Pu

Report on the 

condition of 

wadeable streams of 

the US.

rpose

Help build State 

capacity for 

monitoring and 

assessment.

Promote 

collaboration across 

jurisdictional 

boundaries in the 

assessment of water 

quality.

The Wadeable Streams Assessment:

A Collaborative Survey of 

the Nation’s Streams 

Background 

The Wadeable Streams Assessment (WSA) is a first-ever, statisticallyvalid 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 dragonflies; 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 macroinvertebrates are more sensitive to pollution than others, information 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, instream 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 Lowlands, 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 statistically-valid assessments of water quality at the state level.
Your comments 

are welcome

The draft Wadeable 

Streams Assessment report is available for public 

review and comment at 

http://www.epa.gov/owow/

streamsurvey. It includes 

an appendix further explaining the WSA analytical approach. Additional 

technical information is 

available at this website. 

We invite your comment 

on the report’s format, approach, and findings, and 

plan to release the final 

WSA report, incorporating 

review comments, by late 

summer 2006. 

Please submit any comments on the draft Wadeable Streams Assessment 

to wadeablestreams@epa.

gov by June 30, 2006.

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)

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.

EPA-841-F-06-001

For more information visit: 

ww.epa.gov/owow/streamsurvey

 or contact: 

Susan Holdsworth, USEPA

202-566-1187

holdsworth.susan@epa.gov

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