As indicated by the placement of WQS in all parts of the waterbody system illustrated in the accompanying slide, water quality standards should be set for all surface waters meeting the definition of "waters of the United States."

States, territories, and designated tribes can, using their own authorities, adopt standards for additional surface waters. Also, though the CWA does not require WQS for ground water, states, tribes, and territories can use their own authorities to set targets for ground water.