EFFECT OF INCREASING COOL-SEASON PRECIPITATION ON GROUNDWATER TEMPERATURE IN MEROKARST ENVIRONMENTS

Climate predictions for the central USA indicate that cool-season precipitation will increase without increase in total precipitation, and average air temperature will rise. Increase in cool-season precipitation is predicted for significant parts of the world’s land masses. Higher annual air temperatures will likely cause rising surface water and groundwater temperatures; these can perturb the local and regional environment, including biological and microbial activity, ecological function, and geochemistry, both mineral precipitation and dissolution reaction rates which can affect porous media properties. Here, we present measured and modeled data examining the role of precipitation timing in changes to groundwater temperature in a carbonate-karst aquifer, using six years of high-frequency measured groundwater level and temperature data from the Konza Prairie Long-Term Ecological Research Site, Kansas, USA. We demonstrate, despite increases in annual air temperature, shifts to increased cool-season precipitation may mitigate the rise in groundwater temperature. In karst, the solution-enlarged conduits allow faster and focused recharge to the water table, and the recharge-event temperature can cause nearly step changes in groundwater temperature. Therefore, predictions of future groundwater conditions in karst aquifers and the streams they feed need to consider changes in precipitation patterns, in addition to changes in average annual air temperature.