Submitted to: Interagency Conference on Research in the Watersheds
Publication Type: Abstract Only
Publication Acceptance Date: February 26, 2003
Publication Date: March 20, 2003
Citation: HUBBARD, R.K., SHERIDAN, J.M., BOSCH, D.D. A DERIVED-DISTRIBUTION APPROACH TO DAILY LOADS OF DISSOLVED AND SUSPENDED SOLIDS IN COASTAL PLAIN STREAMFLOW. INTERAGENCY CONFERENCE ON RESEARCH IN THE WATERSHEDS. PAGE 595-600. 2003. Technical Abstract: Estimates of allowable total maximum daily loads (TMDLs) of sediment must be developed for selected streams and rivers across the US. The sediment TMDLs are required to quantify total daily assimilative loads for those streams which are deemed to have impaired water quality due to sediment, and are required for formulating plans to improve these streams. A TMDL is defined as a daily stream loading rate (e.g., kg/day). However, actual stream sediment data are collected in terms of concentrations (e.g., mg/L), thus requiring estimates of streamflow to make the necessary rate and load conversions. A "derived distribution" (DD) is the frequency distribution of the dependent variable that is "derived" from the distribution of the independent variables through a monotonic functional relationship between the dependent and independent variables. The USDA-ARS, Southeast Watershed Research Laboratory (SEWRL) in Tifton, Georgia has collected over 30 years of hydrologic and climatic data from the 334 km2 Little River Watershed (LRW). The LRW is typical of heavily vegetated landscapes and slow-moving stream systems of the southeastern Coastal Plain. Field studies quantifying dissolved and suspended loads in LRW streamflow have been conducted during the 30 year period (1974-1978, 1984-1986), but a continuous record of measured loads does not exist. A DD approach is being used to estimate total maximum daily dissolved and suspended loads in LRW streamflow. This paper presents results of comparisons of the measured and estimated dissolved and suspended solids for the record period, and compares this approach to estimating TMDLs to methods currently being used by the State of Georgia for the LRW and portions of the Upper Suwannee River Basin of the southeastern Coastal Plain.