Wouter Berghuijs , Elco Luijendijk , Christian Moeck , Ype Van der Velde , Scott Allen 

Groundwater is an invaluable global resource, but its long-term viability as a resource for consumption, agriculture, and ecosystems depends on precipitation recharging aquifers. How much precipitation recharges groundwaters varies enormously across Earth's surface, but recharge rates are uncertain because field observations are sparse and modeled global estimates remain largely unvalidated. Here we show that recharge is predictable as a simple function of climatic aridity — the ratio of long-term potential evapotranspiration to precipitation — using a global synthesis of measured recharge of 5237 sites across six continents. We use this relationship to estimate long-term recharge globally outside of permafrost regions. Our estimates double previous global estimates and are more consistent with empirical observations. These revised higher estimates of global groundwater recharge imply that much more groundwater must contribute to evapotranspiration and streamflow than previously represented in global water cycle depictions or global hydrological and Earth system models.