Global depletion of groundwater resources

In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provide a global overview of groundwater depletion (here defined as abstraction in excess of recharge) by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater abstraction. Restricting our analysis to sub-humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (\textpm32) km3 a-1 in 1960 to 283 (\textpm40) km3 a-1 in 2000. The latter equals 39 (\textpm10)\% of the global yearly groundwater abstraction, 2 (\textpm0.6)\% of the global yearly groundwater recharge, 0.8 (\textpm0.1)\% of the global yearly continental runoff and 0.4 (\textpm0.06)\% of the global yearly evaporation, contributing a considerable amount of 0.8 (\textpm0.1) mm a-1 to current sea-level rise.