Developing contaminant loads for Georgia streams
Bradshaw, James K.
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Comparing contaminant loads from streams in single-land use watersheds to appropriate reference streams and modeling water quality with a watershed-scale GIS model may be an effective method for determining background contaminant loads. Water samples taken during storm and base flow were used to calculate sediment and phosphorus loads in four small single-land use watersheds and the Soil Water Assessment Tool (SWAT) was calibrated for sediment -and phosphorus from agricultural watersheds. Sediment loads ranged from 241 to 1725 kg ha1-1-1-1yr and total P loads ranged from 0.145 to 1.87 kg hayr. Error between predicted and observed sediment loads ranged from 7-367% and error between predicted and observed TP loads ranged from 47-70%. The results of this study indicate that better best management practices (BMP’s) need to be implemented in agricultural watersheds to control phosphorus and that SWAT may not be an appropriate model to aid in TMDL development for small streams.