Modeling long-term water use of irrigated cropping rotations in the Texas High Plains using SWAT

The Ogalalla Aquifer is used to supplement insufficient precipitation for agricultural production in the semiarid Texas High Plains. However, decades of pumping combined with minimal recharge has resulted in decreased well capacity in most areas. A calibrated Soil and Water Assessment Tool (SWAT) model was used to compare simulated yields, crop water use, and required irrigation for crop rotations of the region using measured long-term (90 years) historical weather data. Crop rotations included continuous corn and cotton, corn-cotton, sorghum-cotton, cotton-winter wheat, and corn-winter wheat. Results demonstrated that a calibrated SWAT model simulated crop water use and yields well for all listed crops except cotton. The plant growth algorithms in SWAT appear unable to simulate representative cotton yields typical of cotton management in the Texas High Plains. A work-around for a limitation of the auto-irrigate function in SWAT to be suspended during the dormancy period of winter wheat was also used. Summary statistics for crop yield, crop water use, and irrigation were presented for all rotations. Long-term water use of simulations and irrigation probability exceedance statistics are presented for all simulated crops. These data may serve as a decision support tool for producers considering crop rotation strategies.