Designated beneficial uses are the desirable uses that water quality should support. Examples are drinking water supply, primary contact recreation (such as swimming), and aquatic life support. Each designated use has a unique set of water quality requirements or criteria that must be met for the use to be realized. States, Tribes, and other jurisdictions may designate an individual water-body for multiple beneficial uses. A waterbody is considered to be impaired when it does not attain water quality standards due to an individual pollutant, multiple pollutants, pollution, or an unknown cause of impairment that preclude it from supporting its designated uses.
Priority for regulation is the Total Maximum Daily Load (TMDL) development priority. A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. In other words, it is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources, and includes a margin of safety and consideration of seasonal variations. In addition, a TMDL contains the reductions needed to meet water quality standards and allocates those reductions among the sources in the watershed. The objective of the TMDL process is to systematically identify impaired or threatened waterbodies and the pollutant(s) causing the impairment and ultimately establish a scientifically-based strategy for correcting the impairment or eliminating the threat and restoring the waterbody. Scorecard reports six categories of priorities; targeted (a TMDL is expected to be developed within two years), high, medium, low, not assessed (the state agency responsible for TMDL development has not determined a waterbody's TMDL development priority), and not reported (no information was submitted to EPA regarding a waterbody's TMDL development priority)
