Changes in mean evapotranspiration dominate groundwater recharge in semi-arid regions

Groundwater is one of the most essential natural resources and is affected by climate variability. However, our understanding of the effects of climate on groundwater recharge (GR), particularly in dry regions, is limited. Future climate projections suggest changes in many statistical characteristics of the potential evapotranspiration (ETref) and the rainfall that dictates the GR. To better understand the relationship between climate statistics and GR, we separately considered changes to the mean, STD, and extreme statistics of the ETref and the rainfall. We simulated the GR under different climate conditions in multiple semi-arid locations worldwide. We find that changes in the average ETref have the most significant impact on GR. Interestingly, we find that changes in the extreme ETref statistics have much weaker effects on the GR than changes in extreme rain statistics. Contradictory results of previous GR studies may be explained by the differences in the projected climate statistics.