ARS | Publication request: Evaluation of Hydrologic and Water Quality Impacts of Crop Rotation in the Little River Watershed Using SWAT

Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: October 26, 2007
Publication Date: June 29, 2008
Citation: Cho, J., Lowrance, R.R., Bosch, D.D., Strickland, T.C., Vellidis, G. 2008. Evaluation of Hydrologic and Water Quality Impacts of Crop Rotation in the Little River Watershed Using SWAT [abstract]. ASABE Annual International Meeting.

Technical Abstract: The Soil and Water Assessment Tool (SWAT) has been used for evaluating impacts of conservation practices on hydrology and water quality at watershed scales. However, previous researchers rarely described detailed information on temporal and spatial changes in agricultural managements. In this study, SWAT was evaluated for its applicability in considering temporal impacts of crop rotations within a Coastal Plain Watershed, the Little Liver Watershed in Georgia. Two different approaches for simulating the cropped areas were compared: a default management approach (DMA) scheduled by heat unit (continuous cotton or peanut) and a typical rotation approach (TRA) scheduled by operational date (Cotton -Cotton-Peanut 3-year rotation). The model was calibrated for both approaches using measured daily, monthly, and annual discharge, sediment, and nutrients from 1995 to 2004. Total relative error (RE) and the Nash-Sutcliffe model efficiency (NSE) were used to evaluate model performance. SWAT demonstrated an excellent performance on hydrology with monthly NSE of 0.93 and 0.94 for DMA and TRA, respectively. The corresponding measures for sediment, total nitrogen, and total phosphorus were less than 0.5 in all cases. The poor performance in simulating sediment and nutrients loads was attributed to the poor correlation between measured flow rates and sediment/nutrient loads. The study showed that hydrologic response of SWAT was less sensitive to the detailed temporal rotation input compared to the sediment and nutrient components. The study found that temporal variations in hydrology can be reasonably simulated by DMA but more attention should be paid to the TRA for considering temporal variations in water quality.