Agricultural phosphorus and water quality: a U.S. Environmental Protection Agency perspective

Pollution of lakes, rivers, and estuaries from agricultural sources of P is a major water quality problem in the USA. This paper explains the regulatory and nonregulatory programs developed by the U.S. Environmental Protection Agency (USEPA) to implement its legal mandate to control water pollution from these sources. The Clean Water Act defines concentrated animal feeding operations as point sources of pollution that are required to obtain permits to discharge into waters of the USA. All other agricultural sources are considered nonpoint and are not regulated under federal law. The USEPA provides grant money to the states to develop and implement nonpoint source programs. The Coastal Zone Act Reauthorization Amendments of 1990 requires coastal states to adopt nonpoint management measures that are backed by enforceable policies and mechanisms. For water bodies that continue to be impaired despite the basic implementation of these laws and other programs, states are required to develop a total maximum daily load (TMDL). The TMDL process is the quantitative basis for reaching water quality standards. The USEPA is putting a new emphasis on controlling nutrient pollution sources to meet the goal of the Clean Water Act.