Identifying the Major Sources of Nutrient Water Pollution

摘要

Since the passage of the Clean Water Act (CWA) in 1972, more than $540 billion has been spent on water pollution controls. In spite of this massive commitment of funds, in 1992 approximately 44% of U.S. river miles tested still did not fully support the uses designated by the states. One well-recognized problem is the lack of controls in the CWA for nonpoint-source pollution. Preventing or controlling pollution from non-point sources has been stymied, in part, because little was known about the relative magnitudes of non-point and point sources of nutrients at the national level. Only recently has it been possible to estimate the major sources of nutrients entering watersheds and relate these inputs and resulting stream loads to land use patterns and regional settings.