Changes in groundwater irrigation withdrawals due to climate change in Kansas

Warming temperatures increase the evapotranspiration demand of crops, leading to an increase in irrigation and exacerbating water scarcity. Previous research relies on models of irrigation water requirements to understand the potential impacts of climate change, but these models have significant uncertainty and ignore the risk-averse behavior of irrigators. Here we develop regression models to estimate how changes in vapor pressure deficit and precipitation affect groundwater withdrawals for corn, soybeans, and wheat using well-level data from the Kansas portion of the High Plains Aquifer. Withdrawals are expected to increase for all three crops, with the largest increase for soybeans. Even after accounting for the CO2 improvements in transpiration efficiency, we find that total withdrawals are expected to increase by 5.9% (7.6%) by mid-century under RCP 4.5 (8.5). The increase in withdrawals is expected to accelerate the decline in aquifer water levels and is therefore important to consider when projecting future aquifer conditions.