Climate change has the potential to impact groundwater availability in several ways. For example, it may cause farmers to change the crops they plant or the amount of water they apply, both of which have implications for water availability. Climate change also affect water availability directly by changes in precipitation and evapotranspiration patterns. In this paper, we analyze the effects of changes in temperature, precipitation, and humidity on groundwater extraction for agriculture using an econometric model of a farmer’s irrigation water pumping decision that accounts for both the intensive (water use) and extensive margins (crop acreage). Our research focuses on the groundwater used for agriculture in the High Plains (Ogallala) Aquifer system of the Midwestern United States. We find that changes in climate variables will influence crop selection decisions, crop acreage allocation decisions, technology adoption, and the demand for water by farmers. We also find that such changes in behavior can affect the diversity of crops planted, potentially impacting agricultural biodiversity.