“Total Maximum Daily Loads are quantitative analyses of water bodies where one or more water quality standards are not being met, and are aimed at identifying the management strategies necessary to attain those water quality standards. In essence, TMDLs describe the amount of each pollutant a water body can receive without violating standards, and are characterized as the sum of wasteload allocations, load allocations, and a margin of safety to account for uncertainties. Wasteload allocations are pollutant loads attributable to existing and future point sources, such as discharges from industry and sewage facilities. Load allocations are pollutant loads attributable to existing and future nonpoint sources and natural background. Nonpoint sources include runoff from farms, forests, urban areas, and natural sources, such as decaying organic matter and nutrients in soil.

TMDLs take into account the water quality of an entire water body or watershed and assess all the pollutant loadings into that watershed, rather than simply considering whether each individual discharge meets its permit requirements. The management strategies that emerge from the TMDL process may encompass everything from traditional regulatory measures, agricultural best management practices and other pollution prevention measures, land acquisition, infrastructure funding, pollutant trading, and the like. They also will include an overall monitoring plan to test their effectiveness.”

source:http://webapps.dep.state.fl.us/DearTmdl/welcomehz.do