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.