United States
Environmental Protection
Agency
•
Streamflow Duration
Assessment Method
for the Pacific
Northwest
•
.
EPA 910-K-14-001 I November 2015
www.epa.gov/measurements/streamflow-duration-assessment-method-pacific-northwest
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Streamflow Duration Assessment Method for the Pacific Northwest
U.S. Environmental Protection Agency, Region 10
Appropriate Citation: Nadeau, Tracie-Lynn. 2015. Streamflow Duration Assessment
Method for the Pacific Northwest. EPA 910-K-14-001, U.S. Environmental Protection
Agency, Region 10, Seattle, WA
Photo credits - Rob Coulombe, Lindsey Webb, Blake Hatteberg, Howard Bruner, Jim
Wigington, Russ Klassen, Gail Heine, Tracie Nadeau
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Table of Contents
PURPOSE v
ACKNOWLEDGMENTS vi
Section 1: Introduction 1
Method Development and Validation Study 2
Interim Method 2
Validation Study 2
Relevant Definitions 5
Considerations When Assessing Indicators of Streamflow 6
Spatial Variability 6
Reach Selection 6
Recent Precipitation 7
Ditches and Modified Natural Streams 7
Disturbed or Altered Streams 8
Section 2: Conducting Field Assessments 9
Suggested Field Equipment 9
General Guidance for Completing the Field Assessment Form 9
Observed Hydrology 10
Indicators of Streamflow Duration 12
Macroinvertebrate Indicators (1 - 3) 12
Additional Indicators (4 and 5) 15
Ancillary Information 16
Section 3: Drawing Conclusions 18
Appendix A: References Consulted 21
Appendix B: Streamflow Duration Field Assessment Form 27
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- A *
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PURPOSE
The purpose of this manual and
accompanying field assessment form is
to guide natural resource professionals
in evaluating the described indicators of
streamflow to help distinguish between
ephemeral, intermittent and perennial
streams. This rapid assessment method has
been developed and tested for applicability
across Oregon, Idaho, and Washington,
from the humid west side of the Cascade
Mountains to the dry and semi-arid areas
of the Snake River Plain and Basin and
Range Province. The current method,
substantively the same as the Streamflow
Duration Assessment Method for Oregon
(Nadeau 2011), summarizes the three-state
study which supports the application of
the method across the Pacific Northwest,
and thus replaces the 2011 manual with a
regionally consistent manual.
Section 1 contains an introduction to the
method, including method development
and validation, definitions of key terms, and
sources of variability. Section 2 describes
the indicators and provides assessment
guidance. The final section describes how
to draw conclusions based on the assessed
indicators of flow.
This method can be used to distinguish
between perennial, intermittent, and
ephemeral streams, but is primarily designed
to distinguish ephemeral streams from
intermittent and perennial streams in a
single site visit. It provides a scientifically
supported, rapid assessment framework
to support best professional judgment in
a consistent, robust and repeatable way.
While use of this method may inform a more
robust stream assessment, it was specifically
developed for the purpose of determining
streamflow duration and does not provide a
stand-alone assessment of stream function or
condition.
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ACKNOWLEDGMENTS
This method was initially developed in
Oregon and has benefitted greatly from
the input of many, as previously described
(Nadeau 2011), on the path to becoming
applicable across the Pacific Northwest. It
is a data driven method that results from
a validation study conducted in Oregon,
Idaho, and Washington. A committed group
of colleagues helped make the four year
validation study (Nadeau et al. 2015) a
reality: Jim Wigington, Scott Leibowitz, Ken
Fritz, Joe Ebersole, Randy Comeleo (EPA),
and Rob Coulombe (CSS-Dynamac). Rob
Coulombe and the Dynamac crew—Blake
Hatteberg, Lindsey Webb, Shawn Majors,
Rachel LovellFord, and Howard Bruner—
with their extensive time in the field at 264
study streams in the three-state area, were
particularly instrumental in improving the
on-the-ground usability of the method. We
are grateful to colleagues across the Pacific
Northwest who provided local knowledge
for study site reconnaissance and/or
additional hydrological observations at study
streams during the course of the study: John
Olson, Jess Jordan, Yvonne Vallette, Linda
Storm, Jim Zokan, and Tina Tong.
Celeste Mazzacano, Scott Hoffman Black,
and Michele Blackburn of the Xerces
Society for Invertebrate Conservation
reviewed the literature and current
understanding of aquatic macroinvertebrates
as indicators of streamflow duration in
Oregon, Idaho, and Washington streams
(Mazzacano and Black 2008; Blackburn
and Mazzacano 2012) to identify the
perennial indicators presented in Table 1,
as well as produced the associated aquatic
macroinvertebrate field guide for use with
this method: www.epa.gov/measurements/
streamflow-duration-assessment-method-
pacific-northwest#documents.
Jess Jordan (U.S. Army Corps of Engineers)
and Chris Rombough (Rombough
Biological) developed the herpetofauna
water-dependent life history stages presented
in Table 2. Shannon Hubler (Oregon
Department of Environmental Quality)
provided data from ODEQ's statewide
stream monitoring database.
With sincere thanks to all,
Tracie Nadeau, U.S. EPA Region 10
Portland, Oregon
nadeau.tracie@epa.gov
Streamflow Duration Assessment Method for the Pacific Northwest
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Section 1: Introduction
A stream* can be described as a channel
containing flowing surface water including:
storm/low - increased streamflow
resulting from the relatively rapid runoff
of precipitation from the land as interflow
(rapid, unsaturated, subsurface flow), overland
flow, or saturated flow from surface water
tables close to the stream channel, or;
base/low - flow resulting from ground water
entering the stream or sustained melt water
from glaciers and snowmelt (observed during
long gaps between rainfall events), or;
a combination of both stormflow
and baseflow, and;
contributions of discharge from upstream
tributaries as stormflow or baseflow, if present.
*Note: For the purposes of this method
the descriptor 'stream' is attached to the
channel, and applies regardless of whether
flow dries up seasonally or otherwise.
Duration, frequency, and timing of
streamflow or drying, as well as flow
magnitude, are fundamental properties of
streams (Poff and Ward 1989; Winter et
al. 1998) which can influence the structure
and function of stream ecosystems (e.g.,
Chadwick and Huryn 2007; Fritz et al.
2008b; Austin and Strauss 2011; Datry
2012). Watershed geology, climate,
topography, soils, vegetation and human
activities can all influence streamflow
(Winter et al. 1998; Winter 2007). Water
to support streams can originate from
numerous sources within a watershed
including overland flow from rainfall or
snowmelt, shallow subsurface flow through
the unsaturated zone, and ground-water
discharge (Winter 2007). Streams may
be perennial, intermittent or ephemeral.
Perennial streams flow year-round during a
typical year, receiving appreciable quantities
of water from numerous sources but with
consistent groundwater inputs required
throughout the year (Winter et al. 1998;
Winter 2007). In cases where groundwater
aquifers are unable to supply sufficient
quantities of water, intermittent streams
cease to flow during dry periods (Mosley
and McKerchar 1993; Rains and Mount
2002; Rains et al. 2006). Ephemeral streams
flow only in direct response to precipitation
including rainstorms, rain on snow
events, or snowmelt. They do not receive
appreciable quantities of water from any
other source, and their channels are, at all
times, above local water tables (Gordon et
al. 2004; McDonough et al. 2011).
As a stream flows from its origin, water
may be derived primarily from stormflow,
baseflow, or some combination of the two.
Streams typically continue to accumulate
water from stormflow, baseflow and other
tributaries as they flow downstream. As
streams accumulate flow they commonly
transition along a gradient from ephemeral
to intermittent and perennial, but sometimes
quickly transition from ephemeral to
perennial in high gradient systems, or
transition from perennial to ephemeral or
to total cessation of surface flow. Often
these changes are gradual and may not be
obvious to the casual observer. There are,
however, indicators of streamflow that can
be used to characterize the flow duration
of a stream along a particular reach as
ephemeral, intermittent or perennial. In this
manual, duration encompasses the concept
of the cumulative time period of flow
over the course of a year, which may vary
interannually with climate, groundwater
withdrawal or streamflow diversion, and
other water use patterns. This manual
presents an indicator-based method for
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assessing Streamflow duration in the Pacific
Northwest.
This method and accompanying assessment
form are designed to assist the user
in distinguishing between ephemeral,
intermittent and perennial streams
throughout the Pacific Northwest. Stream
systems can be characterized by interactions
among hydrologic, geomorphic (physical)
and biological processes. These attributes,
or dominant processes, vary along the
length of a stream related to flow duration
(Figure 1). To identify the indicators and
apply the information presented in this
manual to determine Streamflow duration
classes of streams, the evaluator should have
experience making field observations in
streams.
FIGURE 1. Hydrologic and geomorphic characteristics in
relation to drainage area (FISRWG 1998)
Do position
Drainage Area (—downstream distance3)
Method Development and
Validation Study
Interim Method
The Streamflow Duration Assessment
Method was initially developed for Oregon
through best professional judgment (BPJ)
and results of a single season field test
including more than 170 streams from
both the humid and semi-arid sides of
the Cascade Range. The Interim Method
(Topping et al. 2009) uses ordinal scoring
of 21 geomorphic, hydrologic, and biologic
stream attributes based on abundance and
prominence. Conclusions of Streamflow
duration in the Interim Method are based
on the additive score of the assessed
stream attributes compared to threshold
values that separate perennial, intermittent
and ephemeral classes. In addition, the
Interim Method classifies streams as at
least intermittent (i.e., intermittent or
perennial) based on the presence of Single
Indicator measures: fish, or water-dependent
life stages of specific herpetological and
macroinvertebrate species.
The Interim Method was made available to
allow practitioners such as stream ecologists,
aquatic ecologists, and hydrologists the
opportunity to provide comment on their
experiences using the method during a two-
year field validation study of the method in
Oregon.
Validation Study
This section summarizes relevant validation
study conclusions (Nadeau et al. 2015)
Phase I, Oregon
To meet our objectives of developing a rapid
Streamflow duration assessment method
that is consistent, robust, and repeatable,
we undertook a two-year field validation
Streamflow Duration Assessment Method for the Pacific Northwest
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study of the Interim Method. The study
included 178 streams ranging across the
hydrologic settings of Oregon, with an
approximately equal distribution of streams
from the humid west and semi-arid east side
of the Cascade Range, and in the perennial,
intermittent, and ephemeral classes. Study
design maximized representation of a
diversity of hydrologic landscapes, based
on a hydrologic classification framework
that includes indices of annual climate,
seasonality, aquifer permeability, terrain, and
soil permeability (Wigington et al. 2013).
Method evaluation compared results with
actual streamflow duration classes.
The first phase of the study addressed
several primary questions: 1) What is
the accuracy of the Interim Method? 2)
Is it equally applicable in different (wet/
dry) seasons? 3) Is it equally applicable in
different hydrologic landscapes across the
state? 4) Are these 21 stream attributes the
most predictive indicators of streamflow?
5) Can results be improved by developing
an alternative method (statistical analysis of
data)?
The study included both wet and dry season
sampling; in the Pacific Northwest, where
the delivery of precipitation is generally
greatest during the winter months, these
correspond to wet winter/spring and dry
summer seasons. Supplemental data were
also collected at each site, particularly
for those indicators that were considered
problematic.
The Interim Method agreed with the
known streamflow duration class for 62%
of Oregon observations. The accuracy rate
for distinguishing between ephemeral and
'at least intermittent' (i.e., intermittent or
perennial) streams was 81%. The high
error rate of the Interim Method as applied
in Oregon highlighted the need for an
alternative method to more accurately
determine streamflow duration. Analyses of
the Oregon data found that a subset of the
Interim Method and supplemental indicators
appeared to have the strongest explanatory
power in separating the perennial,
intermittent, and ephemeral stream classes.
Based on analyses of the Oregon data, the
Revised Method was developed. Comprised
of five indicators-wetland plants in/near
streambed, reach slope, and three aquatic
macroinvertebrate indicators, the Revised
Method correctly classified 307 of the 356
Oregon observations, which is 86% correct
compared with 62% accuracy of the Interim
Method. Additionally, accuracy rates for
distinguishing between ephemeral and 'at
least intermittent' classes (i.e., intermittent
or perennial) rose from 81% to 95% with
the Revised Method. The Revised Method
was significantly more accurate (p < 0.0001)
than the Interim Method for predicting all
three streamflow classes and for 'at least
intermittent' accuracy.
The Revised Method subsequently became
the basis for the Final Streamflow Duration
Assessment Method for Oregon (Nadeau
2011), in which the five indicators are
evaluated using a decision-tree, similar to
using a dichotomous key. Additionally, the
presence of certain vertebrate organisms that
require the sustained presence of water for
their growth and development are included
as Single Indicators that a stream has at least
intermittent flow.
Phase II, Idaho and Washington
In the second phase, we evaluated the
regional applicability of the methods
developed in Oregon by testing the Interim
and Revised methods on 86 study reaches
across a variety of hydrologic landscapes,
and stream types, in Washington and Idaho.
As in the first phase of the study, study
streams were tested in both wet and dry
seasons, and method evaluation compared
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results with actual streamflow duration
classes. The Revised Method correctly
classified 84% of observations from the
three-state study area (see inside front
cover map) and distinguished between
ephemeral and 'at least intermittent' with
94% accuracy, compared with 62% overall
accuracy and 82% 'at least intermittent'
accuracy of the Interim (BPJ) Method.
During this phase of the study, we also
compared the Revised Method, which was
developed from Oregon data alone, with
a similar approach (Combined Method)
that was based on combined field data
from Oregon, Washington, and Idaho. The
Combined Method, which required two
additional indicators, did not significantly
outperform the Revised Method, so we
ruled it out as providing an improved on-
the-ground streamflow duration assessment
method for the Pacific Northwest.
Relevant Conclusions
Based on results of our three-state study
the Revised Method, already in use in
Oregon, is the method described herein as
the Streamflow Duration Assessment Method
for the Pacific Northwest. This decision-
tree method (see Section 3) is based on
stream attributes—four biological and one
physical—that are measurable, rather than
subjective. Developed through statistical
analyses of field data, it provides a more
simplified approach with significantly higher
accuracy than the additive, weighted scale
Interim Method.
Because of the diverse hydrology,
climatic regimes, and distinct winter-wet
and summer-dry seasons of the Pacific
Northwest, we also explored the accuracy of
the compared methods in different regions,
climate classes, and seasons. The current
method consistently outperforms the Interim
Method in all categories. Performance of
the current method does vary somewhat
in different hydrological settings and at
different times; for instance, it performs
better during the spring for semiarid and
very wet climate classes, while classification
is more accurate during the fall for wet
climates. However, overall accuracy for
determining 'at least intermittent' status is
nearly 90% or greater in all categories.
Examining the accuracy of Single
Indicators—organisms that require the
sustained presence of water for their growth
and development—at all study sites showed
that while the absence of Single Indicator
measures is not indicative of streamflow
duration, their presence is strongly
predictive. The presence accuracy1 for fish
was 100%, and that of water dependent
herpetological life history stages (Table
2) was 97%. This means that 100% of the
time that fish were found at a study stream,
the stream was intermittent or perennial,
and 97% of the time that the described
herpetological organisms (Table 2) were
found at a study stream, that stream was
likewise at least intermittent. In other words,
while the classes of organisms that make
up the Single Indicator measures are often
not found in streams assessed as perennial
or intermittent, when they are found they
are a very accurate indication of perennial
or intermittent status. This confirms their
usefulness as indicators determining a
stream is 'at least intermittent.'
Finally, we calculated user accuracies—
accuracy of the method when applied
by a user in the field—using data from
all study reaches. For all stream types—
ephemeral, intermittent, and perennial—user
accuracies were higher for the Streamflow
Duration Assessment Method for the Pacific
Northwest than for the Interim Method. User
accuracy was 92% for the current method in
determining the ephemeral class of streams.
1 the number of observations where the indicator group was present
and the actual streamflow duration class was at least intermittent,
divided by the total number where the indicator was present.
Streamflow Duration Assessment Method for the Pacific Northwest
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There was also a high level of repeatability
between duplicate assessments (n=35), but
that may be due, in part, to the level of field
crew training in the study.
Relevant Definitions
As used by this method:
Channel is an area that contains
flowing water (continuously or not)
that is confined by banks and a bed.
Dry Channel is an area confined by banks
and a bed that at times contains flowing water,
but at the time of assessment does not contain
flowing water (it may contain disconnected
pools with no sign of connecting flow).
Wet Channel is an area confined by banks
and a bed that contains flowing water at the
time of assessment (flow may be interstitial).
Ephemeral Stream flows only in direct
response to precipitation. Water typically
flows only during and shortly after large
precipitation events. An ephemeral stream
may or may not have a well-defined channel,
the streambed is always above the water
table, and stormwater runoff is the primary
source of water. An ephemeral stream
typically lacks biological, hydrological and
in some instances physical characteristics
commonly associated with the continuous
or intermittent conveyance of water.
Groundwater occurs at the subsurface
under saturated conditions and contains
water that is free to move under the
influence of gravity, often horizontally
to stream channels when a confining
layer blocks downward percolation.
Hyporheic Zone is the zone under and
adjacent to the channel where stream
water infiltrates, mixes with local and/or
regional groundwater, and returns to the
stream. The dimensions of the hyporheic
zone are controlled by the distribution and
characteristics of alluvial deposits and by
hydraulic gradients between streams and
local groundwater. It may be up to two
to three feet deep in small streams, and is
the site of both biological and chemical
activity associated with stream function.
Intermittent Stream is a channel that
contains water for only part of the year,
typically during winter and spring
when the streambed may be below the
water table and/or when snowmelt from
surrounding uplands provides sustained
flow. The channel may or may not be well-
defined. The flow may vary greatly with
stormwater runoff. An intermittent stream
may lack the biological and hydrological
characteristics commonly associated with
the continuous conveyance of water.
Normal Precipitation is defined as the
30-year average, provided by National
Oceanographic and Atmospheric
Administration National Climatic
Data Center, computed at the end of
each decade. These data are available
as annual and monthly means.
Perennial Stream contains water
continuously during a year of normal
rainfall, often with the streambed located
below the water table for most of the
year. Groundwater supplies the baseflow
for perennial streams, but flow is also
supplemented by stormwater runoff and
snowmelt. A perennial stream exhibits the
typical biological, hydrological, and physical
characteristics commonly associated with
the continuous conveyance of water.
Stream Origin is the point where flow first
appears on the land surface with enough
force to disturb the substrate creating a
lasting sign of flow. Stream origins are
often wetlands, springs, seeps or headcuts.
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Swales can be wetlands or uplands (when
assessed under the USAGE 1987 Wetlands
Delineation Manual or appropriate Regional
supplements) and primarily serve as a
vegetated flow path occurring in a slight
depression in the landscape but lacking
differentiation between bed and bank.
Swales often connect uplands to wetlands
or streams, connect wetlands together, or
connect upstream and downstream reaches
of small streams that flow through a
colluvial fan or an abrupt change in grade.
Thalweg is the deepest part of a stream
channel and the last part of the stream to
contain flowing water as a stream dries
up. As used in this method, the thalweg
comprises the "lowest flow" pathway
and typically spans approximately
5 to 20% of the channel width.
Water Table is the surface elevation
of the saturated zone below which all
interconnected voids are filled with
water and at which the pressure is
atmospheric, commonly identified as
the top of the local (i.e., floodplain)
or regional groundwater aquifer.
Considerations When Assessing
Indicators of Streamflow
Spatial Variability
Spatial variation in stream indicators occurs
within and among stream systems. Sources
of variation between stream systems are
due primarily to physiographic province
(geology and soils) and climate (seasonal
patterns of precipitation, snowmelt, and
evapotranspiration). For example, riffles
and pools result from in-channel structures
and these structures can vary between rocks
and boulders in the mountains and roots
and wood debris in the alluvial valleys. The
method was designed to apply to all stream
systems within the diverse hydrologic
landscape regions ofthe Pacific Northwest.
A substantial amount of variability can also
occur along the length of a given stream
system. Common sources of variation within
a stream system include:
• Longitudinal changes in stream indicators
related to increasing duration and volume
of flow. As streams gain or lose streamflow,
the presence of indicators changes.
• Longitudinal changes due to variables such
as channel gradient and valley width, which
affect physical processes and thus may
directly or indirectly affect indicators.
p Temporal variation of flow related to seasonal
precipitation and evapotranspiration pattern. For
instance, in western Oregon the strong seasonal
rainfall pattern - several months of wet weather
followed by several months of dry weather
- supports the establishment of intermittent
streams. Due to these long periods of rain many
of the intermittent streams in western Oregon
may carry close to the yearly discharge associated
with a perennial stream of the same size.
• Transitions in land use, for instance from
commercial forest to pasture/grazing,
from pasture grazing to cultivated farm,
or cultivated farm to an urban setting.
• The size of the stream; streams develop
different channel dimensions due to
differences in flow magnitude, landscape
position, land use history, and other factors.
Reach Selection
This manual lays out a method for assessing
indicators of streamflow duration. However,
flow characteristics often vary along the
length of a stream, resulting in gradual
transitions in flow duration. Recognizing
that in many streams flow duration exists on
a continuum, choosing the reach on which
to conduct an assessment can influence the
resulting conclusion about flow duration.
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Assessments should be made for a
representative reach, rather than at one point
of a stream. A representative reach for
stream assessments is equivalent to 35 - 40
channel widths of the stream (Peck et al.
2006). Reach length is measured along the
thalweg. For narrow streams, the length of
the assessment reach should be a minimum
of 30 meters. If the assessment reach is near
a culvert or road crossing, the assessment
reach should begin a minimum of 10 meters
from the culvert or road crossing feature.
Assessments should begin by first walking
the length of the channel, to the extent
feasible, from the stream origin to the
downstream confluence with a larger stream.
This initial review of the site allows the
evaluator to examine the overall form of
the channel, landscape, and parent material,
and variation within these attributes as the
channel develops or disappears upstream
and downstream. We recommend walking
alongside, rather than in, the channel for
the initial review to avoid unnecessary
disturbance to the stream and maximize
the opportunity to observe single indicator
organisms (i.e., fish and herpetological
species). Walking the channel also allows
the assessor to observe characteristics of
the watershed such as land use and sources
of flow (e.g., stormwater pipes, springs,
seeps, and upstream tributaries). Once these
observations are made, the assessor can
identify the areas along the stream channel
where these various sources (stormflow,
tributaries or groundwater) or sinks (alluvial
fans, abrupt change in bed slope, etc.)
of water may cause abrupt changes in
flow duration. Similarly, the assessor can
identify if the stream segment in question is
generally uniform or might best be assessed
as two or more distinct reaches.
For some purposes (e.g., regulatory)
the reach in question will often be
predetermined by property ownership or
proposed activities; the above process for
assessing the stream should be followed
to the extent possible, and if the reach
in question is generally uniform one
assessment is appropriate. If the reach
in question is not uniform, two or more
assessments are recommended to fully
describe the changes along the reach.
Regardless of the number of reaches
assessed, decisions should be made in
conjunction with best professional judgment
to reach a conclusion on flow duration as
ephemeral, intermittent, or perennial.
Recent Precipitation
The rate and duration of flow in stream
channels is influenced by climate and by
recent weather. Recent rainfall can influence
the presence of indicators. Evaluators should
note recent rainfall events on the assessment
form, and consider the timing of field
evaluations in assessing the applicability of
individual indicators.
Ditches and Modified Natural Streams
This method can be used, in combination
with best professional judgment, to assess
the flow duration of natural streams,
modified natural streams, and ditches dug in
wetlands or uplands.
When assessing a reach that is a ditch or
modified natural stream, it is important to
walk the entire reach and locate the inflow
point or origin as well as the downstream
terminus of flow (most often a confluence
with another channel). Similarly, any
disturbance or modifications to the stream
channel should be noted on the assessment
form, especially if it affects applicability
of assessment indicators. For highly
modified streams, an alternative assessment
method may be necessary to identify flow
duration. Visiting the site multiple times
or conducting hydrologic monitoring may
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also be necessary. For all assessments,
disturbances or modifications to the
stream or its catchment that may affect
the presence of the streamflow duration
indicators should be noted.
Disturbed or Altered Streams
Assessors should be alert for natural or
human-induced disturbances that affect
streamflow duration and/or the presence
of indicators. Streamflow duration can
be directly affected by flow diversions,
urbanization and stormwater management,
septic inflows, agricultural and irrigation
practices, vegetation management, or other
activities. The presence of indicators can be
affected by changes in streamflow, and can
also be affected by disturbances that may not
substantially affect streamflow (for instance,
grading, grazing, recent fire, beaver activity,
riparian management, culvert installation,
and bank stabilization). Such disturbances
should be described in the "Notes" section
of the field assessment form. Similarly,
natural sources of variation should also be
noted such as fractured bedrock, volcanic
parent material, recent or large relic colluvial
activity (landslides or debris flows), and
drought or unusually high precipitation.
Urbanized and impaired streams
experiencing multiple stressors may be poor
in biologic species, raising concerns about
the effective application of this method in
those situations given the importance of
macroinvertebrate indicators in drawing
conclusions. A query of the Oregon
Department of Environmental Quality's
statewide monitoring data of primarily
perennial streams, which includes the most
impaired streams in the state, indicated
that of more than 2000 macroinvertebrate
samples collected, all had at least one
mayfly (Ephemeroptera) individual.
Additionally, only 37 samples had less than
6 mayfly individuals; these low counts could
be due to very high levels of disturbance or
sampling error.2 Based on these data, this
method should be widely applicable, except
in extreme instances of disturbance.
Shannon Hubler, Oregon Department of Environmental Quality, June 2011
Streamflow Duration Assessment Method for the Pacific Northwest
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Section 2: Conducting Field Assessments
Suggested Field Equipment
• This manual, associated assessment
forms, and an all-weather notebook.
m Global Positioning System (GPS) - used to
identify the boundaries of the reach assessed.
• Clinometer - used to measure channel slope.3
• Tape measure - for measuring
reach width and length.
• Kicknet or small net and tray - used to
sample aquatic insects and amphibians.
m Hand lens - to assist with macroinvertebrate
and plant identification.
• Camera - used to photograph
and document site features.
• Polarized sun glasses - for eliminating
surface glare when looking for fish,
amphibians, and macroinvertebrates.
• Shovel, rock hammer, pick or other digging
tool - to facilitate hydrological observations/
determination of hyporheic flow.
m Macroinvertebrate field guides (e.g.,
Macroinvertebrate Indicators ofStreamflow
Duration for the Pacific Northwest: Companion
Field Guide4, Blackburn and Mazzacano,
2012; Stream Insects of the Pacific Northwest,
Edwards, 2008; Macroinvertebrates of the Pacific
Northwest, Adams and Vaughan, 2003).
• Hydrophytic plant identification guides (e.g.,
Wetland Plants of Oregon and Washington,
Guard, 1995; A Field Guide to Common Wetland
Plants of Western Washington and Northwest
Oregon, Cooke, 1997) and current National
Wetland Plant List for indicator status.5
• Herpetological field guides (e.g.,
Amphibians of Oregon, Washington and
British Columbia, Corkran and Thorns,
1996; A Field Guide to Western Reptiles
and Amphibians, Stebbins, 2003).
3 Channel slope can also be determined from topographic maps or surveys.
4 Developed for use with this method, available at: http://www.epa.gov/
regionl0/pdf/water/sdam/macroinvertebrate_fieldjguide.pdf
5 Available at: http://rsgisias.crrel.usace.army.mil/NWPL/
General Guidance for Completing
the Field Assessment Form
The Streamflow Duration Assessment
Method for the Pacific Northwest relies upon
the assessment of five indicators of flow
duration and on the assessor's understanding
of the site. As with wetland delineation,
for best results we recommend that the
method be applied during the growing
season. As described in the Ditches and
Modified Natural Streams section above, be
aware that modifications to the site or areas
upstream of the site may affect the presence
of the indicators. Similarly, natural variation
such as interannual variation in precipitation
can affect the presence of the indicators used
in this method. Therefore, it is important
to accurately complete the entire field
assessment form, including information
for date, project, evaluator, waterway
name and location, recent precipitation,
observed hydrologic status, and channel
width.
If the stream does not have a defined channel
(i.e., bed and banks are not apparent),
estimate the width of the flow path and
describe in the "Additional Notes" section.
Any other relevant observations should
also be recorded in the "Additional Notes"
section of the form. These may include the
local geology, runoff rates, hydrologic unit
codes, evidence of stream modifications
or hydrologic alterations upstream of the
assessment area (e.g., dams, diversions,
stormwater discharge), and recent land
clearing activities upstream. All pertinent
observations should be recorded on the
form, including a clear and repeatable way
of identifying the boundaries of the reach
being assessed and the reasons for choosing
those boundaries.
November 2015
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Observed Hydrology
Observed hydrology in the assessment
reach informs determination of streamflow
duration. The field evaluator should record
hydrological observations describing
percentage of assessment reach with surface
flow, percentage of reach with any flow
(surface or hyporheic), and number of pools
in the reach in the designated area of the
assessment form.
Stream reach flow
• Observe the stream for the entire
length of the assessment reach.
p Visually estimate the percentage of the reach
length that has flowing surface water.
p Estimate the percentage of the reach length
that has flowing surface water or sub-
surface (hyporheic) flow (see below).
p If there is uncertainty about how to best
characterize a particular assessment reach,
specific observations should be described
on the assessment form, using diagrams
or pictures in support of observations.
FIGURE 2. Examples of recording hydrological observations (figure: R. Coulombs)
Flow
Flowing surface water in
the upper 70% of reach
upper reach boundary
Flow
A
Lower reach boundary
2A:
Recorded observation
% of reach with surface flow = 70%
% of reach with any flow = 70%
isolated pools = 0
Flowing surface water in
the upper 70% of reach
upper reach boundary
Flowing surface water ir
the lower 10% of reach
Lower reach boundary
26:
Recorded observation
YO of reach with surface flow = 80%
% of reach with any flow = 100%
isolated pools = 0
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Streamflow Duration Assessment Method for the Pacific Northwest
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Figure 2C: There is pooling (above left) near the bottom of the study reach; surface water is flowing into this area, but there is none
flowing out and there is no sign of flowing water below the pooled area (above right).
Recorded observation
% reach with surface flow = 90% (no observed surface flow along the lowest 10% of the reach)
% reach with any flow =90% (there was no evidence ofhyporheic flow below the pooled area or immediately below the reach)
Figure 2D: There is NO evidence of flowing water into or out
of this long pool; yellow lines are the assessment reach
boundaries.
Recorded observation
% of reach with surface flow = 0%
% of reach with any flow = 0%
# of pools = 1
Observation comment - "One long stagnant
pool covering most of the reach."
Hyporheic flow
Because it occurs below the surface of
the streambed, hyporheic flow is not
easily observed. However, there are
some observable signs of the presence of
hyporheic flow, including:
• Flowing surface water disappearing
into alluvium deposits, and reappearing
downstream. This is common when there is
a large, recent alluvium deposit created by a
downed log or other grade-control structure.
• Water flowing out of the streambed
(alluvium) and into isolated pools.
p Flowing water below the surface of the
streambed, observed by moving streambed
rocks or digging a small hole in the streambed.
• At sites where the observed surface flow is less
than 100%, look for evidence ofhyporheic
flow and use best professional judgment
in entering observations on the data form.
Figure 2 (A - D) provides examples of how
to record hydrological observations.
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Indicators of Streamflow Duration
Identification of stream type is accomplished
by evaluating five indicators of Streamflow
duration, which are then considered
sequentially using a decision-tree. Natural
disturbances such as recent landslides and
wildfires could mask the presence of some
indicators. Similarly, human modifications
to streams, such as toxic pollution or cement
lined channels, could also preclude some
indicators from forming. These situations
should be explained in the "Notes" section
of the assessment form.
Indicator assessment is based on direct
observation and should not include
predictions of what could or should be
present. Disturbances and modifications
to the stream should be described in
the "Notes" section of the assessment
form and taken into consideration when
drawing conclusions from the information
collected. It is also important to explain
the rationale behind conclusions reached,
and when necessary that rationale should
be supported with photos and other
documentation of the reach condition and
any disturbances or modifications that were
taken into consideration. Stream reaches
are categorized as perennial, intermittent, or
ephemeral on the basis of five indicators. To
apply this method, all indicators should first
be evaluated, and the field assessment form
(Appendix B) completed. The indicators
are then considered sequentially, similar
to using a dichotomous key (see Drawing
Conclusions). The answers to each step of
the key determine the relevant indicator for
the next step.
Macroinvertebrate Indicators (1 - 3)
Many macroinvertebrates require the
presence of water, and in many cases
flowing water, for their growth and
development. Such macroinvertebrates
are good indicators of Streamflow duration
because they require aquatic habitat to
complete specific life stages. For example,
clams cannot survive outside of water, in
contrast to some stoneflies or alderflies that
resist desiccation in some seasons of the
year by burrowing into the hyporheic zone.
Some macroinvertebrates can survive short
periods of drying in damp soils below the
surface, or in egg or larval stages resistant
to drying. Others are quick to colonize
temporary water and complete the aquatic
portion of their life cycle during the wettest
part of the year when sustained flows are
most likely.
The three macroinvertebrate indicators used
here are assessed within the defined reach
using a single search. The assessment for all
three macroinvertebrate indicators requires
a minimum 15 minute search time to sample
the range of habitats present, including:
water under overhanging banks or roots, in
pools and riffles, accumulations of organic
debris (e.g., leaves), woody debris, and the
substrate (pick up rocks and loose gravel,
also look for empty clam shells washed up
on the bank in the coarse sand).
A kicknet or D-frame net and a hand lens are
required to collect and identify specimens.
Begin sampling at the most downstream
point in the assessment reach and move
upstream to each new sampling site. Place
the kicknet perpendicular against the
streambed and stir the substrate upstream
of the net for a minimum of one minute,
empty contents of the net into a white
tray with fresh water for counting and
identification. Many individuals will appear
the same until seen against a contrasted
12
Streamflow Duration Assessment Method for the Pacific Northwest
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Figure 3: Example of caddisfly casings: A) the Limnephilidae
family, and B) abundant casings from an intermittent stream
in the Ochoco Mountains, central Oregon.
color background, and some bivalves and
other macroinvertebrates can be pea-sized
or smaller. Sweeping grass and shrubs in the
riparian zone immediately adjacent to the
active channel with a funnel-shaped insect
net may collect emergent aquatic insects
such as stoneflies or caddisflies.
Dry channels: The reach should first be
walked to ascertain whether it is completely
dry, or if areas of standing water where
aquatic macroinvertebrates may collect
remain. Focus the search on areas of
likely refuge such as any remaining pools
or areas of moist substrate for living
macroinvertebrates, the sandy channel
margins for mussel and aquatic snail shells,
and under cobbles and other larger bed
materials for caddisfly casings. Casings
of emergent mayflies or stoneflies may be
observed on dry cobbles or on stream-side
vegetation. In summary, we recommend
a sampling methodology consistent to
that recommended by the Xerces Society
report on using aquatic macroinvertebrates
as indicators of streamflow duration
(Mazzacano and Black 2008).
Searching is complete when:
at least 6 samples have been collected across
the range of habitat types and a minimum
of 15 minutes of effort expended (not
including specimen identification time), or;
all available habitat in the assessment reach
has been completely searched in less than 15
minutes. In dry stream channels with little bed/
bank representation and little habitat diversity, a
search maybe completed in less than 15 minutes.
The 15 minute estimate for searching
does not reflect time spent on identifying
individuals, rather it is wholly focused
on the searching and gathering effort. It
is important to complete the search for
macroinvertebrates, as described above,
prior to identifying taxa necessary to
evaluate the three indicators. The data
November 2015
13
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sheet includes an area for noting observed
macroin vertebrates.
Macroinvertebrate identification:
Macroinvertebrate Indicators ofStreamflow
Duration for the Pacific Northwest:
Companion Field Guide (Blackburn and
Mazzacano 2012) developed specifically
for use with this method provides a useful,
compact field guide for identification of
aquatic macroinvertebrates, including as
indicators of streamflow duration in Pacific
Northwest streams. It is available at: http://
www.epa.gov/region 10/pdf/water/sdam/
macroinvertebrate_field_guide
Notes:
These indicators do not differentiate
between live organisms and shells, casings,
and exuviae (i.e., the external coverings of
larvae and nymphs). In other words, mussel
shells are treated the same as live mussels,
and caddisfly cases are treated the same as
live caddisflies (Figure 3).
The assessment is based only on what is
observed, not on what would be predicted
to occur if the channel were wet, or in the
absence of disturbances or modifications.
Disturbances and modifications should be
described in the "Notes" section of the data
form and taken into account when drawing
conclusions.
1. Presence of Aquatic Macroinvertebrates
Are there aquatic macroinvertebrates
in the assessment reach? If at least one
macroinvertebrate (or macroinvertebrate
shell, casing, or exuviae) is present, the
answer is "yes." *
This indicator includes the range of
macroinvertebrates typically associated
with stream habitats including: Coleoptera
(aquatic beetles), Diptera (true flies),
Ephemeroptera (mayflies), Megaloptera
(dobsonflies and alderflies), Mollusca
(snails and clams), Odonata (dragonflies
and damselflies), Plecoptera (stoneflies),
Trichoptera (caddisflies), and Astacoidea
(crayfish).
*Exception: If the ONLY macroinvertebrate
present is Culicidae (mosquito) larvae/
pupae, which is an ephemeral indicator
taxon (Mazzacano and Black 2008), the
answer is "no."
2. Presence of 6 or More Ephemeroptera
Are 6 or more individuals of the Order
Ephemeroptera present in the assessment
reach? If at least six Ephemeroptera are
present, the answer is "yes."
Ephemeroptera (mayflies) are present in
many stream systems. Adults are short-lived
and are commonly observed in swarms over
streams. Immature mayflies are aquatic and
have the following characteristics:
p Short and bristle-like antenna;
• Four to nine pairs of leaf-like or fan-like gills
usually visible along the sides of the abdomen;
• Three (rarely two) long filaments
at rear of abdomen.
3. Presence of Perennial Indicator Taxa
Are there perennial indicator taxa in
the assessment reach? If at least one
individual (or macroinvertebrate shell,
casing, or exuviae) of such taxa is present,
the answer is "yes."
Certain macroinvertebrate taxa are
associated with the prolonged presence
of water. Based on a literature review and
synthesis completed by the Xerces Society
for Invertebrate Conservation (Mazzacano
and Black 2008; Blackburn and Mazzacano
14
Streamflow Duration Assessment Method for the Pacific Northwest
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2012)6, several taxa and lifestages of
macroinvertebrates occurring in Pacific
Northwest streams have been identified as
"Perennial Indicators" (Table 1).
Available at: http://www.xerces.org/macroinvertebrate-streamflow-indicators/
Table 1: Perennial Macroinvertebrate Indicator Taxa and Life
Stages
Any life stage of:
Pleuroceridae, Ancylidae,
Hydrobiidae (Juga spp., freshwater
limpets, pebble snails)
Margaritiferidae, Unionidae
(freshwater mussels)
Larvae/pupae of:
Rhyacophilidae (freeliving caddisfly)
Philopotamidae (finger-net caddisfly)
Hydropsychidae (net-spinning caddisfly)
Glossosomatidae (saddle
case-maker caddisfly)
Nymphs of:
Pteronarcyidae (giant stonefly)
Perlidae (golden stonefly)
Larvae of:
Elmidae (riffle beetle)
Psephenidae (water penny)
Corydalidae (dobsonflies, fishflies)
Larvae/nymphs of:
Gomphidae (clubtail dragonfly)
Cordulegastridae (biddies)
Calopterygidae (broad-
winged damselflies)
Additional Indicators (4 and 5)
4. Wetland Plants In or Near Streambed
Within the assessment channel, and
within one-half channel width of the
stream on either bank, are there plants
with a wetland indicator status of FACW
or OBL, or is there submerged aquatic
vegetation present? If so, the answer is
"yes."
The U.S. Army Corps of Engineers
(USAGE) wetland delineation procedure7
uses a plant species classification system
which identifies hydrophytic plants.
Likewise, the presence of hydrophytic plants
can be used as an indicator of the duration
of soil saturation in or near stream channels.
Intermittent and perennial streams will often
have obligate wetland (OBL) and facultative
wetland (FACW) plants or submerged
aquatic vegetation (SAV) growing in or
immediately adjacent to the Streambed. SAV
grows completely underwater.
To determine the wetland indicator status of
a plant, consult the National Wetland Plant
List (NWPL). The NWPL, formerly called
the National List of Plant Species that Occur
in Wetlands, was revised by the USAGE,
U.S. Fish and Wildlife Service, USEPA, and
the Natural Resource Conservation Service
in 2013, and is available at: http://rsgisias.
crrelusace.army.mil/NWPL/.
The wetland plant indicator is assessed
based on the single most hydrophytic
wetland plant found in or within one-half
channel width of the assessed reach, even if
that plant is not a dominant species.
http://el.erdc.usace.army.mil/elpubs/pdf/wlmanS7.pdf
November 2015
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Notes:
• Abundance and prevalence throughout the reach
is not a factor in determining this indicator.
p While it is sometimes most convenient to take
plant samples off-site for identification at a
later date, please note that several aquatic plant
species are protected by state and federal laws.
5. Slope
What is the 'straight line' slope, as
measured with a clinometer, from the
beginning of the reach to the end of the
reach? Is it greater than or equal to
10.5%? To 16%?
Channel slope is measured as percent slope
between the lower and upper extent of
the assessment reach. This is most easily
accomplished by a two-person team, with
one individual standing in the thalweg at the
downstream extent of the reach and, using a
clinometer, sighting a location at eye-level
at the upper extent of the reach, (e.g., if
team members are of the same height, one
individual standing in the thalweg at the
lower end of the reach would 'site' the eyes
of the crew member standing in the thalweg
at the upper end of the reach).
This measurement requires direct line-of-
site between the lower and upper ends of the
reach. If direct line-of-site from the bottom
to top of the reach is not possible, the slope
of the longest representative portion of the
reach should be 'line-of-site' evaluated.
Note: This measurement is not necessarily
the same as the 'average water-surf ace
slope' which is often evaluated as part of
stream ecological assessments including
U.S. EPA's Environmental Monitoring and
Assessment Program (EMAP) (Peck et al.
2006) and Oregon Department of Fish and
Wildlife's Aquatic Inventory (Moore et al.
2006).
Ancillary Information
The presence of these features should be
noted and briefly described, if applicable, as
indicated on the assessment form.
Riparian Corridor: Is there a distinct
change in vegetation between the
surrounding uplands and the riparian zone,
or corridor, along the stream channel?
Intermittent and perennial streams often
support riparian areas that contrast
markedly with adjacent upland plant
communities. A distinct change in
vegetation between the surrounding
lands and the riparian area (top of bank
and adjacent areas) may indicate the
presence of seasonal moisture.
Erosion and Deposition: Does the channel
show evidence of fluvial erosion in the form
of undercut banks, scour marks, channel
downcutting, or other features of channel
incision? Are there depositional features
such as bars or recent deposits of materials
in the stream channel?
Undercut banks and scour marks are
the most common signs of fluvial
erosion for streams in a floodplain
system. In steeper landscapes, channel
downcutting and incision may occur.
Alluvium may be deposited as sand,
silt, gravel and cobble. Sometimes there
may be depositional features along the
side of the channel or on the lee side of
obstructions in the channel (e.g., in the
hydraulic shadow of logs, boulders, etc.).
Erosion and deposition processes differ
between bedrock and alluvial channels;
note if the streambed consists primarily
of bedrock.
16
Streamflow Duration Assessment Method for the Pacific Northwest
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Floodplain connectivity: Is there an active
floodplain at the bankfull elevation?
A floodplain is a level area near a stream
channel, constructed by the stream
and overflowed during moderate flow
events if there is still connectivity. An
active floodplain (at current bankfull
elevation, such that it is inundated
on an approximate 2-year recurrence
interval) shows characteristics such as
drift lines, sediment and debris deposits
on the surface or surrounding plants, or
flattening of vegetation. The floodplain
of incised streams may be restricted to
within the channel itself and the previous
floodplain (now a terrace) may be
inundated rarely or infrequently, if at all.
November 2015 17
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Section 3: Drawing Conclusions
Results of the field evaluation, applied to
the assessment decision-tree (Figure 4; also
included on the field assessment form), are
used to determine whether the assessed
stream has perennial, intermittent, or
ephemeral streamflow.
Figure 4: Decision tree for drawing conclusions from
assessed indicators
Are aquatic macroinvertebrates present?
(Indicator 1)
If Yes: Are 6 or more
individuals of the Order
Ephemeroptera present?
(Indicator 2)
JL
If No: Are SAV, FACW, or OBL
plants present?
(Indicator 4)
In addition, the method indicates a stream is
at least intermittent when either of the two
following criteria, for the presence of fish or
for the presence of specific herpetological
species, is met:
1. One or more fish are found
in the assessment reach.*
Fish are an obvious indicator of flow
presence and duration. Fluctuating water
levels of intermittent and ephemeral streams
provide unstable and stressful habitat
conditions for some fish communities.
However, the strongly seasonal precipitation
pattern in the Pacific Northwest means
intermittent streams may flow continuously
for several months; thus, some native fish
species have evolved to use intermittent
streams for significant portions of their
lifespan (e.g., Wigington et al. 2006).
When looking for fish, all available habitats
should be searched, including pools, riffles,
root clumps, and other obstructions. In small
streams, the majority of fish species usually
inhabit pools and runs. Also, fish will
seek cover if disturbed, so we recommend
checking several areas along the sampling
reach, especially underneath undercut banks
and other places likely to provide cover.
^Exception: Non-native fish, with the
exception of mosquito fish (Gambusia spp.)
that has been placed as a vector control, are
also included in the assessment. If Gambusia
spp. is encountered as the only fish species
present, its placement as a vector control
at the site must be documented, along with
an explanation of why the single indicator
('presence of fish') conclusion does not
apply.
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Streamflow Duration Assessment Method for the Pacific Northwest
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2. One or more individuals of an
amphibian or snake life stage (adult,
juvenile, larva, or eggs) identified as
obligate or facultative wet (Table 2)
are present in the assessment reach.
Amphibians, by definition, are associated
with aquatic habitats, and some amphibians
require aquatic habitat for much or all of
their lives. In the Pacific Northwest, there
are likewise three snake species that require
aquatic habitat for significant portions
of their life cycle. This indicator focuses
on the life history stages of salamanders,
frogs, toads, and snake species that require
aquatic habitat by indicating life history
stages for these species as facultative (FAC),
facultative wet (FACW), or obligate (OBL).8
This indicator is assessed using a minimum
20 minute search time, within one channel
width from the top of both stream banks, to
sample the range of habitats present This
search can be conducted concurrently with
the macroinvertebrate search (Indicators 1 -
3) for greatest efficiency. Various life stages
of frogs and salamanders can be found under
rocks, on stream banks and on the bottom
of the stream channel. They may also
appear in benthic samples. Using kicknets
or smaller nets and light colored tubs for
The designations "FAC", "FACW", and "OBL" are based on a
review of the scientific literature and current understanding of
the life history stages of these herpetological species.
Table 2: Water-dependent life stages of amphibians and snakes of the Pacific Northwest. OBL - obligate, requires surface or
hyporheic water; FACW - facultative wet, strong preference for surface or hyporheic water; FAC - facultative, uses but does not
depend on surface or hyporheic water. These designations are based on a review of the scientific literature and current
understanding of the life history stages of these herpetological species.
Species
Common Name
Water-Dependent Life Stages
1-5&=
AH i lit
Aquatic Salamanders
Ambystoma gracile
Ambystoma macrodactylum
Ambystoma tigrinum
Taricha granulosa
Dicamptodon copei
Dicamptodon tenebrosus
Rhyacotriton spp.
Northwest Salamander
Long-toed Salamander
Tiger Salamander (rare)
Roughskin Newt
Cope's Giant Salamander
Pacific Giant Salamander
Torrent Salamanders (rare)
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
FACW
FACW
FACW
FAC
OBL
OBL
OBL
FACW
FACW
FACW
FAC
OBL
FACW
OBL
Frogs and Toads
Ascaphus truei
Spea intermontana
Bufo boreas
Bufo woodhousii
Pseudacris regilla
Rana aurora
Rana boylii
Rana cascadae
Rana catesbeiana
Rana pretiosa
Rana luteiventris
Tailed Frog
Great Basin Spadefoot
Western Toad
Woodhouse's Toad
Pacific Treefrog
Red-Legged Frog
Foothill Yellow-Legged Frog
Cascades Frog
Bullfrog
Oregon Spotted Frog
Columbia Spotted Frog
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
OBL
FAC
FAC
FAC
FACW
FACW
OBL
FACW
FACW
OBL
OBL
OBL
FAC
FAC
FAC
FAC
FACW
OBL
FACW
FACW
OBL
OBL
Snakes
Thamnophis atratus
Thamnophis elegans
Thamnophis sirtalis
Western Aquatic Garter Snake (SW Oregon)
Wandering Garter Snake
Common Garter Snake
OBL
FACW
FACW
OBL
FACW
FACW
November 2015
19
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specimen collection and identification is
recommended. Certain frogs and tadpoles,
as well as adult and larval salamanders,
typically inhabit the shallow, slower moving
waters of stream pools and near the sides of
banks.
Amphibians of Oregon, Washington, and
British Columbia (Corkran and Thorns
1996) and A Field Guide to Western Reptiles
and Amphibians (Stebbins 2003) are useful
field guides for identifying amphibians of
the Pacific Northwest.
Note: Vertebrates must be identified at the
assessment site, and left at the site following
identification. We recommend that a series
of photographs be taken of any species in
question to allow further identification to be
done off-site, if necessary. Please note that
several animal species, including fish and
amphibian species, are protected by state
and federal laws.
Additional considerations
If the stream does not have a bed and
banks, is covered with wetland plant
species, and/or indicators cannot be
assessed, it may be more appropriate to
consider the reach as a swale, wetland, or
upland.
As discussed in the introductory sections, if
the channel does not meet the decision-tree
or single indicator criteria and the evaluator
believes the channel to be perennial or
intermittent, the evidence supporting this
assertion should be clearly described on
the assessment form. This may occur in
highly polluted or recently manipulated
streams; in those cases, the indicators that
could potentially be there were it not for the
pollution/manipulation should be described
in the "Additional Notes" section of the field
form.
20
Streamflow Duration Assessment Method for the Pacific Northwest
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Appendix A: Relevant References
Adams, J. and M. Vaughan, 2003.
Macroinvertebrates of the Pacific Northwest:
a field guide. The Xerces Society for
Invertebrate Conservation, Portland, OR.
Adams, M.J. and R.B. Bury, 2002. The endemic
headwater stream amphibians of the American
Northwest: associations with environmental
gradients in a large forested preserve. Global
Ecology & Biogeography 11:169-178.
Anderson, R. J., B.P Bledsoe and W.C. Hession,
2004. Width of streams and rivers in response
to vegetation, bank material, and other
factors. Journal of the American Water
Resources Association 40:1159-1172.
Austin, B.J. and E.A. Strauss, 2011. Nitrification
and denitrification response to varying periods
of desiccation and inundation in a western
Kansas stream. Hydrobiologia 658 (1):183-195.
Barbour, M.T., J. Gerritsen, B.D. Snyder and
J.B. Stribling, 1999. Rapid bioassessment
protocols for use in streams and wadeable
rivers: periphyton, benthic macroinvertebrates
and fish, second edition. EPA 841-B-99-
002, U.S. Environmental Protection Agency,
Office of Water, Washington, D.C.
Bencala, K.E., 2005. Hyporheic exchange flows.
In: Encyclopedia of Hydrological Sciences,
Anderson, M. and J.J. McDonnell, (editors).
Volume 3, John Wiley and Sons, New York.
Benda, L., M.A. Hassan, M. Church, and C.L.
May, 2005. Geomorphology of steepland
headwaters: the transition from hillslopes
to channels. Journal of the American Water
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Streamflow Duration Assessment Method for the Pacific Northwest
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Appendix B: Streamflow Duration Field Assessment Form
Project #/ Name
Assessor
Address
Date
Waterway Name
Reach Boundaries
Coordinates at i_at.
downstream end
(ddd.mm.ss)
Lon
N
W
Precipitation w/in 48 hours (cm)
Channel Width (m)
n Disturbed Site/ Difficult
^J /
Situation (Describe in "Notes")
% of reach w/observed surface flow_
Observed
Hydrology
% of reach w/any flow (surface or hyporheic).
# of pools observed
Observations
Observed Wetland Plants
(and indicator status):
Observed Macroinvertebrates:
Taxon
Indicator Ephemer- # of
Status optera? Individuals
s
1. Are aquatic macroinvertebrates present?
Yes
No
2. Are 6 or more individuals of the Order Ephemeroptera present?
Yes
No
3. Are perennial indicator taxa present? (refer to Table i)
Yes
No
4. Are FACW, OBL, or SAV plants present? (Within V2 channel width)
Yes
No
5. What is the Slope? (In percent, measured for the valley, not the stream)
Conclusions
Are aquatic
macroinvertebrates
present?
(Indicator 1)
If Yes: Are 6 or more
individuals of the Order
Ephemeroptera
present?
(Indicator 2)
If No: Are SAV, FACW,
or OBL plants present?
(Indicator 4)
Single Indicators:
n Fish
Q Amphibians
Finding: | _ | Ephemeral
] Intermittent
Perennial
November 2015
27
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Notes: (explanation of any single indicator conclusions, description of disturbances or modifications that may
interfere with indicators, etc.)
Difficult Situation:
Q] Prolonged Abnormal Rainfall / Snowpack
Q Below Average
Q| Above Average
Q] Natural or Anthropogenic Disturbance
n Other:
Describe situation. For disturbed streams, note extent, type,
and history of disturbance.
Additional Notes: (sketch of site, description of photos, comments on hydrological observations, etc.) Attach
additional sheets as necessary.
Ancillary Information:
Q Riparian Corridor
Q| Erosion and Deposition
Q Floodplain Connectivity
Observed Amphibians, Snake, and Fish:
Life
History
Taxa
Stage
Location
Observed
Number of
Individuals
Observed
28 Streamflow Duration Assessment Method for the Pacific Northwest
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©EPA
United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue, Suite 900
Seattle, WA 98101-1128
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