|Evett, Steven - Steve|
|HOWELL, TERRY - Retired ARS Employee|
|MAREK, THOMAS - Texas Agrilife Research|
|Baumhardt, Roland - Louis|
|SRINIVASAN, R - Texas A&M University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/1/2014
Publication Date: 4/7/2014
Citation: Marek, G.W., Gowda, P., Evett, S.R., Howell, T.A., Brauer, D.K., Marek, T.H., Moriasi, D.N., Baumhardt, R.L., Srinivasan, R. 2014. Calibration and validation of the SWAT model for predicting daily ET for irrigated crops in the Texas High Plains using lysimetric data. ASABE Paper No. 1872959.
Technical Abstract: The Soil and Water Assessment Tool (SWAT) model has been used to assess the impacts of alternative agricultural management practices on non-point source pollution in watersheds of various topography and scale throughout the world. Water balance is the driving force behind all processes of SWAT, as it impacts plant growth and the movement of sediments, nutrients, pesticides, and pathogens. As the major component of consumptive water use, evapotranspiration (ET) is perhaps the most important parameter in the water budget. Limited studies were performed to calibrate and validate the ET parameter within the SWAT modeling environment during the early stages of model development. The objective of this study was to calibrate and validate the SWAT model for predicting ET for major irrigated crops grown in the Texas High Plains. Long-term (2000-2010) daily ET data from two large weighing lysimeters managed by the USDA-ARS Conservation and Production Laboratory under irrigated conditions were used for this purpose. The lysimeter data for the first year (2000) were used as a model warm up period. The remaining lysimeter data were divided equally for calibration (2001-2005) and validation (2006-2010) for predicting daily ET. Comparison of predicted daily ET against observed data during the calibration period gave an r square value of 0.70 with a slope of 0.81 and an intercept of -0.03 mm per day. However, the RMSE was 68% (1.6 mm per day) of the observed daily ET with a Nash-Sutcliffe efficiency of 0.60. This is partly due to overprediction of ET during the year 2001. Similar performance was observed during the validation period, however, with an improved Nash-Sutcliffe efficiency of 0.74. Future work includes evaluating the SWAT model for its ability to predict irrigation requirements and water content in the soil profile.