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Assessing Seasonal Climatic Impact on Water Resources and Crop Production Using CLIGEN and WEPP Models

Zhang, X.C.
Transactions of the ASAE 2003 v.46 no.3 pp. 685–693
water resources, crop production, climatic factors, stochastic processes, weather, hydrologic models, climate models, grain yield, precipitation, simulation models, wet environmental conditions, dry environmental conditions, runoff, soil water, wheat, seasonal variation, Oklahoma
Physically based response models are useful tools for assessing climatic impact on water resources and crop productivity. Most response models require daily weather, which is often synthesized using stochastic daily weather generators. Synthesis of climate scenarios using weather generators provides an effective means for making impact assessments. The objectives were to evaluate the ability of the CLIGEN model to generate various climate scenarios and to assess further the hydrological and crop productivity responses using the WEPP model. The CLIGEN model was evaluated at four Oklahoma weather stations with mean annual precipitation ranging from 420 to 1150 mm and was then used to generate typical climate scenarios that represent wet, dry, and average conditions for Chandler, Oklahoma. The WEPP model was used to simulate hydrologic and grain yield responses to the generated climate scenarios. Results show that CLIGEN simulated daily and monthly precipitation reasonably well. CLIGEN was capable of preserving statistics of monthly precipitation as well as reproducing seasonal precipitation patterns for the dry, average, and wet year conditions. Simulated surface runoff, deep percolation, and plant transpiration increased as precipitation increased, but the rates of the increase varied with initial soil moisture levels and total precipitation. Predicted percent increase of wheat grain yield per 1% increase of growing-season precipitation, which was a function of initial soil moisture and total precipitation, ranged from 0.5% to 0.75%. Overall results indicate that CLIGEN is capable of translating monthly climate forecasts into daily weather series while preserving statistics of the forecasts. This study demonstrates that CLIGEN, when used in conjunction with response models such as WEPP, provides a useful tool for assessing the impact of seasonal climate variations or forecasts on water resources and crop production.