From the EPA website:
Forty years ago, in the midst of a national concern about untreated sewage, industrial and toxic discharges, destruction of wetlands, and contaminated runoff, the principal law to protect the nation’s waters was passed. Originally enacted in 1948 to control water pollution primarily based on state and local efforts, the Federal Water Pollution Control Act, or Clean Water Act (CWA), was totally revised in 1972 to give the Act its current shape. The CWA set a new national goal “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters”, with interim goals that all waters be fishable and swimmable where possible. The Act embodied a new federal-state partnership, where federal guidelines, objectives and limits were to be set under the authority of the U.S. Environmental Protection Agency, while states, territories and authorized tribes would largely administer and enforce the CWA programs, with significant federal technical and financial assistance. The Act also gave citizens a strong role to play in protecting and restoring waters.
The CWA specifies that all discharges into the nation’s waters are unlawful unless authorized by a permit and sets baseline, across-the-board technology-based controls for municipalities and industry. It requires all dischargers to meet additional, stricter pollutant controls where needed to meet water quality targets and requires federal approval of these standards. It also protects wetlands by requiring “dredge and fill” permits. The CWA authorizes federal financial assistance to states and municipalities to help achieve these national water goals. The Act has robust enforcement provisions and gives citizens a strong role to play in watershed protection. Congress has revised the Act, most notably in 1987, where it established a comprehensive program for controlling toxic pollutants and stormwater discharges, directed states to develop and implement voluntary nonpoint pollution management programs, and encouraged states to pursue groundwater protection. Notwithstanding these improvements, the 1972 statute, its regulatory provisions and the institutions that were created 40 years ago, still make up the bulk of the framework for protecting and restoring the nation’s rivers, streams, lakes, wetlands and coastal waters.