Pierre, SD
South Dakota Department of Game, Fish and Parks, Pierre, SD
U.S. Geological Survey, Rapid City, SD
iii
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Table of Contents
Participants ii
Executive Summary v
Introduction 1
Colorado 18
Montana 38
North Dakota 62
South Dakota 84
Utah 96
Wyoming 106
Middle Rocky Mountains 123
Northwestern Great Plains 131
Northern Cultivated Plains 140
Upper Missouri River Basin 151
EPA Region 8 160
Overall Conclusions & Recommendations 170
References 173
iv
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Executive Summary
This Region 8 assessment presents the condition of streams in the states within U. S.
Environmental Protection Agency (EPA) Region 8 using measures of biotic condition, chemistry
and habitat. This study was completed as a portion of the western EMAP (Environmental
Monitoring and Assessment Program) study. While previous reports described the condition across
the entire West, or subregions of the West, this report examines individual states and some
ecoregions. Specifically, EPA Region 8 contains the six States of Colorado, Montana, North
Dakota, South Dakota, Utah, and Wyoming. Each of these is represented by a separate chapter,
along with individual chapters for the Middle Rockies, Northwestern Great Plains, Northern
Cultivated Plains, Upper Missouri River Basin, and EPA Region 8 as a whole.
Sites were selected for sampling based on a probability design. This design provided
estimates of stream length with a known confidence in several "condition classes" (good or least-
disturbed, fair or moderately-disturbed, and poor or most-disturbed). A total of 400 probability sites
were sampled within the Region, with others sampled as potential reference sites. An important
design goal was to have at least 50 sites per state in order to have a statistically valid survey for
each state.
The main purposes of this study were to 1) develop (or use previously developed) biological
indicators derived from the biota living in the streams (fish, aquatic insects, algae); 2) assess
ecological condition using biological, chemical and physical measures; 3) rank the relative
importance and severity of stressors (chemical, physical or biological); and, 4) enhance the capacity
of states to design surveys for monitoring and assessment. This work is critical for understanding
the present condition of rivers and streams in Region 8, in helping to establish a baseline for water
quality management, and to improve the tools for monitoring in the West.
All EPA Region 8 states participated in the work and assessments were completed by many
of the individual states themselves. Development of bioindicators was accomplished in many areas
of Region 8, at least partly as a result of this work and in some cases by states for their individual
water quality programs using EMAP data. At least two bioindicators were used in each assessment
area; in some case there were three or four bioindicators. Stressors were evaluated at the scale of
both the state and ecoregion to determine the extent of particular stressors. In addition, the risk to
biota of particular stressors was determined at the larger, regional scale.
In this document, state chapters report individual findings of biological condition and
stressor extent. Many of these chapters were adapted from individual reports from states. They are
included here in an edited version. Other state chapters were created specifically for this report.
Several ecoregions were selected to report on biological condition and stressor extent (the Middle
Rocky Mountains, the Northwestern Great Plains, and a collection of ecoregions referred to as the
Northern Cultivated Plains). Additionally, the Upper Missouri River Basin and the entire EPA
Region 8 were assessed and biological condition, stressor extent and relative risk were reported.
The overall results for Region 8 are summarized here and each state chapter more closely
examines findings at the state level. Two biological indicators were applied to the entire Region,
macroinvertebrate MMIs (multi-metric indices) and periphyton MMIs. Others, such as
v
-------
An Ecological Assessment of (JSEPA Region 8 Streams and Rivers
macroinvertebrate predictive models and fish MMIs, were used in some state and ecoregional
assessments.
Using all macroinvertebrate MMIs (some developed in this study, others applied from state
assessment work), 58% (83,879 km) of Region 8 was in least-disturbed condition and 25% (35,295
km) was in most-disturbed condition. Periphyton MMIs found fewer sites (or stream length) in
least-disturbed condition at 43% (61,976 km), but a similar amount of stream reach in most-
disturbed condition at 23% (32,582 km).
Stressor indicators were ranked in terms of extent from highest to lowest. Human riparian
disturbance, stream habitat complexity, and streambed stability were the greatest habitat stressors.
Riparian disturbance and impact to habitat complexity affected 30% or more of stream length.
Lower streambed stability impacted 23% and total phosphorus was close behind at 21 %. Fish tissue
was high for mercury content in 18% of stream length in Region 8. That is, at least one individual
fish in 18% of the stream length had mercury concentrations that exceeded the ecologically derived
benchmark for mercury in tissue. Relative risk (the analysis of the strength of the impact of a
particular stressor to a component of the biota) was done at the scale of the Region. While nutrient
concentrations were elevated in a lower number of stream kilometers than habitat stressors,
elevated nutrient concentrations had a greater impact on both macroinvertebrates and periphyton.
An exception to this finding was for streambed stability, in which unstable streambeds resulted in
strong impacts on macroinvertebrate indicators.
vi
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Introduction
This report documents an ecological assessment of streams and rivers in the six states of
U.S. Environmental Protection Agency Region 8. It is based on the results of EPA's Environmental
Monitoring and Assessment Program (EMAP) during the years 2000-2004. The major objective of
that study (EMAP-West) was to determine the condition of the streams and rivers throughout the
western United States and to demonstrate the utility of the EMAP approach to environmental
monitoring and assessment at varying spatial scales. This report draws much of its content from
three previously published documents, Environmental Monitoring and Assessment Program
(EMAP) Western Streams and Rivers Statistical Summary (Stoddard et al 2005a), An Ecological
Assessment of Western Streams and Rivers (Stoddard et al 2005b), and Wadeable Streams
Assessment—The States Assess the Nation's Streams (U.S. EPA 2006a) but differs in that it focuses
on reporting at the level of EPA Region 8 and the states within it, rather than the West as a whole.
Starting in the 1980's, the EMAP approach successfully developed scientific tools to
monitor and assess trends of the Nation's aquatic ecological resources with a known statistical
confidence (U.S. EPA 2000). A probability-based design and EMAP sampling methods were first
used in the Mid-Atlantic region (U.S. EPA 2000). This approach has recently been expanded
nationwide to assess a range of waterbody types, including wadeable streams, lakes, larger rivers,
coastal areas, and wetlands.
The biological condition of flowing waters was determined through the use of biological
assemblages. The biota, including aquatic invertebrates (fish), benthic macroinvertebrates (aquatic
insects, snails, mussels, worms and crustaceans), and periphyton (diatoms) are particularly relevant
to determining the health of freshwater systems. The species of organisms that are able to survive
and their abundances reflect the stresses that impact a stream. Organisms integrate the physical and
chemical habitat over time, reflecting the health of their surroundings. An aim of assessment is to
determine the condition of streams and rivers by measuring appropriate indicator taxa and combine
the results of biotic measures into indices.
Additional measurements of the physical, chemical and habitat factors that influence stream
condition allowed for an assessment of particular factors that might have a negative effect on
biological condition. The relative importance of these potential stressors on the biological
assemblages was also assessed. The most important threats to the aquatic biological condition were
analyzed, as well as how much risk these stressors posed to aquatic ecosystems.
The EMAP-West project sampled over 1340 perennial streams (some streams were sampled
multiple times) throughout the western U.S. in the years 2000 through 2004. This project included
both wadeable streams and non-wadeable rivers. Sampled sites were chosen randomly to represent
the entire population of flowing waters in the West (965 sites), or "hand-picked" to represent the
best possible condition ("reference sites"). The project developed as a partnership between twelve
western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon,
South Dakota, Utah, Washington and Wyoming), the U.S. Geological Survey (USGS), academic
institutions, EPA Regions 8, 9 and 10 and the EPA Office of Research and Development. The
EMAP-West study area is presented in Figure 1, with the location of the mountains, plains, and
xeric regions. These three physiographic regions served as the basis for much of the indicator
1
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
development for the west-wide study (Stoddard et al 2005b). This particular report focuses only on
the EPA Region 8 States of Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming,
and presents results at the state and ecoregion level.
SI
D
I I States
1 [ Xeric Regions
Plains Regions
| Mountain Regions
"I
f v^-er
t \ \
- V" .
I • u
.\
250
500
1,000
kilo mete rs
Figure 1. EMAP-West study area and probability sites.
2
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Sites were chosen according to a probability design, where each site has a known
probability of being selected for sampling, and collectively the sites represent the population of
flowing waters in a region. This probability design uses the same philosophy as an opinion poll,
bringing the statistical rigor of sample surveys to environmental assessment. The sample survey
approach is especially cost-effective if the population is large or if it is unnecessary to census the
entire resource to reach the required level of precision to describe its condition. The design team
used the U.S. Geological Survey (USGS) National Hydrography Dataset (NHD) to identify the
location of perennial streams. Site selection included weighting of stream orders to balance the
number of stream sites from each stream order size class. This was done since a truly random
selection would result in selecting mostly first order streams. The design was weighted to ensure
that larger order streams were sampled and later for analysis the weights are recalculated to account
for the larger number of first order streams. In addition, spatial distribution ensured that at least 50
sample sites were contained within each state. More detail on probability designs can be found in
Olsen et al (1999). The target population in this report was the perennial streams and rivers of EPA
Region 8 smaller than the very largest rivers ("Great Rivers") of the Missouri and lower Colorado.
Extra sites were added to the Upper Missouri Basin to allow for an assessment of the basin
as a whole. Sites sampled in Region 8 included probability and potential reference sites (Figure 2).
A total of 786 sites were sampled in the region, 430 of which were probability sites. The relative
weight that a given site has on the design is presented in Figure 3. In other words, the larger the
symbol the more stream length it represents. Symbols are generally larger in the mountains since
the sites sampled there represent much more stream length than in the plains or xeric regions. In a
design that did not force sites to be drawn in drier areas with fewer streams, the vast majority of
sites would be from the mountains and there would be little elsewhere. The purpose of this study
was to assess the condition of streams in the West, not just the mountains. Therefore, sites were
specifically chosen to represent plains and xeric regions and each mountain site chosen represents
more stream length per site. Figure 4 presents the perennial stream length of each assessment unit
(assessment units are presented in Figure 7). The actual amount of stream length assessed is
somewhat less due to site access issues.
3
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
La-
*
• if, . , f-
• : v, » »
• *•«» i*i , »
* A
¦" -£3TV
- ~- « f»
I
• •
_ A ^
Region 8 States
Tribal Lands
Probability Sites
Hand-Picked Sites
Kilometers
¦igure 2. Location of probability (black) and hand-picked (blue) sites in EPA Region 8.
Once sites were selected, an office evaluation and field reconnaissance was conducted to
determine if the streams labeled as perennial in NHD were actually flowing during the sampling
season. If not, they would be considered non-perennial and the site replaced with a perennial
stream. Other factors may have also precluded sampling a given site, such as being denied
permission for access to the site by the landowner, physical barriers to sampling, or safety concerns
for the field crews. A list of reserve sites existed for each state to draw from when replacements
were needed.
4
-------
An Eccioaicai Assessment of USEPA Region 8 Streams and Rivers
oo
o°
jj.® 0
W 9 *
MT
O •
o
• o °
ND
9 ° So . «
x ••
;>. •
^ r ^ : * < :
$ „
- 0 o rf
%
*
. * ~ *\
• o o
~»o
~ O
oo
SD *
03 O «
C6o
O 9
e
. ~ *. 0 * *
«o * '
% *
WY
O o
o • ®
* -
125 250
500
kilometers
J.
° O
a
ooo .
° *z
<8 ° v
CO
© «®» <£
°«
Proportion of Stream
Length Represented
] States
Figure 3. Relative weight of each site (stream length per site).
5
-------
An Ecoioaicai Assessment of (JSEPA Region 8 Streams and Rivers
Perennial Stream Length by Assessment Unit
Region 8
Mountain Region
Plains Region
Xeric Region
Upper Missouri Basin
Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
Middle Rockies
Northwestern Great Plains
Northern Cultivated Plains
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000
Stream Length (km)
figure 4. Perennial stream length in each assessment unit.
The sampling methods were consistent across the geographic area and across stream sizes.
Methods were developed to allow a four-person crew to collect data in a single day visit, on
vertebrate, algal, and macroinvertebrate assemblages, physical and chemical habitat, invasive
riparian plant species, and major toxic contaminants in fish tissue (Peck et al 2005a; Peck et al
2005b). All of the crews were trained to use identical sampling methods and the data were subject
to strict quality assurance procedures (see Stoddard et al 2005b). At each site, crews laid out the
sample reach and the 11 transects for data collection (Figure 5). Field crews collected water
samples for chemical analysis and macroinvertebrate and periphyton samples were collected at
each transect and sent to taxonomists for identification and quantitative analysis. Fish were
collected along the entire reach and identified in the field. A few fish were kept as voucher
specimens and for fish tissue analysis. Crews also recorded information about the physical
characteristics of the stream and adjacent riparian area. Similar data were collected on non-
wadeable streams, with boats used in sampling.
6
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Upstream End of
Sampling Reach
Channel/
Riparian
Cross
Section
Transect
Riparian Vegetation &
Human Disturbance
Instream Fish Cover
Thalweg
Profile .
Intervals'
Woody Debris1 —- MlhrT
Tally (berw«n
transects)
Downstream End
of Sampling Reach
igure 5. Physical habitat sampling protocol (from U.S. EPA 2006a)
EPA Region 8
EPA Region 8 consists of the States of Colorado, Montana, North Dakota, South Dakota,
Utah, and Wyoming. It is roughly one-third federal land (primarily managed by the U.S. Forest
Service and Bureau of Land Management) and two-thirds private land. About 7% is under tribal
jurisdiction, representing 27 Tribal Nations. It is topographically and climatically diverse, including
portions of the Great Plains, the Rocky Mountains, and the canyonlands and deserts of the
Colorado Plateau and Great Basin. Within this geographic region are the headwaters (and much of
the main stems) of the Missouri, the Arkansas, the Rio Grande, the Snake, and the Colorado Rivers.
Portions of 20 Level III Ecoregions are contained within EPA Region 8. Ecoregions (Omernik
1987) are areas of similar topography, land cover, vegetation, and climate. The highest level (Level
I) includes areas as large as the entire Great Plains or the Western Mountains. Level III divides that
much further into various subareas. These are still fairly large and a separation to a smaller Level
7
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
IV has been performed for much of the United States. Ecoregions form the basis for much of the
indicator development and assessment work in this report. The Level III Ecoregions and states in
EPA Region 8 are shown in Figure 6.
Noitliein
Rockies
Northwestern Gieat Plains
Noitliein
Basin &
Range
Wbsatch &
Hi lit.1
MoillItaillS
WyouiiMj Basin
Ceiiti.il
Basin &
RaiMJ*
Col oi ado
Plateau
Soiitliein
Rockies
Mojave
Basin ^
Range
Aiizona& New I
Pl.i1e.iu
Noitliein
Glaciated Plains
Lake
Atjassiz
Plain
Soinn western
Tablelands
0*)
0 125 260 SM
Wlometers
^igure 6. Level III Ecoregions within EPA Region 8.
Western
Com Belt
PI.1NIS
Canadian
Rockies
Northwestern Glaciated Plains
Idaho
Batholith
Mddle RocKies
Nelxaska
Sanill tills
Numerous and varied stressors to aquatic systems are present across EPA Region 8. Some
areas, such as Colorado's Front Range, Utah's Wasatch Front, and some mountain cities are
experiencing rapid population growth and associated impacts to streams and rivers. Oil and gas
extraction has increased dramatically in a number of areas such as northeastern Wyoming,
southwestern Colorado and eastern Utah. Other areas experience the more traditional impacts that
have existed in the West for many years, such as timber harvest, mining, grazing, and crop
agriculture. Row crop agriculture is prevalent in eastern North and South Dakota and northeastern
Colorado. Irrigated agriculture is common in northeastern Colorado and in many valleys in
throughout the Region and can have great impacts where it does exist (stream dewatering,
increased nutrient, selenium and salinity concentrations). The greatest impacts to aquatic systems in
the West are the result of increased nutrients and sediment, and diversion of streams for irrigation
8
-------
An Ecological Assessment of USEPA Region 3 Streams and Rivers
and water supplies. Toxic impacts are more localized, resulting from mining, pesticide use, or spills
of toxic substances.
Assessment Units
For the purposes of this assessment, reporting occurs at varying geographic areas referred to
as assessment units. Assessment units include each individual state, several level III and aggregated
Level III Ecoregions, the Upper Missouri River basin, and EPA Region 8 as a whole. The
ecoregions (based on Omernik 1987) that serve as assessment units include the Middle Rockies
(Ecoregion 17), the Northwestern Great Plains (Ecoregion 43), and the northern Cultivated Plains
(Ecoregions 46, 47, and 48) (Figure 7).
MT
ND
~F\
SD
>
^
\
WY
250
125
Kilometers
UT
CO
7igure 7. Location of assessment units.
9
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Ecological Assessment
Ecological assessment includes the determination of aquatic condition using biological,
chemical, and physical measures. The biological condition of streams and rivers is determined by
assessing the condition of biotic assemblages. Organisms within aquatic ecosystems integrate the
many forms of human disturbance, which are then assessed in regard to biotic integrity. This
assessment is designed to address the objective of the Clean Water Act: to restore and maintain the
chemical, physical, and biological integrity of the Nation's waters (Frey 1977; Karr and Dudley
1981; Stoddard et al 2005b). This assessment looks at all three of these components (chemical,
physical and biological).
An analysis of stressors is also an important part of an assessment. Stressors are the factors
(particularly human influenced) that negatively impact aquatic systems (Stoddard et al 2005b).
Stressors can be chemical, physical or biological. Examples of chemical stressors are toxic
compounds or excess nutrients (nitrogen and phosphorus). Most physical stressors are created by
the modification of the physical habitat of a stream network. Excess sedimentation, bank erosion,
and loss of streamside vegetation can degrade biotic integrity. Biological stressors include non-
native or invasive species in the stream or riparian area. A measure of how common and how
severe stressors are is a major element of an ecological assessment.
Ecological Indicators
The biological condition of aquatic systems is estimated by analyzing the composition and
relative abundance of key biotic assemblages representing biotic integrity. Biotic integrity is
defined as "the capability of supporting and maintaining a balanced, integrated, adaptive
community of organisms having a species composition, diversity, and functional organization
comparable to that of the natural habitat of the region" (Karr and Dudley 1981; Frey 1977;
Stoddard et al 2005b). This assessment focused on the community composition of aquatic
vertebrates (fish), macroinvertebrates (aquatic insects, crustaceans, worms and mollusks), and
periphyton (diatoms). In this assessment the term periphyton is used to refer to the indicators
developed using algae, even though diatoms were the only algal organisms used. Periphyton has
become the accepted term to refer to indices developed using this aquatic community.
One measure of biotic integrity is the Index of Biotic Integrity (IBI). The IBI is a multi-
metric index that is a sum of scores for a variety of individual measures, or metrics. These metrics
make up characteristics of biotic integrity, such as, taxonomic richness, habitat and trophic
composition, and sensitivity to human disturbance. The original IBI was developed for fish in
Midwestern streams, but has been modified many times for other regions, taxonomic groups, and
ecosystems (Barbour et al 1995; Karr 1981). In this work, a modification of the IBI was used
known as the multi-metric index (MMI). An MMI differs slightly from an IBI in that IBI metrics
generally are selected a priori, whereas MMI metrics typically are selected a posteriori using an
empirical approach (Peterson et al 2007).
In the EMAP-West study (Stoddard et al 2005b) one MMI each was constructed for the
mountains, plains, and xeric regions. For this regional assessment, a number of MMIs were used
depending on the given state or ecoregion. Some were developed specifically from this work;
10
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
others were developed by states for their bioassessment programs (but including EMAP data in that
development). MMI development for each area is described in detail in each assessment unit
chapter. These include MMIs for fish, macroinvertebrates, and periphyton, where possible. MMIs
were developed at the scale of Level III Ecoregion, and in some cases, Level III Ecoregions within
states. Smaller ecoregions are more homogeneous and contain less environmental variability.
Typically, MMIs developed within such small regions perform quite well. However, a sufficient
number of sites are needed to develop a successful MMI. In reality, the approach is to balance the
size of ecoregion (minimize heterogeneity of sites) with adequate number of sites to represent that
ecoregion.
An alternative approach to balancing ecoregion and number of sites is to utilize predictive
models. In this approach, the condition of macroinvertebrate assemblages is reported as an
Observed/Expected (O/E) index (Hawkins 2005; Hawkins et al 2000; Van Sickle et al 2005; Wright
2000). An O/E score is a measure of the number of macroinvertebrate taxa expected at a site based
on natural environmental parameters over the macroinvertebrate taxa actually observed at that site.
The taxa expected (E) at individual sites are predicted from a model developed from data collected
at reference sites. The model predicts the taxa that should occur under natural environmental
conditions. By comparing the list of taxa observed (O) at a site with those expected to occur, the
proportion of expected taxa that have been lost can be quantified as the ratio of O/E.
O/E values range from 0 (none of the expected taxa are present) to slightly greater than 1
(more taxa are present than expected). O/E values are interpreted as the percentage of the expected
taxa present (U.S. EPA 2006a). Each tenth of a point less than 1 represents a 10% loss of taxa at the
site. Therefore, an O/E score of 0.9 indicates that 90% of the expected taxa are present and 10% are
missing. O/E values need to be interpreted in context of the quality of reference sites used to build
the predictive models. There will be a lower expectation for regions with lower-quality reference
sites. Although an O/E value of 0.8 means the same thing regardless of region (20% of taxa have
been lost relative to those regional reference conditions), the true amount of taxa loss will be
underestimated if reference sites are of low quality (U.S. EPA 2006a).
As with MMIs, the particular O/E model used for assessment varied by state and each
assessment unit chapter contains a discussion of their individual development.
Stressor Indicators
Human activities can produce effects that may be stressful to aquatic ecosystems. A list of
important stressors was selected from each of the chemical, physical, and biological categories.
They do not include all possible stressors and some important stressors were not included because
there is currently no way to assess them at the site scale (e.g., water withdrawals for irrigation).
The stressor indicators used in this report are direct measures of stress in the stream or
adjacent riparian areas. They do not include landuse or land cover alterations such as row crops,
mining or grazing, but indicators that would be expected to result from those types of activities.
This assessment focuses on the stressors themselves, rather than on their sources.
11
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Chemical Stressors
The indicators of chemical stress assessed were two nutrients (total phosphorus and total
nitrogen), mercury in fish tissue, and in some cases, states chose to add specific conductance.
Nutrients, such as phosphorus and nitrogen, enter streams in precipitation runoff from agricultural
operations and from wastewater discharges. Excess nutrients entering waters may negatively affect
the biotic condition of streams. For example, phosphorus can stimulate growth of algae, as well as
shift the composition of species present. When the algae eventually die, and if algal growth has
been excessive, the respiration of decaying organic matter can deplete oxygen in the water. The
resulting lack of oxygen is harmful to invertebrates and fish. Phosphorus is found in fertilizers and
nitrogen sources include fertilizers, wastewater, and animal wastes (Stoddard et al 2005b).
The mercury content in fish tissue was analyzed at many sites in the EMAP-West study.
Sources of mercury in the environment include: 1) combustion of coal, industrial and residential
waste; 2) mining; 3) use of herbicides and fungicides; and 4) effluents from processing of pulp,
paper and textiles (Stoddard et al 2005b). Airborne mercury is widespread and common in rain and
snow across most of the U.S. Once it reaches lakes and streams, mercury can be converted to a
toxic form, methylmercury, by bacterial activity, taken up by organisms into their tissues, and
accumulate in higher trophic level species. Fish were sampled for whole-body mercury
concentrations. Sites were considered stressed by mercury if any fish from that site contained
mercury concentrations that exceeded the levels established for the protection of wildlife (0.1fjg/g)
(Lazorchak et al 2003).
Excessive salinity occurs in areas with high evaporative losses of water, and can be
exacerbated by repeated use of water for irrigation, or by water withdrawals (Stoddard et al 2005b).
Both conductivity and total dissolved solids (TDS) can be used as measures of salinity, but in this
report, where reported, conductivity was used.
Physical Habitat Stressors
Streams may be impacted by physical disturbances, resulting in the degradation of stream
habitat. For example, fine sediment can be delivered to the stream channel through erosion from
improperly managed grazing, agricultural runoff, development, or mining. In all these cases, the
removal of natural vegetation allows for higher loads of fine sediment to enter streams that would
normally be held on land. Tilling ground to the edge of stream banks, building roads across or
along streams, dredging and straightening stream channels, and building dams or other diversion
structures in the stream channel may destabilize stream banks and change substrate size and
composition (Kaufmann et al 1999). This destruction of riparian habitat can affect the stability of
the stream channel, increase water temperature from loss of shading, and increase the sediment
load. Excess fine sediment can fill in fish spawning areas and reduce habitat for aquatic
macroinvertebrates, a major food source for fish.
Generally, in this assessment four aspects of habitat were used to determine habitat quality,
though not necessarily in every assessment unit. The four were streambed stability, habitat
complexity, riparian vegetation, and riparian disturbance.
12
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Streambed Stability
The substrate of a stream channel is one of the most important physical components for
organisms that inhabit a stream. A stream bottom with excessive amounts of fine sediment is likely
to contain a degraded aquatic macroinvertebrate community, possibly affecting fish that rely on
stream invertebrates for food. Relative bed stability (RBS) is a measure used to determine if the
sediment supply to the stream is higher or lower than natural (Kaufmann et al 1999). It is a ratio of
the substrate size of observed sediments to the size of sediment that a stream can move during its
flood stage. RBS is calculated using the channel shape, size, slope and other physical
characteristics of the stream channel. The RBS ratio differs naturally among regions, depending
upon landscape characteristics such as geology, topography, hydrology, natural vegetation, and
natural disturbance history.
The RBS Index can be lower (finer, more unstable streambeds) or higher (coarser, more
stable streambeds) than expected based on the range found in least-disturbed reference sites. Both
high and low values are considered to be indicators of ecological stress. Excess fine sediments can
destabilize streambeds when the supply of sediments from the landscape exceeds the ability of the
stream to move them downstream. A lower than expected streambed stability value may result
either from high inputs of fine sediments (from erosion) or increases in flood magnitude or
frequency (hydrologic alteration) (Stoddard et al 2005b). The instability (low RBS) resulting from
hydrologic alteration can be a precursor to channel incision and arroyo formation. Streams with
higher than expected streambed stability can also be considered stressed. Very high bed stability is
typified by hard, armored streambeds, such as those often found below dams where fine sediment
flows are interrupted or within channels where banks are highly altered (e.g., paved or lined with
rip-rap) (Stoddard et al 2005b).
Habitat Complexity
The most diverse fish and macroinvertebrate assemblages are found in streams and rivers
that have complex forms of habitat, such as large wood, boulders, undercut banks, or tree roots
(Stoddard et al 2005b). Human use of streams and riparian areas can result in the simplification of
this habitat, with potential effects on biotic integrity. For this assessment, a measure (Kaufmann et
al 1999) was used that sums the amount of in-stream habitat consisting of undercut banks, boulders,
large pieces of wood, brush, and cover from overhanging vegetation within a meter of the water
surface. The higher the value, the more kinds and amount of habitat complexity was found.
Riparian Vegetation
The presence of a complex, multi-layered vegetation corridor along streams and rivers is a
measure of how well the stream network is buffered against sources of stress in the watershed.
Intact riparian areas can help reduce nutrient and sediment runoff from the surrounding landscape,
prevent bank erosion, provide shade to reduce water temperature, and provide leaf litter and large
wood that serve as food and habitat for stream organisms (Stoddard et al 2005b).
The presence of canopy trees in the riparian corridor indicates longevity; the presence of
smaller woody vegetation typically indicates that riparian vegetation is reproducing, and suggests
13
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
the potential for future sustainability of the riparian corridor (Stoddard et al 2005b). For this
assessment a measure of riparian vegetation complexity was used that sums the amount of woody
cover provided by three layers of riparian vegetation: the ground layer, woody shrubs, and canopy
trees (Kaufmann et al 1999). The higher the value the more riparian vegetation in multiple layers
was found. This measure was used in all ecoregions, including areas where trees do not dominate
the landscape (e.g. plains regions). It is still useful as a measure even in those areas since it
measures the total riparian vegetation of the stream corridor and reference sites in the plains region
were used to assess the quality of streams based on this metric.
Riparian Disturbance
The condition of the riparian area is very important for the condition of the stream.
Streambank vegetation provides shading that moderates the stream temperature; it stabilizes banks,
buffers streams from an influx of sediment or other pollutants, and through leaves and other
material provides a source of nutrients to aquatic life. In order to determine the condition of the
riparian area, a measure of the visual human disturbance was used (Stoddard et al 2005b). This
measure involved noting the presence of various types of impacts (roads, cropland, buildings,
pipes, mines, etc.) and their proximity to the stream at 11 transects. Those in the stream or on the
bank received the highest weighting; those more than 10 meters away received the lowest. The
impacts for each transect were then averaged into a final metric. A higher value represented more
human disturbance. The index ranged from 0 (no observed disturbance) to 5.5 (many types of
disturbance observed in the stream or on the banks, throughout the reach).
Biological Stressors
Non-native or invasive species can stress the native biota of an aquatic system. Non-native
species can either prey on, or compete with, native species and when non-native species become
established, their presence conflicts with the definition of biotic integrity in the Clean Water Act
("having a species composition, diversity, and functional organization comparable to that of the
natural habitat of the region") (Stoddard et al 2005b). In many areas of the West non-native fish
were purposely introduced for sport fishing, therefore, while technically a biological stressor, in
many places the streams are managed for a non-native species. This assessment reports on the
presence of non-native fish as an indicator of potential stress, primarily to provide information
about how widespread they are in EPA Region 8, but it does not treat them as a stressor to the same
extent as chemical or physical degradation. The west-wide report also focused on exotic crayfish
and clams and their potential impact (Stoddard et al 2005b). They were not included in this
assessment since they were limited in Region 8 to relatively few sites.
Terrestrial invasive plants were also collected. The presence or absence of 12 invasive
plants in the riparian areas adjacent to each stream reach was noted. The 12 were Common
Burdock, Giant Reed, Cheatgrass, Musk Thistle, Canada Thistle, Teasel, Russian-olive, Leafy
Spurge, English Ivy, Reed Canary Grass, Himalayan Blackberry and Salt Cedar. All were found
somewhere in Region 8 with the exception of Himalayan Blackberry. The actual list of species,
however, varied from state to state. This list is only a subset of the full set of plants invading
western riparian areas. As a result, the data cannot be used to assess the status of riparian plant
invasions throughout the region, but only serves as an indication of invasive plant presence.
14
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Setting Expectations
An assessment of biological condition requires the comparison to some standard of "least-
disturbed" condition (Stoddard et al 2005b; Bailey et al 2004; Hughes 1995). If numeric biological
criteria existed for a given area the comparison would involve simply determining if a score for a
site was above or below that standard. However, in most cases there is no numeric standard to
compare to, at least biologically. Therefore, in this assessment it was necessary to derive a set of
least-disturbed sites to serve as a reference by which to compare the population of streams in a
given area.
Least-disturbed condition, however, varies depending on the location and human influence
in an area (Stoddard et al 2005b). This benchmark was chosen because of the difficulty in
estimating historical conditions. Almost every place has seen some degree of human influence,
especially in the plains regions. Therefore, determining the least disturbed condition for an area
can be difficult. The goal is to select sites that reflect the natural variability across the landscape
and to select sites whose condition is "the best of what's left" in a given area (Stoddard et al
2005b). Within the population of reference sites there are two sources of variability: natural and
that due to human activities (U.S. EPA 2006a). Considerable natural variability exists in an area
the size of a Level III Ecoregion and a diversity of reference sites is necessary to represent this
range of habitats. Human activities also vary with ecoregion and some have much less impact than
others. Finding reference sites is more difficult in those areas with extensive human impacts and
those that do exist tend to have more variability (U.S. EPA 2006a).
For the EMAP-West report (Stoddard et al 2005a; Stoddard et al 2005b) a screening method
was devised for determining least-disturbed sites for use in assessing biological indicators. This
served as the basis for this assessment but was modified by each of the Region 8 states. In the
original screening, the chemical and physical data collected at each site was used to determine
whether any given site was in least-disturbed condition for its ecoregion. Data on the biological
assemblages themselves was not used since they are the basis for the ecological assessment and to
use them would constitute circular reasoning. For each of the stressor indicators, a similar process
was used for identifying least disturbed sites according to specific criteria, but excluding the
specific stressors themselves from the criteria identifying the sites. For example, to derive least
disturbed sites for assessment of relative bed stability, all substrate measurements were removed
from the screening criteria. The screening method for least disturbed site determination is described
in more detail in Stoddard et al (2005a and 2005b). Each assessment unit chapter describes further
any deviations from this method.
The reference site approach (Bailey et al 2004; Hughes 1995) was then used to set
expectations. The range of conditions found in the least-disturbed or "reference sites" describes a
distribution of values, and extremes of this distribution are used as thresholds to distinguish sites in
relatively good condition from those in poor condition. One common approach is to examine the
range of values (e.g., for a particular MMI) in all of the reference sites in a region, and to use the
5th percentile of this distribution to separate the most disturbed sites from moderately disturbed
sites. Similarly, the 25th percentile of the reference distribution can be used to distinguish between
moderately disturbed sites and those in Least Disturbed Condition (Stoddard et al 2006a; Stoddard
et al 2005b). For those areas with fewer and potentially lower quality reference sites, expectations
15
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
were often set differently, using varying percentiles to compensate for this. In setting thresholds for
stressors, expectation setting often deviated from the 5th and 25th percentile method because leaving
out a stressor in reference site screening, can reduce the confidence in the reference site population
for that particular stressor (see above). Since these threshold-determining methods varied among
states and ecoregions, more details on how thresholds were set can be found in each assessment
unit chapter. Throughout this report the terms least-, moderately- and most disturbed will be used
for designating the various condition classes.
Ranking of Stressors and Relative Risk
There are two common approaches to define the importance of a stressor. One approach is
to define the extent of a stressor; the second is to define its severity. Both pieces of information are
biologically relevant. The first is determined by understanding the extent, in stream length, of a
stressor in comparison to other stressors. The second involves determining severity to the biotic
community and the relative effect (greater or smaller than that of other stressors). Each of these
measures provides a different understanding of potential impact. This assessment presents both as
separate rankings: 1) relative extent and 2) relative severity of stressors to streams and rivers.
To address the question of stressor severity, the concept of "relative risk" was borrowed
from epidemiology (Van Sickle et al 2006). For example, there is a greater risk of developing heart
disease if one has high cholesterol levels. These results are often presented in terms of a relative
risk ratio (e.g., the risk of developing heart disease is four times higher for a person with total
cholesterol level of 300 mg than for a person with total cholesterol of 150 mg). In aquatic
assessment terms, the relative risk ratio represents the proportional increase in the likelihood of
finding a biological indicator in most disturbed condition when the stressor is also in the most
disturbed condition class (see Stoddard et al (2005b) for the details of relative risk calculations).
Because different biological assemblages are expected to be affected by different stressors, relative
risk is calculated separately for each of the biological indicators presented in this assessment, where
possible. Since certain stressors are known to correlate with one another, for the relative risk
calculations, stressors were combined into various groups. This is described more fully in the
chapters where this analysis is reported.
A relative risk value of one indicates that there is no association between the stressor and
the biological indicator, while values very much greater than one suggest greater relative risk.
Confidence intervals are presented for each ratio to show when a risk is significant. When the
confidence intervals for any given ratio fall below a value of one, the relative risk is not statistically
significant. On the other hand, a high relative risk value should not be considered to mean that the
stressor is causing the effect on the biota, only that it is associated.'
Because a relatively high number of sites are necessary to determine relative risk, this
analysis was only done for larger areas such as the entire Region 8 and the Upper Missouri River
Basin. Unfortunately, the state and ecoregion scale generally has too few sites to accurately
determine relative risk.
16
-------
An Ecological Assessment of USEPA Region 8 Streams and Rivers
Data Limitations
Data generated using the EMAP sampling design should not be interpreted to describe the
condition of a particular stream. Data from each site belongs to a larger population of stream length
and cannot be used to fully represent that stream. Data at an individual site may be useful, but more
data would need to be collected on a stream in order to more accurately characterize its condition.
Additionally, comparisons of stressor extent and biological condition between states are not
recommended, since in many cases, states developed both indicators and thresholds independently.
An individual state chapter functions as a statement by that state of the condition and impacts
derived through their own process. The assessments at larger scales that incorporate efforts from
more than one state accept the decisions made in those individual states and do not attempt to
"harmonize" the assessments at lower scales. This must be kept in mind when interpreting the
results from larger scales.
Organization of this Assessment
Each of the following chapters contained in this report represents a different assessment
unit. Whether an individual state or ecoregion, they follow a similar format that is listed below.
Each assessment unit chapter covers in more detail issues such as indicator development, threshold
setting, a description of the biological condition, and a discussion of major stressors. Each unit had
different indicators and reference sites, therefore, the condition assessment is unique to that unit
and comparing one unit to another is difficult and not recommended (e.g. 50% in least disturbed
condition in the mountains is very different from 50% in least disturbed condition in the plains).
Each assessment unit chapter generally contains the following organization (although some
chapters may vary somewhat from this format):
• General description of each assessment unit.
• Extent of resource (total length of perennial streams and assessed stream length).
• Reference site determination (how least- and most-disturbed sites were chosen for a given area).
• Indicators and stressors (development of indicators specific to this assessment unit).
• Setting expectations (threshold-setting for each ecological indicator and stressor).
• Biological condition using various indicators.
• Examination of stressors by stream length.
• Relative risk of stressors to each biological indicator, where possible.
• Conclusions for that assessment unit.
17
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of Colorado
Physical Setting
The State of Colorado covers 267,346 square kilometers and is home to approximately
4,722,460 people (U.S. Census Bureau 2005). The State serves as the headwaters of four major
rivers including the Platte, Arkansas, Colorado, and Rio Grande. Within its boundaries are six
Level III Ecoregions (Omernik 1987), which for the purpose of this study have been merged to
create three bioregions (Figure 1): Plains (Western High Plains, Southwestern Tablelands
Ecoregions), Mountains (Southern Rockies Ecoregion), and Xeric (Wyoming Basin, Colorado
Plateau, and Arizona/ New Mexico Plateau Ecoregions).
Figure 1. Colorado bioregions and major rivers.
V'.
' 3-.
Features
Major Rivers
Xeric Bioregion |1
Mountain Bioregion^
Plaint BioregionlJ
Bioregions
The Plains Bioregion in eastern Colorado is the largest bioregion in the State, covering
113,380 square kilometers (42%). Elevation of the Plains is the lowest in the State and includes the
lowest point, 3,350 feet (1020 meters) above sea level (WRCC), where the Arkansas River crosses
the border into Kansas. The Plains bioregion is characterized by prairie grasslands, tablelands, and
croplands, which are broken by occasional hills, bluffs, and small canyons. With a growing season
of 140-160 days, numerous crops such as wheat, corn, alfalfa, spring grains, and sugar beets can be
easily grown. Although the majority of the Plains bioregion is agricultural land, eighty-six percent
of the State's population resides in this region. Eighty-three percent is concentrated along the Front
Range of the Rocky Mountains in highly developed residential and commercial tracts.
18
-------
An Assessment of USEPA Region 8 Streams and Rivers
Although the Plains bioregion accounts for the largest land area in the State, the Mountains
bioregion accounts for a nearly equal portion at 96,928 square kilometers (36%). The mountains
bioregion has its boundaries at the eastern and western edges of the Rocky Mountains, which are
oriented vertically across the State, just west of center. The mountains exhibit features such as
alpine cirques and tams, glaciers/glacial moraines, broad U-shaped valleys/parks, and glacial
outwash plains at lower elevations. This bioregion boasts the State's highest elevations, with fifty-
four mountains exceeding 14,000 feet (4,267 meters) above sea level, greatly contributing to a state
elevation average of 6,800 feet (2,073 meters), the highest in the nation. Land cover in the
Mountains bioregion consists primarily of pinyon-juniper, spruce fir, ponderosa pine, aspen,
lodgepole pine, and Douglas fir forests, with localized areas of open parks and alpine tundra above
treeline (10,500-12,000 feet or 3,200-3,660 meters). The majority of the State's 91,427 square
kilometers of forest (CDNR 2002) fall within this bioregion.
The Xeric Bioregion covers the remaining 59,290 square kilometers of the State along the
western border. It is characterized by high mesas, buttes, and canyonlands that are typical of the
Colorado Plateau, the dominant feature of the bioregion. The elevation ranges from approximately
4,300 to 12,100 feet (1,310-3,688 meters) above sea level. Land cover in the bioregion is quite
variable and includes large portions of forests, grasslands, irrigated croplands, rangelands, and
shrublands. Fruit production is also possible in the valleys of west-central Colorado as warm, moist
air from the Pacific Ocean provides the specific climate that is suitable for these types of crops. The
Xeric also contains the San Luis Valley, which, with the addition of the State's first agricultural
ditch in 1852, became a productive area of irrigated cropland (Colorado Data Book 2005). The
overall landcover for the State of Colorado is presented in Figure 2.
Climate
The climate in Colorado is classified as a continental highland climate, characterized by
highly variable local temperatures, abundant sunlight, and a moderate wind environment. The
mountains are typically cool year-round, while the plains can have very warm summer days with
initially high temperatures abated by afternoon thunderstorms. High-elevation ranges normally
collect around 400 inches (1010 cm) of snowfall per year, but can receive in excess of 500 inches
(1270 cm) annually (National Climatic Data Center 2006). The accumulated mountain snowpack
generally melts during the spring and summer months, becoming the primary source of Colorado's
water supply. While the mountains typically receive the greatest amounts of precipitation during
the winter months, nearly 80 percent of annual moisture on the plains falls within the growing
season from April to September (WRCC). Areas near the Front Range of the Rocky Mountains are
typically dry and cool with winter temperatures that can occasionally increase rapidly by 25 to 35
°F (14 to 19 °C) due to warm westerly downslope winds known locally as Chinook winds.
19
-------
An Assessment of USEPA Region 8 Streams and Rivers
COLORADO
Shrubland
| Grassland
_ j Cropland
Wtetland
Water
Urban
Mlometers
Forest
figure 2. Land cover of the State of Colorado.
Human Influence
Population
Colorado's population totaled 4,722,460 in 2005, an increase of 9 percent from 2000
(Colorado Data Book 2005). The current State growth rate of 1.8 percent per year is nearly double
the national average (Colorado Data Book 2005), and promises to place ever-growing pressure on
the State's water resources and environment.
Economics
Historically, Colorado has been a productive area for mineral extraction. Agriculture's
contribution to the State GDP has declined, but it still remains an integral part of the economy,
controlling a large portion of private lands. Livestock has overtaken crops as the largest revenue-
producing commodity in Colorado agriculture. Colorado's present economy is grounded in high-
tech and skilled sectors, as well as a robust real-estate and construction market. Tourism has been
an increasing contributor to the revenue of the State (Longwoods International 2003).
20
-------
An Assessment of USEPA Region 8 Streams and Rivers
Impacts to Streams
In Colorado, human activity has the largest impact on stream quality through point and non-
point source discharges, agriculture and silviculture, urban and road runoff, as well as mining and
resource extraction. However, natural biogeochemical, climatological, and hydrological processes
can also amplify anthropogenic impacts to water quality degradation.
Human degradation of streams affects nearly all physical and chemical characteristics of
streams, directly or indirectly. Chemical quality of streams is affected by mining activity, which
contributes heavy metals that are toxic to aquatic life. Naturally occurring elements are exposed in
mine tailings, and the chemicals used to extract ores leach into streams causing unsafe metals
concentrations and low pH conditions. Pesticides, herbicides, nutrients, and pathogens found in
agricultural runoff affect metabolic rates within streams as well as aquatic life health. Chemical
quality is also affected by municipal wastewater facilities and rural septic systems that contribute
ammonia, organic matter, and bacteria to streams. Dam releases change stream chemistry by
influencing dissolved oxygen levels, turbidity, temperature, and chemical composition.
Physical characteristics of streams are also heavily influenced by human activity. Flow
management, channelization, diversions, and impoundments alter natural hydrographs, bed
composition, as well as floodplain inundation extent and duration. Logging activities increase
sediment loads in streams by reducing soil stability in the watershed and also increase the volume
of runoff. Construction and development of riparian areas also affect bank stability, canopy density,
and channel morphology.
Natural processes and climatological events have the potential to amplify stream
degradation. High levels of precipitation deliver chemicals, nutrients, and sediment into streams
through overland and subsurface runoff. Erosional processes can expose naturally occurring
geologic element such as selenium, which is a constituent of local shale. Wildfires cause high
sedimentation rates due to vegetative reduction.
Extent of Streams
A total of 125 sites were sampled in Colorado (71 probability sites and 54 "hand-picked" as
potential reference sites). Sixty-seven probability sites were used in the final assessment.
Approximately 37,265 (+/- 8,446) kilometers of perennial streams are contained within the State
according to the EMAP-West evaluation; the 67 sites used for assessment represent 30,827 (+/-
5,116) kilometers. About 11,681 km of stream were non-target (either dry or found to contain
impoundments). Seventeen sites, representing about 6,438 km, were denied access by landowners.
Sites sampled in Colorado are represented in Figure 3. The extent of stream length by bioregion is
depicted in Figure 4, highlighting the large extent in the mountains.
21
-------
An Assessment of USEPA Region 3 Streams and /Rivers
COLORADO
••
• •
V,
• PROBABILITY SITES
• HAND-PICKED SITES
' ] XERIC REGION
Q J PLAINS REGION
¦ MOUNTAIN REGION
100
200
figure 3. Sampled sites in Colorado (black dots represent probability sites and blue dots represent
hand-picked sites).
Mountains
Stream Length by Bioregion
Bioregioi
Plains
¦¦¦2070
21973
Xerics
8/H4
.
5000 10000 15000
20000
Length (Km)
Figure 4. Colorado stream length assessed by bioregion.
Data Sources
Colorado's EDAS database (Ecological Data Application System) contains extensive
macroinvertebrate and water chemistry data from CDPHE's (Colorado Department of Public
22
-------
An Assessment of USEPA Region 8 Streams and Rivers
Health and the Environment) monitoring program. However, due to spatial and temporal gaps
within data, additional macroinvertebrate and chemistry datasets were compiled to achieve a robust
dataset upon which to base the development of the Macroinvertebrate Multi-metric Index (MMI)
and O/E predictive model for this study. Chemistry data from the national STORET (Storage and
Retrieval database, USEPA) database was used to supplement data for sites where
macroinvertebrate data was collected, but corresponding chemistry data was unavailable. To
eliminate spatial gaps in surveyed sites, additional macroinvertebrate and chemistry data was
drawn from high quality datasets where similar sampling methods were employed. These datasets
included chemical, biological, and physical habitat data from the USEPA's WEMAP (Western
Ecological Monitoring and Assessment Program) and Southern Rockies REMAP (Regional
Ecological Monitoring and Assessment Program), USU-STAR (Utah State University, Science to
Achieve Results Program), and NAWQA—USGS (National Water Quality Assessment
Program—United States Geological Survey). This merger of data allowed the inclusion of 717
sites statewide from which the Macroinvertebrate MMI and O/E model would be developed.
To compare macroinvertebrate data from datasets of varying taxonomic resolution, an
operational taxonomic unit (OTU) system was utilized. This system assigns a standardized
numeric code to each taxonomic level associated with specific macroinvertebrates. By examining
these designations, the highest taxonomic level that is exhibited by all sites can then be selected,
allowing direct comparison of all sites from all datasets compiled for this study. In order to be
compatible with CDPHE data, non-CDPHE samples were also sub-sampled to a 300-organism
count. While some taxonomic resolution was sacrificed, mainly within the CDPHE data, the use of
the combined dataset led to a more accurate and powerful tool for index and model development.
The data utilized in the Fish Index of Biotic Integrity (IBI) development was collected at 91
sites throughout Colorado during the WEMAP project. Periphyton MMI development data was
also from the WEMAP project and used information from 69 reference sites in Colorado, Utah,
and Wyoming.
Reference Site Determination
In this study, an a priori approach was used in site classification and establishment of
reference condition. These sites represent natural (reference) and impacted (stressed) conditions in
each bioregion and were designated based on physical and chemical conditions. A priori sites are
the foundation for the development and calibration of the Fish IB I, the Macroinvertebrate and
Periphyton MMIs, and the Macroinvertebrate multivariate predictive model (O/E model). Metrics
to be included in the IBI and MMIs were chosen based on the level of discrimination efficiency
they exhibit between reference and stressed sites. In the O/E model, reference sites were used to
determine the number of expected taxa at each site, which is then used as part of a ratio to generate
a unit-less score associated with taxa loss. Reference sites were then used to generate thresholds
for scores from the Macroinvertebrate and Periphyton MMIs, the Macroinvertebrate O/E model, as
well as the fish IB Is (see Threshold Determination below).
A priori reference site designation for the Macroinvertebrate MMI and O/E model was
conducted by their respective developers, Tetra Tech, Inc. and Chuck Hawkins of Utah State
University. These researchers used standards in Colorado's Basic Water Quality Standards;
23
-------
An Assessment of USEPA Region 8 Streams and Rivers
screening criteria from USEPA's Office of Research and Development (ORD); water quality
standards and EMAP selection criteria from Wyoming and Montana; as well as best professional
judgment to establish a set of selection criteria for designating a priori classification. The
subsequent criteria utilized varying levels of parameter stringency for each bioregion to allow for
comparisons between sites in adjacent bioregions where natural conditions can be dramatically
different. The criteria were then applied to water chemistry, land cover/land use, and physical
habitat data from the Plains, Mountains, and Xeric bioregions to produce the final a priori
classifications for the macroinvertebrate tools.
The EMAP and STAR site designation process was based on an inclusion by exclusion
selection design. This process was aimed not at distinguishing reference sites, but rather excluded
sites exhibiting characteristics associated with stress. Alternatively, CDPHE sites that passed four
parameter criteria thresholds without a failure were designated Reference, while sites that failed
four or more parameters were designated as Stressed. CDPHE sites from the reference list were
then reviewed by CDPHE staff with detailed knowledge of the candidate reference sites to
determine whether characteristics of a site that were not apparent in the data should exclude a site
from reference designation.
Colorado's Fish IBI was developed by researchers from the CDOW (Colorado Division of
Wildlife), CDPHE, CWN (Colorado Watershed Network), and the USEPA and followed a separate
reference site designation process. These agency scientists used chemical and physical screening
criterion, developed by John Stoddard and Alan Herlihy at the EPA's ORD (Stoddard et al 2005a),
as a guideline for reference site designation. Reference sites were selected if they met the ORD
criteria and were then individually examined by those who possessed specific knowledge of the
sites. Characteristics not apparent within the dataset were accounted for by refining site
designations using best professional judgment during three workgroup meetings in July 2005 and
April and May of 2006.
Colorado's Periphyton MMI utilized a priori designations from the EPA's ORD
(RT_Final) for index calibration while its test set relied on designations developed in Colorado for
the Fish IBI (RT_Mod). Variation between these two designation lists was low for sites within
Colorado and allowed sites outside of the State that had ORD designations to be used. External site
inclusion strengthened the index by bolstering the number of reference sites used in the
development of the Periphyton MMI.
Bioassessment Tool Development
Periphyton MMI Development
Colorado's periphyton index was developed by scientists from USGS, USEPA, and
CDPHE. Index development utilized over 250 diatom metrics from five categories, applied to data
from regions in Utah, Wyoming, and Colorado. External validation of bioregionally specific
periphyton indices was accomplished by utilizing separate sets of calibration and test data (Table
1). Plains data from Colorado and Wyoming as well as xeric data from Colorado and Utah were
each randomly split in two groups, creating a calibration data set for index development and a test
24
-------
An Assessment of USEPA Region 8 Streams and Rivers
dataset for index validation for each region. For the mountains bioregion, data from Utah and
Wyoming included the calibration dataset, while data from Colorado was used as the test set.
Table 1. Subsets of EMAP data used to develop periphyton indices for Colorado.
Region
Ecoregion
Calibration data
Calibration data
Test data
Test data
Level 3
R sites
T sites
R sites
T sites
Mountain
19,21
20
19
22
22
Plains
25, 26
8
8
5
7
Xeric
13, 20, 22
4
9
4
7
Metric selection was based on each metric's ability to discriminate between reference and
"stressed conditions". This response to stress was discerned by plotting metric values against
corresponding a priori site designations (T sites) (Stoddard et al 2005a). Metrics that passed the
responsiveness screening were then sequentially evaluated based on range, signal to noise ratio, and
independence from other metrics. The remaining pool of potential metrics were then compared to
other metrics in their same category (i.e., morphology, composition) and selected for inclusion
within the index based on their scores in each previous screening test. The resulting indices
incorporated the most responsive metrics from as many categories as possible. The final metrics for
the periphyton index are included in Table 2.
Table 2. Peri
phyton MMI metrics.
Bioregion
Metric
Category
Plains
Cymbella (sensu lato or "old" taxonomic classification)
Richness
Richness
Cymbella (sensu strictu or "new" taxonomic
classification) Percent Taxa
Composition
Van Dam (et al. 1994) Trophic Class 5&6 Number of
Individuals
Tolerance
Van Dam (et al. 1994) Oxygen Class 1 Percent Taxa
Tolerance
Xeric
Navicula (sensu lato or "old" taxonomic classification)
Richness
Richness
Cymbella/(Cymbella+Navicula) (sensu strictu or "new"
taxonomic classification) Percent Taxa
Composition
Bahls (2004) Mod. & Highly Motile Number of
Individuals
Morphology
Van Dam (et al. 1994) Trophic Class 5&6 Richness
Tolerance
Mountains
Navicula (sensu strictu or "new" taxonomic
classification) Richness
Richness
Achnanthes (sensu lato or "old" taxonomic
classification) Percent of Individuals
Composition
Bahls (2004) Moderately & Highly Motile Number of
Individuals
Morphology
Van Dam (et al. 1994) Trophic Class 1&2 Percent Taxa
Tolerance
25
-------
An Assessment of USEPA Region 8 Streams and Rivers
Macroinvertebrate MMI
Multimetric indexes (MMI or IBI) allow multiple biological measurements, or metrics, to
be combined into a single, unitless index value. Metrics are attributes of the biological assemblage,
which can be quantified as a response to human and natural alteration or stress of the environment.
MMIs are calibrated using reference conditions and are created to exhibit a site's correlation to
these conditions based on multiple categories (metrics). By incorporating metrics such as richness,
composition, functional feeding group, and pollutant tolerance for benthic macroinvertebrate
communities, MMIs can accurately indicate macroinvertebrate community health and aide in
stream condition determination statewide. Tetra Tech, Inc. developed Colorado's Macroinvertebrate
MMI as part of a 319 grant project.
Candidate metrics were drawn from five categories: richness, composition, pollution
tolerance, functional feeding group, and habit (locomotion). Selection was based on discrimination
efficiency (DE), low variability, ecological meaningfulness, contribution of representative and
unique information, and sufficient range of values.
In this case, discrimination efficiency is the capacity of biological indicators to detect
stressed conditions. Box plots of inter-quartile ranges of reference and stressed sites display the
indicator's ability to discriminate between reference and stressed conditions. If the boxes do not
overlap, the DE is said to be 75% or greater. The metrics with higher DE values were preferred,
and those less than 25% were excluded from the index. The Coefficient of Variability
(CV=Standard Deviation/ Mean) was calculated for each reference site and, although no numeric
threshold was set, lower CV values were preferred. Metrics selected were also indicative of
expected responses of assemblages to change. The largest number of non-redundant metrics was
used to encompass as many indicators of stress as possible. The metrics included in the
macroinvertebrate MMIs are listed in Table 3.
26
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 3. Macroinvertebrate MMI metrics.
Bioregion
Metric
Category
Plains
Percent Chironomidae
Composition
Percent Burrowers
Habit
Percent Predators
Trophic
EPT Taxa
Richness
Hilsenhoff Biotic Index
Tolerance
Xeric
Percent Coleoptera
Composition
Diptera Taxa
Richness
Percent Dominant Taxon
Tolerance
Percent Climbers
Habit
Predator Taxa
Trophic
Mountains
Percent Climbers
Habit
Total Taxa
Richness
Percent Oligochaete
Composition
Percent Trichoptera which are Hydrops ychidae
Tolerance
O/E Development
RIVPACS (River Invertebrate Prediction and Classification System) (Moss et al 1987,
Wright 1995) assessments determine biological condition or quality by estimating the taxonomic
completeness of a standard sample. Taxonomic completeness is a fundamental aspect of biological
integrity and is defined here as the proportion of taxa that occur over those that are expected in a
single sample. The O/E model describes which taxon are predicted to naturally occur at a site (E,
expected) versus which taxon were actually collected by sampling the site (O, observed), where E
is the sum of the probabilities of capture for each taxa. Individual probabilities of capture are
derived from regionally classified reference sites, which are grouped by taxonomic similarity.
The O/E model output is a number from 1 (0=E) to 0 (0
-------
An Assessment of USEPA Region 8 Streams and Rivers
Ninety-seven reference (least-disturbed) sites were used for the development of the O/E
model for Colorado. These sites contained 173 OTU's, eighty of which occurred in five or more
samples and were used to biologically classify sites for the model. Sites were well-distributed
geographically throughout the State with the exception of a cluster along the western base of the
Southern Rocky Mountains. These sites were selected as adequate representation of natural
conditions due to low chemical contamination, low flow alteration, and natural riparian and habitat
conditions. Sites were then classified based on their taxonomic similarities.
Sites were divided into as many classes as were feasible in order to maximize similarity,
with the requirement that each class contain no fewer than five sites. Classification of sites allowed
for the estimation of frequencies of taxon occurrence in each site class and the development of a
discriminate function model from taxonomic predictor variables that allowed the prediction of
reference site classification probability for new sites. John Van Sickle's (USEPA) all subsets
software was utilized to evaluate 32,767 discriminate models in order to determine which metric
combination maximized precision and minimized bias for each predictor variable.
Performance measures were based on internal validation and included the mean, standard
deviation, and root mean square error of O/E. Predictor variables that could be influenced by
humans were eliminated, and only map-derived variables were utilized to illustrate the influence of
local factors on spatial and temporal distribution of the biota. The final three predictor variables
were: longitude (decimal degrees), mean annual air temperature (°C x 10), and log watershed area
(km2) (see Table 4). A strong relationship between temperature and biotic classes implies that
thermal variation across Colorado is the single most important factor affecting the distribution of
stream taxa (Tetra Tech, Inc. 2005).
Table 4. O/E model predictor variables.
Predictor Variables
Longitude (Decimal Degrees)
Mean annual air temperature (°C x 10)
log watershed area (km2)
O/E score calculations are based on a probability of capture threshold of >0.5. Ideally, the
greatest number of taxa is used to develop a model, but this threshold is used as it minimizes
predictive error based on the presence of rare taxa. It should be noted that utilizing this capture
threshold decreases taxonomic resolution and may mask specific species' sensitivity to stress.
Fish IBI Development
Representatives of CDPHE, USEPA, CDOW, and CWN held a series of workshops in the
fall 2005 and spring of 2006 to create a fish IBI for Colorado, A list of 761 metrics was compiled
from species counts collected at each Colorado site sampled during the western EMAP study. An
inter-quartile box plot was created for each metric to discern the discrimination efficiency (DE)
between least- and most-disturbed sites. Those metrics that exhibited a DE of greater than seventy-
five percent (boxes did not overlap) between reference and stressed sites were retained for further
evaluation. A Pearson's correlation was conducted on the remaining metrics and redundant metrics
were removed. In order to garner a comprehensive index, the metrics were then categorized based
28
-------
An Assessment of USEPA Region 8 Streams and Rivers
on reproductive and feeding habits, habitat preference, stress tolerance, and taxonomic
classification to ensure inclusion of each facet of the biological community that was potentially
responsive of disturbance.
This process resulted in the creation of an IBI for both the Xeric and the Plains bioregions
(Table 5). An index for the Mountains bioregion failed to be developed as metrics were unable to
discriminate between reference and stressed sites.
Table 5. Fish IBI metrics.
Bioregion
Metric
Plains Bioregion
Number of nonnative individuals
Percent of species that native herbivores
Percent of hider individuals
Percent of native species that are long-lived and tolerant to sediment
Percent of native individuals that prefer warm-water habitats
Number of individuals that are benthic and tolerant to sediment
Xeric Bioregion
Number of individuals of intermediate tolerance to nutrients and
prefer cool water habitat
Percent of hider individuals
Percent of long-lived species with intermediate tolerance to sediment
Percent of species that are lithophilic
Stressors
Examination of ecological stressors is critical when assessing the biotic health of surface
water due to their direct impacts on the biota living in the stream. Water quality and physical
habitat characteristics (Table 6) were analyzed and recorded as part of this project in order to
determine which stressors were most influential as they pertained to macroiqvertebrate, periphyton,
and fish health in Colorado. Understanding which parameters are influencing stream health allows
management and regulatory practices to be developed or altered in order to minimize future
impacts and mitigate degraded conditions due to specific stressors of streams.
29
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 6. Stressor
parameters of Colorado EMAP study.
Type
Stressor
Data Code
Chemical
Total Phosphorus (pg/L)
PTL
Total Nitrogen (ng/L)
NTL
Chloride (neq/L)
CL
Sulfate (|^eq/L)
S04
Closed Headspace pH
PHSTVL
Physical
Habitat
Mean Bank Canopy Density (%)
XCDENBK
Riparian Disturbance—Sum of All Types
(Proximity Weighted Presence)
W1 HALL
Turbidity (NTU)
TURB
LoglO[Relative Bed Stability]
LRBS BW5
Substrate Fines—Silt/Clay/Muck (%)
PCT_FN
Water chemistry and physical habitat are of great importance in bioassessment studies
because they determine habitat quality and influence biological processes in streams. Phosphorous
and nitrogen are influential nutrients in a stream that effect primary production rates and overall
stream metabolism. Agricultural runoff, waste-water treatment facility effluent, and allochthonous
organic matter are primary point and non-point sources of N and P.
Riparian disturbance is a qualitative measure that indicates levels of human and non-human
impact on the land area directly adjacent to the stream. Canopy density is important due to its effect
on in-stream temperature, sunlight penetrance, as well as its contribution of litterfall (organic
matter) into streams. Relative bed stability describes the substrate of the stream and its mobility,
which is determined by substrate composition and flow characteristics at a site. This parameter,
along with percent fines, details benthic micro-habitat in a stream as well as sediment availability
for microbial colonization as part of hyporheic metabolism.
Threshold Determination
In order to classify streams based on level of disturbance, thresholds were set for each
biologic indicator and ecological stressor. Biological Indicator thresholds were established using
two sets of percentiles, both using land cover weights calculated in Statistica 7.0. The 25th and 5
percentiles of reference site scores were used for the Fish IB I thresholds, while the 25 th percentile
of reference site scores and the mean of the remaining scores were used for the Macroinvertebrate
MMI and O/E model as well as the Periphyton MMI.
Land cover was based off of a GIS layer of Land Cover Data that was developed for the
Colorado Gap Analysis Project. A one kilometer radius buffer was drawn around each site and
percentage of each land cover type was calculated and classified as natural or disturbed. This
weighting allowed sites' biological indicator scores to be compared without a bias resultant from
varying degrees of land cover disturbance. This technique was applied in all four bioassessment
tool threshold development procedures. However, land cover weighting was not used when
determining the moderately/most-disturbed threshold for the macroinvertebrate MMI. Cover types
can be seen by type and bioregion in Figure 5.
30
-------
An Assessment of USEPA Region 8 Streams and Rivers
Plains Landcover
9%
5vT
~ Grassland
\
~ Row Crops
¦ B ^
¦ Small Grains
~ Fallow
6%L-^"
J
jr 69%
~ Other
Xerics Landcover
6v\ \
¦ Evergreen Forest
~ Shrubland
16% I
~ Grassland
J
~ Pasture/Hay
V W
~ Other
47%
Mountains Land Cover
6%
16%
19%/\
~ Deciduous Forest
¦ Evergreen Forest
~ Shrubland
~ Grassland
14%
45%
~ Other
Figure 5. Bioregional land cover.
Fish IB I thresholds were set using the 25lh (least-/moderately-disturbed boundary) and 5,h
(moderately-/most-disturbed boundary) percentiles of reference site scores. These percentiles have
been used as thresholds in past bioassessment studies by the EPA (i.e., Western EMAP (Stoddard et
al 2005b) and the Southern Rockies Assessment (U.S. EPA 2006b)). As development of a Fish IBI
for the mountains bioregion was unsuccessful, thresholds were set for both the Xeric and Plains
bioregions. Since only four reference sites existed in the Colorado Xeric bioregion; Xeric EMAP
reference sites from Utah and Wyoming were utilized to solidify the threshold determination within
31
-------
An Assessment of USEPA Region 8 Streams and Rivers
the region. Site additions were beneficial, as threshold (25th percentile score) accuracy increases
when more reference sites are used in threshold determination. The thresholds shown in Table 7
were based on a total of thirteen Plains reference sites. Neither the plains, nor the xeric bioregion
had normally distributed Fish IBI scores, with natural breaks occurring at the moderately-/most-
disturbed threshold. This distribution aligned with the established thresholds, which contributed to
the confidence placed in our tools, although relatively few reference sites were utilized.
Table 7. Disturbance class thresholds.
Index
Least-Moderate
Moderate-Most
MMI
55.76
43.02
OE
0.69
0.57
IBI_X
52.21
41.56
IBI-P
66.76
28.79
Periphyton
51.10
25.00
The Macroinvertebrate MMI and O/E as well as the Periphyton MMI thresholds were set
utilizing the 25th percentile of reference sites and the mean of all sites below the 25th percentile of
reference sites. The scores for each site were weighted for percentage of disturbed land cover
within a 1km radius around the site. These percentile based threshold values were calculated to
differentiate least- and moderately-disturbed sites as well as moderately- and most-disturbed sites.
MMI and O/E thresholds were set using reference sites from across the entire State with all
bioregions combined into one set of scores. This allowed designations to be based on a robust set of
24 reference sites statewide.
Stressor thresholds were defined by Stoddard and Herlihy of the USEPA's ORD (Stoddard
et al 2005a). These were initially designed as reference site screening thresholds for the ten
ecological regions of the West (USEPA Level III Ecoregions) and were comprised of chemical and
physical habitat parameters (Table 8).
32
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 8. Physical and chemical stressor thresholds.
Colorado EMAP Sites
Chemical/Physical Habitat Parameter
P total
N total
CI
so4
PH
Turbidity
Riparian
Disturbance
Fines
(%)
Relative
Bed
Stability
Bank Canopy
Density
Hg/L
Pg/L
|jeq/L
Heq/L
NTUs
Ecoregion
Threshold
S. Rockies
Least-Disturbed
<25
<750
<200
<200
<9
No Std*
<1.0
<15%
>-2.0
>50%
S. Rockies
Most-Disturbed
>100
>1000
>1000
>1000
<6,>9
>10
>3.0
>50%
<-3.0
<10%
N. Plains
Least-Disturbed
<150
<2000
<1000
No Std*
<9
<50
<2.0
<90%
>-3.5
>25%
N. Plains
Most-Disturbed
>500
>4000
>2750
No Std*
<6,>9
>100
>3.0
>99%
No Std*
<5%
Xeric
Least-Disturbed
<50
<1500
<1000
<10000
<9
<25
<1.5
<50%
>-2.0
>50%
Xeric
Most-Disturbed
>150
>4000
>2500
>15000
<6,>9
>50
>3.0
>90%
<-2.8
<10%
* No disturbance category standard was developed for these parameters; therefore, stressor extent and relative risk calculations
did not include data from these instances. Calculations relied on values derived from the available standards for each parameter
within each bioregion.
33
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
Following the development of Colorado's MMI, IBI, and O/E model, generation of scores,
and subsequent determination of thresholds, a final statewide output was compiled. Biological
condition was reported for only those sites that fell within the probability design of the EMAP
Study. Of the 250 sites used to develop the Periphyton MMI, the 717 sites of the Macroinvertebrate
MMI and O/E model, and the 91 sites the Fish IBI, only 67 were reportable, target, probability
sites. These sites met the requirements of the study design and could be reported on as part of the
EMAP project. Each of the 67 sites represented a given number of river miles, determined by the
site's location within the watershed and stream type. River length was then totaled for sites
representing each disturbance class for all bioassessment tools (Table 9, Figure 6).
Table 9. Biological condition.
Index
Stream Length (Km)
Disturbance Class
Macroinvertebrate
MMI
26456.68 [85.82%1
Least-Disturbed
2013.92 [6.53%]
Moderately-Disturbed
2356.12 [7.64%]
Most-Disturbed
Macroinvertebrate
O/E
24871.13 [80.68%]
Least-Disturbed
2821.19 T9.15%]
Moderately-Disturbed
3134.4 riO.17%]
Most-Disturbed
Fish IBI
3178.5 [10.31%]
Least-Disturbed
2348.71 [7.62%]
Moderately-Disturbed
2213.46 [7.18%]
Most-Disturbed
23086.04 [74.89%]
No Index
Periphyton MMI
12424.22 [40.30%]
Least-Disturbed
12797.67 [41.51%]
Moderately-Disturbed
4867.94 ri5.79%]
Most-Disturbed
736.89 [2.39%]
No Data
Although repeated sampling is needed for a comprehensive assessment of a site, the tools
developed in this study give scientists a better understanding of biologic communities at a given
time and place. In general, biotic condition throughout the State is quite good, with well distributed
sites with little overall impairment. There were groupings of degraded sites where the South Platte
flows out of the Denver metro area, along the lower Arkansas in southeastern Colorado, as well as
on the Colorado River near the Utah border. This is most likely due to the high demand placed on
steams as they pass through highly developed locations with extensive land cover degradation and
flow control. Industrial and domestic discharges can account for 100 percent of flows in the South
Platte at times of high demand, resulting in altered water chemistry, temperature, and flow regimes
in these reaches. When this is coupled with diversions for agriculture and water supply storage,
stress on the biota of the stream can lead to altered macroinvertebrate and fish communities.
33
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
T^8%
10%
75%
5000 10000 15000 20000
Stream Length (km)
25000
30000
35000
Figure 6. Macroinvertebrate, fish and periphyton condition.
The Mountains bioregion is generally an area of lower pollution and land cover degradation
due to limited agricultural land use and sparse residential and commercial development. These low
disturbance conditions in the mountains may be the result of widespread publicly owned lands and
areas of high forest density where human perturbation is reduced due to restrictions placed on use
of public lands. Although human induced disturbance is low, ambient levels of pollutants or
compounds from abandoned mining sites or natural sources continue to pose risks to aquatic
organisms. Human disturbance increases as streams flow out of headwater areas into the Plains and
Xerics. Increased population density at lower elevations leads to increases in agricultural runoff;
diversions and dams; residential and commercial development; and industrial and municipal
discharges. These compounding factors degrade water quality and reduce overall biotic condition at
sites in downstream bioregions. The impact of increased degradation at lower elevations was
reflected in each of the bioassessment tools developed in the study.
Fish IBI scores were generally lower than scores generated by the Periphyton MM1 and
Macroinvertebrate MMI and O/E model. The lack of a Fish IBI in mountains may have lowered the
mean index score of the Fish IBI statewide. Macroinvertebrate and periphyton assessment tools
showed that fewer sites of the most-disturbed condition category were seen in the Mountains
bioregion than were seen in either of the State's other bioregions. Without these potential positive
scores weighting the overall output, scores from the Fish IBI tended to be lower than their
periphyton or macroinvertebrate counterparts.
34
-------
An Assessment of USEPA Region 8 Streams and Rivers
As more data becomes available through monitoring by CDPHE, these bioassessment tools
should be recalibrated with additional reference sites to decrease the standard deviation of the
thresholds and to ensure that the metrics currently comprising the indexes are the most informative
of biological condition. Many factors contribute to degradation in streams (see Impacts to Streams),
but it is important to understand which parameters are of the greatest importance to stream biota in
order to mitigate degradation and develop management and regulatory practices that protect
designated uses and aquatic life. By re-examining metrics and thresholds as more data is collected
throughout the State, more accurate output will be generated by these tools, producing an increased
efficiency in biological condition assessment in Colorado.
Stressor Extent
Stressors were ranked using the screening criteria developed by the USEPA's ORD's
Stoddard and Herlihy (Stoddard et al 2005a). These criteria were then applied to the 67 probability
sites, and associated stream length representations were totaled (Table 10). Stressors were then
ranked based on the proportion of stream length that fell in the most-disturbed class to Colorado's
stressor conditions. Turbidity, total phosphorous, and sulfate had nearly equal lengths of stream
classified as most-disturbed, indicating that these parameters are the most widespread stressors in
the State. It should be noted that a threshold was not designated for least-disturbed turbidity levels
in the Mountains and for least- and most-disturbed sulfate levels in the Plains bioregion.
Table 10. Extent of stressors throughout Colorado.
Colorado EMAP Sites
Chemical/Physical Habitat Parameter
Chemical/Physical Habitat
P
N
CL
S04
pH
Turbidity
NTUs
Riparian
Disturbance
Fines
%
Relative
Bed
Stability
Canopy
Density
Stressor Extent
Mg/L
Mg/L
(jeq/L
fteq/L
Disturbance Rank
(Most to Least)
2
5
4
3
10
1
7
6
9
8
Reach
Length
(Km)
Least-
Disturbed
24196
29100
27079
20132
30827
7053
20373
22390
25450
21045
Mod-
Disturbed
5109
807
1605
7224
1077
6984
4443
1021
6331
Most-
Disturbed
1521
919
942
1401
1524
376
901
300
357
NoStd
2070
21173
105
No Data
1201
3094
3094
3951
3094
Total Length (km)
30827
30827
30827
30827
30827
30827
30827
30827
30827
30827
Disturbed
Length %
Least-
Disturbed
78%
94%
88%
65%
100%
23%
66%
73%
83%
68%
Mod-
Disturbed
17%
3%
5%
23%
3%
23%
14%
3%
21%
Most-
Disturbed
5%
3%
3%
5%
5%
1%
3%
1%
1%
No Std
applied
7%
69%
No Data
4%
10%
10%
13%
10%
Two additional biological stressors were measured in this study, but not presented in Table
10. These were the presence of alien vertebrates (mainly fish) and invasive plants. The EMAP-
West Report (Stoddard et al 2005a) derived thresholds for non-native vertebrates, which were: if
more than 10% of the vertebrate individuals captured at a site were non-native they were listed as
35
-------
An Assessment of USEPA Region 8 Streams and Rivers
common, more than 0% but less than 10% was considered "present" and if none were found they
were absent. In Colorado, alien fish were common in 20,504 km of stream length, present in 1,774
km, and absent in 3,745 km.
Additionally, twelve invasive plants were also noted for presence throughout the full
EMAP-West study area. Of those 12, common ones found in Colorado were common burdock
(Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus nutans), Canada thistle
(Cirsium arvense), common teasel (Dipsacus fullonum), Russian olive (Elaeagnus angustifolia),
leafy spurge (Euphorbia esula), salt cedar (Tamarix sp.) and reed canary grass (Phalaris
arundinacea). These were either common (found at 10-50% of transects) or dominant (found in
more than 50% of transects) in about 34% of stream length where sampled and absent in 62%.
Invasive plants were assessed in 27,733 stream kilometers (out of the total of 30,827).
Also not presented in Table 10 is an assessment of condition using concentrations of
mercury in fish tissue. This indicator used whole fish of various species and sizes, so does not
directly correlate with human health issues, but is meant as an ecological indicator. The threshold
used to determine if impacts to wildlife was set at levels >0.1 |ig/g (Lazorchak et al 2003). Fish
with values above this level were found in 5,300 km of stream length, lower than this level in
16,972 km. About 8,950 km of stream length were not assessed using fish tissue mercury.
Discussion
Streams statewide were found to be in good condition, with only three groups of localized
degradation and otherwise randomly distributed sites of the most-disturbed condition. Scores
between the MMIs, IB I, and O/E tools exhibited poor correlation, which further emphasizes the
need for continued recalibration of these tools to ensure accuracy. Six percent of sites were
designated in the same disturbance class by all four indicator tools and twenty-one percent of sites
showed agreement between three tools. These percentages were higher when only the
Macroinvertebrate IBI and O/E tools were examined, exhibiting sixty-two percent agreement.
The lack of bioassessment tool agreement may prove to be a benefit of using unique metrics
for each bioregional index and using separate biological communities as indicators of stream
condition. It is possible that this method allows for the resolution of assessment to be much higher
as specific components of each community in each region can be inferred. The varied response of
different biologic communities to conditions and stress at a single site may provide some novel
insight to preferences and tolerances of the given community (Hawkins, Personal Communication
2007).
The stressors turbidity, total phosphorous, and sulfate have the greatest extent in Colorado,
thus making them more likely to have the greatest impact on stream biota. As part of further tool
refinement by CDPHE, inclusion of additional index metrics should be considered. Currently,
metrics focus on composition and richness of biological communities, which may mask presence of
rare species. This presence has been intentionally deleted in an effort to increase taxa prediction
accuracy by using a capture threshold (<0.5) in the O/E model and perhaps unintentionally by
subsampling data used in the MMI and IBI tools. While this increases predictive capability and
allows for inclusion of information from data sets of varying resolution, it ignores pertinent
36
-------
An Assessment of USEPA Region 8 Streams and Rivers
information available within the current data set by disregarding the presence of highly specialized
and sensitive species.
Processes leading to reference site determination should be examined as more candidate
sites become available through continued monitoring. Incorporation of best professional judgment
within this study may have led to erroneous o priori site classifications, namely within the Fish IBI
development, on which these bioassessment tools were based. Consistent values such as table value
standards should be utilized to eliminate inconsistencies incurred through judgment decisions
during reference site determinations. This could potentially allow for new metric compositions
within indexes, which could lead to more accurate scores and better inter-index agreement. More
accurate reference designations would also benefit O/E output as probabilities of capture and
expected (E) values would more accurately reflect reference conditions in streams within each
region.
Continued sampling of streams statewide will contribute greatly to the index and model
framework established within this project. As additional reference (least-disturbed) and stressed
(most-disturbed) sites are added to Colorado's EDAS database, metric discrimination efficiency
and threshold designation can be reevaluated, ensuring the accuracy of scores generated for future
regulatory purposes. Additional reference sites within the Mountains bioregion could lead to the
development of a Fish IBI for this region, filling a gap in the existing IBI and creating a viable
statewide index.
Colorado's EMAP Project resulted in the development of bioassessment tools that will be
immediately useful in monitoring and assessing streams statewide. A data management program
has been developed to assign metric values and generate IBI scores from validated fish data to
supplement the existing MMI (CDPHE's EDAS) and O/E (USU website) data processors. A
periphyton data management tool is also possible, using the template that was developed for the
fish data management program. This set of tools will allow the State to make rapid assessments of
sites and determine general ecological condition based on a single sample with some degree of
confidence. This rapid screening of sites will allow regulators to focus on stream segments where
ecological conditions are poor. Specific parameters can then be researched in detail to provide
information for management alteration as well as permitting and compliance issues. For more
detail on the assessment of Colorado streams see the full Colorado report (CDPHE, 2007).
37
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of Montana
Physical Setting
The State of Montana covers approximately 380,803 square, kilometers. Three
major river basins dominate the landscape of Montana: the Missouri, the Yellowstone,
and the Columbia River basins. Tributaries of the Columbia River, principally the Clark
Fork River and the Kootenai River, flow west of the Continental Divide to the Pacific
Ocean. East of the Continental Divide, the Yellowstone and Missouri Rivers and their
tributaries drain the State's waters toward the Mississippi River and on to the Gulf of
Mexico. Smaller areas of the State are drained by tributaries of the St. Mary River, which
flows northward to Hudson Bay. Parts of 7 Level III Ecoregions (Woods et al 1999) are
located in the State. These are the Northern Rockies (15), Idaho Batholith (16), Middle
Rockies (17), Wyoming Basin (18), Canadian Rockies (41), Northwestern Glaciated
Plains (42), and Northwestern Great Plains (43).
The Northern Rockies Ecoregion (15) varies from high, rugged, glaciated
mountains with dense coniferous forests to low elevation, essentially treeless valleys.
Mountains range from the wet and rugged Cabinet Range to the gentler, drier Salish
Mountains. Valleys are also varied in geomorphology, vegetation, and climate, with the
most striking comparison between the forested Swan Valley with its gravelly soils and
the dry treeless grasslands of the Camas Prairie Basin, with its lacustrine clays. Flathead
Lake, a lake large enough to moderate the climate of the surrounding area, is a prominent
feature of the ecoregion. Precipitation in the Northern Rockies Ecoregion ranges from
100 or more inches (250 cm) in the high mountains to 12 or fewer inches (30 cm) in the
drier, rain shadowed valleys. On a broad scale the climate is influenced by maritime
weather patterns, which are a stronger influence in the north and west than in the east and
south.
The Idaho Batholith Ecoregion (16) is characterized by low alkalinity waters;
granitic rocks underlie the erodable soils. The glacier-gouged canyons and high peaks of
the Bitterroot Range are a prominent feature of the ecoregion; these form the
southwestern border of Montana. The eastern part of die Idaho Batholith Ecoregion is
characterized by forested mountains. Much of the region remains in federally-designated
wilderness.
The Middle Rockies Ecoregion (17) is a diverse mosaic of landscapes that lie both
east and west of the Continental Divide. Rugged, high mountains are treeless in the
higher elevations, and forested on lower slopes. Partly-wooded or shrub-and-grass
covered foothills, and intermountain valleys dominated by grasslands and pastures cover
large areas of the region. The high mountains, particularly the Absaroka, Madison, and
Gallatin ranges are much wetter than low elevation areas. Carbonate rocks throughout the
ecoregion influence water chemistry of the lakes and streams, creating higher alkalinity
waters that are more productive than the waters of granitic regions. A large number and
many kilometers of perennial streams, fed by mountain runoff, flow through the Middle
Rockies Ecoregion. High concentrations of heavy metals contaminate parts of the Clark
38
-------
An Assessment of USEPA Region 8 Streams and Rivers
Fork River in this ecoregion, a legacy of the Anaconda Smelter. Parts of the ecoregion
are isolated mountain areas lying in the midst of the Northwestern Glaciated Plains; these
include the Little Rockies, Sweetgrass Hills, Highwood Mountains and other ranges.
A small part of the Wyoming Basin Ecoregion (18) extends into south'central
Montana. This region is dry, lying in the rain shadow of the Beartooth Plateau to the
west; only a few centimeters of precipitation fall annually. Alkaline soils, arid rolling
plains, and sagebrush steppes characterize the region. Aquatic resources are few, but
include reaches of the Clarks Fork of the Yellowstone River.
To the north, the Canadian Rockies Ecoregion (41) encompasses the high
elevation mountains of Glacier National Park, and the Bob Marshall, Great Bear, and
Scapegoat wilderness areas. West of the Continental Divide, these mountains are
influenced by maritime air masses, and receive heavy precipitation. Portions of the
ecoregion that lie east of the Divide, however, are in the rain shadow of the mountains,
and are influenced by continental weather patterns. Rugged, forested lower slopes and
unforested high alpine country characterize the region. Much remains in wilderness.
Carbonaceous rocks underlie the southern part of the Canadian Rockies Ecoregion both
west of the Continental Divide and on the Front Range to the east, influencing water
quality and aquatic productivity.
The Northwestern Glaciated Plains Ecoregion (42) extends over the northern part
of the State, from the base of the Rocky Mountain Front to the North Dakota state line. In
its western expanse, grassy hills and buttes are dissected by tree-lined streams, and there
is more precipitation than in the areas to the east. Broad, nearly-level, treeless plains
characterize the areas eastward; native vegetation in these areas were short-stemmed
grasses. Today, this is an important cereal crop production area. Dissected, rolling plains
farther east are drier, and cattle grazing is more common there. The Milk River drains the
central part of the Northwestern Glaciated Plains.
The Northwestern Great Plains Ecoregion (43) is an immense expanse of semi-
arid, rolling plains, dissected by many intermittent and ephemeral stream channels. Open-
forested or savannah-covered buttes also occur in the vast region. Some areas of
badlands, treeless rolling hills and benches, and a few perennial rivers and streams are
present. Low precipitation precludes cropland, except in a few areas such as the Judith
River basin. Most of the ecoregion is rangeland, much remains in native grasslands. Soils
are highly erodible in many parts of the area. The Yellowstone River is a prominent
feature of this region.
Human Influence
The extent of urban development and cropland plotted on the map in Figure 1
only hints at the extent of human influence in the State. Many human activities in the
State affect, or have the potential to affect, water quality and aquatic habitats. The
contrasting physical environments in the eastern and western parts of the State influence
39
-------
An Assessment of USEPA Region 8 Streams and Rivers
the characteristics of human activity as well as the intensity and nature of their influence
on aquatic resources.
Grasslands and croplands dominate the eastern parts of the State, while forests
dominate the western mountains (Figure 1). Grasslands are also common in the
southwestern corner of the State.
| Water
HI Urban
£ Barren
| Forest
"I Shrub land
| Grassland
j Cropland
| Wfetland
Kilometers
Figure 1. Montana land cover.
Human-caused impacts to aquatic resources in the Northern Rockies Ecoregion
(15) include impacts attributable to logging and mining in the mountains and grazing,
residential development, irrigated and non-irrigated cropland, lumber mills, and gravel
and sand extraction in the valleys. Recreational activities, especially motorized, may also
affect water quality in this ecoregion.
Logging, mining, and the roads associated with these activities are major sources
of impact to streams and rivers in the Idaho Batholith Ecoregion (16). Soils in this region
are highly erodable, and sediment deposition is a consequence of human activity. Grazing
and recreation are also potential sources of disruption to aquatic habitats.
Forestry and mining activities potentially impact aquatic resources in the
Canadian Rockies (41). Recreation may also threaten streams and rivers here.
40
-------
An Assessment of USEPA Region 8 Streams and Rivers
The arid Wyoming Basin Ecoregion (18) supports some livestock grazing, and
irrigated agriculture may be found along the Clarks Fork of the Yellowstone River. These
are the major threats to aquatic resources in the region due to erosion and the introduction
of nutrients.
Industrial activities such as mining and smelting have had immense and long-
lived impacts on the aquatic resources of the Middle Rockies Ecoregion (17). In addition,
logging, mining, and grazing are potential sources of habitat and water quality
degradation. The effects of historic large-scale mining activities, especially in Butte, but
also in other areas of the region are a grave concern. Periodic dewatering of streams and
rivers is not uncommon in the region. Residential development and recreation are also
potential sources of impact.
Cattle grazing and cropland impacts are potential sources of degradation to habitat
and water quality for the aquatic resources of the Northwestern Glaciated Plains
Ecoregion (42).
Grazing, especially where soils are erodable has the potential to degrade streams
and rivers in the Northwestern Great Plains Ecoregion (43). Where cropland exists,
impacts associated with it are of concern. Recent development of coalbed methane
resources in the Powder River area has great potential for degradation of water quality
due to the introduction of additional dissolved salts into the already alkaline waters.
Extent of Streams
Estimation of the total length of Montana streams in this study is based on
information about the perennial stream network contained in US EPA's River Reach file,
which is a model based on an interpretation of 1:100,000 scale USGS topographic maps.
Only perennial streams and rivers were included. There is an estimated 48,195 kilometers
of perennial streams in the State.
According to the EMAP design, first order streams account for approximately
29% of the total length of perennial streams in Montana (Figure 2). The model does not
include the Missouri River. By far, the greatest extent of stream length is located in the
Middle Rockies Ecoregion (Figure 3), which contains 49% of the total state stream
length.
Table 1 contains the estimated extent of kilometers of perennial streams in the
State, and indicates the number of sites in each ecoregion/stream order category used in
the statewide analysis.
41
-------
An Assessment of USEPA Region 8 Streams and Rivers
5th +
Stream Order
Figure 2. Distribution of streams in Montana by Strahler stream order and percent of total
stream kilometer. Values were calculated based on the western EMAP survey design.
NW GREAT PLAINS
NW GLACIATED PLAINS
CANADIAN ROCKIES
MIDDLE ROCKIES
NORTHERN ROCKIES
10
20 30 40
Percent of stream kilometers
50
60
Figure 3. Statewide extent of Montana stream length, estimated by the EMAP design, in
Level III Ecoregions. Only 5 of the 7 ecoregions in the State are shown since less than
1% of statewide stream extent is estimated to lie in the Idaho Batholith (16) and
Wyoming Basin (18) Ecoregions.
42
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 1. Stream kilometers statewide within each ecoregion by stream order as
represented in the EMAP design.
Ecoregion
Stream
order
Stream
length
(km)
Representative
sites
1st
2009.8
1
15
2nd
2009.8
2
Northern
3rd
0
0
Rockies
4th
0
0
5tn +
3433.4
3
1st
0
0
16
Idaho Batholith
2nd
513.0
1
3rd
0
0
4m
0
0
5m +
0
0
1st
8596.8
7
17
Middle Rockies
2nd
5600.5
9
3rd
5301.2
11
4th
683.9
1
5tn +
3363.7
3
1st
1025.9
1
41
2nd
1517.9
2
Canadian
3rd
1607.8
2
Rockies
4th
0
0
5m +
0
0
Mountain total
35663.7
43
1st
1025.9
1
42
2nd
0
0
NW Glaciated
3rd
1308.1
4
Plains
4th
1846.7
3
5m +
384.7
1
1st
947.0
2
43
NW Great Plains
2nd
1538.9
3
3rd
1179.8
4
4th
1846.7
3
5th +
2453.7
5
Plains total
12531.5
26
Data Sources
Statewide results are based on the probability design model of the EMAP study of
Montana streams and rivers. A total of 80 probability sites (Figure 4) were sampled in the
State. However, only 69 sites were available to be used in this report for assessment due
to sampling issues. Sites on the Yellowstone, Flathead, and Kootenai Rivers were
excluded from the statewide assessment data, but geospatial data from these sites,
43
-------
An Assessment of USEPA Region 8 Streams and Rivers
including their total in-state stream length, is included in estimates. The stream length
represented by these sites appears as "not assessed" in graphs of disturbance class extent.
There were a total of 64 sites with biological, chemical, and geospatial data;
many of these sites are represented by both reachwide (64 sites) and targeted riffle (45
sites) macroinvertebrate sampling methods. Reachwide and targeted riffle samples are
analyzed separately in this report, for purposes of comparing statewide results from each
sampling method. Although shore-collection methods for non-wadeable streams were
necessarily different from either reachwide or targeted riffle sampling, samples collected
this way were grouped with the more-similar reachwide samples. Periphyton samples
were collected at a total of 78 EMAP sites. Samples from sites in the Middle Rockies
Ecoregion (32 sites) were analyzed for sediment disturbance.
The EMAP assessment strategy relies on assigning weights to ecoregions, stream
orders, and other physical or geographic variables, based on their extent within the study
area, so that randomly selected sites within a stratified framework produce data that
represents the variety of flowing waters in the State. Each sampled site is considered to
represent a calculated proportion of total stream kilometers within a stratum. The design
thus allows for an estimate of stream length within each of a number of geographic,
hydrologic, and assessment classifications. The biological or chemical condition of a site
is extrapolated to the length of stream represented by the site.
• •
MONTANA
• Probability Sites
• Hand-Picked Sites
| Mountains
Rains
Xenc (Wyoming Basin)
150
300
Figure 4. EMAP sampled sites (black dots represent probability sites and blue dots are
hand-picked sites).
44
-------
An Assessment of USEPA Region 8 Streams and Rivers
Assessment
In this study, disturbance classifications are assigned to stream sites based on
evaluation of macroinvertebrate communities, periphyton assemblages, and nutrients.
Evaluations were made using multimetric index and predictive model tools for
macroinvertebrates, and a discriminant function tool for periphyton; development of
these assessment tools is summarized in the next sections. Biological tools were
developed based on the characterization of reference condition, and comparison of site
characteristics with reference site characteristics. Nutrient concentrations were evaluated
against draft criteria (Suplee et al 2007) which are proposed for ecoregions in various
seasons.
Reference Site Determination
Biological disturbance at a site cannot be adequately assessed without a
determination of the potential of the site. Reference sites are those sites that are
considered to be at their biological potential, or as near to that condition as possible.
Given the scarcity of sites that are not influenced in some way by human activities,
usually to the detriment of biological integrity, the use of minimally disturbed sites to
represent attainable potential is often the only recourse. Since aquatic environments in the
surface waters of the State vary greatly, from the cold, cobble-bottom streams of the
mountainous regions to the warm, near-lentic, soft-bottom streams of the plains regions,
reference condition must be determined for a wide range of environmental conditions. In
general, Level III Ecoregions have been demonstrated to be a useful model for the initial
partitioning of environmental conditions. At a finer scale, certain geospatial
characteristics, such as elevation and watershed area, also influence biology. To address
these issues, the Montana Department of Environmental Quality (MDEQ) developed an
evaluation process for assessing candidate reference sites in order to establish benchmark
conditions for the aquatic biology of each of the various ecoregions of the State (Suplee
et al 2005). Quantitative watershed and water quality analyses are conducted for each
candidate site. In addition, qualitative assessments of stream health and habitat condition
are performed, using specific criteria as well as best professional judgment.
The quantitative watershed analysis includes study of land-cover types; in
particular, the proportion of agricultural use is determined at the 5th code HUC level.
Road density upstream of the candidate site is evaluated. Where available, water quality
data are assessed, particularly for heavy metals.
Qualitative assessments are composed of a series of 7 tests or "screens" that use
both best professional judgment as well as other criteria. Sites are screened for
disturbance that exceeds a minimal level, generally reflecting cumulative impacts from
multiple causes. Sites lacking sufficient site-specific data collected in the field are
screened out. Using quantitative measures and best professional judgment, cold water
streams in forested areas are eliminated from consideration if either road density or
timber harvest intensity in the watershed is judged to be influential. Sites are screened for
the intensity of agricultural land use. Sites that show a clear tendency to exceed numeric
45
-------
An Assessment of USEPA Region 8 Streams and Rivers
water quality standards, and sites that may be influenced by abandoned mines are
removed. Sites that pass all 7 screens are considered reference sites.
Reference sites identified by MDEQ's process were used to develop the
biological assessment tools that assigned disturbance classifications to the sites in this
study. Determination of ecoregion-specific reference condition that incorporates
influential geospatial characteristics by assessing and screening candidate sites is an on-
going process at MDEQ.
Biological Indicators
MDEQ uses 2 indicators of biological health for macroinvertebrate assemblages:
a multimetric index (MMI) and a predictive model (O/E). Both tools rely on comparison
of assemblages with reference assemblages, but the methods differ on the assignment of
sites to an appropriate group for which reference conditions have been determined, and in
how the comparisons are made. In practice, MDEQ uses both the MMI and O/E tools and
assigns disturbance classifications based on a decision tree, when the tools give different
results.
To date, assessment of periphyton community health is limited to a single tool,
developed specifically for a single ecoregion (Middle Rockies) and for a specific stressor
(sediment). In this report, disturbance classifications based on periphyton assessment are
assigned and reported only for Middle Rockies sites. In spite of its limitation to the
assessment of sediment stress, this tool is used in calculations of the relative risk of
chemical stressors in this study.
Development of Biological Assessment Tools
The Multimetric Index (MMI)
Development of the MMI approach began with a classification of reference sites,
based on an ordination of the taxonomic components of their macroinvertebrate
assemblages (Jessup et al 2006). For Montana, the recommended classification model
uses 3 site classes: Mountains, Low Valleys, and Plains. Mountains are distinguished
from Low Valleys by site elevation, annual mean of daily maximum air temperature, and
the annual precipitation. Biological metrics expressing attributes of the communities such
as richness, composition, function, habit, voltinism, and pollution tolerance were
calculated for both reference assemblages and assemblages from sites known to be most-
disturbed. Within each site class, metrics that predictably and efficiently discriminated
between reference sites and impacted sites were selected. Metrics were further screened
to identify those with low variability for reference condition, ecological interpretability,
and contribution of unique information. Metrics that were redundant with other metrics
were eliminated. The work resulted in 3 site class-specific indices. Scoring criteria for
metrics were based on the 95,h percentile of metric performance for all data within a
given site class. Table 2 lists the metrics selected for each site classification, and gives
the expected response of each metric to increasing stress. Disturbance classifications
46
-------
An Assessment of USEPA Region 8 Streams and Rivers
were assigned to sites using the criteria given in Table 3. Montana chose to assess
macroinvertebrate condition using reachwide and targeted riffle data separately. This
differed from most other state and ecoregion assessments in this report.
Table 2. Metrics and expected responses. MMI indices for Montana site classifications.
Site class
Metric
Expected response to
increasing stress
Mountain
Ephemeroptera taxa
Decrease
Plecoptera taxa
Decrease
% EPT
Decrease
% Non-insect
Increase
% Predator
Decrease
Burrower taxa %
Increase
Hilsenhoff Biotic Index
Increase
Low Valley
% EPT excluding Hydropsychidae and Baetidae
Decrease
% Chironomidae
Decrease
% Crustacea and Mollusca
Increase
Shredder Taxa
Increase
% Predator
Decrease
Plains
EPT taxa
Decrease
% Tanypodinae
Decrease
% Orthocladiinae of Chironomidae
Increase
Predator taxa
Decrease
% Filterers and Collectors
Increase
Table 3. Criteria for the assignment of disturl
>ance classifications using MMI and O/E.
Site class
MMI
O/E
Disturbance class
Mountain
>63
>0.8
Least-disturbed
<63
<0.8
Most-disturbed
Low Valley
>48
>0.8
Least-disturbed
<48
<0.8
Most-disturbed
Plains
>37
>0.8
Least-disturbed
<37
<0.8
Most-disturbed
O/E Model
Similar to the multimetric assessment tool, development of the O/E model began
with a classification of reference sites, based on analysis of an ordination of the
taxonomic components of macroinvertebrate assemblages (Hawkins 2005; Jessup et al
2006). Reference site classes were analyzed to determine variables that could reliably
predict the probability of class membership. For Montana, these predictor variables were:
latitude, longitude, annual mean of daily maximum temperature, and watershed area. A
discriminant function model was derived for estimating the probability of class
membership of a site based on the predictor variables.
47
-------
An Assessment of USEPA Region 8 Streams and Rivers
Taxonomic composition of reference samples was analyzed to determine the
frequency of occurrence of each taxon in each site class. Each frequency of occurrence,
when weighted by the probability of a site belonging to a class, represented the
probability of capture for a particular taxon. The sum of the probabilities of capture for
each taxon is interpreted as a prediction of the expected number of taxa at a site. Only
taxa with a probability of capture greater than or equal to 0.5 are used. Sites are evaluated
by comparing the observed number of taxa (O) with the expected number of taxa (E). The
proportion of O/E is interpreted as the degree to which a site is attaining its potential in
biological diversity. Disturbance classifications were assigned to sites using the criteria
given in Table 3.
Periphyton Assessment
Periphyton bioassessment methods developed for MDEQ use an empirically-
derived list of diatom taxa ("increaser taxa") that respond in a measurable way to stress
from sediment (Teply and Bahls 2005; Teply and Bahls 2007). Further, these are taxa that
exist in detectable abundances in samples from both stressed and least-disturbed streams.
Model development was restricted to data from the Middle Rockies Ecoregion.
Discriminant analysis was used to determine the probability of disturbance by
sediment for a dataset of randomly chosen samples collected since 1995 from both
stressed and least-disturbed streams in the Middle Rockies Ecoregion (Teply and Bahls
2006). The percent abundance of "increaser" taxa was used to derive a discriminant
function that can be used to predict the probability that a site is impacted by sediment
stress.
Table 4 gives the probability of disturbance by sediment for values of abundance
of "increaser taxa". Development of discriminant functions for other stressors and other
ecoregions is an on-going effort at MDEQ. For this particular report, the threshold for
disturbance was considered if the probability of sediment disturbance was above 56%.
Table 4. Probability of sediment disturbance for Middle Rockies sites based on the
Percent
Probability
Relative
of Sediment
Abundance
Disturbance
5
5.31%
10
11.56%
15
21.80%
20
35.92%
25
52.30%
30
68.30%
35
81.45%
40
90.54%
45
95.83%
50
98.42%
48
-------
An Assessment of USEPA Region 8 Streams and Rivers
Evaluation of Stressors
Reference condition for nutrient concentrations (nitrogen, phosphorus, and
ammonia) were defined by MDEQ by establishing the frequency distributions of nutrient
values from least-disturbed streams throughout the State. Streams were stratified
according to ecoregion and data were further stratified according to seasonality, since the
seasonal differences in median nutrient concentrations in the general population of
samples is significant (Suplee et al 2007). Regional scientific studies were reviewed; the
studies identified nutrient concentrations at which impacts to beneficial uses appeared.
These nutrient concentrations matched, on average, the 86th percentile of reference
condition concentrations. Based on these findings, draft criteria for assessment of stress
due to nutrients were set at the 85th percentile of reference condition. It should be noted
that these draft ammonia criteria represent much lower concentrations than
concentrations shown to have a toxic effect on aquatic life (DEQ 2006). Therefore, these
are nutrient-enrichment values, not toxicity values.
Draft seasonal criteria for nutrients in Montana ecoregions is presented in Table 5
(A-C). For most of the extent of the Clark Fork River, separate nutrient numeric criteria
apply. These thresholds are presented in Table 5 (D). Clark Fork River standards apply
from June 21 to September 21.
Table 5. Seasonal nutrient thresholds for Montana ecoregions. Dashes in the tables
indicate that there were too few observations in the data to generate valid distributions.
A. Winter season
Middle Rockies
(17)
Northwestern
Glaciated Plains (42)
Northwestern Great
Plains (43)
Total N mg/1
-
0.089
1.670
Total P mg/1
0.020
2.825
0.179
Ammonia mg/1
0.010
0.173
0.046
B. Runoff season
Middle Rockies
(17)
Total N mg/1
-
Total P mg/1
0.040
Ammonia mg/1
0.010
C. Growing season
Northern
Middle
Canadian
Northwestern
Northwestern
Rockies
Rockies
Rockies
Glaciated
Great Plains
(15)
(17)
(41)
Plains (42)
(43)
Total N mg/1
-
0.320
0.158
1.399
2.980
Total P mg/1
0.003
0.020
0.003
0.178
0.327
Ammonia mg/1
-
0.010
0.005
0.101
0.073
49
-------
An Assessment of USEPA Region 8 Streams and Rivers
D. Nutrient criteria for the Clark Fork River
Clark Fork River
near Tarkio, MT
Total N mg/l
0.300
Total P mg/l
0.039
Ammonia mg/l
-
Reachwide and Shore Sampling Methods Results
Biological Condition
The extent of impacted and least-disturbed biological condition in the State,
based on the analysis of 69 sites in the EPA probability model, and using the data
generated by the reachwide and shore sampling methods are summarized in Figure 5.
These analyses suggest that about 60% of stream length (about 28,900 kilometers) in the
State is classified as least-disturbed. About 33 % of stream length fell into the most-
disturbed category. About 7% of Montana stream Length was not represented in this
analysis. The MMI and O/E assessment tools gave similar estimations of the kilometer
extent of biological condition. A site-by-site comparison indicates that MMI and O/E
assessments agreed in 78% of cases (54 of 69 samples). Confidence intervals do not
overlap, indicating statistically significant results.
The statewide percent of stream kilometers in each Strahler stream order class
classified as most-disturbed by the biological assessment tools is plotted in Figure 6. The
wide extent of impact of first order stream length is an unexpected result; the MMI
indicates disturbance in more than 75% of first order stream kilometers statewide and the
O/E tool indicates most-disturbed condition in more than 60% of first order stream
extent. MMI results suggest that third order streams have the lowest extent of most-
disturbed condition, while the O/E suggests that fifth order streams have the lowest extent
of most-disturbed condition.
50
-------
An Assessment of USEPA Region 8 Streams and Rivers
Reachwide and Shore
MMI
O/E
10 20 30 40 50 60 70 80
Percent of stream kilometers
90 100
^igure 5. Biological condition evaluated for reachwide and shore samples using
macroinvertebrate assessment tools (green is least-disturbed, red is most-disturbed, and
gray is not assessed). Data for 69 sites sampled with the reachwide or shore protocol are
depicted.
Reachwide and Shore
MMI (n=69)
~ 1st
~ 2nd
¦ 3rd
3 4th
¦ 5th+
O/E (n=69)
JO 20 30 40 50 60 70 80
Percent of stream kilometers impaired
90
100
Figure 6. Statewide extent of disturbance of total stream kilometers in each Strahler
stream order. Data for 69 sites sampled with the reachwide or shore protocol are depicted.
51
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Extent
The approximation of most-disturbed stream length for chemical stressors is
presented in Figure 7. Appropriate criteria, as in Table 5, for nutrients were applied, and
disturbance classifications based on exceedances of the criteria.
The model suggests that about 20% of stream length (about 9,640 kilometers)
statewide was in most-disturbed condition using thresholds for total phosphorus. Sixty-
nine percent (about 33,255 kilometers) of total stream length was least-disturbed, and
about 10% of stream length was not assessed for total phosphorus.
The analysis suggests that most-disturbed condition for total nitrogen was present
in 10% of stream length (about 4,820 kilometers) in the State. Sixty-seven percent (about
32,290 kilometers) were least-disturbed. Twenty-three percent of stream length was not
assessed for total nitrogen. Most-disturbed condition for ammonia1 had the greatest extent
chemical disturbance; 28% of statewide stream length (about 13,500 kilometers)
exhibited most-disturbed condition. Least-disturbed condition was found in 53% of
stream length (about 25,540 kilometers). Nineteen percent of stream length was not
assessed for ammonia.
Reachwide and Shore
PHOSPHORUS
NITROGEN
AMMONIA
I
10 20 30 40 50 60 70
Percent of stream kilometers
80
90
100
-igure 7. The statewide extent of disturbance classifications for 3 chemical stressors
(green is least-disturbed, red is most-disturbed, and gray is not assessed). Data for 69
sites sampled with the reachwide or shore protocols are depicted.
1 Ammonia concentrations were elevated above concentrations derived from regional reference
streams, but they did not exceed toxicity ammonia thresholds in DEQ-7 (DEQ 2006).
52
-------
An Assessment of USEPA Region 8 Streams and Rivers
The statewide percent of most-disturbed stream kilometers, as assessed with
appropriate criteria for each chemical stressor, in each Strahler stream order class is
represented in Figure 8. Compared to higher stream orders, first order streams have
greater extent of disturbance for phosphorus and nitrogen. However, disturbance by
ammonia has greater extent in second and third order streams.
Reachwide and Shore
PHOSPHORUS (n=69)
NITROGEN (n=69)
~ 1st
~ 2nd
¦ 3rd
¦ 4th
¦ 5th+
AMMONIA (n=69)
10 20 30 40 50 60 70 80
Percent of stream kilometers impaired
90 100
"igure 8. Statewide extent of most-disturbed stream length for each chemical stressor in
each Strahler stream order. Data for 69 sites sampled with the reachwide or shore
protocols are indicated
Targeted Riffle Sampling Method Results
Forty-five sites were sampled with targeted riffle methods; in this section, these
are evaluated for estimates of the extent of biological and chemical disturbance and
relative risk of biological disturbance for each chemical/nutrient stressor. Since there
were more reachwide and shore samples in the dataset, measures of the extent of
disturbance and the extent of stressors would be more representative of statewide
conditions if that data were used. More than 30% of total statewide stream length was
unassessed by targeted riffle samples, compared to only 7% of stream length that was not
assessed by reachwide and shore methods. The effect of the different sample size is most
apparent when relative risk is assessed.
53
-------
4/7 Assessment of USEPA Region 8 Streams and Rivers
Targeted riffle
Percent of stream kilometers
Figure 10. Biological condition of targeted riffle samples using macroinvertebrate
assessment tools (green is least-disturbed, red is most-disturbed, and gray is not
assessed). Data for 45 sites sampled with the targeted riffle protocol are depicted.
Biological Condition
Similar to the findings for the reachwide sampling method, the analysis of
targeted riffle samples indicates that the greater proportion (>45%) of total statewide
stream length is classified as least-disturbed as evaluated with MDEQ macroinvertebrate
assessments. About 22% of total statewide stream extent is most-disturbed. Figure 10
plots the percent of total stream length in each disturbance category when targeted riffle
samples are analyzed.
The assessment methods give similar estimates of the extent of disturbance. The
MMI and O/E resulted in the same disturbance classification for 82% of targeted riffle
samples.
Like their reachwide counterparts, targeted riffle samples indicate a wider extent
of disturbance for first order streams than for other Strahler stream orders when
macroinvertebrate tools are used for assessment. The statewide extent of disturbance for
each stream order is graphed in Figure 11.
54
-------
An Assessment of USEPA Region 8 Streams and Rivers
Targeted riffle
MMI (n=45)
~ 1st
~ 2nd
¦ 3rd
ca 4th
¦ 5 th+
O/E (n-45)
10 20 30 40 50 60 70 80
Percent of stream kilometers impaired
90
100
ngure 11. Statewide extent of disturbance of total stream miles in each Strahler stream
order. Data for 45 sites sampled with the targeted riffle protocol are depicted.
Stressor Extent
The graph of the statewide extent of stressors for targeted riffle samples differs
from the corresponding reachwide graphs only in the number of samples used to estimate
extent. Thus it is not surprising that analysis of targeted riffle results are similar to
reachwide results, both for the statewide extent of stressors (Figure 12) and for the extent
of stressors within each Strahler stream order (Figure 13).
55
-------
An Assessment of USEPA Region 8 Streams and Rivers
Targeted riffle
PHOSPHORUS
I |
1
NITROGEN
AMMONIA
0 10 20 30 40 50 60 70 80 90 100
Percent of stream kilometers
Figure 12. The statewide extent of disturbance classifications for 3 stressors (green is
least-disturbed, red is most-disturbed, and gray is not assessed). Data for 45 sites sampled
with the targeted riffle protocol are depicted.
Targeted riffle
PHOSPHORUS (n=45)
NITROGEN (n-45)
AMMONIA (n-45)
1 , , . 1 i 1 1 r— 1 1
~ 1st
~ 2nd
¦ 3rd
0 4th
¦ 5th+
10 20 30 40 50 60 70 80
Percent of stream kilometers impaired
90 100
Figure 13. Statewide extent of most-disturbed stream length for each chemical stressor in
each Strahler stream order. Data for 45 sites sampled with the targeted riffle protocol are
depicted.
56
-------
An Assessment of USEPA Region 8 Streams and Rivers
Periphyton Results: Sediment Disturbance in the Middle Rockies Ecoregion
Thirty-two sites in the Middle Rockies Ecoregion were sampled for periphyton.
Two of the 32 sites are not included in the statewide analysis, since they did not fit the
probabilistic model criteria for inclusion in the EMAP dataset. Manipulation of the EPA
model was necessary in order to obtain stream extent estimations that included the added
sites. A simple model manipulation was used. Length estimates were assigned to the
added sites by totaling the number of stream kilometers within each Strahler stream order
class, and averaging that total extent over the number of sites included in the larger
periphyton dataset. Although this manipulation does not account for all of the variables
considered for weighting in the EPA model and likely violates rules used to construct it,
the estimations are probably reasonable for this analysis.
Figure 15 plots the percent of total Middle Rockies Ecoregion stream length in
each disturbance category when the periphyton sediment disturbance tool is used. The
analysis indicates that 86% of total stream length in the Middle Rockies is in least-
disturbed condition by sediment. About 12% of stream length in the region is in most-
disturbed condition by sediment. About 2% of stream length was not assessed. The
results were statistically significant.
Middle Rockies: sediment disturbance
b
0 10 20 30 40 50 60 70 80 90 100
Percent of stream kilometers
^igure 15. The extent of sediment disturbance classifications in the Middle Rockies
Ecoregion, as estimated by the periphyton sediment tool (green is least-disturbed, red is
most-disturbed, and gray is not assessed). Data for 33 sites in the Middle Rockies
Ecoregion that were sampled for periphyton are depicted.
Figure 16 plots the percent of sediment-impacted stream kilometers, as assessed
with the periphyton tool, in each Strahler stream order class for the Middle Rockies
Ecoregion. Only about 6% of first order streams in the region are impacted by sediment,
57
-------
An Assessment of USEPA Region 8 Streams and Rivers
while disturbance by sediment is more extensive in third order streams (about 25% of
stream length) and stream systems fifth order and larger (about 20% of stream length).
Periphyton sediment impairment
PER1PHYTON (N=33)
~ 1st
Q| 2nd
¦ 3rd
¦ 4th
¦ 5th+
10 20 30 40 50 60 70 80
Percent of stream kilometers impaired
90
100
Figure 16. Extent of most-disturbed stream length in the Middle Rockies Ecoregion for
sediment, as estimated by the periphyton sediment tool, in each Strahler stream order.
Data for 33 sites in the Middle Rockies Ecoregion that were sampled for periphyton are
depicted.
Discussion
Site selection for EMAP sampling followed a carefully-crafted procedure,
designed to give an unbiased estimate of the condition of streams over a large geographic
area using a small number of samples. The probabilistic design ensures that (1) the
population being sampled is unambiguously described; (2) every element in the
population has the opportunity to be sampled with a known probability; and (3) sample
selection is carried out by a random process (US EPA 2002). It is possible that impacted
sites are simply overrepresented in the dataset; however, this seems very unlikely. EMAP
employed two types of samples, a "targeted riffle" sample and a "reachwide" sample.
Ideally, both sample types are collected from each sampled stream segment (US EPA
2002). (In the data analyzed in this report, paired reachwide and targeted riffle samples
were collected for 45 of 80 sites.)
The EPA model estimate indicates that the greater part of total stream length in
the State of Montana is located in the mountainous ecoregions. Streams in the plains
regions account for only about 26% of the State's total stream length. In the analysis of
reachwide and shore sample data, which is the larger of the 2 datasets treated in this
report, 7% (about 3400 kilometers) of statewide stream length was not assessed; the sites
excluded from the assessment were sites on the Yellowstone, Kootenai, and Flathead
58
-------
An Assessment of USEPA Region 8 Streams and Rivers
Rivers. Since several sites had reach wide samples but no targeted riffle samples, the
proportion of unassessed stream length was much greater (30%) in that dataset, rendering
both extent and relative risk estimates less reliable for those data.
Extent of Biological Disturbance: Macroinvertebrates
The reachwide and shore sample results show that about 60% of the assessed
stream length in the State can be considered biologically in least-disturbed condition. For
comparison, Stoddard et al (2005) reported that about 50% of stream length in the entire
Western EMAP study could be classified as least-disturbed. These findings suggest that
Montana has a greater extent of biologically intact stream and river length than the
Western United States as a whole. The interesting issues about the extent of biological
and nutrient disturbance in each ecoregion remain unanswered in the statewide analysis.
However, observations concerning disturbance in the various Strahler classes and
comparisons of the results of different sampling methods can be made.
The analysis of disturbance extent by stream order indicates that biological
disturbance is extensive among first order streams statewide. First order streams account
for about 29% of total stream length in the State. The MMI and O/E tools indicate
biological disturbance in 75% (10204 kilometers) and 63% (8,571 kilometers) of first
order streams, respectively. This finding runs counter to the perception that headwaters
ought to be the least impacted. While first order streams in plains regions may be exposed
to intense anthropogenic disturbance by cattle grazing and other agricultural activities,
first order streams in montane regions generally suffer less apparent disruption than
higher order streams in those regions. Since headwater streams in plains regions account
for only 14.5% of the total statewide first order length, the results of the analysis clearly
imply that the greater portion of first order stream length in montane regions is
biologically impacted. If accurate, this is an unexpected result.
Extensive biological disturbance of first order streams in the montane regions of
the State may be a consequence of the widespread forest fires that occurred during the
sampling years. Other possible causes of disturbance to these systems include acid
deposition or effects of recreation activities. On the other hand, the results may be
spurious and attributable to problems with site selection, sampling methods, or
assessment tools.
Although there was some representation of EMAP-style samples, development of
the MMI and O/E tools for use in Montana relied largely on data from samples collected
using MDEQ sampling protocols. It is not clear how samples produced with "traveling
kicknet" and "jab" techniques compare with EMAP samples, and whether assessment
tools based on these techniques are useful in evaluating EMAP samples. MMI and O/E
scores frequently differed between reachwide and targeted riffle samples (see below),
suggesting that differences in sampled habitats affect assessment scores. It is not
unreasonable to speculate that assessment tools are not readily transferable between
sample types.
59
-------
An Assessment of USEPA Region 8 Streams and Rivers
Another possible pitfall may be related to inherent problems with the MMI and
O/E tools with respect to their ability to accurately assess first order streams. Headwater
streams are unique environments, typically supporting fewer taxa in lower numbers, with
different functional characteristics. In montane regions, these are typically cold,
oligotrophic, and harsh environments; taxa that are ubiquitous in higher order streams do
not occur there. It is not clear whether accurate assessments of first order streams can be
expected from the same tools used to evaluate third and higher order streams. A site-by-
site analysis of the biological assemblages collected at these sites, and the responses of
individual metrics, indices, and predictive models to assemblage components may help to
shed light on these issues.
The estimate of the extent of biological disturbance was similar for both the MMI
and O/E assessment tools (Figure 7). There was also general agreement in the extent of
disturbance measured by reachwide and targeted riffle sampling methods (Figure 7 and
Figure 10). When site-by-site classifications are examined, it is apparent that MMI and
O/E disturbance classifications disagreed 20% of the time for reachwide samples and
18% of the time for targeted riffle samples. For 45 sites in the statewide dataset, results
from both a reachwide sample and a targeted riffle sample were available. In 14 cases
(29%), disturbance classifications given by MMI or O/E for reachwide samples did not
agree with classifications attained by targeted riffle samples. The O/E method performed
somewhat better than the MMI in this regard; whereas there was disagreement between
targeted riffle and reachwide sample results in 7 O/E classifications, 11 MMI results
disagreed.
Extent of Biological Disturbance by Sediment in the Middle Rockies Ecoregion within
Montana: Periphyton
Sediment disturbance in the Middle Rockies Ecoregion was not extensive,
affecting only 12% of stream extent region-wide. For comparison, Stoddard et al. (2005)
report that about 26% of stream length in the entire Western EMAP study are impacted
by sediment problems, mostly due to excessive fine sediments. In montane ecoregions
West-wide, about 21% of stream extent was in most-disturbed condition due to the
presence of more fine sediments than expected. The Western EMAP estimates, however,
are based on direct physical measures of relative bed stability (RBS) which is a
comparison between the particle sizes of sediments present in the stream channel with the
size of sediment particles a stream can move or scour during its flood stage. These
estimates may not be directly comparable to estimates which are based on a biological
model that predicts the likelihood of disturbance based on the relative abundance of
diatom taxa known to increase with the increase of fine sediment. However, the data
suggest that streams in the Middle Rockies Ecoregion may be less extensively sediment-
impacted than streams in montane ecoregions in the Western United States as a whole.
Distribution of sediment-disturbance among stream orders in the Middle Rockies
foEows an expected pattern. Lower order streams are less extensively impacted by
sediment, while middle order and higher order streams are more affected. High inputs of
fine sediment are typically associated with human influences on the landscape that result
60
-------
An Assessment of USEPA Region 8 Streams and Rivers
in erosion or increased flood frequency or magnitude, such as agriculture, logging, road
building, and grazing. Natural erosive episodes may also influence the sediment balance
in streams; these episodes may be related to forest fires or naturally erosive soil
composition. While natural causes of sediment input may affect first order streams in the
high mountains and wilderness areas, it is reasonable to assume that most human-
influenced erosion and hydrologic alteration are concentrated in middle to lower order
streams, where logging and its associated roads, as well as grazing and other agricultural
activities are more concentrated.
Extent of Disturbance by Nutrient Stressors
Montana ecoregions did not follow the pattern of the Western United States as a
whole for the relative extent of disturbance by nitrogen and phosphorus. The Western
EMAP study (Stoddard et al. 2005) found that for most regions in the West, the
proportion of stream length in poor condition for nitrogen (27%) was higher than the
most-disturbed extent for phosphorus (15%). In the montane ecoregions of the Western
United States, 26% of stream length was impacted by nitrogen, and 15% were impacted
by phosphorus. In contrast, the proportion of Montana stream extent with phosphorus
disturbance (20%) was 2 times greater than the extent impacted by nitrogen (10%).
Ammonia2 disturbance was not investigated by the Western EMAP study; in Montana
ecoregions, ammonia was the most extensive nutrient-caused disturbance, with 28% of
stream kilometers in most-disturbed condition statewide.
Analysis of stressor extent by stream order indicates that phosphorus pollution is
extensive in first order streams statewide, affecting 40% of total first order stream length
in the State. Although nitrogen exceedances were much less extensive than either of the
other 2 nutrients studied here, the greatest extent of disturbance by nitrogen was among
first order streams. Ammonia pollution was extensive not only in middle order and higher
order streams where septic systems and wastewater treatment facilities are typically
located, but second order streams were also extensively impacted by ammonia statewide.
The full individual Montana report contains further information comparing results
between the ecoregions within the State of Montana, as well as more detailed discussions
of individual site assessment (Montana DEQ 2008).
2 Ammonia concentrations were elevated above concentrations derived from regional reference
streams, but they did not exceed toxicity ammonia thresholds in DEQ-7 (DEQ 2006).
61
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of North Dakota
Introduction
The ecological resources of North Dakota provide substantial benefits to the State
through their socio-economic value. The State is supported through outdoor enthusiasts
who hunt, fish, boat, hike, and perform other outdoor activities, purchase items and
access to recreational areas for sporting pleasure and for the beauty and solitude of the
outdoors. Economic activities, such as agriculture, mining and tourism are dependent
upon the State's natural resources. Environmental assessments provide information that
allows state authorities to make informed decisions regarding the conservation and
development of those natural resources.
Alterations to stream habitats, such as fluctuations in temperature, increase in
sediment load, or toxic substances result from both natural and anthropogenic sources.
Changes in riparian habitats and physical composition of the streambed can affect the
composition of the aquatic community that, in turn, may favor tolerant species and loss of
sensitive species in the community. Such changes disrupt, or cause a decline, in species
diversity. Often, streams that have little disturbance will have a greater species diversity
than streams that have been disturbed. Assessments of biological, chemical, and physical
habitat characteristics can provide data from which to make accurate evaluations of the
condition of streams in North Dakota.
The Environmental Monitoring and Assessment Program (EMAP)-West was
initiated in North Dakota in 2000 by the U.S. Environmental Protection Agency
(USEPA) in cooperation with the U.S. Geological Survey (USGS) and the North Dakota
Department of Health (NDDH) to develop and demonstrate monitoring tools to produce
unbiased estimates of ecological condition in surface waters of the State. Information
from EMAP-West was used to establish baseline biological, chemical, and physical
habitat condition estimates. These can be used to make comparisons with similar
condition estimates obtained from future monitoring activities. Baseline condition
estimates can also be used to evaluate possible recovery of sites associated with
regulation, restoration, and conservation practices.
Study Area Description
North Dakota has an area of approximately 185,500 square kilometers and a
population of about 642,000 (2000 census). Major cities include Fargo, Bismarck, Grand
Forks, and Minot. The climate of the State is continental, with short warm summers and
cold prolonged winters. Annual precipitation ranges from about 14 inches (35 cm) in the
northwest to about 24 inches (60 cm) in the southeast. Pre-settlement vegetation across
most of the State was predominately prairie grass with occasional forests along streams.
Since settlement, the State has developed considerable agricultural production of crops
including sunflowers, canola, sugar beets, wheat, soybeans, and corn. Major rivers in the
State include the James, Sheyenne, Pembina, Souris, Missouri, Little Missouri, Heart,
62
-------
An Assessment of USEPA Region 8 Streams and Rivers
Knife, Cannonball and Red River of the North. Many of the streams have dams that form
significant reservoirs such as Lake Sakakawea, Lake Oahe, Jamestown Reservoir, Lake
Ashtabula, Lake Tschida, Lake Patterson, and Lake Darling.
North Dakota is covered by four Level III Ecoregions as defined by Bryce et al
(1998). The ecoregions are the Northwest Glaciated Plains (42), the Northwest Great
Plains (43), the Northern Glaciated Plains (46), and the Lake Agassiz Plain (48) (Figure
1). In a recent ecological assessment of western streams and rivers, USEPA indicated that
North Dakota exists within two broader ecological areas, the Cultivated Plains, including
the Northern Glaciated Plains and Lake Agassiz Plain Ecoregions, and the Rangeland
Plains, including the Northwestern Glaciated Plains and Northwestern Great Plains
Ecoregions (Stoddard et al 2005a).
The Cultivated Plains region (Ecoregions 46 and 48) (Figure 1) is a flat to gently
rolling landscape composed of glacial till that has high concentrations of temporary and
seasonal wetlands. This area contains landscape features such as the Turtle Mountains,
the Prairie Coteau, a former glacial lake basin now occupied by Devils Lake, and the
Lake Agassiz Plain. The Lake Agassiz Plain was once filled with Glacial Lake Agassiz,
the last in a series of glacial lakes to fill the valley in the past three million years
(Omernik, 1987). Thick beds of lake sediments created the extreme low relief of the Lake
Agassiz Plain. Once covered with tall prairie grass, the Lake Agassiz Plain now has
intensive small grain and row crop agriculture (Figure 1).
The Rangeland Plains region is located in the southwest half of North Dakota
(Ecoregions 42 and 43) (Figure 1). The eastern portion of this ecological area is
dominated by the Coteau du Missouri, a series of glacial moraines. left after several
glacial advances. Most of the Coteau has little or no integrated drainage, but does have
numerous wetlands formed mostly by melting glacial ice. The remainder of the
Rangeland Plains region is made up of the Northwest Great Plains Ecoregion. The
landscape in this ecoregion is rolling to hilly with numerous streams, but few wetlands or
lakes. This area supports shortgrass grazing lands, and occasional intensively-cultivated
agricultural lands (Figure 1). The southwest portion of the Rangeland Plains is dominated
by rugged badlands and grasslands (Figure 1), which includes Theodore Roosevelt
National Park and the Little Missouri National Grasslands.
Aside from impacts from the larger cities and towns, the greatest impact to
streams in North Dakota is the result of agricultural production of crops and livestock.
Crop production practices can increase soil erosion, which permits excess nutrients,
pesticides, and sediments to enter streams. Construction of ditches, especially in the Lake
Agassiz Plain Ecoregion, has allowed fields to drain faster than would occur naturally.
Ditching has likely increased the volume of water and sediment load that enter streams
and likely cause alterations of the natural hydrology and geomorphology of streams.
Animal production, especially in confined areas, can produce excess nutrients, oxygen-
consuming organic matter, pathogens, and sediments that may enter streams.
63
-------
An Assessment of USEPA Region 3 Streams and Rivers
Northern Glaciated Plains
I
^ 1
. 46
\ Lake\
I Agassiz\
\ Plain 1
Northwestern Great Plains
Lj Northwestern 1
f Glaciated Plains \
n
43
42 \
100
Kilometers
N
EXPLANATION
I Water
| Urban
I Forest
1 Rangeland Plains
| Grassland
] Cropland
] Wetland
] Cultivated Northern
Plains
Figure 1. Land cover categories and ecoregions in North Dakota.
Sampling Site Determination
Probability and hand-picked sites were used to develop indicators and derive
threshold values for estimating stream condition. Probability sites were chosen by
statistical design and may not have been able to be sampled because of access restrictions
or lack of water. In the entire State of North Dakota, four sites were denied access by the
landowner and one site was inaccessible. Reference and stressed sites were hand-picked
sites selected based on anthropogenic land use practices. Reference sites represented
streams in a least-disturbed condition. Stressed sites represented streams that were in
64
-------
An Assessment of USEPA Region 8 Streams and Rivers
most-disturbed condition due to human impacts that degrade biotic integrity. Stressors to
the streams included chemical, physical and biological components such as increase in
nutrients, erosion of river-banks, and invasive species.
Extent of Streams
A total of 111 sites were selected and sampled in North Dakota (Figure 2). Forty-
one (41) probability sites and 27 hand-picked sites were selected in the Cultivated Plains
region, and 23 probability sites and 20 hand-picked sites were selected in the Rangeland
Plains region. All 23 probability sites in the Rangeland Plains and 40 of the 41
probability sites in the Cultivated Plains were used in the chemical stressor assessment.
All 23 probability sites in the Rangeland Plains and 39 of the 41 probability sites in the
Cultivated Plains were used in the physical habitat stressor assessment. Of the
approximately 6,900 kilometers of perennial streams within the State, an estimated 6,583
kilometers were represented in the chemical stressor assessments and in the periphyton
assessment (3,955 kilometers in the Cultivated Plains and 2,627 kilometers in the
Rangeland Plains). About 6,555 kilometers were represented in the physical habitat
stressor assessment and the macroinvertebrate assessment (3,928 kilometers in the
Cultivated Plains and 2,627 kilometers in the Rangeland Plains). Approximately 6116
kilometers of stream length was represented in the statewide assessment of mercury in
fish tissue.
NORTH DAKOTA
• Probability Sites
• Hand-Picked Sites
Cultivated Northern Plains
Rangeland Plains
• •
200
50
Figure 2. EMAP Western Pilot Project sampled sites in North Dakota (black dots
represent probability sites and blue dots are hand-picked sites).
65
-------
An Assessment of USEPA Region 8 Streams and Rivers
Reference Site Determination
The original designation for reference and stressed sites done by EMAP-West was
revised by the North Dakota Department of Health using local knowledge and by
incorporating a method developed by the State. North Dakota's method for defining
reference and stressed sites involved defining a set of metrics selected from the
landscape, physical habitat, and chemical data (Table 1). Biological data were considered
response variables and were not used in the designation of reference and stressed
sampling sites. Redundant metrics were eliminated using a correlation matrix. Each
metric was standardized using the 5th and 95th percentiles as the floor and ceiling for
each metric. The final Reference Index combined all of the final landscape, physical
habitat, and chemical metrics (Table 1) into a composite score ranging from 0-100. Sites
with Reference Index scores in the top 10 percent were designated as "reference", sites
with scores in the bottom 10 percent were designated as "stressed" for each region.
Table 1. Landscape, physical habitat, and chemical metrics used in the North Dakota
Reference Site Index.
Landscape Metrics
Physical Habitat Metrics
Chemical Metrics
Percent Urban Cover
Percent Embeddedness
Total Suspended Solids
Percent Agricultural
Cover
Percent Large Woody
Debris
Total Phosphorus
Percent Forest Cover
Percent Fines
Ammonia
Percent Wetland Cover
Sinuosity
Sulfate
Percent Side Channels
Total Nitrogen
Bank Canopy Cover
Nitrate
Because the reference site selection process which uses the Reference Site Index
is only capable of identifying 20% of the total sites in each ecoregion as reference or
stressed (10% reference and 10% stressed), this approach may possibly miss some
potential site designations. To account for this limitation, adjustments were made to the
final reference and stressed site selection process. Sites were evaluated by comparing
field sheets, reference scores and consulting the original EMAP-West designations to
identify sites as reference or stressed. For example, if the score for a site was just outside
the threshold for stressed but the field sheet comments were strongly indicating the site
being designated as stressed, the site was designated as stressed. A designation of
stressed or reference was also given to a site if both the EMAP-West designation and the
field sheets agreed, but the North Dakota Reference Index was inconclusive.
The location of a sampling site in agricultural or grassland areas did not fully
determine whether a site was considered stressed. Streams in croplands may have well-
preserved riparian zones and have a considerable amount of buffer vegetation and,
therefore, could be considered nearly undisturbed. Conversely, streams in grasslands may
have extensive activity along the riparian zone from grazing animals or development and
could therefore be considered highly disturbed.
66
-------
An Assessment of USEPA Region 8 Streams and Rivers
In order to accurately display error for each stream kilometer estimate, the
statistical program "R" was used to provide the upper and lower limits of each condition
class estimate and allowed graphical display of each estimate with confidence (R
Development Core Team 2007). All estimates were calculated using an "R" script written
specifically for this assessment.
Indicators
Macroinvertebrate Biotic Integrity
A separate multi-metric index (MMI) was developed for the Cultivated Plains and
the Rangeland Plains. The MMIs were developed specific to this dataset and this
assessment unit (i.e. North Dakota). The original EMAP-West plains macroinvertebrate
MMI did not perform well at the scale of this assessment unit with the revised reference
and stressed site list.
For MMI development in the Cultivated Plains and the Rangeland Plains regions,
datasets were separated into calibration and validation datasets. The first step involved
comparing box-plots of individual metrics to show separation between least disturbed
(reference) and most disturbed (stressed) sites.
The next step involved submitting the metrics to a redundancy test to determine
metrics not independently adding value to the MMI. The MMI was created using the
most responsive, non-redundant metrics. Additionally, an attempt was made to cover as
many ecological categories as possible, including richness, composition, diversity,
tolerance, feeding and habit guilds.
The final MMI for the Cultivated Plains region consists of six metrics: percent
EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa, percent abundance of individuals
that are predators, percent abundance of individuals rated 8 or 9 on the tolerance scale
(more tolerant), percent abundance of individuals rated 6 or 7 on the tolerance scale,
percent dinger taxa, and percent abundance of individuals that are collector-filterers.
There was one composition metric, two tolerance metrics, two feeding group metrics and
one habit metric. These metrics were scored from 0 to 100 based on the range of the
dataset, with the six values averaged for the final score. Least-disturbed and most-
disturbed condition class thresholds for the Cultivated Plains region were set at the 25th
and 5th percentiles of the least disturbed (reference) sites (Table 2). In the Cultivated
Plains region, scores greater than 55.7 were considered least-disturbed and scores less
than 49.4 were considered most-disturbed. Macroinvertebrate MMI scores greater than or
equal to 49.4 and less than or equal to 55.7 were considered moderately-disturbed.
Once the final score for each site was calculated, sites were classified with the
appropriate condition class according to each biological community. For instance, if the
total score for a site in the Cultivated Plains region was 48 (< 49.4), that site is considered
to be in most-disturbed condition based on the macroinvertebrate indicator.
67
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 2. Multi-metric Index thresholds used to determine condition class for biological
indicators in the Cultivated Plains region.
Condition Class
Biological
Community
Most-disturbed
Moderately-
disturbed
Least-disturbed
Macroinvertebrate
MMI
5th percentile OR
<49.4
>49.4 and <55.7
25th percentile
OR >55.7
Aquatic Vertebrate
MMI
5th percentile OR
<52.1
>52.1 and <61.5
25th percentile
OR >61.5
Periphyton MMI
10th percentile OR
<21.4
>21.4 and <44.1
25th percentile
OR >44.1
Table 3. Multi-metric Index thresholds used to determine condition class for biological
indicators in the Rangeland Plains region.
Condition Class
Biological
Community
Most-disturbed
Moderately-
disturbed
Least-disturbed
Macroinvertebrate
MMI
10m percentile OR
<22.5
>22.5 and <38.2
25th percentile OR
>38.2
Aquatic Vertebrate
MMI
NA
NA
NA
Periphyton MMI
10th percentile OR
<32.3
>32.3 and <42.5
25th percentile OR
>42.5
The final MMI for the Rangeland Plains region also consists of six metrics: EPT
richness, percent abundance of individuals that are dingers, percent abundance of
individuals that are collector-gatherers, percent predator taxa, percent of taxa rated 0 to 5
on the tolerance scale, and percent abundance of individuals rated 8 or 9 on the tolerance
scale. There was one richness metric, two tolerance metrics, two feeding group metrics,
and one habit metric. These metrics were also scored from 0 to 100 based on the range of
the dataset, with the six values averaged for the final score. Least-disturbed and most-
disturbed condition class thresholds for the Rangeland Plains were set at the 25th and the
10th percentile of the least disturbed (reference) sites (Table 3). In the Rangeland Plains
region, scores greater than 38.2 were considered least-disturbed and scores less than 22.5
were considered most-disturbed. Macroinvertebrate MMI scores greater than or equal to
22.5 and less than or equal to 38.2 were considered moderately-disturbed.
Each site visited was scored independently according to region (Cultivated Plains
or Rangeland Plains). Thresholds were determined for indicators within each region and
data were then pooled as least-disturbed, moderately-disturbed or most-disturbed for an
overall statewide assessment. Thirty-six (36) sites, representing 3,928 kilometers, were
used to assess the Cultivated Plains region, while twenty-three (23) sites, representing
2,627 kilometers, were used to assess the Rangeland Plains region. A total of 6,555 km of
streams were assessed statewide using the macroinvertebrate MMI.
68
-------
4/7 Assessment of USEPA Region 8 Streams and Rivers
For the State of North Dakota 3,141 stream kilometers (48%) were considered to
be in good condition with regards to macroinvertebrate biotic integrity, 1,602 kilometers
(24%) are estimated to be in moderately-disturbed condition and 1,813 kilometers (28%)
are estimated to be in most-disturbed condition (Figure 3).
4000
3500
I
E 2500
CD
S 2000
~ 1500
j
"igure 3. Condition class summary for perennial streams in North Dakota based on
macroinvertebrate MM I scores (green is least-disturbed, yellow is moderately-disturbed,
and red is most-disturbed).
Vertebrate Biotic Integrity
For the fish indicator, the MMI developed by EMAP-West for the EMAP-West
assessment (for the entire plains) was used for Ecoregions 46 and 48 (Cultivated Plains
region of North Dakota (Stoddard et al 2005a). The fish metrics in this MMI are: native
rheophilic (prefers running water) species richness; percent abundance of individuals
considered super tolerant; percent abundance of individuals that are nontolerant
invertivores or piscivores; sensitive spawner species richness; native catostomid/ictalurid
species richness (corrected for stream size); percent abundance of all species that are
native, sensitive, and migrators; non-tolerant species richness (corrected for stream size);
and percent abundance of individuals that are alien (non-native or foreign individuals).
In the Cultivated Plains region, a total of 3,591 out of 4,116 stream kilometers
were represented by the probabilistic sample reflecting 87% of the perennial stream
kilometers present in this region. Thresholds were set using the 25th and the 5th percentile
of the reference sites (Table 2). A score of greater than 61.5 is considered good while
69
-------
An Assessment of USEPA Region 8 Streams and Rivers
scores ranging between 61.5 and 52.1 are considered moderately-disturbed. Scores less
than the fifth percentile, or less than 52.1, are considered to be in most-disturbed
condition.
Within the Cultivated Plains region of North Dakota, 1,690 stream kilometers
(47%) are considered most-disturbed followed by 1,192 stream kilometers (33%)
estimated to be in moderately-disturbed condition. Only 709 stream kilometers (20%) are
considered to be in least-disturbed condition with regards to vertebrate biotic integrity
(Figure 4).
2500
2000
Figure 4. Condition class summary for perennial streams in the Cultivated Plains region
of North Dakota based on the fish MM1 (green is least-disturbed, yellow is moderately-
disturbed, and red is most-disturbed).
Due to relatively low species diversity in the Rangeland Plains region of North
Dakota (Ecoregions 42 and 43) the fish indicator performed poorly. Therefore, rather
than reporting on the biological condition of streams in this region through the use of an
MMI, we will provide a general description of the overall fisheries quality. Thirty-three
(33) probability and hand-picked sites were sampled with a total of 8,388 fish collected
via long-line electrofishing.
A total of 2,627 stream kilometers were assessed for general fisheries quality in
the Rangeland Plains region (Ecoregions 42 and 43) of North Dakota. In this region of
the State, 2,783 perennial stream kilometers are estimated to be present. Primary sportfish
represented only 3% of the total fish collected (271 individuals). Primary sportfish
70
-------
An Assessment of USEPA Region 8 Streams and Rivers
species included smallmouth bass, northern pike, channel catfish, sauger, walleye, white
crappie, bluegill, yellow perch and white bass (Figure 5).
Individuals
1) OO O M
3 O O O
1. ; 11
1 "0
I 20 4-1
|1 p
0 J
y
/ *
.si® A
I / J? c/ y J
Species
Figure 5. Abundance of primary sportfish in the Rangeland Plains region of North
Dakota.
Stream kilometer estimates of fish occurrence are based on presence/absence of a
particular species or family. For instance, if a single smallmouth bass (Centrarchidae) is
collected at four different locations and each location is representative of 125 stream
kilometers in the Rangeland Plains region, then the estimate for smallmouth bass will be
500 stream kilometers. The families Cyprinidae (minnows) and Catostomidae (suckers)
were the most frequently collected fish taxa. Both were equally represented in the
Rangeland Plains of North Dakota and were estimated to be present in 2,023 stream
kilometers. Ictalurids (catfish and bullheads) were estimated to be present in 1,846 stream
kilometers while Centrarchids (sunfish and black bass) were estimated to inhabit 1,523
miles of stream kilometers. Finally, Esocidae (pike) and Percidae (perch, walleye and
sauger) were estimated to be present in 1,302 and 1,221 stream kilometers, respectively
(Figure 6).
71
-------
An Assessment of USEPA Region 8 Streams and Rivers
3000
2500
J 2000
T _
£
1500
| 1000
95
500
n
FT1
/
/ / y ^
? jf <#
cf
Family
Figure 6. Stream length estimates of each fish family in the Rangeland Plains region of
North Dakota.
Interestingly, although the stream kilometer estimates, based only on occurrence,
are similar in the Rangeland Plains of North Dakota for each taxonomic group, the
relative abundance of fish is dominated by the family Cyprinidae at 82.9 percent.
Catstomidae was the next most abundant family and only accounted for 8.8 percent of
collected individuals. Centrarchidae and Ictaluridae accounted for 3.2 percent and 2
percent, respectively, while Percidae and Esocidae families were present in 1.2 percent
and 0.7 percent of the entire sample, respectively (Figure 7).
72
-------
An Assessment of USEPA Region 8 Streams and Rivers
l
AH
Q fin -
C en .
1 n
n
0*
X
r
c
J? /¦ /¦ J? /
r cf
Family
Figure 7. Percent abundance of each family of fish in the Rangeland Plains region of
North Dakota.
Periphyton Biotic Integrity
For the periphyton indicator, metric screening was similar to the MMI that was
developed for macroinvertebrates. A total of 250 diatom metrics covering 5 categories
were evaluated. First, box-plots of least (reference) and most disturbed (stressed) sites
were compared to show which metrics provided distinction between sites. Next, through
correlation analysis, non-redundant metrics were chosen with an attempt to include as
many ecological categories as possible.
In the Cultivated Plains region, 55 samples, including repeat visits, were
analyzed. Non-wadeable sites were also included in this assessment. The periphyton
metrics used in the MMI are: number of species in the genus Cymbella (old, or sensu
lato)\ percent of taxa that are highly motile; percent of taxa in the oxygen class 1 or 2
(that is, require high concentrations of O2); number of Gomphonema species; and percent
abundance of individuals in the genus Fragilaria.
In the Rangeland Plains region, a total of 70 samples were analyzed for North
Dakota. The final metrics chosen for the MMI were: percent of taxa in the genus
Cymbella (old, or sensu lato)\ percent abundance of taxa in the genus Fragilaria (old, or
sensu lato)\ percent abundance of individuals in the genus Nitzschia (new, or sensu
stricto)\ percent of taxa that are moderate or highly motile; and percent of taxa in the
oxygen class 1 or 2.
73
-------
An Assessment of USEPA Region 8 Streams and Rivers
For both the Cultivated Plains and the Rangeland Plains, least-disturbed and most-
disturbed condition class thresholds were set at the 25th and 10th percentile of the least
disturbed (reference) sites (Table 2). Similar to the macroinvertebrate indicator, each site
visited was scored independently, according to region (Cultivated Plains or Rangeland
Plains). Final scores were then calculated for each site and data was then pooled as least-
disturbed, moderately-disturbed or most-disturbed for an overall statewide assessment.
In the Cultivated Plains, scores greater than 44.1 were considered least-disturbed.
Scores that were greater than or equal to 21.4 and less than or equal to 44.1 were
considered moderately-disturbed while any site scoring less than 21.4 was considered to
be in most-disturbed condition. In the Rangeland Plains, any site scoring greater than
42.5 was considered least-disturbed. Site scores that were greater than or equal to 32.3
and less than or equal to 42.5 were in moderately-disturbed condition and anything less
than 32.3 was considered to be in most-disturbed condition.
Based on the periphyton MMI, North Dakota has 2,305 stream kilometers (35%)
in least-disturbed condition, 2,585 kilometers (40%) in moderately-disturbed condition,
and 1,665 kilometers (25%) in most-disturbed condition (Figure 8).
Condition Class
Figure 8. Condition class summary for perennial streams in North Dakota based on
periphyton MMI (green is least-disturbed, yellow is moderately-disturbed, and red is
most-disturbed).
74
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Indicators
Environmental stressors are defined as the chemical, physical habitat, and
biological components of the ecosystem that have the potential to degrade biotic integrity
and also the pressures that human beings exert on habitat systems through their use of the
surrounding environment (Stoddard et al 2005a). For this report, the environment is
defined as perennial streams in North Dakota. Chemical stressors in North Dakota
include excess nutrients and chemical contamination (pesticides and trace metals).
Physical habitat stressors include excess sedimentation, bed and bank erosion, and loss of
streamside vegetation. Biological stressors include the presence of invasive species. The
key to stressor assessment is determining how common a stressor is in a region and how
severely the stressor affects biotic integrity. During this assessment of perennial streams
in North Dakota, no biological stressors were evaluated for their affect on biotic integrity.
Chemical Stressors
Three chemical stressors, total phosphorus, total nitrogen, and specific
conductance, were assessed for both the Cultivated and Rangeland Plains regions of
North Dakota. A fourth chemical stressor, mercury in fish tissue, was assessed for
perennial streams in the State as a whole. These stressors were the same as those used in
the South Dakota assessment (Heakin et al 2006). Thresholds for total phosphorus, total
nitrogen, and mercury in fish tissue were the same as those used in South Dakota, while
the thresholds for specific conductance were the same as those used in the EMAP-West
report (Stoddard et al 2005a). Thresholds for the Cultivated Plains are shown in Table 4,
thresholds for the Rangeland Plains are shown in Table 5, and thresholds for mercury in
fish tissue are shown in Table 6.
Table 4. Threshold values used to determine condition classes for total phosphorus, total
nitrogen, and specific conductance for perennial streams in the Cultivated Plains region
of North Dakota.
Chemical Stressor
Most-
disturbed
Moderately-
disturbed
Least-disturbed
Total phosphorus
>312 pg/L
228-312 Mfi/L
<228 pg/L
Total nitrogen
>2501 pg/L
1525-2501 pg/L
<1525 pg/L
Specific conductance
>2000 |uS/cm
1000-2000 jiS/cm
<1000 (iS/cm
Table 5. Threshold values used to determine condition classes for total phosphorus, total
nitrogen, and specific conductance for perennial streams in the Rangeland Plains region
of North Dakota.
Chemical Stressor
Most-disturbed
Moderately-
disturbed
Least-disturbed
Total phosphorus
>138 |ig/L
70-138 ug/L
<70 pg/L
Total nitrogen
>1186 pg/L
886-1186 ug/L
<886 pg/L
Specific conductance
>2000 pS/cm
1000-2000 uS/cm
<1000 pS/cm
75
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 6. Threshold values used to determine condition classes for mercury in fish tissue
for perennial streams in North Dakota.
Most-disturbed
Moderately-
disturbed
Least-disturbed
>0.1 pg/g
Not Assessed
<0.1 Mg/g
Chemical stressor assessments for perennial streams in the Cultivated Plains of
North Dakota are shown in Figure 9. Based on the total phosphorus stressor, 1,645
kilometers (42%) of streams were found to be in most-disturbed condition and 1,616
kilometers (41%) were in least-disturbed condition. Only 668 kilometers (17%) of
streams were found to be in moderately-disturbed condition. Total nitrogen and specific
conductance stressor thresholds were exceeded for most-disturbed condition for only 238
kilometers (6%) and 373 kilometers (9%) of streams, respectively. The remaining 3,717
kilometers (94%) of streams were assessed to be in moderately-disturbed to least-
disturbed condition for total nitrogen and about 3,583 kilometers (91%) of streams were
assessed to be in moderately-disturbed to least-disturbed condition for specific
conductance.
Chemical stressor assessments for perennial streams in the Rangeland Plains
region are shown in Figure 10. Based on total phosphorus stressor thresholds, 1,031
kilometers (39%) of perennial streams in the Rangeland Plains region were found to be in
most-disturbed condition, while 1,249 kilometers (48%) of assessed streams were found
to be in least-disturbed condition and 341 kilometers (13%) were found to be in
moderately-disturbed condition. Total nitrogen and specific conductance stressor
thresholds were exceeded for most-disturbed condition for 479 kilometers (18%) and
1,200 kilometers (46%) of perennial streams, respectively. The remaining 2,148
kilometers (82%) of perennial streams were assessed in moderately-disturbed to least-
disturbed condition for total nitrogen and about 1,427 kilometers (54%) were assessed in
moderately-disturbed to least-disturbed condition for specific conductance. While a
relatively small percentage of perennial streams in the Cultivated Plains were assessed as
being in most-disturbed condition (9%) based on the specific conductance stressor, a
relatively large percentage of streams in the Rangeland Plains region (46%) were
assessed as being in most-disturbed condition based on the same stressor. This may be
due to climatic differences between the Rangeland Plains and the Cultivated Plains. The
Rangeland Plains area tends to be a dry, arid environment which may account for these
differences.
76
-------
An Assessment of USEPA Region 8 Streams and Rivers
0 500 1000 1500 2000 2500 3000 3500
Stream length (km)
-¦igure 9. Stream length in the Cultivated Plains considered least-disturbed (green),
moderately-disturbed (yellow), or most-disturbed (red) based on three chemical stressors.
0 500 1000 1500 2000 2500 3000 3500
Stream length (km)
Figure 10. Stream length, in kilometers, in the Rangeland Plains that were considered to
be in least-disturbed (green), moderately-disturbed (yellow), or most-disturbed (red)
condition based on three chemical stressors.
77
-------
An Assessment of USEPA Region 8 Streams and Rivers
The chemical stressor assessment of perennial streams for North Dakota as a
whole reflects the summation of the assessments for the Cultivated Plains and Rangeland
Plains regions (Figure 11). Based on total phosphorus stressor thresholds, 2,677
kilometers (41%) of perennial streams in North Dakota were found to be in most-
disturbed condition, while 2,866 kilometers (43%) of assessed streams were found to be
in least-disturbed condition and 1,040 kilometers (16%) were found to be in moderately-
disturbed condition. Total nitrogen and specific conductance stressor thresholds were
exceeded for most-disturbed condition for 717 kilometers (11%) and 1,573 kilometers
(24%) of perennial streams, respectively. The remaining 5,866 kilometers (89%) of
perennial streams were assessed in moderately-disturbed to least-disturbed condition for
total nitrogen, while about 5,010 kilometers (76%) were assessed in moderately-disturbed
to least-disturbed condition for specific conductance.
0 500 1000 2000 2500 3000 3500 4000 4500 5000
Stream length (km)
Figure 11. Stream length, in kilometers, in North Dakota as a whole that were considered
in least-disturbed (green), moderately-disturbed (yellow), and most-disturbed (red)
condition based on three chemical stressors.
Based on the mercury in fish tissue stressor, approximately 3,457 kilometers
(56%) of the perennial streams in North Dakota were assessed to be in most-disturbed
condition (mercury concentrations in fish tissue greater than 0.1 ng/g) (Figure 12). Only
about 1,830 kilometers (30%) of the perennial streams were considered to be in least-
disturbed condition based on the mercury in fish tissue stressor. Around 829 kilometers
of streams lack fish available for tissue analysis and therefore, were not assessed.
78
-------
An Assessment of USEPA Region 8 Streams and Rivers
1 1 1
^—
1
1
1 1 1 1 1 1
1
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Stream length (km)
Figure 12. Perennial stream length in North Dakota that was assessed in least-disturbed
(green) and most-disturbed (red) condition based on the mercury in fish tissue stressor
(gray is not assessed).
Physical Habitat Stressors
Four physical habitat stressors were assessed for North Dakota perennial streams:
streambed stability, riparian vegetation, riparian disturbance, and habitat complexity.
These stressors are the same as those defined and used in the EMAP-West assessment.
Thresholds for each physical habitat stressor for the Cultivated Plains region (Table 7)
and for the Rangeland Plains region (Table 8) were the same as those used in the South
Dakota assessment (Stoddard et al 2005a).
Table 7. Threshold values used to determine condition classes for streambed stability,
riparian disturbance, habitat complexity and riparian vegetation for perennial streams in
the Cultivated Plains region of North Dakota.
Physical Habitat
Stressor
Most-disturbed
Moderately-
disturbed
Least-disturbed
Streambed stability
<-2.58
-2.58 to -2.20
>-2.20
Riparian disturbance
>1.8
1.31-1.8
<1.31
Habitat complexity
<0.136
0.136-0.214
>0.214
Riparian vegetation
<0.041
0.041-0.236
>0.236
Table 8. Threshold values used to determine condition classes for streambed stability,
riparian disturbance, habitat complexity and riparian vegetation for perennial streams in
the Rangeland Plains region of North Dakota.
Physical Habitat
Stressor
Most-disturbed
Moderately-
disturbed
Least-disturbed
Streambed stability
<-3.01
-3.01 to-2.54
>2.54
Riparian disturbance
>1.57
1.43-1.57
<1.43
Habitat complexity
<0.152
0.152-0.278
>0.278
Riparian vegetation
<0.124
0.124-0.276
>0.276
79
-------
An Assessment of USEPA Region 8 Streams and Rivers
Physical habitat stressor assessments for perennial streams in the Cultivated
Plains region of North Dakota are shown in Figure 13. Approximately 2,148 kilometers
(55%) of streams were assessed in most-disturbed condition, while only 1,148 kilometers
(29%) of streams were assessed in least-disturbed condition for streambed stability.
Condition assessments based on riparian disturbance and riparian vegetation indicated
that perennial streams in the Cultivated Plains region were considered in least-disturbed
condition for 2,180 kilometers (55%) and 2,986 kilometers (76%), respectively. Only 77
kilometers (2%) of stream length was assessed in most-disturbed condition for riparian
vegetation. Habitat complexity was more evenly divided with 1,482 kilometers (38%) of
streams assessed in most-disturbed condition, 1,561 kilometers (40%) assessed in
moderately-disturbed condition, and 885 kilometers (22%) assessed in least-disturbed
condition.
Figure 13. Perennial stream length (km) in the Cultivated Plains region of North Dakota
that was assessed in least-disturbed (green), moderately-disturbed (yellow), and most-
disturbed (red) condition based on four physical habitat stressors.
8
C
C
CO -Q
1.1
500 1000 1500 2000
Stream length (km)
3000 3500 4000
Physical habitat stressor assessments for perennial streams in the Rangeland
Plains region are shown in Figure 14. Approximately 1,221 kilometers (46%) of streams
were assessed in least-disturbed condition and only 781 kilometers (30%) of streams
were assessed in most-disturbed condition for streambed stability. Assessments of
riparian disturbance and riparian vegetation stressors indicated streams were considered
in least-disturbed condition for 1,427 kilometers (54%) and 898 kilometers (34%) of
stream length, respectively. The habitat complexity stressor assessment indicated that
1,773 kilometers (68%) of stream length were considered in most-disturbed condition.
80
-------
An Assessment of USEPA Region 8 Streams and Rivers
The riparian vegetation stressor assessment showed the greatest difference
between the Rangeland Plains and Cultivated Plains regions. Approximately 76% of the
assessed streams in the Cultivated Plains region were considered to be in least-disturbed
condition while only about 34% of the streams assessed in the Rangeland Plains region
were considered to be in least-disturbed condition. Because livestock grazing is more
dominant in the Rangeland Plains region than in the Cultivated Plains region, it is likely
that over-grazing by livestock in the Rangeland Plains region may be degrading riparian
vegetation.
The physical habitat stressor assessment for North Dakota as a whole reflects the
summation of the assessments for the Cultivated Plains and Rangeland Plains regions
(Figure 15). Approximately 2,369 kilometers (36%) of streams were assessed in least-
disturbed condition, while 2,929 kilometers (45%) of streams were assessed in most-
disturbed condition for streambed stability. Assessments of riparian disturbance and
riparian vegetation stressors indicated streams were considered in least-disturbed
condition for 3,607 kilometers (55%) and 3,884 kilometers (59%) of stream length,
respectively. The habitat complexity stressor assessment indicated that 3,255 kilometers
(50%) of stream length were considered in most-disturbed condition.
1000 1500 2000 2500 3000 3500 4000
Stream length (km)
I
Figure 14. Perennial stream length (km) in the Rangeland Plains of North Dakota that
was assessed in least-disturbed (green), moderately-disturbed (yellow), and most-
disturbed (red) condition based on four physical habitat constituents.
81
-------
An Assessment of USEPA Region 8 Streams and Rivers
i* L
•c E
CO .2
5 E
CO o
X O
ft
cc >
H 1 1
Ji—
¦¦¦¦¦¦¦¦¦
Bin
¦H
H
K-
F
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Stream length (km)
Figure 15. Perennial stream length in North Dakota as a whole that was assessed in least-
disturbed (green), moderately-disturbed (yellow), and most-disturbed (red) condition
based on four physical habitat constituents.
Conclusions
The Environmental Monitoring and Assessment Program (EMAP)-West was
initiated in North Dakota in 2000 by the U.S. Environmental Protection Agency
(USEPA) in cooperation with the U.S. Geological Survey (USGS) and the North Dakota
Department of Health (NDDH) to develop and demonstrate monitoring tools that would
be used to produce unbiased estimates of ecological condition in surface waters of the
State. Probability and hand-picked sampling sites were selected in order to develop
indicators and derive threshold values for estimating stream condition.
A total of 111 sites were selected and sampled in North Dakota (Figure 2). Forty-
one (41) probability sites and 27 hand-picked sites were selected in the Cultivated Plains
region, and 23 probability sites and 20 hand-picked sites were selected in the Rangeland
Plains region. A cumulative total of the probability sites estimate there are 6,900
perennial stream kilometers within the State.
Based on the macroinvertebrate indicator, the multi-metric index (MMI)
developed for this assessment shows the condition class estimates for the State of North
Dakota are 3,141 (48%) stream kilometers in least-disturbed condition, 1,602 (24%)
stream kilometers in moderately-disturbed condition and 1,813 (28%) stream kilometers
estimated to be in most-disturbed condition (Figure 3).
82
-------
An Assessment of USEPA Region 8 Streams and Rivers
The vertebrate MMI developed by the US EPA for the entire plains region of the
U.S. was applied to North Dakota, the vertebrate MMI only performed well in the
Cultivated Plains. In this region, only 709 (20%) stream kilometers are considered to be
in least-disturbed condition while 1,192 (33%) stream kilometers are in moderately-
disturbed condition and 1,690 (47%) stream kilometers are estimated to be in most-
disturbed condition (Figure 4). In the Rangeland Plains region of North Dakota, the MMI
performed poorly and condition class estimates are not reported.
According to the periphyton indicator, the MMI revealed estimates of 2,305
(35%) stream kilometers in least-disturbed condition, 1,665 (25%) stream kilometers in
moderately-disturbed condition and 1,665 (25%) stream kilometers in most-disturbed
condition (Figure 8).
Based on the chemical stressor assessment for the State of North Dakota, 2,866
(43%) stream kilometers are in least-disturbed condition with regards to total phosphorus
while 1,040 (16%) stream kilometers are in moderately-disturbed condition and 2,677
(41%) stream kilometers are in most-disturbed condition. Based on total nitrogen, 5,866
(89%) stream kilometers are in least-disturbed to moderately-disturbed condition while
only 717 (11%) stream kilometers are estimated to be in most-disturbed condition.
According to the specific conductance constituent, 1,573 (24%) stream kilometers are in
most-disturbed condition while 5,010 (76%) stream kilometers are in moderately-
disturbed to least-disturbed condition (Figure 11).
According to the mercury in fish tissue constituent, 3,457 (56%) perennial stream
kilometers in the State are estimated to be in most-disturbed condition (mercury
concentrations >0.1 |ig/g) while 1,830 (30%) stream kilometers are in least-disturbed
condition. A total of 829 stream kilometers lacked fish for the analysis and, therefore,
were not assessed (Figure 12).
Physical habitat stressor assessments revealed that approximately 2,369 (36%)
stream kilometers are in least-disturbed condition based on streambed stability while
2,929 (45%) stream kilometers are in most-disturbed condition. Riparian disturbance
assessments estimate that 3,607 (55%) stream kilometers are in least-disturbed condition
along with 3,884 (55%) stream kilometers based on riparian vegetation. Habitat
complexity indicated that 3,255 (50%) stream kilometers are in most-disturbed condition
(Figure 15).
In summary, biological indicators (macroinvertebrate and periphyton) generally
provided higher estimates of streams in least-disturbed to moderately-disturbed condition,
while physical habitat indicators (bed stability, riparian disturbance, habitat complexity)
provided higher estimates of streams in most-disturbed condition. Of the chemical
indicators, total phosphorus provided a higher estimate of streams in most-disturbed
condition (41%) compared to total nitrogen (89%) and conductivity (76%) which
estimated a higher percentage of streams in least-disturbed to moderately-disturbed
condition. These results suggest the need to develop and implement multiple indicators
(biological, chemical and physical) for accurate water resource assessment.
83
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of South Dakota
Physical Setting
The State of South Dakota is 199,730 square kilometers in area and contains
portions of eight Level III Ecoregions. These are the Middle Rockies (17) (Black Hills),
Northwestern Great Plains (43), Northwestern Glaciated Plains (42), Northern Glaciated
Plains (46), and small portions of the Western Corn Belt Plains (47), Lake Agassiz Plain
(48), the Nebraska Sand Hills (44), and the Western High Plains (25) (Omernik 1987).
The Black Hills in western South Dakota (and northeastern Wyoming) is in the
easternmost portion of the Middle Rockies Ecoregion (17). This area contains the highest
elevation in the State and is heavily forested. The Northwestern Great Plains (43) is a
great expanse of rolling prairie lands extending from western South Dakota, southwestern
North Dakota, northeastern Wyoming and much of eastern Montana. The Northwestern
Great Plains covers most of the western half of South Dakota, except for the Black Hills
in the southwest corner of the State.
The Northwestern Glaciated Plains (42) is a relatively narrow band of grassland
east and north of the Northwestern Great Plains. It has a high concentration of prairie
potholes. With such poor drainage, the number of streams is limited, especially in the
South Dakota portion of the Northwestern Glaciated Plains. Very few sites were sampled
in this ecoregion because of the paucity of flowing water. The Northern Glaciated Plains
Ecoregion (46) is a flat to gently rolling landscape composed of glacial till (Omernik
1987). The original vegetation was grassland containing both tallgrass and shortgrass
prairie. There are high concentrations of temporary and seasonal wetlands in this
ecoregion.
Precipitation ranges from more than 30 inches (76 cm) annually in the central
Black Hills to 15-20 inches (38-50 cm) in the western and central portions of the State to
more than 20 (50 cm) in the southeast. Elevation ranges from more than 7000 feet (2130
meters) at the highest point in the Black Hills to around 1100 feet (335 meters) in
southeastern South Dakota. Major rivers in South Dakota include the Missouri,
Cheyenne, Belle Fourche, James, and Big Sioux.
Human Influence
Prior to human settlement, the vegetation of eastern South Dakota was primarily
prairie grasses, with gallery forests along streams. The lands are now rich in agricultural
production and most of the prairie has been converted to row crops. Western South
Dakota is mainly grassland where grazing is the predominant land use, with the exception
of the Black Hills where logging, mining, and tourism are important industries.
The population of South Dakota is 781,919 (US Census Bureau 2006). Major
population centers include Sioux Falls, Rapid City, Aberdeen, Brookings, Mitchell,
Pierre, and Watertown. Aside from impacts from the larger cities and towns, the greatest
84
-------
An Assessment of USEPA Region 8 Streams and Rivers
impact to streams occurs from agricultural production, including the impacts of row
crops, grazing, and livestock feeding operations. Such land use can introduce excess
nutrients and sediment to streams, with row crop agriculture potentially adding pesticides
and their degradation products. In the Black Hills, potential impacts are from mining,
logging and residential development. Figure 1 depicts the land cover for South Dakota.
The dominance of agricultural land is obvious in the eastern third of the State while
grassland dominates the western two-thirds. The forested Black Hills are in the
southwest. The larger cities, such as Rapid City and Sioux Falls are in red.
W6ter Shrub land
Urban HI Grassland
Barren Cropland
Forest Wbtland
kilometers
ngure 1. Land cover of the State of South Dakota.
Extent of Streams
A total of 143 sites were sampled in South Dakota (81 probability sites and 62
"hand-picked" as potential reference sites). Seventy-six probability sites were used in the
Final assessment. Approximately 14,121 (+/- 2,122) kilometers of perennial streams are
contained within the State according to the EMAP-West evaluation; the 76 sites used for
assessment represent 13,073 (+/- 1,530) kilometers. No sites were physically inaccessible
and 8 sites, representing 1,050 km, were denied access by landowners. About 2,465
stream kilometers were considered non-target (either dry or found to contain
impoundments). The sampled sites in South Dakota are presented in Figure 2.
85
-------
An Assessment of USEPA Region 8 Streams and Rivers
SOUTH DAKOTA
• Probability Sites
: Hand-Picked Sites
Rangeland Rains
1 . . : Cultivated Plains
H Back Hills
100
200
Figure 2. Location of sampled sites in South Dakota (black dots represent probability
sites and blue dots are hand-picked sites.
Stream Length by Ecoregion Combination
Rangeland
Plains
Cultivated
Plains
Black Hills
HB
.
(
) 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Stream Length (km)
Figure 3. South Dakota assessed stream length.
86
-------
An Assessment of USEPA Region 8 Streams and Rivers
Reference Site Determination
Development of biological indicators and threshold values of condition are
dependent upon using reference and stressed sites to represent the range of biotic
condition. As mentioned in the reference site discussion in the introduction of this report,
reference sites are considered to be the least-disturbed sites for a given ecoregion, not
necessarily pristine or completely without human influence.
The original designation for least-disturbed and stressed sites completed by EPA-
ORD (Stoddard et al 2005a) was revised by state agency staff using local knowledge, and
in some cases, local methods. The process used to designate least-disturbed and stressed
South Dakota sites (plains only) involved a method similar to MMI development. First, a
set of landscape, habitat, and chemistry metrics were selected. Then, metrics were
compared to one another in a correlation matrix, and redundant metrics (those with a
correlation greater than 0.7) were removed. Metrics were standardized, scored on a scale
from 0 to 100, and combined into a composite metric score. The top 10 percent of scores
were designated as least-disturbed and the bottom 10 percent were designated stressed for
each ecoregion. A limitation to this approach is that only 20% of the sites in each
ecoregion will be classified. As a result, some least-disturbed or stressed sites could be
missed. To correct that limitation, adjustments were made in site designations. For
example, if the score for site was outside the boundary for being designated as a stressed
site, but the field sheet comments strongly suggested the site was stressed, the site was
designated as "stressed". A designation of "stressed" or least-disturbed was also given to
a site if the EPA-ORD designation and the field sheets agreed but South Dakota specific
method was inconclusive. In the Black Hills, the EPA-ORD designations were used with
some changes recommended by the State of South Dakota.
Least-disturbed sites in the plains ecoregions were found in watersheds where
agriculture was present, but not strongly impacting the stream. A watershed can have a
significant amount of cropland and still retain high quality streams if riparian areas are
intact. The least-disturbed sites in South Dakota were predominantly from the first to
fourth stream orders. Least-disturbed sites were most common in the northeast, extreme
south, and the Black Hills. Stressed sites were fairly well distributed throughout the State,
but few least-disturbed sites were found in the central portions of South Dakpta.
Biotic Indicators
Several macroinvertebrate MMIs were developed specific to the ecoregions of
South Dakota. Level III Ecoregions were combined into larger groupings extending from
South Dakota into North Dakota and parts of Montana. These larger groupings of
ecoregions allowed creation of a sufficient sample size for metric development and
analysis. The original EPA-ORD plains macroinvertebrate MMI (Stoddard et al 2005b)
did not perform as well at smaller geographic scales. Therefore, separate MMIs were
developed for the Northern Cultivated Plains Ecoregion combination (Ecoregions 46, 47,
and 48) and for the Northern Rangeland Plains Ecoregion combination (Ecoregions 42,
43, and 44). For the relatively few sites in the Black Hills the original EPA-ORD western
87
-------
An Assessment of USEPA Region 8 Streams and Rivers
mountains MMI was used. See the EMAP-West Report for more information on how that
MMI was developed (Stoddard et al 2005b).
The procedure to develop the two plains macroinvertebrate MMIs followed that
outlined in the EMAP-West Statistical Summary (Stoddard et al 2005a), but because it
was performed at a lower regional scale, different results were obtained. This is not
unexpected since generally, the smaller the scale the less variability in the landscape. For
both the Northern Cultivated and Northern Rangeland Plains MMI development, the
datasets were separated into calibration and validation sets. The first step in the analysis
was to compare individual metrics between least-disturbed and stressed sites and
determine metrics that were responsive to the range of site quality.
Metrics were compared to one another in a correlation matrix to determine which
metrics were not independent. An MMI was created using the most strongly responsive,
non-redundant metrics. Additionally, an attempt was made to include as many of the
metric categories (richness, composition, diversity, tolerance, feeding, and habit) as
possible.
The final MMI for the Northern Cultivated Plains region consisted of 6 metrics,
listed in Table 1 (one composition metric, two tolerance metrics, two feeding group
metrics, and one habit metric). These metrics were scored from 0 to 100 based on the
range of the dataset, with the six values averaged for the final metric score.
The final Northern Rangeland Plains region macroinvertebrate MMI consisted of
six metrics (Table 1) and included one richness metric, two tolerance metrics, two
feeding group metrics, and one habit metric. These metrics were also scored from 0 to
100 based on the range of the dataset, with the six values averaged for the final score.
The Black Hills MMI metrics are from Stoddard et al (2005a).
Table 1. Macroinvertebrate MMI metrics.
Bioregion
Metric
Category
Cultivated
Plains
Percent EPT Taxa
Composition
Percent Predator Individuals
Feeding
Percent Individuals Rated 8 or 9 on Tolerance Scale
Tolerance
Percent Individuals Rated 6 or 7 on Tolerance Scale
Tolerance
Percent Clinger Taxa
Habit
Percent Collector-Filterer Individuals
Feeding
Rangeland
Plains
EPT Richness
Richness
Percent Clinger Individuals
Habit
Percent Collector-Gatherer Individuals
Feeding
Percent Predator Taxa
Feeding
Percent Taxa Rated 0 to 5 on Tolerance Scale
Tolerance
Percent Individuals Rated 8 or 9 on Tolerance Scale
Tolerance
88
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 1 (cont.) Macroinvertebrate MMI metrics.
Bioregion
Metric
Category
Percent Nonlnsect Individuals
Composition
Percent Dominant 5 Taxa
Diversity
Black Hills
Percent Omnivore Taxa
Feeding
Percent Burrower Individuals
Habit
EPT Richness
Richness
Percent Tolerant Taxa
Tolerance
Development of a periphyton MMI for both the Northern Cultivated Plains and
the Northern Rangeland Plains also followed the outline of MMI development presented
in the EMAP-West Report (Stoddard et al 2005b). Boxplots of least-disturbed and most-
disturbed sites were compared and the best non-redundant metrics were selected, also
attempting to obtain as much representation in the metric categories as possible. The
periphyton metrics for the Northern Rangeland Plains MMI and Northern Cultivated
Plains MMI are listed in Table 2. The Black Hills were not assessed using periphyton
because the Black Hills periphyton metrics appeared to respond differently from the
periphyton metrics of the larger Middle Rockies Ecoregion and there was an insufficient
number of sites to develop an MMI specific to the Black Hills.
Table 2. Periphyton MMI metrics.
Bioregion
Metric
Category
Cultivated
Plains
Gomphonema species richness
Richness
Percent Fragilaria (sensu lato, or "old" taxonomic
classification) individuals
Composition
Cymbella (sensu lato, or "old" taxonomic classification)
richness
Richness
Percent Highly Motile Taxa
Morphology
Percent Taxa in Oxygen Classes 1 and 2
Tolerance
Rangeland
Plains
Percent Taxa in Cymbella (sensu lato, or "old" taxonomic
classification)
Composition
Percent Taxa in Fragilaria (sensu lato, or "old"
taxonomic classification)
Composition
Percent Individuals in Nitzschia (sensu stricto, or
"new" taxonomic classification)
Composition
Percent Moderately and Highly Motile Taxa
Morphology
Percent Taxa in Oxygen Classes 1 and 2
Tolerance
A fish MMI was not used for the State of South Dakota since the fish metrics did
not discriminate between least- and most-disturbed sites in the rangeland plains area.
Although the fish MMI created for the plains in the EMAP-West report (Stoddard et al
2005b) was responsive in the eastern portions of the State, the western South Dakota fish
metrics were not responsive. Because the MMI could only be based on half of the State,
we determined that a fish indicator was not appropriate for this assessment unit.
89
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Indicators
Stressors analyzed in this assessment included three water chemistry parameters
(total phosphorus, total nitrogen, and fish tissue mercury), four habitat measures
(streambed stability, riparian vegetation, riparian disturbance, and habitat complexity),
and two biological stresses (invasive plants and alien vertebrates). It is expected that all
of these measures provide an indication of human influence on streams, and may directly,
or indirectly, impact biological indicators.
Setting Expectations
Thresholds of condition for three classes (least-disturbed, moderately-disturbed,
and most-disturbed) were set for each biological or stressor indicator using reference
(least-disturbed) sites chosen for comparison to the entire population. Different sets of
least-disturbed sites were used depending on the indicator/stressor to assess. Biotic
condition was assessed using sets of least-disturbed sites chosen through the reference
site method discussed above.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites with various chemical and habitat parameters excluding the stressor
to be assessed to avoid circularity. Therefore, there is a different set of least-disturbed
sites for each stressor. There is more information on reference determination in the
Introduction to this Assessment.
If the confidence in the least-disturbed set of sites chosen for a particular indicator
was fairly high, then thresholds were set at greater than the 25th percentile of least-
disturbed sites for least-disturbed condition and less than the 5th percentile of least-
disturbed sites for most-disturbed condition. When there was somewhat less confidence
in the least-disturbed sites for an area for a particular indicator (due to screening without
important parameters), then the thresholds were raised to the median and the 25th
percentile of least-disturbed sites as equal to thresholds for least-disturbed and most-
disturbed, respectively. In the case of the macroinvertebrate MMI for the Northern
Rangeland Plains (western South Dakota), the thresholds were set at the 25th percentile
for least-disturbed and the 10th percentile as the dividing line between moderate and
most-disturbed (and only sites from the western Dakotas were used, even though
development of the MMI included sites in Montana and Wyoming). These were also the
thresholds used for the periphyton MMIs. Tables 3, 4, and 5 below describe what
thresholds were used for a given indicator or stressor.
90
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 3. Northern Cultivated Plains thresholds.
Northern Cultivated
Plains
Most-disturbed
Least-disturbed
Threshold
%
Threshold
%
Macroinvertebrate MMI
<49.4
5th
>55.7
25th
Periphyton MMI
<21.4
10th
>44.1
25th
Phosphorus
>312 ng/L
95th
<228 |jg/L
75th
Nitrogen
>2501 Mg/L
95th
<1525 pg/L
75th
Riparian Disturbance
>1.8
75th
<1.31
50th
Habitat Complexity
<0.136
25th
>0.214
50th
Streambed Stability
<-2.58
25th
>-2.20
50th
Riparian Vegetation
<0.041
25 th
>0.236
50th
Fish Tissue Mercury
>0.1 ng/g
<0.1 ng/g
Non-native Vertebrates
>10% of
individuals
Absent
Table 4. Northern Rangeland Plains thresholds.
Northern Rangeland
Plains
Most-disturbed
Least-disturbed
Threshold
%
Threshold
%
Macroinvertebrate MMI
<22.5
10th of
Western
Dakotas
>38.2
25th of
Western
Dakotas
Periphyton MMI
<32.3
10th of
Sites in SD
only
>42.5
25th of
Sites in SD
only
Phosphorus
>138 ng/L
95th
<70 |jg/L
75th
Nitrogen
>1186 Mg/L
95th
<886 |ig/L
75th
Riparian Disturbance
>1.57
75th
<1.43
50th
Habitat Complexity
<0.152
25th
>0.278
50th
Streambed Stability
<-3.01
25th
>-2.54
50th
Riparian Vegetation
<0.124
25th
>0.276
50th
Fish Tissue Mercury
>0.1 |ig/g
<0.1 pg/g
Non-native Vertebrates
>10% of
individuals
Absent
91
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 5. Black Hills thresholds.
Black Hills
Most-disturbed
Least-disturbed
Threshold
%
Threshold
%
Macroinvertebrate MMI
<43.6
5 th
>62.5
25th
Periphyton MMI
none
none
Phosphorus
>73 mb/L
95th
<26 (Jg/L
75th
Nitrogen
>135 jjg/L
95th
<209 |ig/L
75th
Riparian Disturbance
>1.71
95th
<0.64
75th
Habitat Complexity
<0.168
5th
>0.368
25th
Streambed Stability
<-1.69
5th
>-1.16
25th
Riparian Vegetation
<0.30
5th
>0.49
25th
Fish Tissue Mercury
>0.1 |ig/g
<0.1 ng/g
Non-native Vertebrates
>10% of
individuals
Absent
Biological Condition
Using macroinvertebrate MMIs developed for the Northern Cultivated Plains, the
Northern Rangeland Plains, and the Western Mountains (for the Black Hills), about 6,477
km (50%) of stream length was in least-disturbed condition, 1,383 km (10%) moderately-
disturbed, and 4,774 km (37%) most-disturbed, with a little over 3% unassessed. The
periphyton MMIs developed for the plains found less in least-disturbed condition - about
4,132 km (32%). It found a similar amount in most-disturbed condition, however, at
5,426 km (41%). About 8% of stream length was unassessed using periphyton. Figure 3
presents the amount of stream length by condition class for macroinvertebrates and
periphyton.
92
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
0 1000 2000 3000 4000 5000 6000 7000 8000
Stream Length (km)
Figure 3. Biological condition based on macroinvertebrate and periphyton MMIs (green
represents least-disturbed, yellow represents moderately-disturbed, red is most-disturbed,
and gray is not assessed).
Indicators of Stress
Stream length in most-disturbed condition for total phosphorus was 5,970 km,
with 4,985 km least-disturbed (Figure 4). Only 3,421 km of stream length was in most-
disturbed condition for total nitrogen and a similar amount of 4,347 km in least-disturbed
condition. Mercury in fish tissue (all fish samples, regardless of size) at levels greater
than 0.1 pg/g (Lazorchak et al 2003) were found in 4,026 km of stream length, lower than
this level in 5,200 km. About 3,850 km of stream length were not assessed using fish
tissue mercury.
Least disturbance to riparian areas was found in 5,140 km of stream length in
South Dakota and 4,121 km most-disturbed. For riparian vegetation cover, 5,238 km was
least-disturbed and 5,663 km was most-disturbed. Habitat complexity was in least-
disturbed condition in 3,711 km of stream length and 5,778 most-disturbed. The
streambed stability indicator found 6,795 km in least-disturbed condition, 1,566 km
moderate, and 3,953 most-disturbed (a little less than 6% could not be assessed).
Figure 4 presents the amount of stream length in the various condition classes for
stressors. Total phosphorus, poor habitat complexity, and poor riparian vegetation cover
affected the most stream length at more than 5,500 km each. However, fish tissue
93
-------
An Assessment of USEPA Region 8 Streams and Rivers
mercury, along with streambed stability and riparian disturbance, all had around 4,000
km of stream length in the most-disturbed condition.
Stressor Extent
Phosphorus
Nilrogen
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
1000 2000 3000 4000 5000 6000 7000 8000 9000
Stream Length (km)
Figure 4. Extent of stressors in least- (green), moderate- (yellow), and most-disturbed
(red) condition (gray is not assessed).
Two biological stressors were measured in this study, but not presented on the
chart. These were the presence of alien vertebrates (mainly fish) and invasive plants. The
EMAP-West Report (Stoddard et al 2005b) derived thresholds for non-native vertebrates,
which were: if more than 10% of the vertebrate individuals captured at a site were non-
native they were listed as common, more than 0% but less than 10% was considered
"present" and if none were found they were absent. In South Dakota, non-native fish
were common in 4,764 km of stream length, present in 3,605 km, and absent in 4,484 km.
Twelve invasive plants were also noted for presence throughout the full EMAP-
West study area. Of those 12, common invasive plants found in South Dakota were
common burdock (Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus
nutans), Canada thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian
olive (Elaeagnus angustifolia), leafy spurge (Euphorbia esula), and reed canary grass
(.Phalaris arundinacea). As a group, invasive plants were either common or dominant
(found at more than 10% of transects) in about 85% of stream length where sampled and
absent in less than 12%. Invasive plants were assessed in 10,733 stream kilometers (out
of the total of 13,073).
94
-------
An Assessment of USEPA Region 8 Streams and Rivers
Conclusions
The results of analysis of two bioindicators resulted in similar amounts of stream
length in most-disturbed condition (around 5,000 km of stream length), but the amount of
least-disturbed stream length differed. According to the macroinvertebrate MMI, 6,000 km of
stream length was in least-disturbed condition. According to the periphyton MMI, 4,000 km
was in least-disturbed condition (more was in the moderate category for periphyton as
compared to macroinvertebrates). The difference in response of bioindicators underscores the
need for using more than one bioindicator and comparing the results to determine impacts.
High concentrations of phosphorus, reduction in habitat complexity and disturbance
to riparian vegetation impacts between 5,500 and 6,000 km of stream length. Phosphorus,
habitat complexity and riparian vegetation were the greatest cause of impacts to streams. The
other stressors, however, were not far behind at around 4,000 km most-disturbed.
Recommendations / Data and Information Gaps
A RIVPACS predictive model (see Ecological Indicators in the introduction of this
report) would add valuable biological information and complement the macroinvertebrate
MMIs and the development of such a model for South Dakota would be valuable. As with
development of MMIs, finding appropriate least-disturbed or reference sites is one of the
greatest challenges in plains streams. The impacts to streams are likely underestimated
because of the limited number and quality of least-disturbed sites. Continued effort to
improve bioindicators and to find both more and better quality reference sites is necessary.
More sites overall would lead to better understanding of the extent of stressors and their
relative risk, something that could not be done at this level in this study. The stressors and
bioindicators probably differ significantly between eastern and western South Dakota - more
sites in each of these areas would lead to a better understanding of the condition and stressors
in each.
More work should be done to determine differences in bioindicators with respect to
stream size. This study combined small streams and larger rivers. Bioindicators developed
separately or with these differences in mind would lead to a better assessment.
A continued focus on nutrients is worthwhile, but riparian and direct stream impacts
are also important. All of the stressors in the study found a large amount of stream length in
most-disturbed condition. Breaking this down into ecoregions may tease out what stressors
are more important in different landscapes (grazing land versus row crops).
Nearly 4,000 km of streams were not assessed for fish tissue mercury. Since more
than 4,000 km of stream length was found to be over the 0.1 jag/g threshold, more
investigation into the extent of fish tissue mercury contamination would be worthwhile, even
though these do not necessarily correspond to a human health concern (samples were whole
fish not filets, and some were not fish of interest for human consumption).
95
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of Utah
Physical Setting
The State of Utah covers 219,900 square kilometers and contains portions of
seven Level III Ecoregions (Omemik 1987). These are the Wasatch and Uinta Mountains,
the Colorado Plateau, the Central Basin and Range, and small portions of the Southern
Rockies, the Northern Basin and Range, the Mojave Basin and Range, and the Wyoming
Basin.
Covering the highest elevations from the northeast and extending down the center
of the State are the Wasatch and Uinta Mountains (Ecoregion 19). A majority of the
perennial stream length is located in this ecoregion. The ecoregion (Omemik 1987) is
composed of high, precipitous mountains with narrow crests and valleys. The vegetation
pattern is similar to the Southern Rockies, except that aspen, and pinyon-juniper, and oak
are more common at middle elevations. Lodgepole pine is not as extensive as in the
Southern Rockies and the vegetation supports more livestock in the summer months than
in the Middle Rockies to the north.
The Colorado Plateau covers most of the eastern and southeastern portion of Utah
and contains the dramatic sandstone canyonlands landscape (Ecoregion 20). A very small
portion of Ecoregion 18, the Wyoming Basin, is located in the far northeast part of Utah.
A few small mountain ranges considered to be part of the Southern Rockies (21)
intersperses this ecoregion not far from the Colorado state boundary. Large rivers (Green,
Colorado, and San Juan) drain the arid ecoregion. Erosion by water and wind has created
a geomorphology of abrupt changes in local relief, with rugged tablelands and steep sided
waits (Omernik 1987). Pinyon-juniper woodland dominates the vegetation, with saltbrush
and greasewood in the low lying areas.
The Central Basin and Range Ecoregion (13), is located in the western desert,
along with smaller parts of the Mojave Basin and Range (14) in the southwest and the
Northern Basin and Range (80) in the northwest. The Sevier River enters this ecoregion
from the mountains and ends in a terminal lake. The Central Basin and Range Ecoregion
is internally drained and is characterized by a mosaic of xeric basins, scattered low and
high mountains, and salt flats (Omernik 1987). Basins are covered by Great Basin
sagebrush or saltbush-greasewood vegetation. The small amount of Utah in the Mojave
Basin and Range is generally lower in elevation than the Central Basin and Range and
has predominantly creosote bush as a natural vegetation cover.
Elevation ranges from 2,350 feet (716 meters) at Beaver Dam Wash near St.
George to 13,528 feet (4123 meters) at Kings Peak in the Uinta Mountains. Precipitation
reaches a low of around 8 inches (20 cm) annually in the Colorado Plateau, Uinta Basin,
and extreme southwestern Utah to a high of 50 to 60 inches (125-150 cm) per year in the
northern Wasatch Mountains. Major rivers in Utah include the Green, Colorado, San
Juan, Bear, Jordan, and Sevier.
96
-------
An Assessment of USEPA Region 8 Streams and Rivers
Human Influence
According to the 2007 census estimate, the population of Utah is 2,645,330 (US
Census Bureau 2007). Most of the population of Utah resides along the Wasatch Front,
which includes the cities of Salt Lake City (Salt Lake County's population is 979,000),
Provo (105,000), Orem (84,000), Logan (43,000), and Ogden (77,000). Outside of the
Wasatch Front, the largest city is St. George at nearly 50,000 people.
Aside from impacts from the larger cities, the greatest impact to streams occurs
from agricultural production (mainly irrigated) and grazing. Both can introduce excess
nutrients and sediment to streams, with irrigated crop agriculture potentially adding
pesticides, selenium and salinity. In the mountains, there are potential impacts from
mining, logging and development. Figure 1 represents the land cover for Utah. The
dominance of larger cities is obvious but localized (red). Agricultural land is limited in
area, with most of Utah dominated by forest and shrubland.
Kilometers
| Water
j Shrubland
¦ Urban
^ Grassland
Barren
Cropland
| Forest
Wetland
^igure 1. Land cover of the State of Utah.
97
-------
An Assessment oi USEPA Region 3 Streams and Rivers
Extent of Streams
A total of 127 sites were sampled in Utah (55 probability sites and 72 "hand-
picked" as potential reference sites). All 55 probability sites were used in the final
assessment. Approximately 13,782 (+/- 3,502) kilometers of perennial streams are
contained within the State according to the EMAP-West evaluation; the 55 sites used for
assessment represent 12,091 (+/- 2,287) kilometers. Five sites were physically
inaccessible (representing 1,494 km) and only 1 site was denied access by landowners.
About 14,460 stream kilometers were considered non-target (either dry or found to
contain impoundments). The sampled sites in Utah are presented in Figure 2 and the
stream length assessed by ecoregion combination is represented in Figure 3.
UTAH
• Probability Sites
• Hand-Picked Sites
] vvfest Desert
¦ Mountains
Colorado Plateau /
' Wyoming Basin
Figure 2. Location of sampled sites in Utah (black dots represent
probability sites and blue are hand-picked sites).
| - -V
~ • «
..V
• # P
* «
. | -
50 100 200
Wlo meters
98
-------
An Assessment of USEPA Region 8 Streams and Rivers
Assessed Stream Length by Ecoregion Combination
Mountains
CO Plateau
West Desert
1 -
0
1000
2000
3000
Stream Length (km)
4000
5000
6000
figure 3. Assessed stream length in Utah by ecoregion combination.
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
site discussion in the introduction of this report, reference sites are considered to be the
least disturbed sites for a given ecoregion.
The original designation for least disturbed and stressed sites performed by EPA-
ORD (Stoddard et al 2005a) was revised by each state using local knowledge, and in
some cases, locally determined methods. Representatives from EPA Region 8 and Utah
Department of Environmental Quality met and reassessed each site for reference
characteristics and made revisions to the original designation. Additional reference sites
were used from neighboring Colorado for periphyton MMI development.
Biotic Indicators
Utah's RIVPACS is a statewide macroinvertebrate-based predictive model that
provides an assessment of biological condition by comparing the macroinvertebrate taxa
observed at a site of unknown biological condition with the macroinvertebrate taxa
expected to occur in the absence of human-caused stress (Utah DEQ 2008). The expected
macroinvertebrate taxa are derived from an appropriate set of reference sites that are
minimally or least-impacted by anthropogenic stress. The reference sites are classified
into groups of similar taxonomic composition and then models are developed with
watershed descriptors (i.e., climatic setting, soil characteristics, stream size) to generate
equations that ultimately allow for predicting the probability that a new site falls within
each group of reference sites (Utah DEQ 2008). Predictor variables used in the Utah
99
-------
An Assessment of USEPA Region 8 Streams and Rivers
model included such parameters as elevation, slope, geology, soils, precipitation, dates of
first and last freeze, and temperature. The deviation of the observed from the expected
taxa, known as the O/E value, is a measure of the compositional similarity expressed in
units of taxa richness and thus a community level measure of biological condition. O/E
values near 1 imply high biological condition while values < 1 imply some degree of
biological degradation. Much more information on the development of this predictive
model is available in Utah DEQ (2008).
Development of a periphyton MMI for Utah followed the outline of MMI
development presented in the EMAP-West Report (Stoddard et al 2005b). An MMI was
only developed for the mountainous regions of Utah; the xeric regions will need more
reference sites and analysis in order to develop robust indicators. Boxplots of least-
disturbed and most-disturbed sites were compared and the best non-redundant metrics
were selected, also attempting to obtain as much representation in the metric categories as
possible. The periphyton metrics for the Utah mountain region are listed in Table 1.
Table 1. Periphyton MMI metrics.
Bioregion
Metric
Category
Utah
Mountains
Navicula (sensu stricto, or "new" taxonomic
classification) Percent Individuals
Composition
Percent Fragilaria (sensu lato, or "old" taxonomic
classification) Richness
Richness
Percent Highly Motile Taxa
Morphology
Percent Taxa in Oxygen Class 1
Tolerance
A fish MMI was not used for the State of Utah due to fish collection issues, low
species diversity, and a greater interest in pursuing other biological indicators. A
macroinvertebrate MMI was previously developed and applied to sites in Utah as a result
of the EMAP west-wide assessment (Stoddard et al 2005b). While these MMI scores
were used for the full EPA Region 8 assessment, it was decided that they were not
appropriate to use at the scale of the State of Utah.
Stressor Indicators
Stressors analyzed in this assessment were two chemical (total phosphorus and
total nitrogen), four habitat (streambed stability, riparian vegetation, riparian disturbance,
and habitat complexity), and two biological (invasive plants and alien vertebrates). All of
these were measures that would give some indication of human influence to streams and
may directly or indirectly impact biological indicators. Fish tissue mercury is not reported
for Utah because more than half of the stream length was unassessed, mainly due to fish
collection restrictions.
Setting Expectations
Thresholds of condition for three classes (least-disturbed, moderately-disturbed,
and most-disturbed) were set for each biological or stressor indicator using reference
100
-------
An Assessment of USEPA Region 8 Streams and Rivers
(least-disturbed) sites chosen for comparison to the entire population. Different sets of
least-disturbed sites were used depending on the indicator/stressor to assess. Biotic
condition (for periphyton) was assessed using sets of least disturbed sites chosen through
the reference site method discussed above. Thresholds for the predictive model were
determined differently, using a value of 2 standard deviations of the model error, which
in this case equaled 0.26 (Utah DEQ 2008). Least-disturbed sites were those that had a
score of 0.74 or greater. The most-disturbed determination depended on the number of
samples at a site. If there were three or more scores for a site, then it would be classified
as most-disturbed if the average was less than 0.74; if there were less than three scores,
then a score of less than 0.54 was needed to classify as most-disturbed. In the case of less
than three samples, any average score between 0.54 and 0.74 would be considered
undetermined. The 0.54 threshold was derived from year-to-year variability values.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites with various chemical and habitat parameters excluding the stressor
to be assessed to avoid circularity. Therefore, there is a different set of least-disturbed
sites for each stressor. For sites in Utah, stressor reference sites were screened separately
in the mountain ecoregions and the xeric ecoregions, so that differing thresholds were
derived in each area. There is more information on reference determination in the
Introduction to this Assessment.
If the confidence in the least-disturbed set of sites chosen for a particular indicator
was fairly high, then thresholds were set at greater than the 25th percentile of least-
disturbed sites for least-disturbed condition and less than the 5th percentile of least-
disturbed sites for most-disturbed condition. When there was somewhat less confidence
in the least-disturbed sites for an area for a particular indicator (due to screening sites
without important parameters), then the thresholds were raised slightly. For the Utah
assessment this was done for only one parameter (riparian disturbance). Thresholds used
for the periphyton MMI were the 5th and 25th as well. Thresholds used for a given
indicator or stressor are presented in Tables 2 and 3.
Table 2. Mountain region thresholds.
Mountain Regions
Most Disturbed
Least Disturbed
Threshold
%
Threshold
%
O/E*
<0.54
>0.74
Periphyton MMI
<42.1
5th
>59.6
25th
Phosphorus
>52 |ig/L
95th
<11 pg/L
75th
Nitrogen
>385 (ig/L
95th
<286 ng/L
75th
Riparian Disturbance
>1.0
90th
<0.89
75th
Habitat Complexity
<0.23
5th
>0.975
25th
Streambed Stability
<-0.80
5th
>-0.35
25th
Riparian Vegetation
<0.59
5th
>1.02
25th
Non-native Vertebrates
>10% of individuals
Absent
*See description of O/E thresholds in text.
101
-------
An Assessment of (JSEPA Region 8 Streams and Rivers
Table 3. Xeric region thresholds.
Xeric Regions
Most Disturbed
Least Disturbed
Threshold
%
Threshold
%
O/E*
<0.54
>0.74
Periphyton MMI
none
none
Phosphorus
>203 ng/L
95th
<40 |ig/L
75th
Nitrogen
>1181 ug/L
95th
<609 |ig/L
75th
Riparian Disturbance
>1.67
90th
<1.0
75th
Habitat Complexity
<0.17
5th
>0.47
25th
Streambed Stability
<-1.99
5th
>-1.62
25th
Riparian Vegetation
<0.36
5th
>0.69
25th
Non-native Vertebrates
>10% of individuals
Absent
*See description of O/E thresholds in text.
Biological Condition
Using the statewide predictive model, about 2,887 km (24%) of stream length was
in least-disturbed condition and 1761 km (15%) most-disturbed. However, more than
61% was unassessed. The periphyton MMIs found 1,765 km in least-disturbed condition
(about 15%). It found 2,843 km in most disturbed condition (23%) and 1096 km (9%) in
moderately-disturbed condition. About 53% of stream length (6,387 km) was unassessed
using periphyton, mostly due to the lack of an index covering the xeric regions of Utah.
The amount of stream length by condition class for macroinvertebrates and periphyton is
presented in Figure 4.
102
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
UJ
o
0)
TO
n
C
ai
>
c
o
—
o
>.
£
a.
a>
a.
24%
15%
61%
15%
9%
23%
53%
1000 2000 3000 4000 5000 6000
Stream Length (km)
7000
8000
9000
10000
-¦igure 4. Biological condition based on the macroinvertebrate predictive model and
periphyton MMI (red is most disturbed, yellow is moderately disturbed, green is least
disturbed, and gray is not assessed).
Indicators of Stress
Stream length in most-disturbed condition for total phosphorus was 2,970 km
(24%), with 4,796 km (40%) least-disturbed. A similar amount at 3,073 km (25%) of
stream length was in most-disturbed condition for total nitrogen, with 6,102 km (50%) in
least-disturbed condition.
Least-disturbance to riparian areas was found in 4,933 km of stream length in
Utah and 5,185 km most-disturbed. For riparian vegetation cover, 7,123 km was in least-
disturbed condition and 1,686 km most-disturbed, while habitat complexity was in least-
disturbed condition in 7,483 km of stream length and 1,249 most-disturbed. The
streambed stability indicator found 4,074 km in least-disturbed condition, 954 km
moderate, and 4,237 most-disturbed (about 23% was not assessed).
Figure 5 presents the amount of stream length in the various condition classes for
stressors (not including exotic fish or invasive plants). Human riparian disturbance and
streambed stability affected the most stream length at more than 4,000 km each.
However, both phosphorus and nitrogen were not far behind at around 3,000 km of
stream length each in most disturbed condition.
103
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Extent
Phosphorus
Nitrogen
Riparian Disturbance
Riparian Vegetation
Streambed Stability
Habitat Complexity
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 1 0000
Stream Length (km)
Figure 5. Extent of stressors in least, moderate, and most-disturbed condition (red is most
disturbed, yellow is moderately disturbed, green is least disturbed, and gray is not
assessed).
Two biological stressors were measured in this study, but not presented on the
chart. These were the presence of alien vertebrates (mainly fish) and invasive plants. The
EMAP-West Report (U.S. EPA 2005) derived thresholds for non-native vertebrates,
which were: if more than 10% of the vertebrate individuals captured at a site were non-
native they were listed as common, more than 0% but less than 10% was considered
"present" and if none were found they were absent. In Utah, non-native fish were
common in 4,379 km of stream length, present in 1,615 km, and absent in 2,213 km.
Only 9,364 km of stream length was assessed for introduced fish.
Twelve invasive plants were also noted for presence throughout the full EMAP-
West study area. Of those 12, common ones found in Utah were common burdock
(Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus nutans), Canada
thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian olive (Elaeagnus
angustifolia), leafy spurge (Euphorbia esula), and reed canary grass (Phalaris
arundinacea). These were either common (found at 10-50% of transects) or dominant
(found in more than 50% of transects) in about 52% of stream length where sampled and
absent in 47%. Invasive plants were assessed in 11,093 stream kilometers.
104
-------
An Assessment of USEPA Region 8 Streams and Rivers
Conclusions
The indicators found differing amounts of stream length in least- and most-
disturbed condition. The macroinvertebrate predictive model found 24% of stream length
in least-disturbed condition and 15% in most-disturbed. The periphyton MMI, however,
found only 15% in least-disturbed condition and 23% most-disturbed. While these
possibly are responding to different stressors, this has to be observed in light of the fact
that more than half the stream length in Utah could not be assessed with either indicator.
Until judgments can be made about the differences in the indicators, more stream length
should be assessed with both.
Riparian disturbance and streambed stability ranked as the top two stressors
impacting the most stream length in Utah, with both at more than 4000 km. Nutrients
were in the next tier, impacting approximately 3000 km.
Recommendations / Data and Information Gaps
Placing a high priority on increasing the stream length assessed with biological
indicators (macroinvertebrates and periphyton) will result in a more accurate
understanding of the biotic condition. In fact, the State of Utah has implemented such an
increase in assessment. The biological data at additional sites will allow an analysis of
relative risk of particular stressors impacting streams.
The more xeric regions of the State provided more challenges in the development
of biological indicators, especially for periphyton. Finding reference sites in the
mountains tends to be less difficult than in the Colorado Plateau and West Desert
Ecoregions. More reference sites sampled in those regions could greatly improve a
biological assessment program for the State.
105
-------
An Assessment of USEPA Region 8 Streams and Rivers
State of Wyoming
Physical Setting
The State of Wyoming covers 253,325 square kilometers and is home to approximately
515,004 people (U.S. Census Bureau 2006). The Stale serves as the headwaters of the
Yellowstone, Snake, Bighorn, Green, and Cheyenne Rivers. Within the State boundaries are
seven Level III Ecoregions (Omernik 1987): Western High Plains, Northwestern Great Plains,
Middle Rockies, Southern Rockies, Wyoming Basin, and very small portions of the Wasatch and
Uinta Mountains and Snake River Plain.
The Middle Rockies within Wyoming include the northwestern portion of the State and
the Yellowstone Plateau, the Absaroka, Wind River, and Wyoming Mountain Ranges, the
Bighorn Mountains in the north-central and the Black Hills in the northeast. The Southern
Rockies extend from the Colorado border to just south of Casper. The plains in the east are
divided into the Northwestern Great Plains (which cover eastern Montana and western North and
South Dakota) and the Western High Plains, which reach into Nebraska and eastern Colorado. A
large portion of the center of the State is covered by the Wyoming Basin.
Elevation in Wyoming ranges from 13,804 feet (4204 meters) at Gannett Peak in the
Wind River Range to 3,099 feet (945 meters) where the Belle Fourche River leaves the State.
Precipitation ranges from as little as 10 inches (25 cm) annually in the Wyoming basin to more
than 75 inches (190 cm) in the Teton Range. The elevation and precipitation regimes create a
great diversity of stream habitat within Wyoming.
Human Influence
Major population centers in Wyoming include Cheyenne (55,000), Casper (52,000),
Laramie (26,000), Gillette (24,000), Rock Springs (19,000), and Sheridan (16,000) (U.S. Census
Bureau 2006). Aside from impacts from the larger cities and towns, the greatest impact to
streams occurs from irrigated agricultural production, grazing, oil and gas extraction and some
mining and development. Statewide, grazing and oil and gas extraction are probably the greatest
stressors to aquatic resources in Wyoming, especially in basin areas.
Figure 1 represents the land cover of Wyoming. Areas of cropland cover the southeast,
with large expanses of grassland in the east and shrubland in central and western Wyoming,
interspersed with mountainous terrain and forestland.
106
-------
4/7 Assessment of USEPA Region 8 Streams and Rivers
WYOMING
Figure 1. Land cover in the State of Wyoming.
100
Kilometers
| Wfcter ] Shrubland
I Urban H Grassland
| Barren i ] Cropland
I Forest [ | Wfetland
Extent of Streams
A total of 127 sites were sampled in Wyoming (76 probability sites and 51 "hand-picked"
as potential reference sites). Seventy-four probability sites were used in the final assessment. In
Wyoming, 50,764 kilometers of stream are listed as perennial in the RF3 file. The non-target
portion in Wyoming was about 26 percent of the total stream length (either dry or not
representing a stream). Therefore, approximately 37,637 (+/- 7,514) kilometers of perennial
streams are contained within the State according to the EMAP-West evaluation; the 76 sites used
for assessment represent 33,147 (+/- 4,887) kilometers. The sites sampled in Wyoming are
represented in Figure 2. Five sites were physically inaccessible (representing about 800 miles)
and 13 sites, representing about 5,940 stream kilometers were denied access by landowners. The
proportion of stream length in the access denied and inaccessible categories was relatively small
for the State of Wyoming.
107
-------
An Assessment of USEPA Region 8 Streams and Rivers
WYOMING
• PROBABILITY SITES
• HAND-PICKED SITES
1 | PLAINS REGION
MOUNTAIN REGION
] XERIC REGION
Kilometers
Figure 2. Location of sampled sites in Wyoming (black dots represent probability sites and blue
dots are hand-picked sites).
The proportion of stream length in the target and other categories varied between climatic
regions. In Wyoming, proportions of non-target length were higher in the plains (48 percent)
than in either the xeric (29 percent) or mountains (20 percent) climatic regions (Figure 3).
Although the proportion of non-target stream length was relatively high in the plains climatic
region, the total stream length in the RF3 file was less than 5,000 km for the plains in Wyoming.
The majority of the perennial stream length in Wyoming was located in the mountains (30,032
km) and xeric (15,751 km) climatic regions.
108
-------
An Assessment of USEPA Region 8 Streams and Rivers
1 1 1 1 1 1 !'
¦ 1 <
i 1 i
Wyoming
Total 50.764 kilometers
1 1 '
jl > *
1 1 1
r jy
Wyoming mountains
Total 30.032 kilometers
^
Wyoming <#r ic
Total 15r751 kilometers
1 1 Awe** denied
i —"W
. £ ~J Inaccessible
«1
**=¥" | | Ncmi-target
I
1
I I D5-perc«nt confidence inter* A
Wyoming plains
Total 4,081 kilometers
I 1 1 i i i i
0 5 10 15 20 25 30 35 40
STREAM LENGTH IN KILOMETERS TIMES 1.000
'igure 3. Estimated target stream length in relation to access denied, inaccessible, or non-target
stream lengths for mountains, xeric, and plains climatic regions, and in Wyoming.
Biotic Indicators
This section presents a discussion of the biotic indicators used in the analysis of
Wyoming EMAP data. Two macroinvertebrate indicators were developed specifically for
Wyoming and the aquatic vertebrate indicator was developed by EPA-ORD for use west-wide.
Macroinvertebrates
Wyoming Stream Integrity Index (WSII) Methodology
The WSII follows the basic concept of EMAP's West-wide macroin vertebrate IB1 in that
it is a regionally-calibrated macroinvertebrate-based multi-metric index designed to assess
aquatic life use support in Wyoming perennial streams (Hargett and Zumberge 2006). The WSII
is technically an aggregation of seven individual indices developed for seven bioregions
delineated within Wyoming. The seven bioregions are the Bighorn/Wind River Mountains, the
Western Volcanic and Sedimentary Mountains, the Bighorn/Wind River Foothills, the Southern
Rockies, the Wyoming Basin, the Black Hills and the Plains. A separate multi-metric index was
created for each bioregion.
Core macroinvertebrate metrics (e.g. composition, structure, tolerance, functional guilds)
with pronounced discrimination efficiencies (degree of separation between metric values),
distributions of reference and degraded sites within a bioregion, responsiveness to human
disturbance, and no redundancy with other metrics were incorporated into the WSII. Scoring of
109
-------
Af) Assessment of USEPA Region 8 Streams and Rivers
individual metric values was based on comparisons to the 5th and 95th percentiles of bioregional
reference conditions for each metric. The final index score is an average of the individual metric
scores where higher scores imply high biological condition. The particular metrics in each index
are listed in Table 1.
wifturn
Volcanic ft
S*dtm»ntary
Mou«itatn%
Bfgnorn &
VAnd Rlvor
Moutaina
Bgriorn 4
Wind Rlwr
Foothills
soutnorri
ftocMoa
Wyoming
Bum
Stack
ran* Pi«n»
nc 3>*emercpt*ra "ao
X
\
X
A
A
A
No ^Taxa
X
no ~3xa
X
X
X
X
X
No nana Taxa
X
he Trfcnopwa ~xxa
X
X
X
X
X
X
composition Mttrtcs
*• ITIMC!
X
X
X
X
X
** stecoprtra
X
A
X
*• Tticoptera ricct ^ycptychlcaewvvthlnirwTrfcftofne'a.
X
X
X
s ^ttpiwoptfira ;«s Batioat! :v* mm int corrvmncy >
X
ThcepttraiiMt ^aroptyzntsati .;w tfiin thocomrurwy:
X
X
A
X
Ltn Hi*toryM*triot
Nd stnwocnt Taxa <««Cattooftfat
X
X
X
X
X
X
Functional ftoding/Habltat Group M*trtc«
•• Co»*c*f-£»tr«r*r
X
X
X X
X
X
X
Nc &:rapcrTaxa
X
X
A
Toloranco Motrict
X
X
X
Hffl
X
X
X X
Dtv»r«ity Motrlc*
••5 Dorr ant Taxa
X
Table 1. Macroinvertebrate metrics used in each individual MMI.
Wyoming RIVPACS Methodology
Similar to the west-wide EMAP O/E index, Wyoming RIVPACS is a statewide
macroinvertebrate-based predictive model that provides an assessment of biological condition by
comparing the macroinvertebrate taxa observed at a site of unknown biological condition with
the indigenous macroinvertebrate taxa expected to occur in the absence of human stress (Hargett
et al 2007; Hargett et al 2005). Predictor variables such as site latitude, longitude, substrate type,
watershed area, elevation and geology were used to construct the model. The expected
macroinvertebrate taxa are derived from an appropriate set of reference sites that are minimally
or least impacted by anthropogenic stress. The deviation of the observed from the expected taxa,
known as the O/E value, is a measure of the compositional similarity expressed in units of taxa
richness and thus a community level measure of biological condition. O/E values near 1 imply
high biological condition while values <1 imply some degree of biological degradation.
Aquatic Vertebrates
The vertebrate index used in this report represents an assessment of the biotic integrity of
the fish community, calculated by synthesizing nine metrics into a combined index, or MMI,
developed by Stoddard et al (2005a). Each of the nine metrics represents a metric class or aspect
of biotic integrity: habitat (preferred habitat such as benthic or water column); tolerance (general
110
-------
An Assessment of USEPA Region 8 Streams and Rivers
tolerance to physical and chemical stressors); trophic group (for example, omnivore or
piscivore); reproductive (habit for each species); composition (relative abundance of different
kinds of taxa); richness (the number of taxa); life history (for example, long-lived or short-lived);
alien species (native or introduced); and abundance. Vertebrate MMIs were developed separately
for the mountains, xeric, and plains climatic regions, as well as for a West-wide assessment
designed to avoid introducing regional bias (Stoddard et al 2005b).
Periphyton
Wyoming's periphyton index was developed by scientists from USGS and USEPA. Index
development utilized over 250 diatom metrics from five categories, applied to data from regions
in Utah, Wyoming, and Colorado. External validation of bioregionally specific periphyton
indices was accomplished by utilizing separate sets of calibration and test data (Table 2). Data
from the Wyoming basin was randomly split in two groups, creating a calibration data set for
index development and a test dataset for index validation. For the mountain bioregion, data from
Montana, Wyoming and Idaho (Northern Rockies) were included the calibration and test data
sets. Metric selection was accomplished in the same manner as described in the Colorado
chapter. Periphyton metrics are listed in Table 3.
Table 2. Subsets of EMAP data used to develop periphyton indices for Wyoming.
Region
(EC03)
ECOREGL3
Calibration
data R sites
Calibration
data T sites
Test data R
sites
Test data T sites
Wyoming
Basin
18
5
4
4
4
Mountains
MT,WY,ID
23
7
24
8
Rangeland
Plains
42-44
15
25
16
24
Ill
-------
An Assessment of USEPA Region 8 Streams and Rivers
Table 3. Periph}
rton MMI metrics.
Bioregion
Metric
Category
Mountains
Achnanthes (sensu lato, or "old" taxonomic classification)
Number of Individuals
Composition
Navicula (sensu stricto, or "new" taxonomic classification)
Richness
Richness
Bahls (2004) Non Motile Percent Taxa
Morphology
Van Dam (et al. 1994) Trophic Class 1&2 Richness
Tolerance
Van Dam (et al. 1994) Oxygen Classes 4&5 Taxa Richness
Tolerance
Rangeland
Plains
Cymbella (sensu lato, or "old" taxonomic classification)
Richness
Richness
Percent Individuals in Cymbella/Navicula (sensu stricto, or
"new" taxonomic classification)
Composition
Bahls (2004) Highly Motile Percent Taxa
Morphology
Van Dam (et al. 1994) Oxygen Classes 1&2 Percent
Individuals
Tolerance
Wyoming
Basin
Percent Individuals in Navicula (sensu stricto, or "new"
taxonomic classification)
Composition
Bahls (2004) Highly Motile Percent Taxa
Morphology
Fragilaria (sensu lato, or "old" taxonomic classification)
Richness
Richness
Van Dam (et al. 1994) Oxygen Classes 4&5 Number of
Individuals
Tolerance
Stressor Indicators
The term stressor as used here refers to variables often associated with negative impacts,
or stresses, to stream ecosystems. Multiple factors, such as land use, geology, and climate can
affect concentrations or measures of stressor variables. Examples of stressors to streams in
Wyoming include ammonia (a form of nitrogen), phosphorus, trace elements, habitat
degradation, and bacteria (Wyoming DEQ 2006). The stressors described in this report were
selected to complement those described by Stoddard et al (2005a), and represent only a subset of
the data available on a State-wide and EMAP West-wide basis, which in turn encompass only a
subset of the multitude of influences on stream ecosystems.
Stressors analyzed in this assessment were three chemical (total phosphorus, total
nitrogen, and conductivity), four habitat (streambed stability, riparian vegetation, riparian
disturbance, and habitat complexity), and two biological (invasive plants and alien vertebrates).
All of these were measures that would give some indication of human influence to streams and
may directly or indirectly impact biological indicators.
Setting Expectations
An assessment of stream condition is perhaps most useful when conditions or
expectations have been determined in order to provide a point of comparison. In the case of the
112
-------
An Assessment of USEPA Region 8 Streams and Rivers
EMAP West-wide report, Stoddard et al (2005b) defined a reference condition for such
comparisons, with caveats. They recognized that stream conditions today might be different than
conditions 50 years ago, or perhaps hundreds of years ago, because of anthropogenic influences.
Stream condition categories - least-disturbed, most-disturbed, and intermediate - were
designated on the basis of conditions as they exist today. Reference conditions were determined
using chemical constituents and habitat measurements such as nutrients, chloride, turbidity, and
excess fine sediments. To avoid circularity, biological indicators were not used to determine the
reference condition.
Unique numeric thresholds for macroinvertebrates were developed for each of
Wyoming's bioregions. Index scores were derived from the 25th percentile of reference
conditions and an equal trisection of values below this threshold, codified into least, moderately,
and most-disturbed. These correspond in Wyoming to one of three narrative aquatic life use-
support criteria of 'full-support', 'indeterminate', and 'partial/non-support'. The indeterminate
category is technically not a use-support category, but rather a designation that requires the use
of other information to make a proper use-support assignment. Details on the numeric thresholds
for each bioregion and more information on the WSII can be found in Hargett and Zumberge
(2006).
O/E values are codified into one of three narrative aquatic life use-support criteria where
values >0.836 were considered least-disturbed or 'full-support', values between 0.836-0.662
were moderately-disturbed or 'indeterminate' and values <0.662 were most disturbed or
'partial/non-support'. The vertebrate index thresholds were the same ones created in the west-
wide assessment for the three large regions of the West (mountains, plains, xeric) (U.S. EPA
2005). Thresholds used for all biological and stressor indicators are listed in Table 4.
113
-------
An Assessment of USEPA Region 8 Streams and Rivers
Mountains
Xeric
Plains
Variable
Most
disturbed
Least
disturbed
Most
disturbed
Least
disturbed
Most
disturbed
Least
disturbed
Vertebrate MMI
<37
> 62
<29
> 40
<35
> 45
WSII Bighorn/Wind
River Mtns
<40.5
>60.7
NA
NA
NA
NA
WSII Western
Volcanic &
Sedimentary Mtns
<40.3
>60.4
NA
NA
NA
NA
WSII Southern Rocky
Mtns
<45.5
>68.2
NA
NA
NA
NA
WSII Bighorn/Wind
River Foothills
<41.4
>62.1
NA
NA
NA
NA
WSII Wyoming Basin
NA
NA
<35.6
>51.9
NA
NA
WSII Black Hills
<35.8
>53.8
NA
NA
NA
NA
WSn Plains
NA
NA
NA
NA
<28.6
>42.9
Wyoming O/E
<0.662
> 0.836
<0.662
> 0.836
<0.662
> 0.836
Periphyton MMI
<36.6
>39.3
<38.6
>67.6
<25.0
>43.9
Phosphorus, total
>40 |ig/L
< 10 |ig/L
>175 jig/L
< 40 ng/L
>300 (ig/L
< 40 ng/L
Nitrogen, total
>200 (ag/L
< 125 jig/L
>600fig/L
< 200 ng/L
>1,100 |ug/L
< 300 (ig/L
Specific conductance
>1,000
jiS/cm
<500 (iS/cm
>1,000
(iS/cm
<500 fiS/cm
>2,000
nS/cm
<1,000
aS/cm
Mercury
>0.1 ng/g
< 0.1 ng/g
>0.1 ng/g
< 0.1 |ig/g
>0.1 ng/g
< 0.1 ng/g
Riparian disturbance
>0.95
< 0.35
>0.9
< 0.7
>1.3
< 1.0
Riparian vegetation
<0.23
> 0.67
<0.32
> 0.60
<0.15
> 0.35
Streambed stability
<-1.8 or >0.1
(MR)
>- 1.1 and
< -0.4 (MR)
<-1.7 or
>0.3
> -0.9 and
< -0.1
<-2.5 or
>0.3
> -1.7 and
< -0.5
<-1.6 or >0.3
(SR)
>- 0.9 and
< -0.2 (SR)
Habitat complexity
<0.18 (MR)
>0.34 (MR)
<0.132
> 0.270
<0.125
> 0.359
<0.31 (SR)
> 0.56 (SR)
Modified from Stoddard et al 2005b; MMI, Multi-metric index; WSII, Wyoming Stream Integrity Index
(macroinvertebrates); O/E, Observed/Expected; |ig/L, micrograms per liter; (iS/cm, microSiemens per centimeter;
ug/g, micrograms per gram; MR, Middle Rockies Ecoregion; SR, Southern Rockies Ecoregion
Table 4. Thresholds used to separate condition classes in the mountains, xeric, and plains
climatic regions.
114
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
On a statewide scale, the WSII assigned 12,963 km (39%) of Wyoming's stream length
as least-disturbed, and about 9,275 (28%) as moderately-disturbed and 9,420 km (28%) most-
disturbed. In percentages, the Wyoming RIVPACS assigned a statewide biological condition
similar to what was produced by the WSII. The actual stream length for the Wyoming RIVPACS
was 9,357 km in least-disturbed condition, 6,389 km in moderate condition, and 6,086 in most-
disturbed condition. However, 11,300 stream kilometers in Wyoming could not be assessed
because it was outside the RIVPACS model (stream types were not represented in the reference
sites).
The three individual periphyton MMIs (plains, mountains and Wyoming Basin)
collectively, found 12,107 km least-disturbed (37%), 6,760 km moderately-disturbed (20%), and
14,281 km most-disturbed (43%). The fish MMI found 12,600 km least-disturbed (38%), 3,860
km moderately-disturbed (12%), and 5,600 km most-disturbed (17%). About 11,989 km (33%)
could not be assessed using fish due to either not having a permit to collect fish or no data
because no fish were present in the stream. West-wide, collecting permits sometimes were not
issued because of concerns about effects on endangered species. In Wyoming, small streams
without fish were the primary cause of a lack of data. In both cases, the unsampled category
cannot be assessed for condition, and the results of the sampled categories should not be
extrapolated to the unsampled streams (Stoddard et al 2005a).
The condition classes in Wyoming for the WSII, the Wyoming RIVPACS, fish MMI, and
periphyton MMI are presented in Figure 4. These values represent the condition for the State of
Wyoming as a whole. See Peterson et al (2007) for more detail about the condition of streams
within the various ecoregions in Wyoming and a comparison between what was found in
Wyoming versus the EMAP west-wide efforts. The periphyton MMIs found the greatest amount
of stream length in most-disturbed condition at more than 14,000 km. The WSII was next at
about 9,400 km, while the WY RIVPACS and Fish MMI were lower at 6,000 km or less. The
amount of stream length in least-disturbed condition according to each bioindicator was actually
much closer, from less than 10,000 km to 13,000 km. A large amount of stream length was not
assessed, however, using the RIVPACS model or the Fish MMI. Had both of those indicators
fully assessed the stream length, the amount in most-disturbed condition would likely be higher.
Therefore, the indicators may not be as far apart as it appears.
115
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
to
3
CO
o
<
a
>
K
>
5
s
2
X
CO
O
II
oc
UJ
a
39% .
28% >~
3=
28% >-
5%
28% h
19% >-
19%
34%
38%
12% i-
17% h-
33%
37%
20% h
43%
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Stream Length (km)
J
Figure 4. Summary of results for biological condition indicators for Wyoming (red is most
disturbed, yellow is moderately disturbed, green is least disturbed, and gray is not assessed).
Wyoming Aquatic Life Use (ALU) Support Decision Matrix
The results calculated by the WSII and Wyoming RIVPACS models are treated as
biological water quality parameters. Table 5 outlines how these parameters are evaluated to
determine whether the narrative aquatic life criterion in Chapter l of the Wyoming Water
Quality Rules and Regulations (Wyoming DEQ 2001) is attained. Sites that achieve the narrative
criterion are assessed as fully supporting aquatic life use. Sites that exceed the narrative criterion
are assessed as either partially or not supporting aquatic life use, depending on the strength of the
supporting physical and chemical data. For purposes of this report, partial and non-support are
combined into one category. Sites characterized as "undetermined" by this matrix do not receive
an assessment of use support, and are considered in need of further investigation.
116
-------
An Assessment of USEPA Region 8 Streams and Rivers,
Wyoming 0/E narrative category
Full support
Indeterminate
Partial/i KM-sipptrt
Full support
Achieves narrative aquatic
life use criteria
Achieves narrative aquatic
life use criteria
Undetermined
WSII narrative category ......
Indeterminate
Achieves narrative aquatic
life use criteria
Undetermined
Exceeds narrative aquatic
lile use criteria
Partial/lion support
Undetermined
Exceeds narrative aqujlic
life use criteria
Exceeds narrative aquatk-
lil'e lite criteria
:tl onM DIUDATC
narrative categories.
Using the ALU matrix, biological condition on a statewide scale generally followed a
pattern similar to that derived from either the WSI1 or the Wyoming RIVPACS model.
Statewide, this matrix revealed that 13,020 km of Wyoming's stream length achieves, 3,860 km
percent is undetermined and 7,890 km exceeds the State's narrative aquatic life use criteria
(Figure 5). An additional 8,378 could not be assessed for aquatic use since they did not have
either a RIVPACs score or an MM I score. The xeric region had a larger percentage of stream
length (66 percent) that achieved Wyoming's narrative ALU criteria than the mountains
(51 percent). About 26 percent of the stream length in the xeric region and 33 percent in the
mountains exceeded the State's narrative ALU criteria, indicating partial or non-support of
aquatic life uses.
Aquatic Life Use Attainment
Achieves
Undetermined
Exceeds
12%
Not Assessed
24%
25%
2000
4000
6000 8000 10000
Stream Length (km)
12000
14000
16000
18000
|
Figure 5. Aquatic life use attainment of streams in Wyoming, as indicated by a matrix of
narrative criteria from the WSII and the RIVPACS model.
117
-------
An Assessment of USEPA Region 3 Streams and Rivers
Indicators of Stress
Chemical Stressors
About 17,613 km (53%) of the stream length in Wyoming was in least-disturbed
condition for phosphorus (Figure 6), with almost 7,870 km in most-disturbed condition. The
percentage of stream length affected by phosphorus (most-disturbed) was about 35% in the
Wyoming mountains region. In the Wyoming xeric region, no streams were in a most-disturbed
condition for phosphorus. An intermediate condition predominated in the plains in Wyoming.
Nitrogen was similar with 14,762 km (44%) least-disturbed and 7,667 km (23%) in most-
disturbed condition. About 30% of stream length in the Wyoming mountains was in most-
disturbed condition, while only about 10 percent of the stream length in the Wyoming xeric
region was in a most-disturbed condition. Most of the stream length in the plains was in a most-
disturbed or intermediate condition within Wyoming. Specific conductance measurements
indicated a high proportion of streams in the least-disturbed condition for Wyoming at 25,041
km (76%). Only 3,176 km (10%) was in most-disturbed condition.
Concentrations of mercury in fish-tissue samples indicated that 11,386 km of stream
length in Wyoming was in favorable condition (Figure 6), having mercury concentrations less
than the 0.1 (jg/g criterion for protection of the American river otter Lontra canadensis
(Lazorchak et al 2003). About 5,830 km was in most-disturbed condition for fish tissue mercury,
exceeding the 0.1 jag/g threshold. However, 15,872 km were not assessed for fish tissue mercury.
Fish samples were either a composite of multiple, small fish of a single species per site or
individual specimens of larger fish. The fish species selected in Wyoming generally were not
piscivores (fish-eating) because of a lack of availability. Piscivores, such as walleye and river
otter, tend to accumulate mercury and have higher concentrations of mercury than their prey,
such as the minnows, suckers, and small trout sampled in Wyoming.
118
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Extent
Phosphorus
Nitrogen
Conductivity
Fish Tissue Hg
Habitat Complexity
1 i 1
Streambed Stability
Riparian Vegetation
Riparian Disturbance
_
5000
10000 15000 20000 25000 30000
Stream Length (km)
Figure 6. Summary of results for stressors in Wyoming.
Numeric aquatic life criteria exist for three of the water-quality constituents that were
analyzed from EMAP samples. Criteria for total chloride, dissolved zinc, and pH are listed in
Appendix B of Chapter 1 of the Wyoming Water Quality Rules and Regulations (Wyoming DEQ
2001).
Chloride concentrations exceeded the aquatic life chronic value of 230 milligrams per
liter (mg/L) at 4 of 71 sites. The acute aquatic life value of 860 mg/L for chloride was exceeded
at one site. The hardness dependent chronic aquatic life criterion for dissolved zinc was exceeded
at one of 71 sites. At all 71 sites, pH was within the acceptable chronic aquatic life use criterion
range of 6.5 to 9.0 units.
Physical Habitat Stressors
Least disturbance to riparian areas was found in 14,229 km of stream length in Wyoming
and 15,745 km most-disturbed. The proportion of stream length in least-disturbed condition for
riparian disturbance is highest in the mountains climatic region (about 58 percent). The
percentage of most-disturbed stream length exceeds that of least-disturbed stream length in both
the plains and xeric climatic regions. The xeric climatic region had the highest percentage of
most-disturbed riparian stream length in Wyoming (90 percent). For riparian vegetation cover,
5,867 km was least-disturbed and 8,388 km was most-disturbed. The mountains climatic region
119
-------
An Assessment of USEPA Region 8 Streams and Rivers
had only 1,931 km of stream length in most-disturbed condition in Wyoming and 3,435 km in
least-disturbed condition. Riparian vegetation in the xeric and plains climatic regions was found
to have higher percentages of most-disturbed stream length in Wyoming than in the mountains.
Habitat complexity was in least-disturbed condition in 10,949 km of stream length and
14,317 most-disturbed. Of the three Wyoming climatic categories, the mountains had the highest
percentage of least-disturbed stream length (39 percent) while the plains had zero least-disturbed
stream length. The streambed stability indicator found 13,357 km in least-disturbed condition,
11,221 km moderate, and 6,659 most-disturbed (about 6% could not be assessed). Wyoming
mountain streams exhibited fewer problems with stream stability having 13 percent stream
length in the most-disturbed category. The xeric and plains climatic regions within Wyoming had
a higher percentage of stream length in the most-disturbed category, with 32% and 56%,
respectively.
Biological Stressors
EMAP samples indicated non-native vertebrates were common in many mountain and
xeric climatic region streams in Wyoming. Non-native vertebrates identified generally were
trout, such as brown trout (Salmo trutta), brook trout (Salvelinus fontinalis), and rainbow trout
(Oncorhynchus mykiss). Although these three trout species are in fact not native to Wyoming,
their presence likely reflects either stocking for recreational fishing or movement and
reproduction from areas where they were stocked. The non-native trout can present a serious
threat to genetic purity or existence of native cutthroat trout populations (Oncorhynchus clarki),
but that issue is beyond the scope of this report. Other non-native vertebrates identified included
common carp (Cyprinus carpio) and the fathead minnow (Pimephales promelas) which has been
introduced to Wyoming west of the continental divide. The EMAP-West Report (Stoddard et al
2005b) derived thresholds for non-native vertebrates, which were: if more than 10% of the
vertebrate individuals captured at a site were non-native they were listed as common, more than
0% but less than 10% was considered "present" and if none were found they were absent. In
Wyoming, non-native fish were common in 12,172 km of stream length (55%), present in 1,642
km (7%), and absent in 7,772 km (35%). A total of 22,291 km was assessed for introduced fish
out of the total of 33,147 km.
The Asian clam (Corbicula fluminea) and some non-native species of crayfish
(Decapoda) were noted as invertebrate biological stressors to streams of the Southwestern U.S.
by Stoddard et al (2005b). Those species of invertebrates were absent or not identified from
EMAP samples in Wyoming.
Twelve invasive plants were also noted for presence throughout the full EMAP-West
study area. Of those 12, common ones found in Wyoming were cheatgrass (.Bromus tectorum),
musk thistle (Carduus nutans), Canada thistle (Cirsium arvense), Russian olive (Elaeagnus
angustifolia), salt cedar (Tamarix sp.) and reed canary grass (Phalaris arundinacea). In
Wyoming, these were either common (found at 10-50% of transects) or dominant (found in more
than 50% of transects) in about 55% of stream length where sampled and absent in 39%.
Invasive plants were assessed in 31,316 stream kilometers (out of the total of 33,147 km).
120
-------
An Assessment of USEPA Region 8 Streams and Rivers
Relative Extent of Stressors
Riparian disturbance was a common stressor to streams State-wide and in the climatic
regions within Wyoming, but was the predominant stressor only in the xeric climatic region of
Wyoming where about 90 percent of the stream length was rated in poor condition due to
riparian disturbance. Other physical stressors affected Wyoming streams, such as: 1) a lack of
habitat complexity that affected more than 40 percent of stream length State-wide; 2) riparian
vegetation that was rated poor in more than 40 percent of the stream length in the xeric and
plains climatic regions; and 3) streambed stability that affected more than 70 percent of the
stream length in the plains. Nitrogen and phosphorus, which are chemical stressors, affected
about 20 percent of the stream length Statewide; phosphorus affected 36 percent of the stream
length in the Wyoming mountains climatic region. Specific conductance affected less than 10
percent of streams Statewide, but more than 50 percent of the stream length in the plains was
rated poor for specific conductance. Non-native vertebrates were common in Wyoming, except
for the plains, but this stressor is affected by introduced game fish as previously described.
Conclusions
EMAP data were collected from 74 sites in Wyoming, using a probabilistic design to select
stream reaches from the RF3 file. EMAP data from Wyoming were analyzed using a
macroinvertebrate MMI (the WSII) and O/E calculated using a RIVPACS model developed by
the State of Wyoming. Narrative ratings determined from the MMI and the O/E then were used
in a matrix to determine suitability for aquatic life use (ALU). An assessment of data for
chemical and physical stressors was conducted by comparing data from sampling sites to
reference conditions established by Stoddard et al (2005) for 12 Western states that participated
in the Western Pilot EMAP study. Major findings of the ecological assessment were:
• The Wyoming macroinvertebrate MMI indicated most streams were in full support of
their aquatic life use. Proportions of streams in various disturbance classes generally
were similar between the WSII and the EMAP MMI on both the State-wide and climatic
region basis. Exceptions occurred in the mountains climatic region, where the WSII
assigned a higher proportion of mountain streams (34 percent) to the most-disturbed
category than the 20 percent assigned by the EMAP MMI, and in the plains climatic
region. Differences between the WSII and the EMAP MMI in the plains could well be
caused by the small number of sites available for testing and possible differences in
reference conditions.
• The Wyoming O/E assigned more stream length in Wyoming to the full support
condition than either the partial/non support or indeterminate condition categories.
There were, however, appreciable differences in biological condition assigned by the
Wyoming O/E compared to the EMAP O/E at both the statewide and climatic region
scales. For example, the EMAP O/E model assigned 58 percent of the stream length
Statewide to the least-disturbed (full support) condition, compared to 43 percent assigned
by the Wyoming O/E model.
• The State-wide ALU matrix results by stream length indicated 52 percent achieves, 16
percent was undetermined, and 32 percent exceeded the State's narrative aquatic life use
criteria. The xeric climatic region had the highest proportion of stream length (66
121
-------
An Assessment of USEPA Region 8 Streams and Rivers
percent) that achieved the ALU criteria, and the mountains had 51 percent in the achieved
ALU category.
• For chemistry measures, the least-disturbed condition prevailed State-wide, where
phosphorus and nitrogen concentrations were least-disturbed for 50 to 60 percent of the
stream length, and specific conductance values were least-disturbed for about 80 percent
of the stream length. Mercury in fish concentrations State-wide was at about 60 percent
of stream length less than the criterion for protection of piscivores.
• Conditions for three physical stressors, riparian disturbance, streambed stability, and
habitat complexity were similar in least-disturbed stream length Statewide in Wyoming at
between 10000 to 15000 km. Riparian vegetation condition was lower at around 6000
km. Habitat complexity and riparian disturbance both were around 15000 km in most
disturbed condition, while steambed stability and riparian vegetation indicated around
7000-8000 km in most disturbed condition.
In conclusion, the probabilistic design of the EMAP study provides a foundation and
example for future monitoring in Wyoming. The WDEQ incorporated a probability survey
component into the State monitoring strategy in 2004 and plans to do so for the foreseeable
future.
Future Directions
WDEQ implemented a probability survey into its monitoring strategy in 2004. WDEQ
has sampled 15-20 sites per year, and will continue to do so for the foreseeable future. WDEQ's
design builds upon the foundation laid by EMAP to enhance the State's ability to assess and
track water quality conditions at large spatial scales. In addition, probability surveys present an
unbiased method for locating problem areas in need of water quality improvement, as well as
new candidate reference sites. Peterson et al (2007) has much more detailed information on how
Wyoming compared to the West as a whole and for more information on the condition of
bioregions within the State.
122
-------
An Assessment of USEPA Region 3 Streams and Rivers
Middle Rocky Mountains Ecoregion
Physical Setting
The Middle Rockies Ecoregion (Ecoregion 17) (Omernik 1999) contains the
mountains and valleys of southwestern Montana (along with outlying isolated ranges to
the east) and northwestern Wyoming south and east to the Wyoming Range, the Wind
River Range, and the Bighorn Mountains. It also includes the Black Hills of northeastern
Wyoming and western South Dakota. It is, therefore, a very diverse ecoregion, but
mainly mountainous and with a relatively low population. Northwestern Montana is not
included in this ecoregion - that area is contained within the Northern and Canadian
Rockies Ecoregions.
Precipitation in the Middle Rockies Ecoregion has a large range, from between 12
inches (30 cm) per year in the low valleys of western Montana to more than 65 inches
(165 cm) in the highest mountains of southwestern Montana and northwestern Wyoming.
The topography is also very diverse, with elevation running from about 3000 feet (914
meters) on the eastern edge of the Black Hills to 13,804 feet (4204 meters) at Gannett
Peak in Wyoming's Wind River Mountains. This ecoregion could easily be treated as
several subregions if enough sample sites existed (this is especially true of the lower
valleys and the Black Hills). Major rivers in the area include the Yellowstone, Missouri,
Blackfoot, and the Clark Fork.
Human Influence
The major population centers are generally in the large valleys of Montana and
include the cities of Helena, Missoula, Butte, and Bozeman. Missoula is the largest city at
more than 64,000 (U.S. Census Bureau 2006); other cities such as Helena, Butte and
Bozeman have around 28,000 to 35,000 residents (U.S. Census Bureau 2006). This
ecoregion, however, also contains large National parks (including Yellowstone National
Park), many wilderness areas, and National Forest lands.
The greatest impact to streams in the ecoregion occurs from grazing, mining,
timber harvest, development, and oil and gas production. There is some irrigated
cropland in the valleys as well. However, in much of the ecoregion there is little human
impact and least-disturbed sites were in abundance.
This area was assessed because it stands alone with enough sites, is diverse, and
contains some of the least-disturbed areas in EPA Region 8. Land cover for this
assessment unit is presented in Figure 1. It is covered predominantly by forest and
grassland, with agricultural areas in the valleys of western Montana. The gray regions
within northwestern Wyoming are the result of the fires in Yellowstone National Park in
1988.
123
-------
An Assessment of USEPA Region 8 Streams and Rivers
Figure 1. Land Cover of the Middle Rockies (Ecoregion 17).
| | Middle Rocky
Mountains
[H Water
| Urban
Barren
| Forest
j Shrubland
| Grassland
1 Cropland
Wetland
100 200 400
Kilometers
Extent of Streams
A total of 145 sites were sampled in this area (70 probability sites and 75 "hand-
picked" as potential reference sites) within EPA Region 8 (the ecoregion extends into
Idaho, which was not included). Sixty-seven probability sites were used in the final
assessment. Approximately 48,732 kilometers of perennial streams are contained within
this assessment area (+/- 5,255 km) according the EMAP-West evaluation; the 67 sites
used for assessment represent 42,242 (+/- 5,840) kilometers. Eight sites were denied
access by landowners (representing about 4,100 km) and 9 were physically inaccessible
(representing about 4,300 km). Almost 12,200 kilometers of stream were non-target
(either dry or found to contain impoundments). The 42,242 km of assessed stream length
in this ecoregion represents about 30% of the stream length in EPA Region 8. The
location of sites sampled in this assessment unit is presented in Figure 2.
124
-------
An Assessment of USEPA Region 3 Streams and Rivers
* Probability Sites
~ Hand-Picked Sites
| | Middle Rocky Mountains
Ecoregion
Figure 2. Location of sampled sites in the Middle Rockies Ecoregion (black dots
represent probability sites and the green dots are hand-picked sites).
Kilometers
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
site discussion in the introduction of this report, reference sites are considered to be the
least-disturbed sites for a given ecoregion.
The original designation for least-disturbed and stressed sites done by EPA-ORD
(Stoddard et al 2005a; Stoddard et al 2005b) was revised by each state using local
knowledge, and in some cases, locally determined methods.
125
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biotic Indicators
A number of different macroinvertebrate MMIs were developed to assess this
area. More details on the macroinvertebrate MMI development can be found in the
Montana, South Dakota, and Wyoming chapters of this document, along with the EMAP-
West report (Stoddard et al 2005b).
Development of a periphyton MMI for this assessment unit followed the outline
of MMI development presented in the EMAP-West Report (Stoddard et al 2005b). One
MMI was developed for the Middle Rocky Mountains, but was applied to only the
Wyoming portion of the ecoregion. A separate periphyton MMI was developed in
Montana and applied to the ecoregion within that state. See the Wyoming chapter for
more detail on the periphyton MMI development. A periphyton MMI was not applied to
the Black Hills of South Dakota and they were unassessed using periphyton.
Stressor Indicators
Stressors analyzed in this assessment unit were three chemical (total phosphorus,
total nitrogen, and fish tissue mercury), four habitat (streambed stability, riparian
vegetation, riparian disturbance, and habitat complexity), and two biological (invasive
plants and alien vertebrates). All of these were measures that could give some indication
of human influence to streams and may directly or indirectly impact biological indicators.
Setting Expectations
Thresholds of condition (least- versus most-disturbed) were set for each biological
or stressor indicator using reference (least-disturbed) sites chosen for comparison to the
entire population. Different sets of least-disturbed sites were used depending on the
parameter to judge. Biotic condition was assessed using sets of least-disturbed sites
chosen through the reference site method discussed above. Biological indicator
thresholds were developed independently in Montana, Wyoming, and the Black Hills of
South Dakota.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites for a number of chemical and habitat parameters excluding the
stressor to be assessed to avoid circularity. Therefore, there is a different set of least-
disturbed sites for each stressor. Since stressors used to determine least-disturbed sites are
removed in the process, the confidence in these sets as reference sites is somewhat
diminished. Therefore the confidence that they truly represent least-disturbed sites is
lower. Thresholds for stressors were developed somewhat differently in each state within
this ecoregion. For the Black Hills of South Dakota and in the Wyoming portion of the
ecoregion, all stressor thresholds were the same as those developed for the EMAP-West
report (Stoddard et al 2005a; Stoddard et al 2005b). In the Montana portion of the
ecoregion, only the physical habitat stressor thresholds were the same as those developed
for EMAP-West. However, chemical stressor thresholds were developed by the State of
Montana and are described in the Montana chapter of this document. Use of the
126
-------
An Assessment of US EPA Region 8 Streams and Rivers
thresholds developed for habitat measures in the EMAP-West report applies only to this
work and does not imply use by any individual state for assessment.
Biological Condition
Using the various macroinvertebrate MMIs covering this area, 20,269 km (48%)
of stream length was in least-disturbed condition, 8651 km (20%) moderately-disturbed,
and 12,501 km (30%) most-disturbed. Two separate predictive models developed
independently in Montana and Wyoming were applied to this ecoregion and O/E scores
were calculated for most sites. The models found 18,069 km (43%) of stream length was
least-disturbed, 3,998 km (9%) moderate, and 15,046 km (36%) most-disturbed. About
12% of stream length was unassessed with the predictive models. These were sites found
to be outside of the predictive model; there were no reference sites present in the data to
determine their condition.
The periphyton MMIs found 25,647 km (61%) least-disturbed, 3,197 km (8%)
moderate, and 11,541 km (27%) most-disturbed. About 4% of stream length was not
assessed using periphyton. The amount of stream length by condition class for
macroinvertebrates and periphyton is shown in Figure 3.
Biological Condition
48%
20% '
J—>2%
30%
¦—i 9%
36%
12%
2
2
§
S.
HUHIHI
| 8%
27%
I
1 4%
5000 10000 15000 20000
Stream Length (km)
25000
30000
35000
-igure 3. Biological condition based on the macroinvertebrate and periphyton MMIs (red
is most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is
not assessed).
127
-------
An Assessment of USEPA Region 8 Streams and Rivers
Indicators of Stress
The amount of stream length in the most-disturbed condition for total phosphorus
was 9,349 km (with 26,457 km least-disturbed). For total nitrogen, 5,971 km of stream
length was in most-disturbed condition and a similar amount of 25,091 km in least-
disturbed condition. Mercury in fish tissue (all fish samples, regardless of size) at levels
>0.1 pg/g (Lazorchak et al 2003) was found in only 3,041 km of stream length, lower
than this level in 11,735 km. However, more than 63% of stream length (25,646 km) was
unassessed.
Riparian areas with the least human disturbance were found in 20,665 km of
stream length in the Middle Rocky Mountains Ecoregion. Over 14,971 km was most-
disturbed. For riparian vegetation cover, 11,292 km was least-disturbed and 5,512 km
most-disturbed. Habitat complexity was in least-disturbed condition in 25,373 km of
stream length and 9,165 km most-disturbed. The streambed stability indicator found
12,738 km in least-disturbed condition, 17,484 km moderate, and 10,561 km most-
disturbed. The amount of stream length in each condition class for each stressor in the
Middle Rockies Ecoregion is presented in Figure 4.
Stressor Extent
Phosphorus
Nitrogen
1
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
5000 10000 15000 20000 25000 30000 35000
Stream Length (km)
Figure 4. Extent of stressors in least, moderate, and most-disturbed condition (red is
most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is not
assessed).
128
-------
An Assessment of USEPA Region 8 Streams and Rivers
Riparian disturbance affected the largest amount of stream length compared to
other stressors in the Middle Rocky Mountains at 15,000 km. All others were at around
10,000 km or less with streambed stability, phosphorus and habitat complexity the next
most common stressors.
Two biological stressors were measured in this study, but not presented on the
chart. These were alien vertebrates (mainly fish in this region) and invasive plants. If
more than 10% of the vertebrate individuals captured at a site were alien they were listed
as common, more than 0% but less than 10% was considered "present" and if none were
found they were absent. Alien vertebrates were common in 13,630 km (56%) of stream
length, present in 1,974 km (8%), and absent in 5,237 km (22%). About 14% was not
assessed for this indicator.
Twelve invasive plants were noted for presence throughout the full EMAP-West
study area. Of those 12, common ones found in the Middle Rocky Mountains Ecoregion
include common burdock (Arctium minus), cheatgrass (Bromus tectorum), musk thistle
(¦Carduus nutans), Canada thistle (Cirsium arvense), and Russian olive (Elaeagnus
angustifolia). These were common (found at 10-50% of transects) or dominant (found in
more than 50% of transects) in 36% of stream length where sampled and absent in 59%.
A total of 37,784 stream kilometers was assessed for invasive plants (out of a total of
42,242 km).
Conclusions
Although much of this area is among the least impacted in Region 8, the
bioindicators found between 11,500 and 15,000 km in most-disturbed condition, which
translates into about one-fourth to one-third of stream length. This disturbance is
determined based on reference sites from within this ecoregion and these disturbed sites
might not be as "disturbed" as sites outside this region. Nevertheless, for streams within
the Middle Rocky Mountains they have enough impacts to depress the biota. While the
amount in most-disturbed condition is fairly consistent between indicators, it is more
varied for the determination of least-disturbed condition. The periphyton MMI found
more stream length in least-disturbed condition at about 26,000 km. The two
macroinvertebrate indicators were closer to each other at between about 18,000 and
20,000 km. Despite somewhat similar stream lengths, individual sites often were found to
be in opposite condition depending on the indicator. For example, of the 16 sites found to
be in most-disturbed condition by the macroinvertebrate MMI, three-fourths were
considered least-disturbed by the periphyton MMI. In contrast, the macroinvertebrate
predictive model found only 1 in least-disturbed condition, meaning the differences
between the two macroinvertebrate indicators was much smaller. The difference between
the two assemblages underscores the need for multiple assemblages, since they are often
responding to different stressors.
Out of more than 42,000 km assessed, all indicators of stress but one were in the
most-disturbed condition for less than one-fourth of the stream length (some as little as
14%). The exception was riparian habitat disturbance, which at 15,000 km, affected over
129
-------
An Assessment of USE PA Region 8 Streams and Rivers
one-third of stream length. Fish tissue mercury was fairly low in extent as well, but a
huge amount of stream length was unassessed. This assessment area would be expected
to have lower impacts from various stressors than many other portions of the Region.
Recommendations / Data and Information Gaps
While this area may have lower total impacts from stressors, with the exception of
some habitat issues, the biota was found to be impacted in roughly 30% of the stream
length. It may require further investigations into what stressors are actually impacting the
aquatic life in those areas. More sites would allow some investigation of the relative risk
of various stressors, not just their extent.
About 60% of the stream length was not assessed for mercury in fish tissue,
mainly due to fish collection restrictions. More coverage of stream length for this
indicator might be valuable, especially in popular fishing areas.
130
-------
An Assessment of USEPA Region 8 Streams and Rivers
Northwestern Great Plains Ecoregion
Physical Setting
The Northwestern Great Plains Level III Ecoregion (Ecoregion 43) is located in
western South Dakota, southwestern North Dakota, northeastern Wyoming and central
and southeastern Montana (Omernik 1999). It is predominantly grassland with some
cropland and a few areas of forestland, especially in southern Montana. Badland areas in
the western Dakotas also exist on highly erosive soils. This ecoregion completely
surrounds the Black Hills.
Precipitation in this ecoregion ranges from 12 to 19 inches (30-48 cm) per year.
Elevation varies from around 1600 feet (488 meters) in central South Dakota to 5900 feet
(1800 meters) in and around the isolated mountain ranges in Montana. Major rivers in the
area include the Yellowstone, Missouri, Powder, Tongue, Cheyenne, Belle Fourche,
White, and Little Missouri.
This ecoregion was assessed since it had enough sites for a statistically valid
survey and in general, the northern plains have seen little assessment work. There is a
need to attempt assessments in areas such as the plains in order to refine and improve
bioassessment tools. There is also a great need for locating and sampling potential
reference sites.
Human Influence
The major population centers in the Northwestern Great Plains include: Billings,
Montana (100,000), Gillette (24,000) and Sheridan (16,000), Wyoming, and Dickinson,
North Dakota (16,000). Technically Casper, Wyoming (52,000); Mandan, North Dakota
(17,000); and Rapid City, South Dakota (63,000) are in the ecoregion, but on the very
edges. Aside from impacts from the larger cities and towns, the greatest impact to streams
in this ecoregion occurs from grazing and oil and gas production. Coal bed methane
production has increased dramatically in the past five years in the Wyoming portion of
the ecoregion.
The land cover for the Northwestern Great Plains is presented in Figure 1.
Grassland covers most of this assessment unit. However, there are extensive cropland
areas, especially in southwestern North Dakota.
131
-------
An Assessment of USEPA Region 8 Streams and Rivers
I I Northwestern f
Great Plains
IB Water
I Urban
jig Barren
Forest
Shrubland
| Grassland
Cropland
Wetland
Wlometers
*igure 1. Land cover of the Northwestern Great Plains (Ecoregion 43).
Extent of Streams
A total of 160 sites were sampled in this area (101 probability sites and 59 "hand-
picked" as potential reference sites). Ninety-two probability sites were used in the final
assessment. Approximately 26,407 kilometers of perennial streams are contained within
this assessment area (+/- 3,214 km) according the EMAP-West evaluation; the 92 sites
used for assessment represent 19,713 kilometers (+/- 2,566). Twenty-one sites were
denied access by landowners (representing about 4,300 km) and 2 were physically
inaccessible (representing about 730 stream kilometers). About 10,000 km of stream
were non-target (either dry or found to contain impoundments). The assessed stream
length represents about 14% of the assessed stream length in EPA Region 8. The location
of sites sampled in this assessment unit is shown in Figure 2.
132
-------
An Assessment of USEPA Region 8 Streams and Rivers
MT
ND
H * V Z?
SD
••
wy
« *
• Probability Sites
• Hand-Picked Sites
I I Northwestern
' ' riKQoi DI oi n o
100
200
400
kilometers
Figure 2. Location of sampled sites in the Northwestern Great Plains (black dots
represent the probability sites and green are hand-picked sites).
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
site discussion in the introduction of this report, reference sites are considered to be the
least-disturbed sites for a given ecoregion.
The original designation for least-disturbed and stressed sites done by EPA-ORD
(Stoddard et al 2005a: Stoddard et al 2005b) was revised by each state using local
knowledge, and in some cases, locally determined methods. Applicable to this ecoregion,
the State of North Dakota defined least-disturbed and stressed sites in a fashion similar to
1B1 development. A set of landscape, habitat, and chemistry metrics were selected and
redundant metrics were eliminated (using a correlation matrix). Biological information
was avoided to reduce circularity. Each metric was standardized and scored on a scale
from 0 to 100 and the final Reference Index combined all the metrics into a composite
score. The top 10 percent of scores were designated as least-disturbed and the bottom 10
133
-------
An Assessment of USEPA Region 8 Streams and Rivers
percent were designated stressed for each ecoregion. A limitation to this approach is that
only 20% of the sites in each ecoregion will be classified. As a result, some least-
disturbed or stressed sites could be missed. To correct that limitation, adjustments were
made in site designations. For example, if the score for site was just outside the line for
stressed and the field sheet comments strongly suggested the site was stressed, the site
was designated as "stressed". A designation of "stressed" or least-disturbed was also
given to a site if the EPA-ORD designation and the field sheets agreed but the North
Dakota Reference Index was inconclusive.
A similar process was used to designate least-disturbed and stressed South Dakota
sites, using chemistry, habitat and landscape metrics. These metrics were also
standardized and scored on a 0 to 100 scale. The top 20th percentile of the scores was
designated least-disturbed and the bottom 20th percentile was designated as stressed.
Adjustments were made to individual sites based on the original EPA-ORD score and
individual parameters. For example, if a site scored well overall, but had a very high level
of a particular parameter (such as total phosphorus) it was removed from the least-
disturbed classification.
Biotic Indicators
Three different macroinvertebrate MMIs were developed to assess this area: one
for Montana, one for Wyoming, and one for western North and South Dakota combined.
More details on the macroinvertebrate MMI development can be found in the individual
state chapters of this document. The Northwestern Great Plains periphyton index
development is described in the North Dakota and South Dakota chapters. It is the same
as the rangeland plains periphyton MMI used in those States.
Stressor Indicators
Stressors analyzed in this assessment were three chemical (total phosphorus, total
nitrogen, and fish tissue mercury), four habitat (streambed stability, riparian vegetation,
riparian disturbance, and habitat complexity), and two biological (invasive plants and
alien vertebrates). All of these were measures that could give some indication of human
influence to streams and may directly or indirectly impact biological indicators.
Setting Expectations
Thresholds of condition (least versus most-disturbed) were set for each biological
or stressor indicator using reference (least-disturbed) sites chosen for comparison to the
entire population. Different sets of least-disturbed sites were used depending on the
parameter to judge. Biotic condition was assessed using sets of least-disturbed sites
chosen through the reference site method discussed above.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites for a number of chemical and habitat parameters excluding the
stressor to be assessed to avoid circularity. Therefore, there is a different set of least-
134
-------
An Assessment of USEPA Region 8 Streams and Rivers
disturbed sites for each stressor. Since stressors used to determine least-disturbed sites are
removed in the process, the confidence in these sets as reference sites is somewhat
diminished. Therefore the confidence that they truly represent least-disturbed sites is
lower. Thresholds for stressors were developed somewhat differently in each state within
this ecoregion. For the western North and South Dakota portions, thresholds were
developed based on the method described above in that separate sets of reference sites
were chosen for each stressor in the dataset. In the Wyoming portion of the ecoregion,
stressor thresholds were the same as those developed for the EMAP-West report
(Stoddard et al 2005a; Stoddard et al 2005b). In the Montana portion of the ecoregion,
only physical habitat stressor thresholds were the same as those developed for EMAP-
West. Chemical stressor thresholds were developed by the State of Montana and are
described in the Montana chapter of this document. Use of the thresholds developed for
habitat measures in the EMAP-West report applies only to this work and does not imply
use by any individual state for assessment.
For more information on derivation of thresholds, see the threshold discussions in
the Montana, Wyoming, North Dakota, and South Dakota chapters.
Biological Condition
Using the various macroinvertebrate MMIs that cover this area, 12,335 km (61%)
of stream length was in least-disturbed condition, 2,434 km (12%) moderately-disturbed,
and 4,170 km (21%) most-disturbed. The periphyton MMI found 11,300 km (56%) least-
disturbed, 3,990 km (20%) moderate, and 4,559 km (23%) most-disturbed. Figure 3
presents the amount of stream length by condition class for macroinvertebrates and
periphyton. The two assemblages found very similar amounts of stream length in least-
and most-disturbed condition.
135
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
2000 4000 6000 8000
Stream Length (km)
10000
12000
14000
figure 3. Biological condition based on the macroinvertebrate and periphyton MMIs (red
is most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is
not assessed).
Indicators of Stress
Slightly more than 4,140 km of stream length was in most-disturbed condition for
total phosphorus (with 11,468 km least-disturbed), while 2,549 km of stream length was
in most-disturbed condition for total nitrogen and a similar amount of 11,263 km in least-
disturbed condition. Mercury in fish tissue (all fish samples, regardless of size) at levels
>0.1 jag/g (Lazorchak et al 2003) were found in 6,000 km (30%) of stream length, lower
than this level in 6,224 km (32%). Nearly 7,693 km (39%), however, were unassessed for
fish tissue mercury in the Northwestern Great Plains.
Riparian areas with the least human disturbance were found in 7,459 km of stream
length in the Northwestern Great Plains and 7,693 km was most-disturbed. For riparian
vegetation cover, 10,737 km was least-disturbed and 5,341 km most-disturbed. Habitat
complexity was in least-disturbed condition in 5,966 km of stream length and 10,181 km
most-disturbed. The streambed stability indicator found 9.341 km in least-disturbed
condition, 3,710 km moderate, and 6,296 km most-disturbed (about 4% was not
assessed).
136
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Extent
Phosphorus
"¦
Nitrogen
US—I
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
0 2000 4000 6000 8000 10000 12000 14000
Stream Length (km)
Figure 4. Extent of stressors in least, moderate, and most-disturbed condition (red is
most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is not
assessed).
In Figure 4 the amount of stream length for each stressor in the various condition
classes is presented. Habitat complexity and riparian disturbance affected 10,000 and
8000 km, respectively, of stream length making them the most common stressors in this
assessment area. Fish tissue mercury and streambed stability were not far behind,
however, at around 6000 km in most-disturbed condition.
Two biological stressors were measured in this study, but not presented on the
chart. These were alien vertebrates (mainly fish in this region) and invasive plants. If
more than 10% of the vertebrate individuals captured at a site were alien they were listed
as common, more than 0% but less than 10% was considered "present" and if none were
found they were absent. Alien vertebrates were common in 6,221 km (35%) of stream
length, present in 5,825 km (33%), and absent in 5,864 km (33%).
Twelve invasive plants were noted for presence throughout the full EMAP-West
study area. Of those 12, the ones found in the Northern Great Plains Ecoregion were
common burdock (Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus
nutans), Canada thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian
olive (Elaeagnus angustifolia), leafy spurge (Euphorbia esula), English ivy (Hedera
helix), and reed canary grass (Phalaris arundinacea). These were common (found at 10-
50% of transects) or dominant (found in more than 50% of transects) in 74% of stream
137
-------
An Assessment of USE PA Region 8 Streams and Rivers
length where sampled and absent in 20%. A total of 16,902 stream kilometers was
assessed for invasive plants (out of a total of 19,713 km).
Conclusions
Macroinvertebrates and periphyton found very similar amounts of stream length
in both least- and most-disturbed condition. Both indicators found 4000 km as most-
disturbed, about 1/5 of stream length. Additionally, least-disturbed condition for both
indicators was found in about 11,000 to 12,000 km (around 60% of stream length).
Despite very similar stream lengths, individual sites often were found to be in opposite
condition depending on the indicator. For example, of the 13 sites found to be in most-
disturbed condition by the macroinvertebrate MMI, nine were considered least-disturbed
by the periphyton MMI. This difference between the two assemblages underscores the
need for multiple assemblages, since they are often responding to different stressors.
Habitat complexity and riparian disturbance were the stressors affecting the
greatest amount of stream length (10,000 km and 8,000 km, respectively), which is
approximately one-half of the stream length. Significant amounts of stream length were
affected however, by high concentrations of fish tissue mercury, low streambed stability,
and poor riparian vegetation. Nutrients ranked somewhat lower in this region, perhaps
due to the lesser extent of row crop agriculture; the ecoregion is mostly rangeland.
Recommendations / Data and Information Gaps
A RIVPACS predictive model to complement the macroinvertebrate MMI
throughout the ecoregion would greatly improve the assessment. Presently, Montana and
Wyoming have predictive models that cover their portions of the ecoregion, but models
are lacking in the Dakotas. However, reference site issues that impact MMI development
also are critical for development of predictive models. Further reference site investigation
will be necessary to further both approaches.
A fish MMI was used in the EMAP-West report for this area, but was developed
on a scale of the entire plains. At the scale of the Northwestern Great Plains it did not
distinguish well between reference and stressed sites and therefore, was not used in this
report. This ecoregion is difficult to assess with fish, but more efforts could be valuable
since it has higher fish species richness than much of the mountainous regions in the
Region.
More samples would allow for a relative risk determination of the stressors.
Perhaps a stressor such as phosphorus with lower extent, but greater impact would show
a stronger risk to biota. While some of the habitat stressors had the largest extent, there
may be some biases in the reference sites that account for at least some of this. More
work needs to be done to determine what constitutes reference condition for arid plains
streams. For example, what type of riparian vegetation measure is most appropriate?
Should a measure containing tree canopy or woody vegetation be used? Disturbance rates
are high due to agricultural use of the landscape, and it is possible that reference sites are
138
-------
An Assessment of USEPA Region 8 Streams and Rivers
not representative of the region. Furthermore, reference sites from subregions or differing
stream types are necessary to fully assess habitat conditions. As with bioindicators, better
reference site determination in this area is critical for future assessment.
139
-------
An Assessment of USEPA Region 8 Streams and Rivers
Northern Cultivated Plains
Northern Glaciated Plains, Western Corn Belt Plains,
and Lake Agassiz Plain Ecoregions
Physical Setting
Three ecoregions within the States of North and South Dakota were combined to
create the Northern Cultivated Plains assessment unit. This area is located within the
eastern portion of the Dakotas and contains portions of three Level III Ecoregions
(Omernik 1987): the Northern Glaciated Plains (46), the Western Corn Belt Plains (47),
and the Lake Agassiz Plain (48), This region is the most eastern portion of EPA Region
8, with the greatest extent of row crop agriculture in the Region. Additionally, the climate
is generally wetter than other parts of the Region. Because these combined ecoregions
form a larger region composed of a relatively coherent set of geographic factors, climate,
and land use at one end of the spectrum, it was deemed of value in serving as an
assessment unit.
The Northern Glaciated Plains Ecoregion is a flat to gently rolling landscape
composed of glacial till (Omernik 1987). Prior to human settlement, vegetation was
transitional grassland containing both tallgrass and shortgrass prairie and high
concentrations of temporary and seasonal wetlands important for waterfowl nesting and
migration. This ecoregion contains unique landscape features such as the Turtle
Mountains, the Prairie Coteau and a former glacial lake basin now filled by Devils Lake.
No longer covered by tallgrass prairie, over 75% of the Western Corn Belt Plains
is now used for cropland agriculture. Much of the remaining 25% is forage for livestock
(Omernik 1987). The majority of the Western Corn Belt Plains actually is found outside
the boundaries of EPA Region 8, extending to the south and east. Topographically, the
Western Corn Belt Plains consists of nearly level to gently rolling glaciated till plains and
loess deposits forming hilly plains. A fairly high annual precipitation makes this one of
the most productive areas of corn and soybeans in the world.
The Lake Agassiz Plain was once filled with Glacial Lake Agassiz, the last in a
series of glacial lakes to fill the Red River valley since the beginning of the Pleistocene
(Omernik 1987). Thick beds of lake sediments on top of glacial till create the extremely
level terrain of the ecoregion. The historic tallgrass prairie has been mainly replaced by
intensive row crop agriculture. Crops in the northern half of the region include potatoes,
beans, sugar beets and wheat. Soybeans, sugar beets, and corn predominate in the south.
Unique features include the Beach Ridges, which are remnants of former shorelines of
the original glacial lake).
The northern half of the Northern Cultivated Plains receives 15-20 inches (38-50
cm) of precipitation annually, the southern half 20-25 inches (50-63 cm), and the extreme
southern portion more than 25 inches (63 cm). Elevation within this assessment unit
ranges from about 1100 feet (335 meters) in southeastern South Dakota to 2000 feet (610
140
-------
An Assessment of USEPA Region 8 Streams and Rivers
meters) in northwestern North Dakota. Major rivers in the area include the James, Red,
Big Sioux, Sheyenne, and Souris. This area contains the highest diversity of native fish
species in EPA Region 8.
Human Influence
Pre-settlement vegetation was dominated by prairie grass with gallery forests
along streams. Now, with conversion to row crops, the landscape is rich in agricultural
production. The major population centers include Sioux Falls, Brookings, Watertown,
Mitchell, and Aberdeen in South Dakota and Fargo, Minot, Grand Forks, and Jamestown
in North Dakota. The population of this area is approximately 880,000 (US Census
Bureau 2000).
Aside from impacts from the larger cities and towns, the greatest impact to
streams occurs from agricultural production, including row crops and some grazing, and
animal feeding operations. All of these can introduce excess nutrients and sediment to
streams, with row crop agriculture potentially adding pesticide impacts. The land cover
for the Northern Cultivated Plains assessment unit is presented in Figure 1. Agricultural
land covers most of the area, with a few larger areas of grassland more common in the
northwest.
North Dakota
I v'- i' i^i triP!
£ South Dakota
1 1 Cultivated Plains
H Water
HI Urban
m Barren
H Forest
1 1 8hrubland
Figure 1. Land cover of the Northern Cultivated Plains.
141
-------
An Assessment of USEPA Region 8 Streams and Rivers
Extent of Streams
A total of 117 sites were sampled in this area (64 probability sites and 53 "hand-
picked" as potential reference sites). Fifty-nine probability sites were used in the final
assessment. Approximately 7,952 kilometers of perennial streams are contained within
this assessment area (+/- 1,547 km) according the EMAP-West evaluation. The 59 sites
used for assessment represent 7,352 (+/- 1,100) kilometers (representing about 5% of the
stream length in EPA Region 8). Only one site was physically inaccessible and 4 were
denied access by landowners (representing about 530 stream miles). About 3,030
kilometers of stream were non-target (either dry or found to contain impoundments).
Figure 2 presents the location of sites sampled in this assessment unit.
This area was assessed for condition because there were enough sites (greater than
50), and it is a unique area in EPA Region 8, both for its extensive wetlands and the land
cover is heavily dominated by row crops. Row crop agriculture has unique and intensive
impacts to aquatic systems.
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
I
North Dakota
South Dakota
Kilometers
Figure 2. Location of sampled sites in the Northern Cultivated Plains
(black dots represent probability sites and green are hand-picked sites).
142
-------
An Assessment of USEPA Region 8 Streams and Rivers
site discussion in the introduction of this report, reference sites are considered to be the
least-disturbed sites for a given ecoregion, not necessarily pristine or completely without
human influence.
The original designation for least-disturbed and stressed sites done by EPA-ORD
(Stoddard et al 2005a; Stoddard et al 2005b) was revised by each state using local
knowledge, and in some cases, locally determined methods. Applicable to this ecoregion,
the State of North Dakota defined least-disturbed and stressed sites in a fashion similar to
MMI development. A set of landscape, habitat, and chemistry metrics were selected and
redundant metrics were eliminated (using a correlation matrix). Biological information
was avoided to reduce circularity. Each metric was standardized and scored on a scale
from 0 to 100 and the final Reference Index combined all the metrics into a composite
score. The top 10 percent of scores were designated as least-disturbed and the bottom 10
percent were designated stressed for each ecoregion. A limitation to this approach is that
only 20% of the sites in each ecoregion will be classified. As a result, some least-
disturbed or stressed sites could be missed. To correct that limitation, adjustments were
made in site designations. For example, if the score for site was just outside the line for
stressed and the field sheet comments strongly suggested the site was stressed, the site
was designated as "stressed". A designation of "stressed" or least-disturbed was also
given to a site if the EPA-ORD designation and the field sheets agreed but the North
Dakota Reference Index was inconclusive.
The process used to designate least-disturbed and stressed sites in South Dakota
involved using chemistry, habitat and landscape metrics. These metrics were also
standardized and scored on a 0 to 100 scale. The top 20th percentile of the scores was
designated least-disturbed and the bottom 20th percentile was designated as stressed.
Adjustments were made to individual sites based on the original EPA-ORD score and
individual parameters. For example, if a site scored well overall, but had a very high level
of a particular parameter (such as total phosphorus) it was removed from the least-
disturbed classification.
Least-disturbed sites in this ecoregion grouping are in watersheds where
agriculture may be present and even extensive, but is not strongly impacting the stream.
A watershed can have a significant amount of cropland and still have high quality streams
if riparian areas are intact. The least-disturbed sites in this ecoregion are predominantly
from the first to fifth stream orders and are more common in the eastern and northern
portions. The western part of this ecoregion is the James River valley with relatively few
least-disturbed sites occurring there.
Biotic Indicators
A macroinvertebrate MMI was developed specific to this dataset and this
assessment unit. The procedure used to develop the macroinvertebrate MMI followed that
outlined in the EMAP-West Report (Stoddard et al 2005a).
143
-------
An Assessment of USEPA Region 8 Streams and Rivers
After separating the dataset into a calibration and validation set, the first step in
the analysis was to compare individual metrics between least-disturbed and stressed sites
to determine metrics that showed separation. Metrics were then submitted to a
redundancy test to determine those metrics that were not independent. An MMI was
created using the most strongly responsive, non-redundant metrics. Additionally, an
attempt was made to cover as many of the metric categories as possible. Metric
categories include richness, composition, diversity, tolerance, feeding, and habit.
The final macroinvertebrate MMI consisted of 6 metrics listed in Table 1. There
was one composition metric, two tolerance metrics, two feeding group metrics, and 1
habit metric. These metrics were scored from 0 to 100 based on the range of the dataset,
with the six values averaged for the final score.
Table 1. Macroinvertebrate MMI metrics.
Metric
Category
Percent EPT Taxa
Composition
Percent Predator Individuals
Feeding
Percent Individuals Rated 8 or 9 on Tolerance Scale
Tolerance
Percent Individuals Rated 6 or 7 on Tolerance Scale
Tolerance
Percent Clinger Taxa
Habit
Percent Collector-Filterer Individuals
Feeding
For the fish indicator, the MMI developed by EPA-ORD for the EMAP-West
assessment (for the entire plains) was used since it performed well at the scale of this
assessment unit (Stoddard et al 2005a). The fish metrics in this MMI are listed in Table 2.
More information on how this index was developed can be found in the EMAP-West
Report (Stoddard et al 2005b).
Table 2. Fish MMI metrics.
Metric
Category
Native Rheophilic Species Richness
Habitat
Percent Individuals Super Tolerant
Tolerance
Percent Individuals Nontolerant Invertivores or Piscivores
Trophic
Sensitive Spawner Species Richness
Reproductive
Native Catostomid and Ictalurid Species Richness (Corrected for
Stream Size)
Composition
Percent of Species that are Native, Sensitive and Migrators
Life History
Nontolerant Species Richness (Corrected for Stream Size)
Richness
Percent Alien Species
Alien Species
The Northern Cultivated Plains periphyton index was developed in a similar
manner as previously described, with data from regions in North and South Dakota. Sites
in this region did not include the larger boatable sites (n = 34). External validation of
bioregionally specific periphyton indices was accomplished by utilizing separate sets of
calibration and test data (Table 3). Data from the Northern Cultivated Plains was
144
-------
An Assessment of USEPA Region 8 Streams and Rivers
randomly split in two groups, creating a calibration data set for index development and a
test dataset for index validation. Metric selection was accomplished in the same manner
as described in the Colorado chapter. The periphyton metrics used are listed in Table 4.
Table 3. Subsets of EMAP data used to develop periphyton indices for the Northern
Cultivated P
ains.
Region
ECOREGL3
Calibration
Calibration
Test data R
Test data T
(EC03)
data R sites
data T sites
sites
sites
Northern
46-48
8
6
5
13
Cultivated
Plains
Table 4. Periphyton MMI metrics
Bioregion
Metric
Category
Northern
Cultivated
Plains
Gomphonema Species Richness
Richness
Percent Individuals in Fragilaria (sensu lato, or "old"
taxonomic classification)
Composition
Cymbella (sensu lato, or "old" taxonomic classification)
Richness
Richness
Bahls (2004) Highly Motile Percent Taxa
Morphology
Van Dam (et al 1994) Oxygen Classes 1&2 Percent Taxa
Tolerance
Stressor Indicators
Stressors analyzed in this assessment were three chemical (total phosphorus, total
nitrogen, and fish tissue mercury), four habitat (streambed stability, riparian vegetation,
riparian disturbance, and habitat complexity), and two biological (invasive plants and
alien vertebrates). All of these were measures that could give some indication of human
influence to streams and may directly or indirectly impact biological indicators.
Setting Expectations
Thresholds of condition (least- versus most-disturbed) were set for each biological
indicator or stressor using reference (least-disturbed) sites chosen for comparison to the
entire population. Different sets of least-disturbed sites were used depending on the
parameter to assess. Biotic condition was assessed using sets of least-disturbed sites
chosen through the reference site method discussed above. Sets of least-disturbed sites to
assess condition of various stressors were derived by screening all sites for a number of
chemical and habitat parameters excluding the stressor to be assessed to avoid circularity.
Therefore, there is a different set of least-disturbed sites for each stressor. Since stressors
used to determine least-disturbed sites are removed in the process, the confidence in these
sets as reference sites is somewhat diminished.
If the confidence in the least-disturbed set of sites chosen for a particular indicator
was fairly high (as with the original set for biotic indicators), then thresholds were set at
greater than the 25th percentile of least-disturbed sites for least-disturbed condition and
145
-------
An Assessment of USE PA Region 3 Streams and Rivers
less than the 5th percentile for most-disturbed condition. These thresholds were used for
the macroinvertebrate and fish MMIs, as well as the two chemical indicators. The
periphyton indicator lower threshold was set at the 10th percentile to be consistent with
another periphyton MMI developed for the rangeland plains. For the habitat stressor
indicators, percentiles for thresholds were relaxed to the 50th and 25th percentiles due to
lower confidence that these represented reference sites. Thresholds used for a given
indicator or stressor are described in Table 5.
Table 5. Northern Cultivated Plains thresholds.
Northern Cultivated
Plains
Most-disturbed
Least-disturbed
Threshold
%
Threshold
%
Macroinvertebrate MMI
<49.4
5th
>55.7
25tn
Periphyton MMI
<21.4
10th
>44.1
25th
Aquatic Vertebrate MMI
<52.1
5th
>61.5
25th
Phosphorus
>312 pg/L
95th
<228 |ig/L
75th
Nitrogen
>2501 Mg/L
95th
<1525 |ag/L
75th
Riparian Disturbance
>1.8
75th
<1.31
50,n
Habitat Complexity
<0.136
25th
>0.214
50th
Streambed Stability
<-2.58
25th
>-2.20
50th
Riparian Vegetation
<0.041
25th
>0.236
50th
Fish Tissue Mercury
>0.1 |jg/g
<0.1 n g/g
Non-native Vertebrates
>10% of
individuals
Absent
Biological Condition
Using the macroinvertebrate MMI developed for the Northern Cultivated Plains
2,177 km of stream length was in least-disturbed condition (30%), 748 km moderately-
disturbed (10%), and 4,400 km most-disturbed (60%). The fish index found a similar
result with 1,975 km least-disturbed (27%), 1,192 km moderate (16%), and 3,720 km in
most-disturbed condition (51%). About 6% of stream length was not assessed with the
fish indicator. The periphyton MMI differed from the others in the amount in most-
disturbed condition, finding less. It found 1,919 km least-disturbed (26%), 2,802 km
moderate (38%), and 2,485 km most-disturbed (34%). About 2% of stream length was
not assessed using periphyton. Interestingly, while there was a disparity in the amount
found in most-disturbed condition, all three indicators found very similar amounts of
stream length in least-disturbed condition. The amount of stream length by condition
class for macroinvertebrates, fish, and periphyton is presented in Figure 3.
146
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
2
n
0>
It
o
5
2
5
S
30%
10%
60%
27%
16%
51%
6%
26% i-
38%
34%
| 2%
1000
2000 3000
Stream Length (km)
4000
5000
6000
*igure 3. Biological condition based on macroinvertebrate, fish and periphyton MMIs
(red is most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray
is not assessed).
Indicators of Stress
Three chemical stressors were assessed in this region. The amount of stream
length in most-disturbed condition for total phosphorus was 3,903 km (53%), with 2,510
km (34%) least-disturbed. Only 1,186 km (16%) of stream length was in most-disturbed
condition for total nitrogen, but a similar as phosphorus was in least-disturbed condition -
2,847 km (39%). Mercury in fish tissue (all fish samples, regardless of size or trophic
level) were found at levels >0.1 pg/g (Lazorchak et al 2003) in 4,035 km (54%) of stream
length; lower than this level in 2,315 km (31%). Only about 900 km was unassessed for
fish tissue mercury.
Riparian areas with the least human disturbance occurred in 2,959 km of stream
length in the northern cultivated plains, while 2,413 km was most-disturbed. For riparian
vegetation cover, however, 4,499 km was least-disturbed and only 1,249 km was most-
disturbed. Habitat complexity was in least-disturbed condition in 1,746 km of stream
length and 3,072 km most-disturbed. The streambed stability indicator found 2,635 km in
least-disturbed condition, 1,029 km moderate, and 3,661 km most-disturbed. The amount
of stream length for each stressor in the various condition classes is shown in Figure 4.
The most common stressors in terms of extent in most-disturbed condition in the northern
cultivated plains were fish tissue mercury, total phosphorus, habitat complexity, and poor
streambed stability. In all of these more than 3,000 km was in most-disturbed condition.
147
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Extent
Phosphorus
Nitrogen
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
0 1 000 2000 3000 4000 5000 6000
Stream Length (km)
Figure 4. Extent of stressors in least, moderate, and most-disturbed condition.
Two biological stressors were measured in this study, but not presented on the
chart. These were alien vertebrates (mainly fish in this region) and invasive plants. If
more than 10% of the vertebrate individuals captured at a site were alien, they were listed
as common, more than 0% but less than 10% was considered "present" and if none were
found they were absent. Alien vertebrates were common in 2,482 km (35%) of stream
length, present in 1,523 km, and absent in 2,880 km (40%). Four percent was not
assessed for this indicator.
Twelve invasive plants were noted for presence throughout the full EMAP-West
study area. Of those 12, the common ones found in the Northern Cultivated Plains were
common burdock (Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus
nutans), Canada thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian
olive (Elaeagnus angustifolia), leafy spurge (Euphorbia esula), and reed canary grass
(.Phalaris arundinacea). These were common (found at 10-50% of transects) or dominant
(found in more than 50% of transects) in 90% of stream length where sampled and absent
in 10%. However, only 3,825 stream kilometers were assessed for invasive plants out of a
total of 7,352 km.
148
-------
An Assessment of USEPA Region 8 Streams and Rivers
Conclusions
The Northern Cultivated Plains Ecoregion was one of the few areas where three
biological indicators could be used (fish, macroinvertebrates, and algae). However, the
indicators found different amounts of stream length in most-disturbed condition. The
stream length in most-disturbed condition ranged from only 2,500 km for periphyton to
nearly 4,500 km for macroinvertebrates. This difference underscores the need for using
more than one bioindicator. Despite that difference, however, all found very similar
amounts of stream length in least-disturbed condition - around 2,000 km.
Three indicators of stress rank as responsible for the greatest amount of stream
length impacted (most-disturbed condition): increased concentrations of phosphorus,
decreased streambed stability, and high concentrations of mercury in fish tissue. A fourth
stressor, loss of habitat complexity, is the next most influential in terms of leading to
most-disturbed condition. All four stressors combined resulted in approximately 3,000 to
4,000 km of stream reach in most-disturbed condition. Human disturbance to riparian
areas was the next most important stressor at causing 2,400 km of stream to be in most-
disturbed condition. Increased concentrations of nitrogen (nitrate, nitrite, and ammonium)
and loss of riparian vegetation were lesser in impact at influencing approximately 1,000
km of stream reach each.
Recommendations / Data and Information Gaps
A RIVPACS (O/E) predictive model (see Ecological Indicators in the
Introduction of this report) would add valuable biological information and complement
the macroinvertebrate MMI and would be a beneficial tool that should be developed for
the area. As with development of MMIs, though, finding appropriate least-disturbed or
reference sites is one of the greatest challenges in this area. Our experience shows that
sites with extensive riparian buffers, even those with watersheds under heavy agriculture,
are likely to be among the least impacted. This collection of ecoregions contains both the
Lake Agassiz Plain, with its considerable agriculture, and the Northern Glaciated Plains
containing more wetlands. Any future indicator development (more refined MMIs and
RIVPAC models) should take into account the differences in expectation between these
portions of the assessment unit.
From the stressor analysis, nutrients, sediment and fish tissue mercury are
important parameters to begin to address. Nutrients and sediment issues are not surprising
given the heavy agriculture found in this region, but the fish tissue mercury may be
somewhat of a surprise. While high mercury in fish tissue samples was found in
individual sites throughout EPA Region 8, this particular area had a fairly high number of
samples exceeding the 0.1 ng/g threshold. While these do not necessarily correspond to a
human health concern (samples were whole fish not filets, and some were not fish of
interest for human consumption), further investigation is warranted.
149
-------
An Assessment of USEPA Region 8 Streams and Rivers
An insufficient number of samples were available to perform a relative risk
analysis for this assessment area. Given some of the large percentages of stressor extent,
obtaining the relative risk of each stressor is a logical next step.
150
-------
An Assessment of USEPA Region 8 Streams and Rivers
The Upper Missouri River Basin
Physical Setting
The Upper Missouri River Basin covers the eastern four-fifths of Montana, the
northern half of Wyoming, much of southwestern North Dakota, virtually all of South
Dakota. It includes the headwaters of the Missouri flowing from the mountains of
Montana, the Yellowstone River drainage and tributaries such as the Bighorn, Tongue
and Powder Rivers. The Upper Missouri River Basin also gathers waters from numerous
plains tributaries such as the James, Big Sioux, and Cheyenne Rivers.
The Upper Missouri Basin is covered predominantly by plains topography, but
includes the Black Hills, the Bighorn Mountains and a large amount of mountainous
terrain in southwestern Montana and northwestern Wyoming. It includes portions of the
Middle Rockies Ecoregion, almost all of the Northwestern Great Plains, much of the
Northern and Northwestern Glaciated Plains, and the northern portion of the Wyoming
Basin Ecoregions (Omernik 1999).
Precipitation varies considerably across the upper basin with 45 to 55 inches (114-
140 cm) per year in the western mountains (with some areas higher than 65 inches (165
cm) in northwestern portion), dropping to 12 inches (30 cm) in the low valleys of western
Montana and the eastern plains of Montana. Precipitation then increases eastward to more
than 22 inches (56 cm) in eastern South Dakota with over 27 inches (69 cm) in extreme
southeastern South Dakota. Elevation ranges from a high of 13,804 feet (4207 meters) at
Gannett Peak in Wyoming to only around 1,100 feet (335 meters) in southeastern South
Dakota. Some of the upper basin is in Canada (southern Alberta and Saskatchewan), in
the Milk River drainage, and is not included in this assessment.
Sites were specifically added to this region when the original EMAP-West design
was created in order to guarantee an assessment could be done of the Upper Missouri
River Basin. The upper basin has been an area of interest to EPA Region 8 for many
years due to numerous projects and activities occurring there.
Human Influence
The population of the Upper Missouri Basin is approximately 2.3 million (US
Census Bureau 2000). Major population centers include Billings, Helena, Great Falls, and
Bozeman in Montana. Bismarck in North Dakota, and Rapid City and Sioux Falls in
South Dakota are also major population centers.
Impacts to streams occur from a variety of sources, depending on land types. In
the mountains, timber harvesting, mining and development form the major impacts. In
the plains, mining, grazing, crop agriculture, and oil and gas extraction dominate. In the
Wyoming Basin, grazing and oil and gas extraction form major impacts. The land cover
for the Upper Missouri Basin is presented in Figure 1. It is mostly grassland with forest
cover in the highest areas, but large amounts of cropland in the northwest portion and the
151
-------
An Assessment of USE PA Region 8 Streams and Rivers
eastern and southeastern parts. The southwestern portion is mainly shrubland (Wyoming
Basin).
| | Upper Missouri
l—"~J Basin Boundary1
| W&ter
| Urban
Barren
| Forest
j Shrubland
| Grassland
_ Cropland
; V\tetland
Kilometers
Figure 1. Land cover of the Upper Missouri River Basin.
Extent of Streams
A total of 230 probability sites were sampled in this area and 197 probability sites
were used in the final assessment. Approximately 75,316 kilometers of perennial streams
are contained within this assessment area (+/- 13,200 km) according the EMAP-West
evaluation; the 197 sites used for assessment represent 56,957 (+/- 6,265) kilometers
(representing about 40% of the assessed stream length in EPA Region 8). Forty-four sites
were denied access by landowners (representing about 9,700 km) and 10 were physically
inaccessible (representing about 2,900 stream kilometers). About 23,500 kilometers of
stream were non-target (either dry or found to contain impoundments). The location of
sites sampled in this assessment unit is presented in Figure 2. The breakdown of stream
length in the entire basin (blue) and in the mountains, plains, and xeric regions within the
Upper Missouri Basin (green) is depicted in Figure 3.
152
-------
An Assessment of USEPA Region 8 Streams and Rivers
ND
MT
~ *•
»»
•«
WY
Upper Missouri Basin States
• Probability Sites
• Hand-Picked Sites
~ Upper Missouri River Basin Area
125
250
500
kilometers
Figure 2. Location of sampled sites in the Upper Missouri River Basin (black dots
represent the probability sites and green are hand-picked sites).
153
-------
An Assessment of USEPA Region 8 Streams and Rivers
Assessed Stream Length in the Upper Missouri River Basin
All UMB
Mountains
Plains
Xeric
0
10000
20000
30000
Stream Length (km)
40000
50000
60000
Figure 3. Assessed stream length in the Upper Missouri River Basin (blue is the stream
length in the entire basin and green represents the stream length in the various
subregions).
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
site discussion in the introduction of this report, reference sites are considered to be the
least-disturbed sites for a given ecoregion.
The original designation for least-disturbed and stressed sites done by EPA-ORD
(Stoddard et al 2005a; Stoddard et al 2005b) was revised by each state using local
knowledge, and in some cases, locally determined methods. See each state chapter for
discussions on deviations from the ORD method for determining reference sites.
Biotic Indicators
Many different macroinvertebrate MMIs were developed to assess this area. More
details on macroinvertebrate MMI development can be found in the Montana, North
Dakota, South Dakota, and Wyoming chapters of this document. Many different
periphyton MMIs were used to assess this area as well, all created at state or ecoregion
levels. Individual state or ecoregion chapters also describe the creation of these MMIs in
detail.
154
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Indicators
Stressors analyzed in this assessment were three chemical (total phosphorus, total
nitrogen, and fish tissue mercury), four habitat (streambed stability, riparian vegetation,
riparian disturbance, and habitat complexity), and two biological (invasive plants and
alien vertebrates). All of these were measures that could give some indication of human
influence to streams and may directly or indirectly impact biological indicators.
Setting Expectations
Thresholds of condition (least versus most-disturbed) were set for each biological
or stressor indicator using reference (least-disturbed) sites chosen for comparison to the
entire population. Different sets of least-disturbed sites were used depending on the
parameter to judge. Biotic condition was assessed using sets of least-disturbed sites
chosen through the reference site method discussed above.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites for a number of chemical and habitat parameters excluding the
stressor to be assessed to avoid circularity. Therefore, there is a different set of least-
disturbed sites for each stressor. Since stressors used to determine least-disturbed sites are
removed in the process, the confidence in these sets as reference sites is somewhat
diminished. Therefore the confidence that they truly represent least-disturbed sites is
lower. Thresholds for stressors were developed somewhat differently in each state within
this ecoregion. For the North and South Dakota portions, thresholds were developed
based on the method described above in that separate sets of reference sites were chosen
for each stressor in the dataset (using separate datasets from the western and eastern
Dakotas). In the Wyoming portion of the ecoregion, stressor thresholds were the same as
those developed for the EMAP-West report (Stoddard et al 2005a; Stoddard et al 2005b).
In the Montana portion of the ecoregion, physical habitat stressor thresholds were also the
same as those developed for EMAP-West. However, chemical stressor thresholds were
developed by the State of Montana and are described in the Montana chapter of this
document. Use of the thresholds developed for habitat measures in the EMAP-West
report applies only to this work and does not imply use by any individual state for
assessment.
For more information on derivation of thresholds, see the threshold discussions in
the Montana, Wyoming, North Dakota, and South Dakota chapters.
Biological Condition
Using the various macroinvertebrate MMIs that cover this area, 32,234 kilometers
(57%) of stream length was in least-disturbed condition, 7,875 km moderately-disturbed,
and 14,491 km most-disturbed (25%). About 2,331 km was unassessed using
macroinvertebrate MMIs. Unfortunately, there was not enough coverage of the area with
the predictive model to assess streams using an O/E score.
155
-------
An Assessment of USEPA Region 8 Streams and Rivers
The periphyton MMIs found a very similar result with 29,316 km (52%) least-
disturbed, 9,630 km moderate, and 13,820 km most-disturbed (24%). About 4165 km
stream length was not assessed using periphyton. The amount of stream length by
condition class for macroinvertebrates and periphyton is depicted in Figure 4.
s
s
Q
1
.Q
0)
r
0)
>
c
o
o
TO
2
a
0.1 jli g/g (Lazorchak et al 2003)
was found in 11,237 km (20%) of stream length, lower than this level in 18,398 km
(33%). More than 47% of the stream length in the Upper Missouri Basin was not assessed
for fish tissue mercury.
Riparian areas with the least human disturbance were found in 21,530 km of
stream length in the Upper Missouri basin and 23,315 km were most-disturbed. Riparian
vegetation cover was least-disturbed in 24,207 km most-disturbed in 11,686 km. Habitat
complexity was in least-disturbed condition in 25,703 km of stream length and 18,589
km most-disturbed. The streambed stability indicator found 24,291 km (43%) in least-
Bioiogical Condition
57%
14%
25%
4%
52%
17%
24%
156
-------
4/7 Assessment of USEPA Region 8 Streams and Rivers
disturbed condition, 16,637 km (29%) moderate, and 13,497 km (24%) most-disturbed
(about 4% was not assessed).
Phosphorus
Nitrogen
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
0 5000 10000 15000 20000 25000 30000 35000 40000
Stream Length (km)
Stressor Extent
Figure 5. Extent of stressors in least, moderate, and most-disturbed condition (red is
most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is not
assessed).
The amount of stream length for each stressor in the various condition classes is
shown in Figure 5. Total phosphorus, habitat complexity, and riparian disturbance each
affected more than 15,000 km in the Upper Missouri Basin, making them the most
common stressors in this assessment area. However, all other stressors impacted more
than 11,000 km, with percentages of stream length in most-disturbed condition at 19-
24%.
Two biological stressors were measured in this study, but not presented on the
chart. These were alien vertebrates (mainly fish in this region) and invasive plants. If
more than 10% of the vertebrate individuals captured at a site were alien they were listed
as common, more than 0% but less than 10% was considered "present" and if none were
found they were absent. Alien vertebrates were common in 21,615 km (50%) of stream
length, present in 9,354 km (22%), and absent in 10,275 km (24%). About 5% (2,052
km) was not assessed for this indicator.
Twelve invasive plants were noted for presence throughout the full EMAP-West
study area. Of those 12, the ones found in the Upper Missouri Basin were common
burdock (Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus nutans),
157
-------
An Assessment of USEPA Region 8 Streams and Rivers
Canada thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian olive
(Elaeagnus angustifolia), leafy spurge (Euphorbia esula), English ivy (Hedera helix),
and reed canary grass (Phalaris arundinacea). These were common (found at 10-50% of
transects) or dominant (found in more than 50% of transects) in 59% of stream length
where sampled and absent in 38%. A total of 48,792 stream kilometers were assessed for
invasive plants (out of a total of 56,957 km).
Relative Risk
~ Macroinvertebrate MMI
¦ Periphyton MMI
Streambed Stability
Habitat
t 1.5 2 2.5 3 3.5
Relative Risk
^igure 6. Relative risk of stressors to biological indicators in the Upper Missouri Basin.
Relative Risk
A relative risk analysis was done for this assessment area and for the entire
Region, since these were the only areas with enough sites to perform the analysis.
Additionally, since there is a large amount of correlation between stressors, relative risk
should be assessed based on combinations of stressors (Van Sickle 2008). In this case, the
two nutrient stressors, phosphorus and nitrogen were combined, and three habitat
stressors (riparian disturbance, habitat complexity, and riparian vegetation) were
combined into a general habitat stressor, and streambed stability was left by itself. For
the overall nutrient stressor to be considered "most-disturbed" either phosphorus or
nitrogen could be in most-disturbed condition; for the habitat stressor, two of the three
needed to be most-disturbed to label the habitat overall as most-disturbed. A relative risk
score must be significantly greater than 1.0 to be considered relevant.
Comparing the macroinvertebrate MMI with various stressors, only one stressor
showed a significant response (Figure 6). This was streambed stability at nearly three
158
-------
An Assessment of USEPA Region 8 Streams and Rivers
times the risk, meaning that when there is poor streambed stability the risk is three times
greater that the macroinvertebrates will be in poor condition as well. The periphyton
MMI, however, had a significant response only to nutrients, at about 2.5 times greater
risk to periphyton. Habitat stressors showed no significant risk to the biological indicators
at this scale.
Conclusions
Macroinvertebrates and periphyton indicators found very similar amounts of
stream length in both least- and most-disturbed condition. Least-disturbed condition in
the Upper Missouri Basin was found by both in more than one-half of stream length and
most-disturbed in about one-fourth of stream length. Despite very similar stream length,
individual sites often were found to be in opposite condition depending on the indicator.
Of the 50 sites found to be in most-disturbed condition by the macroinvertebrate MMI,
21 were considered least-disturbed by the periphyton MMI. The difference between the
two assemblages underscores the need for multiple assemblages, since they are often
responding to different stressors.
Three stressors, phosphorus, human riparian disturbance and habitat complexity,
ranked the highest with impacts to 15,000 or more stream kilometers in the Upper
Missouri River Basin (out of a total of about 57,000 km assessed). Riparian disturbance
was in most-disturbed condition in 40% of stream length. Plains sites generally had more
riparian disturbance which brings this number up in the basin. All of the other stressors
were in most-disturbed condition for about 10-15,000 km.
There were enough sites to perform a relative risk analysis on the full data,
although this number may be near the lower end for the analysis. Poor streambed stability
exhibited the greatest risk by far to macroinvertebrates, with a relative risk of nearly 3.
Nutrients were next at 2.5 times greater risk, but only to periphyton, not
macroinvertebrates. The combined habitat stressor had no greater risk associated with it
to either periphyton or macroinvertebrates at the scale of the Upper Missouri Basin.
Recommendations / Data and Information Gaps
Both Montana and Wyoming have created predictive models using
macroinvertebrates to complement macroinvertebrate MMIs. Adding this tool to North
and South Dakota would cover this assessment area with another important indicator.
Fish tissue was not assessed in nearly one-half of the stream length. While much of this
was due to fish collection and permit issues, decreasing this information gap would
provide important knowledge about risks from mercury in the Upper Missouri Basin.
Obviously, nutrients and sediment impact much of the stream resource in this area
and work targeted to those parameters would accomplish much in stream restoration.
More work pinpointed to the various subregions in the basin would more clearly define
where problems exist. Portions of the basin are heavily row-cropped and likely greatly
impact streams, but they are probably not the only impacted areas.
159
-------
An Assessment of USEPA Region 8 Streams and Rivers
EPA Region 8
Physical Setting
EPA Region 8 consists of the six States of Colorado, Montana, North Dakota,
South Dakota, Utah, and Wyoming. The assessment of this area involved collecting all
the state assessments and presenting them at the level of all states combined. No
indicators were created at this level. The condition of streams for a given bioindicator or
stressor at the state level was applied to the full Region to obtain stream length estimates
for least-disturbed, moderately-disturbed or most-disturbed.
The land cover for the Region as a whole is depicted in Figure 1. There is mostly
cropland and grassland in the east, mountains in the south and northwest, with xeric
regions in the central and southwest. The large urban areas of the Colorado Front Range
and the Wasatch Front in Utah are also clear (red).
V\&ter
Urban
0 Barren
| Forest
Shrubland
| Grassland
Cropland
Wstland
Kilometers
Figure 1. Land cover of EPA Region 8.
160
-------
An Assessment of USEPA Region 8 Streams and Rivers
Extent of Streams
A total of 786 sites were sampled within EPA Region 8. Of these, 430 were
probability sites and 356 were hand-picked as potential reference sites. Four hundred and
four probability sites were used in the final assessment. Approximately 175,851
kilometers of perennial streams are contained within this assessment area (+/- 20,759 km)
according the EMAP-West evaluation; the 404 sites used for assessment represent
143,916 (+/- 10,982) km. Sixty-one sites were denied access by landowners (representing
about 23,270 km) and 17 were physically inaccessible (representing about 8,660 stream
kilometers). About 66,500 kilometers of stream were non-target (either dry or found to
contain impoundments). The location of sites sampled in EPA Region 8 is presented in
Figure 2. The amount of stream length in the mountain, plains, and xeric regions is
depicted in Figure 3.
rvrr
*• •
• *1
•»
•$
SD
••
WY
• •••
-igure 2. Location of sampled sites in EPA Region 8 (black dots represent the
probability sites and blue are hand-picked sites).
161
-------
An Assessment of USEPA Region 8 Streams and Rivers
Assessed Stream Length in EPA Region 8
All Region 8
Mountains
Plains
Xeric
0
20000
40000
60000 80000 100000 120000 140000
Stream Length (km)
Figure 3. Stream length assessed in EPA Region 8 and by bioregion (blue is the stream
length in the entire Region and green represents the stream length in the various
subregions).
Reference Site Determination
Reference and stressed sites were selected in order to develop biological
indicators and derive thresholds for estimating condition. As mentioned in the reference
site discussion in the introduction to this report, reference sites are considered to be the
least-disturbed sites for a given ecoregion.
The original designation for least-disturbed and stressed sites done by EPA-ORD
(Stoddard et al 2005a; Stoddard et al 2005b) was revised by each state using Local
knowledge, and in some cases, locally determined methods. See each state chapter for
discussions on deviations from the ORD method for determining reference sites.
Biotic Indicators
Many different macroinvertebrate and periphyton MMIs were developed to assess
the full region. More details on MMI development can be found in the individual state
chapters and in the EMAP-West Report (Stoddard et al 2005b).
162
-------
An Assessment of USEPA Region 8 Streams and Rivers
Stressor Indicators
Stressors analyzed in this assessment were three chemical (total phosphorus, total
nitrogen, and fish tissue mercury), four habitat (streambed stability, riparian vegetation,
riparian disturbance, and habitat complexity), and two biological (invasive plants and
alien vertebrates). All of these were measures that could give some indication of human
influence to streams and may directly or indirectly impact biological indicators.
Setting Expectations
Thresholds of condition (least- versus most-disturbed) were set for each biological
or stressor indicator using reference (least-disturbed) sites chosen for comparison to the
entire population. Different sets of least-disturbed sites were used depending on the
parameter to judge. Biotic condition was assessed using sets of least-disturbed sites
chosen through the reference site method discussed above.
Sets of least-disturbed sites to assess condition of various stressors were derived
by screening all sites for a number of chemical and habitat parameters excluding the
stressor to be assessed to avoid circularity. Therefore, there is a different set of least-
disturbed sites for each stressor. Since stressors used to determine least-disturbed sites are
removed in the process, the confidence in these sets as reference sites is somewhat
diminished. Therefore the confidence that they truly represent least-disturbed sites is
lower. See individual state chapters for more detail on how thresholds were set in a given
area.
Biological Condition
Using the various macroinvertebrate MMIs created for each state or ecoregion,
83,879 km (58%) of stream length was in least-disturbed condition, 20,633 km (14%)
moderately-disturbed, and 35,295 km (25%) most-disturbed. The amount of stream
length in least-disturbed condition for various bioregions ranged from only 50% in xeric
areas to 55% in the plains and 62% in the mountains. The plains had the highest amount
in most-disturbed condition at 30%. Since large areas of the Region were missing a
predictive model, assessment using O/E scores was not possible at this scale, therefore
only macroinvertebrate MMIs provide full coverage of the Region.
The periphyton MMIs found 61,976 km (43%) least-disturbed, 27,975 km (19%)
moderate, and 32,582 km (23%) most-disturbed. About 15% of stream length was not
assessed using periphyton. The amount of stream length in least-disturbed condition for
various bioregions ranged from only 31% in xeric areas to 42% in the mountains and
49% in the plains. The plains had the highest amount in most-disturbed condition at 25%.
The amount of stream length by condition class for macroinvertebrates and periphyton is
presented in Figure 4.
163
-------
An Assessment of USEPA Region 8 Streams and Rivers
Biological Condition
n
m
E
0)
58%
14%
25%
'3%
43%
19%
23%
15%
10000 20000 30000 40000 50000 60000
Stream Length (km)
70000
80000
90000
100000
Figure 4. Biological condition based on macroinvertebrate and periphyton MMIs (red is
most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is not
assessed).
Indicators of Stress
The amount of stream length in EPA Region 8 in most-disturbed condition for
total phosphorus was 30,742 km (21 %), with 89,459 km (62%) least-disturbed. For total
nitrogen, 19,775 km (14%) of stream length was in most-disturbed condition and a
similar amount of 88,157 km (61%) in least-disturbed condition. Mercury in fish tissue
(all fish samples, regardless of size) at levels >0.1 jag/g (Lazorchak et al 2003) was found
in 25,157 km of stream length and lower than this level in 48,342 km. However, more
than 68,800 km in EPA Region 8 were not assessed. Percentages of streams above the
level varied between bioregions, with less than 9% of mountain streams exceeding 0.1
pg/g. In the plains and xeric regions, 29% and 33%, respectively, were above the
threshold. However, the percentage of stream length below the threshold was similar in
all bioregions at between 32% and 35% of stream length (with of course greatly varying
stream kilometers).
Riparian areas with the least human disturbance were found in 67,647 km of
stream length in the Region, with 46,468 km most-disturbed. For riparian vegetation
cover, 59,376 km was least-disturbed and 22,045 km most-disturbed. Habitat complexity
was in least-disturbed condition in 71,111 km of stream length and 43,153 km most-
disturbed. The streambed stability indicator found 71,580 km in least-disturbed condition,
32,576 km moderate, and 32,427 km most-disturbed (about 5% was not assessed).
164
-------
An Assessment of USEPA Region 8 Streams and Rivers
Phosphorus
Nitrogen
Fish Tissue Hg
Habitat Complexity
Streambed Stability
Riparian Vegetation
Riparian Disturbance
D 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000
Stream Length (km)
-igure 5. Extent of stressors in least, moderate, and most-disturbed condition (red is
most-disturbed, yellow is moderately-disturbed, green is least-disturbed, and gray is not
assessed).
The amount of stream length for each stressor in the various condition classes is
shown in Figure 5. Overall there were relatively similar amounts of stream length in
most-disturbed condition for the various stressors. Riparian disturbance and habitat
complexity stand out somewhat at more than 40,000 km each. However, for all the
others, the most-disturbed condition exists in about 20,000 km or more. Looking at the
results by bioregion, differences are more evident. Total phosphorus is generally lower in
the xeric and mountain regions at 20% of stream length or less, while in the plains it is
32%. The habitat complexity measure has the lowest amount in most-disturbed condition
in mountains at only 19% but over 45% for both the plains and xeric regions. Riparian
measures generally had more extensive most-disturbed conditions in the xeric and plains
and less so in the mountains. Streambed stability in most-disturbed condition was higher
in extent in the plains at 31%, but similar in comparison with total phosphorus in that in
the mountains it was at 20%. Stressors are ranked in order from greatest to lowest extent
in Figure 6.
Stressor Extent
. . _
1—1—1
—
1—-1—-
^ 1 1
HMMU, •—it 1
WTH-»ir ri ' 71
165
-------
An Assessment of USEPA Region 8 Streams and Rivers
Extent of Stressor in Most-Distubed Condition
Riparian Disturbance
32% mummm (
Habitat Complexity
30% , <
Streambed Stability
23' o i—mpi <
Phosphorus
1 S) 1
Fish Tissue Hg
18% 1
Riparian Vegetation
15% ~ 1
Nitrogen
14% i )
10000 20000 30000 40000 50000 60000
Stream Length (km)
Figure 6. Ranking of stressors by stream length in most-disturbed condition.
Two biological stressors were measured in this study, but not presented on the
chart. These were alien vertebrates (mainly fish in this region) and invasive plants. If
more than 10% of the vertebrate individuals captured at a site were alien they were listed
as common, more than 0% but less than 10% was considered "present" and if none were
found they were absent. Alien vertebrates were common in 57,815 km (53%) of stream
length, present in 16,348 km (15%), and absent in 23,726 km (22%). About 10% was not
assessed for this indicator, mainly due to lack of permits to collect fish.
Twelve invasive plants were noted for presence throughout the full EMAP-West
study area. Of those 12, eleven were found within EPA Region 8: common burdock
(Arctium minus), cheatgrass (Bromus tectorum), musk thistle (Carduus nutans), Canada
thistle (Cirsium arvense), common teasel (Dipsacus fullonum), Russian olive (Elaeagnus
angustifolia), leafy spurge (Euphorbia esula), English ivy (Hedera helix), giant reed
(Arundo donax) and reed canary grass (Phalaris arundinacea). These were common
(found at 10-50% of transects) or dominant (found in more than 50% of transects) in 48%
of stream length where sampled and absent in 49%. A total of 122,993 stream kilometers
was assessed for invasive plants (out of 143,916 km).
166
-------
An Assessment of USEPA Region 8 Streams and Rivers
Relative Risk
Nutrients
Streambed Stability
Habitat
Relative Risk
~ Macroinvertebrate MMI
¦ Periphyton MMI
figure 7. Relative risk of stressors to biological indicators in EPA Region 8.
Relative Risk
A relative risk analysis was done for Region 8 assessment area, since this area,
along with the Upper Missouri Basin, were the only areas with enough sites to perform
the analysis. Due to the large amount of correlation between stressors, relative risk should
be assessed based on combinations of stressors (Van Sickle 2008). In this case, the two
nutrient stressors, phosphorus and nitrogen were combined, and three habitat stressors
(riparian disturbance, habitat complexity, and riparian vegetation) were combined into a
general habitat stressor, and streambed stability was left by itself. For the overall nutrient
stressor to be considered "most-disturbed" either phosphorus or nitrogen could be in
most-disturbed condition; for the habitat stressor, two of the three needed to be most-
disturbed to label the habitat overall as most-disturbed. A relative risk score must be
significantly greater than 1.0 to be considered relevant.
Comparing the macroinvertebrate MMI with various stressors, all three stressor
combinations showed a significant response, with nutrients and streambed stability much
stronger than the general habitat stressor (Figure 7). Both nutrients and streambed
stability were around 3, meaning that when there are high nutrients or poor streambed
stability, there is a 3 times greater risk of poor macroinvertebrate condition. The habitat
stressor, however, also showed a significant response with macroinvertebrates, but only
at about 1.7 times greater risk. For periphyton, only nutrients exhibited a significant
relative risk. There was a 2.6 times greater risk of poor periphyton condition when
nutrients were high.
167
-------
An Assessment of USEPA Region 8 Streams and Rivers
Conclusions
For the entire EPA Region 8, analysis of macroinvertebrate and periphyton
indicators resulted in similar total stream length in most disturbed condition, each
approximately 25%. Macroinvertebrate MMIs indicated that nearly three-fifths of stream
length was in least-disturbed condition, while periphyton MMIs indicated 43%. Because
roughly 15% of sites were not assessed (mainly in xeric regions of Utah) with periphyton
this may not be a fair comparison - the amount in least-disturbed condition could be
higher. However, it is not necessarily expected that they would match. In addition,
despite similar stream lengths, individual sites often were found to be in opposite
condition depending on the indicator. For example, of the 106 sites found to be in most-
disturbed condition by the macroinvertebrate MMI, fully one-third were considered least-
disturbed by the periphyton MMI. There was less disagreement when the
macroinvertebrate MMI rated a site in least-disturbed condition. Differences between the
assemblages could mean that the indicators are responding to different stressors, or that
one or the other is under or over indicating impacts.
Two stressors, human riparian disturbance and habitat complexity, ranked the
highest with impacts to over 40,000 stream kilometers in Region 8 (out of a total of
about 144,000 km assessed, almost one-third of stream length). All of the other stressors
were in most-disturbed condition for about 20,000 to 30,000 km. At this geographic scale
there were enough sites to perform a relative risk analysis on the full data. Despite
affecting around 30,000 km or less (lower than many other stressors), nutrients have a
disproportionate affect on both macroinvertebrates and periphyton. There was a 2.5 to 3
times greater risk to macroinvertebrates and periphyton throughout Region 8 from
nutrients. Additionally, streambed stability affected macroinvertebrates at more than 3
times greater risk. Both extent and severity of stressors is important information to obtain
from an assessment. More data is required to perform an analysis of severity or risk, but it
adds an additional perspective. As with many other sub areas within Region 8, nutrients
and sediment have the most impact. A finding that nutrients and sediment are widespread
and important stressors to aquatic systems is not new, but this study supports that
concept.
Throughout the Region, the mountain areas generally had lower extent of stressor
impacts as would be expected with somewhat lower human settlement; however, one
must be careful with this comparison since the areas are judged within by reference sites
suitable to those areas; in other words, poor or good condition in the plains does not equal
that in the mountains.
Recommendations / Data and Information Gaps
A predictive model (or many individual state models) for macroinvertebrates
covering the entire Region would be an important complement to macroinvertebrate
MMIs. Fish as an indicator are problematic in the West due to low diversity, permit and
collection issues, and the prevalence of stocking. In this report they were used as an
168
-------
An Assessment of USE PA Region 8 Streams and Rivers
indicator in a few limited areas. In the future, fish could possibly be used different ways
than in MMIs, such as modeling for species occurrences.
Almost half the stream length in the Region is missing an analysis of fish tissue
mercury. The findings for this indicator revealed some interesting patterns
geographically, so more coverage could be informative. If more widespread sampling is
not possible because of permit and collection issues, targeting popular fishing areas or
fish consumption areas first may be useful.
While two habitat stressors were found to have the greatest extent region wide,
nutrients and excess sediment had fairly large extent and the greatest risk to biota. The
results from this assessment suggest that reduction in nutrient loading and reduction in
transport of fine sediments to streams are the most important in improving the condition
of aquatic biota.
169
-------
An Assessment of USEPA Region 8 Streams and Rivers
Overall Conclusions and Recommendations
EPA Region 8 is extremely diverse in landform and stream types with mountains, plains,
and desert areas, all with very different biota. Some of these areas are used heavily for
agriculture (cropland and/or grazing) and as population centers. Other areas do not receive as
much human use, except on a seasonal or local basis. There are, therefore, diverse impacts to
aquatic systems and stating any generalizations are difficult at best. Despite these differences,
however, impacts can be detected using biological indicators such as macroinvertebrates,
periphyton, and fish when the metrics and indices are designed with ecological differences in
mind. Although there were limitations on how small an assessment unit could be due to sample
numbers, the main goals of using bioindicators by states and others were largely realized along
with a large scale assessment and state-by-state assessments of condition.
This report presents an examination of differing levels of assessment, at the state,
ecoregion, and EPA Region 8 as a whole. Analysis of different assessment units required specific
indicators and larger scale assessments were based on combining smaller scale assessments.
Such an approach allows us to ask questions about biotic condition at the appropriate scale. This
approach also allows states to work within their political boundaries. In this way, the main goal
of the project, to provide estimates of condition throughout these varied areas using biology and
to gain an understanding of the extent and severity (where possible) of common stressors, was
achieved.
Each assessment unit chapter presents the findings on biological condition and extent of
stressors. Many of the individual state chapters were condensed from larger reports which
describe in more detail about what was accomplished in a given state. The more extensive
separate state reports are listed in the references.
Since in most cases, states developed both indicators and thresholds for indicators and
stressors independently, comparisons between states are not recommended. A finding of 30%
most-disturbed condition one state is not necessarily comparable to a similar finding in another
state. This is true for stressor extent as well. The individual state chapter functions as a statement
by that State of the condition and impacts derived through their own processes. The ecoregional,
Upper Missouri Basin and EPA Region 8 scale chapters integrate the state efforts but do not
reconcile these differences. Therefore, the larger scale chapters are the best compilation possible
while not imposing strict rules on how the states would assess their streams. The larger scale
chapters should be read with this concept in mind - a more uniform method for determining
thresholds for indicators and stressors would likely lead to a slightly different outcome at these
scales.
The macroinvertebrate MMIs generally found 20-30% of stream length in most-disturbed
condition regardless of whether the area was mountains, plains, most States, or the Region as a
whole, with the notable exception of the Northern Cultivated Plains, which had much more
stream length as most-disturbed. This is an area of extensive agricultural use and might be
expected to have a larger proportion of impacted streams. Periphyton MMIs were similar to
macroinvertebrate MMIs in the percentage most-disturbed, with a few exceptions (with generally
higher estimates of disturbance than macroinvertebrate indicators). In assessment units where a
170
-------
An Assessment of USEPA Region 8 Streams and Rivers
macroinvertebrate predictive model could be run, the percentage in most-disturbed condition
generally ranged from 10 to 36%.
The stressors representing poor habitat complexity and high riparian human disturbance
had the greatest extent in EPA Region 8, but tended to be higher in extent in the plains and xeric
regions, less so in the mountains. Total phosphorus and excess sediment were in the next tier of
important stressors in extent, with high fish tissue mercury extensive in many areas as well
(especially in the Northern Cultivated Plains). Most stressors had a greater extent in the plains as
opposed to the mountains, but often not much greater.
While habitat issues had the greatest extent Region-wide, a relative risk analysis for both
the full Region and for the Upper Missouri Basin found that nutrients and excess sediment
impacted the biota the strongest. Habitat stressors did not associate as strongly with impacted
biota. It would have been interesting to perform this analysis at state or ecoregion scales, but the
calculations require more sites than were available at those scales.
In summary, surprisingly similar results were found in the amount of stream length in
least- and most-disturbed condition despite the ecoregional differences. An exception was the
Northern Cultivated Plains; a unique area in Region 8 in that most of the landscape is
dramatically altered. It was not surprising, however, that nutrients, some habitat measures, and
sediment rose to the top in extent and also in severity. The large extent in places of high fish
tissue mercury was an interesting finding. However, the threshold used was lower than in some
reports because this is an ecological threshold and does not directly relate to human health. Very
few sites had fish tissue mercury above the 0.3 jig/g human health criteria (which is actually for
methylmercury (U.S. EPA 2001), not total mercury as in this study). Therefore, the findings in
this study are not directly comparable to human health risk, because, aside from the
methylmercury versus total mercury issue, samples were from whole fish, not filets.
Nevertheless, the extent findings at this lower level may signal the need for more site-specific
studies.
Future Needs
A predictive model (or many individual state models) for macroinvertebrates covering
the entire Region would be an important complement to macroinvertebrate MMIs, especially in
the Dakotas. Some of the plains and xeric region MMIs (both macroinvertebrate and periphyton)
need more investigation and development in the future. More reference sites in the plains and the
Colorado Plateau would certainly improve assessment in those areas. More sites overall in any
given area would allow for more relative risk analyses and provide a greater understanding of the
severity, not just the extent of stressors. Fish as an indicator are problematic in the West due to
low diversity, permitting and collection issues, and the prevalence of fish stocking. In this report
they were used as an indicator in a few limited areas. In the future fish could possibly be used in
different ways than in MMIs, such as modeling for species occurrences.
Additional stressors may be important to sample for in some areas and more coverage of
stream length of stressors such as mercury would improve overall assessment. This project did
not attempt to assess all things, since most toxics (fish tissue mercury is an exception) and
171
-------
An Assessment of USEPA Region 8 Streams and Rivers
pathogens were not included. A few metals were sampled, but these had very few exceedances of
criteria throughout the study area. This study did not look at many toxics or pathogen issues
since these are more human health focused instead of the ecological assessment objectives of this
work. Future planned nationwide assessments may fill some of these gaps, although work at the
state level would also be very valuable.
There is a need for better diagnostic tools in some areas where biota are impacted, but the
stressor causing the impairment is unknown. Along with this is a need for a better understanding
of how multiple stressors might interact (relative risk analysis examines only one stressor versus
one indicator). Finally, more landscape efforts to help target sampling to where impacts are
expected will be critical in the future for reducing costs of sampling.
Recommendations
Nutrient and sediment impacts were among the most common and found to be the most
severe to biological communities. Unless more local information points to other stressors, these
are the stressors impacting biota on a widespread basis in EPA Region 8. Efforts to deal with
these would have the most widespread impact environmentally.
Of course there are other stressors not included in this study that are impacting streams,
such as pathogens, localized metals and toxics and these should not be ignored. Additionally,
habitat impacts were found to be widespread. While direct connections from habitat stressors and
harm to biota was not drawn in this work, they may be impacting biota in areas where the
relative risk analysis could not be done or they are functioning as intermediate stressors.
Nevertheless, stream restoration work focused on nutrients and excess sediment would benefit a
great number of aquatic systems in Region 8 States.
172
-------
An Assessment of USEPA Faction 8 Streams and Rivers
References
Bailey, R. C., Norris, R. H. & Reynoldson, T. B. 2004. Bioassessment of Freshwater
Ecosystems: Using the Reference Condition Approach. Kluwer Academic Publishers,
New York.
Barbour, M. T., Stribling, J. B. & Karr, J. R. 1995. Multimetric approach for establishing
biocriteria and measuring biological condition. In Biological assessment and criteria:
tools for water resource planning and decision making. (Davis, W. S. & Simon, T. P.,
Eds), pp. Chapter 6, pg. 63-77. Lewis, Boca Raton, FL.
Colorado Data Book. 2005. http://www.state.co.us/oed/business-development/colorado-
data-book.cfm
Colorado Department of Natural Resources (DNR). 2001. Report on the condition of
Colorado's forests. Colorado Department of Natural Resources, Denver, CO. 21 pp.
Colorado Department of Public Health and Environment. 2007. Colorado EMAP
Ecological Monitoring and Assessment Report. Water Quality Control Division. Denver,
CO. 46 pp.
Frey, D. G. 1977. The integrity of water - an historical approach. In: The Integrity of
Water. (Ballentine, S. K. & Guarala, L. J., Eds), pp. 127-140. U.S. Environmental
Protection Agency, Washington DC.
Hargett, E.G., and Zumberge, J.R. 2006, Redevelopment of the Wyoming Stream
Integrity Index (WSII) for assessing the biological condition of wadeable streams of
Wyoming: Cheyenne, Wyoming Department of Environmental Quality, Water Quality
Division Report. 70 p.
Hargett, E.G., Zumberge, J.R., and Hawkins, C.P. 2005. Development of a RIVPACS
model for wadeable streams of Wyoming: Cheyenne, Wyoming Department of Environ-
mental Quality, Water Quality Division Report. 64 p.
Hargett, E.G., Zumberge, J.R., Hawkins, C.P., and Olson, J.R. 2007. Development of a
RIVPACS-type predictive model for bioassessment of wadeable streams in Wyoming:
Ecological Indicators.
Hawkins, C. P. (In Press). Quantifying biological integrity with predictive models:
comparisons with three other assessment methods. Ecological Applications.
Hawkins, C. P. 2005. Development of a RIVPACS (O/E) Model for Assessing the
Biological Integrity of Montana Streams (Draft). The Western Center for Monitoring and
Assessment of Freshwater Ecosystems, Utah State University, 10 November 2005.
Hawkins, C.P. 2007. Personal Communication. Utah State University
173
-------
An Assessment of USEPA Region 8 Streams and Rivers
Hawkins, C. P., Norris, R. H., Hogue, J. N. & Feminella, J. W. 2000. Development and
evaluation of predictive models for measuring the biological integrity of streams.
Ecological Applications 10, 1456-1477.
Hughes, R. M. 1995. Defining acceptable biological status by comparing with reference
conditions. In Biological Assessment and Criteria: Tools for Water Resource Planning
and Decision Making for Rivers and Streams. (Davis, W. & Simon, T., Eds), pp. Chapter
4, pg. 31-47. Lewis, Boca Raton, FL.
Jessup, B., J. Stribling, and C. Hawkins. 2006. Biological Indicators of Stream Condition
in Montana Using Macroinvertebrates. Tetra Tech, Inc. November 2005 (draft).
Karr, J. R. 1981. Assessment of biotic integrity using fish communities. Fisheries 6, 21-
27.
Karr, J. R. & Dudley, D. R. 1981. Ecological perspective on water quality goals.
Environmental Management 5, 55-68.
Kaufmann, P. R., Levine, P., Robison, E. G., Seeliger, C. & Peck, D. 1999. Quantifying
physical habitat in wadeable streams. EPA Report EPA/600/3-88/021a, U.S. EPA,
Washington, D.C.
Lazorchak, J. M., McCormick, F. H., Henry, T. R. & Herlihy, A. T. (2003).
Contamination of fish in streams of the Mid-Atlantic Region: an approach to regional
indicator selection and wildlife assessment. Environmental Toxicology and Chemistry
22, 545-553.
Longwoods International. 2003. http://www.state.co.us/oed/news/040817tour.html 11-28-
06
Montana Department of Environmental Quality. 2006. Circular DEQ-7 - Montana
Numeric Water Quality Standards. Montana Department of Environmental Quality,
Planning, prevention and Assistance,Helena, Montana.
Montana Department of Environmental Quality. 2008. An assessment of the ecological
conditions of the streams and rivers of Montana using the Environmental Monitoring and
Assessment (EMAP) method. Prepared by Wease A. Bollman and Jennifer A. Bowman,
Rhitron Associates, Inc. Missoula, MT. 95 pp.
Moss, D., M.T. Furse, J.F. Wright, and P.D. Armitage. 1987. The prediction of the
macroinvertebrate fauna of unpolluted running-water sites in Great Britain using
environmental data. Freshwater Biology 17,41-52.
National Climatic Data Center. 2006. http://www.ncdc.noaa.gov
/oa/climate/research/2005/snow0405.html
174
-------
An Assessment of USEPA Region 8 Streams and Rivers
Olsen, A. R., Sedransk, J., Edwards, D., Gotway, C. A., Liggett, W., Rathbun, S.,
Reckhow, K. H. & Young, L. J. 1999. Statistical issues for monitoring ecological and
natural resources in the United States. Environmental Monitoring and Assessment 54, 1-
45.
Omernik, J. M. 1987. Ecoregions of the conterminous United States. Annals of the
Association of American Geographers 77, 118-125.
Peck, D. V., Averill, D. K., Herlihy, A. T., Hughes, R. M., Kaufmann, P. R., Klemm, D.
J., Lazorchak, J. M., McCormick, F. H., Peterson, S. A., Cappaert, M. R., Magee, T. &
Monaco, P. A. 2005a. Environmental Monitoring and Assessment Program - Surface
Waters Western Pilot Study: Field Operations Manual for Non-Wadeable Rivers and
Streams. EPA Report EPA 600/R-05/xxx, U.S. Environmental Protection Agency,
Washington, DC.
Peck, D. V., Herlihy, A. T., Hill, B. H., Hughes, R. M., Kaufmann, P. R., Klemm, D. J.,
Lazorchak, J. M„ McCormick, F. H., Peterson, S. A., Ringold, P. L., Magee, T. &
Cappaert, M. R. 2005b. Environmental Monitoring and Assessment Program - Surface
Waters Western Pilot Study: Field Operations Manual for Wadeable Streams. EPA
Report EPA 600/R-05/xxx, U.S. Environmental Protection Agency, Office of Research
and Development, Washington, DC.
Peterson, D.A., Hargett, E.G., Wright, P.R., and Zumberge, J.R. 2007. Ecological status
of Wyoming streams, 2000-2003: U.S. Geological Survey Scientific Investigations
Report 2007-5130, 32 p.
R Development Core Team (2007). R: A language and environment for statistical
computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN3-900051-07-
0, URL http://www.R-^rqject.org.
Stoddard, J.L., Peck, D.V., Olsen, A.R., Larsen, D.P., Van Sickle, J., Hawkins, C.P.,
Hughes, R.M., Whittier, T.R., Lomnicky, G.A., Herlihy, A.T., Kaufman, P.R., Peterson,
S.A., Ringold, P.L., Paulsen, S.G., and Blair, R. 2005a. Environmental Monitoring and
Assessment Program (EMAP) western streams and rivers statistical summary: U.S.
Environmental Protection Agency Report 620/R-05/006, 1,762 p.
Stoddard, J.L., Peck, D.V., Paulsen, S.G., Van Sickle, J., Hawkins, C.P., Herlihy, A.T.,
Hughes, R.M., Kaufman, P.R., Larsen, D.P., Lomnicky, G.A., Olsen, A.R., Peterson,
S.A., Ringold, P.L., and Whittier, T.R. 2005b. An ecological assessment of western
streams and rivers: U.S. Environmental Protection Agency Report 620/R-05/005,49 p.
Stoddard, J.L., Larsen, D.P., Hawkins, C.P., Johnson, R.K., and Norris, R.H. 2006a.
Setting expectations for the ecological condition of streams—The concept of reference
condition: Ecological Applications, v. 16, p. 1,267-1,276.
175
-------
An Assessment of USE PA Region 8 Streams arid Rivers
Stoddard, I. L., Herlihy, A. T., Hill, B. H., Hughes, R. M., Kaufmann, P. R., Klemm, D.
J., Lazorchak, J. M., McCormick, F. H., Peck, D. V., Paulsen, S. G., Olsen, A. R., Larsen,
D. P., Van Sickle, J. & Whittier, T. R. 2006b. Mid-Atlantic Integrated Assessment
(MAIA)--State of the Flowing Waters Report. EPA Report EPA 620/R-06/001, U.S.
Environmental Protection Agency, Washington, DC.
Suplee, M., R. S. de Suplee, D. Feldman, and T. Laidlaw. 2005. Identification and
Assessment of Montana Reference Streams: A Follow-up and Expansion of the 1992
Benchmark Biology Study. Montana Department of Environmental Quality, Helena, MT.
23p.
Suplee, M.W., A. Varghese, and J.Cleland. 2007. Developing nutrient criteria for streams:
an evaluation of the frequency distribution method. Journal of the American Water
Resources Association. 43(2):453 - 472.
Teply, M. and L. Bahls. 2005. Diatom Biocriteria for Montana Streams. Prepared for the
Montana Department of Environmental Quality by Larix Systems, Inc. of Helena,
Montana. September 2005.
Teply, M. and L. Bahls. 2006. Diatom Biocriteria for Montana Streams - Middle Rockies
Ecoregion. Prepared for the Montana Department of Environmental Quality by Larix
Systems, Inc. of Helena, Montana. February 2006.
Teply, M. and L. Bahls. 2007. Statistical Evaluation of Periphyton Samples from
Montana Reference Streams. Prepared for the Montana Department of Environmental
Quality by Larix Systems, Inc. of Helena, Montana. February 2007.
Tetra Tech, Inc. 2005. Development of Bioassessment Tools for Colorado. Owings Mills,
MD. 46 pp.
U.S. Census Bureau 2000 http://quickfacts.census.gov/qfd/states
U.S. Census Bureau. 2005. http://quickfacts.census.gov/qfd/states/08000.html
U.S. Census Bureau. 2006. http://quickfacts.census.gov/qfd/states/states/46000.html
U.S. EPA. 2000. Mid-Atlantic Highlands Streams Assessment, p. 64. EPA Report
EPA/903/R-00/015, U.S. Environmental Protection Agency, Region 3, Philadelphia, PA.
U.S. EPA. 2001. Water Quality Criterion for the Protection of Human Health:
Methylmercury. EPA Report EPA-823-R-01-001. U. S. EPA Office of Science and
Technology. Washington, D.C. January 2001. 303 pp.
U.S. EPA 2002. Research Strategy Environmental Monitoring and Assessment Program
U.S.EPA 620/R-02/002. July 2002.
176
-------
An Assessment of USEPA Region 8 Streams and Rivers
U.S. EPA. 2006a. Wadeable Streams Assessment—The States Assess the Nation's
Streams: EPA Report 841/B-06/002, 86 p.
U.S. EPA 2006b. The Condition of Headwater Streams in the Mining Belt of the
Southern Rockies Ecoregion of Colorado. U.S. Environmental Protection Agency,
Region VIII, Denver, CO. 47 pp.
Utah Department of Environmental Quality. 2008. Building Tools to Interpret Biological
Data in Utah Final Report. March 2008. 23 pp.
Van Sickle, J. 2008. Combining correlated stressor variables to clarify stressor effects.
Presentation at North American Benthological Society 56th Annual Meeting, May 25-30,
2008, Salt Lake City, UT.
Van Sickle, J., Stoddard, J. L„ Paulsen, S. G. & Olsen, A. R. 2006. Using relative risk to
compare the effects of aquatic stressors at a regional scale. Environmental Management.
Vol. 38:6.
Van Sickle, J., Hawkins, C. P., Larsen, D. P. & Herlihy, A. T. 2005. A null model for the
expected macroinvertebrate assemblage in streams. Journal of the North American
Benthological Society 24, 178-191.
Western Regional Climate Center. http://www.wrcc.dri.edu/inventory/snotelCO.html
Western Regional Climate Center, http://www.wrcc.dri.edu/summarv/climsmco.html
Woods, A. J., J. M. Omernik, J. A. Nesser, J. Shelden, and S. H. Azevedo 1999.
Ecoregions of Montana. (Color poster with map, descriptive text, summary tables, and
photographs): Reston, Virginia. U.S. Geological Survey.
Wright, J.F. 1995. Development and use of a system for predicting the macroinvertebrate
fauna in flowing waters. Australian Journal of Ecology 20, 181-197.
Wright, J. F. 2000. An introduction to RIVPACS. In Assessing the Biological Quality of
Fresh Waters. (Wright, J. F., Sutcliffe, D. W. & Furse, M. T., Eds), pp. 1-24. Freshwater
Biological Association, Ambleside, UK.
Wyoming Department of Environmental Quality. 2001. Water Quality Rules and
Regulations, Chapter 1, Wyoming Surface Water Quality Standards: Cheyenne,
Wyoming, 25 p.
Wyoming Department of Environmental Quality. 2006. Wyoming's Draft 2006 305(b)
State Water Quality Assessment Report and Draft 2006 303(d) List of Waters Requiring
TMDLs: accessed November 9, 2006, at http://deq.state.wv.us/wad/watershed/index.asp
177
------- |