The law governing water quality in the United States is mainly statutory, comprising the Clean Water Act, which governs water quality in effluent to U.S. waters, and the Safe Drinking Water Act, which regulates drinking water quality standards. However, surface water quality is also impacted by many other statutes that regulate the contamination of air, soil, and groundwater by toxic substances.

Moreover, the type and scale of contaminants present in streams, lakes, rivers, and the oceans is shifting. Non-point sources of nitrogen and phosphorus create grave threats to human health and the environment, while point-source emerging contaminants of concern create long-term environmental challenges.

The Clean Water Act and Water Quality

The Clean Water Act (CWA) forms the core of water quality regulation in the United States and is a cornerstone of environmental law. The 1972 statute prohibits the discharge of a pollutant from a point source into a navigable water without a permit. Other important aspects of the CWA included setting treatment criteria for publicly owned treatment works, regulating fill and dredging in wetlands, and defining national water quality standards for surface waters [1].

Per the statute, the CWA is comprehensive, encompassing everything from wetland development and restoration to the discharge of dangerous industrial chemicals. The CWA also regulates the discharge of non-point source pollutants through nonbinding TMDLs that act as a backstop protection for ambient water quality [2]. Federal courts have decided a range of cases to do with non-point source runoff, including nutrient reduction standards promulgated in states such as Florida (see Florida Wildlife Federation, Inc. v. Johnson, 2009).

The Supreme Court’s decision in County of Maui v. Hawaii Defense Fund (2020) impacts the CWA’s jurisdiction over discharge of contaminants through groundwater to surface waters explicitly protected by the Act. The Supreme Court has also granted cert in Sackett v. USEPA (2023), a case that may implicate the federal government’s jurisdiction to regulate wetlands that are not adjacent to navigable waters under the CWA. These changes highlight the potential for continuing legal challenges in the sphere of water quality.

Importantly, the CWA does not directly regulate pollutant discharges to groundwater. See the section on County of Maui v. Hawaii Wildlife Fund for a further discussion of the important hydrologic connections between surface water and groundwater. This hydrologic connection is of increasing importance in cases dealing with contamination from underground septic systems (Peconic Baykeeper v. Harvey, 2021), discharges from unlined waste pits (Toxics Action Center v. Castella Waste Systems, 2021), and leachate from sediment deposits (Conservation Law Foundation v. NH Fish and Game Dep't, 2020).

The Overlap Between the CWA and Other Environmental Legislation

There is considerable overlap between the effluent regulations in the CWA and the drinking water regulations in the Safe Drinking Water Act (SDWA). Discharges of nutrients such as nitrates into streams and rivers can lead to harmful algal blooms (HABs) that produce toxic by-products that can adversely impact towns and cities that source their drinking water from contaminated waters. Recent court cases including Rio Hondo Land & Cattle Co. v. U.S. Environmental Protection Agency (2021) highlight the dangers of these HABs on downstream communities. Nitrates are also toxic in their own right, particularly for infants; cities can be forced to spend hundreds of millions of dollars to retrofit drinking water treatment systems to efficiently remove them from contaminated source waters (see Bd. of Water Works Trs. of Des Moines v. Sac Cnty. Bd. of Supervisors of Drainage Districts 32, 42, 65, 79, 81, 83, 2017).

Although the regulation of water quality primarily falls under the jurisdiction of the SDWA and the CWA, other statutes also impact water quality in a variety of ways. The Clean Air Act (CAA) regulates emissions of nitrous oxides (NOx) and sulfur oxides (SOx), contaminants that can result in both acid rain and (in the case of NOx) nitrate contamination of surface waters. The Resource Conservation and Recovery Act (RCRA) manages discharges from underground sites such as landfills into groundwater. Other statutes such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), and the Toxic Substances Control Act (TSCA) are intended to regulate discharges (and cleanup) of toxic substances such as herbicides into surface or groundwater.

[1] R. Percival, C. Schroeder, A. Miller and J. Leape, Environmental Regulation: Law, Science, and Policy, 9th ed., Boston, MA: Aspen Publishing, 2021.

[2] American Bar Association, The Clean Water Act Handbook, 4th ed., M. A. Ryan, ed., Washington, D.C.: ABA Book Publishing, 2018.