are nitrogen and phosphorus from fertilizers. An influx of these nutrients can lead to eutrophication within the water. This is when there is an excess of nutrients in water, thus leading to an explosion in the growth of algae. The algae can cover the lake and block sunlight from reaching the organisms below, typically killing them. Legal framework Some aspects of NPS water pollution are regulated at the federal, state, and local level, but to a lesser extent than point sources. The pollution persists and remains a significant problem in many watersheds. NPS water pollution comes from numerous and diverse sources, and control measures are expensive to implement. State and local governments are generally responsible for implementing NPS regulations. Coordination among localities can be difficult, and, furthermore, localities often lack the incentive to rigorously enforce NPS regulations because their NPS pollution is exported downriver, where other towns and cities must deal with the consequences. Federal laws There are two principal federal laws effecting NPS water pollution: the Clean Water Act and the Coastal Zone Management Act. In addition, EPA's "Clean Water Action Plan" (2009) outlines a strategy for enforcing CWA requirements, some of which are applicable to nonpoint sources. Clean Water Act The Clean Water Act (CWA) was the first federal law designed to directly address water pollution. The CWA has been amended many times, but the 1972 amendments provide the core statutory basis for the regulation of point source water pollution and created the National Pollutant Discharge Elimination System (NPDES) permit program. The 1972 amendments were also the first instance where Congress acknowledged the problem of NPS water pollution by requiring the states to prepare area-wide water quality management plans under Section 208. Congress passed additional amendments to the CWA in 1987 that address NPS water pollution. This section will chronologically address the parts of the CWA that regulate NPS water pollution. Defining NPS water pollution in the CWA The definition of NPS water pollution is open to interpretation. However, federal regulation under the CWA provides a specific legal definition for the term. A "nonpoint source" is defined as any source of water pollution that is not a "point source" as defined in CWA section 502(14). That definition states: "The term 'point source' means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal