Southern Regional Water Program

Research, Extension & Education Water Quality Programs through the Land Grant University System

Regional TMDL Information and Programs

TMDL Definition -- What is a Total Maximum Daily Load(TMDL)?

A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.

Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use.

A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody can be used for the purposes the State has designated. The calculation must also account for seasonable variation in water quality. The above definition was provided by the EPA.

The Clean Water Act requires states to establish water quality standards and TMDL programs, and for EPA to assume those responsibilities if the states do not comply.

EPA sites that link to TMDL information:

Pages summarizing TMDL information by EPA regions:

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