Assessing the effectiveness of irrigator-driven groundwater conservation programs to drought: a case study of the northwestern Kansas Local Enhanced Management Areas

Groundwater pumping for irrigation has led to significant decreases in groundwater levels in agricultural areas around the world, including the U.S. High Plains Aquifer. Here, we used a process-based corn and sorghum crop model, AquaCrop, to assess the effectiveness of different irrigation management strategies during a synthetic multi-year drought. We focused on the Groundwater Management District 4 Local Enhanced Management Area (GMD-4 LEMA), a regional groundwater conservation program in the northwestern Kansas portion of the High Plains Aquifer. We first calibrated the AquaCrop models to observed yield and irrigation using the Particle Swarm Optimization algorithm, and then applied a novel difference-based bias correction method to improve performance. We found that the corn models outperformed the sorghum models, likely due to limited observational sorghum data. However, both models performed satisfactorily during drought periods. We then evaluated the effectiveness of the groundwater conservation program, defined as the ability to reduce water use, during a synthetic five-year drought under three irrigation strategies. During the synthetic drought, corn irrigation requirements were double those of sorghum, but even simulated corn irrigation needs were generally less than current water allocations. Model simulations also indicated that water conservation strategies could reduce annual irrigation requirements without a substantial reduction in crop yield through improved water use efficiency. Consistent with previous work, this indicates that the current GMD-4 LEMA water allocations are ineffective for conserving water.