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

摘要

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 K{sub}s, 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.