National Rivers and Streams Assessment
United States 2008-2009
Environmental Protection
A Collaborative Survey
RAFT
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National Rivers and Streams
Assessment 2008-2009
A Collaborative Survey
DRAFT
U.S. Environmental Protection Agency
Office of Wetlands, Oceans and Watersheds
Office of Research and Development
Washington, DC 20460
EPA/841/D-13/001
February 28, 2013
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Table of Contents
Executive Summary xi
Key findings xi
Biological quality xi
Chemical stressors xii
Physical habitat stressors xiii
Human health indicators xiii
Change in stream condition xiii
Implications xiv
Chapter 1. Introduction 1
The nation's rivers and streams 1
Some facts about large rivers 2
Smaller streams and rivers 3
The Wadeable Streams Assessment 4
Chapter 2. Design of the National Rivers and Streams Assessment 6
What area does the NRSA cover? 6
What regions are used to report NRSA results? 7
How were sampling sites chosen? 10
How were waters assessed? 12
Setting expectations 14
Chapters. Condition of the Nation's Rivers and Streams 19
Background 19
Indicators of biological condition 19
Macroinvertebrate Multimetric Index 20
Findings for the Macroinvertebrate Multimetric Index 23
Macroinvertebrate Observed/Expected Ratio of Taxa Loss 23
Findings for 0/E Taxa Loss 24
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Table of Contents (Continued)
Fish Multimetric Index 25
Findings for the Fish Multimetric Index 25
Periphyton Multimetric Index 26
Findings for the Periphyton Multimetric Index 27
Aquatic indicators of stress 28
Chemical stressors 29
Physical habitat stressors 35
Ranking stressors: relative extent, relative risk, and attributable risk 40
Relative extent 41
Relative risk 42
Attributable risk 45
Chapter 4. Human Health Considerations in the Nation's Rivers and Streams...47
Background 47
Mercury in fish tissue 47
Findings for mercury in fish tissue 49
Pathogen indicators (enterococci) 50
Findings for enterococci 52
Chapter 5. Changes in Stream Condition 56
Findings for changes in stream condition 56
Chapters. Ecoregional Results 61
Introduction 61
Nationwide comparisons 63
Biological condition Macroinvertebrate Multimetric Index 63
Nutrients-total phosphorus and nitrogen 64
Riparian vegetative cover 65
Enterococci 67
Northern Appalachians 67
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Table of Contents (Continued)
Setting 68
Summary of NRSA find ings, Northern Appalachians 68
Southern Appalachians 70
Setting 70
Summary of NRSA find ings, Southern Appalachians 71
Coastal Plains 73
Setting 73
Summary of NRSA find ings, Coastal Plains 74
Upper Midwest 75
Setting 75
Summary of NRSA find ings, Upper Midwest 76
Temperate Plains 78
Setting 78
Summary of NRSA find ings, Temperate Plains 79
Southern Plains 80
Setting 80
Summary of NRSA find ings, Southern Plains 81
Northern Plains 83
Setting 83
Summary of NRSA find ings, Northern Plains 83
Western Mountains 85
Setting 85
Summary of NRSA find ings, Western Mountains 86
Xeric 88
Setting 88
Summary of NRSA find ings 89
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Table of Contents (Continued)
Chapter 7. Summary and Next Steps 91
Moving the science forward 93
Next steps 94
Glossary of Terms 100
Sources and References 102
General references 102
Stream and river sampling and laboratory methods 103
Probability designs 104
Ecological regions 104
Fish multimetric indices 105
Indices of biotic integrity 105
Observed/expected models 106
Periphyton 106
Physical habitat 107
Reference condition 108
Other EMAP assessments 108
Biological condition gradient/quality of reference sites 108
Relative risk 108
Nutrients 109
List of Abbreviations and Acronyms 110
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Tables and Figures
Tables
Table 1. Length of river and streams represented in the NRSA, by ecoregion 10
Table 2. Indicators evaluated for the NRSA 14
Figures
Figure 1. Biological condition of the nation's rivers and streams, based on the
Macroinvertebrate Multimetric Index xii
Figure 2. Average annual precipitation in the U.S 6
Figure 3. Major NRSA climatic regions 8
Figure 4. Nine ecoregions surveyed for the NRSA 8
Figure 5. NRSA sample sites 11
Figure 6. Reach layout used for sampling in the NRSA 12
Figure 7. Biological condition of the nation's rivers and streams based on the -
Macroinvertebrate Multimetric Index 23
Figure 8. Macroinvertebrate taxa loss in the nation's rivers and streams as measured -
by the Observed/Expected Ratio of Taxa Loss 24
Figure 9. Condition of the fish assemblage in the nation's rivers and streams as -
measured by the Fish Multimetric Index 26
Figure 10. Condition of periphyton assemblage in the nation's rivers and streams based -
on the Periphyton Multimetric Index 28
Figure 11. Total phosphorus concentrations in the nation's rivers and streams 30
Figure 12. Total nitrogen concentrations in the nation's rivers and streams 31
Figure 13. Salinity conditions in the nation's rivers and streams 33
Figure 14. Acidification in the nation's rivers and streams 35
Figure 15. Excess streambed sediment in the nation's rivers and streams 37
Figure 16. In-stream habitat in the nation's rivers and streams 38
Figure 17. Riparian vegetative cover in the nation's rivers and streams 39
Figure 18. Riparian disturbance in the nation's rivers and streams 40
Figure 19. Relative extent of stressors in the nation's rivers and streams 41
Figure 20. Relative extent, relative risk, and attributable risk to macroinvertebrates -
based on the Macroinvertebrate Multimetric Index 43
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Tables and Figures (Continued)
Figure 21. Relative extent, relative risk, and attributable risk to fish based on the Fish
Multimetric Index 44
Figure 22. Relative extent, relative risk, and attributable risk to periphyton based on -
the Periphyton Multimetric Index 45
Figure 23. Human health fish tissue assessment for target and sampled populations of -
the nation's rivers 50
Figure 24. Percent offish tissue target population sampled for mercury in fish tissue in -
the three major climatic regions of the U.S 50
Figure 25. Enterococci human health thresholds exceedance in the nation's rivers and -
streams 52
Figure 26. Mercury in fish tissue from urban sites 54
Figure 27. PFOS in fish tissue from urban sites 55
Figure 28. Change in macroinvertebrate condition and nutrients between 2004 and -
2008-2009, based on percent of length in good condition 58
Figure 29. Change in stream fish habitat, riparian vegetation cover, and riparian -
disturbance between 2004 and 2008-2009 60
Figure 30. Ecoregional surveys for the NRSA 62
Figure 31. Biological condition in rivers and streams based on the Macroinvertebrate -
Multimetric Index across the nine ecoregions 63
Figure 32. Total phosphorus levels in rivers and streams across the nine ecoregions 64
Figure 33. Total nitrogen levels in rivers and streams across the nine ecoregions 65
Figure 34. Riparian vegetative cover in rivers and streams across the nine ecoregions 66
Figure 35. Enterococci human health threshold exceedance in rivers and streams -
across the nine ecoregions 67
Figure 36. NRSA survey results forthe Northern Appalachians ecoregion 69
Figure 37. NRSA survey results forthe Southern Appalachian ecoregion 72
Figure 38. NRSA survey results forthe Coastal Plains ecoregion 74
Figure 39. NRSA survey results forthe Upper Midwest ecoregion 77
Figure 40. NRSA survey results forthe Temperate Plains ecoregion 79
Figure 41. NRSA survey results forthe Southern Plains ecoregion 82
Figure 42. NRSA survey results forthe Northern Plains ecoregion 84
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Tables and Figures (Continued)
Figure 43. NRSA survey results forthe Western Mountains ecoregion 87
Figure 44. NRSA survey results forthe Xeric ecoregions 89
Figure 45. Map of about 1,200 probability sites in California sampled since 2000 using -
compatible EMAP-style survey designs 96
Figure 46. Biological condition of perennial streams in the six major ecological regions -
of California 97
Figure 47. Percentage of California stream length that exceeds severe and moderate -
threshold values for various chemical and physical habitat stressor variables -
in streams associated with each of three major land cover types 97
Figure 48. Relative risk of biological impairment associated with a series of habitat and -
chemistry variables in southern California streams 98
Figure 49. The combination of probability and reference distributions provides -
objective context for interpreting targeted monitoring data 98
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Executive Summary
This National Rivers and Streams Assessment 2008-2009: A Collaborative Survey (NRSA)
presents the results of an unprecedented sampling effort undertaken by the U.S. Environmental
Protection Agency and its state and tribal partners. It provides information on the ecological
condition of the nation's rivers and streams and the key stressors that affect them, both on a
national and an ecoregional scale. It also discusses change in water quality conditions in
streams sampled for an earlier study, the Wadeable Streams Assessment of 2004.
During the summers of 2008 and 2009, more than 85 field crews sampled 1,924 river and
stream sites across the country. Using standardized field methods, they sampled waters as
large as the Mississippi River and as small as mountain headwater streams. Sites were selected
using a random sampling technique that uses a probability-based design. This design ensures
that the results of the survey reflect the full variety of river and stream types and sizes across
the U.S. To determine water quality conditions, sampling results were compared to conditions
at least-disturbed (or reference) sites in different ecological regions.
The goals of the NRSA are to determine the extent to which rivers and streams support a
healthy biological condition and the extent of major stressors that affect them. In addition, the
survey supports a longer-term goal: to determine whether our rivers and streams are getting
cleaner and how we might best invest in protecting and restoring them.
Key findings
Biological quality
Biological condition is the most comprehensive indicator of water body health: when the
biology of a stream is healthy, the chemical and physical components of the stream are also
typically in good condition. Twenty-one percent of the nation's river and stream length is in
good biological condition, 23% is in fair condition, and 55% is in poor condition, based on a
robust, commonly used index that combines different measures of the condition of aquatic
benthic macroinvertebrates (aquatic insects and other creatures such as crayfish). Of the three
major climatic regions (Eastern Highlands, Plains and Lowlands, and West) discussed in this
report, the West is in the best biological condition, with 42% of river and stream length in good
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Executive Summary
condition. In the Eastern Highlands, 17% of river and stream length is in good condition; in the
Plains and Lowlands, 16% is rated in good condition (Figure 1).
National Biological Condition
0.9%
Figure 1. Biological condition of the nation's rivers and streams, based on the Macroinvertebrate Multimetric
Index (EPA/NRSA).
Chemical stressors
Four chemical stressors were assessed: total phosphorus, total nitrogen, salinity, and
acidification. Of these, phosphorus and nitrogen are by far the most widespread. Forty percent
of the nation's river and stream length has high levels of phosphorus and 28% has high levels of
nitrogen. Poor biological condition (for macroinvertebrates) is 50% more likely in rivers and
streams with high levels of phosphorus and 40% more likely in rivers and streams with high
levels of nitrogen. Acidification, although a problem in less than 1% of U.S. river and stream
length, has a significant impact on biological condition where it is found: poor biological
condition is 50% more likely in waters affected by acidification.
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Executive Summary
Physical habitat stressors
Four indicators of physical habitat condition were assessed for the NRSA: excess streambed
sediments, riparian vegetative cover (vegetation in the land corridor surrounding the river or
stream), riparian disturbance (human activities near the river or stream), and in-stream fish
habitat. Of these, poor riparian vegetative cover and high levels of riparian disturbance are the
most widespread stressors, reported in 24% and 20% of the nation's river and stream length,
respectively. However, excess levels of streambed sediments, reported in 15% of river and
stream length, were found to have a somewhat greater impact on biological condition. Poor
biological condition is 60% more likely in rivers and streams with excessive levels of streambed
sediments.
Human health indicators
Two indicators that provide insight into potential risks to human health were assessed:
mercury in fish tissue and enterococci (bacteria). Human health screening values for mercury in
fish tissue are exceeded in 13,144 miles of U.S. river length (streams were not evaluated). In 9%
of river and stream length, samples exceed an enterococci threshold level for protecting human
health.
Change in stream condition
Compared to the findings of the 2004 WSA, some statistically significant changes are found
in stream condition. Nationally, the amount of stream length in good quality for
macroinvertebrate condition dropped from 27.4% in 2004 to 20.5%; this change appears driven
in large part by a 13.3% decline in streams in good condition in the Plains and Lowlands climatic
region. In addition, the percent of stream length in good condition for phosphorus dropped
nationally from 52.8% to 34.2% and declined in all three major climatic regions. However, other
indicators showed an increase in stream length in good condition: the percent of stream length
in good condition for nitrogen rose from 46.6% in 2004 to 55.4%; percent of stream length with
good in-stream fish habitat rose from 51.7% to 68.9%; and percent of stream length in good
condition for riparian disturbance (i.e., with low levels of disturbance) rose from 22.7% to
34.8%. It is important to note that these are differences/or streams only, between two points
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Executive Summary
in time. Future surveys and more data are needed to discern trends and the reasons for those
trends.
Implications
A picture of the condition of the nation's rivers and streams is emerging from this survey
and its predecessor streams assessment. Our rivers and streams are under significant stress and
more than half exhibit poor biological condition. Phosphorus, nitrogen, and streambed
sediments in particular have widespread and severe impacts; reducing levels of these
constituents will significantly improve the biological health of rivers and streams. This survey
suggests the need to address the many sources of these stressors including runoff from
urban areas, agricultural practices, and wastewater in order to ensure healthier waters for
future generations.
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Chapter 1. Introduction
The nation's rivers and streams
This report presents the findings of the National Rivers and Streams Assessment 2008-
2009: A Collaborative Survey, the first statistically based survey of the condition of the nation's
rivers and streams. The survey sampled a stunning range of waters: huge workhorse rivers that
roll past our largest urban areas, tiny undisturbed creeks tucked away in national parks, and
everything in between. This report also compares the condition of streams to those of an
earlier study that focused on small streams (the Wadeable Streams Assessment or WSA)
conducted by the U.S. Environmental Protection Agency and its partners in 2004.
Rivers and streams shape our landscape. They supply humans with drinking water, carry
away our wastes and used water, irrigate our crops, power our cities with hydroelectricity, and
offer us myriad recreational and commercial opportunities. They support fish and other aquatic
life and provide shelter, food, and habitat for birds and wildlife of all types. They are the land's
vast and interconnected circulatory system, carrying water, sediment, and organic material
from the mountains to the sea. Clean and healthy rivers and streams greatly enhance the
quality of our lives.
Over the centuries, we have radically changed most U.S. rivers and streams by interrupting
their flows with dams and levees; straightening and modifying their channels for irrigation,
navigation, or flood control; building our cities and developing our farmland in their watersheds
and floodplains; withdrawing their water for our use; and discharging our waste materials into
their flow. Our rivers and streams are also subject to other influences such as seasonal, annual,
and climate-change-induced variations in precipitation and temperature, as well as changing
cycles of erosion and deposition (e.g., during flooding or dam releases). To effectively manage,
restore, and protect these rivers and streams, we must improve the information we need to
make wise water quality decisions.
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Chapter 1. Introduction
Some facts about large rivers
The nation's large rivers the biggest of which are often referred to as the Great Rivers
are familiar to all of us, part of our American history and lore. Their contribution to our nation
cannot be overestimated. Some examples of their power, breadth, and value:
> The Mississippi River is the largest in the U.S. by drainage area and discharge; its
watershed (that is, the area it drains) is one of the largest in the world and covers 1.2
million square miles. At Lake Itasca, where the Mississippi begins, its average flow rate is
6 cubic feet per second. At New Orleans the average flow rate is 600,000 cubic feet per
second. Agriculture is the dominant land use in the Mississippi River basin; 60% of all
grain exported from the U.S. is shipped on the Mississippi River through the ports at its
mouth.
> The Missouri River, known as the "Big Muddy," is the longest in the U.S., at about 2,540
miles, and drains one sixth of the country. It begins in the Rocky Mountains in Montana,
flows east and south, and joins the Mississippi River north of St. Louis, Missouri. It was
the "highway" used by Lewis and Clark and became an important route for trade and
westward expansion in the 1800s. The Missouri has been extensively dammed for
irrigation, hydroelectricity, and flood control, and its river basin is home to ten million
people from 28 tribes, ten states, and a small part of Canada.
> The Delaware River is the longest undammed river east of the Mississippi, flowing for
330 miles from the confluence of the east and west branches in Hancock, New York,
through Pennsylvania, New Jersey, and Delaware to the Atlantic Ocean. Its 13,539-
square-mile watershed is only about 0.4% of the land area of the continental U.S., but it
supplies water to 5% of the nation's population over 15 million people including
residents of New York City and Philadelphia.
> The Columbia River Basin is the most hydroelectrically developed river system in the
world. By volume, the Columbia is the fourth-largest river in the U.S., and it has the
greatest flow of any North American river draining into the Pacific. More than 400 dams,
including 11 on the Columbia mainstem and hundreds of others on tributaries in the
watershed, generate more than 21 million kilowatts.
> The Colorado River flows across 1,450 miles of mountainous and desert terrain from the
Rocky Mountains to the Gulf of California. It supplies water to over 25 million people in
seven western states, two Mexican states, and 32 tribal communities; helps irrigate 3.5
million acres of farmland; and provides electricity for 30 million people. There are ten
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Chapter 1. Introduction
major dams on the Colorado River among them Hoover Dam and 80 smaller
diversions, making it one of the most controlled rivers in the world.
Smaller streams and rivers
At the other end of the spectrum from the nation's large rivers are the small stream and
river systems often referred to as "wadeable" because they are shallow enough to sample
without a boat. About 90% of perennial (i.e., continuously flowing) stream and river miles in the
U.S. are considered wadeable. These smaller streams are the ones we know best: they drain
our neighborhoods and fields and flow past our campgrounds. They are also a critical part of
the ecosystem, providing food and shelter to a broad array of aquatic organisms, birds, and
wildlife.
Ecologists commonly define stream size according to the "Strahler stream order"; wadeable
streams usually fall into the first - through fifth-order range. The life of a river begins in its
headwaters, or first-order streams; as streams of a certain order join one another, their stream
order increases.
Stream order affects a stream's natural characteristics, including the biological communities
the plants and animals that live in it. For example, first- and second-order streams are
often quite clear and narrow and shaded by grasses, shrubs, and trees growing along their
banks. The food base of these streams consists of terrestrial insects and leaves from stream
bank plants, algae that attach to rocks and wood, aquatic insects adapted to shredding leaves
and scraping algae, and small fish that feed on these organisms.
In contrast, rivers that are sixth-order and higher typically appear muddy because their
large flow carries accumulated sediments downstream. They are wide, so the canopy cover
along their banks shades only the river's edge. The food base of wide rivers shifts away from
the stream bank toward in-stream sources such as algae, small organisms that are drifting down
stream, and eroded matter. The biological communities of mid-sized and large rivers are
dominated by aquatic insects adapted to filtering and gathering fine organic particles and by
larger fish that feed on plants, animals, and smaller fish.
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Chapter 1. Introduction
Many streams, especially those in the arid West, do not flow year-round. These were not
included in this survey because well-developed indicators to assess them are not yet available.
The Wadeable Streams Assessment
In 2004, EPA and its partners completed sampling for the first statistical survey of the
condition of the nation's small, perennial streams. The survey's purpose was to establish a
baseline of information on the condition of small streams and the extent of major
environmental stressors that affect them. Through the efforts of state environmental and
natural resource agencies, federal agencies, universities, and other organizations, more than
150 field biologists used standardized methods to collect environmental samples at 1,392
perennial stream locations. These sites were chosen using a statistical design to ensure that
results represented the condition of all U.S. streams. The WSA resulted from this ground-
breaking collaboration.
The WSA was implemented to help fill an information need identified over the years by a
number of independent organizations, including the Government Accountability Office, the
National Research Council, and the National Academy of Public Administration. In the early
2000s, these organizations noted that EPA and the states did not have a uniform, consistent
approach to monitoring that supported water quality decision-making. They called for more
efficient and cost-effective ways to understand the magnitude and extent of water quality
problems, the causes of these problems, and practical ways to address them.
In response, EPA, states, tribes, academics, and other federal agencies began collaborating
on a series of statistically based surveys called the National Aquatic Resource Surveys (NARS) to
provide the public and decision-makers with improved, statistically valid environmental
information. These surveys are nationally consistent and representative, use standardized field
and laboratory protocols, and follow rigorous quality assurance protocols. The WSA was based
on 15 years of EPA research and, like other surveys that followed, was designed to begin
answering such short- and long-term questions as:
> What is the extent of waters that support a healthy biological condition, recreation, and
fish consumption?
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Chapter 1. Introduction
I How widespread are major stressors that affect water quality?
> Are we investing wisely in water resource restoration and protection?
> Are our waters getting cleaner?
Under the NARS program and since the publication of the WSA in 2006, EPA and its many
partners have:
> Completed a survey of the nation's lakes, ponds, and reservoirs in 2007 (the National
Lakes Assessment, EPA 841-R-09-001) and conducted field work in the 2012 summer
sampling season for the next lakes assessment.
> Completed field work and lab analyses for the next National Coastal Condition Report,
currently under development.
> Finished field sampling and embarked on the analysis and reporting stage of the first-
ever National Wetland Condition Assessment.
I Developed this National Rivers and Streams Assessment and begun planning for the next
rivers and streams field season in 2013-2014.
These accomplishments would not have been possible without collaboration and
partnership among field biologists, taxonomists, statisticians, data analysts, project managers,
quality control officers, and reviewers in state, tribal, and federal offices and universities across
the country.
Why do we need consistent and statistically valid survey data on rivers and
streams?
Under the Clean Water Act, states are expected to monitor and required to assess and report
on the condition of the nation's waters, including the extent of waters that support the goals
of the Act However, methods of collecting and assessing data vary widely between states
and change over time, making it difficult to compare this information from state to state, for
the nation as a whole, or over time. State monitoring programs are generally designed to
meet state-specific information needs, such as locating impaired waters that require
additional pollution controls. They are not designed to answer national-level questions such
as whether or not U.S. water quality is improving one of the long-term goals of the
National Aquatic Resource Surveys. These surveys are meant to complement the state-
specific information and provide national and regional context to decision-makers.
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Chapter 2. Design of the National Rivers and Streams
Assessment
The NRSA is the first nationally consistent survey assessing the ecological condition of the
full range of flowing waters in the conterminous U.S. (lower 48 states). The target population
includes the Great Rivers (such as the Mississippi and the Missouri), small perennial streams,
and urban and non-urban rivers. Run-of-the-river ponds and pools are included, along with
tidally influenced streams and rivers up to the leading edge of dilute sea water.
The NRSA was designed to answer basic questions about the extent to which our rivers and
streams support healthy biological conditions and how widespread their key stressors are. Over
the longer term, as additional surveys in this series are completed, we will also learn whether
our waters are getting cleaner over time, and whether our policy decisions to protect and
restore them are effective or should be changed.
What area does the NRSA cover?
This report covers the conterminous U.S. 3,007,436 square miles. Of this area, 73% is
state or private land and the rest is federal or tribal land. Initial NRSA projects in Hawaii and
Alaska are also underway.
State political boundaries offer few insights into the true nature of the features that affect
our streams and rivers. The
most fundamental trait that
defines our waters is annual
precipitation (see Figure 2).
On either side of the 100th
meridian that runs from west
Texas through North Dakota,
a sharp change occurs where
precipitation falls plentifully
to the east but sparsely to
the west. (The high Figure 2. Average annual precipitation in the U.S. (NOAA).
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Chapter 2. Design of the National Rivers and Streams Assessment
mountains of the West and the Pacific coast are exceptions to the general scarcity of water in
the West.) The east-west divide in moisture has shaped not only the character of these waters
but also how we use them, how we value them, and even the legal system with which we
manage their allocation. A second divide that defines the nature of our rivers and streams is the
north-south gradient in temperature.
This huge area includes a wide diversity of landscapes, from the maple-beech-birch forests
and coastal plains of the East, to the enormous agricultural plains and grasslands of the mid-
continent, to the deserts and shrub lands of the Southwest, and to the giant mountain ranges
of the Rocky Mountains, Sierra Nevadas, and Cascades in the west. The Appalachian Mountains,
running from Maine to Alabama, cross state and climatic boundaries and separate the waters
flowing to the Atlantic from those flowing to the Gulf of Mexico.
The establishment and spread of European colonies and the industrial revolution of the 18th
century transformed our natural landscape as more people arrived and modified many of the
features of our land and waters. Tens of thousands of dams, large and small, have altered the
flow of virtually every major river and many smaller ones. The current and future condition of
our waters will continue to be influenced by our population patterns and how we use all
components of a watershed, including surface water, ground water, and the land itself.
What regions are used to report NRSA results?
The broadest scale unit for which results are reported in the NRSA is the continental U.S.
itself. Next are three climatic regions corresponding to major climate and landform patterns:
the West, Plains and Lowlands, and Eastern Highlands. The body of this report describes the
results for these broader-scale reporting units.
The finest-scale reporting unit included in this report consists of nine ecological regions that
further divide the climatic regions (Figure 4). The NRSA uses ecoregions to report results
because the patterns of response to stress, and the stressors themselves, are often best
understood in the context of these ecological regions.
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Chapter 2. Design of the National Rivers and Streams Assessment
500 750 JLOOO
Figure 3. Major NRSA climatic regions (EPA/NRSA).
NARSEcoreglons
Coartal Ptaln {CPL)
Northern Appalachians (NAPJ
Northern Plains (NPL)
Southern Appalachian5 (SAP)
Southern Plains (SPL)
Temperate Plains (TPL)
Upper Midwest (UMW)
^Western Mountains [WMTJ
Xerk(XER)
^
Figure 4. Nine ecoregions surveyed for the NRSA.
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Typically, management practices aimed at preventing degradation or restoring water quality
may apply to many flowing waters with similar problems throughout an ecoregion. Both the
climatic regions and ecoregions used in this report are aggregations of ecoregions as described
by Omernik in 1987. Ecoregion-specific results are included in Chapter 6 of this report.
> The Eastern Highlands climatic region is composed of the mountainous areas east of the
Mississippi River. It is further divided into the Northern Appalachians ecoregion
encompassing New England, New York, and northern Pennsylvania, and the Southern
Appalachians ecoregion extending from Pennsylvania into Alabama, through the eastern
portion of the Ohio Valley and including the Ozark Mountains.
> The Plains and Lowlands climatic region includes five of the NRSA ecoregions. The
Coastal Plain includes the low gradient areas of the east and southeast. It contains the
Atlantic and Gulf of Mexico coastal plains and the lowlands of the Mississippi delta,
which extend from the Gulf northward through Memphis, Tennessee. The Upper
Midwest is dominated by lakes and has little elevation gradient. The Temperate Plains is
also known as the Corn Belt. The Northern and Southern Plains are better known as the
Great Prairies. The Northern Plains includes the Dakotas, Montana, and northeast
Wyoming. The Southern Plains encompasses Nebraska, Kansas, Colorado, Oklahoma,
and Texas.
> The Western climatic region is defined by its Mountainous regions and the arid or Xeric
region that includes both the true deserts and the arid lands of the Great Basin.
To get a statistically valid state picture of water quality conditions, some of the states
participating in the NRSA opted for a finer state-scale resolution than the ecoregion scale by
increasing the number of sites they sampled within their borders. While their data are included
in the analyses described in this report, state-scale results are not presented. The states are
preparing similar analyses that reflect their own water quality standards and regulations.
It should be noted that NRSA assessments and findings regarding the condition of waters
nationally and in each ecoregion are not Clean Water Act section 303(d) impaired waters
determinations. Such determinations are made by states on specific water body segments using
applicable state water quality standards.
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How were sampling sites chosen?
NRSA sampling locations were selected using a modern survey design approach. This
approach, which is based on random selection, has been used in a variety of fields (e.g., health
surveys, election polls, monthly labor estimates) to determine the status of populations or
resources of interest using a representative sample of relatively few members or sites. This
approach is especially cost-effective if the population is so numerous that all components
cannot be sampled, or if it is not necessary to sample the entire resource in order to reach the
desired level of precision.
As consumers of information, we have all become accustomed to seeing survey data
reported in the news. Results in the NRSA have similar rigor in their ability to estimate the
percent of stream miles, within a range of certainty, that are in good, fair, and poor condition.
In order to pick a random sample, one must first know the location of members of the
population of interest. The NRSA design team used the EPA-USGS National Hydrography
Dataset Plus (NHD-Plus), a comprehensive set of digital spatial data on surface waters at the
1:100,000 scale, to identify the locations of perennial streams. They also obtained information
about stream order from the NHD-Plus. Table 1 shows the length of flowing waters in each of
the nine ecological regions used for the NRSA.
Table 1. Length of river and streams represented in the NRSA, by ecoregion
Ecoregion
Northern Appalachians
Southern Appalachians
Coastal Plains
Upper Midwest
Temperate Plains
Southern Plains
Northern Plains
Western Mountains
Xeric
Miles of Rivers and Streams in NRSA
119,094
315,242
176,510
96,142
227,017
36,594
27,227
150,975
44,974
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in
The 1,924 sites sampled for the NRSA were identified using a particular type of random
sampling technique called a probability-based sample design. In such a design, every element i
the population has a known probability of being selected for sampling. This important feature
ensures that the results of the survey reflect the full range in character and variation among
flowing waters across the U.S. Site selection rules included weighting to provide balance in the
number of river and stream sites from each of the size classes. Site selection was also controlled
for spatial distribution to make sure sample sites were distributed across the U.S. (see Figure 5).
Among these randomly selected sample sites were 359 of the original 2004 WSA sites. These
were revisited as part of the NRSA to examine whether conditions have changed.
When sites were selected for sampling, research teams conducted office evaluations and
field reconnaissance to determine if the sites were accessible or if a river or stream labeled as
perennial in NHD-Plus was, in fact, flowing during the sampling season. If a river or stream was
not flowing or was determined to be inaccessible, it was dropped from the sampling effort and
replaced with a perennial river or stream from a list of replacement sites within the random
design.
Figure 5. NRSA sample sites.
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How were waters assessed?
During the summers of 2008 and
2009, more than 85 trained crews,
composed primarily of state/tribal
environmental agency, EPA, and
contract staff, sampled river and
stream sites across the U.S. using
standardized field protocols. The field
protocols were designed to collect data
relevant to the ecological condition of
stream resources and the key stressors
affecting them. Each site was sampled
by a three- or four-person field crew.
Figure 6. Reach layout used for sampling in the NRSA.
During each site visit, crews laid out
the sample reach (i.e., stretch of river or stream) and the numerous transects to guide data
collection (see Figure 6). Field crews collected water samples which were sent to a lab for basic
chemical analysis, and collected biological samples from 11 transects or fixed paths along each
stream reach which were sent to taxonomists for identification. Crews recorded extensive data
on field forms and documented information about the physical characteristics of each stream
and the riparian area adjacent to its banks. Each crew was audited and 10% of the sites were
revisited as part of the quality assurance plan for the survey.
The use of standardized field and laboratory protocols for sampling across all 48 states
included in the NRSA (including the pilots in Alaska and Hawaii) is a key feature of the survey. It
allows the data to be combined to produce a nationally consistent assessment. This
standardization is necessary: states, tribes, academics, and federal agencies use a wide range of
methods to sample streams and rivers, and inconsistent results might have arisen if different
methods were used in this survey. In fact, this nationwide sampling effort provided an
opportunity to examine the comparability of different sample protocols by applying both the
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NRSA method and various state or USGS methods to a subset of the sites. Crews collected
physical, chemical, and biological data at all NRSA sites.
The NRSA uses fish, benthic macroinvertebrates (insects and other small animals such as
snails and crayfish) and algae as biological indicators of ecological condition. It focuses on these
three groups of organisms because they are each sensitive to different disturbances that result
from human activities and therefore give us a measurement of the biological integrity of rivers
and streams. Biological integrity has been 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). Macroinvertebrates are included in almost every state and
federal program monitoring rivers and streams, and are increasingly evaluated by volunteer
water quality monitoring organizations. Water quality monitoring and management programs
are also enhancing their understanding of biological integrity by adding other biological
assemblages, including fish and algae.
The NRSA supplements information on the ecological condition of streams with
measurements of key stressors that might negatively influence or affect stream condition.
Stressors are the chemical, physical, and biological components of the ecosystem that have the
potential to degrade biological integrity. Some of these are naturally occurring, some result
only from human activities, but most come from both sources. The challenge is in
understanding and effectively minimizing the pressures humans exert on aquatic systems
through their use of the surrounding environment.
Examples of chemical stressors are excess nutrients (nitrogen and phosphorus), salinity, and
acidification from acid deposition or mining. Most physical stressors such as excess
sedimentation, bank erosion, and loss of streamside trees and vegetation are created when
the physical habitat within the watershed of a stream network is altered. One of the key
components of an ecological assessment is a measure of how common each stressor is in a
region, and how severely it affects biotic integrity.
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In addition to these stressors, the NRSA investigated human health indicators, specifically
mercury levels in fish tissue and the fecal indicator enterococci.
Table 2 shows the key indicators evaluated for this report. NRSA scientists sampled for a
number of other indicators as well; future reports will discuss these, but they are not included
here due to technical and time considerations.
Table 2. Indicators evaluated for the NRSA
Biological Indicators Chemical Indicators Physical Indicators Human Health Indicators
Benthic
macroinvertebrates
Periphyton (algae)
Fish community
Phosphorus
Nitrogen
Salinity
Acidity
Streambed sediments
In-stream fish habitat
Riparian vegetative cover
Riparian disturbance
Enterococci (fecal
indicator)
Mercury in fish tissue
Setting expectations
In order to interpret the data collected by the NRSA field crews and to assess current
ecological condition, scientists need to compare the collected data to a benchmark an
estimate of what we would expect to find in a natural condition. Setting reasonable
expectations for each of the indicators is one of the greatest challenges to an assessment of
ecological condition. Should we take a historical perspective and try to compare current
conditions to an estimate of pre-Columbian conditions, or to pre-industrial conditions, or to
conditions at some other point in history? Or should we accept that some level of
anthropogenic disturbance is a given, and simply use the best of today's conditions as the
yardstick against which we compare everything else? These questions, and their answers, all
relate to the concept of reference condition: what do we use as a reference, or yardstick, to
assess today's condition?
Because it is difficult to estimate historical conditions for many indicators, the NRSA's
benchmark is "least-disturbed condition": the best available physical, chemical, and biological
habitat conditions given today's state of the landscape. Least-disturbed condition is defined
based on data from sites selected according to a set of explicit screening criteria, used to define
what is least-disturbed by human activities. These criteria vary from region to region to reflect
the natural variability across the American landscape; for the NRSA, separate criteria were
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defined for each of the nine ecoregions. The screening criteria were developed with the goal of
identifying the least amount of ambient human disturbance in each ecoregion. Reference
criteria, in essence, describe the sites whose condition is "the best of what's left" in the U.S.
The NRSA compares a subset of the chemical and physical data collected at each site to the
screening criteria to determine whether any given site is in least-disturbed condition for its
ecoregion. The NRSA does not use data on the biological assemblages as a screening factor to
select reference sites because that would have pre-judged expectations for biological condition.
For each of the stressor indicators, the NRSA used a similar process (i.e., identifying least-
disturbed sites according to specific criteria, but excluding the specific stressors themselves
from the criteria identifying the sites).
The reference site approach is then used to set expectations. The range of conditions found
in the reference sites for an ecoregion describes a distribution of values expected for least-
disturbed condition. The benchmarks used to define distinct condition classes (e.g., good, fair,
poor) based on the degree of disturbance are drawn from this reference condition.
The NRSA approach was to examine the range of values for an indicator in all of the
reference sites in a region, and to use the fifth percentile of the reference distribution to
separate the most disturbed sites from moderately disturbed sites. This means that stream
miles in the most disturbed category are worse than 95% of the best sites used to define
reference condition. Similarly, the 25th percentile was used to distinguish between moderately
disturbed sites and least-disturbed sites: stream miles reported as least-disturbed are as good
as 75% of the sites used to define reference condition.
Within the reference site population, there are two sources of variability:
> Natural variability the wide range of habitat types naturally found within each
ecoregion creates a spread of reference sites representing those different habitats.
Capturing natural variability in reference sites helps establish reference conditions that
represent the range of natural environments in the ecoregions.
> Human activities have changed many areas in the U.S., with natural landscapes
transformed by cities, suburban sprawl, agricultural development, and resource
extraction. The extent of those disturbances varies across regions. Some regions have
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reference sites in watersheds with little to no evidence of human impact, such as
mountain streams or rivers in areas with very low population densities. Other regions
have few sites that have not been influenced by human activities. The least-disturbed
reference sites in these widely influenced regions display more variability in quality than
those in areas with little human disturbance.
Variation within the reference distribution due to disturbance was addressed before
benchmarks were set for the condition classes of good, fair, and poor. For regions where the
reference sites exhibited a disturbance signal, the data analysis team accounted for this
disturbance by shifting the mean of the distribution toward the less-disturbed reference sites.
NRSA partners supported this reference-condition-based approach, which is consistent with
EPA guidance and state practice. Interested readers can find more detailed information about
determining reference condition in the NRSA technical report, published online at
www.epa.gov/aquaticsurveys.
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Understanding biological condition
The objective of the Clean Water Act is to restore and maintain the chemical, physical, and
biological integrity of the nation's waters. It establishes many national goals to control
pollution, including that water quality support healthy aquatic communities and provide for
recreational uses like swimming and fishing wherever attainable. A primary goal of the NRSA is
to develop a baseline understanding of the biological condition of our nation's streams.
One of the most meaningful ways to answer basic questions about water quality is to directly
observe the communities of plants and animals that live in water bodies. Aquatic plants and
animals are constantly exposed to various stressors. Therefore, they reflect not only current
conditions, but also the cumulative impacts of stressors and changes in conditions over time.
Benthic macroinvertebrates (aquatic insects, crustaceans, worms, and mollusks that live in river
and stream beds and in vegetation) are widely used to determine biological condition. These
organisms can be found in all rivers and streams, even in the smallest streams that cannot
support fish. Because they are relatively stationary and cannot escape pollution,
macroinvertebrate communities integrate the effects of stressors over time (i.e., pollution-
tolerant species will survive in degraded conditions, and pollution-intolerant species will die).
These communities are also critically important to fish because most game and non-game
species require a good supply of benthic macroinvertebrates as food. Biologists have been
studying the health and composition of benthic macroinvertebrate communities in streams for
decades. Biological condition is the most comprehensive indicator of water body health; when
the biology of a stream is healthy, the chemical and physical components of the stream are
also typically in good condition. In fact, several states have found that biological data
frequently detect stream impairment where chemistry data do not.
Data on biological condition are invaluable for managing the nation's aquatic resources and
ecosystems. Water quality managers can use these data to set protection and restoration goals,
decide which indicators to monitor and how to interpret monitoring results, identify stresses to
the water body and decide how they should be controlled, and assess and report on the
effectiveness of management actions. Many specific state responsibilities under the Clean
Water Actsuch as determining the extent to which waters support aquatic life uses,
evaluating cumulative impacts from polluted runoff, and determining the effectiveness of
discharger permit controlsare tied directly to an understanding of biological condition.
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Using multiple biological assemblages to determine biological condition
EPA's guidance on developing biological assessment and criteria programs recommends the
use of multiple biological assemblages to determine biological condition. The term "multiple
biological assemblages" simply refers to the three main categories of life found in a water
body: plants (e.g., algae), macroinvertebrates, and vertebrates (e.g., fish). The purpose of
examining multiple biological assemblages is to generate a broader perspective of the
condition of the aquatic resource of interest.
Each assemblage plays a different role in the way that rivers and streams function. Algae and
macroinvertebrates occur throughout all types and sizes of rivers and streams, whereas very
small streams may be naturally devoid of fish. Algae are the base of the food chain and capture
light and nutrients to generate energy. They are sensitive to changes in shading, turbidity, and
increases or decreases in nutrient levels. Macroinvertebrates feed on algae and other organic
material that enters the aquatic system from the surrounding watershed. Macroinvertebrates
are also an important food source for many aquatic vertebrates such as fish, which in turn serve
as an important food source for people and wildlife. Each of these groups of aquatic organisms
is sensitive in its own way to different human-induced disturbances.
The NRSA uses benthic macroinvertebrates, fish, and algae as biological indicators of
ecological condition. This is the first time three different biological assemblages have been
evaluated for one national survey. For each of these assemblages, scientists calculated a series
of metrics or individual measures and combined them into index scores. Results for each of
these assemblages are presented in this report.
However, research is still underway to determine how the different assemblage indices can be
accurately combined into one overall index. Therefore, the macroinvertebrate assemblage
and specifically the Macroinvertebrate Multimetric Index, or MMI was selected to represent
overall biological condition for purposes of this report. The Macroinvertebrate MMI integrates
a broad variety of informative macroinvertebrate metrics into one overall result and provides a
particularly strong picture of biological condition that is widely used by state water quality
agencies to assess and report on their rivers and streams. It was also used as the primary
indicator of biological condition in the 2004 WSA. Work is ongoing to explore methods for
integrating different assemblage indices into one overall index for future reports in this series.
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Background
The goal of the Clean Water Act is to restore and maintain the "chemical, physical, and
biological integrity" of the nation's waters. The NRSA examines these three aspects of water
quality through a set of commonly used and widely accepted indicators. It does not include all
aspects of aquatic ecosystem integrity or review all possible chemical, physical, or biological
stressors known to affect water quality.
This chapter discusses the indicators of biological condition that were measured and
analyzed for the NRSA, the chemical and physical aquatic indicators of stress, and a ranking of
the relative importance of the stressors in affecting biological condition. Results for each
indicator are shown for the nation's rivers and streams and for the three major climatic regions
(Eastern Highlands, Plains and Lowlands, and West). Chapter 4 presents the findings of the
human health indicators, and Chapter 6 presents indicator results for each of the nine NRSA
ecoregions. An analysis of the changes between this study and the 2004 WSA is presented in
Chapter 5. It is important to keep in mind that the overall NRSA findings should not be
compared directly to those of the WSA because of the difference in overall population surveyed
(rivers and streams versus streams only).
Indicators of biological condition
Ecologists evaluate the biological condition of rivers and streams by analyzing key
characteristics of the communities of organisms that live in them. These characteristics include
the composition and relative abundance of related groups of organisms that represent a
portion of the overall biological community. The NRSA focuses on three such key groups, known
as assemblages: benthic macroinvertebrates (aquatic insects, crustaceans, worms, and mollusks
that live at the bottom of rivers and streams); periphyton (algae that attach themselves to
stream and river beds, plants, rocks, and woody debris); and fish. This is the first time three
different biological assemblages were evaluated for one national statistical survey. The reason
for evaluating three distinct groups is to secure as robust an understanding of the biological
condition of rivers and streams as possible. This is because each assemblage plays a different
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role in the way that rivers and streams function. For example, algae are the base of the food
chain and capture light and nutrients to generate energy. They are sensitive to changes in
shade, turbidity, and nutrient levels. Macroinvertebrates feed on algae and other organic
material and are also an important food source for many other aquatic animals, such as fish; in
turn, fish serve as an important source of food for people and wildlife. Each of these groups of
aquatic organisms is sensitive in its own way to human disturbances.
NRSA researchers collected samples of these organisms and sent them to laboratories for
analysis, yielding data sets that provided the types and number of taxa (i.e., classifications or
groupings of organisms) found at each site. These were then analyzed to assess the condition of
each group of organisms, using well-established and tested indices. As a final step in
interpreting this information, analysts developed a ranking system for the stressors that affect
each of these biological assemblages.
Macro!nvertebrate Multimetric Index
Macroinvertebrates are widely used as indicators of biological condition because they
respond to human disturbance in known and predictable ways. Given their broad geographic
distribution, abundance, ease of collection, and connection to fish and other aquatic animals
(i.e., as a source of food), these organisms serve as excellent indicators of the biological quality
of rivers and streams and of the human stressors that affect them.
The Macro invertebrate Multimetric Index (MMI) is similar in concept to the Leading
Economic Index in that the total index score is the sum of scores for a variety of individual
measures (also known as metrics). To develop the Leading Economic Index, economists select
metrics such as manufacturers' new orders for consumer goods, building permits, money
supply, and other aspects of the economy that reflect economic growth. Similarly, to determine
the Macroinvertebrate MMI, ecologists selected six metrics indicative of different aspects of
macroinvertebrate community structure:
> Taxonomic richness the number of distinct taxa (family or genus) within different
taxonomic groups of organisms, within a sample. A sample with many different families
or genera, particularly within those groups that are sensitive to pollution, indicates
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Chapter 3. Condition of the Nation's River and Streams
least-disturbed physical habitat and water quality and an environment that is not
stressed.
> Taxonomic composition the proportional abundance of certain taxonomic groups
within a sample. Certain taxonomic groups are indicative of either highly disturbed or
least-disturbed conditions, so their proportions within a sample serve as good indicators
of condition.
> Taxonomic diversity the distribution of the number of taxa and the number of
organisms among all the taxa groups. Healthy rivers and streams have many organisms
from many different taxa groups; unhealthy streams are often dominated by a high
abundance of organisms in a small number of taxa.
> Feeding groups the distribution of macroinvertebrates by the strategies they use to
capture and process food from their aquatic environment, such as filtering, scraping,
grazing, or predation. As a river or stream degrades from its natural condition, the
distribution of animals among the different feeding groups will change, reflecting
changes in available food sources.
> Habits/habitats the distribution of macroinvertebrates by how they move and where
they live. A stream with a diversity of habitat types will support animals with diverse
habits, such as burrowing under streambed sediments, clinging to rocks, swimming, and
crawling. Unhealthy systems, such as those laden with silt, will have fewer habitat types
and macroinvertebrate taxa with less diverse habits (e.g., will be dominated by
burrowers).
> Pollution tolerance the distribution of macroinvertebrates by the specific range of
contamination they can tolerate. Highly sensitive taxa, or those with a low tolerance to
pollution, are found only in rivers and streams with good water quality. Waters with
poor quality will support more pollution-tolerant species.
The specific metrics chosen for each of these characteristics varied among the nine
ecoregions used in the analysis. Each metric was scored and then combined to create an overall
Macroinvertebrate MMI for each ecoregion. Analysts calculated a Macroinvertebrate MMI for
each site, factored in the river or stream length represented by the site, and then generated an
estimate of the river and stream length in a region, and nationally, with a given
Macroinvertebrate MMI score.
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Because it integrates a broad variety of informative macroinvertebrate metrics into one
overall result, the Macroinvertebrate MMI provides a particularly strong picture of biological
condition that is widely used by state water quality agencies to assess and report on their rivers
and streams. It was also used as the primary indicator of biological condition in the 2004 WSA.
For these reasons, and because it is not yet possible to integrate the indices for the three
different biological assemblages (macroinvertebrates, fish, and periphyton) into one overall
result, the Macroinvertebrate MMI serves as the key indicator of biological condition for the
NRSA as well. Work is ongoing to explore methods for integrating different assemblage indices
into one overall index for future reports in this series.
What are confidence intervals?
Confidence intervals (the small lines at the end of the bars in this report's
charts) convey the level of certainty or confidence in the condition
estimates presented in this report For example, for the Macroinvertebrate
MMI, the NRSA finds that 20.7% of the nation's river and stream length is in
good condition, with a confidence interval of +/- 2.8 %; this means that
there is a 95% certainty that the real value is between 17.9 % and 23.5 %.
The confidence interval depends primarily on the number of sites sampled.
As more rivers and streams are sampled, the confidence interval becomes
narrower, meaning there is more confidence in the findings. When fewer
rivers and streams are sampled, the confidence interval become broader,
meaning there is less certainty. Figure 7 shows an example of this pattern,
in which the confidence interval for the national results (the largest sample
size) is narrowest, whereas the confidence intervals for the major regions,
where a smaller number of streams were sampled, are generally broader.
Ultimately the breadth of the confidence interval is a tradeoff between the
need for increased certainty to support decisions and the money and
resources dedicated to monitoring.
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Findings for the
Macroinvertebrate Multimetric
Index
As illustrated in Figure 7, the
Macroinvertebrate MMI results
show that 21% of the nation's river
and stream length (247,558 miles) is
in good condition, 23% (276,796
miles) is in fair condition, and 55%
(659,788 miles) is in poor condition
compared to least-disturbed
reference conditions. Of the three
major climatic regions, the Eastern
Highlands has the highest
percentage of river and stream
length in poor condition (63%, or
272,171 miles), followed by the
Plains and Lowlands (58%, or
328,821 miles) and the West (30%,
or 58,796 miles).
Macroinvertebrate MMI
Total Length
(mi)
National e
(Lower 48) F
ND
Eastern -,
Highlands h
->V
M p
$P
ND
Plains and o
Lowlands F
West
247.558
276.796
659,738
9,634
Total 1,191,775
74,67!
33.428
272.171
Tolal 434.137
90,793
139,336
328,821
4,040
Total 5fr3,4W)
62,093
63,532
S8.796
1,529
Total m,94S
40
60
100
Percent of Length
I Good I 1 Fglr ^m Poor
Figure 7. Biological condition of the nation's rivers and streams
based on the Macroinvertebrate Multimetric Index. This index
combines metrics of benthic community structure and function into a
single index for each region.
Macroinvertebrate Observed/Expected Ratio of Taxa Loss
The Macroinvertebrate Observed/Expected Ratio of Taxa Loss (or 0/E Taxa Loss) measures
taxa that have been lost at a site. The taxa expected at individual sites (E) are predicted from a
model developed from data collected at least-disturbed sites. By comparing the list of taxa
observed (0) at a site with those expected to occur, the proportion of expected taxa that have
been lost can be quantified as the ratio of 0/E. 0/E taxa loss models are calibrated for the
specific natural conditions in each area for which they are used. For the NRSA, analysts
developed three 0/E taxa loss models to predict the extent of taxa loss in rivers and streams in
the Eastern Highlands, Plains and Lowlands, and West.
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O/E Taxa Loss values range from 0 (none of the expected taxa are present) to slightly
greater than 1 (more taxa are present than expected). Each tenth of a point less than 1
represents a 10% loss of taxa at a site, so a score of 0.9 indicates that 90% of the expected taxa
are present and 10% are missing. The quality of reference sites available for a region sets the
bar for what is expected, so regions with lower-quality reference sites will have a lower bar. It is
important to keep in mind that this indicator examines only one specific aspect of biological
condition (biodiversity loss), while the Macroinvertebrate MMI discussed above combines
multiple characteristics. Therefore, results are not expected to be the same.
Findings for O/E Taxa Loss
Findings for O/E Taxa Loss are presented in four categories: (1) less than 10% taxa loss, (2)
10%-20% taxa loss, (3) 20%-50%
taxa loss, and (4) more than 50%
taxa loss. As shown in Figure 8, 40%
of U.S. stream length lost less than
10% of taxa; 14% lost 10%-20% of
taxa; 29% lost 20%-50% of taxa; and
17% lost more than 50% of expected
taxa.
Macroinvertebrate O/E
National
(Lower 48)
Of the three major regions, the
West had the highest percentage of
stream length with 10% or less taxa
loss (57%) and the smallest
percentage with more than 50%
taxa loss (8%). The Plains and
Lowlands and the Eastern Highlands
had similar percentages of stream
length with more than 50% taxa loss
(19% and 17% respectively),
although the Plains and Lowlands
Eastern
Highlands
Plains and
Lowlands
West
"
GO
SO
Percent of Stream Length
~ 1U*. Tux* L :M> ESSD 2U-W\ TMXH LdhM
I 10-20% Taxa Lass -. son. Taxa Lo*i
Figure 8. Macroinvertebrate taxa loss in the nation's rivers and
streams as measured by the Observed/Expected Ratio of Taxa
Loss. This indicator displays the loss of taxa compared to the
reference sites for each region.
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had a greater percentage of stream length in the good range with less than 10% taxa loss (41%
versus 29% for the Eastern Highlands).
Fish Multimetric Index
Evaluating the variety and abundance of fish species (the fish assemblage) in streams and
rivers has been integral to water monitoring and water quality management programs for many
years. Fish are sensitive indicators of physical and chemical habitat degradation, environmental
contamination, migration barriers, and overall ecosystem productivity. They need plants,
insects, and small aquatic creatures to feed on; in-stream and streambank cover to shelter in;
appropriate streambed substrate conditions for spawning; and overhanging vegetation to
shade the water in which they live. They are affected by changes in temperature, dissolved
oxygen, pH, and myriad other physical and chemical constituents in water. They are also long-
lived, will move (if they can) to avoid pollutants or other stresses, and are economically,
culturally, and recreationally valuable. Determining the health and wellbeing of the fish
assemblage helps us evaluate the extent to which our waters are meeting the goals of the Clean
Water Act.
For the NRSA, scientists developed a Fish MMI using an approach that estimates expected
condition at individual sites. Separate indices were developed for each of the three major
climatic regions. These indices were based on a variety of metrics including taxa richness,
taxonomic composition, pollution tolerance, habitat and feeding groups, spawning habits
(specifically, the percent of individuals that deposit eggs on or within the substrate in shallow
waters), the number and percent of taxa that are migratory, and the percent of taxa that are
native. Fish were collected using standard electrofishing methods, tallied, and identified in the
field; except for those used for tissue analysis and as voucher specimens, they were then
released alive.
Findings for the Fish Multimetric Index
As shown in Figure 9, the NRSA Fish MMI indicates that 37% of the nation's river and stream
length (or 440,129 miles) is in good condition for this indicator, 15% (174,676 miles) is in fair
condition, and 36% (425,688 miles) is in poor condition compared to least-disturbed conditions.
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Chapter 3. Condition of the Nation's River and Streams
The remaining 13% of river and
stream length either is not
assessed or, for various reasons,
has insufficient data. Reasons why
this percentage is relatively large
include denials offish collection
permits by state, federal, or local
authorities (often because of the
possible presence of threatened or
endangered species) and
conditions and sites that were
deemed to be unsafe or unsuitable
for fish sampling.
Results for the Eastern
Highlands and Plains and Lowlands
are similar for this index. The
Plains and Lowlands region has the
highest percentage of stream
length in poor condition (41%, or
228,331 miles) and an almost
equal percentage in good
Total Length
(mi)
440,129
174,676
425,688
56,861
30,113
66,408
Total 1,193,775
National
(Lower 48)
165,949
70,106
148,002
34,554
8,789
6,937
Total 434,336
226,169
54,137
228,331
11,562
8,727
34,564
Total 563,490
48,011
50,433
49,354
10,745
12,498
24,907
Total 195,948
Eastern
Highlands
Plains and
Lowlands
Percent of Length
Good ^^H Poor I I Insufficent Sampling
Fair I I Not Assessed Zl No Data
Figure 9. Condition of the fish assemblage in the nation's rivers
and streams as measured by the Fish Multimetric Index
(EPA/NRSA). The index combines metrics of fish assemblage structure
and function into a single index for each region.
condition (40%, or 226,169 miles). For the Eastern Highlands, 35% of river and stream length
(148,002 miles) ranks in poor condition and 38% (165,949 miles) ranks in good condition. In the
West, on the other hand, good, fair, and poor rankings each apply to about 25% of river and
stream length. Note that the West has the largest percentage of stream length that was either
not assessed or had insufficient data.
Periphyton Multimetric Index
Periphyton, which are bottom-dwelling algae that attach themselves to stream and river
beds, plants, rocks, and woody debris, are an important foundation of many river and stream
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Chapter 3. Condition of the Nation's River and Streams
food webs. They also stabilize substrates and serve as habitat for many other organisms.
Because they are attached, they are affected by physical, chemical, and biological disturbances
in the water body.
The most common types of periphyton, diatoms, are particularly useful ecological indicators
because they are found in abundance in most river and stream ecosystems. Diatoms are algae
with inorganic cell walls composed of silica. They grow as single cells but also form filaments or
colonies. The great numbers of diatom species in rivers and streams provide multiple, sensitive
indicators of environmental change and of the specific conditions of their habitat.
Analysts developed the Periphyton MM I for the NRSA using diatoms. Samples from the
NRSA sample sites were identified and counted in the laboratory. The Periphyton MMI was
developed based on 12 metrics related to sensitive-tolerant species, functional composition,
and diversity composition:
> The proportion of sensitive-tolerant (diatom) taxa, which are metrics based on
proportion of sensitive and tolerant taxa from specific families of diatoms relative to all
taxa. These metrics included the proportion of all sensitive diatom taxa, the proportion
of several individual sensitive taxa, as well as the proportion of two tolerant taxa.
> Functional metrics include the proportion of highly motile diatom individuals, stalked
diatom individuals, and planktonic diatom, relative to all diatom taxa.
> Diversity metrics include the proportion of diatom taxa relative to the number of
individual diatoms counted, Shannon diversity of diatoms, and number of diatom
families per individual diatoms counted.
Findings for the Periphyton Multimetric Index
Based on the Periphyton MMI, 42% of the nation's river and stream length, or 497,738
miles, is rated in good condition compared to least-disturbed conditions, 14% (169,392miles) is
rated in fair condition, and 43% (507,007 miles) is rated in poor condition (Figure 10). Of the
three major climatic regions, the Eastern Highlands has by far the largest percentage of river
and stream miles in poor condition for this index (64%, or 277,761 miles). The West follows
with 39% (75,875 miles); for the Plains and Lowlands, 27% (153,371 miles) are rated poor
compared to least-disturbed condition.
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Chapter 3. Condition of the Nation's River and Streams
Aquatic indicators of stress
In the aquatic environment, a
stressor can be anything that could
adversely affect the community of
organisms that resides there. For the
NRSA, a set of chemical and physical
stressor indicators were selected
because they are widespread, of
potential concern, and can be
measured. These indicators of stress
were not intended to be all-
inclusive. Some important stressors
were not included in the survey due
to technical or cost constraints.
Several others primarily more
leading-edge indicators or more
complex analytes were sampled
but are still undergoing analysis and
are not included in this report. EPA
and its partners will be reporting on
Plains and G
Lowlands
.1 -
Percent of Length
Good I I Fair Poor [
Figure 10. Condition of periphyton assemblage in the nation's
rivers and streams based on the Periphyton Multimetric Index
(EPA/NRSA). This index combines metrics of periphyton pollution
sensitivity and taxa diversity.
these stressors in supplemental technical documents or in peer-reviewed journals.
NRSA indicators are based on direct measures of stress in the river or stream or in its
adjacent riparian areas. This report does not track the origins of these stressors, which can
come from a wide variety of human activities, natural sources, and land uses. A summary of the
national and regional results for chemical and physical stressors are shown in Figures 11
through 18. See the "Ranking Stressors" section below for a discussion of the severity of
impacts from individual stressors and the benefits that would be derived if those stressors were
reduced or eliminated. The purpose of these NRSA analyses is to help rank the different threats
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February 2013
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Chapter 3. Condition of the Nation's River and Streams
posed by stressors to our water resources, and assist in setting priorities for management
actions.
Chemical stressors
Four chemical stressors were assessed as indicators in the NRSA: total phosphorus, total
nitrogen, salinity, and acidification. These stressors were selected because of national or
regional concerns about the extent to which they might be affecting the quality of the biological
communities in rivers and streams, and to allow comparison of findings with the 2004 WSA.
Scientists developed thresholds for interpreting the data for these indicators from a set of least-
disturbed reference sites for each of the nine NRSA ecoregions, as described in Chapter 2.
These thresholds are the same as those used for the WSA.
Total phosphorus
Phosphorus is an essential nutrient in the environment and a common component of
fertilizers. Because of the naturally low concentrations of phosphorus in most rivers and
streams, even small increases can adversely affect water quality and biological condition. High
concentrations in rivers and streams may be associated with poor agricultural practices, runoff
from urban areas and lawns, leaking septic systems, or discharges from sewage treatment
plants. Too much phosphorus can lead to increased growth of algae and large aquatic plants;
decaying algae and plants reduce dissolved oxygen levels and water clarity, interfere with
swimming, and reduce aesthetic enjoyment of our waters. High levels of phosphorus can also
lead to algae blooms that can produce toxins harmful to human and animal health. Natural
variability in phosphorus concentrations is reflected in the regional thresholds for high,
medium, and low levels, which are based on least-disturbed reference sites for each of the nine
NRSA ecoregions.
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Chapter 3. Condition of the Nation's River and Streams
Findings for total phosphorus
Approximately 34% (407,225
miles) of the nation's river and
stream miles are in good condition
for phosphorus compared to least-
disturbed reference conditions, 26%
(308,177 miles) are in fair condition,
and 40% (475,598 miles) are in poor
condition (Figure 11). Of the three
major climatic regions, the Eastern
Highlands has the greatest
proportion of river and stream
length in poor condition based on
phosphorus levels (48%, or 208,435
miles).
Total nitrogen
Nitrogen is an essential nutrient
that, at high concentrations, can
Total Phosphorus
National
percent of Length
Figure 11. Total phosphorus concentrations in the nation's rivers
and streams (EPA/NRSA). Percent of river and stream length in
good, fair, and poor, condition based on phosphorus concentrations
compared to least-disturbed regional reference sites.
stimulate excess growth of algae and large aquatic plants when phosphorus levels are also high.
Common sources of excess nitrogen include fertilizers, wastewater, animal wastes, and
atmospheric deposition. Low dissolved oxygen levels, algae blooms, and degraded habitat
conditions for benthic macroinvertebrates and other aquatic life can result from high nitrogen
concentrations.
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Chapter 3. Condition of the Nation's River and Streams
Findings for total nitrogen
About 55% (660,168 miles) of the
nation's river and stream miles are in
good condition for nitrogen
compared to least-disturbed
reference conditions (Figure 12).
About 17% (201,517 miles) are rated
fair for nitrogen, and 28% (329,314
miles) are rated poor. Unlike the
findings for phosphorus, however,
the findings for the Plains and
Lowlands show the greatest
proportion of river and stream length
with high concentrations of nitrogen
(32%, or 182,824 miles), followed by
the Eastern Highlands (24%, or
103,128 miles) and the West (22%, or
43,362 miles).
Total Nitrogen
Total Length
(mil
National
(Lower 48)
:;
Eastern
Highlands
' ,
Plains and a
Lowlands
West
'
106
Percent of Length
I COW I I FSil ^m P'.Xi' I I N:: HHU
Figure 12. Total nitrogen concentrations in the nation's rivers
and streams (EPA/NRSA). Percent of river and stream length in
good, fair, or poor condition for nitrogen compared to least-
disturbed regional reference sites.
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Chapter 3. Condition of the Nation's River and Streams
Nutrients and eutrophication in rivers and streams
Eutrophication is a condition that results from high levels of nutrients in a water body and is
characterized by excessive plant growth. Although eutrophication is a natural process, human
activities can accelerate it by increasing the rate at which nutrients and organic substances enter
waters from surrounding watersheds. Agricultural and urban runoff, leaking septic systems, sewage
discharges, eroded stream banks, and similar sources can increase the flow of nutrients and organic
substances into rivers and streams, and subsequently into downstream lakes and estuaries. These
substances can over-stimulate the growth of algae and aquatic plants, creating eutrophic conditions
that interfere with recreation and the health and diversity of insects, fish, and other aquatic organisms.
Nutrient enrichment due to human activities has long been recognized as one of the leading
problems facing our lakes, reservoirs, and estuaries. It has also been more recently recognized as a
contributing factor to river and stream degradation. Nutrient over-enrichment of rivers and streams is
a problem because of the negative impacts on aquatic life, adverse health effects on humans and
domestic animals, aesthetic and recreational use impairment, and excessive nutrient input into
downstream water bodies.
Excess nutrients can lead to excessive growth of phytoplankton (free-floating algae) in slow-moving
rivers, periphyton (algae attached to the substrate) in shallow streams, and macrophytes (aquatic
plants large enough to be visible to the naked eye) in all waters. Unsightly filamentous algae can
impair the aesthetic enjoyment of rivers and streams. In more extreme situations, excessive growth of
aquatic plants can slow water flow in flat streams and canals, interfere with swimming, snag fishing
lures, and clog water intake screens.
Nutrient enrichment in streams has also been demonstrated to affect animal communities. For
example, declines in invertebrate community structure have been correlated directly with increases in
phosphorus concentration. High concentrations of nitrogen in the form of ammonia (NH3) are known
to be toxic to aquatic animals. Excessive levels of algae have also been shown to be damaging to
invertebrates. Finally, fish and invertebrates will experience growth problems and can even die if either
oxygen is depleted or pH increases are severe; both of these conditions are symptomatic of
eutrophication.
As a river or stream system becomes more enriched by nutrients, different species of algae may
spread and species composition can shift. However, unless such species shifts cause clearly
demonstrable symptoms of poor water quality such as fish kills, toxic algae, or very long streamers
of filamentous algae the general public is unlikely to be aware of a potential ecological concern.
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Chapter 3. Condition of the Nation's River and Streams
Salinity
Salts can be toxic to freshwater plants and animals and can make water unsafe for drinking,
irrigation, and livestock watering. Excess salinity can occur in areas where evaporation is high
and made worse by repeated use of water for irrigation or water withdrawals; where road de-
icers are applied; and in mining, oil drilling, and wastewater discharges. Conductivity (a
measure of water's ability to pass an electrical current) was used as a measure of salinity for
this study.
Findings for salinity
Salinity is not a problem in 87% of the nation's river and stream miles (or 1,030,381 miles).
About 10%, or 117,423 miles, are rated fair for salinity, and 4% (42,336 miles) are rated poor
compared least-disturbed sites in
the nine NRSA ecoregions (Figure
13). All three major climatic regions
have about 3%-4% of stream length
rated poor for salinity. However, the
Eastern Highlands region has a
higher percentage of waters rated
fair (14%, or 62,283 miles),
compared to 7% (41,401 miles) for
the Plains and Lowlands and 7%
Salinity
National
(Lower 48)
: y
Eastern G
Highlands
,
r-*~ .
(13,738 miles) for the West.
Acidification
Streams and rivers can become
acidic because of acid deposition
(acid rain), or acid mine drainage,
particularly from coal mining. These
problems tend to be focused in a
few geographic areas. Streams and
Plains and
Lowlands
West
Percent of Length
! I 1 Fair ^m POQI
No Date
Figure 13. Salinity conditions in the nation's rivers and streams
(EPA/NRSA). Thresholds are based on conditions of least-disturbed
regional reference sites. Indicator based on electrical conductivity.
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Chapter 3. Condition of the Nation's River and Streams
rivers can also be acidic because of natural conditions, such as high levels of dissolved organic
compounds. Some fish and macroinvertebrates are acid-sensitive and can only tolerate small
changes in acidity. Acidification can also indirectly affect aquatic life by releasing toxic metals
such as aluminum from soils into the water.
The NRSA identifies the extent to which flowing waters are not acidic, are naturally acidic
(similar to reference conditions), and are acidic because of anthropogenic sources. This last
category includes rivers and streams that are acidic due to chronic or episodic acid deposition,
or because of mine drainage.
Acid deposition forms when smokestack and auto emissions (primarily sulfur dioxide and
nitrogen oxides) combine with moisture in the air to form dilute solutions of sulfuric acid and
nitric acid. It can also occur in dry form, such as the particles that make up soot. Acid deposition
on sensitive watersheds can have damaging effects on soils, vegetation, and aquatic systems.
To assess the effect of acid deposition on flowing waters, the NRSA relied on a measure of
water's ability to buffer inputs of acids, called acid-neutralizing capacity (ANC). When ANC
values fall below zero, water is considered acidic and can be either directly or indirectly toxic to
aquatic life. When ANC is between 0 and 25 milliequivalents, the water is considered sensitive
to episodic acidification during rainfall events. These threshold values were determined based
on values derived from the National Acid Precipitation Assessment Program.
Acid mine drainage occurs when water moves through mines and mine tailings, combining
with sulfur released from certain minerals to form strong solutions of sulfuric acid and
mobilizing toxic metals. The acidity of waters in mining areas can also be assessed by using ANC
values. However, since mine drainage also produces very high concentrations of sulfate, sulfate
serves as an indicator of the influence of mines on streams and rivers. Thus when ANC values
and sulfate values are low, acidity can be attributed to acid rain; when ANC values are low and
sulfate values are high, acidity can be attributed to acid mine drainage.
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February 2013
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Chapter 3. Condition of the Nation's River and Streams
Findings for acidification
Figure 14 shows that the vast
majority of U.S. rivers and streams
(99%, or 1,178,614 miles) are not
affected by acidification.
Anthropogenic sources in the
remaining waters include acid
deposition (0.1%, or 1,245 miles of
river and stream length), mine
drainage (0.2%, or 2,902 miles) and
episodic acidity due to high runoff
events (0.2%, or 2,825 miles). About
0.3% (5,233 miles) of river and
stream length is affected by acidity
from natural sources. In the Eastern
Highlands region, acid mine drainage
affects 0.6% (2,391 miles) of river
and stream length and acid
Eastern
Highlands °'3 0<*
Enl :
1 4
Percent of Length
ItonAraJE ^m f.a-&pao&;
Figure 14. Acidification in the nation's rivers and streams
(EPA/NRSA).
deposition affects 0.3% (1,425 miles). In the Plains and Lowlands region, 0.5% of river and
stream length, or 2,825 miles, is affected by episodic acidity.
Physical habitat stressors
Many human activities such as construction, agriculture, removal of vegetation near
streams, land development, and spread of impervious surfaces (such as roads and parking lots)
stress the physical condition of rivers and streams and, consequently, stress fish and other
aquatic organisms. The NRSA focuses on four indicators of physical habitat conditions in rivers
and streams: excess streambed sediments, in-stream fish habitat, riparian (streamside)
vegetation, and riparian disturbance.
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Chapter 3. Condition of the Nation's River and Streams
Excess streambed sediments
The size and shape of natural stream and river channels and the size of the particles that
make up their beds reflect the interplay between sediment inputs and the flow of water.
Human uses of the landscape, such as agriculture, construction, and urbanization, can increase
the amount of fine sediments entering streams and rivers. The same types of land uses can also
change the amount and timing of water runoff into channels, especially when they increase the
amount of impervious land surfaces. Typically these hydrologic alterations increase the
frequency of high-magnitude floods, and channels can respond by down-cutting (incising),
eroding their banks, and washing away important aquatic habitat. The most common response
to increased fine sediment inputs is a shift to a channel formed of finer, more unstable particles
as these sediments are transported downstream. These excess fine sediments can fill in the
habitat spaces between stream cobbles and rocks where many aquatic organisms live or breed.
For the NRSA, scientists measured the ratio between the particle size of observed
sediments to the size of sediments each river or stream can move or scour during its flood
stage, based on measures of the size, slope, and other physical characteristics of the stream
channel. This ratio, also known as relative bed stability (RBS), differs naturally among regions
depending on characteristics such as geology, topography, hydrology, natural vegetation, and
natural disturbance history. Very high RBS, indicating channels with beds that are substantially
more stable than expected (e.g., evidence of hardening after prolonged scouring or reduced
fine sediment supply, concrete-lined channels) was not assessed by the NRSA as it is difficult to
determine the role of human alteration in stream coarsening on a national scale. In this report,
the NRSA addresses bed sediment conditions at the low end of RBS, indicating lower-than-
expected streambed stability, or higher excess sedimentation, resulting from high inputs of fine
sediments or increases in stormflows.
Findings for excess streambed sediments
About 55% (654,401 miles) of the nation's river and stream length has streambed sediment
characteristics in good condition compared to regional reference conditions (Figure 15).
Streambed sediment characteristics are rated fair in 30% (351,696 miles) of river and stream
length and poor in 15% (177,493 miles). For this indicator, a slightly higher percentage of rivers
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Chapter 3. Condition of the Nation's River and Streams
and streams in the West are rated
in poor condition (18%, or 34,539
National
miles) than in the Eastern Highlands (Lower 43)
(15%, or 63,111 miles) or the Plains
and Lowlands (14%, or 79,844
miles).
In-stream fish habitat
The healthiest and most diverse
communities offish and
macroinvertebrates are found in
rivers and streams that have
complex and varied forms of
habitat, such as boulders, undercut
banks, tree roots, and logs within
the stream banks. Human use of
rivers and streams and their
Excess Sedimentation
Total Length
(miles)
20 *0 60
Percent of Length
100
adjacent riparian areas often results Fi9ure 15- Excess streambed sediment in the nation's rivers and
streams (EPA/NRSA).
in the removal or loss of much of this habitat, which in turn affects the biological condition of
the stream. The NRSA uses a habitat complexity measure that sums the amount of in-stream
fish habitat and concealment features such as undercut banks, boulders, large pieces of wood,
brush, and cover from overhanging vegetation within the water body and its banks. Because
this measure differs naturally within and among ecoregions, low in-stream fish habitat
complexity was assessed by comparison with expected values at least-disturbed sites adjusted
for factors such as geography and climate within ecoregions.
Findings for in-stream fish habitat
Compared to least-disturbed reference condition, 68% (816,510 miles) of the nation's river
and stream length is in good condition for in-stream fish habitat, 20% (239,627 miles) is in fair
condition, and 11% (136,675 miles) is in poor condition (Figure 16). Of the major climatic
regions, the highest proportion of river and stream length in poor condition for in-stream
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Chapter 3. Condition of the Nation's River and Streams
habitat is in the Plains and
Lowlands, where 15% (84,889
miles) of river and stream length is {Lower45)
rated poor. In the West, 10%
(18,786 miles) of river and stream
length is rated poor, as is 8%
(32,999 miles) in the Eastern
Highlands region.
Riparian vegetative cover
A river or stream can be
buffered from the effects of human
disturbance in the watershed by
varied, multi-layered vegetation in
the land corridor that surrounds it.
Healthy, intact vegetative cover in
these riparian areas can help
reduce nutrient and sediment
runoff from the surrounding
In-Stream Fish Habitat
Figure 16. In-stream habitat in the nation's rivers and streams
(EPA/NRSA).
landscape, prevent streambank erosion, provide shade to reduce water temperature, and
provide leaf litter and large wood (such as branches and logs) to serve as food, shelter, and
habitat for aquatic organisms. The NRSA uses a measure of riparian vegetative cover that sums
the amount of cover provided by three layers of riparian vegetation: the ground layer, woody
shrubs, and canopy trees. Because the amount and complexity of riparian vegetation differs
naturally within and among ecoregions, lower-than-expected riparian vegetative cover was
assessed by comparison with expected values at least-disturbed sites estimated within
ecoregions.
Findings for riparian vegetative cover
Over half of the nation's river and stream length (56%, or 669,687 miles) is in good
condition for riparian vegetative cover compared to least-disturbed regional reference
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February 2013
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Chapter 3. Condition of the Nation's River and Streams
conditions. Another 20% (240,376
miles) is in fair condition, and 24%
(283,712 miles) is in poor
condition. The Eastern Highlands
has the highest proportion of
rivers and streams with poor
riparian vegetative cover (27%, or
116,534 miles), followed by the
Plains and Lowlands (23%, or
130,820 miles) and the West
(19%, or 36,359 miles) (Figure 17).
Riparian disturbance
The closer harmful human
activities are to a river or stream,
the more impact they will have on
it. The NRSA uses a direct
measure of riparian human
Riparian Vegetation Cover
Total Length
(miles)
National G
(Lower 48)
Eastern
Highlands
Plains and
Lowlands
West
283,712
Total 1,193L775
215,996
40
60
80
100
Percent of Length
Zl Good I I Fair I^H Poor
Figure 17. Riparian vegetative cover in the nation's rivers and
streams (EPA/NRSA).
disturbance that tallies 11 specific forms of human activities and their proximity to the river or
stream in 22 riparian plots along the water body. Examples of human disturbance include
roads, pavement and cleared lots, buildings, pastures and rangeland, row crops, dams, and
logging or mining operations. The same disturbance criteria were applied to define high,
medium, and low riparian disturbance in streams and rivers nationwide. For example, a river or
stream scored medium if one type of human influence was noted in at least one-third of the
riparian plots, and scored high if one or more types of disturbance were observed at all of the
plots.
Findings for riparian disturbance
Thirty-four percent (411,035 miles) of the nation's river and stream length had low levels of
riparian disturbance and scored as good for this indicator, 46% (543,374 miles) had medium
levels of disturbance and were rated as fair, and 20% (239,366 miles) had high levels of
February 2013
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Chapter 3. Condition of the Nation's River and Streams
Riparian Disturbance
National G
(Lower 48)
*
Eastern
Highlands
'
Plains and
Lowlands
West
, --
411,035
543.374
239,366
T01»11,193,775
143.227
1&6.179
94,931
Total 434,337
210,813
25S.752
96,925
Total 563,490
58,995
91,443
47,510
Total 195,948
disturbance and were rated poor
for this indicator. The most
widespread types of riparian
disturbance were roads, pastures
and rangeland, and buildings.
Compared to the other physical
stressors discussed above, a much
greater proportion of U.S. river and
stream length was rated as fair
(with medium levels of riparian
disturbance) and a significantly
lower percentage of river and
stream length was rated as good.
The three major climatic regions
had similar proportions of river and
stream length in the
good/fair/poor categories,
Figure 18. Riparian disturbance in the nation's rivers and streams
although the West had the highest (EPA/NRSA).
proportion of stream length rated as poor for riparian disturbance (24%, or 47,510 miles) and
the lowest proportion rated as good (29%, or 56,995 miles) (Figure 18).
Ranking stressors: relative extent, relative risk, and attributable risk
One of the key roles of the NRSA, and of all assessments in this series, is to provide
perspective on key stressors affecting the biological condition of our waters. This includes
estimating the benefits that would be derived if those stressors were reduced or eliminated.
For the NRSA, analysts use three approaches to assess the influence of stressors on the
ecological condition of the nation's rivers and streams. The first, relative extent, looks at how
extensive any particular stressor is (e.g., how many miles of rivers and streams have excess
phosphorus concentrations). The stressor discussions earlier in this chapter are based on
relative extent. The second approach, relative risk, examines the severity of the impact from an
Zfl
40
60
108
Percent of Length
CJ.Wl 1=) Fil ^m P.13I
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Chapter 3. Condition of the Nation's River and Streams
individual stressor when it is found at high levels (e.g., how much more likely poor biological
conditions are when phosphorus levels are high). To assess how ecological conditions may
change when a stressor is reduced or removed requires taking both of these perspectives into
consideration; this leads to the third approach, attributable risk. Attributable risk is derived by
combining the first two risk values into a single number that estimates the expected
improvement in biological conditions if that stressor is eliminated.
Throughout this section, stressors are assessed and reported on independently and as such
do not sum to 100%. Most rivers and streams are likely to experience multiple stressors
simultaneously, which can result in
cumulative effects not accounted for
in this analysis.
Relative extent
It is important for water resource
managers to take into account how
extensive a stressor is when setting
priority actions at the national,
regional, and state scale. Stressors
that can be found in all geographic
areas but are not pervasive do not
have high relative extent.
Nationally, the most widespread
stressors measured as part of the
NRSAare phosphorus and nitrogen
(Figure 19). Phosphorus levels are high
compared to least-disturbed
conditions in 40% of river and stream
length; nitrogen is found at high levels
in 28% of river and stream length.
Extent of Stressor
National
(Lower 48) RVC
~-l':'-'
Eastern
Highlands RVC
'
-
,..
rf \
Plains and
Lowlands
I! '
West
20 40 60 80
Percent of Length
In Poor Condition
P = Talal Phosphorus "
N = Total Nitrogen I
RVC = Riparian Vegetation Cove!
RD - Riparian Disturbance I
SS = Excess Sedimentation
1-sFH = InStrearn Fish Ha&Ha1
Sal = Salinity
Acict = Acidification
Figure 19. Relative extent of stressors in the nation's rivers and
streams (EPA/NRSA).
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Chapter 3. Condition of the Nation's River and Streams
Riparian vegetative cover is rated poor in 24% of river and stream length, and riparian
disturbance is rated at high levels in 20%. With a few exceptions, the extent of these stressors
shows a similar pattern across the three major climatic regions.
Relative risk
Relative risk is a way to examine the severity of the impact of a stressor when it occurs.
Relative risk is used frequently in the human health field. For example, a person who smokes is
15 to 30 times more likely to get lung cancer or die of lung cancer than a person who does not.1
Similarly, scientists can examine the likelihood of finding poor biological conditions in a river or
stream when phosphorus concentrations are high, relative to the likelihood of poor biological
conditions when phosphorus concentrations are low. When these two likelihoods are
quantified, their ratio is called the relative risk. A relative risk value of 1 means that you are just
as likely to find poor biological conditions when the stressor is high as when it is low in
essence, no demonstrable effect. A relative risk of 1.5, however, means that you are 50% more
likely to find poor biological conditions when a stressor is high.
Results of the relative risk analyses for NRSA are presented in the middle panels of Figures
20 through 22. Relative risk differs for macroinvertebrates, fish, and periphyton. For
macroinvertebrates nationally, the relative risks are largest for total phosphorus, excess
sedimentation, and acidification, all in the range of 1.5. In other words, when these stressors
occur in excess levels, streams and rivers are 50% more likely to have poor macroinvertebrate
communities than when these stressors are low. The relative risks posed by the various
stressors differ in the three major climatic regions, with the West showing the most sensitivity
to all the stressors compared to the other regions. In the West, macroinvertebrate communities
are 200%-300% more likely to be in poor condition when stressors are at excessive levels
compared to when they are at normal levels.
1 Centers for Disease Control. Lung cancer: Risk factors.
http://www.cdc.gov/cancer/lung/basic info/risk factors.htm (accessed November 7, 2012).
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Chapter 3. Condition of the Nation's River and Streams
Extent of Stressor
Relative Risk
Macroinvertebrate MMI
Attributable Risk
Macroinvertebrate MMI
20 40
80 100 1
5 o
Percent of Length
In Poor Condition
^H P = Total Phosphorus
^H N = Total Nitrogen
RVC = Riparian Vegetation Cove
i i RD = Riparian Disturbance
Relative Risk Factor
20 40 60 80 100
Percent of Length
SS = Excess Sedimentation
I l-sFH = InStream Fish Habitat
I Sal = Salinity
I Acid = Acidification
Figure 20. Relative extent, relative risk, and attributable risk to macro!nvertebrates based on the
Macroinvertebrate Multimetric Index (EPA/NRSA).
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Chapter 3. Condition of the Nation's River and Streams
National
(Lower 48)
Eastern
Highlands
Plains and
Lowlands
"
West
Extent of Stressor
Relative Risk to
Fish MMI
Attributable Risk
Fish MMI
40 60 80 1001
Percent of Length
In Poor Condition
234
Relative Risk
5 0
20 40 60 80
Percent of Length
100
P = Total Phosphorus I
N = Total Nitrogen I
RVC = Riparian Vegetation Cover I
RD = Riparian Disturbance I
SS = Excess Sedimentation
l-sFH = InStream Fish Habitat
Sal = Salinity
Acid = Acidification
Figure 21. Relative extent, relative risk, and attributable risk to fish based on the Fish Multimetric Index
(EPA/NRSA).
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Chapter 3. Condition of the Nation's River and Streams
Extent of Stressor
Relative Risk
Periphyton MMI
Attributable Risk
Periphyton MMI
National
(Lower 48)
20 40 60 80 1001 2 3 4 50
Relative Risk Factor
Percent of Length
In Poor Condition
20 40 60 80 100
Percent of Length
P = Total Phosphorus
N = Total Nitrogen
RVC = Riparian Vegetation Cover
RD = Riparian Disturbance
SS = Excess Sedimentation
l-sFH = InStream Fish Habitat
Sal = Salinity
Acid = Acidification
Figure 22. Relative extent, relative risk, and attributable risk to periphyton based on the Periphyton
Multimetric Index (EPA/NRSA).
Previous studies in the mid-Atlantic Highlands and in the western U.S. provided some
evidence of very different patterns of relative risk for macroinvertebrates, fish, and periphyton.
The NRSA results are inconclusive on this. The relative risk values are consistently low for
macroinvertebrates, both nationally and in the Eastern Highlands and Plains and Lowlands. For
periphyton, relative risk scores are consistently high for salinity and variable by region for the
other stressors. The relative risk values for fish are somewhat variable across the three regions.
Attributable risk
Attributable risk represents the magnitude or importance of a potential stressor and can be
used to help rank and set priorities for policymakers and managers. Attributable risk is derived
by combining relative extent and relative risk into a single number for purposes of ranking (see
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Chapter 3. Condition of the Nation's River and Streams
third panels of Figures 20 through 22). Conceptually, attributable risk provides an estimate of
the proportion of poor biological conditions that could be reduced if high levels of a particular
stressor were eliminated. This risk number is presented in terms of the percent of length that
could be improved.
For example, as noted above, phosphorus occurs at excess levels in 40% of river and stream
length. Rivers and streams are 50% more likely to have poor conditions for macroinvertebrates
when phosphorus is high (relative risk of 1.5). Relative extent and relative risk combined result
in an attributable risk level of about 17%. That is, if phosphorus levels were reduced, one might
expect to see 17% of river and stream length improve to good conditions for
macroinvertebrates. For periphyton, the attributable risk for phosphorus is 18%; for fish, it is
22%. In the West, where relative risks are large, the amount of improvement in river and
stream length to good biological condition is correspondingly large.
Some stressors can have fairly large relative risk but small attributable risk (regardless of
biological community) because the relative extent of this problem is small. For example,
national relative risk levels for salinity are between 1.3 (for macroinvertebrates) and 1.7 (for
fish), yet excess salinity occurs in only 4% of river and stream length nationally. Therefore, the
resulting attributable risk levels are small.
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Chapter 4. Human Health Considerations in the Nation's
Rivers and Streams
Background
In addition to physical, chemical, and biological indicators of the condition of the nation's
rivers and streams, the NRSA includes two indicators that provide insight into potential risks to
human health: mercury in fish tissue, and the pathogen indicator enterococci.
Most human exposure to mercury is through the consumption offish. When pregnant
women, nursing mothers, and women who might become pregnant eat fish with mercury
concentrations above specified thresholds for human protection, this poses a
neurodevelopmental health risk to fetuses, babies, and young children. States issue
consumption advisories for specific fish species and water bodies when state or local sampling
results indicate elevated mercury concentrations. More information on fishing advisories is
available from local health agencies and
water.epa.gov/scitech/swguidance/fishshellfish/fishadvisories/index.cfm.
Enterococci are indicators of the presence of fecal material in water and, therefore, of the
possible presence of disease-causing bacteria, viruses, and protozoa. These pathogens can
sicken swimmers and others who use rivers and streams for recreation or eat raw shellfish or
fish.
Mercury in fish tissue and enterococci were not evaluated for the 2004 WSA. These results
are not intended to represent the full range of pollutants in rivers and streams that might
adversely affect human health.
Mercury in fish tissue
Mercury is widely distributed in the environment, due to both natural processes and human
activities. It enters the atmosphere from the natural degassing of the earth's crust (e.g., from
volcanic action) and from some industrial sources such as coal-burning power plants and
hazardous waste incineration. Once in the atmosphere, it can circulate widely and be deposited
on land and water through rain and snow.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Microorganisms in water convert inorganic mercury to a toxic form of organic mercury
called methylmercury. Methylmercury accumulates in fish, primarily in muscle tissue. Nearly all
fish contain traces of mercury, and the amount of mercury measured in fish tissue usually
increases with fish age and size. It also varies among fish species those that prey on other
fish typically accumulate higher concentrations of mercury than those that eat insects or other
aquatic organisms. Measuring mercury levels in fish is critical because about 80% of all fish
consumption advisories currently in effect involve mercury. Human health effects can include
damage to the immune and nervous systems; developing embryos are particularly at risk.
For the NRSA, field sampling teams applied consistent methods to collect fish from 542
randomly selected river segments (fifth-order or larger) distributed across the lower 48 states.
These 542 sites are a subset of the total sites sampled for the NRSA. The teams also collected
additional fish at about 10% of the sites to evaluate field sampling variability. Each sample was
a composite, consisting of multiple adult fish of the same species and similar size. Field teams
selected fish species that people commonly eat, including largemouth and smallmouth bass,
walleye, and various trout and catfish species. Fish fillet contaminant levels were then
compared to EPA's human health screening values.
EPA analyzed the NRSA fish tissue samples for total mercury in addition to other
contaminants. Following EPA guidance, scientists made the conservative assumption that all
mercury is present in fish tissue as methylmercury. The human health screening value used to
interpret mercury concentrations in fillet tissue is 0.3 milligrams of methylmercury per kilogram
of tissue (wet weight) or 300 parts per billion, which is EPA's tissue-based water quality
criterion for methylmercury. This threshold represents the concentration that, if exceeded, can
be harmful to human health.
For a wide variety of additional chemicals (including selenium, pesticides, polychlorinated
biphenyls (PCBs), and other contaminants of emerging concern), analyses are still underway
and will be presented in future publications.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Findings for mercury in fish tissue
The human health fish tissue indicator focused on fifth-order and larger rivers. This sub-
population contains 106,247 river miles, which represents 9% of the total NRSA river and
stream miles associated with all flowing waters (1,193,755 miles). The NRSA limited the target
population to fifth-order and larger rivers both because of resource constraints and the need to
focus the assessment on waters that would likely support a population of fish of the size that
are typically sought for human consumption. Given that levels of mercury in fish tissue vary but
tend to increase with size and trophic level, this focus was intended to address both fish taken
for subsistence and for sportfishing and produce assessment results that could be comparable
across all the waters sampled. The sampled population is the portion of the target sub-
population for which we can determine whether mercury levels were above or below the
human-health-based screening value. The sampled population, 49% of the target sub-
population, consists of 51,544 river miles. Mercury levels in the other 51% of the target sub-
population (54,703 river miles) cannot be assessed because sites could not be sampled due to a
variety of factors, including inability to obtain permits, lack of suitable fish, insufficient time to
collect fish samples, and denial of access to sites.
All fillet samples analyzed for the NRSA contain quantifiable levels of mercury. Fish tissue
results indicate that 13,144 river miles have concentrations above the 300 parts per billion
human-health-based water quality criterion for mercury; 38,400 river miles do not. Figure 23
summarizes the target and sampled populations for the fish tissue indicator.
In the Eastern Highlands, 3,419 river miles exceed the human health screening value for
mercury in fish tissue and 11,200 miles do not. In the Plains and Lowlands, the screening value
is exceeded in 7,424 river miles and not exceeded in 22,315 miles. In the West, 2,301 miles
exceed the screening value and 4,885 miles do not exceed it. Particularly in the West and the
Plains and Lowlands, a high percentage of river length was not sampled for mercury in fish
tissue. Results from the sampled sites cannot be extrapolated to these unassessed waters.
Figure 24 shows the percent of rivers and streams in each of the three ecoregions that were
sampled for mercury in fish tissue.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
River and Stream Miles Identified
as Target and Not Target
for Human Health Fish
Tissue Assessment
(Total = 1,193,775)
Human Health Fish
Tissue Assessment:
Target Population Only
(in Miles)
(Total = 106,247)
Human Health Fish
Tissue Assessment:
Sampled Population Only
(in Miles)
(Total = 51,544)
106,247
HH Fish Tissue
Not Target
HH Fish Tissue
Target
38,400
13,144
SampledDoes Not
Exceed HH Criteria
SampledExceeds
HH Criteria
Not Sampled
13,144
Does Not Exceed
HH Criteria
Exceeds
HH Criteria
Figure 23. Human health fish tissue assessment for target (middle graphic) and sampled populations (right
graphic) of the nation's rivers (EPA/NRSA). The fish tissue target population (106,247 miles of fifth order and larger
rivers) is a subset of the overall NRSA population for all other indictors. No assessment can be made for the 54,703 miles
of the target population that were not sampled, and the fish tissue target population assessment cannot be extrapolated
to the entire rivers and streams target population. The fish tissue sampled population assessment (right graphic, 51,544
miles) cannot be extrapolated to either the entire rivers and streams target population, or the fish tissue target
population.
Assessment of Mercury in Fish Tissue NRSA 2008/2009
100%
90%
80%
Not Sampled
Sampled
Eastern
Highlands
Plains and
Lowlands
Western
Mountains
Figure 24. Percent of fish tissue target population sampled for mercury in
fish tissue in the three major climatic regions of the U.S. (EPA/NRSA).
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Pathogen indicators (enterococci)
Enterococci are bacteria that live in the intestinal tracts of warm-blooded animals, including
humans, and therefore indicate possible contamination of streams and rivers by fecal waste.
Enterococci are typically not considered harmful to humans, but their presence in the
environment may indicate that other disease-causing agents such as viruses, bacteria, and
protozoa may also be present. Epidemiological studies conducted at beaches affected by
human sources of fecal contamination have established a relationship between the density of
enterococci in ambient waters and the elevated incidence of gastrointestinal illness in
swimmers. Other potential health effects can include diseases of the skin, eyes, ears, and
respiratory tract. Eating fish or shellfish harvested from waters with fecal contamination can
also result in human illness. Significant economic losses can occur due to beach closures,
swimming and boating bans, and closures of fishing and shellfishing areas due to fecal
contamination.
Sources of fecal indicator bacteria such as enterococci include wastewater treatment plant
effluent, leaking septic systems, stormwater runoff, sewage discharged or dumped from
recreational boats, domestic animal and wildlife waste, improper land application of manure or
sewage, and runoff from manure storage areas, pastures, rangelands, and feed lots. There are
also natural, non-fecal sources of fecal indicator bacteria, including plants, sand, soil, and
sediments, that contribute to a certain background level in ambient waters and vary based on
local environmental and meteorological conditions. In some situations, background levels of
fecal indicator bacteria can be high and not necessarily related to the occurrence of fecal
contamination or human health risks. Watershed-scale sanitary investigations can provide
important context to fecal bacteria monitoring results.
For the NRSA, water samples were analyzed using a process known as quantitative
polymerase chain reaction, or qPCR, a methodology that facilitates the detection of DNA
sequences unique to these bacteria. Analysts compared the NRSA results to a new EPA qPCR
threshold for protecting human health in ambient waters designated for swimming (1,280
calibrator cell equivalents per 100 milliliter).
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Findings for enterococci
About 85% (1,009,897 miles) of the
nation's river and stream length are in
good condition for enterococci (i.e.,
samples do not exceed the threshold
level). About 9% (105,970 miles) are in
poor condition, with samples that
exceed the threshold level. Nearly 7% of
river and stream length is not assessed
for enterococci or has no data. Of the
three major climatic regions, the
Eastern Highlands has the highest
percentage of stream length exceeding
the threshold (12%, or 49,836 miles),
followed by the Plains and Lowlands
(9%, or 51,013 miles). In the West, only
3% (8,121 miles) of stream length
exceed the threshold for enterococci
(Figure 25).
8.9%
Enterococci
Total Length
(mi)
Tj^82.
82.97,
1,009,897
105,970
55,076
22,830
Total 1,193,775
360,236
49,836
8,472
15,793
Total 434,337
480,717
51,013
28,615
3,145
Total 563,490
168,944
5,121
17,989
3,895
Total 195,945
20 40 60 80
Percent of Length
100
Does Not Exceed
Exceeds
J Not Assessed
I No Data
Figure 25. Enterococci human health thresholds exceedance
in the nation's rivers and streams (EPA/NRSA). Percent of
rivers and streams length exceeding or not exceeding EPA human
health thresholds for enterococci.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Urban rivers
Cities share one key characteristic: they are comparatively small areas full of people, buildings, and
businesses. The urban rivers that flow through and near them can serve as vital economic resources,
often providing drinking water and recreational opportunities, boosting tourism, and improving the
quality of city life. However, urban rivers also take on large, concentrated amounts of pollution from a
variety of sources, including industrial discharges, mobile sources (e.g., cars/trucks), residential and
commercial wastewater, trash, and polluted stormwater runoff from urban landscapes. As urban
populations often share centralized water sources, this pollution creates public and environmental
health hazards like lowered drinking water quality, water bodies that are not safe to swim in, and fish
that aren't safe to eat. NRSA fish tissue sampling offered an opportunity to target these important
waters to determine if a wide range of toxic substances were of concern.
To assist researchers in evaluating urban water quality, EPA identified each site selected for NRSA as
either urban or non-urban. Urban waters were defined by intersecting a modified version of the Census
Bureau national urban boundary geographic information system (CIS) coverage with the NHD-Plus.
This essentially gave EPA a way to identify whether selected river and stream sites were within areas
identified as contiguous census block groups and urban clusters meeting Census Bureau minimum
population density requirements of at least 2,500 people.
From the 1,924 sites sampled for the NRSA, a subset of 164 urban river sites across the country were
sampled for additional data analysis. Fish tissue samples at these locations were analyzed for chemicals
of emerging concern, including perfluorinated compounds (PFCs) and synthetic musks, in addition to
contaminants, such as mercury, PCBs, polybrominated diphenyl ethers (PBDEs), and organochlorine
pesticides. Results for mercury and one PFC, perfluorooctane sulfonate (PFOS), are presented below;
complete analysis and reporting on the remaining fish tissue analytical results for organic compounds
will follow in a separate report. Additionally, comparisons between urban and non-urban waters will be
examined in the future.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Urban rivers: findings for mercury
Mercury is widely distributed in the environment through natural processes and through industrial
activities, such as fossil fuel (e.g., coal) combustion and hazardous waste incineration. These activities
release mercury into the atmosphere where it can be transported for long distances before being
deposited in water or on land. Once mercury is deposited in water, certain microorganisms can
change it into methylmercury, a highly toxic form that builds up in fish, shellfish, and animals that eat
fish. Fish and shellfish are the main sources of human exposure to methylmercury. The levels of
methylmercury in fish and shellfish depend on several factors, including what they eat, how long they
live, and how high they are in the food chain.
Mercury is widely found at detectable levels in fish tissue, and the amount of mercury measured in fish
tissue usually increases with fish age and size. Fish tissue samples from 44 of the 163 urban sites
assessed for mercury (or 26.9%) exceed the EPA fish-tissue-based human health water quality mercury
criterion of 300 parts per billion (ppb) (see Figure 26). This represents 2,970 miles of the 11,002
assessed urban river miles.
% of Urban Sites Exceeding
Hg Screening Value (300 ppb)
Figure 26. Mercury in fish tissue from urban sites.
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Chapter 4. Human Heaith Considerations in the Nation's Rivers and Streams
Urban rivers: findings for perfluorooctane sulfonate
PFCs are artificial chemicals that persist in the environment and have been used for decades to make
products that resist heat, oil, stains, grease, and water. They are used in many industrial applications
and are found in stain-resistant fabrics, nonstick cookware, and some types of food packaging. One
type of PFC, perfluorooctane sulfonate or PFOS, can accumulate to levels of concern in fish and
wildlife.
PFOS was the most commonly detected PFC in the fish tissue samples. Fish tissue samples from 19 of
the 162 urban sites assessed for PFCs contained PFOS above the one-meal-per-week Minnesota
advisory value of 40 ppb. This represents 11.6% of the 11,002 assessed urban river miles, or 1,276 river
miles (Figure 27). EPA is currently re-assessing the risk of PFOS to human health and expects to have a
peer-reviewed reference dose for PFOS in 2013.
% of Urban Sites Exceeding 1 Meal/Week
PFOS Screening Value (40 ppb)
infi
Figure 27. PFOS in fish tissue from urban sites.
Elevated mercury levels in fish are the leading cause offish consumption advisories in the U.S. Urban
river results showed that mercury concentrations occurred above the 300 ppb human health screening
value at about a quarter of the assessed urban river miles. These results demonstrate the pervasive
nature of mercury deposition in watersheds of the U.S. and mercury's subsequent accumulation in
fish. PFCs are recognized as contaminants of emerging concern because they are toxic, ubiquitous,
and persistent in the environment. Measured levels of PFOS in the fish tissue samples exceeded the
one-meal-per-week screening value of 40 ppb at nearly 12% of the assessed urban river miles. To
date, three states have issued fish consumption advisories based on elevated concentrations of PFOS
in fish.
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Chapter 5. Changes in Stream Condition
Among the long-term goals of the National Aquatic Resource Surveys is detecting trends in
both the condition of our aquatic resources and in the stressors that affect them. Policymakers
need this information in order to evaluate whether policy decisions have been effective or
whether a different approach is necessary to achieve important water quality goals. Trends can
be tracked either at the individual water body scale or at the larger population scale.
Typically, researchers and site managers are interested in changes at individual sites, while
many policymakers are more driven by changes and trends in groups or populations. Both types
of approaches are relevant to policy-making and complement each other in evaluating trends
and causes This is analogous to human health considerations: for example, you and your doctor
are interested in whether you are gaining or losing weight, but national health experts and the
health policy debate will be driven more by whether there is an increase or decrease in the
percentage of people in the U.S. who are gaining or losing weight.
To detect trends in the condition of rivers and streams, more years of data will be
necessary. However, comparison of the "wadeable streams" portion of the NRSA with the 2004
WSA provides a preliminary assessment of change in conditions in wadeable streams only,
between the two surveys. A change is not the same as a trend: it simply identifies the
difference between two points in time.
Some of the changes found in streams between 2004 and 2008-2009 are statistically
significant, and some are not. More data and additional analyses are necessary to fully
understand what these changes are telling us.
Findings for changes in stream condition
Comparing the WSA results to the NRSA's wadeable stream results provides an initial look
at changes for six of the survey indicators the Macroinvertebrate MMI, total phosphorus,
total nitrogen, in-stream fish habitat, riparian vegetative cover, and riparian disturbance. Some
indicators were not included in the change analysis because they had not been evaluated in the
WSA or because protocols were modified for the later study. The same evaluation thresholds
were used for both studies. It is important to remember that results from the WSA cannot be
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Chapter 5. Changes in Stream Condition
compared to results in other chapters of this report because the NRSA evaluates both rivers
and streams, not just streams.
The figures below show the percent of stream length in good condition for a given indicator
for the WSA in 2004 and the NRSA in 2008-2009. When the difference in the two estimates is
statistically significant, it is noted with a red star. A detailed statistical analysis of the difference
between surveys and the statistical confidence in that difference was performed and underlies
the presentation of the results below. It should be noted that the WSA condition class
percentages differ slightly from those in the WSA report to allow comparison between the
target populations of wadeable streams across the country. Minor adjustments were made to
the WSA percentages to be comparable to the NRSA design.
In Figure 28, results for the macroinvertebrate community indicator and nutrient indicators
(phosphorus and nitrogen) are shown for the nation and the three major climatic regions.
Nationally, the percent of stream length in good macroinvertebrate condition dropped from
27.4% in 2004 to 20.5% in 2008-2009. This difference is statistically significant for the nation
and may be driven by a 13.3% decline in streams in good condition in the Plains and Lowlands.
For the Eastern Highlands, the values also decline but the difference is not statistically
significant. There is no difference in macroinvertebrate condition for streams in the West.
A consistent, statistically significant drop is evident in the percentage of stream length in
good condition for phosphorus. Nationally, 52.8% of stream length was in good condition for
phosphorus in 2004, compared to 34.2% in 2008-2009. This pattern occurred in each of the
three major climatic regions, with the largest change (a decline of 22.5%) in the Plains and
Lowlands.
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Chapter 5. Changes in Stream Condition
c
.o
TJ
C
O
0
TJ
O
O
0
_E
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Chapter 5. Changes in Stream Condition
On the other hand, the percentage of stream length in good condition for nitrogen has risen
nationally, from 46.6% in 2004 to 55.4% in 2008-2009. Increases occurred in the Eastern
Highlands and the West, with each of those improvements being statistically significant. In the
Plains and Lowlands, there was a slight decline in the percent of stream length in good
condition but it is not statistically significant.
Figure 29 presents change results for three of the habitat indicators: in-stream fish habitat,
riparian vegetation cover, and riparian disturbance. The percent of stream length with good in-
stream fish habitat rose nationally and in each of the three regions. Nationally and in the West,
the percent of stream length in good condition for riparian vegetation cover also rose, with no
statistically significant changes in the Eastern Highlands or Plains and Lowlands. The percent of
stream length with low levels of riparian disturbance also showed statistically significant
increases nationally, in the Eastern Highlands, and in the Plains and Lowlands.
The fact that the differences noted above are statistically significant does not automatically
mean they are the result of human activities. Already, analysts have examined the relationships
between the change in nutrients and in natural phenomena such as precipitation, stream flow,
and drought, but they have found no reasons to explain the differences. Additional work is
underway to examine relationships to other signals of natural phenomena and to signals of
human activity. EPA and the U.S. Geological Survey (USGS) are also examining how long-term
trend data from USGS sites might help provide context for the changes seen between the WSA
and the NRSA. Trends in water quality will emerge over time as more surveys are completed,
and our understanding of the reasons for the trends will advance.
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Chapter 5. Changes in Stream Condition
In-stream Fish Habitat Riparian Vegetation Cover Riparian Disturbance
_i , 1 I L_J , ! ^^"-^ J-J , 1 ^^"-^
WSA(2004) NRSA(2009) WSA (2004) NRSA(2009) WSA (2004) NRSA (2009)
Figure 29. Change in stream fish habitat, riparian vegetation cover, and riparian disturbance between
2004 and 2008-2009, based on percent of stream length in good condition; red stars indicate
statistically significant change (EPA/NRSA). Note: WSA condition class percentages differ slightly from
those in the WSA report to allow comparison between the target populations of wadeable streams across the
country. Minor adjustments were made to the WSA percentages to be comparable to the NRSA design.
National Rivers and Streams Assessment, 2008 2009
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Chapter 6. Ecoregional Results
Introduction
Ecoregions are geographic areas that display similar environmental characteristics, such as
climate, vegetation, type of soil, and geology. EPA has defined ecoregions at various scales,
from a continental scale (Level I) to fine scales that divide the land into smaller ecosystem units
(Levels III or IV). This chapter will focus on NRSA results for the nine U.S. Level III ecoregions
aggregated for use in the National Aquatic Resource Surveys. These nine ecoregions, shown in
Figure 30, are:
> Northern Appalachians
> Southern Appalachians
> Coastal Plains
> Upper Midwest
> Temperate Plains
> Southern Plains
> Northern Plains
> Western Mountains
> Xeric
Ecoregions are designed to be used in environmental assessments, for setting water quality
and biological criteria, and to set management goals for pollution control. This is because it is
important to assess water bodies in their own ecological setting. For example, the rivers in the
mountainous, cold-to-temperate Northern Appalachians will have many similar characteristics;
they run through steep, rocky channels over glacial sediments, and are influenced by annual
precipitation totals of 35 to 60 inches. These rivers will differ significantly from those in the dry
plains, tablelands, and low mountains of the Xeric ecoregion, which drain erodible sedimentary
rock and are subject to flash floods in a climate where precipitation ranges from 2 to 40 inches
and average temperatures are much higher.
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Chapter 6. Ecoregional Results
NARS Ecoregions
Coastal Plain (CPl)
Northern Appalachians (NAP)
Northern Plains (NPL1
Southern Appalachians (SAP)
Southern Plains (SPL)
Temperate Plains (TPL)
Upper Midwest JUMW)
Western Mountains (WMT)
-=-Xeric(XER)
Figure 30. Ecoregional surveys for the NRSA (EPA/NRSA).
For purposes of the NRSA, least-disturbed reference sites in each ecoregion were used to
set benchmarks for good, fair, and poor condition in that ecoregion, and reflect the variability
within the ecoregion (see Chapter 2 and the NRSA Technical Report for more information on
this approach). This allows sites in one ecoregion to be compared to the reference waters in
that ecoregion. Because of this, it also allows results for one ecoregion to be compared to
results for another.
This chapter provides nationwide comparisons of key NRSA results for the nine ecological
regions. It then describes each ecoregion in more detail, providing background information and
describing NRSA results for the length of rivers and streams throughout the ecoregion. These
results should not be extrapolated to an individual state or water body within the ecoregion
because the study was not intended or designed to characterize conditions at these finer scales.
This information also cannot be compared to the ecoregional results presented in the earlier
WSA, which presented results only for streams. See Chapter 5 for the assessment of change for
wadeable streams only between the WSA and the NRSA. A number of states implemented
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Chapter 6. Ecoregional Results
randomized designs at the state scale to characterize the condition of rivers and streams
throughout their state, but these assessments are not described here.
Nationwide comparisons
The three most widespread stressors to rivers and streams phosphorus, nitrogen, and
riparian vegetative cover are depicted by ecoregion in the following maps, along with
summaries of macroinvertebrate condition and enterococci levels. These maps provide an
overview of how conditions vary across the nation, and in some cases illustrate distinct
ecoregional patterns.
Biological condition Macroinvertebrate Multimetric Index
The proportion of rivers and streams in poor biological condition based on the
Macroinvertebrate MMI ranges from 26% in the Western Mountains ecoregion to 71% in the
Coastal Plains ecoregion (Figure 31). A clear pattern is evident: the easternmost ecoregions
Biological Condition Macroinvertebrate MMI
Figure 31. Biological condition in rivers and streams based on the Macroinvertebrate Multimetric Index across
the nine ecoregions (EPA/NRSA). Percents may not add up to 100% due to rounding.
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Chapter 6. Ecoregional Results
(generally east of the Mississippi River) have a higher proportion of rivers and streams scoring
in poor biological condition than those in the western U.S. In the east, the percent of river and
stream miles in poor biological condition ranges from 55% to 71%. In the western ecoregions,
the percent in poor condition ranges from 26% to 43%.
Nutrients - total phosphorus and nitrogen
The nutrients phosphorus and nitrogen are the most widespread stressors of those
assessed in the NRSA. Figure 32 shows that in six of the nine ecoregions, phosphorus levels are
consistently rated poor (i.e., high) in about a third or more of river and stream miles. In two
more ecoregions the Northern Plains and the Northern Appalachians the proportion of
miles rated poor is much higher (84% and 71%, respectively). Only in the Southern Plains
ecoregion are half the river and stream miles rated good and only 23% rated poor for
phosphorus levels.
Total Phosphorus
Good
Fair
Poor
Northern Plains
Upper Midwest Northefn Appa|achians
14% A Southern Appalachians
Kilometers
0 125250 500 750 1,000
Figure 32. Total phosphorus levels in rivers and streams across the nine ecoregions (EPA/NRSA). Percents may
not add up to 100% due to rounding.
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Chapter 6. Ecoregional Results
The national picture shows less widespread impacts for nitrogen in many ecoregions (Figure
33). The ecoregions with the highest proportion of miles in poor condition for nitrogen are the
Northern Plains (60% rated poor), the Temperate Plains (58% rated poor), the Northern
Appalachians (42% rated poor), and the Xeric (36% rated poor). Five ecoregions (Coastal Plains,
Southern Plains, Southern Appalachians, Western Mountains, and Upper Midwest) have
between 7% and 21% of river and stream miles rated poor for nitrogen.
Total Nitrogen
Good
Fail-
Poor
Upper Midwest .1 u-
Northern Appalachians
Figure 33. Total nitrogen levels in rivers and streams across the nine ecoregions (EPA/NRSA). Percents may not
add up to 100% due to rounding.
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Chapter 6. Ecoregional Results
Riparian vegetative cover
One ecoregion the Northern Plains stands out as having the highest percentage of
river and stream miles in poor condition for riparian vegetative cover, at 59% (Figure 34). The
next highest is the Xeric ecoregion, at 37% of river and stream miles rated poor. In the
remaining seven ecoregions, between 13% and 29% of river and stream miles are rated poor for
riparian vegetative cover.
Riparian Vegetative Cover
Good
Fair
Poor
Western Mountains
Northern Plains
26%
Upper Midwest , . , ,
Northern Appalachians
29%
26% Southern Appalachians
rlk
49%
Kilometei
0 125 250 500 750 1,000
Figure 34. Riparian vegetative cover in rivers and streams across the nine ecoregions (EPA/NRSA). Percents may
not add up to 100% due to rounding.
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Chapter 6. Ecoregional Results
Enterococci
In six of the nine ecoregions, less than a tenth of river and stream miles exceed thresholds
protective of human health for enterococci bacteria (Figure 35). Of the three remaining
ecoregions, the Southern Appalachians has 14% of river and stream miles exceeding thresholds,
the Southern Plains has 13%, and the Central Plains has 11%.
Figure 35. Enterococci human health threshold exceedance in rivers and streams across the nine ecoregions
(EPA/NRSA). Percents may not add up to 100% due to rounding.
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Chapter 6. Ecoregional Results
Northern Appalachians
Setting
The Northern Appalachians ecoregion covers all of the New England states, most of New
York, the northern half of Pennsylvania, and northeastern Ohio. Included in the ecoregion are
New York's Adirondack and Catskill Mountains and Pennsylvania's Allegheny National Forest.
Major river systems include the St. Lawrence, Allegheny, Penobscot, Connecticut, and Hudson
rivers. The total river and stream length represented in the NRSA for the Northern Appalachians
ecoregion is 119,094 miles.
Forests in this ecoregion were extensively cleared in the 18th and 19th centuries. Current fish
stocks are lower than at the time of European contact, but the coastal rivers of the Northern
Appalachians ecoregion still have a wide variety of fish including shad, alewife, salmon, and
sturgeon that are born in fresh water, move to the sea for most of their lives, and then return
to fresh water to spawn. Major manufacturing, chemical, steel, and power production occur in
the large metropolitan areas around New York City, Connecticut, and Massachusetts. It is
common for treated wastewater effluent to account for much of the stream flow downstream
from major urban areas.
This ecoregion is generally hilly, with some intermixed plains and mountain ranges. River
channels in the glaciated uplands of the northern parts of the ecoregion are steep and rocky,
and flow over glacial sediments. The climate is cold to temperate, with mean annual
temperatures ranging from 39° to 48°F. Annual precipitation totals range from 35 to 60 inches.
The Northern Appalachians ecoregion covers some 139,424 square miles of land (4.6% of the
continental U.S.), with about 4,722 square miles of land under federal ownership. Based on
satellite images from the 2006 National Land Cover Dataset, the distribution of land cover in
this ecoregion is 61% forested, 15% planted/cultivated, and 9% developed; various other types
of land cover (such as wetlands or scrubland) constitute the remaining 15% of the ecoregion.
Summary of NRSA findings, Northern Appalachians
A total of 206 NRSA sites were sampled to characterize the condition of rivers and streams
in the Northern Appalachians ecoregion. Figure 36 shows an overview of the findings.
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Chapter 6. Ecoregional Results
Chemistry
Physical Habitat
Northern Appalachians (119,094 mi)
Biology
Macroinvertebrate MMI
-118.9%
21.9%
-)56.8%
Fish MMI
18.3% 29.6% 13 36.7% 1.6°/c
0 20
MMI
40
60
0/E
80
100 0
Riparian vegetative Cover
51%
40
60
80
100 0
No Data
Insuff Data
Not Assessed
Poor
Fair
Good
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
Percent of Length
I I Good I I Fair
20
Poor
40
60
80
100
NA
Figure 36. NRSA survey results for the Northern Appalachians ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add up
to 100% due to rounding.
Biological condition
The Macroinvertebrate MMI shows that 57% of the river and stream length in the Northern
Appalachians ecoregion is in poor condition, 22% is in fair condition, and 19% is in good
condition. The Macroinvertebrate 0/E Taxa Loss results show that 18% of river and stream
length has lost more than 50% of taxa expected to occur, and 30% has lost between 20% and
50%oftaxa.
The Periphyton MMI shows 53% percent of river and stream length in poor condition for
periphyton, while for fish, 28% of river and stream length in this ecoregion is determined to be
in poor condition.
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Chapter 6. Ecoregional Results
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Northern
Appalachians ecoregion are phosphorus, nitrogen, riparian vegetative cover, streambed
sediments, and riparian disturbance. Compared to least-disturbed conditions for this ecoregion:
> Phosphorus is at high levels in 71% of river and stream length, medium levels in 23%,
and low levels in 7%.
> Nitrogen is at high levels in 42% of river and stream length, medium levels in 9%, and
low levels in 49%.
> Riparian vegetative cover is rated poor in 29% of river and stream length, fair in 21%,
and good in 51%.
> Streambed sediments are rated poor in 18% of river and stream length, fair in 21%, and
good in 61%.
> Riparian disturbance is at high levels in 11% of river and stream length, medium levels in
50%, and low levels in 39%.
Southern Appalachians
Setting
The Southern Appalachians ecoregion stretches over 10 states, from northeastern Alabama
to central Pennsylvania, and includes the interior highlands of the Ozark Plateau and the
Ouachita Mountains in Arkansas, Missouri, and Oklahoma. The topography of this ecoregion is
mostly hills and low mountains, with some wide valleys and irregular plains. Its land area covers
about 321,900 square miles (10.7% of the continental U.S.), with about 42,210 square miles in
federal ownership. Many significant public lands, including the Great Smoky Mountains
National Park, the George Washington and Monongahela National Forests, and Shenandoah
National Park, are located within this ecoregion.
The Southern Appalachians ecoregion has some of the greatest aquatic animal diversity of
any area of North America, especially for species of amphibians, fishes, mollusks, aquatic
insects, and crayfishes. Some areas, such as the Great Smoky Mountains National Park,
continue to protect exceptional stands of old-growth forest riparian systems. Nevertheless, the
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Chapter 6. Ecoregional Results
effects of habitat fragmentation, urbanization, agriculture, channelization, diversion, mining,
and impoundments have altered many rivers and streams in this ecoregion.
Rivers in this ecoregion flow mostly over bedrock and other resistant rock types, with steep
channels and short meander lengths. A number of major rivers originate here, including the
Susquehanna, James, and Potomac, along with feeders into the Ohio and Mississippi River
systems such as the Greenbrier River in West Virginia. The total river and stream length
represented in the NRSA for the Southern Appalachians ecoregion is 315,242 miles. It is
considered temperate wet, with annual precipitation of about 40 to 80 inches and mean annual
temperature ranging from 55° to 65°F. Based on satellite images in the 2006 National Land
Cover Dataset, land cover in this ecoregion is 60% forested, 23% cultivated, and 9% developed;
the remaining 8% is in various other types of land cover.
Summary of NRSA findings, Southern Appalachians
A total of 316 NRSA sites were sampled to characterize the condition of rivers and streams
in the Southern Appalachians ecoregion. An overview of the findings is shown in Figure 37.
Biological condition
The Macro invertebrate MMI shows that 65% of the river and stream length in the Southern
Appalachians ecoregion is in poor condition; an additional 18% is in fair condition, and 17% is in
good condition. The Macroinvertebrate 0/E Taxa Loss results show that 17% of river and
stream length has lost more than 50% of taxa expected to occur, and 37% has lost between
20% and 50% of taxa.
The Periphyton MMI shows 68% percent of river and stream length in poor condition for
periphyton, while for fish, 37% of river and stream length is in poor condition.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Southern
Appalachians ecoregion are phosphorus, riparian vegetative cover, riparian disturbance,
nitrogen, and streambed sediments. Compared to least-disturbed conditions for this ecoregion:
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Chapter 6. Ecoregional Results
Physical Habitat
Streambed Sediments
58.3%
Total Phosphorus
Southern Appalachians (315,242 mi)
Biology
Macromvertebrate MMI
Total Nitrogen
71.2%
In-stream Fish Habitat
72.7%
Riparian Vegetative Cover
49.2%
Riparian Disturbance
30.8%
43.3%
Macromvertebrate O/E
37.1% 19.3% 26% 0.5°/,
40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
MMI O/E
ND ^H > 50% Taxa Loss
InsuffData I 1 20-50% Taxa Loss
NA LZ^M 0-20% Taxa Loss
Poor I I < 10% Taxa Loss
Fair i l NO Data
Good
Percent of Length
Good
Fair Poor
NA
Figure 37. NRSA survey results for the Southern Appalachian ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
> Phosphorus is at high levels in 40% of river and stream length, medium levels in 30%,
and low levels in 30%.
> Riparian vegetative cover is in poor condition in 26% of river and stream length, fair in
25%, and good in 49%.
> Riparian disturbance is at high levels in 26% of river and stream length, medium levels in
43%, and low levels in 31%.
> Nitrogen is at high levels in 17% of river and stream length, medium levels in 12%, and
low levels in 71%.
> Streambed sediments are rated poor in 13% of river and stream length, fair in 28%, and
good in 58%.
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Chapter 6. Ecoregional Results
Coastal Plains
Setting
The Coastal Plains ecoregion covers all of Florida, eastern Texas, and the Atlantic seaboard
from Florida to New Jersey. It includes the Mississippi Delta and Gulf Coast, and ranges north
along the Mississippi River to the Ohio River. The total land area of this ecoregion is about
395,000 square miles, or 13.2% of the continental U.S. Of this, 25,890 square miles, or 6.6%, is
in federal ownership. River systems within or intersecting the Coastal Plains ecoregion include
the Mississippi, Suwannee, Savannah, Potomac, Delaware, Susquehanna, James, Sabine, Brazos,
and Guadalupe.
River habitats in the Coastal Plains ecoregion have high species richness and the greatest
number of endemic species of aquatic organisms in North America. These include fish, aquatic
insects, and mollusks, as well as unique species such as paddlefish, American alligators, and
giant aquatic salamanders. However, it is estimated that about 18% of the aquatic species in
this ecoregion are threatened or endangered. Historically, this ecoregion had extensive
bottomlands that flooded for several months; these areas are now widely channelized and
confined by levees. Acid mine drainage, urban runoff, air pollution, sedimentation, and the
introduction of non-native species have affected riparian habitats and native aquatic fauna.
In general, rivers in the Coastal Plains meander broadly across flat plains created by river
deposition and form complex wetland topographies, with natural levees, back swamps, and
oxbow lakes. Typically, they drain densely vegetated watersheds; well-developed soils and
moderate rains and subsurface flows keep suspended sediment levels in the rivers relatively
low. An exception is the Mississippi River, which carries large sediment loads from dry lands in
the central and western portion of its drainage area. The total river and stream length
represented in the NRSA for the Coastal Plains ecoregion is 176,510 miles.
The topography of this ecoregion is mostly flat plains, barrier islands, many wetlands, and
about 50 important estuary systems that lie along its coastal margins. The climate is temperate
wet to subtropical, with average annual temperatures ranging from 50° to 80°F and annual
precipitation ranging from 30 to 79 inches. Based on satellite images in the 2006 National Land
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Chapter 6. Ecoregional Results
Cover Dataset, the distribution of land cover in this ecoregion is 28% forested, 26% cultivated,
21% wetlands, 9% developed, and the remainder in various other types of land cover.
Summary of NRSA findings, Coastal Plains
A total of 308 NRSA sites were sampled to characterize the condition of rivers and streams
in the Coastal Plains ecoregion. An overview of the findings is shown in Figure 38.
Biological condition
The Macro invertebrate MMI shows that 71% of river and stream length in the Coastal Plains
ecoregion is in poor condition compared to least-disturbed conditions, 17% is in fair condition,
and 12% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that 19% of
river and stream length has lost more than 50% of the taxa expected to occur, and 44% of river
Physical Habitat
Coastal Plains (176,510 mi)
Biology
Riparian vegetative Cover
69.3%
ND
InsuffData
NA
Poor
Fair
Good
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
20 40 60 80
Percent of Length
I I Good
40
60
80
100
Fair
Poor
NA
Figure 38. NRSA survey results for the Coastal Plains ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
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Chapter 6. Ecoregional Results
and stream length has lost between 20% and 50% of taxa.
The Fish MMI also shows a large percentage of river and stream length (52%) in poor
condition for fish, while for periphyton, 28% of river and stream length is in poor condition.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Coastal
Plains ecoregion are phosphorus, in-stream fish habitat, riparian vegetative cover, riparian
disturbance, and streambed sediments. Compared to least-disturbed conditions for this
ecoregion:
> Phosphorus is at high levels in 36% of river and stream length, medium levels in 31%,
and low levels in 33%.
> In-stream fish habitat is in poor condition in 24% of river and stream length, fair in 30%,
and good in 45% of river and stream length.
> Riparian vegetative cover is in poor condition in 18% of river and stream length, fair in
13%, and good in 69%.
> Riparian disturbance, or evidence of human influence in the riparian zone, is at high
levels in 13% of river and stream length, fair in 40%, and good in 47%.
> Streambed sediments are rated poor in 13% of river and stream length, fair in 34%, and
good in 51%.
Upper Midwest
Setting
The Upper Midwest ecoregion covers most of Minnesota's northern half and southeastern
area, two-thirds of Wisconsin, and almost all of Michigan, extending about 160,374 square
miles or 5.3% of the continental U.S. National and state forests and federal lands account for
about 25,000 square miles, or 15.5% of the area. The river systems in this ecoregion empty into
portions of the Great Lakes regional watershed and the upper Mississippi River watershed.
Major river systems include the upper Mississippi River in Minnesota and Wisconsin; the
Wisconsin, Chippewa, and St. Croix rivers in Wisconsin; and the Menominee and Escanaba
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Chapter 6. Ecoregional Results
rivers in Michigan. Other important water bodies include Lakes Superior, Michigan, Huron, and
Erie.
Virtually all of the virgin forest in this ecoregion was cleared in the 19th and early 20th
centuries, and rivers and streams were greatly affected by logging. The Great Lakes aquatic
systems are subject to increasing impact from invasive animal and plant species including the
zebra mussel, round goby, river ruffe, spiny water flea, and Eurasian watermilfoil. Major
manufacturing and chemical, steel, and power production occur in the large metropolitan areas
of the Upper Midwest ecoregion.
Streams in the Upper Midwest ecoregion typically drain relatively small catchments and
empty directly into the Great Lakes or Upper Mississippi River. These streams generally have
steep gradients, but their topography and soils tend to slow runoff and sustain flow throughout
the year. The total river and stream length represented in the NRSA for the Upper Midwest
ecoregion is 96,142 miles.
The glaciated terrain of this ecoregion typically consists of plains with some hills. Lakes,
rivers, and wetlands predominate in most areas. The climate is characterized by cold winters
and relatively short summers, with mean annual temperatures ranging from 34° to 54°F and
annual precipitation in the 20- to 47-inch range. Based on satellite images in the 2006 National
Land Cover Dataset, the distribution of land cover in this ecoregion is 36% forested, 27%
cultivated, 20% wetlands, and the remainder in various other types of land cover.
Summary of NRSA findings, Upper Midwest
A total of 161 NRSA sites were sampled to characterize the condition of rivers and streams
in the Upper Midwest ecoregion. An overview of the findings is shown in Figure 39.
Biological condition
The Macroinvertebrate MMI shows that 59% of river and stream length in the Upper
Midwest ecoregion is in poor condition compared to least-disturbed conditions, 23% is in fair
condition, and 18% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that
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Chapter 6. Ecoregional Results
Chemistry
Upper Midwest (96,142 mi)
Biology
o
0.1%
Macroinvertebrate MMI
I 17.7%
\ 22.7%
^B 1 59.4%
Fish MMI
11.4% 13.7%
62.9% 0.1%
Total Phosphorus
49.3%
Total Nitrogen
40.6%
38.6%
Salinity
98.7% hj
1.3%
Acidification
100%
Physical Habitat
Streambed Sediments
I 1 1 63.5%
In-stream Fish Habitat
) 80%
Riparian Vegetative Cover
I \ 1 62.6%
| 23.2%
Riparian Disturbance
I 1 1 60.3%
28.9%
20 40 60 80 100 0
20 40 60 80 100 0
MMI
CVE
Percent of Length
ND
InsuffData
NA
Poor
Fair
Good
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
Good
Fair
Poor
60 80 100
NA
Figure 39. NRSA survey results for the Upper Midwest ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
11% of river and stream length has lost more than 50% of the taxa expected to occur, and 12%
of river and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 41% of river and stream length in poor condition for fish; for
periphyton, only 15% of river and stream length is in poor condition.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Upper
Midwest ecoregion are phosphorus, riparian vegetative cover, and nitrogen. Compared to least-
disturbed conditions for this ecoregion:
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Chapter 6. Ecoregional Results
I Phosphorus is at high levels in 33% of river and stream length, medium levels in 18%,
and low levels in 50% of stream length.
> Riparian vegetative cover is rated in poor condition in 23% of stream length, fair in 14%,
and good in 63% of river and stream length.
> Nitrogen is at high levels in 21% of river and stream length, medium levels in 39%, and
low levels in 41%.
> Streambed sediments and riparian disturbance are both rated poor in 11% of river and
stream length.
Temperate Plains
Setting
The Temperate Plains ecoregion includes Iowa; the eastern Dakotas; western Minnesota;
portions of Missouri, Kansas, and Nebraska; and the flat lands of western Ohio, central Indiana,
Illinois, and southeastern Wisconsin. This ecoregion covers about 342,200 square miles, or
11.4%, of the continental U.S., with approximately 7,900 square miles under federal ownership.
Many of the rivers in this ecoregion drain into the Upper Mississippi Ohio, and Great Lakes
watersheds.
Much of this ecoregion is now primarily arable cultivated land, including field crops such as
corn, wheat, and alfalfa as well as hog and cattle production. Crops and grazing have reduced
natural riparian vegetative cover, increased sediment yield, and introduced pesticides and
herbicides. Rivers have many species offish, including minnows, darters, killifishes, catfishes,
suckers, sunfishes, and black bass.
Rivers and streams in the tall grass prairie start from prairie potholes and springs and may
be ephemeral (flowing for a short time after snowmelt or rainfall). Rivers carry large volumes of
fine sediments and tend to be turbid, wide, and shallow. The total river and stream length
represented in the NRSA for the Temperate Plains ecoregion is 227,017 miles.
The terrain of this ecoregion consists of smooth plains and many small lakes and wetlands.
The climate is temperate, with cold winters, hot and humid summers, and mean temperatures
ranging from 36° to 55°F. Annual precipitation ranges from 16 to 43 inches. Based on satellite
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Chapter 6. Ecoregional Results
images in the 2006 National Land Cover Dataset, the distribution of land cover in this ecoregion
is 69% cultivated, 10% forested, 9% developed, and the remainder in other types of land cover.
Summary of NRSA findings, Temperate Plains
A total of 193 NRSA sites were sampled to characterize the condition of rivers and streams
in the Temperate Plains ecoregion. An overview of the findings is shown in Figure 40.
Biological condition
The Macro invertebrate MMI shows that 55% of river and stream length in the Temperate
Plains ecoregion is in poor condition compared to least-disturbed conditions, 30% is in fair
condition, and 15% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that
Temperate Plains (227,017 mi)
Biology
23% 20.6% 12.3% 43.6% 0.5%
Chemistry
Total Phosphorus
45.7%
Total Nitrogen
57.5%
Salinity
91.8% HH
0.6%
Acidification
99.8%
Physical Habitat
40
60
80
100 0
20
40
60
80
MMI O/E
I 1 ND
InsuffData
NA
Poor
Fair
Good
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
Percent of Length
I I Good
100 0
Fair
Riparian Vegetative Cover
50.4%
Riparian Disturbance
28.5%
55.6%
Poor
NA
Figure 40. NRSA survey results for the Temperate Plains ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
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23% of river and stream length has lost more than 50% of the taxa expected to occur, and 21%
of river and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 35% of river and stream length in poor condition for fish; for
periphyton, 29% of river and stream length is in poor condition.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Temperate
Plains ecoregion are nitrogen, phosphorus, riparian vegetative cover, riparian disturbance, and
streambed sediments. Compared to least-disturbed conditions for this ecoregion:
> Nitrogen is at high levels in 58% of river and stream length, medium levels in 13%, and
low levels in 29%.
> Phosphorus is at high levels in 31% of river and stream length, medium levels in 24%,
and low levels in 46%.
> Riparian vegetative cover is rated as poor in 24% of river and stream length, fair in 26%,
and good in 50%.
> Riparian disturbance is at high levels in 16% of river and stream length, medium levels in
56%, and low levels in 29%.
> Streambed sediments are rated poor in 14% of river and stream length, fair in 36%, and
good in 50%.
Southern Plains
Setting
The Southern Plains ecoregion covers about 405,000 square miles (13.5% of the continental
U.S.) and includes central and northern Texas; most of western Kansas and Oklahoma; and
portions of Nebraska, Colorado, and New Mexico. The Arkansas, Platte, White, Red, and Rio
Grande rivers flow through this ecoregion, and most of the Ogallala aquifer (one of the world's
largest water table aquifers which supplies irrigation and drinking water to eight states) lies
underneath it. Federal land ownership in this ecoregion totals about 11,980 square miles, or
about 3% of the total.
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The terrain is a mix of smooth and irregular plains interspersed with tablelands and low
hills. The Great Prairie grasslands, which once covered much of the Southern Plains ecoregion,
are the most altered and endangered large ecosystem in the U.S. About 90% of the original tall
grass prairie was replaced by other vegetation; agriculture and livestock grazing and production
are prevalent. Agriculture is, in fact, an important economic activity in this ecoregion, and
includes sorghum, wheat, corn, sunflower, bean, and cotton production. Livestock production
and processing is also prevalent. This ecoregion also contains a sizable portion of U.S.
petroleum and natural gas production in Oklahoma, Kansas, and Texas. The total river and
stream length represented in the NRSA for the Southern Plains ecoregion is 36,594 miles.
Based on satellite images in the 2006 National Land Cover Dataset, the land in this
ecoregion is 62% grassland/shrub, 27% cultivated, 5% forested, and the remainder in other
types of land cover. The climate in this ecoregion is dry temperate, with mean annual
temperatures ranging from 45° to 79°F. Annual precipitation is between 10 and 30 inches.
Summary of NRSA findings, Southern Plains
A total of 166 NRSA sites were sampled to characterize the condition of rivers and streams
in the Southern Plains ecoregion. An overview of the findings is shown in Figure 41.
Biological condition
The Macro invertebrate MMI shows that 42% of river and stream length in the Southern
Plains ecoregion is in poor condition compared to least-disturbed conditions, 36% is in fair
condition, and 21% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that
23% of river and stream length has lost more than 50% of the taxa expected to occur, and 28%
of river and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 31% of river and stream length in poor condition for fish. Forty-three
percent of river and stream length is in poor condition for periphyton.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Southern
Plains ecoregion are riparian disturbance, streambed sediments, phosphorus, riparian
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Chapter 6. Ecoregional Results
Chemistry
Southern Plains (36,594 mi)
Biology
Macroinvertebrate MMI
I 21.4%
\ 35.6%
Fish MMI
Total Phosphorus
49.8%
Total Nitrogen
75%
Physical Habitat
80 100 0
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
20 40 60 80 100 0
Percent of Length
i i Good I I Fair
Riparian Vegetative Cover
69.4%
40 60 80 100
Poor
NA
Figure 41. NRSA survey results for the Southern Plains ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not
add up to 100% due to rounding.
vegetative cover, and in-stream fish habitat. Compared to least-disturbed conditions for this
ecoregion:
> Riparian disturbance is rated at high levels in 30% of river and stream length, medium
levels in 59%, and good levels in only 11% of river and stream length.
> Streambed sediments are rated poor in 26% of river and stream length, fair in 34%, and
good in 39%.
> Phosphorus is at high levels in 23% of river and stream length, medium levels in 28%,
and low levels in 50%.
> Riparian vegetative cover is rated in poor condition in 18% of river and stream length,
fair in 13%, and good in 70%.
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I In-stream habitat is rated poor in 16% of river and stream length, fair in 25%, and good
in 59%.
> Salinity, though not a widespread stressor nationally or in most other ecoregions, is
rated poor in 15% of river and stream length in the Southern Plains ecoregion.
Northern Plains
Setting
The Northern Plains ecoregion covers approximately 205,084 square miles, or 6.8% of the
continental U.S. It includes the western Dakotas, Montana east of the Rocky Mountains,
northeast Wyoming, and a small section of northern Nebraska. This ecoregion is the heart of
the Missouri River system and is almost exclusively within the Missouri River's watershed.
Federal lands account for 52,660 square miles, or nearly 26% of the total area.
Human economic activity in this ecoregion is primarily agriculture, including cattle and
sheep grazing and cropland. Coal mining occurs in the North Dakota, Montana, and Wyoming
portions of the ecoregion, and petroleum and natural gas production are growing.
This ecoregion's terrain is irregular plains interspersed with tablelands and low hills. The
Great Prairie grasslands were once an important feature of this ecoregion, but have largely
been replaced by other vegetation or land uses, particularly cropland. The total river and
stream length represented in the NRSA for the Northern Plains ecoregion is 27,227 miles.
Based on satellite images in the 2006 National Land Cover Dataset, the land in this
ecoregion is 68% grassland/shrub, 23% cultivated, 3% forested, and the remainder in other
types of land cover. The climate in this ecoregion is dry and characterized by short, hot
summers and long, cold winters. Temperatures average 36° to 46°F, and annual precipitation
totals range from 10 to 25 inches. High winds are an important climatic factor in this ecoregion,
which is also subject to periodic intense droughts and frosts.
Summary of NRSA findings, Northern Plains
A total of 175 NRSA sites were sampled to characterize the condition of rivers and streams
in the Northern Plains ecoregion. An overview of the findings is shown in Figure 42.
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Physical Habitat
Northern Plains (27,227 mi)
Biology
Riparian vegetative Cover
, 25.9%
h-)-H 15.
ND ^B > 50% Taxa Loss
InsuffData | | 20-50% Taxa Loss
| | 10-20% Taxa Loss
I | < 10% Taxa Loss
| | No Data
20 40 60 80
Percent of Length
I Good [
Fair
20
Poor
40
60
80 100
NA
NA
Poor
Fair
Good
Figure 42. NRSA survey results for the Northern Plains ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
Biological condition
The Macroinvertebrate MMI shows that 33% of river and stream length in the Northern
Plains ecoregion is in poor condition compared to least-disturbed conditions, 27% is in fair
condition, and 40% is in good condition. The Macroinvertebrate O/E Taxa Loss results show that
9% of river and stream length has lost more than 50% of the taxa expected to occur, and 18% of
river and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 29% of river and stream length in poor condition for fish; for
periphyton, 30% of river and stream length is in poor condition.
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Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Northern
Plains ecoregion are phosphorus, riparian disturbance, nitrogen, riparian vegetative cover, and
salinity. Compared to least-disturbed conditions for this ecoregion:
> Phosphorus is at high levels in 84% of river and stream length, medium levels in 4%, and
low levels in 13%.
> Riparian disturbance is rated high in 60% of river and stream length, medium in 36%,
and low in 3%.
> Nitrogen is at high levels in 60% of river and stream length, medium levels in 17%, and
low levels in 23%.
> Riparian vegetative cover is rated poor in 59% of river and stream length, fair in 15%,
and good in 26%.
> Salinity is a widespread stressor in the Northern Plains and is found at high levels in 51%
of river and stream length, at medium levels in 23%, and at low levels in 26% of river
and stream length.
Western Mountains
Setting
The Western Mountain ecoregion includes the Cascade, Sierra Nevada, and Pacific Coast
ranges in the coastal states; the Gila Mountains in the southwestern states; and the Bitterroot
and Rocky Mountains in the northern and central mountain states. The headwaters and upper
reaches of the Columbia, Sacramento, Missouri, and Colorado River systems all occur in this
ecoregion. This ecoregion covers about 397,832 square miles, with about 297,900 square miles,
or 74.8%, classified as federal land.
The terrain of the Western Mountains ecoregion is characterized by extensive mountains
and plateaus separated by wide valleys and lowlands. Coastal mountains are transected by
many fjords and glacial valleys, are bordered by coastal plains, and include important estuaries
along the margins of the ocean. Soils are mainly nutrient-poor forest soils. Rivers drain dense
forested catchments and contain large amounts of woody debris that provide habitat diversity
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and stability. Rivers reaching the Pacific Ocean historically had large runs of salmon and trout,
although many of these populations have been reduced by the effects of dams, flow regulation,
overfishing, and introduced species. Smaller rivers generally start as steep mountain streams
with staircase-like channels, steps, and plunge pools, with riffles and pools appearing as slope
decreases. Upper river reaches experience debris flows and landslides when shallow soils
become saturated by rainfall or snowmelt. The total river and stream length represented in the
NRSA for the Western Mountains ecoregion is 150,975 miles.
Based on satellite images in the 2006 National Land Cover Dataset, the land in this
ecoregion is 55% forested, 36% shrub/scrub and grassland, and the remainder in other types of
land cover. The climate is sub-arid to arid and mild in southern lower valleys, and humid and
cold at higher elevations. The wettest climates of North America occur in the marine coastal
rain forests of this ecoregion. Mean annual temperatures range from 32° to 55°F, and annual
precipitation ranges from 16 to 240 inches.
Summary of NRSA findings, Western Mountains
A total of 210 NRSA sites were sampled to characterize the condition of rivers and streams
in the Western Mountains ecoregion. An overview of the findings is shown in Figure 43.
Biological condition
The Macroinvertebrate MMI shows that 26% of river and stream length in the Western
Mountains ecoregion is in poor condition compared to least-disturbed conditions, 31% is in fair
condition, and 42% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that
6% of river and stream length has lost more than 50% of the taxa expected to occur, and 18% of
river and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 21% of river and stream length in poor condition for fish, while for
periphyton, 36% of river and stream length is in poor condition.
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Chemistry
Western Mountains (150,975 mi)
Biology
Total Phosphorus
38.6%
Total Nitrogen
66.9%
Salinity
97.6% ||
}\ 2.4%
Acid if
cation
100%
Physical Habitat
40 60 80 100 0 20 40 60 80 100 0
Riparian Vegetative Cover
69.3%
MMI O/E
ND ^
InsuffData
NA
Poor
Fair
Good
Percent of Length
> 50% Taxa Loss
I 20-50% Taxa Loss
10-20% Taxa Loss
I < 10% Taxa Loss
I No Data
Good
Fair
Poor
NA
Figure 43. NRSA survey results for the Western Mountains ecoregion (EPA/NRSA). Bars show the
percentage of river and stream length within a condition class for a given indicator. Percents may not add
up to 100% due to rounding.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Western
Mountains ecoregion are phosphorus, nitrogen, riparian disturbance, riparian vegetative cover
and streambed sediments. Compared to least-disturbed conditions for this ecoregion:
> Phosphorus is at high levels in 37% of river and stream length, medium levels in 25%,
and low levels in 39%.
> Nitrogen is at high levels in 18% of river and stream length, medium levels in 15%, and
low levels in 67%.
> Riparian disturbance is rated high in 18% of river and stream length, medium in 50%,
and low in 32%.
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I Riparian vegetative cover is rated poor in 13% of river and stream length, fair in 18%,
and good in 69%.
> Similarly, streambed sediments are rated poor in 13% of river and stream length, fair in
26%, and good in 62%.
Xeric
Setting
The Xeric ecoregion covers the largest area of all NRSA aggregate ecoregions and includes
the most total land under federal ownership. It covers portions of 11 western states and all of
Nevada, fora total of about 636,583 square miles, or 21% of the continental U.S. Around
453,000 square miles, or 71% of the land, is classified as federal lands, including the Grand
Canyon National Park, Big Bend National Park, and the Hanford Nuclear Reservation.
The terrain of the Xeric ecoregion is composed of a mix of physiographic features, including
plains with hills and low mountains, high-relief tablelands, piedmont, high mountains, and
intermountain basins and valleys. The ecoregion includes the flat to rolling topography of the
Columbia/Snake River Plateau; the Great Basin; Death Valley; and the canyons, cliffs, buttes,
and mesas of the Colorado Plateau. Its relatively limited surface water supply contributes to the
Upper and Lower Colorado, Great Basin, California, Rio Grande, and Pacific Northwest regional
watersheds. Large rivers flow all year, are supplied by snowmelt, and peak in early summer.
Small rivers are mostly ephemeral. Rivers are often subject to rapid change due to flash floods
and debris flows. In southern areas of the ecoregion, internal drainages often end in saline
lakes or desert basins without reaching the ocean (e.g., Utah's Great Salt Lake).
Rivers in this ecoregion create a riparian habitat oasis for plants and animals. Many fish are
endemic and have evolved to cope with warm, turbid waters. Many are threatened or
endangered due to flow regulations from dams, water withdrawals, and introduced non-native
species. The total river and stream length represented in the NRSA for the Xeric ecoregion is
44,974 miles.
Based on satellite images in the 2006 National Land Cover Dataset, the land in this
ecoregion is 77% shrub/scrub and grassland, 8% cultivated, 7% forested, and the remainder in
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Chapter 6. Ecoregional Results
various types of land cover. The climate in this ecoregion varies widely from warm and dry to
temperate, with mean annual temperatures ranging from 32° to 75°F and annual precipitation
in the 2- to 40-inch range.
Summary of NRSA findings
A total of 189 NRSA sites were sampled to characterize the condition of rivers and streams
in the Xeric ecoregion. An overview of the findings is shown in Figure 44.
Biological condition
The Macro invertebrate MMI shows that 43% of river and stream length in the Xeric
ecoregion is in poor condition compared to least-disturbed conditions, 15% is in fair condition,
Chemistry
Xeric Region (44,974 mi)
Biology
Total Phosphorus
35.5%
'otaI Nitrogen
III 22.6%
12.1%
Acidification
100%
Physical Habitat
MMI
40
ND
InsuffData
NA
Poor
Fair
Good
60
O/E
80
100 0
20
40
60
80
Percent of Length
> 50% Taxa Loss
20-50% Taxa Loss
10-20% Taxa Loss
< 10% Taxa Loss
No Data
Good
100 0
Fair
In-stream Fish Habitat
HH 1 66.4%
Riparian Vegetative Cover
44%
40
Poor
60
NA
80
100
Figure 44. NRSA survey results for the Xeric ecoregions (EPA/NRSA). Bars show the percentage of river
and stream length within a condition class for a given indicator. Percents may not add up to 100% due to
rounding.
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and 41% is in good condition. The Macroinvertebrate 0/E Taxa Loss results show that 13% of
river and stream length has lost more than 50% of the taxa expected to occur, and 31% of river
and stream length has lost between 20% and 50% of taxa.
The Fish MMI shows 40% of river and stream length in poor condition for fish; for
periphyton, 50% of river and stream length is in poor condition.
Indicators of stress
Of the indicators of stress measured for the NRSA, the most widespread in the Xeric
ecoregion are riparian disturbance, riparian vegetative cover, phosphorus, nitrogen, and
streambed sediments. Compared to least-disturbed conditions for this ecoregion:
> Riparian disturbance is rated high in 46% of river and stream length, medium in 36%,
and low in 18%.
> Riparian vegetative cover is in poor condition in 37% of river and stream length, fair
condition in 19%, and good condition in 44%.
> Phosphorus is at high levels in 38% of river and stream length, medium levels in 26%,
and low levels in 36%.
> Nitrogen is at high levels in 36% of river and stream length, medium levels in 24%, and
low levels in 40%.
> Streambed sediments are rated poor in 34% of river and stream length, fair in 31%, and
good in 34%.
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This first National Rivers and Streams Assessment was an unprecedented sampling and
analytical effort by EPA and its state and tribal partners. Over two summers, 85 field crews
sampled nearly 2,000 sites along the nation's wide-ranging rivers and streams. Twenty-two
separate field training sessions were held to prepare for this survey. The efforts of the field
crews yielded over 25,000 samples shipped to laboratories across the country. For example,
over the course of the survey, 3,300 benthic macroinvertebrate samples (each sample with
hundreds of individual preserved macroinvertebrates) were shipped to eight laboratories for
sorting, identification, and analysis. Seventeen different indicators were sampled or evaluated
at the NRSA sites. Ten million bits of data were collected in field and analyzed in laboratories.
These data from the NRSA are available at www.epa.gov/aquaticsurveys.
Overall, the NRSA finds that biological communities in our rivers and streams are being
heavily affected and degraded across the country. More than half of the nation's river and
stream length is in poor condition, based on an index that combines different measures of the
condition of aquatic benthic macroinvertebrates. The eastern and mid-western ecoregions tend
to have the most waters in poor biological condition, with the percentage of rivers and streams
rated poor ranging from 55% to 71%. In the west (including the Northern and Southern Plains
ecoregions), the percentage of rivers and streams in poor biological condition ranges from 26%
to 42%.
Of the four chemical stressors assessed, phosphorus and nitrogen are the most widespread.
Biological communities are 50% more likely to be in poor condition when phosphorus levels are
high and 40% more likely to be in poor condition when nitrogen levels are high. Phosphorus is
the most widespread stressor in six of the nine ecoregions, and nitrogen is the most widespread
in one ecoregion. Analysis of the NRSA data suggest that if phosphorus levels were reduced in
areas where levels are currently high, we might see 17% of the nation's river and stream length
improve to good conditions for macroinvertebrates.
Of the four physical habitat stressors assessed in the NRSA, poor riparian vegetative cover
and high levels of riparian disturbance are reported in 24% and 20% of the nation's river and
stream length respectively, and are the most widespread. Riparian disturbance is the most
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widespread stressor in two of the nine ecoregions. However, excess streambed sediments have
a somewhat greater impact on biological condition. Poor biological condition is 60% more likely
in rivers and streams with excessive levels of streambed sediments. Nearly 9% of river and
stream length in poor biological condition might improve to good conditions for
macroinvertebrates if excess levels of streambed sediments were reduced or eliminated.
The NRSA also includes two indicators that provide insight into potential risks to human
health. It finds that in 9% of the nation's river and stream length, levels of enterococci bacteria
exceed threshold levels for protecting human health. Additionally, the NRSA is able to report
that over 13,000 miles of rivers have mercury levels in fish tissue that exceed human health
screening values.
As we continue to implement these surveys over time, an important element of the NRSA is
the ability to track changes in the condition of our rivers and streams. This report provides a
first glimpse of that capability by examining the differences between stream conditions as
reported in 2004 and wadeable systems assessed as part of the NRSA. Several NRSA indicators
show statistically significant change compared to the 2004 WSA. An increase in stream length in
good condition is evident for nitrogen, in-stream fish habitat, riparian disturbance, and riparian
vegetation; however, there is also a decrease in stream length in good condition for
phosphorus and overall biological condition as measured by the macroinvertebrate index.
These findings of change apply only to streams and are only identifying differences between
two points in time; they should not be interpreted as trends in water quality conditions.
Reasons for the changes have not been determined although work continues in evaluating
possible human or natural explanations. Future assessments of the nation's rivers and streams
will be able to provide more robust trend assessments as additional years of data become
available and as our understanding of the relationship between human activity, natural
phenomena, and environmental change mature.
The survey's finding that more than half of river and stream length is in poor biological
condition and that excess nutrients and poor habitat are widespread contributors to poor
condition supports continued management attention to these problems at the national,
regional, state, and watershed scales. Management actions should be focused not only on
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improving those areas where biological conditions are poor, nutrient levels are high, and
habitat conditions are already degraded, but on protecting those areas that are still in good
condition.
Moving the science forward
Many of the contributions of the NRSA go beyond the findings discussed in this report.
Scientists developed new methods of sampling and assessing important water indicators such
as streambed sediments; data were collected on leading-edge indicators that will be analyzed
and reported separately; and state and tribal partners gained and shared new expertise in
state-of-the-art field monitoring methods and probability-based surveys.
EPA scientists and collaborators are continuing to move the science forward to assess the
core indicators that are part of the NRSA. Many of these efforts are focused on new ways to
assess the benthic macroinvertebrate community using a method similar to the one used for
the fish assemblage and periphyton assemblage indicators. This advanced approach uses a
modeling technique called random forest modeling to improve the establishment of
reference condition and our ability to assess the condition of biological communities. NRSA
scientists will publish supplemental benthic analysis using the random forest model and set the
stage for incorporating this procedure into the next NRSA report.
NRSA scientists are also working toward developing assessment and reporting methods that
will more fully integrate the three biological indicators into one to evaluate the overall
condition of rivers and streams. Transferring NRSA methods and technology to state and tribal
programs is another key aspect of moving the science forward.
As additional data continue to come back from laboratories, they will be analyzed and
published as NRSA supplemental reports. For example, many analytes that were included in the
fish tissue analysis are still waiting for final laboratory analysis. These include pesticide data,
PCBs, and chemicals of emerging concern such as Pharmaceuticals. In urban rivers, crews also
collected water samples to look at the presence and amount of chemicals of emerging concern.
EPA included several leading-edge indicators as part of the NRSA. These indicators were
selected to address emerging issues and developments in aquatic sciences and were included
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to support innovative research within the EPA. For example, the EPA Office of Research and
Development led an effort to study microbial sediment enzyme activity (or sediment enzymes),
an indicator that focuses on nutrient concentration within the streambed sediment. The work
to collect and analyze sediment enzymes is helping EPA and our partners better understand
nutrient limiting factors within the stream or river channel that affect the biological community.
The result may prove to be a sensitive indicator that can help us implement the most effective
management action to address nutrient pollution. A number of peer-reviewed journal articles
focus on the technical aspects of the analysis and assessment of this innovative indicator.
Next steps
As this report was being written, planning was already underway for the 2013-2014
National Rivers and Streams Assessment. EPA and its state and tribal partners have taken stock
of the lessons learned from the 2008-2009 survey as well as from other National Aquatic
Resource Surveys; they have met to discuss possible changes in indicators, methods, reference
sites, logistics, and analytical approaches; sites for the 2013-2014 sampling seasons have been
selected; and manuals for field and laboratory methods and quality assurance are being
updated and prepared. Supplemental reports based on these 2008-2009 findings will be issued
as assessments are completed. These supplemental reports will be made available on the
National Aquatic Resource Surveys main website at www.epa.gov/aquaticsurveys.
EPA, states, tribes, and other federal partners expect to continue to produce national water
quality assessments on a regular cycle under the National Aquatic Resource Surveys program. A
new national coastal assessment report will be released in 2013 based on field sampling that
took place in 2010. A first-ever national wetlands condition assessment, based on field sampling
in 2011, is also scheduled for 2013. A second national lakes assessment is planned for 2014
based on sampling during the summer of 2012.
As these national assessments continue, many states are developing and conducting their
own state-scale probability surveys of their rivers and streams, lakes, and coastal waters. EPA
will continue to explore ways to best support states as they sample, analyze, and report on
their waters using these surveys. For example, EPA is working to build and refine tools states
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Chapter 7. Summary and Next Steps
can use to assess survey data at different scales and is exploring options for providing direct
technical support. As a first step, EPA will make available the statistical codes that were used to
develop the MMIs and thresholds for assessment. EPA is also piloting in-person training on the
statistical tools and methods that were used in the National Lakes Assessment. Modifications
and refinements will be made to this pilot effort to train states and tribes for the NRSA and
other NARS programs.
This survey would not have been possible without the assistance and collaboration of
hundreds of scientists working for state, federal, and tribal agencies and universities across the
country. These scientists helped plan and design the survey, select sites and indicators, develop
and improve monitoring methods, train crew members, conduct sampling, track samples,
screen and analyze results, and review and write up the findings. Working together on future
surveys, and on state-scale surveys of similar design, EPA and its partners will continue
developing a high quality baseline of information on rivers and streams that can be used to
evaluate our progress in protecting and restoring them.
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California uses the NARS approach to enhance monitoring capacity
Introduction
One of the strengths of the NARS program has
been its ability to transfer significant technical
advances in monitoring approaches and
techniques to states and tribes. Partnerships with
states and tribes were designed to help build
local capacity to take advantage of the new tools
that NARS was developing.
Over the last 12 years, California has embraced
this technical and partnership approach. First
participating in the EPA Environmental
Monitoring and Assessment Program (EMAP)
Western pilot to monitor streams and rivers,
California used what it learned to produce a
thriving program that is transforming the way
water quality monitoring is conducted and data
are evaluated throughout the state. Since 2000,
California has leveraged about 250 EMAP/NRSA
sites into a probability dataset of over 1,200 sites
(Figure 45). The list of data applications and opportunities for partnerships keeps growing every year.
Regional assessments and land use assessments
The high density of sites in California supports the development of regional assessments and
analyses (e.g., of stressor extent and risk) that are more relevant to the scale at which policy and
management decisions are made (Figure 46). California also added the ability to produce summaries
for major land cover classes such as forested, agricultural, or urban land (Figure 47). This was the first
attempt to use a probability survey to produce land-use-specific assessments. Knowing the
probability-derived distribution of stressors and indicators in urban, agricultural, and forested
landscapes gives managers context for interpreting the results of monitoring done in these types of
landscapes.
O Good
O Degraded
Very Degraded
Figure 45. Map of about 1,200 probability sites in
California sampled since 2000 using compatible
EMAP-style survey designs.
National Rivers and Streams Assessment, 2008-2009
February 2013
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Chapter 7. Summary and Next Steps
PSA Boundaries
| | North Coast
| | Chapparal
H Sierra
| | Central Valiey
| | South Coast
I | Other
Figure 46. Biological condition of perennial streams in the six major
ecological regions of California. (Green = good biological condition,
yellow = altered biological condition, and red = very altered biological
condition.)
PHOSPHORUS
NITROGEN
CHLORIDE
CONDUCTANCE
TURBIDITY
SUSPENDED SOLIDS
FINES+SANDS
BED STABILITY
INSTREAM HABITAT
RIPARIAN VEG
RIPARIAN DISTURB
0 20 40 60 80
0 20 40 60 80
0 20 40 60 80 100
Agricultural Forested Urban
Figure 47. Percentage of California stream length that exceeds severe (red)
and moderate (yellow) threshold values for various chemical and physical
habitat stressor variables in streams associated with each of three major
land cover types.
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Chapter 7. Summary and Next Steps
Beyond condition assessments
Exploring stressor-condition relationships
CA measures a large suite of water chemistry and in-stream and riparian habitat parameters in
addition to ecological condition indicators such as benthic invertebrates and algae. Site-specific
information is supplemented with over a hundred layers of CIS data that look across the site,
watershed and region. This provides a dataset that can be used to explore stressor-condition
relationships for a wide variety of objectives (Figure 48). The ability to produce objective descriptions
of stressor extent and relationships between stressors and biological condition holds even greater
potential to influence CA's resource management programs. Better understanding of these
relationships is leading to significant improvements in the state's ability to prioritize limited
resources and to have more meaningful discussions about issues of concern with the public and with
other agencies (Figure 49).
/o Sands and fines
Total Phosphorus
Channel alteration
Riparian disturbance -
Chloride
Riparian vegetation
Total Nitrogen
Cadmium -
Embeddedness
Invasive species
Copper
Selenium
Aquatic toxicity -
A |
1 9 i
i 1
M>-H
K::H
Hh
H3-H
a
H*-H
*;
K>H
lOH Physical habitat
© Nutrients
Q O Water chemistry
Other stressor
1234567!
Relative Risk
reference distribution
probability distribution
management
thresholds
Figure 49. The combination of probability and
reference distributions provides objective context
for interpreting targeted monitoring data.
Figure 48. Relative risk of biological
impairment associated with a series of
habitat and chemistry variables in southern
California streams.
targeted
distribution
12345
Riparian Disturbance
National Rivers and Streams Assessment, 2008-2009
February 2013
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Chapter 7. Summary and Next Steps
r)rt for biocriteria development
-rnia's extensive probability datasets have given the state a solid foundation to move toward
using ecological indicators for regulatory purposes, such as biocriteria development and refining
reference condition. Probability data have also played an important role in the development of
the technical elements of California's biocriteria policy, which is currently in progress.
Fostering inter-agency coiiaboration
California's statewide probability survey, the Perennial Streams Assessment, serves as a highly
effective tool for encouraging collaboration with regional monitoring programs and federal
agencies. For example, two successful monitoring partnerships in urban areas (southern coastal
California and the San Francisco Bay Area) worked with the Assessment to create monitoring
programs that were compatible with the Assessment's design and that allowed them to
coordinate efforts and effectively use data across regional groups. Partnerships with federal
agencies have the potential for similar benefits in rural areas.
Partnerships like those in California enable programs to do more with limited monitoring
resources and provide feedback that improves the monitoring program. They help connect
partners' management needs to the right data. California is using this approach to accelerate its
progress toward the widespread use of ecological indicators in aquatic resource protection,
including the development of multiple indicator assemblages (such as algae and wetland
vegetative condition) and tools for a variety of aquatic resource types, including non-perennial
streams, wetlands, and large rivers.
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Glossary of Terms
Benthic macroinvertebrates: Aquatic insects (often in larval stages) such as dragonfly larvae
and beetles, crustaceans such as crayfish, worms, and mollusks. These small creatures live
throughout the stream bed attached to rocks, vegetation, and logs and sticks or burrowed
into stream bottoms.
Biological assemblages: Key groups of animals and plants such as benthic
macroinvertebrates, fish, or algae that are studied to learn more about the condition of
water resources.
Biological integrity: The state of being able to support and maintain a balanced community
of organisms with a species composition, diversity, and functional organization comparable
to that of the natural habitat of the region.
Ecoregions: Ecological regions that are similar in climate, vegetation, soil type, and geology;
water resources within a particular ecoregion have similar natural characteristics and
similar responses to stressors.
In-streamfish habitat: Areas fish need for concealment and feeding, such as large wood
within the stream banks, boulders, undercut banks, and tree roots.
Intermittent (ephemeral) streams: Streams that flow only during part of the year, such as in
the spring and early summer after snowmelt, or only in direct response to precipitation.
Macroinvertebrate Multimetric Index: The sum of a number of individual measures of
biological condition, such as the number of taxa in a sample, the number of taxa with
different habits and feeding strategies, etc.
National Hydrography Dataset (NHD) Plus: Comprehensive set of digital spatial data
based on U.S. Geological Survey 1:100,000 scale topographic maps that contains
information on surface water features such as streams, rivers, lakes, and ponds.
Nutrients: Substances such as nitrogen and phosphorus that can over-stimulate the growth
of algae and other plants in water. Nutrients in streams and lakes can come from
agricultural and urban runoff, leaking septic systems, sewage discharges, and similar
sources.
0/E (Observed/Expected) Ratio of Taxa Loss: A ratio comparing the number of taxa
expected (E) to exist at a site to the number that are actually observed (0). The taxa
expected at individual sites are based on models developed from data collected at
reference sites.
Perennial streams: Steams that flow throughout the year.
National Rivers and Streams Assessment, 2008 2009
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Glossary of Terms
Physical habitat. For streams and rivers, the area in and around the stream or river,
including its bed, banks, in-stream and overhanging vegetation, and riparian zone.
Probability-based design: A type of random sampling technique in which every element of
the population has a known probability of being selected for sampling.
Reach: Stream segment.
Reference condition: The least-disturbed condition available in an ecological region,
determined based on specific criteria, used as a benchmark for comparison with sampled
sites in the region.
Riparian: Pertaining to a stream or river and its adjacent area.
Riparian disturbance: A measure of the evidence of human activities in and alongside
streams and rivers, such as dams, roadways, construction, pastureland, and trash.
Riparian vegetative cover: The vegetation corridor alongside streams and rivers. Intact
riparian vegetative cover reduces pollution runoff, prevents streambank erosion, and
provides shade, lower temperatures, food, and habitat for fish and other aquatic
organisms.
Streambedsediments: Fine sediments and silt on the streambed. In excess quantities, they
can fill in the habitat spaces between stream cobbles and boulders, and suffocate
macroinvertebrates and fish eggs.
Stream order. Stream size, based on the confluence of one stream with another. First-order
streams are the origin or headwaters. The confluence or joining of two first-order streams
forms a second-order stream, the confluence of two second-order streams forms a third-
order stream, and so on.
Stressors: Effects or substances that are stressful to and therefore degrade aquatic
ecosystems. Stressors can be chemical (e.g., nutrients), physical (e.g., excess sediments on
the streambed), or biological (e.g., competing invasive species).
Taxa: Plural of "taxon"; groupings of living organisms, such as phylum, order, family, genus,
or species. Scientists organize organisms into taxa in order to better identify and
understand them.
Transect: A path or line along which one counts and studies various aspects of a stream,
river, or other study area.
Wadeable streams: Streams that are small and shallow enough to adequately sample by
wading, without a boat.
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Other EMAP assessments
Stoddard, J.L., A.T. Herlihy, B.H. Hill, R.M. Hughes, P.R. Kaufmann, D.J. Klemm, J.M. Lazorchak,
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Relative risk
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Nutrients
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February 2013
National Rivers and Streams Assessment, 2008 2009
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List of Abbreviations and Acronyms
ANC acid-neutralizing capacity
CPL Coastal Plains
EMAP Environmental Monitoring and Assessment Program
EPA U.S. Environmental Protection Agency
GIS geographic information system
MMI multimetric index
NAP Northern Appalachians
NARS National Aquatic Resource Surveys
NHD USGS National Hydrography Dataset
NOAA National Oceanic and Atmospheric Administration
NPL Northern Plains
NRSA National Rivers and Streams Assessment
0/E observed/expected
PCB polychlorinated biphenyl
qPCR quantitative polymerase chain reaction
RBS relative bed stability
SAP Southern Appalachians
SPL Southern Plains
TPL Temperate Plains
UMW Upper Midwest
USGS U.S. Geological Survey
WMT Western Mountains
WSA Wadeable Streams Assessment
XER Xeric region
National Rivers and Streams Assessment, 2008 2009
February 2013
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