U.S. Geological Survey Sept. 7, 2010, press release:

The Potomac River in Washington, D.C., is showing multiple benefits from restoration efforts, newly published research suggests. Reduced nutrients and improved water clarity have increased the abundance and diversity of submerged aquatic vegetation (SAV) in the Potomac, according to direct measurements taken during the 18-year field study.

“Improvements to plant communities living at the bottom of the river have occurred nearly in lock step with decreases in nutrients and sediment in the water and incremental reductions in nitrogen effluent entering the river from the wastewater treatment plant for the Washington, D.C., area,” said USGS scientist Dr. Nancy Rybicki.

Read more here.