Groundwater, stored in permeable geological structures (aquifers), constitutes the largest unfrozen reserve of freshwater on Earth. It amounts to approximately 35% of human fresh water withdrawals (Doll et al., 2012) and sustains ecosystems by supplying baseflow during dry periods. The recharge of aquifers stems mainly from rainfall, melted snow, and water exchanges with inland water bodies. Conversely, groundwater sustains these bodies of water and is the main driver of river flow. To a lesser extent, it also contributes to evapotranspiration in groundwater-dependent ecosystems. In addition to these natural water fluxes, pumping and soil infiltration of irrigation water also affect groundwater levels. The evolution of groundwater resources with climate change is therefore of great importance for both humankind and natural ecosystems.As climate change modify the natural hydrological cycle as well as human water use and demand, it also affect groundwater resources (
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. This signal presents large regional disparities which mostly match the patterns of precipitation changes. As the climate models we used do not simulate human groundwater withdrawals (irrigation as well as domestic and industrial uses) which represent the other main driver of groundwater levels evolution, we also use FAO maps of present-day irrigated areas and projections of population in 2100 to identify regions where groundwater withdrawals could exacerbate the projected depletion, or even reverse a projected rise into a depletion. Depending on the scenario, we then find a rise (respectively a depletion) of groundwater levels in 2100 over 33[28-39]% to 42[41-45]% (respectively 26[25-32]% to 37[36-40]%) of the area covered by the 218 world’s major groundwater basins. And 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 (for 29[27-33]% to 40[39-40]% of the population), or increased risks of flooding (for 1.7[1.5-2.2]% to 2.2[2.2-2.4]% of the population).
<p>Groundwaters found in aquifers play an important role in the hydrological cycle and are essential for human activities and for natural ecosystems. They account for approximately one third of the human fresh water withdrawals and sustain ecosystems by supplying soil moisture during dry periods. Climate change will impact every components of the climate system and aquifers are no exception. Precipitation is the main driver of groundwater recharge and relatively shallow aquifers respond rather quickly to changes in the precipitation rates. Thus, climate change should have an impact on water table depths and could lead to water scarcity and food insecurity in some regions. Therefore, knowing the response of the aquifers to climate change is important to improve the development of mitigation and adaptation plans in water management.&#160;</p><p>Here, the response of unconfined shallow aquifers to climate change is assessed at the global scale using the global climate model developed in our institute (CNRM) : CNRM-CM6 and CNRM-ESM2. We analyse simulations conducted for the Coupled Model Intercomparison Project 6 (CMIP6) following four pathways of greenhouse gas concentrations until 2100. The CNRM models are the only global climate models representing the physicals processes involving aquifers. Results show that aquifers should replenish at the global scale on average, which is consistent with the projected global intensification of precipitation. However, the evolution of water table depths is not uniform and presents large regional disparities. Additionally to climate change, anthropogenic impacts like intensive groundwater withdrawals for agricultural, domestic and industrial purposes should exacerbate the depletion in some aquifers basins. In order to identify these regions, the evolution of the water table depths is compared with the population density. This analysis highlights the widening risk of water stress in some already aquifer-dependant regions.</p>
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.