A new definition of “waters of the United States” (“WOTUS”) will help drive the regulatory reach of the Federal Water Pollution Control Act, or Clean Water Act (“CWA”), starting March 20, 2023. The term WOTUS is used to determine the extent to which the CWA applies to different types of water bodies, such as rivers, streams, lakes, wetlands, and other water resources. Redefining WOTUS changes the scope of CWA programs imposing water quality standards, allocating total maximum daily loads of pollutants to impaired waters, certifying CWA Section 401 compliance, regulating the discharge of pollutants through National Pollutant Discharge Elimination System permits, and regulating the discharge of dredged or fill material under CWA Section 404 permits.