Fifty-five percent of the nation’s rivers and streams do not support healthy populations of aquatic life, with phosphorus and nitrogen pollution and poor habitat being main culprits for these river and stream miles being rated in poor biological condition, according to a recently released Environmental Protection Agency assessment.
The National Rivers and Streams Assessment (NRSA) 2008-2009 Draft Report was released for public comment by the Environmental Protection Agency. Comments are due to firstname.lastname@example.org by May 9, 2013.
Additionally a free webcast on the findings of the NRSA 2008-2009 will be held on April 3, 2013.
This draft report is one of a series of aquatic resource assessments being conducted by the EPA along with states and tribes. The lag time between data collection and the report is obvious from the dating—2008-2009—in the report title.
The assessment of rivers and streams found that only 23 percent of them are in fair condition and 21 percent are rated as in good condition.
An explanation of how and why the assessments was provided by the EPA. “Often referred to as probability-based surveys, these studies provide nationally consistent and scientifically-defensible assessments of our nation's waters and can be used to track changes in condition over time. The surveys use standardized field and lab methods and is designed to yield unbiased estimates of the condition of the whole water resource being studied,” the EPA intro explains.
The good, fair and poor ratings are based on biological indexed ratings. The biological rating is based on an index that combines different measures of “aquatic macroinvertebrates” (aquatic insects and creatures such as crayfish).
The EPA blames phosphorus and nitrogen pollution for much of the negative water quality. Forty percent of the nation’s river and stream miles have high levels of phosphorus, and 27 percent have high levels of nitrogen.
Nutrient pollution is mentioned extensively in a summary fact sheet. “Biological communities” are at increased risk because of high phosphorus and nitrogen pollution. The nutrient pollution is blamed on excess fertilizers, wastewater and other sources, which causes algae blooms, low oxygen levels and more.
Quality of the rivers and streams is also being destroyed by “poor vegetative cover and high levels of human disturbance” near the waterways. Disturbance is resulting in erosion and streambed sediments, “which can smother the habitat where many aquatic organisms live or breed.”