Climate sensitivity of groundwater recharge

Groundwater recharge is fundamental to supporting sustainable groundwater use for both ecosystems and human water withdrawals. Rates of recharge, and how these rates are affected by climate change, remain poorly constrained due to uncertain models and limited recharge measurements. We develop an emerging relationship between measurements of recharge and climatic aridity. This relationship suggests that recharge tends to be most sensitive to climatic changes in regions where potential evapotranspiration slightly exceeds precipitation. In these regions, even modest aridification can significantly reduce groundwater recharge. Future climate-driven changes in recharge are likely to be primarily influenced by shifts in precipitation, with groundwater recharge typically responding more strongly than the precipitation changes themselves. Measurements of recharge are more sensitive to variations in aridity than recharge simulated by several global hydrological models is. As a result, the impacts of climate change on groundwater replenishment and the sustainability of groundwater use for humans and ecosystems are likely greater than previously estimated.