CLIMATE CHANGE IMPLICATIONS FOR IRRIGATION AND GROUNDWATER IN THE REPUBLICAN RIVER BASIN, U.S.A

This study investigates the influence of climate change on groundwater availability, and thereby, irrigation across political boundaries within the United States’ High Plains aquifer. A regression model is developed to predict changes in irrigation according to predicted changes in precipitation and temperature from a downscaled dataset of 32 general circulation models (GCMs). Precipitation recharge changes are calculated with precipitation-recharge curves developed for prognostic representations of precipitation across the Nebraska-Colorado-Kansas area and within the Republican River Basin focal landscape. Irrigation-recharge changes are scaled with changes in irrigation. The groundwater responses to climate forcings are then simulated under new pumping and recharge rates using a MODFLOW groundwater flow model. Results show that The simulation results suggest that in response to climate change: 1) water stress in the irrigation season will be exaggerated due to increased irrigation water demands; 2) recharge will increase in the non-irrigation season; 3) groundwater levels will decline more in areas with declining trends in the baseline; and 4) baseflow will increase because of increased groundwater recharge in the Republican River valley. The methodologies and predictions of this study can inform long-term water planning and the design of management strategies that help avoid and resolve water-related conflicts, enabling irrigation sustainability.