Purpose
Report on the
condition of
wadeable streams of
the US.
•
Help build State
capacity for
monitoring and
assessment.
Promote
collaboration across
jurisdictional
boundaries in the
assessment of water
quality.
841F06001
The Wadeable Streams Assessment:
A Collaborative Survey of
the Nation's Streams
Background
The Wadeable Streams Assessment (WSA) is a first-ever, statistically-
valid survey of the biological condition of streams throughout the
U.S. Wadeable streams—streams and rivers that are shallow enough
to sample without boats—were chosen for study because they are
a critical natural resource, because we have a well-established set
of methods for monitoring them, and because they are frequently
under-sampled in traditional monitoring programs. This project was
a collaborative effort involving states, EPA and other federal agencies,
tribes, universities and other organizations.
The WSA was designed using modern survey techniques, 1,392 random sites were
sampled to represent the condition of all streams in regions that share similar ecological
characteristics. Participants used the same standardized methods at all sites, to ensure
results that are comparable across the nation. A rigorous quality control program included
training all field crews, auditing field crews and labs, and re-sampling 10% of the sites. The
sampling began with pilot work in the West in 2000 and was completed nationwide in 2004.
The WSA used benthic macroinvertebrates to determine the biological condition of streams.
Benthic macroinvertebrates are small creatures that live in streams attached to rocks and
woody debris, or burrowed into the stream bottom. They
include aquatic larval stages of insects such as flies and drag-
onflies; crustaceans such as crayfish; and worms and snails.
These organisms are found everywhere, even in the smallest
streams that cannot support fish. Since some benthic macro-
invertebrates are more sensitive to pollution than others, in-
formation on the abundance the various types of organisms
tells us whether a stream is healthy.
The WSA supplemented information on the biological
condition of streams by measuring key chemical and
physical indicators that reveal stress or degradation of
streams. The WSA reports on four chemical indicators
(phosphorus, nitrogen, salinity, and acidity) and four
physical condition indicators (streambed sediments, in-
stream fish habitat, riparian vegetative cover, and riparian
disturbance).
The WSA was designed to provide regional and national
assessments of stream quality, and findings are presented using three different reporting
levels. The first level is the conterminous U.S. or lower 48 states; Alaska and Hawaii were
not included in this assessment, but pilot projects are underway in those states. The second
level is three major climate and landform regions (the Eastern Highlands, Plains and Low-
lands, and West). The third level is the nine ecological regions that further divide the three
major climate and landform regions. There were not enough sites in the survey to allow sta-
tistically-valid assessments of water quality at the state level.
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Your comments
are welcome
The draft Wadeable
Streams Assessment re-
port is available for public
review and comment at
http://www.epa.gov/owow/
streamsurvey. It includes
an appendix further ex-
plaining the WSA analyti-
cal approach. Additional
technical information is
available at this website.
We invite your comment
on the report's format, ap-
proach, and findings, and
plan to release the final
WSA report, incorporating
review comments, by late
summer 2006.
Please submit any com-
ments on the draft Wade-
able Streams Assessment
to wadeablestreams@epa.
gov by June 30, 2006.
\
ui
9
EPA-841-F-06-001
For more information visit:
www.epa.gov/owow/streamsurvey
or contact:
Susan Holdsworth, USEPA
202-566-1187
holdsworth.susan@epa.gov
Findings
The WSA found that 28% of U.S. stream miles are in good condition compared to the best
available reference sites in their regions, 25% are in fair condition, and 42% are in poor
condition. Another 5% were not assessed.
Stream quality varies widely across the diverse ecological regions of the U.S. Of the three
large climate and landform regions, the West is in the best condition, with 45% of the
length of wadeable streams and rivers in good condition. In the Eastern Highlands region,
18% of stream length is in good condition and more than half is in poor condition. The
quality of streams in the Plains and Lowlands region falls between the other two regions,
with almost 30% of stream length in good condition and 40% in poor condition. (Figure 1)
4*
^^ w.ow
Eastern Highlands,
276 J62 miles
"(ewer 48"
Btgiogrcaf Quality
• Good 3 Fair • Poor LJ Nol Aiseise.d
Figure 1. Condition of wadeable streams
The most widespread stressors observed across the country and in each of the three major
regions are nitrogen, phosphorus, streambed sediments, and riparian disturbance. These
stressors can degrade stream conditions for fish and other aquatic life. Nitrogen and
phosphorus are nutrients that can increase the growth of algae, decrease levels of dissolved
oxygen and water clarity, and degrade stream habitat. Excess streambed sediments can
smother habitat for aquatic organisms. Riparian disturbance is evidence of human activity
alongside streams, such as pipes, pavement and pastures.
Conclusion
The WSA indicates that our current focus on understanding and reducing levels of
nutrients and sediments in the nation's waters should yield important gains in water
quality in coming years. EPA is working together with the states to develop water quality
criteria and implement pollution control practices to reduce the amount and impacts of
nutrients and sediments in the Nation's waters.
The WSA establishes a national baseline we can use to compare to results from future
studies. This information will help us evaluate the successes of our national efforts to
protect and restore water quality. Along with upcoming studies of other water resource
types—coastal waters, lakes, large rivers and wetlands—the WSA responds to criticisms
that the nation's monitoring programs are not providing key answers about water quality.
The WSA also provides funding and expertise that will enhance each state's ability to
monitor and assess the" quality of its waters in the future.
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