"The U.S. Environmental Protection Agency (EPA) surveyed 1.9 million km (1.2 million mi) of rivers and streams and in March released its findings in the National Rivers and Streams Assessment (NRSA) 2008/2009: A Collaborative Survey. The survey found that 46% of rivers and streams are in poor biological condition, and 25% are in fair condition.
Waterways with high levels of phosphorus, nitrogen, and sediments are about twice as likely to have poor macroinvertebrate (aquatic insect) communities. In every 8 km (5 mi) surveyed, levels of excess nutrients were found in more than 3 km (2 mi) and high levels of riparian disturbance, such as nearby roads, buildings, and parking lots, were found in about 1.6 km (1 mi). In addition, about 1.6 km (1 mi) in 6 km (4 mi) did not have healthy shoreline vegetation, and 1.6 km (1 mi) in 10 km (6 mi) had excess streambed sediments.
The survey also found that 23% of waterways had enterococci bacteria levels exceeding thresholds set to protect human health, and more than 20,900 km (13,000 mi) had mercury in fish tissues exceeding these thresholds, the fact sheet says.
When compared to the 2004 Wadeable Streams Assessment, the survey found that while riparian vegetation cover had improved by 10%, there was a 9% decline in biological quality, a 14% decline in phosphorus conditions, and a 12% increase in riparian disturbance, the fact sheet says.
Reducing nutrients and improving habitat would improve biological health of these waterways. Potential solutions include completing state nutrient management strategies, adopting stream and shoreline buffers, supporting farmers’ efforts to manage nutrients and prevent pollution, and improving nutrient removal in wastewater treatment, the fact sheet says."