Final answer:
The Clean Water Act (CWA) of 1972 has had the greatest impact on water quality in the United States by regulating pollution from point and nonpoint sources, setting pollution standards, and requiring permits for discharges.
Explanation:
The Clean Water Act (CWA) of 1972 has had the greatest impact on water quality in the United States.
Enacted to regulate pollution from point and nonpoint sources, the CWA empowered the Environmental Protection Agency to set pollution standards, significantly improving U.S. water quality and ecosystems.
For example, through the National Pollutant Discharge Elimination System, the CWA required permits for discharges, promoting the use of best available technology to mitigate pollution.
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