SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Simulating climate change effects in a Minnesota agricultural watershed 
Authors:Hanratty, M.P. and H.G. Stefan 
Journal:Journal of Environmental Quality 
Volume (Issue):27 
Article ID: 
URL (non-DOI journals): 
Broad Application Category:hydrologic and pollutant 
Primary Application Category:climate change 
Secondary Application Category:pollutant cycling/loss and transport 
Watershed Description:3,400 km^2 Cottonwood River, located in western Minnesota, U.S. 
Calibration Summary:Monthly (1967-91): streamflow E = .78 sediment E = .59 nitrate E = .68 total P = .54 org. N (& ammonia) = .57 
Validation Summary: 
General Comments:The impact of a single 2xCO2 climate change scenario (CCC CGM) is reported. Decreases in streamflow, total P, organic N/ammonia, nitrate/nitrite, and sediment yield were found relative to baseline conditions. However, the climate change effects were not "measurable" sediment and nitrate/nitrite, because the corresponding baseline standard errors were too high. 
Abstract:The effect of climate change on quality and quantity of runoff from a northern, agricultural watershed (in Minnesota, USA) was simulated using the Soil and Water Assessment Tool, 1996 Version (SWAT96). SWAT's snow evaporation submodel was modified. SWAT was calibrated using water quality and quantity data measured in the Cottonwood River (drainage area: 3400 kmsuperscript 2). The standard errors after calibration were 3.31 mm, 157 kg/d, 752 kg/d, 3744 kg/d, and 85 t/d for mean monthly streamflow, P yield, ammonia (NH3)/organic N yield, nitrate (NO3) yield, and sediment yield, respectively. The standard error for monthly streamflow was 9.62 mm. SWAT96 was then used to simulate the effect on the Cottonwood River watershed of a 2x CO2 climate scenario. Assuming land cover and land management remained constant, SWAT96 projected a decrease in mean annual streamflow, P yield, NH3/organic N yield, NO3/nitrite (NO2) yield, and sediment yield. Mean monthly values changed significantly for many months of the year under the 2x CO2 climate scenario. The standard errors in SWAT's baseline simulations, however, were too high for the simulated climate change effects to be measurable for NO3/NO2 and sediment yields. The model assumptions and calibration methods used to obtain the accuracy required for simulating the effects of climate change lead to the conclusions that land use/land cover and land management practices are likely to have a greater impact on water quality than climate change and that SWAT must be calibrated to be used for climate change analysis.