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 email@example.com 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.”
Ratings show that more eastern rivers and streams are in poor condition as a whole than elsewhere in the U.S. The nation is divided into nine “ecological regions.” Northern Appalachians (New England) has 57 percent of its streams and rivers in poor condition. The Southern Appalachians (Mid-Atlantic and South outside of the Atlantic coast) has 65 percent of its river and stream miles in poor condition. The largest percentage of poor rivers and stream miles occurs in the Coastal Plains (Southeast Atlantic and Gulf of Mexico coastal areas) at 71 percent poor.
The Mississippi River and Illinois River basins have received a lot of attention about having high levels of nutrient pollution in rivers, but the Temperate Plains area that includes these basins only has a 55 percent poor quality rating.
The river and stream miles rated at poor for other regions are Upper Midwest, 59 percent; Northern Plains, 33 percent; Southern Plains, 41 percent; and Western Mountains (Pacific Northwest) at 26 percent. The Xeric region covers most of the area west of the Rocky Mountains and had a poor rating of 43 percent of its river and stream miles.
The summary fact sheet suggests that the biggest human health concern is mercury in fish. More than 13,000 miles of rivers are stipulated as “having mercury in fish tissue at levels that exceed thresholds protective of human health.”
The only comparison for the NRSA 2008-2009 quality is to the 2004 Wadeable Streams Assessment. In comparison, the 2008-2009 assessment shows 7 percent fewer streams are in good biological condition, 19 percent fewer stream miles are in good condition for phosphorus but 9 percent more stream miles are in good condition for nitrogen.