United States
Environmental
Protection Agency
Office of Research and Development
Office of Water
Washington, DC 20460
EPA841-B-06-002
December 2006
www.epa.gov/owow/streamsurvey
oEPA Wadeable Streams Assessment
A Collaborative Survey of the Nation's Streams
^•H
'•,*. i-;a.~-'-Y _i_at'
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*.
>to courtesy of the Colorado Division of Wildlife
Inside cover photo courtesy of Michael L Smith, U.S. Fish and Wildlife Service
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Acknowledgments
This report resulted from a ground-breaking collaboration on stream monitoring. States came together
with the U.S. Environmental Protection Agency (EPA) to demonstrate a cost-effective approach for
answering one of the nation's most basic water quality questions: What is the condition of our nation's
streams?
The EPA Office of Water would like to thank the many participants who contributed to this important
effort and the scientists within the EPA Office of Research and Development for their research and
refinement of the survey design, field protocols, and indicator development. Through the collaborative
efforts of state environmental and natural resource agencies, federal agencies, universities, and other
organizations, more than 150 field biologists were trained to collect environmental samples using a
standardized method, and more than 25 taxonomists identified as many as 500 organisms in each sample.
Each participating organization attended a national meeting to discuss and formulate the data analysis
approach, as well as regional meetings to evaluate and refine the results presented in this report.
Collaborators
Alaska Department of Environmental Conservation
Arizona Game and Fish Department
Arkansas Department of Environmental Quality
California Department of Fish and Game
California State Water Resources Control Board
Colorado Department of Public Health and
Environment
Colorado Division of Wildlife
Connecticut Department of Environmental Protection
Delaware Department of Natural Resources
and Environmental Control
Georgia Department of Natural Resources
Idaho Department of Environmental Quality
Illinois Environmental Protection Agency
Iowa Department of Natural Resources
Kansas Department of Health and Environment
Kentucky Division of Water
Louisiana Department of Environmental Quality
Maine Department of Environmental Protection
Maryland Department of Natural Resources
Michigan Department of Environmental Quality
Minnesota Pollution Control Agency
Mississippi Department of Environmental Quality
Missouri Department of Conservation
Montana Department of Environmental Quality
Nevada Division of Environmental Protection
New Hampshire Department of Environmental
Services
New Jersey Department of Environmental Protection
New Mexico Environment Department
New York State Department of Environmental
Conservation
North Carolina Division of Water Quality
North Dakota Department of Health
Ohio Environmental Protection Agency
Oklahoma Conservation Commission
Oklahoma Water Resources Board
Oregon Department of Environmental Quality
Pennsylvania Department of Environmental Protection
South Carolina Department of Health
and Environmental Control
South Dakota Department of Environment
and Natural Resources
South Dakota Game, Fish and Parks
Tennessee Department of Environment and
Conservation
Texas Commission of Environmental Quality
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Utah Division of Water Quality
Vermont Department of Environmental Conservation
Virginia Department of Environmental Quality
Washington State Department of Ecology
West Virginia Department of Environmental
Protection
Wisconsin Department of Natural Resources
Wyoming Department of Environmental Quality
Fort Peck Assiniboine and Sioux Tribes
Guam Environmental Protection Agency
U.S. Geological Survey
U.S. EPA, Office of Environmental Information
U.S. EPA, Office of Water
U.S. EPA, Office of Research and Development
U.S. EPA, Regions 1-10
Center for Applied Bioassessment and Biocriteria
Central Plains Center for Bioassessment
New England Interstate Water Pollution Control
Commission
The Council of State Governments
Great Lakes Environmental Center
TetraTech, Inc.
EcoAnalysts
University of Arkansas
Mississippi State University
Oregon State University
Utah State University
The data analysis team painstakingly reviewed the data set to ensure its quality and performed the data
analysis. This team included Phil Kaufmann, Phil Larsen, Tony Olsen, Steve Paulsen, Dave Peck, John
Stoddard, John Van Sickle, and Lester Yuan from the EPA Office of Research and Development; Alan
Herlihy from Oregon State University; Chuck Hawkins from Utah State University; Daren Carlisle from
the U.S. Geological Survey; and Michael Barbour, Jeroen Gerritson, Erik Lepow, Kristen Pavlik, and Sam
Stribling from TetraTech, Inc.
The report was written by Steve Paulsen and John Stoddard from the EPA Office of Research and
Development and Susan Holdsworth, Alice Mayio, and Ellen Tarquinio from the EPA Office of Water.
Major contributions to the report were made by John Van Sickle, Dave Peck, Phil Kaufmann, and Tony
Olsen from the EPA Office of Research and Development and Peter Grevatt and Evan Hornig from EPA
Office of Water, Alan Herlihy from Oregon State University, Chuck Hawkins from Utah State University,
and Bill Arnold from the Great Lakes Environmental Center. Technical editing and document production
support was provided by RTI International. This report was significantly improved by the external peer
review conducted by Dr. Stanley V Gregory, Ecologist, Oregon State University; Dr. Kenneth Reckhow,
Environmental Engineer, Duke University; Dr. Kent Thornton, Principal Ecologist, FTN Associates; Dr.
Scott Urquhart, Statistician, Colorado State University; and Terry M. Short of the U.S. Geological Survey.
The Quality Assurance Officer for this project was Otto Gutenson from the EPA Office of Water.
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Table of Contents
Acknowledgments ii
Collaborators iii
Executive Summary ES-2
Introduction 2
Chapter 1 — Design of the Wadeable Streams Assessment 6
Why focus on wadeable streams? 6
What area does the WSA cover? 9
What areas are used to report WSA results? 13
How were sampling sites chosen? 15
How were waters assessed? 19
Setting expectations 23
Chapter 2 — Condition of the Nation's Streams 26
Background 26
Indicators of Biological Condition 26
Macroinvertebrate Index of Bio tic Condition 28
Macroinvertebrate Observed/Expected (O/E) Ratio of Taxa Loss 31
Aquatic Indicators of Stress 33
Chemical Stressors 33
Physical Habitat Stressors 39
Biological Stressors 45
Ranking of Stressors 46
Extent of Stressors 46
Relative Risk of Stressors to Biological Condition 48
Combining Extent and Relative Risk 50
Chapter 3 —Wadeable Streams Assessment Ecoregion Results 52
Northern Appalachians Ecoregion 54
Physical Setting 54
Biological Setting 54
Human Influence 54
Summary of WSA Findings 55
Southern Appalachians Ecoregion 58
Physical Setting 58
Biological Setting 58
Human Influence 59
Summary of WSA Findings 59
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Coastal Plains Ecoregion 61
Physical Setting 61
Biological Setting 62
Human Influence 62
Summary ofWSA Findings 63
Upper Midwest Eco region 65
Physical Setting 65
Biological Setting 65
Human Influence 65
Summary ofWSA Findings 66
Temperate Plains Ecoregion 68
Physical Setting 68
Biological Setting 68
Human Influence 68
Summary ofWSA Findings 69
Southern Plains Ecoregion 71
Physical Setting 71
Biological Setting 71
Human Influence 72
Summary ofWSA Findings 72
Northern Plains Ecoregion 74
Physical Setting 74
Biological Setting 74
Human Influence 75
Summary ofWSA Findings 75
Western Mountains Ecoregion 77
Physical Setting 77
Biological Setting 78
Human Influence 78
Summary ofWSA Findings 78
Xeric Ecoregion 81
Physical Setting 81
Biological Setting 81
Human Influence 81
Summary ofWSA Findings 81
V"
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter 4 — Summary and Next Steps 86
Summary 86
Next Steps 88
Glossary of Terms 91
Sources and References 93
General References 93
Stream and River Sampling and Laboratory Methods 94
Probability Designs 95
Ecological Regions 95
Indices of Biotic Integrity 96
Observed/Expected Models 96
Physical Habitat 96
Reference Condition 97
Other EMAP Assessments 97
Biological Condition Gradient/Quality of Reference Sites 97
Relative Risk 97
Nutrients 98
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Figures
1 Strahler stream order diagram 7
2 Stream characteristics change as the stream's size or stream order increases 8
3 Major rivers and streams of the conterminous United States 9
4 Average annual precipitation of the United States, 1961—1990 10
5 Major land cover patterns of the conterminous United States 11
6 Human population density (people per square mile) based on the
2000 U.S. Census Bureau data 12
7 Three major regions were surveyed for the WSA 13
8 Nine ecoregions were surveyed for the WSA 14
9 Length of wadeable, perennial streams in each WSA ecoregion 16
10 Sites sampled for the WSA by EPA Region 17
11 Reach layout for sampling 19
12 Stream macroinvertebrates 20
13 Biological condition of streams based on Macroinvertebrate Index of Biotic Condition 30
14 Macroinvertebrate taxa loss as measured by the O/E Ratio of Taxa Loss 32
15 Total phosphorus concentrations in U.S. streams 35
16 Total nitrogen concentrations in U.S. streams 36
17 Salinity conditions in U.S. streams 37
18 Acidification in U.S. streams 39
19 Streambed sediments in U.S. streams 41
20 In-stream fish habitat in U.S. streams 42
21 Riparian vegetative cover in U.S. streams 43
22 Riparian disturbance in U.S. streams 45
23 Extent of stressors 47
24 Extent of stressors and their relative risk to Macroinvertebrate Condition
and O/E Taxa Loss 49
25 Eco regions surveyed for the WSA 53
26 WSA survey results for the Northern Appalachians ecoregion 56
27 WSA survey results for the Southern Appalachians ecoregion 60
28 WSA survey results for the Coastal Plains ecoregion 63
29 WSA survey results for the Upper Midwest ecoregion 67
30 WSA survey results for the Temperate Plains ecoregion 70
31 WSA survey results for the Southern Plains ecoregion 72
32 WSA survey results for the Northern Plains ecoregion 75
33 WSA survey results for the Western Mountains ecoregion 79
34 WSA survey results for the Xeric ecoregion 83
The Wadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Acronym List
°F degrees Fahrenheit
ANC acid neutralizing capacity
BMPs best management practices
CAAA Clean Air Act Amendments
CWA Clean Water Act
EMAP Environmental Monitoring and Assessment Program
EPA U.S. Environmental Protection Agency
FWS U.S. Fish and Wildlife Service
km kilometers
mi2 square miles
NAPAP National Acid Precipitation Program
NCA National Coastal Assessment
NCCR National Coastal Condition Report
NCCR II National Coastal Condition Report II
NEP National Estuary Program
NEP CCR National Estuary Program Coastal Condition Report
NHD National Hydrography Dataset
NLCD National Land Cover Dataset
NOAA National Atmospheric and Oceanic Administration
O/E observed/expected
PCBs polychlorinated biphenyls
RBS relative bed stability
TDS total dissolved solids
ueq/L microequivalents per liter
USGS U.S. Geological Survey
VOCs volatile organic compounds
WSA Wadeable Streams Assessment
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Executive Summary
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Executive Summary
Executive Summary
"I started out thinking of America as
highways and state lines. As I got to know it
better, I began to think of it as rivers. America
is a great story, and there is a river on every
page of it."
This quote by well-known journalist Charles
Kuralt reflects on the central role that rivers and
streams have played in shaping the history and
character of our nation. Because the health and
survival of U.S. families and communities are
dependent on these waterbodies, their condition,
as well as how they are protected, reflects our
values and choices as a society.
The Wadeable Streams Assessment (WSA)
provides the first statistically defensible summary
of the condition of the nation's streams and small
rivers. In the 35 years since the passage of the
Clean Water Act (CWA), the U.S. Congress,
American public, and other interested parties have
asked the U.S. Environmental Protection Agency
(EPA) to describe the water quality condition of
U.S. waterbodies. These requests have included
seemingly simple questions: Is there a water
quality problem? How extensive is the problem?
Does the problem occur in "hotspots" or is it
widespread? Which environmental stressors affect
the quality of the nation's streams and rivers, and
which are most likely to be detrimental? This
WSA report presents the initial results of what
will be a long-term partnership between EPA,
other federal agencies, states, and tribes to answer
these questions.
Little Washita River, OK, in the Southern
Plains ecoregion (Photo courtesy of Monty Porter).
The WSA encompasses the wadeable streams
and rivers that account for a vast majority of the
length of flowing waters in the United States. To
perform the assessment, EPA, states, and tribes
collected chemical, physical, and biological data
at 1,392 wadeable, perennial stream locations to
determine the biological condition of these waters
and the primary stressors affecting their quality.
Research teams collected samples at sites chosen
using a statistical design to ensure representative
results. The results of this analysis provide a clear
assessment of the biological quality of wadeable,
perennial streams and rivers across the country,
as well as within each of three major climatic and
landform regions and nine ecological regions, or
ecoregions.
The Wadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Executive Summary
The information provided in this report fills an
important gap in meeting the requirements of the
CWA. The purpose of the WSA is four-fold:
• Report on the ecological (biological, chemical,
and physical) condition of all wadeable, peren-
nial streams and rivers within the conterminous
United States. (Pilot assessment projects are
also underway in Alaska and Hawaii.)
• Describe the biological condition of these
systems using direct measures of aquatic life.
Assessments of stream quality have historically
relied primarily on chemical analyses of water,
or sometimes, on the status of game fish.
• Identify and rank the relative importance of
chemical and physical stressors (disturbances)
affecting stream and river condition.
1.7%
• Enhance the capacity of states and tribes to
include these design and measurement tools
in their water quality monitoring programs
so that assessments will be ecologically and
statistically comparable, both regionally and
nationally.
The results of the WSA show that 42% of the
nation's stream length is in poor biological
condition compared to least-disturbed reference
sites in the nine ecoregions, 25% is in fair
biological condition, and 28% is in good biolog-
ical condition (Figure ES-1). Five percent of the
nation's stream length was not assessed for
biological condition during the WSA.
2.0%
9.5%
West
152,425 miles
Plains and Lowlands
242,264 miles
Eastern Highlands
276,362 miles
National
Biological Condition
5.0%
I Good
D Fair
• Poor
D Not Assessed
SJ
Figure ES-I. Biological condition of wadeable streams (U.S. EPA/WSA).
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Executive Summary
Of the three major regions discussed in
this report, the West is in the best biological
condition, with 45% of stream length in good
biological condition. The Plains and Lowlands
region has almost 30% of stream length in good
biological condition and 40% in poor biological
condition. The Eastern Highlands region presents
the most concerns, with only 18% of stream
length in good biological condition and 52% in
poor biological condition.
The WSA also examines the key factors most
likely responsible for diminishing biological
quality in flowing waters, as determined by
aquatic macroinvertebrate communities. The
most widespread stressors observed across the
country and in each of the three major regions
are nitrogen, phosphorus, riparian disturbance,
and streambed sediments. Increases in nutrients
(e.g., nitrogen and phosphorus) and streambed
sediments have the highest impact on biological
condition; the risk of having poor biological
condition was two times greater for streams
scoring poor for nutrients or streambed sediments
than for streams that scored in the good range for
the same stressors (Figure ES-2).
Understanding the current condition of the
nation's wadeable streams and rivers is critical
to supporting the development of water quality
management plans and priorities that help
maintain and restore the ecological condition of
these resources. This report provides a primary-
baseline assessment to track water quality status
and trends. The results of the WSA and similar
assessments in the future will inform the public,
water quality managers, and elected officials of the
effectiveness of efforts to protect and restore water
quality, as well as the potential need to refocus
these efforts.
Readers who wish to learn more about the
technical background of the WSA are directed
to literature cited in the References section at
the end of this report and to material posted on
the EPA Web site at http://www.epa.gov/owow/
streamsurvey.
Extent of Stressor
Relative Risk to
Biological Condition
j-
h-
Ji2.9%
J2.2%
3 10 :
Percentage
1 131 .8%
1— H 30.9%
1— H 25.5%
-\ 24.9%
Hi 9.5%
Hi 9.3%
.0 30 40
Stream Length in Most
0 1
1 1 L. \
h— | 12.2
h-Hl.4
—1 0 A
\ \ 2.4
I— Hi. 4
g— 11.6
HHl.7
2 3 A
Relative Risk
Nitrogen
Phosphorus
Riparian Disturbance
Streambed Sediments
In-stream Fish Habitat
Riparian Vegetative Cover
Salinity
Acidification
Disturbed Condition
Figure ES-2. Extent of stressors and their relative risk to the biological condition of the
nation's streams (U.S. EPA/WSA).
The Wadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Introduction
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Introduction
Introduction
In 1972, the U.S. Congress enacted the
landmark Clean Water Act (CWA) to protect the
nation's vital water resources. A critical section
of the CWA calls for periodic accounting to
Congress and the American public on the success
or failure of efforts to protect and restore the
nation's waterbodies. In recent years, a number of
groups reviewed the available data and concluded
that the U.S. Environmental Protection Agency
(EPA) and state environmental agencies have been
unable to provide Congress and the public with
adequate information regarding the condition of
the nation's waterbodies.
In 2000, the General Accounting Office issued
a report noting that EPA and the states could not
make statistically valid inferences about water
quality and lacked data to support management
decisions. A National Research Council report in
2001 found that a uniform, consistent approach
to ambient monitoring and data collection
was necessary to support core water programs.
In 2002, the National Academy of Public
Administration and the H. John Heinz III Center
for Science, Economics, and the Environment
issued similar conclusions.
Following the 2002 release of the Heinz
Center's report The State of the Nation's Ecosystems,
the national newspaper USAToday published
an editorial discussing the lack of environmental
information available to the public. This editorial
emphasized the failure of state and federal agencies
to fund the collection of necessary environmental
data despite very effective collection of comparable
information on the U.S. economy, population,
energy usage, human health issues, and crime
rate. The editorial concluded that "without such
information, the public doesn't know when to
celebrate environmental successes, tackle new
threats, or end efforts that throw money down a
drain" (USAToday, September 21, 2002).
Little Washita River, OK, in the Southern Plains ecoregion (Photo courtesy of Monty Porter).
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Introduction
To bridge this information gap, EPA, other
federal agencies, states, and tribes, are
collaborating to provide the public with improved
environmental information. This collaboration
includes a new monitoring effort to assess the
quality of the nation's waterbodies, an effort that
has produced reports on three national water
quality assessments during the past five years for
coastal and estuarine waters (see Highlight:
National Report on Coastal Waters). Similar efforts
are planned for other water resource assessments
in the future. The Wadeable Streams Assessment
(WSA)—the first nationally consistent,
statistically valid study of the nation's wadeable
streams—marks the continuation of a
commitment to produce statistically valid
scientific assessments of the nation's fresh waters.
State water quality agencies, tribes, and other
partners, with support from EPA, conducted the
work for the WSA using standardized methods
at all sites to ensure the comparability of results
across the country. Beyond yielding scientifically
credible information on the condition and health
of the nation's wadeable streams, the WSA was
designed to provide states with funding and
expertise that enhances their ability to monitor
and assess the quality of their waters.
EPA and its collaborating partners plan to
conduct similar assessments of other types of
waterbodies (e.g., lakes, rivers, and wetlands) in
the future, with the goal of producing updated
assessments for each type of waterbody every
five years. These repeated studies will ensure that
the public remains informed as to whether the
collective efforts to protect and restore the nation's
waters are meeting with success.
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Introduction
Highlight
National Reports on Coastal Waters
The National Coastal Assessment (NCA) surveys the condition of the nation's coastal resources,
as well as state efforts to protect, manage, and restore coastal ecosystems. The results of these
surveys are compiled periodically into the National Coastal Condition Report (NCCR) series. The
states, EPA, and partner agencies, including the National Oceanic and Atmospheric Administration
(NOAA), U.S. Geological Survey (USGS),and U.S. Fish and Wildlife Service (FWS), issued the National
Coastal Condition Report II (NCCR II) in January 2005 as the second in this series of reports on
environmental surveys of U.S. coastal waters. The NCCR II includes evaluations of 100% of the
nation's estuaries in the conterminous 48 states and Puerto Rico. Federal, state, and local agencies
collected more than 50,000 samples between 1997 and 2000 for the NCCR II, using nationally
consistent methods and a probability-based design to assess five key indices of coastal water health:
water quality, coastal habitat loss, sediment quality, benthic community condition, and fish tissue
contaminants levels.
The National Estuary Program Coastal Condition Report (NEP CCR) focuses specifically on the
condition of the 28 estuaries in the National Estuary Program (NEP) using data collected from 1997
through 2003 for EPA's NCA. The NEP CCR also presents monitoring data collected and analyzed
by each individual NEP and its partners for a variety of estuarine quality indicators. The 28 NEPs are
using these data to develop and implement sets of program-specific indicators of estuarine condition.
National Coastal
Condition Report II
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter 1
Design of the Wade able
Streams Assessment
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Chapter I Design oftheWadeabk Streams Assessment
Design of the
Wadeable Streams
Assessment
Why Focus on Wadeable
Streams?
Like the network of blood vessels that supply
life-giving oxygen and nutrients to all parts
of the human body, streams and rivers form a
network that carries essential water to all parts
of the nation. The human body has far more
small capillaries than large, major arteries and
veins; similarly, only a few U.S. rivers span large
portions of the country (e.g., the Mississippi,
Missouri, or Columbia rivers). Most of the
nation's waterways are much smaller stream
and river systems that form an intimate linkage
between land and water.
The WSA addresses these smaller systems,
which ecologists often refer to as "wadeable"
because they are small and shallow enough to
adequately sample without a boat. Almost every
state, university, federal agency, and volunteer
group involved in water quality monitoring has
experience sampling these smaller flowing waters;
therefore, a wide range of expertise was available
for the WSA's nationwide monitoring effort.
About 90% of perennial stream and river miles
in the United States are small, wadeable streams.
Stream and river ecologists commonly use the
term Strahler stream order to refer to stream size,
and wadeable streams generally fall into the 1st-
through 5th-order range (Figure 1). First-order
streams are the headwaters of a river, where the
life of a river begins; as streams join one another,
their stream order increases. It is important to
note that many Ist-order streams, particularly
those located in the western United States, do
not flow continuously. These intermittent or
ephemeral streams were not included in the WSA
because well-developed indicators to assess these
waterbodies do not yet exist. At the other end of
the range are larger-order rivers and streams that
Sawmill Creek, MA, in the Northern Appalachians ecoregion
(Photo courtesy of Colin Hill,TetraTech, Inc.).
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Chapter I Design oftheWadeabk Streams Assessment
Figure I. Strahler stream order diagram (U.S. EPA/WSA). Stream size is
categorized by Strahler stream order, demonstrated here for a watershed.
The confluence (joining) of two I st-order streams forms a 2nd-order stream;
the confluence of two 2nd-order streams forms a 3rd-order stream.
are too deep for wadeable sampling methods.
These deeper waterbodies will be included in a
future survey of non-wadeable rivers.
Stream order (stream size) affects a stream's
natural characteristics, including the biological
communities that live in the stream, such as fish
and invertebrates. Very small 1 st-order and 2nd-
order streams are often quite clear and narrow
and are frequently shaded by grasses, shrubs, and
trees that grow along the stream bank (Figure 2).
The food base of these streams is found along the
stream bank and tends to consist of leaves and
terrestrial insects, which dominate the streams'
ecology, along with 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, larger 6th- and 7th-
order rivers typically appear muddy because their
flow carries accumulated sediments downstream.
These rivers are wide enough that the canopy
cover along their banks shades only a narrow
margin of water along the river's edge. The food
base for these waterbodies shifts towards in-
stream sources, such as algae; downstream drift of
small organisms; and deposition of fine detritus.
Although the aquatic communities of larger rivers
include the algae and terrestrial insects found in
streams, these rivers are dominated by insects
adapted to filtering and gathering fine organic
particles, and larger fish that are omnivorous
(feeding on plants and animals) and/or
piscivorous (feeding on smaller fish).
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter I Design oftheWadeable Streams Assessment
shredders
•e- 4
I
10
11
12
coarse
particulate
matter
razers
microbes* Predators
x
collectors
collectors
fine
^B particulate
matter
coarse
particulate
matter
microbes
collectors i^.f, -^ V>
s*{ ' %*• predators
J
V_- /
Relative Channel Width
Figure 2. Stream characteristics change as the stream's size or stream order increases
(Vannote et al., 1980).
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter I Design oftheWadeabk Streams Assessment
What Area Does the WSA Cover?
This WSA encompasses the wadeable streams
of the conterminous United States, or lower 48
states (Figure 3)- This land area covers 3,007,436
square miles (mi2) and includes private, state,
tribal, and federal land. Although not included
in this report, initial stream-sampling projects
outside the conterminous United States have
begun and will be included in future assessments.
For example, scientists in Alaska sampled streams
in the Tanana River Basin (a subbasin to the
Yukon River) during 2004 and 2005, and they
expect to report their results in 2007; Guam has
begun implementation of a stream survey; and
Puerto Rico is developing indicators for assessing
the condition of its tropical streams. In addition,
the State of Hawaii began stream sampling using
WSA techniques on the island of Oahu in 2006.
State boundaries offer few insights into the
true nature of features that mold our streams and
rivers. The most fundamental trait that defines
U.S. waters is annual precipitation (Figure 4).
A sharp change occurs on either side of the
Figure 3. Major rivers and streams of the conterminous United States (NationalAtlas.gov, 2006).
Major rivers comprise only 10% of the length of U.S. flowing waters, whereas the nation's wadeable streams
and rivers comprise 90% of the length of U.S. flowing waters.
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter I Design oftheWadeabk Streams Assessment
100th longitude that runs from west Texas
through North Dakota, with precipitation falling
plentifully to the east, but sparsely to the west.
(The high mountains of the western United
States and the Pacific coast are exceptions to the
general scarcity of water in the West.) The east-
west divide in moisture has not only shaped the
character of the nation's waters, but also how they
are used, valued, and the even the legal systems
with which they are managed. A second divide
that defines the nature of U.S. rivers and streams
is the north-south gradient in temperature.
Young Womans Creek, PA, in the Southern
Appalachians ecoregion (Photo courtesy of the
Great Lakes Environmental Center).
Annual Average Precipitation
(in inches) 1961-1990
• <5
• 5-10
• 10-15
15-20
20-25
25-30
30-35
40-50
50-60
60-70
70-80
80-100
100-120
120-140
140-180
180-200
Figure 4. Average annual precipitation of the United States, 1961-1990 (NOAA, National Climatic
Data Center). The 100th longitude meridian runs from Texas north through North Dakota and reveals a major
gradient of precipitation that defines differences in western and eastern streams.
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter I Design oftheWadeabk Streams Assessment
The nation includes a wide diversity of
landscapes, from the varied forests of the East, to
the immense agricultural plains and grasslands
of the Midwest, to the deserts and shrublands
of the Southwest, to the giant mountain ranges
of the West (Figure 5)- In the eastern part of the
country, the Appalachian mountains run from
Maine to Alabama, crossing climatic boundaries
and separating the waters flowing to the Atlantic
Ocean from those flowing to the Gulf of Mexico.
The larger mountain ranges in the West link
their landscapes together: the Rockies through
the heart of the West; the Cascades, which
crown the Northwest in snow; the Sierra Nevada
in California; and the Coastal Range, which
plummets to the Pacific Ocean, with a fault-block
shoreline that stretches from the Santa Monica
mountains to Kodiak Island. The Coastal Plains
of the East and Southeast and the Great Plains of
the interior provide other major landform features
that mark the country.
• Forest
I I Agriculture
CH Wetland
CH Shrubland
I I Urban
^H Bare
"based on NLCD 1992
Figure 5. Major land cover patterns of the conterminous United States (USGS, 2000).
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Chapter I Design oftheWadeabk Streams Assessment
The establishment and spread of European
colonies and the Industrial Revolution intensified
the transformation of the nation's natural
landscape, as greater numbers of people arrived
and modified many of the features of the land and
waters. As the nation's population grew and cities
and towns were established, tens of thousands
of dams were constructed to alter the flow of
virtually every major river in the United States.
Historically, people have tended to live where
water is more abundant. Current population
patterns based on 2000 U.S. Census Bureau
data reflect the historical abundance of waters
in the East and forecast the growing challenges
facing the water-scarce regions in the West, where
population has grown in recent years (Figure
6). The current and future condition of the
nation's waters will continue to be influenced
by population patterns, as well as how the
components of a watershed, including surface
water, groundwater, and the land itself, are used.
Population
Density 2000
(people per square mile)
CZ1 250
Figure 6. Human population density (people per square mile) based on 2000 U.S. Census
Bureau data (ESRI,2005).
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Chapter I Design oftheWadeabk Streams Assessment
What Areas Are Used to Report
WSA Results?
The conterminous United States is the
broadest-scale unit for which WSA results are
reported. For this report, this area has been split
into three major regions—the Eastern Highlands,
the Plains and Lowlands, and the West. These
three regions correspond to major climate and
landform patterns across the United States
(Figure 7).
The Eastern Highlands region is composed
of the mountainous areas east of the Mississippi
River and includes the piedmont to the east
of the Appalachians and the interior plateau
to their west. The Plains and Lowlands region
encompasses the Atlantic and Gulf of Mexico
coastal plains and the lowlands of the Mississippi
Delta, as well as the portions of the Midwest from
the Dakotas down through most of Texas. The
West region includes the western portion of the
country, from the desert southwestern United
States and the Rocky Mountains to the Pacific
Ocean. Chapter 2 of this report describes the
WSA results for these three major regions.
WSA Major Regions*
I I Eastern Highlands
I I Plains and Lowlands
I I West
Abased on Omernik Level III ecoregions
Figure 7. Three major regions were surveyed for the WSA (U.S. EPA/WSA).
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A finer-scale reporting unit included in
the WSA consists of nine ecological regions
(ecoregions) (Figure 8) that further divide the
three major regions. The three major regions
and the nine ecoregions outlined in this report
are aggregations of smaller ecoregions defined by
EPA. Areas are included in an ecoregion based
on similar landform and climate characteristics.
For example, water resources within a particular
ecoregion have similar natural characteristics and
respond similarly to natural and anthropogenic
stressors. Typically, management practices aimed
at preventing degradation or restoring water
quality apply to many flowing waters with similar
problems throughout an ecoregion. This report
presents results by ecoregions because the patterns
of response to stress, and the stressors themselves,
are often best understood in a regional context.
The results for the nine ecoregions are reviewed in
Chapter 3 of this report.
The Eastern Highlands region is divided into
two ecoregions: the Northern Appalachians
ecoregion, which encompasses New England,
New York, and northern Pennsylvania, and the
Southern Appalachians ecoregion, which extends
from Pennsylvania into Alabama, through the
eastern portion of the Ohio Valley, and includes
the Ozark Mountains of Missouri, Arkansas, and
Oklahoma.
WSA Ecological Regions4
I I Northern Appalachians I I Souther
I I Southern Appalachians I I Northen
I I Coastal Plains I I Western
H] Upper Midwest I I Xeric
I I Temperate Plains
*based on Omernik Level III ecoregions
n Pla
n Plains
Mountains
Figure 8. Nine ecoregions were surveyed for the WSA (U.S. EPA/WSA).
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Chapter I Design oftheWadeable Streams Assessment
The Plains and Lowlands region includes five
WSA ecoregions: the Coastal Plains, the Upper
Midwest, the Temperate Plains, the Northern
Plains, and the Southern Plains. The Coastal Plains
ecoregion covers the low-elevation areas of the East
and Southeast, including the Atlantic and Gulf
of Mexico coastal plains and the lowlands of the
Mississippi Delta, which extend from the Gulf of
Mexico northward through Memphis, TN. The
Upper Midwest ecoregion is dominated by lakes
and has little elevation gradient. The Temperate
Plains ecoregion in the midwestern United States
is probably most well-known as the Cornbelt. The
Northern Plains and Southern Plains ecoregions
are better known as the Great Prairies, with the
Northern Plains ecoregion encompassing North
Dakota, South Dakota, Montana, and northeast
Wyoming, and the Southern Plains ecoregion
encompassing parts of Nebraska, Kansas, Colorado,
New Mexico, Oklahoma, and Texas.
The West region includes two WSA ecoregions:
the Western Mountains ecoregion and the arid or
Xeric ecoregion. The Western Mountains ecoregion
includes the Cascade, Sierra Nevada, and Pacific
Coast mountain ranges in the coastal states; the
Gila Mountains in the southwestern states; and the
Bitteroot and Rocky Mountains in the northern
and central mountain states. The Xeric ecoregion
includes both the true deserts and the arid lands of
the Great Basin.
Some states participating in the WSA assessed
an even finer state-scale resolution than the
ecoregion scale by sampling additional random sites
within their state borders. Although these data are
included in the analysis described in this report,
state-scale results are not presented for each state.
These states are preparing similar analyses that
reflect their respective water quality standards and
regulations.
How Were Sampling Sites
Chosen?
The WSA sampling locations were selected
using modern survey design approaches. Sample
surveys have been used in a variety of fields (e.g.,
election polls, monthly labor estimates, forest
inventory analyses, National Wetlands Inventory)
to determine the status of populations or
resources of interest using a representative sample
of a relatively few members or sites. This approach
is especially cost effective if the population is so
large that all components cannot be sampled or
if obtaining a complete census of the resource is
unnecessary to reach the desired level of precision
for describing conditions.
Survey data are frequently reported in the
news. For example, the percentage of children
1—5 years old living in the United States who
have high lead levels in their blood is 2.2% +/-
1.2%, an estimate based on a random sample of
children in the United States. The WSA results
have similar rigor in their ability to estimate the
percentage of stream miles, within a range of
certainty, that are in good condition.
To pick a random sample, the location of
members of the population of interest must
be known. The target population for the WSA
was the wadeable, perennial streams in the
conterminous United States. The WSA design
team used the National Hydrography Dataset
(NHD)—a comprehensive set of digital spatial
data on surface waters—to identify the location of
wadeable, perennial streams. They also obtained
information about stream order from the River
Reach File, a related series of hydrographic
databases that provide additional attributes about
stream reaches. Using these resources, researchers
determined the length of wadeable streams for
each of the nine ecoregions (Figure 9).
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Chapter I Design oftheWadeable Streams Assessment
For this WSA report, the wadeable stream miles
assessed for the nation, regions, and ecoregions are
referred to as the stream length. The total stream
length represented in the WSA for the nation is
671,051 miles. For the Eastern Highlands, Plains
and Lowlands, and West regions, the total stream
length assessed for the WSA is 276,362 miles,
242,264 miles, and 152,425 miles, respectively.
The 1,392 sites sampled for the WSA were
identified using a particular type of random
sampling technique called a probability-based
sample design, in which every element in the
population has a known probability of being
selected for sampling. This important feature
ensures that the results of the WSA reflect the full
range in character and variation among wadeable
streams across the United States. Rules for site
selection included weighting to provide balance
in the number of stream sites from each of the
1st- through 5th-order size classes and controlled
spatial distribution to ensure that sample sites were
distributed across the United States (Figure 10).
The WSA sites were allocated by EPA Region
and WSA ecoregion based on the distribution
of 1st- through 5th-order streams within those
regions. Within each EPA Region, random sites
are more densely distributed where the perennial
1st- through 5th-order streams are more densely
located and more sparsely distributed where
streams are sparse. For example, EPA Region 4
in the southeastern United States includes large
portions of the Southern Appalachian and Coastal
Plains ecoregions. The survey design in EPA
Region 4 identified more sites in the Southern
Appalachians ecoregion, where the stream length
is 178,449 miles, than in the Coastal Plains
ecoregion, where the stream length is 72,130
miles (see Figure 9).
The basic sampling design drew 50 sampling
sites randomly distributed in each of the EPA
Regions and WSA ecoregions. Some of the
unusually dense site patterns visible on Figure
10 occur because some states opted to increase
the intensity of random sampling throughout
National
(lower 48)
Southern Appalachian
Western Mountains
Temperate Plains
Northern Appalachians
Coastal Plains
Upper Midwest
Xeric
Southern Plains
Northern Plains
liiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiu^ »
178,449
126,436
iiiJiJi \Wfl79
'Immmmmn ' ' »' ' ^
72, 1 30
H 36.547
jj 25,989
1 19,263
D 13,445 , , , ,
0 200,000 400,000 600,000 800,000
Figure 9. Length of wadeable, perennial streams in each WSA ecoregion (U.S. EPA/WSA).
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Chapter I Design oftheWadeabk Streams Assessment
V
Figure I 0. Sites sampled for the WSA by EPA Region (U.S. EPA/WSA).
their state to characterize statewide conditions.
Fifteen states, including all states in EPA
Regions 8, 9, and 10, increased the number of
random sites to 50 sites throughout each state
to support state-scale characterizations of stream
condition. States also added clusters of random
sites to characterize areas of special interest in
Washington, Oregon, and California. When sites
from an area of intensification were used in the
ecoregion assessments, the weights associated with
those sites were adjusted so that the additional
sites did not dominate the results. The unbiased
site selection of the survey design ensures that
assessment results represent the condition of the
streams throughout the nation.
An additional 150 reserve replacement sites
were generated for each of the 10 EPA Regions.
These replacement sites were used when site
reconnaissance activities documented that one of
the original stream sites could not be sampled. For
example, sites were replaced when a waterbody
did not meet the definition of a wadeable stream
(e.g., no flowing water over 50% of the reach) or
was unsafe for sampling, or when access to the
stream was denied by the landowner.
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Chapter I \ Design of the Wadeabk Streams Assessment
WSA Sampling Frame
The basis of the WSA target population is 1st- through 5th-order perennial streams, which are
the streams most likely to be wadeable. The sampling frame used to represent the target population
and to select the sites for the WSA is based on the perennial stream network contained in the
USGS-EPA NHD. The NHD is a digitized version of hlOOK USGS topographic maps and shows
both perennial and non-perennial (e.g., intermittent and ephemeral) streams.
The total stream length in the NHD stream and river network labeled perennial in the
conterminous United States is 1,204,859 miles. Of this amount, 1,131,062 miles are 1st- through
4th-order streams, which make up 91% of the total stream length of the nation's flowing waters (see
figure below).
Of the more than I million miles of stream length labeled as perennial, almost 34% (400,000
miles) were found to be non-perennial or non-target waterbodies (e.g., wetlands, reservoirs,
irrigation canals). The remaining target stream length represents the portion of the NHD that
meets criteria for inclusion in the WSA (e.g., perennial, wadeable streams). A portion of that target
stream length was not sampled for various reasons, including denial of access by a landowner or
inaccessibility.
In addition to generating results on the condition of perennial streams, the WSA provides data on
the total length of perennial stream miles in the United States. These results will be loaded into the
NHD so that the database is updated on the status of perennial/non-perennial stream information.
Total NHD Length
1st-4th Order
5th Order 59 409
8th Order
6th Order 12,063 (1%)
7th Order I 31,850(3%)
300,000
1200,000
1,500,000
600,000 900,000
Length (miles)
Estimate of perennial length of streams and rivers from the NHD (U.S. EPA/WSA).
The 1st- through 4th-order streams comprise 91% of total estimated stream length in the NHD.
The I st- through 5th-order streams form the basis for the sampling design frame for the WSA.
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Chapter I Design oftheWadeabk Streams Assessment
How Were Waters Assessed?
Each WSA site was sampled by a two- to four-
person field crew between 2000 and 2004 during
a summer index period. More than 40 trained
crews, comprised primarily of state environmental
staff, sampled 1,392 stream sites using
standardized field protocols. The field protocols
were designed to consistently collect data relevant
to the biological condition of stream resources
and the resources' key stressors.
During each site visit, crews laid out the
sample reach and the numerous transects to
guide data collection (Figure 11). Field crews
sent water samples to a laboratory for basic
chemical analysis, whereas biological samples
collected from 11 transects along each stream
reach were sent to taxonomists for identification
of macroinvertebrates. Crews also completed
roughly 35 pages of field forms, recording data
and information about the physical characteristics
Upstream End of
Sampling Reach
Substrate and Channel
Measuremen
Channel/
Riparian
Cross
Section
Transect
Riparian Vegetation &
Human Disturbance
Instream Fish Cover
Urge Wood
Tally (between
transects)
, Thalweg C>,
\ Profile _-!J^-.
\ Intervals
Downstream End '
of Sampling Reach
Figure I I. Reach layout for sampling (U.S. EPA/WSA).
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Chapter I Design oftheWadeable Streams Assessment
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 is a key feature of the
WSA. Because ecologists use a range of methods
to sample streams, it is often difficult to compare
data collected by different states, regions,
or agencies on a regional or national level.
Standardization allows the data to be combined
to produce a nationally consistent assessment. In
addition to collecting a national set of consistent
data, this nationwide sampling effort provided
an opportunity to examine the comparability of
different sample protocols by applying both the
WSA method and various state or USGS methods
to a subset of the sites. A separate analysis is
underway to examine the comparability of
these methods and explore options for how the
resulting data may be used together.
The WSA uses benthic macroinvertebrates
(e.g., aquatic larval stages of insects, crustaceans,
worms, mollusks) as the biological indicator
of a stream's ecological condition. Benthic
macroinvertebrates live throughout the stream
bed, attaching to rocks and woody debris and
burrowing in sandy stream bottoms and among
the debris, roots, and grasses that collect and
grow along the water's edge (Figure 12). The
Stonefli
Dragan flies,
Damselflies
Mayflies
Caddisflies
Figure I 2. Stream macroinvertebrates (Photo courtesy of Maine Department of Environmental
Protection). Macroinvertebrates in streams serve as the basis for the indicators of biological condition
for the WSA.
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Chapter I Design oftheWadeable Streams Assessment
WSA focuses on these macroinvertebrates
because of their inherent capacity to integrate
the effects of the stressors to which they are
exposed, in combination and over time. Stream
macroinvertebrates generally cannot move very
quickly or very far; therefore, they are affected by,
and may recover from, a number of changes in
physical conditions (e.g., habitat loss), chemical
conditions (e.g., excess nutrients), and biological
conditions (e.g., the presence of invasive or non-
native species). Some types of macroinvertebrates
are affected by these conditions more than others.
Macroinvertebrates provide a measurement
of biological condition or health relative to
the biological integrity of a stream. Biological
integrity represents 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. Macroinvertebrates are
researched by almost every state and federal
program that monitors streams and are also
increasingly evaluated by volunteer organizations
that monitor water quality. In addition, water
quality monitoring and management programs
are enhancing the understanding of the biological
condition of streams by adding other biological
assemblages, including fish and algae.
The WSA supplements information on
the biological 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 stream biology. Some
stressors are naturally occurring, whereas others
result only from human activities, although most
come from both sources.
Most physical stressors are created when we
modify the physical habitat of a stream or its
watershed, such as through extensive urban or
agricultural development, excessive upland or
bank erosion, or loss of streamside trees and
vegetation. Examples of chemical stressors include
toxic compounds (e.g., heavy metals, pesticides),
excess nutrients (e.g., nitrogen and phosphorus),
or acidity from acidic deposition or mine
drainage. Biological stressors are characteristics of
the biota that can influence biological integrity,
such as the proliferation of non-native or invasive
species (either in the streams and rivers, or in the
riparian areas adjacent to these waterbodies).
The WSA water chemistry data allow an
evaluation of the distribution of nutrients,
salinity, and acidification in U.S. streams. The
physical habitat data provide information on the
prevalence of excess sediments, the quality of
in-stream fish habitat, and the quality of riparian
habitat alongside streams. Although these are
among the key stressors identified by states as
affecting water quality, they do not reflect the full
range of potential stressors that can impact water
quality. Future water quality surveys will include
an assessment of additional stressors.
One of the key components of an ecological
assessment is a measure of how important (e.g.,
how common) each stressor is within a region
and how severely it affects biological condition.
In addition to looking at the extent of streams
affected by key stressors, the WSA evaluated the
relative risk posed by key stressors to biological
condition.
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Chapter I \ Design of the Wadeable Streams Assessment
Highlight
Understanding Biological Condition
The main goal of theWSA is to develop a baseline understanding of the biological condition of
our nation's streams. Why is this important?
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 waterbodies. Aquatic plants and
animals—especially the small creatures that are the focus of this study—are constantly exposed
to the effects of various stressors; therefore, they reflect not only current conditions, but also the
cumulative impacts of stresses and changes in conditions overtime.
Benthic macroinvertebrates are widely used to determine biological condition. These organisms
can be found in all 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 waterbody 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 waterbody and decide how they should be controlled, and assess and report on the
effectiveness of management actions. In fact, many specific state responsibilities under the CWA—
such as determining the extent to which waters support aquatic life uses, evaluating cumulative
impacts from polluted runoff, and determining the effectiveness of discharger permit controls—are
tied directly to an understanding of biological condition.
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Chapter I Design oftheWadeabk Streams Assessment
Setting Expectations
To interpret the data collected and assess
current ecological condition, chemical, physical,
and biological measurements must be compared
to a benchmark or estimate of what one would
expect to find in a natural condition. Setting
reasonable expectations for an indicator is one of
the greatest challenges to making an assessment of
ecological condition. Should we take an historical
perspective and try to compare current conditions
to an estimate of pre-colonial conditions, pre-
industrial conditions, or conditions at some other
point in history, or should we accept that some
level of anthropogenic disturbance is expected
and simply use the best of today's conditions as
the benchmark against which everything else is
compared?
These questions, and their answers, all relate
to the concept of reference condition. What
do we use as a reference condition to set the
A researcher collects macroinvertebrate samples
from a small stream in the Northern Appalachians
ecoregion (Photo courtesy of the Vermont Department
of Environmental Conservation).
benchmark for assessing the current status of
these waterbodies? Because of the difficulty of
estimating historical conditions for many of
the WSA indicators, the assessment used the
conditions at a collection of "least-disturbed"
sites as the reference condition. This means
that the condition at these sites represents the
best available chemical, physical, and biological
habitat conditions given the current state of the
landscape. Least-disturbed sites were identified
by evaluating data collected at sites according to a
set of explicit screening levels that define what is
least disturbed by human activities. To reflect the
natural variability across the American landscape,
these levels varied among the nine ecoregions.
The WSA compared physical and chemical data
collected at each site (e.g., nutrients, riparian
condition, chloride, turbidity, fine sediments)
to the screening levels to determine whether any
given site was in least-disturbed condition for its
ecoregion.
Data on land use in the watersheds were not
used to screen-out sites. For example, sites in
agricultural areas with effective best management
practices (BMPs) may have been considered least
disturbed, provided they exhibited chemical and
physical conditions that were among the best
for their region. The WSA also did not use data
on biological assemblages as a screening factor
to select reference sites because that would have
pre-judged expectations for biological condition.
Similarly, when selecting least-disturbed reference
sites for each stressor, the WSA excluded the
specific stressors themselves from the screening
process.
The WSA screening process resulted in the
identification of a set of least-disturbed reference
sites for each WSA ecoregion. These sites were
distributed throughout the ecoregions and
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Chapter I Design oftheWadeable Streams Assessment
covered the range of natural variability across
each area. Some of these sites included a degree of
human-caused variability.
The results from samples collected at the
reference sites for the various indicators (e.g.,
biological condition, nutrients) represent the
range of expected values for least-disturbed
reference condition. The WSA used this reference
distribution as a benchmark for setting thresholds
between good, fair, and poor condition. These
thresholds were then applied to the random sites
to generate the percentage of stream length in
each condition class.
The WSA's approach examined the range
of values for indicators in all of the reference
sites in a region and used the 5th percentile of
the reference distribution for that indicator to
separate the poor sites from fair sites. Using
the 5th percentile means that stream sites and
associated stream length in poor condition
were worse than 95% of the sites used to define
least-disturbed reference condition. Similarly,
the 25th percentile of the reference distribution
was used to distinguish between sites in fair and
good condition. This means that stream length
reported as being in good condition was as good
as or better than 75% of the sites used to define
least-disturbed reference condition.
Within the reference site population, there
exist two sources of variability: natural variability
and variability due to human activities. Natural
variability—the wide range of habitat types
naturally found within each ecoregion—creates
a spread of reference sites representing these
differing habitats. Capturing natural variability in
reference sites helps establish reference conditions
that represent the range of environments in the
ecoregions.
The second source of variation within the
reference population is change resulting from
human activities. Many areas in the United
States have been altered, with natural landscapes
transformed by cities, suburban sprawl,
agricultural development, and resource extraction.
The extent of those disturbances varies across
regions. Some of the regions of the country have
reference sites in watersheds with little to no
evidence of human impact, such as mountain
streams or streams in areas with very low
population densities. Other regions of the country
have few sites that have not been influenced by
human activities. The least-disturbed reference
sites in these widely influenced watersheds
display more variability in quality than those in
watersheds 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.
At a national meeting to discuss data analysis
options, WSA collaborators supported this
reference condition-based approach, which is
consistent with EPA guidance and state practice
on the development of biological and nutrient
criteria. Additional details on how the least-
disturbed condition and benchmarks for the
condition categories were established for the
WSA can be found in the data analysis method
available on the EPA Web site at http://www.epa.
gov/owow/streamsurvey.
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Chapter 2
Condition of the Nations
Streams
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Chapter 2 Condition of the Nation's Streams
Condition of the
Nation's Streams
Background
The CWA explicitly aims "to restore and
maintain the chemical, physical, and biological
integrity of the nation's waters." The WSA
examines these three aspects of water quality
through a small set of commonly used and widely
accepted indicators. Although this WSA report
does not include all aspects of biological integrity
or review all possible chemical, physical, or
biological stressors known to affect water quality,
it does present the results of important indicators
for an entire class of water resources—wadeable,
perennial streams.
This chapter describes the results of the WSA
and is organized as follows:
• Indicators of Biological Condition — Provides
a description of the indicators or attributes of
biological condition that were measured by the
WSA survey and the results of the data analysis.
• Aquatic Indicators of Stress — Presents
findings on the stressors evaluated for the
study.
• Ranking of Stressors — Presents an analysis
of the relative importance of the stressors in
affecting biological condition.
Results for each indicator are shown for the
nation's streams and for the three major regions
(Eastern Highlands, Plains and Lowlands, and
West). Chapter 3 of this report presents indicator
results for each of the nine WSA ecoregions.
Indicators of Biological
Condition
Ecologists evaluate the biological condition of
water resources, including wadeable streams, by
analyzing key characteristics of the communities
of organisms that live in these waterbodies.
These characteristics include the composition
and relative abundance of key groups of animals
(e.g., fish and invertebrates) and plants (e.g.,
periphyton, or algae that attach themselves
to stream bottoms, rocks, and woody debris)
Jellison Meadow Brook, ME, in the Eastern Highlands region
(Photo courtesy of Colin Hill,TetraTech, Inc.).
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Chapter 2 Condition of the Nation's Streams
found in streams. The WSA focused on just one
assemblage, benthic macroinvertebrates (e.g.,
aquatic insects, crustaceans, worms and mollusks);
however, some WSA participants also researched
other assemblages.
Why focus on macroinvertebrates? Macro-
invertebrates are key organisms that reflect the
quality of their environment and respond to
human disturbance in fairly predictable ways.
As all fly-fishermen know, the insects emerging
from streams and rivers are good indicators of
the water quality and serve as an important
food source for both game and non-game fish.
Given the wide geographic distribution of
macroinvertebrates, as well as their abundance
and link to fish and other aquatic vertebrates,
these organisms serve as excellent indicators of the
quality of flowing waters and the human stressors
that affect these systems.
WSA researchers collected samples of these
organisms and sent them to laboratories for
analysis, yielding a data set that provided the
types and number of taxa (i.e., classifications
or groupings of organisms) found at each
site. To interpret this data set, the WSA used
two indicators of biological condition: the
Macroinvertebrate Index of Bio tic Condition and
the Observed/Expected (O/E) Ratio of Taxa Loss.
Macroinvertebrate Index
ofBiotic Condition
The Macroinvertebrate Index ofBiotic
Condition (henceforth referred to as the
Macroinvertebrate Index) is similar in concept
to the economic Consumer Confidence Index
(or the Leading Index of Economic Indicators)
in that the total index score is the sum of
scores for a variety of individual measures, also
What are Taxa?
Taxa (plural of taxon) are groupings of living
organisms, such as phylum, class, order, family,genus,
or species. Biologists scientifically describe and
organize organisms into taxa in order to better
identify and understand them.
called indicators or metrics. To determine the
Leading Index, economists look at a number of
metrics, including manufacturers' new orders
for consumer goods, building permits, money
supply, and other aspects of the economy that
reflect economic growth. To determine the
Macroinvertebrate Index, ecologists look at such
metrics as taxonomic richness, habit and trophic
composition, sensitivity to human disturbance,
and other biotic aspects that reflect "naturalness."
Originally developed as an Index ofBiotic
Integrity for fish in Midwestern streams, the
Macroinvertebrate Index has been modified and
applied to other regions, taxonomic groups, and
ecosystems.
The metrics used to develop the Macro-
invertebrate Index for the WSA covered six
different characteristics of macroinvertebrate
assemblages that are commonly used to evaluate
biological condition:
• Taxonomic richness — This characteristic
represents the number of distinct taxa, or
groups of organisms, identified within a
sample. Many different kinds of distinct taxa,
particularly those that belong to pollution-
sensitive insect groups, indicate a variety of
physical habitats and food sources and an
environment exposed to generally lower levels
of stress.
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Chapter 2 Condition of the Nation's Streams
Highlight
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 waterbody:
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 streams, whereas very small
streams may be naturally devoid offish. 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
also form the base of the food chain for many aquatic vertebrates. Fish are an example of
these aquatic vertebrates and also 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.
TheWSA collaboration began as a partnership among 12 western states; EPA Regions 8,
9, and 10; and EPA's Western Ecology Division (Environmental Monitoring and Assessment
Program [EMAP] West) before it was expanded to include the entire United States. The
original EMAP West program addressed fish, macroinvertebrates, and algae; future WSA reports
will also address multiple assemblages.
To learn more about EMAP West and its use of multiple biological assemblages, visit www.
epa.gov/emap/west/index.html.
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Chapter 2 Condition of the Nation's Streams
Taxonomic composition — Ecologists
calculate composition metrics by identifying
the different taxa groups, determining which
taxa in the sample are ecologically important,
and comparing the relative abundance of
organisms in those taxa to the whole sample.
Healthy stream systems have organisms from
across many different taxa groups, whereas
unhealthy stream systems are often dominated
by a high abundance of organisms in a small
number of taxa that are tolerant of pollution.
Taxonomic diversity — Diversity metrics look
at all the taxa groups and the distribution
of organisms among those groups. Healthy
streams should have a high level of diversity
throughout the assemblage.
Feeding groups — Many macroinvertebrates
have specialized strategies to capture and
process food from their aquatic environment.
As a stream degrades from its natural
condition, the distribution of animals among
the different feeding groups will change. For
example, as a stream loses its canopy (a source
of leaves and shading), the aquatic community
will shift from a more diverse food chain to
one of predominantly algal-feeding animals
that are tolerant of warm water.
Habits — Just like other organisms, benthic
macroinvertebrates are characterized by
certain habits, including how they move and
where they live. These habits are captured
in the habit metrics. For example, some
taxa burrow under the streambed sediment,
whereas others cling to rocks and debris within
the stream channel. A stream that naturally
includes a diversity of habitat types will
support animals with diverse habits; however,
if a stream becomes laden with silt, the
macroinvertebrates that cling, crawl, and swim
will be replaced by those that burrow.
• Pollution tolerance — Each macroinvertebrate
taxa can tolerate a specific range of stream
contamination, which is referred to as
their pollution tolerance. Once this level is
exceeded, the taxa are no longer present in that
area of the stream. Highly sensitive taxa, or
those with a low pollution tolerance, are found
only in streams with good water quality.
The specific metrics chosen for each of these
categories varied among the nine ecoregions used
in the analysis. Each metric was scored and then
combined to create an overall Macroinvertebrate
Index for each region, with values ranging from
0 to 100. For the WSA, analysts calculated a
Macroinvertebrate Index score for each site,
factored in the stream length represented by the
site, and then generated an estimate of the stream
length in a region, and nationally, with a given
Macroinvertebrate Index score.
Six different characteristics of macroinvertebrate
assemblages are commonly used to evaluate
biological condition in wadeable streams (Photo
courtesy of Lauren Holbrook, IAN Image Library).
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Chapter 2 Condition of the Nation's Streams
Findings for the Macroinvertebrate Index
of Biotic Condition
As illustrated in Figure 13, the Macroinverte-
brate Index indicator results show that 42% of
the nation's stream length (281,170 miles) is
in poor condition, 25% (167,092 miles) is in
fair condition, and 28% (189,236 miles) is in
good condition compared to the least-disturbed
reference condition in each of the nine WSA
ecoregions. The 28% of stream length in good
condition has conditions most similar to the
reference distribution derived from the best-
available (least-disturbed) sites in each ecoregion.
The 5% (33,553 miles) of unassessed stream
length results from the fact that Ist-order streams
in New England were not sampled for the WSA.
Macroinvertebrate Index results show that
the Eastern Highlands region has the highest
proportion of stream length (52%, or 143,170
miles) in poor condition, followed by the Plains
and Lowlands (40%, or 96,905 miles) and the
West (27%, or 41,754 miles).
Stream Length (mi)
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33,553
Total: 67 1,051
50,320
56,501
143,170
26,371
Total: 276,362
70,257
70,257
96,905
4,845
Total: 242,264
68,672
39,403
41,754
2,596
Total: 152,425
10
50
60
20 30 40
Percentage of Stream Miles
• Good D Fair • Poor D Not Assessed
Figure 13. Biological condition of streams based on Macroinvertebrate Index of Biotic Condition
(U.S. EPA/WSA). The Macroinvertebrate Index combines metrics of benthic community structure and function
into a single index for each region. The thresholds for defining good, fair, and poor condition were developed for
each of the nine WSA ecoregions based on condition at the least-disturbed reference sites. Stream length in good
condition is most similar to least-disturbed reference condition; in fair condition has Macroinvertebrate Index
scores worse than 75% of reference condition; and in poor condition has Macroinvertebrate Index scores worse
than 95% of reference condition.
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Chapter 2 Condition of the Nation's Streams
What are Confidence Intervals?
Confidence intervals (i.e., the small lines at the end of the bars in this report's charts) are provided to convey the
level of certainty or confidence that can be placed in the information presented in this report. For example, for the
national Macroinvertebrate Index, the WSA finds that 28.2% of the nation's stream length is in good condition, and the
confidence is +/- 2.8%, which means that there is a 95% certainty that the real value is between 25.4% and 3 1%. The
confidence interval depends primarily on the number of sites sampled; as more streams are sampled, the confidence
interval becomes narrower, meaning there is more confidence in the findings. When fewer streams are sampled, the
confidence interval become broader, meaning there is less certainty in the findings. Figure 13 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.
Macroinvertebrate Observed/
Expected (O/E) Ratio ofTaxa
Loss
The Macroinvertebrate O/E Ratio ofTaxa
Loss (henceforth referred to as O/E Taxa Loss)
measures a specific aspect of biological health:
taxa that have been lost at a site. The taxa
expected (E) at individual sites are predicted
from a model developed from data collected at
least-disturbed reference sites; thus, the model
allows a precise matching of sampled taxa with
those that should occur under specific, natural
environmental conditions. By comparing the list
of taxa observed (O) at a site with those expected
to occur, the proportion of expected taxa that
have been lost can be quantified as the ratio of O/
E. Originally developed for streams in the United
Kingdom, O/E Taxa Loss models are modified
for the specific natural conditions in each area
for which they are used. The O/E Taxa Loss
indicator is currently used by several countries
and numerous states in the United States.
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).
These values are interpreted as the percentage of
the expected taxa present. Each tenth of a point
less than 1 represents a 10% loss of taxa at a site;
thus, an O/E Taxa Loss score of 0.9 indicates
that 90% of the expected taxa are present and
10% are missing. O/E Taxa Loss values must
be interpreted in the context of the quality of
reference sites used to build the predictive models,
because the quality of reference sites available in
a region sets the bar for what is expected (i.e.,
regions with lower-quality reference sites will
have a lower bar). Although an O/E Taxa Loss
value of 0.8 means the same thing regardless of
a region (i.e., 20% of taxa have been lost relative
to reference conditions in each region), the true
amount of taxa loss will be underestimated if
reference sites are of low quality.
The WSA developed three O/E Taxa Loss
models to predict the extent of taxa loss across
streams of the United States, one model for each
of the three major regions outlined in this report
(Eastern Highlands, Plains and Lowlands, West).
Analysts used the O/E Taxa Loss scores observed
at each site to generate estimates of the nation's
stream length estimated to fall into four categories
of taxa loss.
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Chapter 2 Condition of the Nation's Streams
Although in many cases the results of O/E
Taxa Loss analysis are similar to the results of the
Macroinvertebrate Index, such agreement will
not always occur. The O/E Taxa Loss indicator
examines a specific aspect of biological condition
(biodiversity loss), whereas the Macroinvertebrate
Index combines multiple characteristics. For
the WSA, the two indicators provided similar
results in those WSA ecoregions that had a lower
disturbance signal among their reference sites.
Findings for O/E Taxa Loss
Figure 14 displays the national and regional
O/E Taxa Loss summary. These data 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. Forty-two percent
of the nation's stream length retained more than
90% of expected taxa; 13% lost 10-20% of taxa;
26% lost 20-50% of taxa; and 13% lost more
than 50% of taxa.
Within the three regions, stream length in
the Eastern Highlands experienced the greatest
loss of expected taxa, with 17% experiencing
a loss of 50% or more. An additional 29% of
stream length in this region lost 20—50% of
taxa; 13% lost 10-20% of taxa; and only 28%
of stream length lost fewer than 10% of taxa.
Eleven percent of stream length in the Plains and
Lowlands region experienced a taxa loss of 50%
or more, 25% of stream length lost 20—50% of
National
(lower 48)
Eastern Highlands
12.6% 26.0% 12.5%
41.5%
7.4%
16.8%
29.1%
13.4% 27.9%
12.8%
Plains and Lowlands
West
I 1.3%
25.0%
13.3%
47.0%
3.4%
6.9%
21.2%
9.6%
57.9%
4.4%
10 20 30 40 50 60 70 80
Percentage of Stream Miles
90 100
• > 50% Taxa Loss Q 20-50% Taxa Loss
D 1 0-20% Taxa Loss •< 1 0% Taxa Loss D Not Assessed
Figure I 4. Macroinvertebrate taxa loss as measured by the O/E Ratio of Taxa Loss (U.S. EPA/WSA).
The O/E Taxa Loss indicator displays the loss of taxa from a site compared to reference for that region.
Scores 0. 1 lower than reference represent a 1 0% loss in taxa.
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Chapter 2 Condition of the Nation's Streams
taxa; 13% lost 10-20% of taxa; and 47% lost
fewer than 10% of taxa. In the West, 7% of
stream length experienced a taxa loss of 50% or
more, 21% of stream length lost 20—50% of taxa;
10% lost 10-20% of taxa; and 58% of stream
length lost less than 10% of taxa.
Aquatic Indicators of Stress
As people use the landscape, their actions
can produce effects that are stressful to aquatic
ecosystems. These aquatic stresses can be
chemical, physical, or in some cases, biological.
The WSA has selected a short list of stressors
from each of these categories as indicators for
assessment. This list is not intended to be all-
inclusive, and in fact, some important stressors
are not included because there is currently no
way to assess them at the site scale (e.g., water
withdrawals for irrigation). Future assessments
of U.S. stream and river condition will include a
more comprehensive list of stressors from each of
these categories.
WSA indicators are based on direct measures
of stress in the stream or adjacent riparian areas,
not on land use or land cover alterations, such
as row crops, mining, or grazing. Many human
activities and land uses can be sources of one
or more stressors to streams; however, the WSA
only assesses stressors to determine the general
condition of the resource and which stressors are
most significant and does not track the source of
these stressors. Source tracking, an expensive and
time-consuming process, is a logical future step
for the WSA and similar national assessments.
A summary of the national and regional results
for indicators of chemical and physical habitat
are shown in Figures 15 through 22. WSA results
for these indicators for each of the nine WSA
ecoregions are presented in Chapter 3 of this
report.
Chemical Stressors
Four chemical stressors were assessed as
indicators in the WSA: total phosphorus, total
nitrogen, salinity, and acidification. These
stressors were selected because of national or
regional concerns about the extent to which
each might be impacting the quality of stream
biota. The thresholds for interpreting data were
developed from a set of least-disturbed reference
sites for each of the nine WSA ecoregions, as
described in Chapter 1, Setting Expectations. The
results for each ecoregion were tallied to report
on conditions for the three major regions and the
entire nation.
Total Phosphorus Concentrations
Phosphorus is usually considered the most
likely nutrient limiting algal growth in U.S.
freshwater waterbodies. Because of the naturally
low concentrations of phosphorus in stream
systems, even small increases in phosphorus
concentrations can impact a stream's water
quality. Some waters—such as streams originating
from groundwater in volcanic areas of eastern
Oregon and Idaho—have naturally higher
concentrations of phosphorus. This natural
variability is reflected in the regional thresholds
for high, medium, and low, which are based on
the least-disturbed reference sites for each of the
nine WSA ecoregions.
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Chapter 2 Condition of the Nation's Streams
Highlight
Nutrients and Eutrophication in Streams
Eutrophication is a condition characterized by excessive plant growth that results from high
levels of nutrients in a waterbody. Although eutrophication is a natural process, human activities
can accelerate this condition by increasing the rate at which nutrients and organic substances enter
waters from their surrounding watersheds. Agricultural runoff, urban runoff, leaking septic systems,
sewage discharges, eroded stream banks, and similar sources can increase the flow of nutrients and
organic substances into streams, and subsequently, into downstream lakes and estuaries. These
substances can overstimulate 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 nation's lakes, reservoirs, and estuaries. It has also been more recently
recognized as a contributing factor to stream degradation. In broadest terms, nutrient over-
enrichment of streams is a problem because of the negative impacts on aquatic life (the focus of
the WSA); adverse health effects on humans and domestic animals; aesthetic and recreational use
impairment; and excessive nutrient input into downstream waterbodies, such as lakes.
Excess nutrients in streams 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 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 the screens on water intakes of water treatment plants and
industries.
Nutrient enrichment in streams has also been demonstrated to affect animal communities in
these waterbodies (see the References section at the end of this report for examples of published
studies). 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 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 2 Condition of the Nation's Streams
Phosphorus influx leads to increased algal
growth, which reduces dissolved oxygen levels and
water clarity within the stream. (See Highlight:
Nutrients and Eutrophication in Streams for
more information about the impacts of excess
phosphorus and nitrogen.) Phosphorus is a
common component of fertilizers, and high
phosphorus concentrations in streams may be
associated with poor agricultural practices, urban
runoff, or point-source discharges (e.g., effluents
from sewage treatment plants).
National
Findings for Total Phosphorus
Approximately 31% of the nation's stream
length (207,355 miles) has high concentrations
of phosphorus, 16% (108,039 miles) has medium
concentrations, and 49% (327,473 miles) has
low concentrations (Figure 15). Of the three
major regions, the Eastern Highlands has the
greatest proportion of stream length with high
concentrations of phosphorus (43%, or 117,730
miles), followed by the Plains and Lowlands
(25%, or 60,324 miles) and the West (19%, or
28,174 miles) regions.
Stream Length (mi)
327,473
108,039
207,355
28,184
Total: 671,051
10
70
20 30 40 50 60
Percentage of Stream Miles
] Low D Medium D High D Not Assessed
Figure 15. Total phosphorus concentrations in U.S. streams (U.S. EPA/WSA). Percent of stream length
with low, medium, and high concentrations of phosphorus based on regionally relevant thresholds derived
from the least-disturbed regional reference sites. Low concentrations are most similar to reference condition;
medium concentrations are greater than the 75th percentile of reference condition; and high concentrations are
greater than the 95th percentile of reference condition.
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Chapter 2 Condition of the Nation's Streams
Total Nitrogen Concentrations
Nitrogen, another nutrient, is particularly
important as a contributor to coastal and
estuarine algal blooms. Nitrogen is the primary
nutrient limiting algal growth in some regions
of the United States, particularly in granitic or
basaltic geology found in parts of the Northeast
and the Pacific Northwest. Increased nitrogen
inputs to a stream can stimulate growth of excess
algae, such as periphyton, which results in low
dissolved oxygen levels, a depletion of sunlight
available to the streambed, and degraded habitat
conditions for benthic macroinvertebrates and
other aquatic life (see Highlight: Nutrients ,
Eutrophication in Streams). Common sources of
excess nitrogen include fertilizers, wastewater,
animal wastes, and atmospheric deposition.
Findings for Total Nitrogen
A significant portion of the nation's stream
length (32%, or 213,394 miles) has high
concentrations of nitrogen compared to least-
disturbed reference conditions, 21% (138,908
miles) has medium concentrations, and 43%
(290,565 miles) has relatively low concentrations
(Figure 16). As with phosphorus, the Eastern
Stream Length (mi)
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290,565
1 38,908
213,394
28,184
Total: 67 1,051
87,297
45,410
1 1 7,284
26,371
Total: 276,3 62
1 25,785
49,454
65,715
1,310
Total: 242,264
78,346
42,527
31,247
305
Total: 152,425
0 10 20 30 40 50 60
Percentage of Stream Miles
• Low CD Medium CD High CD Not Assessed
Figure 16. Total nitrogen concentrations in U.S. streams (U.S. EPA/WSA). Percent of stream length
with low, medium, and high concentrations of nitrogen based on regionally relevant thresholds derived from the
least-disturbed regional reference sites. Low concentrations are most similar to reference condition; medium
concentrations are greater than the 75th percentile of reference condition; and high concentrations are greater
than the 95th percentile of reference condition.
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Chapter 2 Condition of the Nation's Streams
Highlands region has the greatest proportion
of stream length with high concentrations of
nitrogen (42%, or 117,284 miles), followed by
the Plains and Lowlands (27%, or 65,715 miles)
and the West (21%, or 31,247 miles).
Salinity
Excessive salinity occurs in areas with high
evaporative losses of water and can be exacerbated
by repeated use of water for irrigation or by
water withdrawals. Both electrical conductivity
and total dissolved solids (TDS) can be used as
measures of salinity; however, conductivity was
used for the WSA.
Findings for Salinity
Roughly 3% of the nation's stream length
(19,889 miles) has high levels of salinity, 10%
(69,585 miles) has medium levels, and 83%
(553,530 miles) has low levels compared to levels
found in least-disturbed reference sites for the
nine WSA ecoregions (Figure 17). The Plains
and Lowlands region has the greatest proportion
of stream length with high levels of salinity (5%,
or 12,113 miles), followed by the West (3%,
or 4,009 miles) and Eastern Highlands (1%, or
3,593 miles).
Stream Length (mi)
National
(lower 48)
10 20
80 90 100
30 40 SO 60 70
Percentage of Stream Miles
• Low D Medium • High D Not Assessed
Figure I 7. Salinity conditions in U.S. streams (U.S. EPA/WSA). This indicator is based on electrical
conductivity measured in water samples. Thresholds are based on conditions at least-disturbed regional
reference sites.
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Chapter 2 Condition of the Nation's Streams
Acidification
Streams and rivers can become acidic through
the effects of acid deposition (e.g., acid rain) or
acid mine drainage, particularly from coal
mining. Previous studies have shown that these
issues, while of concern, tend to be focused in a
few geographic regions of the country. Streams
and rivers can also be acidic because of natural
sources, such as high levels of dissolved organic
compounds. The WSA identifies the extent of
systems that are not acidic, naturally acidic (i.e.,
similar to reference), and acidic because of
anthropogenic disturbance. This last category
includes streams that are acidic because of
deposition (either chronic or episodic) or because
of mine drainage.
Acid rain forms when smokestack and
automobile emissions (particularly sulfur dioxide
and nitrogen oxides) combine with moisture in
the air to form dilute solutions of sulfuric and
nitric acid. Acid deposition can also occur in dry
form, such as the particles that make up soot.
When wet and dry deposition fall on sensitive
watersheds, they can have deleterious effects on
soils, vegetation, and streams and rivers.
In assessing acid rain's effects on flowing
waters, the WSA relied on a measure of the
water's ability to buffer inputs of acids, called
acid-neutralizing capacity (ANC). When ANC
values fall below zero, the water is considered
acidic and can be either directly or indirectly
toxic to biota (i.e., by mobilizing toxic metals,
such as aluminum). When ANC is between 0
and 25 milliequilivents, 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 (NAPAP).
Acid mine drainage forms when water moves
through mines and mine tailings, combining
with sulfur released from certain minerals to form
strong solutions of sulfuric acid and mobilize
many toxic metals. As in the case of acid rain,
the acidity of waters in mining areas can be
assessed by using ANC values. Mine drainage
also produces extremely high concentrations
of sulfate—much higher than those found in
acid rain. Although sulfate is not directly toxic
to biota, it serves as an indicator of mining's
influence on streams and rivers. When ANC
values and sulfate concentrations are low, acidity
can be attributed to acid rain. When ANC values
are low and sulfate concentrations are high,
acidity can be attributed to acid mine drainage.
Mine drainage itself, even if not acidic, can harm
aquatic life; however, the WSA does not include
an assessment of the extent of mine drainage that
is not acidic.
Acidic mine drainage forms when water moves
through mines and mine tailings (Photo courtesy
of Ben Fertig, IAN Image Library).
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Chapter 2 Condition of the Nation's Streams
Stream Length (mi)
National
(lower 48)
10 20
80 90 100
30 40 SO 60 70
Percentage of Stream Miles
L~H Good (not acidic) L~H Fair (naturally acidic) d Poor (anthropogenically acidic) L~H Not Assessed
Figure 18. Acidification in U.S. streams (U.S. EPA/WSA). Streams are considered acidic when ANC values
fall below zero. Streams are considered sensitive to acidification during rainfall events when ANC values are
between 0 and 25 milliequilivents. Both ranges were scored as anthropogenically acidic in poor condition. Acidic
streams with high concentrations of sulfate are associated with acid mine drainage, whereas low concentrations
of sulfate indicate acidification due to acid rain.
Findings for Acidification
Figure 18 shows that about 2% of the nation's
stream length (14,763 miles) is impacted by
acidification from anthropogenic sources. These
sources include acid deposition (0.7%), acid
mine drainage (0.4%), and episodic acidicity
due to high-runoff events (1%). Although these
percentages appear relatively small, they reflect a
significant impact in certain parts of the United
States, particularly in the Eastern Highlands
region, where 3% of the stream length (9,396
miles) is impacted by acidification.
Physical Habitat Stressors
A number of human activities can potentially
impact the physical habitat of streams upon which
the biota rely. Soil erosion from road construction,
poor agricultural practices, and other disturbances
can result in increases in the amount of fine
sediment on the stream bottom; these sediments
can negatively impact macroinvertebrates and fish.
Physical alterations to vegetation along stream
banks, alterations to the physical characteristics
within the stream itself, and changes in the flow of
water all have the potential to impact stream biota.
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Chapter 2 Condition of the Nation's Streams
Although many aspects of stream and river
habitats can become stressful to aquatic organisms
when these aspects are modified, the WSA focuses
on four specific stressors as habitat indicators:
streambed sediments, in-stream fish habitat,
riparian vegetation, and riparian disturbance.
Streambed Sediments
The supply of water and sediments from
drainage areas affects the shape of river channels
and the size of streambed particles in streams
and rivers. One measure of the interplay between
sediment supply and transport is relative bed
stability (RBS). The measure of RBS used in
the WSA is a ratio that compares measures of
particle size of observed sediments to the size of
sediments that each stream can move or scour
during its flood stage (based on measures of the
size, slope, and other physical characteristics of
the stream channel). The expected RBS ratio
differs naturally among regions, depending
upon landscape characteristics, such as geology,
topography, hydrology, natural vegetation, and
natural disturbance history.
Values of the RBS ratio can be either
substantially lower (e.g., finer, more unstable
streambeds) or higher (e.g., coarser, more stable
streambeds) than those expected, based on
the range found at least-disturbed reference
sites. Both high and low values are considered
to be indicators of ecological stress. Excess
fine sediments in a stream bed can destabilize
streams when the supply of sediments from the
landscape exceeds the ability of the stream to
move them downstream. This imbalance results
from a number of human uses of the landscape,
including agriculture, road building, construction,
and grazing. Streams with significantly more
stable streambeds than reference condition (e.g.,
evidence of hardening and scouring, streams that
have been lined with concrete) were not included
in the assessment of this indicator. These stream
conditions occurred so rarely in the survey that
it was not necessary to separate them from the
overall population. The WSA focuses on increases
in streambed sediment levels, represented by
lower-than-expected streambed stability as the
indicator of concern.
Lower-than-expected streambed stability may
result either from high inputs of fine sediments
(e.g., erosion) or increases in flood magnitude
or frequency (e.g., hydrologic alteration). When
low RBS results from inputs of fine sediment, the
sediment can fill in the habitat spaces between
stream cobbles and boulders. The instability
(low RBS) resulting from hydrologic alteration
can be a precursor to channel incision and gully
formation.
WSA researchers collected data on indicators
of biological condition and aquatic indicators of
stress at 1,392 wadeable stream locations in the
conterminous United States (Photo courtesy of
TetraTech, Inc.).
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Chapter 2 Condition of the Nation's Streams
Findings for Stream-bed Sediments
Approximately 25% of the nation's stream
length (167,092 miles) has streambed sediment
characteristics in poor condition compared
to regional reference condition (Figure 19).
Streambed sediment characteristics are rated fair
in 20% of the nation's stream length (132,197
miles) and good in 50% of stream length
(336,196 miles) compared to reference condition.
The two regions with the greatest percentage of
stream length in poor condition for streambed
sediment characteristics are the Eastern Highlands
(28%, or 77,381 miles) and the Plains and
Lowlands (26%, or 63,958 miles), whereas the
West has the lowest percentage of stream length
(17%, or 26,522 miles) in poor condition for this
indicator.
In-stream Fish Habitat
The most diverse fish and macroinvertebrate
assemblages are found in streams and rivers that
have complex forms of habitat, such as boulders,
undercut banks, tree roots, and large wood within
the stream banks. Human use of streams and
riparian areas often results in the simplification of
this habitat, with potential effects on biological
Stream Length (mi)
National
(lower 48)
Eastern
Highlands
50.1%
24.9%
ijl5.3
Plains and
Lowlands
I 36.2%
110.4%
12.5%
26.4%
JJ1 2.0%
West
336,196
132,197
167,092
35,566
Total: 671,051
100,043
70,196
77,381
28,742
Total: 276,3 62
143,178
30,283
63,958
4,845
Total: 242,264
91,912
31,705
26,522
2,286
Total: 152,425
60
70
20 30 40 50
Percentage of Stream Miles
• Good D Fair • Poor D Not Assessed
Figure 19. Streambed sediments in U.S. streams (U.S. EPA/WSA). This indicator measures the percentage
of streambeds impacted by increased sedimentation, which indicates alteration from reference condition as
defined by least-disturbed reference sites in each of the nineWSA ecoregions.
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Chapter 2 Condition of the Nation's Streams
integrity. The WSA used a habitat complexity
measure that sums the amount of in-stream fish
concealment features and habitat consisting of
undercut banks, boulders, large pieces of wood,
brush, and cover from overhanging vegetation
within a stream and its banks.
Findings for In-stream Fish Habitat
Twenty percent of the nation's stream length
(130,928 miles) is in poor condition for in-
stream fish habitat, 25% (166,851 miles) is in fair
condition, and 52% (345,766 miles) is in good
condition compared to least-disturbed reference
condition (Figure 20). In the three major regions,
National
(lower 48)
the highest proportion of stream length in poor
condition for in-stream habitat is in the Plains
and Lowlands (37%, or 89,638 miles), whereas
only 12% of stream length (18,748 miles) in the
West and 8% of stream length (22,797 miles) in
the Eastern Highlands region is rated poor for this
indicator.
Riparian Vegetative Cover
The presence of complex, multi-layered
vegetative cover in the corridor along a stream or
river is a measure of how well the stream network
is buffered against sources of stress in the
Stream Length (mi)
10
60
70
20 30 40 SO
Percentage of Stream Miles
• Good D Fair • Poor D Not Assessed
Figure 20. In-stream fish habitat in U.S. streams (U.S. EPA/WSA). This indicator sums the amount of
in-stream habitat that field crews found in streams. Habitat consisted of undercut banks, boulders, large pieces
of wood, and brush. Thresholds are based on conditions at regional reference sites.
TheWadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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Chapter 2 Condition of the Nation's Streams
watershed. Intact riparian areas can help reduce
nutrient and sediment runoff from the
surrounding landscape, prevent streambank
erosion, provide shade to reduce water
temperature, and provide leaf litter and large
wood to serve as food and habitat for stream
organisms. The presence of large, mature canopy
trees in the riparian corridor indicates riparian
longevity; the presence of smaller woody
vegetation typically indicates that riparian
vegetation is reproducing and suggests the
potential for future sustainability of the riparian
corridor. The WSA uses a measure of riparian
vegetative cover that sums the amount of woody
National
(lower 48)
cover provided by three layers of riparian
vegetation: the ground layer, woody shrubs, and
canopy trees.
Findings for Riparian Vegetative Cover
Nineteen percent of the nation's stream length
(129,748 miles) is in poor condition due to
severely simplified riparian vegetation, 28% of
stream length (190,034 miles) is in fair condition,
and almost 48% (319,548 miles) is in good
condition relative to least-disturbed reference
condition in each of the nine WSA ecoregions
(Figure 21). The West (12%, or 18,596 miles)
and Eastern Highlands (18%, or 48,640 miles)
Stream Length (mi)
SO
60
20 30 40
Percentage of Stream Miles
• Good D Fair • Poor D Not Assessed
Figure 21. Riparian vegetative cover in U.S. streams (U.S. EPA/WSA). This indicator sums the amount of
woody cover provided by three layers of riparian vegetation: the ground layer, woody shrubs, and canopy trees.
Thresholds are based on conditions at regional reference sites.
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Chapter 2 Condition of the Nation's Streams
regions have similar proportions of stream length
with riparian vegetation in poor condition,
though this equates to a greater number of
stream miles in the Eastern Highlands region,
where water is more abundant. In the Plains and
Lowlands region, a larger proportion of stream
length (26%, or 62,881 miles) has riparian
vegetation in poor condition.
The most diverse fish and macroinvertebrate
assemblages are found in streams and rivers
that have complex forms of habitat, such as
boulders, undercut banks, tree roots, and
large wood within the stream banks (Photo
courtesy of Michael L Smith, F WS).
Riparian Disturbance
The vulnerability of the stream network to
potentially harmful human activities increases
with the proximity of those activities to the
streams. The WSA uses a direct measure of
riparian human disturbance that tallies 11 specific
forms of human activities and disturbances
along the stream reach and their proximity to a
stream in 22 riparian plots along the stream. For
example, streams scored medium if one type of
human influence was noted in at least one-third
of the plots, and streams scored high if one or
more types of disturbance were observed in the
stream or on its banks at all of the plots.
Findings for Riparian Disturbance
Twenty-six percent of the nation's stream
length (171,118 miles) has high levels of human
influence along the riparian zone that fringes
stream banks, and 24% of stream length (158,368
miles) has relatively low levels of disturbance
(Figure 22). The Eastern Highlands region has
the greatest proportion of stream length with
high riparian disturbance (29%, or 79,591 miles),
followed by the Plains and Lowlands (26%, or
62,504 miles) and the West (19%, or 29,570
miles). One of the striking findings of the WSA
is the widespread distribution of intermediate
levels of riparian disturbance; 47% of the nation's
stream length (314,052 miles) has intermediate
levels of riparian disturbance when compared to
reference condition, and similar percentages are
found in each of the three major regions.
It is worth noting that for the nation
and the three regions, the amount of stream
length with good riparian vegetative cover was
significantly greater than the amount of stream
length with low levels of human disturbance
in the riparian zone. This finding warrants
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Chapter 2 Condition of the Nation's Streams
Stream Length (mi)
National
(lower 48)
Eastern
Highlands
Plains and
Lowlands
West
23.6%
46.8%
J--|—I 25.5%
~JJH.I%
121.3%
H 40.4%
) 28.8%
19.5%
18.8%
55.l%h
25.8%
0.3%
\ 34.6%
\ 45.8%
19.4%
0.2%
158,368
314,052
171,1 18
27,513
Total: 671,05 I
58,703
I 11,697
79,591
26,371
Total: 276,362
45,546
133,487
62,504
727
Total: 242,264
52,739
69,81 I
29,570
305
Total: 152,425
0 10 20 30 40 50 60
Percentage of Stream Miles
• Low D Medium • High D Not Assessed
Figure 22. Riparian disturbance in U.S. streams (U.S. EPA/WSA). This indicator is based on field
observations of I I different types of human influence (e.g., dams, pavement, pasture) and their proximity to
a stream in 22 riparian plots along the stream.
additional investigation, but suggests that land
managers and property owners are protecting and
maintaining healthy riparian vegetation buffers,
even along streams where disturbance from roads,
agriculture, and grazing is widespread.
Biological Stressors
Although most of the factors identified as
stressors to streams and rivers are either chemical
or physical, there are biological factors that also
create stress in wadeable streams. Biological
assemblages can be stressed by the presence of
non-native species that can either prey on, or
compete with, native species. In many cases, non-
native species have been intentionally introduced
to a waterbody; for example, brown trout and
brook trout are common inhabitants of streams in
the higher elevation areas of the West, where they
have been stocked as game fish.
When non-native species become established in
either vertebrate or invertebrate assemblages, their
presence conflicts with the definition of biological
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Chapter 2 Condition of the Nation's Streams
Little Washita River, OK, in the Plains and Lowlands region (Photo courtesy of Monty
Porter).
integrity that the CWA is designed to protect
(i.e., "having a species composition, diversity, and
functional organization comparable to that of the
natural habitat of the region"). Therefore, to the
extent that non-native species compete with and
potentially exclude native species, they might be
considered a threat to biological integrity. These
indicators were not included in the WSA, but
may be included in future assessments.
Ranking of Stressors
A prerequisite to making policy and
management decisions is to understand the
relative magnitude or importance of potential
stressors. It is important to consider both the
prevalence of each stressor (i.e., what is its extent,
in miles of stream, and how does it compare to
other stressors) and the severity of each stressor
(i.e., how much influence does it have on
biological condition, and is its influence greater
or smaller than the influence of other stressors).
The WSA presents separate rankings of the
extent and the relative severity of stressors to the
nation's flowing waters. Ideally, both of these
factors (extent and effect) should be combined
into a single measure of relative importance.
EPA is pursuing methodologies for combining
the two rankings and will present them in future
assessments.
Extent of Stressors
Figure 23 shows the WSA stressors ranked
according to the proportion of stream length that
is in poor condition. Results are presented for
the nation (top panel) and for each major region,
with the stressors ordered (in all panels) according
to their relative extent nationwide.
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Chapter 2 Condition of the Nation's Streams
Figure 23 reveals that excess total nitrogen
is the most pervasive stressor for the nation,
although it is not the most pervasive in each
region. Approximately 32% of the nation's stream
length (213,394 miles) shows high concentrations
of nitrogen compared to reference conditions.
In the Plains and Lowlands region, nitrogen
is at high concentrations in 27% of stream
length (65,715 miles), whereas this proportion
climbs to 42% (117,285 miles) in the Eastern
Highlands region. Even in the West, where levels
of disturbance are generally lower than the other
major regions, excess total nitrogen is found
in 21% of the stream length (31,247 miles).
Phosphorus exhibits comparable patterns to
nitrogen and is the second most-pervasive stressor
for the nation's stream length.
Stream Length (mi)
National N
(lower 48) p
RD
:-E^hs$ ss
Sr$M Rsvr
JM^V
^V5^ As
Highlands P
RD
r~TA^rrpr¥ i-sFH
JMTm^ RVC
A-
-------
Chapter 2 Condition of the Nation's Streams
The least-common stressors for the nation's
stream length are salinity and acidification. Only
3% (19,889 miles) and 2% (14,763 miles),
respectively, of the nation's stream length is in
poor condition for salinity and acidification levels.
Although these stressors are not present in large
portions of the nation's streams, they can have a
significant impact where they do occur.
The extent of stressors measured in the WSA
varies across the three major regions. In the Plains
and Lowlands region, the stressor rated poor for
the greatest proportion of stream length (37%, or
89,638 miles) is loss of in-stream fish habitat. In
the Eastern Highlands region, high total nitrogen
and total phosphorus concentrations were found
in more than 42% of the stream length (117,285
and 117,730 miles, respectively). In the West,
no stressor is found to affect more than 21% of
stream length (31,247 miles), although nitrogen,
phosphorus, and riparian disturbance are the
most widespread stressors in this region as well.
Relative Risk of Stressors to
Biological Condition
This report borrows the concept of relative risk
from the medical field to address the question of
severity of stressor effects. We have all heard that
we run a greater risk of developing heart disease if
we have high cholesterol levels. Often such results
are presented in terms of a relative-risk ratio (e.g.,
the risk of developing heart disease is 4 times
higher for a person with a total cholesterol level
greater than 300 mg than for a person with a total
cholesterol level of less than 150 mg).
The relative-risk values for aquatic stressors
can be interpreted in the same way as the
cholesterol example. For each of the key stressors,
Figure 24 depicts how much more likely a stream
is to have poor biological condition if stream
length is in poor condition for a stressor or if high
concentrations of a stressor are present than if the
stream length is in good condition for a stressor
or a stressor is found at low concentrations.
Because different aspects of the macroinvertebrate
assemblage (i.e., biological condition vs. taxa loss)
are expected to be affected by different stressors,
the WSA calculates relative risk separately for
each of the two biological condition indicators
(Macroinvertebrate Index and O/E Taxa Loss).
A relative-risk value of 1 indicates that there
is no association between the stressor and the
biological indicator, whereas values greater than 1
suggest that the stressor poses a greater relative risk
to biological condition. The WSA also calculates
confidence intervals (Figure 24) for each relative
risk ratio. When the confidence interval extending
above and below the ratio does not overlap the
value of 1, the relative risk estimate is statistically
significant.
The relative risks shown in Figure 24 provide
an estimate of the severity of each stressor's
effect on the macroinvertebrate community in
streams. Almost all of the stressors evaluated
for the WSA were associated with increased
risk for macroinvertebrates. Evaluating relative
risk provides insight on which stressors might
be addressed to improve biological condition.
Excess nitrogen, phosphorus, and streambed
sediments stand out as having the most significant
impacts on biological condition based on both
the Macroinvertebrate Index and O/E Taxa Loss
indicators. Findings show that streams with
relatively high concentrations of nutrients or excess
streambed sediments are two to four times more
likely to have poor macroinvertebrate condition.
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Chapter 2 Condition of the Nation's Streams
Extent of Stressor
Relative Risk to
Macroinvertebrate
Condition
Relative Risk
O/E
Taxa Loss
•—{ 3 1.8%
30.9%
h
h
h
h
H2
H2<
H 19.5%
H 19.3%
25.5%
HHl.4
2.1
2.2
N
Eastern P
Highlands RD
SS
West
l_
b
• 2.6%
fo.5%
-| 17.1*
-| I/. 4%
1
1 1 7
1 I-/
1
1
1 • 1
1 ~t \
| J.I
2.5
i
1
1
1
1
| Z.J
1 i n
1
1
3.2
4.5
20
30
40
Percentage Stream Length in Most
Disturbed Condition
234
Relative Risk
234
Relative Risk
N = Nitrogen RD = Riparian Disturbance 1-sFH = In-stream Fish Habitat S = Salinity
P = Phosphorus SS = Streambed Sediments RVC = Riparian Vegetative Cover A = Acidification
Figure 24. Extent of stressors and their relative risk to Macroinvertebrate Condition and O/E
Taxa Loss (U.S. EPA/WSA). This figure shows the association between a stressor and biological condition and
answers the question,"What is the increased likelihood of poor biological condition when stressor X is rated
in poor condition?" It is important to note that this figure treats each stressor independently and does not
account for the effects of combinations of stressors.
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Chapter 2 Condition of the Nation's Streams
There are differences in relative risk from
a geographic perspective. In general, the West
exhibits a higher relative risk for the majority
of stressors than the Eastern Highlands and
the Plains and Lowlands regions. There are
also differences associated with the different
indicators of biological condition. The O/E
Taxa Loss indicator has somewhat higher relative
risk ratios for most of the stressors than the
Macroinvertebrate Index. Additional analysis is
needed to further explore these differences.
In this assessment of relative risk, it is
impossible to separate completely the effects
of the individual stressors that often occur
together. For example, streams with high nitrogen
concentrations often exhibit high phosphorus
concentrations, and streams with high riparian
disturbance often have sediments far in excess of
expectations; however, the analysis presented in
Figure 24 treats the stressors as if they operate
independently.
Combining Extent and Relative
Risk
The most comprehensive assessment of the
ranking of stressors comes from evaluating both
the extent (Figure 23) and relative risk (Figure 24)
results. Stressors that pose the greatest overall risk
to biological integrity will be those that are both
widespread (i.e., rank high in terms of the extent
of stream length in poor condition for a stressor
in Figure 23) and whose effects are potentially
severe (i.e., exhibit high relative risk ratios in
Figure 24). The WSA facilitates this combined
evaluation of stressor importance by including
side-by-side comparisons of the extent of stressors
and relative risk to macroinvertebrate condition
in Figure 24.
An examination of nationwide results suggests
some common patterns for key stressors and
the two indicators of biological condition. Total
nitrogen, total phosphorus, and excess streambed
sediments are stressors posing the greatest relative
risk nationally (relative risk greater than 2), and
they also occur in 25—32% of the nation's stream
length. This suggests that management decisions
aimed at reducing excess sediment, nitrogen,
and phosphorus loadings to streams could have a
positive impact on macroinvertebrate biological
integrity and prevent further taxa loss across the
country.
High salinity in the West is strongly associated
with a poor Macroinvertebrate Index score
(relative risk = 2.5) and O/E Taxa Loss score
(relative risk > 3-1 or = 3-2); however, the rarity of
this occurrence (salinity affects only 3% of stream
length in the West region) suggests that excess
salinity is a local issue requiring a locally targeted
management approach rather than a national or
regional effort.
Relative risks for all stressors in the West region
are consistently larger than for the nation overall
or for the other two regions, yet the extent of
streams in poor condition for these stressors is
consistently lower in the West. This suggests that
although the stressors are not widespread in the
West, the region's streams are particularly sensitive
to a variety of disturbances.
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Chapter 3
Wadeable Streams Assessment
Ecoregion Results
-------
Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Wadeable Streams
Assessment Ecoregion
Results
The WSA is designed to report on three
geographic scales: national, regional, and
ecoregional. Chapter 2 presented the national-
and regional-scale results, and this chapter will
focus on the results for the nine WSA ecoregions,
Ecoregions are areas that contain similar
environmental characteristics, such as climate,
vegetation, soil type, and geology. EPA has
defined ecoregions at various scales, ranging from
coarse (Level I) ecoregions at the continental scale
to fine (Levels III and IV) ecoregions that divide
states into smaller ecosystem units. Ecoregions are
designed to be used in environmental assessments,
for setting water quality and biological criteria,
and to set management goals for non-point source
pollution.
The nine WSA ecoregions are aggregations of
the Level III ecoregions delineated by EPA for
the conterminous United States. This chapter
provides background information on physical
setting, biological setting, and human influence
for each of the WSA ecoregions and describes
WSA results for the wadeable stream length
throughout each ecoregion. The WSA results
may not be extrapolated to an individual state or
stream within the ecoregion because the study
design was not intended to characterize stream
conditions at these finer scales. Note that a
number of states implement randomized designs
at the state scale to characterize water quality
throughout their state, but these characterizations
are not described in this WSA report.
Manistee River, Ml, in the Upper Midwest
ecoregion (Photo courtesy of the Great Lakes
Environmental Center).
The nine ecoregions encompass a variety of
habitats and land uses, and the least-disturbed
reference sites used to set benchmarks for good, fair,
and poor condition reflect that variability. For some
ecoregions, the variability among reference sites
is very small, while it is larger in others. During a
series of WSA workshops held around the country,
professional biologists examined the variability of
reference sites and implications to the benchmarks
used to characterize an ecoregion and to compare
stream condition across ecoregions. These
benchmarks or thresholds were adjusted for those
ecoregions where there was a disturbance signal
associated with the variability among reference
sites. Additional details on the development of
benchmarks or thresholds for each of the indicators
can be found in the data analysis method available
in Chapter 1 and on the EPA Web site at http://
www.epa.gov/owow/streamsurvey.
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
This report includes brief descriptions of the
WSA ecoregions. It should be noted that there
are many specific and unique features within each
ecoregion that are not fully captured in these brief
descriptions (see the References section at the end
of this report for more information). The nine
ecoregions displayed in Figure 25 and defined in
this text are the following:
Northern Appalachians
Southern Appalachians
Coastal Plains
Upper Midwest
Temperate Plains
Southern Plains
Northern Plains
Western Mountains
Xeric.
WSA Ecological Regions*
I I Northern Appalachians I I Southern Plains
I I Southern Appalachians I I Northern Plains
I I Coastal Plains I I Western Mountains
I I Upper Midwest I I Xeric
EH Temperate Plains ^ ^ ^^ ^ m ^.^
Figure 25. Ecoregions surveyed for the WSA (U.S. EPA/WSA).
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Northern Appalachians
Ecoregion
Physical Setting
The Northern Appalachians ecoregion covers
all of the New England states, most of New
York, the northern half of Pennsylvania, and
northeastern Ohio. This ecoregion encompasses
New York's Adirondack and Catskill mountains
and Pennsylvania's mid-northern tier, including
the Allegheny National Forest. Major river
systems for the Northern Appalachians ecoregion
are the St. Lawrence, Allegheny, Penobscot,
Connecticut, and Hudson rivers, and major
waterbodies include Lake Ontario, Lake Erie,
New York's Finger Lakes, and Lake Champlain.
The total stream length represented in the WSA
for the Northern Appalachians ecoregion is
97,913 wadeable stream miles.
The topography of this ecoregion is generally
hilly, with some intermixed plains and old
mountain ranges. River channels in the glaciated
uplands of the northern parts of this ecoregion
have steep profiles and rocky beds, 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 land area
of Northern Appalachians ecoregion comprises
some 139,424 mi2 (4.6% of the United States),
with about 4,722 mi2 (3-4%) of land under
federal ownership. Based on satellite images from
the 1992 National Land Cover Dataset (NLCD),
the distribution of land cover in this ecoregion is
69% forested and 17% planted/cultivated, with
the remaining 14% of the ecoregion comprised of
other types of land cover.
Cedar Stream, NH, in the Northern Appalachians
ecoregion (Photo courtesy of Colin Hill,TetraTech, Inc.).
Biological Setting
Contemporary 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 anadromous fish, including shad,
alewife, salmon, and sturgeon.
Human Influence
Early European settlers in 17th-century New
England removed beaver dams, allowing floods
to pass more quickly, thereby flushing sediment
and decreasing the diversity and availability of
riparian habitat. Forests were cleared to introduce
crops and pasture for grazing animals, and these
efforts caused the erosion of sediments, increased
nutrients, and reduced riparian habitat. Roughly
96% of the original virgin forests of the eastern
and central states were gone by the 1920s.
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Smaller tributaries in this ecoregion were
often disrupted through splash damming — a
19th century practice of creating dam ponds
for collecting timber and then exploding the
dams to move timber downstream with the
resulting torrent of flood waters. These waters
carried flushed sediment and wood downstream,
and these materials scoured many channels to
bedrock. Streams that were not splash dammed
currently have tens to hundreds of times more
naturally occurring woody debris and deeper
pools. During the 18th and early 19th centuries,
streams with once-abundant runs of anadromous
fish declined due to stream sedimentation,
clogging from sawmill discharges, and the effects
of dams. Increased human and animal waste
from agricultural communities changed stream
nutrient chemistry. When agriculture moved west
and much of the eco region's eastern farmland
converted back into woodlands, sediment yields
declined in some areas.
Today, major manufacturing, chemical,
steel, and power production (e.g., coal, nuclear,
oil) occur in the large metropolitan areas
found around New York City and the states of
Connecticut and Massachusetts. Many toxic
substances, including petroleum products,
organochlorines, polychlorinated biphenyls
(PCBs), and heavy metals, along with increased
nutrients such as nitrates and phosphates, are
the legacy of industrial development. There are
currently 215 active, 6 proposed, and 45 former
EPA Superfund National Priority List sites in the
Northern Appalachian eco region.
It is also common for treated wastewater
effluent to account for much of the stream flow
downstream from major urban areas in this
ecoregion. Treated wastewater can be a major
source of nitrate, ammonia, phosphorus, heavy
metals, volatile organic chemicals (VOCs), PCBs,
and other toxic compounds.
This ecoregion supports forestry; mining;
fishing; wood processing of pulp, paper, and
board; tourism; and agricultural activities, such as
dairy cattle farming, potato production, poultry
farming, and timber harvesting.
The approximate population within the
Northern Appalachians ecoregion is 40,550,000,
representing approximately 14% of the total
population of the United States.
Summary ofWSA Findings
A total of 85 WSA sites were sampled during
the summer of 2004 to characterize the condition
of wadeable streams in the Northern Appalachians
ecoregion. An overview of the WSA survey results
for this ecoregion is shown in Figure 26. These
results may not be extrapolated to accurately
assess the ecological condition of an individual
state or stream within the ecoregion because the
study design was not intended to characterize
stream conditions at these finer scales.
It should be noted that about 27% of wadeable
stream length in the Northern Appalachians
ecoregion was not assessed because small,
Ist-order streams in New England were not
included in the sample frame. These streams
were excluded from the WSA due to a decision
to match an earlier New England random design.
The numbers cited below apply to the 73% of
wadeable stream length that was assessed in the
Northern Appalachians ecoregion.
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Northern Appalachians Ecoregion
97,91 3 miles
134%
45%
H5%
27%
Riparian Disturbance
19%
Streambed Sediments
28%
In-stream Fish Habitat
144%
13%
16%
27%
Riparian Vegetative Cover
Acidification
70%
H3%
27%
20 40 60
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/ETaxa Loss:
• >50%TaxaLoss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
d Not Assessed
40 60
Percentage Stream Length
• Low
n Medium
• High
D Not Assessed
100 0 20 40 60 E
Percentage Stream Length
H Good
D Fair
• Poor
D Not Assessed
Figure 26. WSA survey results for the Northern Appalachians ecoregion (U.S. EPA/WSA). Bars show
the percentage of stream length within a condition class for a given indicator. Lines with brackets represent
the width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Northern Appalachians
ecoregion said that many least-disturbed reference
sites in this ecoregion are nearly undisturbed
streams, with sparse human population in the
immediate watershed; therefore, the reference
condition for the ecoregion is of very high quality.
Biological Condition
• The findings of the Macroinvertebrate Index
show that 45% of stream length in the
Northern Appalachians ecoregion is in poor
condition, 15% is in intermediate or fair
condition, and 13% is in good condition
when compared to least-disturbed reference
condition. As noted above, Ist-order streams,
which are generally considered to be of high
quality in this ecoregion, were not included in
the WSA.
• The O/E Taxa Loss results show that 50% of
stream length in the Northern Appalachians
ecoregion has lost 10% or more of the
macroinvertebrate taxa expected to occur, and
19% has lost more than 50% of taxa. These
results indicate that 23% of stream length has
retained 90% of the groups or classes of
organisms expected to occur based on least-
disturbed reference condition.
Indicators of Stress
Leading indicators of stress in the Northern
Appalachians ecoregion include total phosphorus,
total nitrogen, streambed sediments, and riparian
vegetative cover.
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Approximately 45% of stream length in the
Northern Appalachians ecoregion has high
phosphorus concentrations, 16% has medium
phosphorus concentrations, and 12% has low
phosphorus concentrations based on least-
disturbed reference condition.
Similarly, approximately 45% of the
eco region's stream length has high nitrogen
concentrations, 10% has medium nitrogen
concentrations, and 18% has low nitrogen
concentrations based on least-disturbed
reference condition.
Riparian disturbance, or evidence of human
influence in the riparian zone, is at high levels
in 20% of stream length, at medium levels
in 34% of stream length, and at low levels in
19% of stream length.
Salinity is found at high levels in 1% of stream
length, at medium levels in 8% of stream
length, and at low levels in 64% of stream
length.
Streambed sediments are rated poor in 29% of
stream length in the Northern Appalachians
eco region, fair in 14%, and good in 28%.
In-stream fish habitat is in poor condition in
16% of stream length, fair in 13% of stream
length, and good in 44%.
Vegetative cover in the riparian zone along
stream banks is in poor condition for 26% of
stream length, fair condition for 27% of stream
length, and good condition for 20% of stream
length.
Acidification, which is primarily associated with
acid rain in this ecoregion, is rated poor in 3%
of stream length.
Stream channels in the glaciated uplands of the Northern Appalachians
are characterized by steep profiles and rocky beds (Photo courtesy of
Lauren Holbrook, IAN Image Library).
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Southern Appalachians
Ecoregion
Physical 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 land area of the Southern Appalachians
ecoregion covers about 321,900 mi2 (10.7%
of the United States), with about 42,210 mi2
(13-1%) of land under federal ownership. Many
significant public lands, such as the Great Smoky
Mountains National Park, the George Washington
and Monongahela national forests, and the
Shenandoah National Park, reside within this
ecoregion. The topography is mostly hills and low
mountains, with some wide valleys and irregular
plains. Piedmont areas are included within the
Southern Appalachians ecoregion.
Rivers in this ecoregion flow mostly over
bedrock and other resistant rock types, with steep
channels and short meander lengths. Major rivers
such as the Susquehanna, James, and Potomac,
along with feeders into the Ohio and Mississippi
river systems, such as the Greenbrier River in
West Virginia, originate in this ecoregion. The
total stream length represented in the WSA for
the Southern Appalachians ecoregion is 178,449
wadeable stream miles.
This ecoregion's climate is considered
temperate wet, and annual precipitation
totals average 40 to 80 inches. Mean annual
temperature ranges from 55 to 65 °F. Based
on satellite images in the 1992 NLCD, the
distribution of land cover in this ecoregion is 68%
forested and 25% planted/cultivated, with the
remaining 7% in other types of land cover.
Biological Setting
The Southern Appalachians ecoregion has
some of the greatest aquatic animal diversity of
any area in North America, especially for species
Young Womans Creek,
PA, in the Southern
Appalachians
ecoregion (Photo
courtesy of the Great
Lakes Environmental
Center).
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Chapter 3 \ Wadeable Streams Assessment Ecoregion Results
of amphibians, fishes, mollusks, aquatic insects,
and crayfishes. Salamanders, plants, and fungi
reach their highest North American diversity in
the Southern Appalachians ecoregion; however,
some 18% of animal and plant species in the
ecoregion are threatened or endangered.
Some areas in the Southern Appalachians
ecoregion are among the least-impacted pre-
settlement vegetative cover in the United States,
such as the spruce-fir forests in the southern part
of the ecoregion. The Great Smoky Mountains
National Park and other national forests continue
to protect exceptional stands of old-growth forest
riparian ecosystems.
Human Influence
The effects of habitat fragmentation, urbaniza-
tion, agriculture, channelization, diversion, and
impoundments on river systems have altered a
large amount of stream length in the Southern
Appalachians ecoregion. Placer mining, which
disrupts streambeds and increases a stream's
ability to transport fine sediments that influence
habitat and water quality downstream, began in
the Appalachians in the 1820s. In addition, some
800 mi2 were surface mined in the Appalachian
Highlands between 1930 and 1971, leading
to the acidification of streams and reduction
of aquatic diversity. Placer mining and surface
mining operations have introduced many toxic
contaminants to river systems in the Southern
Appalachians ecoregion, including arsenic,
antimony, copper, chromium, cadmium,
nickel, lead, selenium, silver, and zinc. There
are 224 active, 5 proposed, and 46 deleted EPA
Superfund National Priority List sites in this
ecoregion.
Economic activities in the Southern
Appalachians ecoregion include forestry,
coal mining, and some local agriculture and
tourism industries. Petroleum and natural gas
extraction are prevalent along the coal belt,
and the ecoregion supports coal, bauxite, zinc,
copper, and chromium mining activities. Utility
industries include hydro-power in the Tennessee
Valley and numerous coal-fired plants throughout
the ecoregion. Significant agricultural activities
are alfalfa production in Pennsylvania, with apple
and cattle production occurring throughout the
ecoregion. Wood processing and pulp, paper, and
board production are also prevalent.
Approximately 50,208,000 people live in the
Southern Appalachians ecoregion, representing
approximately 17% of the total population of the
United States.
Summary ofWSA Findings
A total of 184 random sites were sampled
during the summer of 2004 to characterize the
condition of wadeable streams in the Southern
Appalachians ecoregion. An overview of the WSA
survey results for the ecoregion is shown in Figure
27- These results may not be extrapolated to an
individual state or stream within the ecoregion
because the study design was not intended to
characterize stream conditions at these finer scales.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Southern Appalachians
ecoregion said that the least-disturbed reference
streams in the ecoregion represent varying degrees
of human influence. Although some reference
streams are in remote areas, others are intricately
linked with road systems in narrow floodplains.
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Southern Appalachians Ecoregion
I 78,449 miles
Macroinvertebrate Index
21%
H 24%
-155%
O/ETaxa Loss
36%
Phosphorus
Streambed Sediments
15%
Nitrogen
(20%
H4I%
(39%
H4I%
44%
33%
20 40 60 80
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
D Not Assessed
Salinity
^i%
11%
40 60 f
Percentage Stream Length
| Low
D Medium
• High
D Not Assessed
41%
62%
100 0 20 40 60
Percentage Stream Length
| Good
D Fair
• Poor
D Not Assessed
Figure 27. WSA survey results for the Southern Appalachians ecoregion (U.S. EPA/WSA). Bars
show the percentage of stream length within a condition class for a given indicator. Lines with brackets
represent the width of the 95% confidence interval around the percent of stream length. Percents may not
add up to 100 because of rounding.
Biological Condition
• The Macroinvertebrate Index shows that 55%
of stream length in the Southern Appalachians
ecoregion is in poor condition, 24% is in
fair or intermediate condition, and 21% is in
good condition compared to least-disturbed
reference condition.
• The O/E Taxa Loss results show that 65% of
stream length in the Southern Appalachians
ecoregion has lost 10% or more of the
macroinvertebrate taxa that are expected to
occur, and 16% has lost more than 50% of
taxa. These results also indicate that 30% of
stream length has retained 90% of the groups
or classes of organisms expected to occur based
on least-disturbed reference condition.
Indicators of Stress
Leading indicators of stress in the Southern
Appalachians ecoregion include total nitrogen,
total phosphorus, riparian disturbance, and
streambed sediments.
• Forty-one percent of stream length in the
Southern Appalachians ecoregion has high
phosphorus concentrations, 15% has medium
phosphorus concentrations, and 44% has low
phosphorus concentrations based on least-
disturbed reference condition.
• Nitrogen concentrations in the ecoregion
are high in 41% of stream length, medium
in 20% of stream length, and low in 39%
of stream length based on least-disturbed
reference condition.
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• Riparian disturbance, or evidence of human
influence in the riparian zone, is at high levels
in 33% of stream length, at medium levels
in 44% of stream length, and at low levels in
23% of stream length.
• Salinity is found at high levels in only 2% of
stream length, at medium levels in 11% of
stream length, and at low levels in 87% of
stream length.
• Streambed sediments are rated poor in 27%
of stream length in the Southern Appalachians
ecoregion, fair in 32%, and good in 41%.
• In-stream fish habitat is in poor condition in
4% of stream length, fair in 34% of stream
length, and good in 62%.
• Vegetative cover in the riparian zone along
Southern Appalachian stream banks is in poor
condition in 13% of stream length, fair in
33% of stream length, and good in 54% of
stream length.
• Acidification, which is primarily associated
with acidic deposition and acid mine drainage
in this ecoregion, is rated poor in 3% of stream
length.
Coastal Plains Ecoregion
Physical Setting
The Coastal Plains ecoregion covers the
Mississippi Delta and Gulf Coast, north along the
Mississippi River to the Ohio River, all of Florida
and eastern Texas, and the Atlantic seaboard from
Florida to New Jersey. The total land area of this
ecoregion is about 395,000 mi2 (13-2% of the
United States), with 25,890 mi2 (6.6%) of land
under federal ownership. River systems lying
within or intersecting the Coastal Plains ecoregion
are the Mississippi, Suwannee, Savannah,
Roanoke, Potomac, Delaware, Susquehanna,
James, Sabine, Brazos, and Guadalupe rivers.
Rivers in the Coastal Plains meander broadly
across flat plains created by thousands of years
of river deposition and form complex wetland
topographies with levees, backswamps, and oxbow
lakes. Rivers typically drain densely vegetated
catchment areas, while well-developed soils and
less intensive rains and subsurface flows keep
suspended sediment levels in the rivers relatively
low. The Mississippi River carries large loads
of sediments from dry lands in the central and
western portion of the drainage. The total stream
length represented in the WSA for the Coastal
Plains ecoregion is 72,130 wadeable stream miles.
Sandy Creek, LA, in the Coastal Plains
ecoregion (Photo courtesy of the Great Lakes
Environmental Center).
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
The Coastal Plains ecoregion contains about
one-third of all remaining U.S. wetlands, more
than half of U.S. forested wetlands, and the
largest aggregate area of U.S. riparian habitat.
The topography of the area is mostly flat plains,
barrier islands, numerous wetlands, and about
50 important estuarine systems that lie along the
coastal margins. The climate of this eco region is
considered temperate wet to subtropical in the
south, 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 1992 NLCD, the distribution of
land cover in this ecoregion is 39% forested, 30%
planted/cultivated, and 16% wetlands, with the
remaining 15% of the ecoregion comprised of
other types of land cover.
Biological Setting
River habitats in the Coastal Plains ecoregion
have tremendous species richness and the
highest number of endemic species of aquatic
organisms in North America. Abundant fish,
crayfish, mollusk, aquatic insect, and other
species include such unique species as paddlefish,
catostomid suckers, American alligator, and giant
aquatic salamanders; however, it is estimated
that some 18% of the aquatic species in this
ecoregion are threatened or endangered. The
Coastal Plains ecoregion includes the Florida
Everglades, which contains temperate and
tropical plant communities and a rich variety of
bird and wildlife species; however, because it is a
unique aquatic ecosystem, the Everglades is not
represented in the WSA.
Human Influence
Historically, the Coastal Plains ecoregion had
extensive bottomlands that flooded for several
months; these areas are now widely channelized
and confined by levees. Damming, impounding,
and channelization in almost all major rivers
have altered the rate and timing of water flow,
as well as the productivity of riparian habitats.
Pollution from acid mine drainage, urban runoff,
air pollution, sedimentation, and recreation, as
well as the introduction of non-indigenous fishes
and aquatic plants, have also affected riparian
habitats and native aquatic fauna. There are
currently 275 active, 13 proposed, and 77 deleted
EPA Superfund National Priority List sites in the
Coastal Plains ecoregion.
The eco region's economy is varied and includes
many activities. Agriculture in this ecoregion
includes citrus, peanut, sugar cane, tobacco,
cattle, poultry, cotton, corn, rice, vegetable,
and stone fruit production. Industries include
pulp, paper, board, and board wood processing;
aluminum production; salt, sulfur, bauxite,
and phosphate mining; and chemical and
plastics production. The Coastal Plains contain
approximately 40% of U.S. petrochemical
refinery capacity, much of which is located
offshore in the Gulf of Mexico.
This ecoregion also includes many large
coastal cities, which contribute to a population of
approximately 56,168,000, the largest population
of all the WSA ecoregions, representing
approximately 19% of the population of the
United States.
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Summary ofWSA Findings
A total of 83 random sites were sampled during
the summer of 2004 to characterize the condition
of wadeable streams in the Coastal Plains
ecoregion. An overview of the WSA survey results
for this ecoregion is shown in Figure 28. These
results may not be extrapolated to an individual
state or stream within the ecoregion because the
study design was not intended to characterize
stream conditions at these finer scales.
During a series of WSA workshops
conducted to evaluate assessment results,
professional biologists working in the Coastal
Plains ecoregion said that the high prevalence
of human population centers, agriculture,
and industry makes it difficult to find truly
undisturbed streams in this ecoregion; therefore,
the ecoregion's least-disturbed reference sites are
influenced to some degree by human activities.
I Phosphorus
Streambed Sediments
Coastal Plains Ecoregion
72,1 30 miles
Nitrogen
Riparian Disturbance
30%
50%
64%
20 40 60
Percentage Stream Length
For Macroinvertebrate Index:
D Good D Fair CU Poor D Not Assessed
For O/ETaxa Loss:
• >50%TaxaLoss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
d Not Assessed
40 60 f
Percentage Stream Length
• Low
Q Medium
• High
D Not Assessed
20 40 60
Percentage Stream Length
• Good
D Fair
• Poor
D Not Assessed
Figure 28. WSA survey results for the Coastal Plains ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent
the width of the 95% confidence interval around the percent of stream length. Percents may not add up to
100 because of rounding.
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Biological Condition
• The Macroinvertebrate Index reveals that
39% of stream length in the Coastal Plains
ecoregion is in poor condition, 23% is in
fair or intermediate condition, and 36% is in
good condition compared to least-disturbed
reference condition. No data were available to
evaluate 2% of the ecoregion's stream length.
• The O/E Taxa Loss results show that 65% of
stream length in the Coastal Plains ecoregion
has lost 10% or more of the macroinvertebrate
taxa that are expected to occur, and 15% has
lost more than 50% of taxa. These results
also indicate that 32% of stream length has
retained 90% of the groups or classes of
organisms expected to occur based on least-
disturbed reference condition.
Indicators of Stress
Leading indicators of stress in the Coastal
Plains ecoregion include total phosphorus, in-
stream fish habitat, riparian vegetative cover, and
streambed sediments.
• Twenty-nine percent of stream length in the
Coastal Plains ecoregion has high phosphorus
concentrations, 13% has medium phosphorus
concentrations, and 58% has low phosphorus
concentrations based on least-disturbed
reference condition.
• Ten percent of the ecoregion's stream length
has high nitrogen concentrations, 18% has
medium nitrogen concentrations, and 72%
has low nitrogen concentrations based on
least-disturbed reference condition.
Riparian disturbance, or evidence of human
influence in the riparian zone, is at high levels
in 20% of stream length, at medium levels
in 50% of stream length, and at low levels in
30% of stream length.
Salinity is found at high or medium levels in
5% of stream length, with the remaining 95%
of stream length showing low levels for this
indicator.
Streambed sediments are rated poor in 22% of
stream length in the Coastal Plains ecoregion,
fair in 11% of stream length, and good in
64% of stream length based on least-disturbed
reference condition; no data were available to
assess the remaining 3% of stream length.
In-stream fish habitat is in poor condition in
41% of stream length, fair in 13% of stream
length, and good in 46% of stream length,
based on least-disturbed reference condition.
Vegetative cover in the riparian zone along
stream banks is in poor condition for 24%
of stream length, fair condition for 24% of
stream length, and good condition in the
remaining 52% of stream length based on
least-disturbed reference condition.
In this ecoregion, the ANC is low enough to
result in episodic acidification during rainfall
in 6% of stream length. Another 5% of stream
length has naturally lower pH.
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Upper Midwest Ecoregion
Physical Setting
The Upper Midwest ecoregion covers most
of the northern half and southeastern part of
Minnesota, two-thirds of Wisconsin, and almost
all of Michigan. The land area of the Upper
Midwest ecoregion comprises some 160,374 mi2
(5-3% of the United States). 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 rivers in Michigan. 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 stream length represented in the
WSA for the Upper Midwest ecoregion is 36,547
wadeable stream miles. Sandy soils dominate these
waterbodies, with relatively high water quality in
streams supporting cold-water fish communities.
Important waterbodies in this ecoregion include
the Upper Mississippi River system and Lakes
Superior, Michigan, Huron, and Erie.
The glaciated terrain of this ecoregion typically
consists of plains with some hill formations.
Numerous lakes, rivers, and wetlands predominate
in most areas. The climate is characterized by
cold winters and relatively short, warm summers,
with mean annual temperatures ranging from
34 to 54 °F and annual precipitation in the
20- to 47-inch range. Much of the land in this
ecoregion is covered by national and state forests,
Raisin River, Ml, in the Upper Midwest
ecoregion (Photo courtesy of the Great Lakes
Environmental Center).
and federal lands account for 15-5% of the area
(roughly 25,000 mi2). Based on satellite images in
the 1992 NLCD, the distribution of land cover
in this ecoregion is 40% forested, 34% planted/
cultivated, and 17% wetlands, with the remaining
9% of the ecoregion comprised of other types of
land cover.
Biological Setting
Vegetative cover for the Upper Midwest
ecoregion is mixed boreal woodland, mixed
oak-hickory associations, and conifers, as well as
bog and moss barrens. The Great Lakes aquatic
ecosystems are subject to increasing intrusion by
invasive animal and plant species introduced by
ocean shipping. These species include the zebra
mussel, the round goby, the river ruffe, the spiny
water flea, and Eurasian watermilfoil.
Human Influence
The Upper Great Lakes portion of the Upper
Midwest ecoregion was entirely forested in
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
pre-colonial times. Virtually all of the virgin forest
was cleared in the 19th and early 20th centuries,
and streams and rivers were greatly affected by
the logging industry. The upper Mississippi River
portion of the Upper Midwest ecoregion was also
heavily influenced by logging and agriculture.
Major manufacturing, chemical, steel, and
power production (e.g., coal, nuclear, oil) occur in
the large metropolitan areas found in the Upper
Midwest ecoregion. Other key economic activities
are forestry, mining, and tourism. Agriculture
includes dairy production, grain crops in the
western areas, fruit production around the Great
Lakes, and hay and cattle farming throughout
the ecoregion. Pulp, paper, and board wood
processing are prevalent throughout the northern
parts of the ecoregion. The area includes the
shipping ports at Duluth, MN, and Superior, WI,
as well as cities like Marquette, MI, and Ribbing,
MN, which were built up along with the mining
industry. The Upper Peninsula of Michigan lies
entirely within the Upper Midwest ecoregion,
as does Minnesota's Mesabi Range, the largest
U.S. iron ore deposit. This area is subject to the
environmental effects of mining operations. There
are currently 112 active, 1 proposed, and 12
deleted EPA Superfund National Priority List sites
in this ecoregion.
The approximate population of this area is
15,854,000, representing approximately 5% of
the population of the United States.
Summary ofWSA Findings
A total of 56 random sites were sampled in the
Upper Midwest ecoregion during the summer of
2004 to characterize the condition of its wadeable
streams. An overview of the WSA survey results
for the Upper Midwest ecoregion is shown in
Figure 29- These results may not be extrapolated
to an individual state or stream within the
ecoregion because the study design was not
intended to characterize stream conditions at
these finer scales.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Upper Midwest
ecoregion said that some of the ecoregion's least-
disturbed streams that serve as a benchmark for
reference condition are influenced by some form
of human activity or land use; however, most
of the least-disturbed reference sites are streams
in relatively undisturbed areas in the northern
portion of the ecoregion.
Biological Condition
• The Macroinvertebrate Index reveals that
39% of stream length in the Upper Midwest
ecoregion is in poor condition, 31% is in
fair condition, and 28% is in good condition
based on least-disturbed reference condition.
• The O/E Taxa Loss results show that 54% of
stream length in the Upper Midwest ecoregion
has lost 10% or more of the macroinvertebrate
taxa that are expected to occur, and 5% has
lost more than 50% of taxa. These results
also indicate that 45% of stream length has
retained at least 90% of the groups or classes
of organisms expected to occur based on least-
disturbed reference condition.
Indicators of Stress
Leading indicators of stress in the Upper
Midwest ecoregion include total phosphorus, total
nitrogen, streambed sediments, and in-stream fish
habitat.
• Thirty-eight percent of stream length in
the Upper Midwest ecoregion has high
phosphorus concentrations, 18% has medium
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
Phosphorus
Upper Midwest Ecoregion
36,547 miles
| Macroinvertebrate Index
I 28%
131%
39%
I O/E Taxa Loss
31% 18%
42%
20 40 60 80
Percentage Stream Length
For Macroinvertebrate Index:
D Good n Fair D Poor Cl Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
L~U Not Assessed
40 60 f
Percentage Stream Length
77%
Streambed Sediments
137%
I 11%
In-stream Fish Habitat
i=|—I 14%
I 69%
I 17%
Riparian Vegetative Cover
H
38%
JjH 4%
13%
Acidification
I
• Low
D Medium
• High
D Not Assessed
100 0 20 40 60 8
Percentage Stream Length
• Good
D Fair
• Poor
D Not Assessed
Figure 29. WSA survey results for the Upper Midwest ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent the
width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
phosphorus concentrations, and 42% has low
phosphorus concentrations based on least-
disturbed reference condition.
Twenty-one percent of the ecoregion's stream
length has high nitrogen concentrations,
30% of stream length has medium nitrogen
concentrations, and 48% of stream length has
low nitrogen concentrations based on least-
disturbed reference condition.
Riparian disturbance, or evidence of human
influence in the riparian zone, is at high levels
in 6% of stream length, at medium levels in
45% of stream length, and at low levels in
49% of stream length.
Salinity is found at medium levels in 22%
of stream length and at low levels in 77% of
stream length. None of the steam length of the
Upper Midwest ecoregion showed high levels
for this indicator.
Streambed sediments are rated poor in 50% of
stream length, fair in 11%, and good in 37%;
data for this indicator were not available for
2% of stream length.
In-stream fish habitat is in poor condition in
17% of stream length, fair in 69% of stream
length, and good in 14% of stream length
based on least-disturbed reference condition.
Vegetative cover in the riparian zone along
stream banks is in poor condition in 13% of
stream length, fair condition in 38% of stream
length, and in good condition in 44% of
stream length.
The effects of acidification are not noted for
the Upper Midwest ecoregion.
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Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Temperate Plains Ecoregion
Physical Setting
The Temperate Plains ecoregion includes the
open farmlands of Iowa; the eastern Dakotas;
western Minnesota; portions of Missouri, Kansas,
and Nebraska; and the flat farmlands of western
Ohio, central Indiana, Illinois, and southeastern
Wisconsin. The area of this ecoregion covers some
342,200 mi2 (11.4% of the United States), with
approximately 7,900 mi2 (2.3%) of land under
federal ownership. The ecoregion's terrain consists
of smooth plains and numerous small lakes and
wetlands. The climate is temperate, with fairly
cold winters; hot, humid summers; and mean
temperatures ranging from 36 to 55 °E Annual
precipitation in the Temperate Plains ecoregion
ranges from 16 to 43 inches.
Many of the rivers in this ecoregion drain
into the Upper Mississippi and Ohio regional
watersheds, and a few systems empty into the
Great Lakes watershed near Toledo, OH; Saginaw,
MI; Detroit, MI; and southeastern Wisconsin.
Rivers are either supplied by snowmelt or
groundwater. Rivers in the tall grass prairie start
from prairie potholes and springs and are likely
to be ephemeral (flowing for a short time after
snowmelt or rainfall). The prairie rivers carry
large volumes of fine sediments and tend to be
turbid, wide, and shallow. The total stream length
represented in the WSA for the Temperate Plains
ecoregion is 100,879 wadeable stream miles.
Based on satellite images in the 1992 NLCD, the
distribution of land cover in this ecoregion is 9%
forested and 76% planted/cultivated, with the
remaining 15% of the ecoregion comprised of
other types of land cover.
Grey Horse Creek, OK, in the Temperate Plains
ecoregion (Photo courtesy of Monty Porter).
Biological Setting
Vegetation for the Temperate Plains ecoregion
consists primarily of oak, hickory, elm, ash, beech,
and maple, with increasing amounts of prairie
grasses to the west. Rivers have rich fish fauna
with many species, including minnows, darters,
killifishes, catfishes, suckers, sunfishes, and black
bass. Few species are endemic to the ecoregion.
Human Influence
Pre-settlement vegetation of the area was
prairie grass and aspen parkland, but is now
comprised of about 75% arable cultivated lands.
This ecoregion is rich in agricultural production,
including field crops such as corn, wheat,
alfalfa, soybeans, flaxseed, and rye, along with
vegetable crops such as peanuts and tomatoes.
Hog and cattle production and processing are
also prevalent. Crops and grazing have reduced
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Chapter 3 \ Wadeable Streams Assessment Ecoregion Results
natural riparian vegetation cover, increased
sediment yield, and introduced pesticides and
herbicides into the watershed. Conservation
tillage — a reduced-cultivation method — has
been implemented in about 50% of crop fields
in the Maumee River Basin and in northwestern
Ohio tributaries draining to Lake Erie. USGS
findings from 1993—1998 in these rivers
showed significant decreases in the amounts of
suspended sediment. Rivers in the Temperate
Plains ecoregion also tend to have high nitrogen
concentrations due to nutrients from agriculture
and from fertilizer applied to lawns and golf
courses in urban areas. In Illinois, where land is
intensively developed through urbanization and
agriculture, more than 25% of all sizable streams
have been channelized, and almost every stream
in the state has at least one dam.
Coal mining, petroleum and natural gas
production, and zinc and lead mining occur
across the Temperate Plains ecoregion. There are
very active areas of manufacturing, steel produc-
tion, and chemical production in the ecoregion's
urban centers, with especially high concentrations
near Detroit, MI, and the industrial belt from
Gary, IN, to Chicago, IL, and Milwaukee, WI.
Industrial activities in these large urban centers
have contributed sewage, toxic compounds, and
silt to river systems. Heavy metals,
organochlorines, and PCBs are especially
prevalent and persistent river contaminants found
in industrial areas; however, many rivers have
improved from their worst state in the 1960s.
There are currently 133 active, 17 proposed, and
44 deleted EPA Superfund National Priority List
sites in the Temperate Plains ecoregion.
The approximate population of this ecoregion
is 38,399,000, representing approximately 13%
of the U.S. population.
Summary ofWSA Findings
A total of 132 random sites were sampled
during the summer of 2004 to characterize the
condition of wadeable streams throughout the
Temperate Plains ecoregion. An overview of the
WSA survey results for the Temperate Plains
ecoregion is shown in Figure 30. These results
may not be extrapolated to an individual state or
stream within the ecoregion because the study
design was not intended to characterize stream
conditions at these finer scales.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Temperate Plains
ecoregion said that it is hard to find high-quality
reference sites in the ecoregion because even
the least-disturbed streams are influenced by a
long history of land use. Extensive agriculture
and development have influenced virtually all
waterbodies in this ecoregion.
Biological Condition
• The Macroinvertebrate Index reveals that
37% of stream length in the Temperate Plains
ecoregion is in poor condition, 36% is in
fair condition, and 26% is in good condition
compared to least-disturbed reference
condition.
• The O/E Taxa Loss results show that 39%
of stream length in the Temperate Plains
ecoregion has lost 10% or more of the
macroinvertebrate taxa that are expected to
occur, and 10% has lost more than 50% of
taxa. These results also indicate that 58% of
stream length has retained 90% of the groups
or classes of organisms expected to occur based
on least-disturbed reference condition.
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Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Streambed Sediments
67%
Temperate Plains Ecoregion
100,879 miles
j O/E Taxa Loss
17% 12%
20 40 60
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
d Not Assessed
40 60
Percentage Stream Length
• Low
n Medium
• High
D Not Assessed
100 0 20 40 60
Percentage Stream Length
| Good
D Fair
• Poor
CU Not Assessed
Figure 30. WSA survey results for the Temperate Plains ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent the
width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
Indicators of Stress
Leading indicators of stress in the Temperate
Plains ecoregion include total nitrogen, riparian
disturbance, in-stream fish habitat, and riparian
vegetative cover.
• Approximately 12% of stream length in the
Temperate Plains ecoregion has high
phosphorus concentrations, 13% has medium
phosphorus concentrations, and 74% has low
phosphorus concentrations based on least-
disturbed reference condition.
• Approximately 41% of the ecoregion's stream
length has high nitrogen concentrations, 17%
has medium nitrogen concentrations, and
41% has low nitrogen concentrations based on
least-disturbed reference condition.
Riparian disturbance for this ecoregion is at
high levels in approximately 38% of stream
length, at medium levels in 58% of stream
length, and at low levels in 3% of stream
length.
Salinity is found at high levels in 2% of stream
length, at medium levels in 13% of stream
length, and at low levels in 84% of stream
length.
Excess streambed sediments affect streams in
the Temperate Plains ecoregion to a lesser
extent than other physical stressors. Streambed
sediments are rated poor in 20% of stream
length in this ecoregion, fair in 12%, and good
in 67% based on least-disturbed reference
condition.
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
• In-stream fish habitat is in poor condition in
39% of stream length, fair in 19% of stream
length, and good in 41% of stream length
based on least-disturbed reference condition.
• Vegetative cover in the riparian zone along
stream banks is in poor condition for 26%
of stream length, fair condition for 17% of
stream length, and good condition for 53% of
stream length.
• The effects of acidification are not noted for
the Temperate Plains ecoregion.
Southern Plains Ecoregion
Physical Setting
The Southern Plains ecoregion covers
approximately 405,000 mi2 (13-5% of the
United States) and includes central and northern
Texas; most of western Kansas and Oklahoma;
and portions of Nebraska, Colorado, and New
Mexico. The terrain is a mix of smooth and
irregular plains interspersed with tablelands
and low hills. The Arkansas, Platte, White,
Red, and Rio Grande rivers flow through this
ecoregion, and most of the great Ogallala aquifer
lies underneath this ecoregion. The total stream
length represented in the WSA for the Southern
Plains ecoregion is 19,263 wadeable stream miles.
Most of the land use is arable and arable
with grazing, with desert or semi-arid grazing
land in the south. Based on satellite images
in the 1992 NLCD, the distribution of land
cover in this ecoregion is 45% grassland, 32%
planted/cultivated, and 14% shrubland, with
the remaining 9% of the ecoregion comprised of
other types of land cover. Federal land ownership
in this ecoregion totals about 11,980 mi2 or
approximately 3% of the total, the lowest share
of all WSA aggregate ecoregions. The climate is
dry temperate, with the mean annual temperature
ranging from 45 to 79 °E Annual precipitation
for the ecoregion is between 10 and 30 inches.
Biological Setting
Vegetative cover in the northern portion of
this ecoregion is mainly short prairie grasses such
as buffalo grass, while in the southern portion,
grasslands with mesquite, juniper, and oak woody
vegetation are common. Coastal vegetation in the
southern Plains ecoregion is typically more salt-
tolerant in nature.
Commission Creek, OK, in the Southern Plains
ecoregion (Photo courtesy of Monty Porter).
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Human Influence
The Great Prairie grasslands, which once
covered much of the Southern Plains ecoregion,
are the most altered and endangered large
ecosystem in the United States. About 90% of
the original tall grass prairie was replaced by
other vegetation or land uses. Agriculture is an
important economic activity in this ecoregion and
includes sorghum, wheat, corn, sunflower, bean,
and cotton production. Livestock production
and processing is prevalent, especially goats,
sheep, and cattle. The ecoregion contains a
sizable portion of U.S. petroleum and natural
gas production in Oklahoma, Kansas, and Texas.
Electricity in this ecoregion is generated almost
exclusively with gas-fired power plants. Some
uranium and zinc mining is found in Oklahoma
and the Texas panhandle. There are currently
39 active, 5 proposed, and 14 deleted EPA
Superfund National Priority List sites in this
ecoregion.
The approximate population in this ecoregion
is 18,222,000, representing roughly 6% of the
population of the United States.
Summary ofWSA Findings
A total of 49 random sites were sampled during
the summer of 2004 to characterize the condition
of wadeable streams throughout the Southern
Plains ecoregion. An overview of the WSA survey
results for the ecoregion is shown in Figure 31.
These results may not be extrapolated to an
individual state or stream within the ecoregion
because the study design was not intended to
characterize stream conditions at these finer scales.
/TClT?^ rtiO
\\Lr^^^m
Southern Plains Ecoregion
19 263 miles
1 T 1 20%
1 1 54%
O/E Taxa Loss
) 20 40 60 80 100 (
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 1 0% Taxa Loss
D Not Assessed
Phosphorus
— | — 1 7%
Nitrogen
1 1 1 34%
1 F 1 30%
Riparian Disturbance
1 1 1 14%
1 1 1 67%
1 | 1 19%
Salinity
20 40 60 80 100
Percentage Stream Length
• Low
n Medium
• High
D Not Assessed
Streambed Sediments
1 1 1 18%
1 1 1 30%
In-stream Fish Habitat
1 135%
1 1 1 23%
Riparian Vegetative Cover
1 1 1 24%
1 1 140%
1 1 1 36%
Acidification
1
3 20 40 60 80 100
Percentage Stream Length
H Good
D Fair
• Poor
D Not Assessed
Figure 3 I. WSA survey results for the Southern Plains ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent the
width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
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Chapter 3 \ Wadeable Streams Assessment Ecoregion Results
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Southern Plains
ecoregion said that no undisturbed streams
remain in the ecoregion. The least-disturbed
streams are those that retain natural configuration
and have riparian buffer zones.
Biological Condition
• The Macroinvertebrate Index reveals that
54% of stream length in the Southern Plains
ecoregion is in poor condition, 20% is in
fair condition, and 22% is in good condition
compared to least-disturbed reference
condition. There are no data for the remaining
4% of stream length.
• The O/E Taxa Loss results show that 50% of
stream length in the Southern Plains ecoregion
has lost 10% or more of the macroinvertebrate
taxa expected to occur, and 15% has lost more
than 50% of taxa. These results also indicate
that 42% of the ecoregion's stream length
has retained 90% of the groups or classes of
organisms expected to occur based on least-
disturbed reference condition.
Indicators of Stress
The most widespread indicators of stress
in the Southern Plains ecoregion include total
phosphorus, total nitrogen, in-stream fish habitat,
and riparian vegetative cover.
• Forty-eight percent of stream length in
the Southern Plains ecoregion has high
phosphorus concentrations, 7% has medium
phosphorus concentrations, and 45% has low
phosphorus concentrations based on least-
disturbed reference condition.
Approximately 36% of the ecoregion's stream
length has high nitrogen concentrations, 30%
has medium nitrogen concentrations, and
34% has low nitrogen concentrations based on
least-disturbed reference condition.
Riparian disturbance in this ecoregion is at
high levels in 19% of stream length. The
majority of stream length (67%) has medium
levels of riparian disturbance, and only 14%
has low levels for this indicator.
Salinity is found at high levels in 22% of
stream length, at medium levels in 21% of
stream length, and at low levels in 57% of
stream length.
Streambed sediments are rated poor in 30% of
stream length, fair in 18%, and good in 52%
based on least-disturbed reference condition.
In-stream fish habitat is in poor condition in
42% of stream length, fair in 23% of stream
length, and good in 35% of stream length
based on least-disturbed reference condition.
Vegetative cover in the riparian zone along
stream banks is in poor condition for 36% of
stream length, in fair condition for 40% of
stream length, and good condition for 24% of
stream length.
The effects of acidification are not noted for
the Southern Plains ecoregion.
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Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Northern Plains Ecoregion
Physical Setting
The Northern Plains ecoregion covers approxi-
mately 205,084 mi2 (6.8% of the United States),
including the western Dakotas, Montana east of
the Rocky Mountains, northeast Wyoming, and
a small section of northern Nebraska. Federal
lands account for 52,660 mi2 or a relatively large
(25-7%) share of the total area. The Great Prairie
grasslands were also an important feature of this
ecoregion, but about 90% of these grasslands have
been replaced by other vegetation or land use. The
ecoregion's terrain is irregular plains interspersed
with tablelands and low hills. This ecoregion is
the heart of the Missouri River system and is
almost exclusively within the Missouri River's
regional watershed. The total stream length
represented in the WSA for the Northern Plains
ecoregion is 13,445 wadeable stream miles.
Land use is arable with grazing or semi-
arid grazing. Based on satellite images in the
1992 NLCD, the distribution of land cover
in this ecoregion is 56% grassland and 30%
planted/cultivated, with the remaining 14% of
the ecoregion comprised of other types of land
cover. Significant wetlands are also found in the
Nebraska Sandhills area. The climate is dry and
continental, 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. It is also subject
to periodic, intense droughts and frosts.
Biological Setting
The predominant vegetative cover for the
Northern Plains ecoregion was formerly native
short prairie grasses, such as wheat grass and
porcupine grass, but now cropland is much more
prevalent.
Wolf Creek, McCook County, SD, in the Northern Plains ecoregion
(Photo courtesy of Dynamac Corp).
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Human Influence
Human economic activity is primarily
agriculture, including cattle and sheep grazing,
as well as the growing of wheat, barley, and
sugar beets. Coal mining occurs in the North
Dakota, Montana, and Wyoming portions of
the ecoregion. Petroleum and gas production has
grown considerably in the Cut Bank region in
north-central Montana. There are several large
Indian reservations in this ecoregion, including
the Pine Ridge, Standing Rock, and Cheyenne
reservations in South Dakota and the Blackfeet,
Crow, and Fort Peck reservations in Montana.
There are currently four active and one proposed
EPA Superfund National Priority List sites in this
ecoregion.
Phosphorus
Northern Plains Ecoregion
13,445 miles
Macroinvertebrate Index
( 30%
50%
The approximate population of this ecoregion
is relatively small at 1,066,000, or 0.4% of the
population of the United States.
Summary ofWSA Findings
A total of 98 random sites were sampled during
the summers of 2000—2004 to characterize the
condition of wadeable streams throughout the
Northern Plains ecoregion. An overview of the
WSA survey results for the ecoregion is shown in
Figure 32. These results may not be extrapolated
to an individual state or stream within the
ecoregion because the study design was not
intended to characterize stream conditions at
these finer scales.
54%
0 20 40 60 80
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
D Not Assessed
Streambed Sediments
50%
33%
In-stream Fish Habitat
34%
I 45%
Riparian Vegetative Cover
28%
22%
H 50%
Acidification
20 40 60
Percentage Stream Length
• Low
D Medium
• High
D Not Assessed
100 0 20 40 60 E
Percentage Stream Length
• Good
D Fair
• Poor
D Not Assessed
Figure 32. WSA survey results for the Northern Plains ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent the
width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
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During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Northern Plains
ecoregion said that although the ecoregion
has relatively few undisturbed streams, the
majority are in areas of low-level agriculture and
pastureland.
Biological Condition
• The Macroinvertebrate Index reveals that
50% of stream length in the Northern Plains
ecoregion is in poor condition, 13% is in
fair condition, and 30% is in good condition
compared to least-disturbed reference
condition. There are no data for the remaining
7% of stream length.
• The O/E Taxa Loss results show that 34% of
stream length has lost 10% or more of the
macroinvertebrate taxa expected to occur,
and 12% has lost more than 50% of taxa.
These results also indicate that 60% of the
ecoregion's stream length has retained 90% of
the groups or classes of organisms expected
to occur based on least-disturbed reference
condition.
Indicators of Stress
The most widespread indicators of stress in
the Northern Plains ecoregion include riparian
vegetative cover, in-stream fish habitat, riparian
disturbance, and salinity.
• Thirty-three percent of stream length in
the Northern Plains ecoregion has high
phosphorus concentrations, 13% has medium
phosphorus concentrations, and 54% has low
phosphorus concentrations based on least-
disturbed reference condition.
Eighteen percent of the ecoregion's stream
length has high nitrogen concentrations, 21%
has medium nitrogen concentrations, and
60% has low nitrogen concentrations based on
least-disturbed reference condition.
Riparian disturbance in the Northern Plains
ecoregion is at high levels in 31% of stream
length, at medium levels in 66% of stream
length, and at low levels in 3% of stream
length.
Salinity is a significant stressor in the Northern
Plains. Salinity is high in 38% of stream
length, medium in 22% of stream length, and
low in 40% of stream length.
Streambed sediments are rated poor in 33%
of stream length in the Northern Plains
ecoregion, fair in 14%, and good in 50%
based on least-disturbed reference condition;
data for this indicator were unavailable for 3%
of stream length.
In-stream fish habitat is in poor condition in
45% of stream length, fair in 21% of stream
length, and good in 34% of stream length
based on least-disturbed reference condition.
Vegetative cover in the riparian zone along
stream banks is in poor condition for 50% of
stream length, in fair condition for 22% of
stream length, and in good condition for 28%
of stream length.
The effects of acidification are not noted for
the Northern Plains ecoregion.
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
Western Mountains
Ecoregion
Physical Setting
The Western Mountains ecoregion includes
the Cascade, Sierra Nevada, and Pacific Coast
ranges in the coastal states; the Gila Mountains
in the southwestern states; and the Bitteroot
and Rocky mountains in the northern and
central mountain states. This ecoregion covers
approximately 397,832 mi2, with about 297,900
mi2 or 74.8% classified as federal land — the
highest proportion of federal property among all
the 9 aggregate ecoregions. The terrain of this
area is characterized by extensive mountains and
plateaus separated by wide valleys and lowlands.
Coastal mountains are transected by numerous
fjords and glacial valleys, are bordered by coastal
plains, and include important estuaries along
the ocean margin. Soils are mainly nutrient-poor
forest soils. Based on satellite images in the 1992
NLCD, the distribution of land cover in this
ecoregion is 59% forested, 19% shrubland, and
13% grassland, with the remaining 9% of the
ecoregion comprised of other types of land cover.
The headwaters and upper reaches of the
Columbia, Sacramento, Missouri, and Colorado
river systems all occur in this ecoregion. Smaller
rivers share many characteristics, starting as steep
mountain streams with staircase-like channels
and 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 stream length represented in
the WSA for the Western Mountains ecoregion is
126,436 wadeable stream miles.
Unnamed tributary to Lake Creek, Chelan County,
WA, in the Western Mountains ecoregion (Photo
courtesy of the Washington Department of Ecology).
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.
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
Biological Setting
Rivers in this ecoregion drain dense forested
catchments and contain large amounts of woody
debris that provide habitat diversity and stability.
Rivers reaching the Pacific Ocean historically had
large runs of salmon and trout, including pink,
chum, sockeye, coho, and chinook salmon, as well
as cutthroat and steelhead trout. Many of these
anadromous fish populations have been reduced
since the time of European settlement due to the
effects of overfishing, introduced species, flow
regulations, and dams. Spawning habitats in
stream pools have been drastically reduced due to
increased sediments from logging, mining, and
other land use changes.
Human Influence
Deforestation and urbanization continue to
alter stream habitats in the mountainous west.
The Western Mountains riparian ecosystems first
encountered pressure from grazing and mining
from the mid-1800s to about 1910 and then from
the logging roads and fire management practices
that occur to the present day.
Placer mining, which disrupts stream sediment
habitats, was once widespread in the Western
Mountains ecoregion. Particularly damaging
in mountainous areas was the introduction of
mercury, which was used extensively in placer
mining for gold. Toxic contaminants from
mining also include arsenic, antimony, copper,
chromium, cadmium, nickel, lead, selenium,
silver, and zinc. In addition to mining, other
activities such as logging, grazing, channelization,
dams, and diversions in the Sierra Nevada
area also significantly impacted rivers and
streams. Introduced fish provided further stress,
with several native fish species threatened or
endangered.
The principal economic activities in this
ecoregion are high-tech manufacturing, wood
processing, international shipping, U.S. naval
operations, commercial fishing, tourism, grazing,
and timber harvesting. Hydroelectric power
generation is prevalent in the Pacific Northwest
area and California. Bauxite mining also occurs in
the Pacific Northwest portions of the ecoregion.
There are currently 74 active, 7 proposed, and
22 deleted EPA Superfund National Priority List
sites in the Western Mountains ecoregion.
The approximate population in the Western
Mountains ecoregion is 9,742,192, representing
approximately 3% of the population of the
United States.
Summary ofWSA Findings
A total of 529 random sites were sampled
during the summers of 2000—2004 to characterize
the condition of wadeable streams throughout
the Western Mountains ecoregion. This ecoregion
had the greatest number of sample sites because
all the western states enhanced the scale of the
national survey by including additional random
sites. Although there are enough sites to develop
state-scale estimates of condition, this report did
not produce those estimates. The individual states
are analyzing the survey results in the context of
their own water quality standards and assessment
methodologies. An overview of the WSA survey
results for the Western Mountains ecoregion is
shown in Figure 33. These results may not be
extrapolated to an individual state or stream
within the ecoregion.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Western Mountains
ecoregion said that many least-disturbed streams
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
in the ecoregion are of relatively high quality;
however, some of these streams have mining and
logging impacts, leading to reference conditions
of varying degrees of quality.
Biological Condition
• The Macroinvertebrate Index reveals that 25%
of stream length in the Western Mountains
ecoregion is in poor condition, 28% is in
fair condition, and 46% is in good condition
compared to least-disturbed reference
condition. There are no data for about 1% of
stream length.
• The O/E Taxa Loss results show that 33% of
stream length has lost 10% or more of the
macroinvertebrate taxa expected to occur, and
5% has lost more than 50% of taxa. These
results indicate that 63% of stream length
has retained 90% of the groups or classes of
organisms expected to occur based on least-
disturbed reference condition.
Indicators of Stress
The most widespread indicators of stress in
the Western Mountains ecoregion include total
nitrogen, total phosphorus, riparian disturbance,
and streambed sediments.
• Sixteen percent of stream length in the
Western Mountains ecoregion has high
phosphorus concentrations, 25% has medium
phosphorus concentrations, and 59% has low
phosphorus concentrations based on least-
disturbed reference condition.
Western Mountains Ecoregion
126,436 miles
20 40 60
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor D Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
d Not Assessed
40 60
Percentage Stream Length
I Low
D Medium
• High
D Not Assessed
40 60
Percentage Stream Length
H Good
D Fair
• Poor
D Not Assessed
Figure 33. WSA survey results for the Western Mountains ecoregion (U.S. EPA/WSA). Bars show the
percentage of stream length within a condition class for a given indicator. Lines with brackets represent the
width of the 95% confidence interval around the percent of stream length. Percents may not add up to 100
because of rounding.
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Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Seventeen percent of the ecoregion's stream
length has high nitrogen concentrations, 28%
has medium nitrogen concentrations, and
54% has low nitrogen concentrations based on
least-disturbed reference condition.
Riparian disturbance, or evidence of human
influence in the riparian zone, is at high levels
in 14% of stream length, at medium levels
in 47% of stream length, and at low levels in
39% of stream length.
Levels of salinity are medium in 3% of stream
length and low in 97% of stream length.
None of the stream length for the Western
Mountains ecoregion had high levels of
salinity.
Streambed sediments are rated poor in 14% of
stream length in this ecoregion, fair in 22%,
and good in the remaining 63%.
In-stream fish habitat is in poor condition in
9% of stream length, fair in 20% of stream
length, and good in 70% of stream length.
Vegetative cover in the riparian zone along
stream banks is in poor condition for 9% of
stream length, in fair condition for 32% of
stream length, and in good condition for 59%
of steam length.
Acidification is rated poor in nearly 1% of
stream length and good in 99% of stream
length.
Fishing and tourism are important economic activities in the Western Mountains
ecoregion (Photo courtesy of Ron Nichols, U.S. Department of Agriculture National
Resources Conservation Service).
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
Xeric Ecoregion
Physical Setting
The Xeric ecoregion covers the largest area of
all WSA aggregate ecoregions and includes the
most total land under federal ownership. This
ecoregion covers portions of eleven western states
and all of Nevada for a total of about 636,583
mi2 (21.2% of the United States). Some 453,000
mi2 or 71.2% of the land is classified as federal
lands, including large tracts of public land,
such as the Grand Canyon National Park, Big
Bend National Park, and the Hanford Nuclear
Reservation. Tribal lands include the Navajo,
Hopi, and Yakima reservations. Based on satellite
images in the 1992 NLCD, the distribution of
land cover in this ecoregion is 61% shrubland and
15% grassland, with the remaining 24% of the
ecoregion comprised of other types of land cover.
The Xeric ecoregion is comprised 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. All of the non-mountainous
area of California falls in the Xeric ecoregion and
is distinguished by a mild Mediterranean climate,
agriculturally productive valleys, and large
metropolitan areas.
This ecoregion's 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,
West Clear Creek,Yavapai County.AZ, in the Xeric ecoregion
(Photo courtesy of the Arizona Game and Fish Department/USGS).
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
and peak in early summer. Small rivers in this
ecoregion are mostly ephemeral. Most rivers are
turbid because they drain erodable sedimentary
rock in a dry climate, where sudden rains flush
sediments down small rivers. Rivers are often
subject to rapid change due to flash floods and
debris flows. In southern areas, dry conditions
and water withdrawals produce internal drainages
that end in saline lakes or desert basins without
reaching the ocean (e.g., Utah's Great Salt Lake).
The total stream length represented in the WSA
for the Xeric ecoregion is 25,989 wadeable stream
miles.
The Xeric ecoregion's climate 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. The dry weather in the Sonoran, Mojave,
and Chihuahuan deserts is created by the rain
shadows cast by the mountains to the west and is
punctuated by heavy, isolated episodic rainfalls.
Biological Setting
Rivers create a riparian habitat oasis for plants
and animals in the dry Xeric ecoregion areas.
Many fish are endemic, are restricted to the
Colorado River basin, and have evolved to cope
with warm, turbid waters. Examples include
the humpback chub, bonytail chub, Colorado
pikeminnow, roundtail chub, razorback sucker,
Colorado squawfish, Pyramid Lake cui-ui, and
Lahontan cutthroat trout. Most of these fish
are threatened or endangered as a result of flow
regulations from dams, water withdrawals, and
introduced non-native species. Threatened species
offish in desert areas include the Sonora chub
and beautiful shiner.
Human Influence
Impacts to the Xeric ecoregion riparian
habitats have been heavy in the past 250 years
because of water impoundment and diversion;
groundwater and surface water extraction; grazing
and agriculture; and mining, road development,
and heavy recreational demand. Both the least-
altered and most-altered pre-settlement natural
vegetation types are found in this ecoregion.
Riparian habitats in this ecoregion have also
been widely impacted by invasive species and
contamination from agriculture and urban runoff.
Big rivers in the southwestern canyon regions
were altered due to large dam construction
and large-scale water-removal projects for cities
and agriculture, with attendant small streams
that experience cycles of draining and filling in
response to grazing, groundwater withdrawal,
and urbanization. In many desert areas,
dissolved solids such as boron, molybdenum,
and organophosphates leach from desert soils
into irrigation waters. Almost every tributary in
California's Central Valley has been altered by
canals, drains, and other waterways.
Principal economic activities include recreation
and tourism; mining; agriculture; grazing;
manufacturing and service industries; agriculture
and food processing; aerospace and defense
industries; and automotive-related industries.
Petroleum production is prevalent in California.
Agriculture includes production of a wide range
of crops, from wheat, dry peas, lentils, and
potatoes to grapes and cotton. Large agricultural
irrigation projects include the Salt and Gila valleys
and the Imperial and Central valleys in California.
There are currently 139 active, 6 proposed, and
24 deleted EPA Superfund National Priority List
sites in this ecoregion.
. /f!
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Chapter 3 Wadeable Streams Assessment Ecoregion Results
The total population in the Xeric ecoregion
is the third largest of all WSA ecoregions at
approximately 46,800,000 people, or 16% of the
population of the United States.
Summary of WSA Findings
A total of 176 random sites were sampled
during the summers of 2000—2004 to characterize
the condition of wadeable streams throughout the
Xeric eco region. An overview of the WSA survey
results for the Xeric eco region is shown in Figure
34. These results may not be extrapolated to an
individual state or stream within the eco region.
During a series of WSA workshops conducted
to evaluate assessment results, professional
biologists working in the Xeric eco region said that
many of the perennial, least-disturbed streams in
this ecoregion have been influenced by past and
current human activities.
Biological Condition
• The Macroinvertebrate Index reveals that 39%
of stream length in the Xeric ecoregion is in
poor condition compared to least-disturbed
reference condition, 15% is in fair condition,
and 42% is in good condition. There are no
data for about 4% of stream length.
• The O/E Taxa Loss results show that 60% of
stream length in the Xeric ecoregion has lost
10% or more of the macroinvertebrate taxa
expected to occur and 15% has lost more than
50% of taxa. These results also indicate that
34% of stream length has retained 90% of the
groups or classes of organisms expected to occur
based on least-disturbed reference condition.
Streambed Sediments
60%
17%
32%
47%
Xeric Ecoregion
25,989 miles
20 40 60
Percentage Stream Length
For Macroinvertebrate Index:
• Good D Fair • Poor EH Not Assessed
For O/E Taxa Loss:
• > 50% Taxa Loss D 20-50% Taxa Loss
D 10-20% Taxa Loss •< 10% Taxa Loss
L"H Not Assessed
40 60 f
Percentage Stream Length
| Low
D Medium
• High
CU Not Assessed
100 0 20 40 60 80 100
Percentage Stream Length
• Good
D Fair
• Poor
D Not Assessed
Figure 34. WSA survey results for the Xeric ecoregion (U.S. EPA/WSA). Bars show the percentage of
stream length within a condition class for a given indicator. Lines with brackets represent the width of the 95%
confidence interval around the percent of stream length. Percents may not add up to 100 because of rounding.
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Chapter 3 Wadeable Streams Assessment Ecoreg/on Results
Indicators of Stress
The leading indicators of stress in the Xeric
ecoregion include riparian disturbance, total
nitrogen, streambed sediments, and in-stream fish
habitat.
• Twenty-nine percent of stream length in
the Xeric ecoregion has high phosphorus
concentrations, 10% has medium phosphorus
concentrations, and 60% has low phosphorus
concentrations based on least-disturbed
reference condition.
• Nitrogen is the leading chemical stressor in the
Xeric region. Approximately 36% of stream
length has high nitrogen concentrations, 26%
has medium nitrogen concentrations, and
37% has low nitrogen concentrations based on
least-disturbed reference condition.
• Riparian disturbance, or evidence of human
influence in the riparian zone, is the leading
physical stressor for the Xeric ecoregion.
Riparian disturbance in this ecoregion is
at high levels in 44% of stream length, at
medium levels in 40% of stream length, and at
low levels in 15% of stream length.
Salinity is rated high in 13% of stream length
and medium in 29%, with 56% of stream
length showing low levels of this indicator.
Data for this indicator were unavailable for
approximately 1% of stream length.
Streambed sediments are rated poor in 32%
of stream length in the Xeric ecoregion, fair in
17%, and good in 48%; data on this indicator
were unavailable for 3% of stream length.
In-stream habitat is in poor condition in
27% of stream length, fair in 25%, and good
in 47% based on least-disturbed reference
condition; data were unavailable for 1% of
stream length.
Vegetative cover in the riparian zone along
stream banks is in poor condition in 28% of
stream length, in fair condition in 21% of
stream length, and in good condition in 49%
of stream length.
The effects of acidification are not noted for
the Xeric ecoregion.
The Xeric ecoregion is
comprised of a mix of
physiographic features,
including plains with
hills and low mountains,
high-relief tablelands,
piedmont, high mountains,
and intermountain
basins and valleys (Photo
courtesy of Tim McCabe, U.S.
Department of Agricultural
Natural Resources
Conservation Service).
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Chapter 4
Summary and Next Step
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Chapter 4 Summary and Next Steps
Summary and Next
Steps
Summary
The United States covers an enormous and
diverse landscape, and not surprisingly, the
biological condition of the nation's streams varies
widely geographically. Overall, 42% percent of
the nation's stream length is in poor biological
condition compared to least-disturbed reference
condition in each of the WSA ecoregions.
The Eastern Highlands region has the largest
proportion of streams in poor biological
condition (52%), whereas the West has the lowest
proportion (27%). In the Plains and Lowlands
region, 40% of stream length is in poor biological
condition.
Stream miles, represented as stream length,
are not evenly distributed across the country.
The densest coverage of perennial streams in
the lower 48 states is in the Eastern Highlands
region, which has approximately 276,362 miles
of perennial streams and the smallest land area of
the three major regions. The Plains and Lowlands
region, which covers the largest portion of the
United States, has 242,264 miles of perennial
streams. The West has 152,425 miles of streams.
It is important to evaluate the survey results in
terms of both stream length percentages and
absolute stream miles in each condition class. For
example, the percentage of stream length in good
condition varies dramatically between the West
(45%) and Plains and Lowlands regions (29%);
however, if these percentages are converted to
stream miles, the West has 68,672 miles in good
condition, whereas the Plains and Lowlands
region has 70,257 miles in good condition.
The WSA finds that the most widespread
or common stressors are elevated levels of the
nutrients nitrogen and phosphorus, riparian
disturbance, and excess streambed sediments.
Nationally, 32% of stream length (213,394 miles)
has high concentrations of nitrogen compared
to least-disturbed reference conditions, and
31% (207,355 miles) has high concentrations of
phosphorus. Twenty-six percent of the nation's
stream length (171,118 miles) has high levels
of riparian disturbance (e.g., human influence
along the riparian zone), and 25% (167,092
miles) has streambed sediment characteristics
in poor condition. Analysis of the association
between stressors and biological condition finds
that high levels of nutrients and excess streambed
sedimentation more than double the risk of poor
biological condition.
The WSA provides the first nationally
consistent baseline of the condition of the
nation's streams. This baseline will be used
in future assessments to evaluate changes in
conditions and to provide insights as to the
effectiveness of water resource management
actions. Highlight: Acidification Trends and the
Clean Air Act illustrates how this type of survey
can be used to evaluate the effectiveness of
management actions on improving water quality.
States, EPA, and other partners plan to use this
approach to implement large-scale assessments of
lakes in 2007 and similar assessments of rivers,
wetlands, and coastal waters in future years.
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Chapter 4 Summary and Next Steps
Acidification Trends and the Clean Air Act
Although thisWSA provides a snapshot of the current conditions in the nation's streams, future
surveys will allow us to detect trends in stream conditions and in the stressors that affect them. One
example in which probability-based survey designs were implemented repeatedly over the course of
10 years has been the evaluation of the responsiveness of acid-sensitive lakes and streams to changes
in policy and management actions. Title IV of the 1990 Clean Air Act Amendments (CAAA) set target
reductions for sulfur and nitrogen emissions from industrial sources as a means of reducing the
acidity in deposition. One of the intended effects of the reductions was to decrease the acidity of
low-alkalinity waters. A 2003 EPA report by Stoddard et al., assessed recent changes in surface water
chemistry in the northern and eastern United States to evaluate the effectiveness of the CAAA. At the
core of the monitoring, known as the Temporally Integrated Monitoring of Ecosystems (TIME) project,
was the concept of a probability survey, where a set of sampling sites was chosen to be statistically
representative of a target population. In the Northeast (New England and Adirondacks), this target
population consists of lakes likely to be responsive to changes in rates of acidic deposition. In the
Mid-Atlantic, the target population is upland streams with a high probability of responding to changes
in acidic deposition. Repeated surveys of this population allowed an assessment of trends and changes
in the number of acidic systems during the past decade. The trends reported in the following table
are for recovery from chronic acidification. The analysis found that during the 1990s, the amount of
acidic waters in the target population declined. The number of acidic lakes in the Adirondacks dropped
by 38%, and the number of acidic lakes in New England dropped by 2%. The length of acidic streams
declined by 28% in the Mid-Atlantic area.
Estimates of change in number and proportion of acidic surface waters in acid-sensitive regions
of the northern and eastern United States. Estimates are based on applying current rates of
change in Gran ANC" to past estimates of population characteristics from probability surveys.
Region
New England
Adirondacks
Mid-Atlantic
Number of
Lakes
6,834 lakes
1,830 lakes
42,426 km
Number
Acidic"
386 lakes
238 lakes
5,0 1 4 km
Acidic0
5.6%
13.0%
11.8%
Time
Period
of
Estimate
1991-1994
1991-1994
1993-1994
Current
Rate of
ANC
Changed
+0.3
+0.8
+0.7
Estimated
Number
Currently
Acidic6
374 lakes
1 49 lakes
3,600 km
Current
Acidic
5.5%
8.1%
8.5%
Change
in
Number
of Acidic
Systems
-2%
-38%
-28%
a For both Northeast lakes and Mid-Atlantic streams, waterbodies with ANC (using the analytical technique of Gran titration,
with the result known as "Gran ANC") of < 100 [jeq/L are particularly vulnerable.
b Number of lakes/streams with Gran ANC < 0 in past probability survey (data collected at "Time Period of Estimate" in column 5).
c Percent of population (from Column 2) with Gran ANC < 0 in past probability survey (data collected at "Time Period of Estimate" in column 5).
d Based on regional trends in |jeq/L/year.
e Based on trends from repeated surveys through 2001.
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Chapter 4 Summary and Next Steps
Next Steps
In addition to characterizing the biological
condition of the nation's stream resources, the
WSA provides a rich data set that has sparked
interest in many additional areas of investigation.
These include the following:
• Support Protection and Restoration
Actions — The WSA finds that between 25
and 32% of stream length is rated poor due
to high levels of nutrients or excess streambed
sedimentation. These streams are two times
more likely to score poor for biological
condition than streams with low levels of
these parameters. This national-scale finding
reinforces reports from states and the USGS
on specific watersheds and stream segments
that identify nutrients and streambed
sedimentation as leading water quality
stressors. EPA is pursuing opportunities to
use the WSA data in combination with other
data to inform decision-makers responsible
for water resource protection and restoration
actions. Specific actions in the short term
include analyzing the WSA dataset to
determine associations between watershed
characteristics (e.g., size, slope, and soil type)
to help target where improvements are needed;
using these characteristics in conjunction
with information on the effectiveness of best
management practices (BMPs) to help identify
successful non-point source pollution controls;
and supporting states' development of water
quality standards for nutrients and sediments.
• Future Designs — It is clear that future
surveys will continue to be based on sample
survey designs and that the detection of
changes and trends will be of greater interest;
therefore, future survey designs will include
provision for estimating both current
status and future trends. This will require a
determination of the number of sites that are
revisited versus new sites. Current analyses
of variance components suggest that in
future surveys, a substantial percentage of the
sites (possibly 20—50%) should be replaced
with new sites and that this replacement
should continue with each new survey.
This replacement will help detect change;
incorporating new sites will improve future
status assessments and reduce the likelihood
that bias will be introduced by repeated
sampling of the same locations. As individual
states and tribes begin adopting sample survey
designs into their programs, the results from
their efforts can be incorporated into the
national assessments.
Indicators — This initial assessment was
unable to incorporate a large set of biological
and stressor indicators because of a short
planning timeline. In future national
stream surveys, the WSA will consider
including fish assemblages, algal assemblages
(e.g., periphyton in streams), fish tissue
contamination by metals and organics,
and/or sediment contamination assessed
through either sediment metal and organic
chemistry or sediment toxicity tests. It will
also be possible to add emerging stressor
indicators of concern. This will allow for
a more comprehensive assessment of both
the conditions in wadeable streams and the
stressors potentially affecting them.
Field Protocols —The field protocols used
for the WSA are widely used and were well
tested across the country. These protocols
have demonstrated a strong ability to detect
environmental signals against the background
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Chapter 4 Summary and Next Steps
of natural variability. For this initial assessment
of wadeable streams, using the same protocols
across the country reduced the complexity of
interpreting the results; however, for future
national stream surveys, the use of different
yet comparable methods will be evaluated for
different types of streams (e.g., low gradient
vs. high gradient). EPA and the states will
also explore integrating and sharing data from
multiple sources, as well as options to improve
sample collection methods.
Reference Conditions — Stream ecologists
and state and federal managers agree that they
should be able to describe least-disturbed
reference condition at a more refined spatial
scale than that of the nine regions presented
in the WSA. To do so will require substantial
coordinated efforts among state, tribal, and
federal partners. There are also likely to be
some regions of the country in which land-
use changes have been so dramatic that even
the "best" streams may have experienced
substantial chemical, physical, and biological
degradation. Additional research will be
required to provide a better solution to setting
expected conditions for those regions of the
country.
Stressor Ranking — The presentation on
stressors in the WSA showed both their
extent (i.e., the percent of stream length with
excessive levels of the stressors) and relative
risk (i.e., the increased chance of finding poor
biological condition). To make the best use
of this information, the WSA must look for
stressors that have both high relative risk and
large extent. The human health assessment
community combines these two sets of
information into a single number called the
"population attributable relative risk." If,
during investigation, this summary number
proves reliable for ecological studies, it will
simplify the ranking of stressors in future
assessments. However, use of more than one
biological assemblage in future assessments
will result in multiple relative risk values,
one for each biological indicator. It would
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Chapter 4 Summary and Next Steps
not be surprising if EPA and its partners find
that the relative risk posed by each stressor
depends on the biological community being
evaluated. Although these added numbers may
complicate the ranking ofstressors, they will
also aid in understanding which component
of the stream biota is sensitive to each stressor
and will provide additional options for
management.
• Future National Assessments — EPA and its
state, tribal, and federal partners will produce
national assessments of waterbody types
on a yearly cycle. For lakes and reservoirs,
a field survey will occur in 2007 with a
national assessment report of the results in
2009- Rivers will be surveyed in 2008, and
a national assessment report will follow in
2010. Wadeable streams will be surveyed
again in 2009, and the assessment report
that follows in 2011 will include all flowing
waters — both rivers and streams. That report
will also evaluate any changes in biological
condition that occurred in streams. An NCCR
assessment will be repeated in 2012, with the
results of the field survey from 2010. Wetlands
will be surveyed during the 2011 sampling
season, followed by a national assessment
report in 2013- From that point on, the
surveys and national assessment reports will be
repeated in sequence, with changes and trends
becoming a greater focus for each resource
survey.
The continued utility of these national surveys
and their assessment reports requires continued
consistency in design, as well as in field, lab,
and assessment methods from assessment to
assessment; however, the surveys must also
provide flexibility that allows the science of
monitoring to improve over time. Maintaining
consistency while allowing flexibility and growth
will be one of the many challenges facing the
national assessment program in coming years.
This national survey would not have been
possible without the involvement of hundreds of
dedicated scientists working for state, tribal, and
federal agencies and universities across the United
States. Future surveys will rely on this continued
close collaboration, a free exchange of knowledge,
and a deep well of energy and enthusiasm. It
is EPA's goal that participants translate the
expertise they gained through these national
surveys to studies of their own waters and use this
substantial and growing baseline of information
to evaluate the success of efforts to protect and
restore the quality of the nation's waters.
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Glossary of Terms
Glossary of Terms
Benthic macroinvertebrates: Aquatic larval
stages of insects such as dragonflies; aquatic
insects such as aquatic 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: State of being capable of
supporting and maintaining a balanced commu-
nity of organisms having 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-stream fish habitat: Areas fish need for
concealment and feeding. These areas include
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.
Macroinvertebrate Index of Biotic Condition:
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: Comprehensive
set of digital spatial data—based on U.S. Geolog-
ical 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 are essential to life but can over-
stimulate the growth of algae and other plants in
water. Excess nutrients in streams and lakes can
come from agricultural and urban runoff, leaking
septic systems, sewage discharges, and similar
sources.
O/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 (O). The taxa expected at
individual sites are based on models developed
from data collected at reference sites.
Perennial streams: Streams that flow
continuously throughout the year.
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: A discrete segment of a stream.
Reference condition: The least-disturbed
condition available in an ecological region;
determined based on specific criteria and used as a
benchmark for comparison with other sample
sites in the region.
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Glossary of Terms
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, such
as dams, roadways, pastureland, and trash.
Riparian vegetative cover: 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.
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 Ist-order streams
forms a 2nd-order stream, the confluence of two
2nd-order streams forms a 3rd-order stream, and
so on.
Streambed sediments: Fine sediments and silt on
the streambed. In excess quantities, they can fill in
the habitat spaces between stream pebbles,
cobbles, and boulders and suffocate
macroinvertebrates and fish eggs.
Stressors: Factors that adversely effect—and
therefore degrade—aquatic ecosystems. Stressors
may be chemical (e.g., excess 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, class, 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.
The Wadeable Streams Assessment: A Collaborative Survey of the Nation's Streams
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