CALIBRATION, REFINEMENT, AND APPLICATION OF THE WEPP MODEL FOR SIMULATING CLIMATIC IMPACT ON WHEAT PRODUCTION

Agricultural system models are useful tools for tailoring agricultural production systems to possible climate variations. The objectives of this work were: (1) to evaluate and calibrate the water balance and crop components of the Water Erosion Prediction Project (WEPP) model and to make improvements if necessary, and (2) to simulate hydrologic and crop responses to generated climate scenarios for winter wheat (Triticum aestivum L.). Precipitation, surface runoff, soil moisture, and wheat biomass collected between 1980 and 1996 on a 1.6 ha watershed near El Reno, Oklahoma, were used. Two contrasting (wet and dry) climate scenarios were generated using a climate generator (CLIGEN) for assessing the overall sensitivity of WEPP to climate variations. Optimized saturated hydraulic conductivity (Ks) agreed well with field-measured Ks, indicating that the infiltration routine of the model functioned properly. WEPP’s original water use function substantially overpredicted plant water uptake and therefore was modified. The revised water use function resulted in better predictions of soil water balance, plant water stress, and biomass production. Predicted aboveground biomass agreed relatively well with measured data (model efficiency = 0.5). However, wheat grain yields were less well predicted because of inadequate adjustments to harvest index in the model. The general relationship between total aboveground biomass and growing-season evapotranspiration for winter wheat was reasonably simulated by the model. Model simulations under the generated wet and dry scenarios showed that each percent increase in growing-season precipitation would result in, on average, 3.38%, 0.34%, 0.73%, 1.09%, and 0.81% increases in surface runoff, plant transpiration, soil evaporation, deep percolation, and wheat grain yield, respectively, under the study conditions. This work has shown that WEPP is capable of simulating hydrologic and crop responses to climate variations.

[1]  Joe T. Ritchie,et al.  Model for predicting evaporation from a row crop with incomplete cover , 1972 .

[2]  C. W. Richardson,et al.  Microcomputer Program for Daily Weather Simulation in the Contiguous United States , 2018 .

[3]  Clayton L. Hanson,et al.  Stochastic Weather Simulation: Overview and Analysis of Two Commonly Used Models , 1996 .

[4]  Graeme L. Hammer,et al.  Advances in application of climate prediction in agriculture , 2001 .

[5]  John R. Williams,et al.  EPIC-erosion/productivity impact calculator: 1. Model documentation. , 1990 .

[6]  J. Garbrecht,et al.  VARIABILITY OF SELECTED SOIL PROPERTIES IN WINTER WHEAT AND NATI VE GRASS WATERSHEDS , 2001 .

[7]  Jurgen D. Garbrecht,et al.  EVALUATION OF CLIGEN PRECIPITATION PARAMETERS AND THEIR IMPLICATION ON WEPP RUNOFF AND EROSION PREDICTION , 2003 .

[8]  Shu Tung Chu,et al.  Infiltration during an unsteady rain , 1978 .

[9]  K. C. McGregor,et al.  Evaluation of WEPP Runoff And Soil Loss Predictions Using Natural Runoff Plot Data , 1996 .

[10]  Xunchang Zhang,et al.  CLIGEN NON-PRECIPITATION PARAMETERS AND THEIR IMPACT ON WEPP CROP SIMULATION , 2004 .

[11]  E. E. Alberts,et al.  Chapter 8. PLANT GROWTH COMPONENT , 1995 .

[12]  Xunchang Zhang,et al.  ASSESSING SEASONAL CLIMATIC IMPACT ON WATER RESOURCES AND CROP PRODUCTION USING CLIGEN AND WEPP MODELS , 2003 .

[13]  J. Monteith.  Climate and the efficiency of crop production in Britain , 1977 .

[14]  James Hansen,et al.  Realizing the potential benefits of climate prediction to agriculture: issues, approaches, challenges , 2002 .

[15]  Bruce N Wilson,et al.  Evaluation of stochastic weather parameters for Minnesota and their impact on WEPP , 1997 .

[16]  J. Williams,et al.  Chapter 5. WATER BALANCE AND PERCOLATION , 1995 .

[17]  C. W. Richardson,et al.  Microcomputer Program for Daily Weather Simulation , 1985 .

[18]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[19]  L. J. Lane,et al.  Chapter 2. WEATHER GENERATOR , 1995 .