When climate variability partly compensates for groundwater depletion: An analysis of the GRACE signal in Morocco

Abstract

Study region: Morocco, Northwestern Africa. Study focus: Since April 2002, the Gravity Recovery and Climate Experiment (GRACE) mission have opened new pathways for hydrologists to monitor the changes in terrestrial total water storage (TWS). Here, the Center for Space Research (CSR), Goddard Space Flight Center (GSFC), Jet Propulsion Laboratory (JPL), and the average (AVG) GRACE mascon solutions were used to examine the changes in TWS and groundwater storages (GWS) in Morocco, with an emphasis on natural replenishment events and their link to snow cover area (SCA) and rainfall variability. New hydrological insights for the region: The results showed that GRACE TWS from AVG (TWSAVG) and GSFC (TWSGSFC) can fairly describe the temporal patterns of the groundwater level (GWL). Moreover, during 2002–2020, the TWS underwent a strong depletion relatively masked by natural recharge events. This was revealed as we identified two intermittent depletion episodes with statistically significant rates (−1.03 ± 0.11 to −0.31 ± 0.1 cm yr−1) higher than those obtained for the long-term trend lines (−0.28 ± 0.11 to −0.15 ± 0.07 cm yr−1). The TWS appeared to be strongly linked with the SCA metrics and rainfall indices with 1–3 months of lag. Our findings suggest that the rainfall distribution can be more insightful about changes in groundwater levels compared to the rainfall monthly totals.

Keywords

• GRACE
• Groundwater depletion
• Changepoint
• Natural recharge
• GRACE versus climate