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OVERVIEW OF TOTAL MAXIMUM DAILY LOAD (TMDL) PROBLEM AND SUPPORTING MODEL DEVELOPMENT
Citation:
McCutcheon, S C. AND J. Pendergast. OVERVIEW OF TOTAL MAXIMUM DAILY LOAD (TMDL) PROBLEM AND SUPPORTING MODEL DEVELOPMENT. Presented at Appalachian Rivers II Conference, Morgantown, WV, July 27-29, 1999.
Description:
Approximately 18,900 impaired water bodies are on the 303(b) state lists required by the Clean Water Act. Of the 300 types of impairments on the 1996 and 1998 lists, 24% involve sediments, suspended solids, or turbidity. Nutrient problems account for 15% of the listings, and pathogens, 14%. The EPA Office of Research and Development (ORD) and the Office of Water are working closely together to develop protocols and models to address TMDL problems in order of frequency of occurrence. The ORD is developing TMDL models under its Ecological Research and Restoration Strategy, and the Office of Water under its pioneering watershed approach. The National Exposure Research Laboratory is developing methods for simpler sediment budgets and more complex sediment routing from watersheds through stratified lakes and estuaries. The EPA Office of Water is working with David Rosgen and interagency partners to develop and test the components method of sediment routing based
on extensive experience in stream geomorphology. The range of simple sediment balances, the
geomorphical components analysis, and the more complex multidimensional routing techniques should provide adequate science-based tools to address most sediment TMDLs. Data are being collected for the South Fork of the Broad River in Georgia and with data available from U.S. Agricultural Research Service, the Forest Service, and the U.S. Geological Survey, sufficient testing of new methods and protocols should be possible. By 2004 a case study for nutrient TMDLs is expected that will probably focus on the Neuse River in North Carolina. The ORD expects to focus on pathogens and toxic chemicals during 2005 until 2008. Each component model is being developed using a multimedia modeling context by ORD. In the short-term, the Office of Water has developed the BASINS system to manage data bases and existing water quality models in a manner that can be adapted for each state unless other methods are available.