Nonpoint source (NPS) pollution is water pollution affecting a water boy from diffuse sources, rather than a point source which discharges to a water body at a single location. NPS may derive from many different sources with no specific solution to rectify the problem, making it difficult to regulate. According to the U.S. Environmental Protection Agency (EPA), nonpoint source pollution is the leading cause of water pollution in the United States today, with polluted runoff from agriculture the primary cause.