SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Evaluating Nonpoint-Source Critical Source Area Contributions at the Watershed Scale 
Authors:White, M.J., D.E. Storm, P.R. Busteed, S.H. Stoodley, and S.J. Phillips 
Journal:Journal of Environmental Quality 
Article ID: 
URL (non-DOI journals): 
Broad Application Category:pollutant only 
Primary Application Category:critical source area assessment 
Secondary Application Category:pollutant cycling/loss and transport 
Watershed Description:Six watersheds in different Oklahoma regions ranging from 230 to 1970 km^2 in size (see Tables 1 and 2) 
Calibration Summary: 
Validation Summary: 
General Comments: 
Abstract:critical source areas [CSAs]) have been widely recognized as priority areas for the control of nonpoint-source pollution. Th e identifi cation and evaluation of CSAs at the watershed scale allows state and federal programs to implement soil and water conservation measures where they are needed most. Despite many potential advantages, many state and federal conservation programs do not actively target CSAs. Th ere is a lack of research identifying the total CSA pollutant contribution at the watershed scale, and there is no quantitative assessment of program eff ectiveness if CSAs are actively targeted. Th e purpose of this research was to identify and quantify sediment and total phosphorus loads originating from CSAs at the watershed scale using the Soil and Water Assessment Tool. Th is research is a synthesis of CSA targeting studies performed in six Oklahoma priority watersheds from 2001 to 2007 to aid the Oklahoma Conservation Commission in the prioritized placement of subsidized conservation measures. Within these six watersheds, 5% of the land area yielded 50% of sediment and 34% of the phosphorus load. In watersheds dominated by agriculture, the worst 5% of agricultural land contributed, on average, 22% of the total agricultural pollutant load. Pollutant loads from these agricultural CSAs were more than four times greater than the average load from agricultural areas within the watershed. Conservation practices implemented in these areas can be more eff ective because they have the opportunity to treat more pollutant. Th e evaluation of CSAs and prioritized implementation of conservation measures at the watershed scale has the potential to signifi cantly improve the eff ectiveness of state and federally sponsored water quality programs.