A global analysis of groundwater recharge for vegetation, climate, and soils

Authors: Kim, JH, RB Jackson

Because ground water is an essential resource for people and for ecosystems, a better understanding is needed for the fundamental controls on recharge and its interactions with vegetation change. We analyzed >600 estimates of groundwater recharge and deep drainage (as a proxy for recharge) to obtain the first global analysis of recharge and vegetation types. We used a regression model with the following predictors: vegetation type, water input (WI=precipitation+ irrigation), potential evapotranspiration (PET), saturated hydraulic conductivity based on soil texture (Ks), and seasonality of rainfall. Globally, croplands had the highest proportion of WI that became recharge of all vegetation types, followed by grasslands, woodlands, and scrublands (average proportional recharge: 0.11, 0.08, 0.06, and 0.05, respectively; P<0.0001). For individual factors in a stepwise regression, WI had the strongest association with recharge overall (R2=0.29; P<0.0001), followed by vegetation type (R2=0.16; P<0.0001), PET (R2=0.12; P<0.0001), and Ks (R2=0.06; P<0.0001). Recharge increased with WI, Ks, and the seasonality of rainfall and decreased with PET. Relative differences in recharge between vegetation types were larger in drier climates and in clayey soils, indicating greater biological control on soil water fluxes under these conditions. To test our global model with estimates of recharge using paired land-use changes, we compared our global synthesis data to parallel field estimates of recharge that we made in paired grasslands, croplands, and woodlands across the Argentinean Pampas and the southwestern United States. Our field estimates of recharge were similar to, and followed the same pattern of, recharge under vegetation types in the synthesis data, suggesting land-use changes will continue to alter recharge dynamics and vadose zone processes globally. The effects of vegetation on recharge presented here highlight the implications of land-use management for sustainable groundwater use and should also help test and improve recharge estimates in large-scale water balance and climate models.
vzj2012.pdf