Comparison of evapotranspiration simulation performance by APEX model in dryland and irrigated cropping systems

Authors: Tadesse, Haile; Moriasi, Daniel; Gowda, Prasanna; Steiner, Jean; TALEBIZADEH, MANSOUR - Orise Fellow; Nelson, Amanda; Starks, Patrick; Marek, Gary

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2019
Publication Date: 5/28/2019
Citation: Tadesse, H.K., Moriasi, D.N., Gowda, P.H., Steiner, J.L., Talebizadeh, M., Nelson, A.M., Starks, P.J., Marek, G.W. 2019. Comparison of evapotranspiration simulation performance by APEX model in dryland and irrigated cropping systems. Journal of the American Water Resources Association. https://doi.org/10.1111/1752-1688.12759.
DOI: https://doi.org/10.1111/1752-1688.12759

Interpretive Summary: Water management is essential to agricultural production in arid and semi-arid regions such as the Texas High Plains located in the United States. Evapotranspiration (ET) accounts for most irrigation water and precipitation in this region. Therefore, it is essential to evaluate ET in order to develop efficient water use agricultural systems. The Agricultural Policy/Environmental eXtender (APEX) is a commonly used hydrologic and water quality model used to predict ET. However, no research has determined how the methods used to compute ET in APEX affect parameters and prediction performance for dryland and irrigated of farming systems. ET and crop yield data measured in the lysimeter fields located in the USDA-ARS, Bushland, Texas were used for this study. The number of parameters that affect ET was higher for dryland (11 to 14) than irrigated cropping system (6 to 8). Overall, it took much shorter computation time to obtain stable parameter values to predict ET well in the irrigated than dryland cropping system, 10 to 276 faster depending on the ET prediction method used. However, when all input data are available, Penman-Monteith ET method would take the shortest computation time to obtain stable parameter values in both dryland and irrigated cropping systems. However, in areas with limited datasets, one can still obtain reasonable ET predictions using either Priestley-Taylor or Hargreaves ET method; but the computation time is 3- to 27-fold greater depending on the method or water management system.

Technical Abstract: Accurate estimation of evapotranspiration (ET) is essential to improving water use efficiency of crop production systems managed under different water regimes. The Agricultural Policy/Environmental eXtender (APEX) model was used to simulate ET using four potential ET (ETp) methods. The objectives were to determine sensitive ET parameters in dryland and irrigated cropping systems and compare ET simulation in the two systems using multiple performance criteria. Measured ET and crop yield data from lysimeter fields located in the USDA-ARS Bushland, Texas were used for evaluation. The number of sensitive parameters was higher for dryland (11 to 14) than irrigated cropping systems (6 to 8). Only five input parameters: soil evaporation plant cover factor, root growth soil strength, maximum rain intercept, and rain intercept coefficient were sensitive in both cropping systems. Overall, it is possible to find a set of robust parameter values to simulate ET accurately in APEX in both cropping systems using any ETp method. However, more computation time is required for dryland than irrigated cropping system due to a relatively larger number of sensitive input parameters. When all inputs are available, the Penman-Monteith method takes the shortest computation time to obtain one model run with robust parameter values in both cropping systems. However, in areas with limited datasets, one can still obtain reasonable ET simulations using either Priestley-Taylor or Hargreaves.