Response of Global Aquifers to Climate Changes

Global aquifer systems are expected to have different response to climate variability. In this study, we examined the magnitude and the lag of correlation between aquifers' terrestrial water storage (TWS) and rainfall data. Thirty-seven global aquifer systems distributed over tropical, continental, temperate, and arid climate zones were examined. Monthly TWS and rainfall data were extracted from GRACE/GRACE-FO and GPCP data, respectively, during the period from 2002 and 2022. Cross-correlation preliminary results indicated that: (1) a high positive (r: 0.63-0.85; p-value:<0.01) correlation was observed between TWS and rainfall data at a lag of 1-2 months over aquifers located in tropical zones, (2) a moderate positive correlation (r: 0.27 - 0.60; p-value:<0.01) was observed between TWS and rainfall data at a lag of 4-9 months over aquifers located in continental zones, (3) weak positive (r: 0.10 - 0.44; p-value: 0.16 - <0.01) and negative (r: -0.06 - -0.20; p-value: 0.40 - :<0.01) correlations between TWS and rainfall estimates were observed over aquifers located in arid regions at a lag ranging from 1 to 9 months, (4) a moderate positive correlation (r: 0.33-0.45; p-value: <0.01) was observed between TWS and rainfall estimates for aquifers located temperate regions at a lag of 1-7 months, and (5) difference in aquifers' response, as indicated by correlation and lag values, could be attributed to different rates of groundwater abstraction as well as evapotranspiration rates over each aquifer system. Results of this study could help developing sustainable management scenarios for global aquifer systems.