Throughout the U.S., data are often lacking adequate spatial or temporal coverage to reliably establish the sources and magnitude of water quality degradation.
Calculating the TMDL for any given body of water involves the combination of factors that contribute to the problem of nutrient concentrated runoff.
Pollutants that originate from a point source are given allowable levels of contaminants to be discharged; this is the waste load allocation (WLA).
Industrial dischargers, farmers, land developers, municipalities, natural resource agencies, and other watershed stakeholders each have a vested interest in the outcome.
[13] The permits are issued by EPA or delegated state agencies under the National Pollutant Discharge Elimination System (NPDES).
The TMDL implementation plan is intended to help bridge this divide and ensure that watershed beneficial uses are restored and maintained.
Local watershed groups play a critical role in educating stakeholders, generating funding, and implementing projects to reduce nonpoint sources of pollution.