Measures taken under the Clean Water Act have successfully reduced much point source pollution, such as direct discharges from factories and wastewater treatment plants, the report says. But many of the Mississippi's remaining pollution problems stem from nonpoint sources -- mainly nutrients and sediments that enter the river and its tributaries through runoff, the committee said. Nutrients, such as nitrogen and phosphorous from fertilizers, create significant water-quality problems in the river itself and contribute to an oxygen-deficient "dead zone" in the northern Gulf of Mexico. Sediments present a more complex problem; in the upper Mississippi, they are too plentiful and considered a pollutant, while in the lower river, sediments are too scarce -- a shortfall that is contributing to losses of coastal wetlands in southern Louisiana.
Given that the Clean Water Act addresses nonpoint source pollution only in a limited manner, and that the Mississippi's water quality also is affected by physical structures which the Act cannot alter -- such as dams and levees -- the Clean Water Act cannot be the only means for improving water quality in the river and Gulf, the report says. Nevertheless, it can effectively address many aspects of pollution in these waters if the law's provisions are comprehensively implemented.
Currently, efforts to monitor and improve water quality in the Mississippi are complicated by the river's interstate nature. According to the Clean Water Act, states are responsible for establishing water-quality standards and for monitoring water quality, but many states that are bordered by the Mississ
|Contact: Sara Frueh|
The National Academies