Handbook for Developing Watershed TMDLs

Since 1995, more than 37,000 TMDLs have been completed by the states and U.S. Environmental Protection Agency (EPA). However, to address the ever growing number of impaired waterbodies, it is necessary for states to expedite TMDL development using an approach that will efficiently address the maximum number of impairments in a scientifically defensible manner. One strategy is to use a watershed framework for developing TMDLs. Grouping multiple impaired segments into a watershed TMDL development effort not only provides a number of cost and time efficiencies to the TMDL development process, but it can also better represent source-impairment dynamics to facilitate more effective allocations and implementation for reducing point and nonpoint source loads to restore impaired waterbodies to water quality standards.To further promote the development of watershed TMDLs, EPA is developing a handbook to provide TMDL practitioners the information to move from concept to practice—to make watershed TMDLs a standard approach in their programs. Handbook for Developing Watershed TMDLs identifies the issues for practitioners to consider and tools and resources that can help them when planning for and developing watershed TMDLs. There are a number of issues that arise when developing watershed TMDLs versus single-segment TMDLs. For example, addressing multiple impaired segments and impairments in one analysis can increase the amount of data to review, address multiple sources contributing to multiple impairments, involve more and varied stakeholders, and result in a greater number of allocation options. The handbook discusses these issues for each step of the TMDL development process, including stakeholder and public involvement, watershed characterization, linkage analysis, allocation analysis, and development of the TMDL report.The document also identifies the benefits of developing watershed TMDLs as well as the challenges and ways to address them. The document contains numerous examples, tips and resources to further support TMDL practitioners in understanding how to develop watershed TMDLs. Finally, the document evaluates the connections between watershed TMDLs and other water programs and identifies opportunities for integrating watershed TMDLs and their results into other watershed management efforts, such as monitoring, watershed planning, watershed-based permitting and water quality trading.EPA developed the handbook to serve as a programmatic and technical resource for TMDL practitioners. Its goal is to promote development of TMDLs on a watershed basis and in doing so to help states realize a number of environmental and programmatic benefits over single-segment TMDLs. The handbook serves to further support EPA's programmatic efforts to integrate watershed approaches in a number of related water programs to effectively protect and restore water resources.