CMIP6 multi-model projections of the groundwater response to climate change during the 21st century

<p><span>Climate change will impact every component of the climate system and</span><span> water cycle. </span><span>It does </span><span>not spare </span><span>groundwater which</span> <span>account for approximately one third of the human fresh water withdrawals.</span> <span>The combined effect of climate change and groundwater pumping </span><span>could lead to water scarcity and food insecurity in some regions. Therefore, </span><span>it is essential to study </span><span>the groundwater response to climate change to improve t</span><span>he </span><span>development of </span><span>adaptation </span><span>and mitigation plans in water management.</span></p><p>Here, <span>w</span><span>e</span> <span>analyze the </span><span>response of groundwater recharge </span><span>to climate change using an ensemble of </span><span>simulations runs with 22 </span><span>fully coupled </span><span>ocean-atmosphere-land models</span> <span>participating </span><span>to</span><span> the CMIP6 exercise. </span><span>The</span><span>y</span><span> are run from 1850 to 2100 and follow four of the latest IPCC scenarios </span><span>of greenhouse gas future evolution</span><span>. This analysis is supplemented with the assessment of the </span><span>climate-driven </span><span>response of groundwater </span><span>level given by the CNRM global climate mode</span><span>l</span><span>s (which are part of the CMIP6 </span><span>exercise</span><span>).</span> <span>These models</span><span> r</span><span>epresent</span> <span>the </span><span>hydrogeological</span><span> processes involving </span><span>groundwater,</span><span> including</span> <span>the </span><span>t</span><span>wo-way water exchanges with rivers and the unsaturated soil, </span><span>the </span><span>lateral groundwater fluxes, </span><span>and </span><span>the </span><span>interaction</span><span>s</span><span> with </span><span>the </span><span>atmosphere</span><span>. </span><span>R</span><span>esults show that</span> <span>on global average, </span><span>groundwater recharge</span> <span>is</span><span> expected </span><span>to</span> <span>increase </span><span>with climate change</span><span>. </span><span>T</span><span>h</span><span>e</span> <span>changes in groundwater recharge follow </span><span>those of </span><span>precipitation </span><span>and, </span><span>to a lesser extent,</span><span> evapotranspiration </span><span>and thus </span><span>follow the same </span><span>regional </span><span>patterns</span><span>. </span></p><p><span>A</span><span>s the</span><span>se</span> <span>CMIP6 </span><span>models do not represent </span><span>human</span> <span>groundwater withdrawals, t</span><span>he projected changes </span><span>in recharge are </span><span>somewhat </span><span>optimistic and could be out of step in regions with strong </span><span>groundwater pumping</span><span>. </span><span>T</span><span>o address this limitation, </span><span>results are put in perspective with</span><span> projections of water withdrawals following the CMIP6 experiments. This analysis shows the </span><span>combined effects of climate change and </span><span>groundwater </span><span>pumping on </span><span>groundwater</span> <span>and </span><span>help to</span><span> understand the evolution of the future large scale water resource.</span></p>