Abstract
As groundwater found in aquifers is the main reservoir of freshwater for
human activity, knowledge of the future response of groundwater to
climate change is key for improving water management adaptation plans.
We analyse the climate-driven evolution of future levels of unconfined
aquifers in the 218 world’s major groundwater basins in global climate
simulations following the latest IPCC scenarios, run with models able to
capture feedbacks among climate, land use and groundwater. We find a
rising of groundwater levels on global average, which is consistent with
the projected global intensification of precipitation. However, the
evolution of water table depths is not spatially uniform and presents
large regional disparities. Depending on the scenario, we find a
statistically significant rise (respectively a depletion) of groundwater
levels in 2100 over 40[34-47]% to 52[50-54]% (respectively
20[19-24]% to 26[25-29]%) of the area covered by the 218
world’s major groundwater basins. Using spatialiazed projections of
population in 2100, we estimate that 31[29-36]% to 43[42-44]%
of the world’s population could be affected by these groundwater
changes, facing either water scarcity issues, or increased risks of
flooding. As the climate models we used do not represent human
groundwater withdrawals (irrigation as well as domestic and industrial
uses), we also use FAO maps of present-day irrigated areas and
projections of population to identify regions where groundwater
withdrawals could exacerbate the projected depletion, or even reverse a
projected rise into a depletion.