Evaluation of Agricultural Practices and Irrigation Scheduling on Water Resources, Southwestern Kansas

Abstract

The effects of selected agricultural land-management practices, major crops, and irrigation schedules on basinwide water resources are assessed using the SWAT model. Six different crops are simulated and different runoff curve numbers are utilized to represent different land-management practices. Five different water stress factors are used to represent five irrigation scheduling scenarios. The simulation results show that both irrigation scheduling and conservation practices have significant effects on surface runoff and groundwater recharge. For a given conservation practice the mean annual surface runoff and groundwater recharge increase with the increase of irrigation frequency (less stressed conditions). For a given irrigation schedule (same stress factor) the mean annual groundwater recharge increases with the increase of efficiency of conservation practices. On the other hand, the mean annual surface runoff decreases with the increase of efficiency of conservation practices. However, the mean annual irrigation depth, evapotranspiration, and soil water content are relatively independent of the conservation practices and are dependent more on the irrigation schedules. Under the same conservation practice (SCS curve number = 60) and irrigation schedule (water stress factor (WSF) = 0.5), wheat produces the highest mean annual surface runoff and groundwater recharge along with the highest soil water content, the lowest irrigation requirement and the lowest evapotranspiration. Corn, on the other hand, has the lowest mean annual surface runoff, groundwater recharge, and soil water content, along with the highest irrigation requirement and the highest evapotranspiration.