Monitoring groundwater and terrestrial water storage with GRACE/GRACE-FO across MENA and the Gulf Cooperation Council countries: A regional review

Study region This review focuses on the Middle East and North Africa (MENA) and the Gulf Cooperation Council (GCC) countries as the primary regional evidence base. Nile Basin, Mediterranean, and South-Central Asian arid/semi-arid studies are used only as methodological benchmarks where they share comparable water stress, groundwater-use conditions, and GRACE-scale basin characteristics. Study focus We synthesize GRACE (2002–2017) and GRACE Follow-On (GRACE-FO, 2018–present) applications for terrestrial water-storage anomalies (TWSA), groundwater-storage anomalies (GWSA), basin water-budget closure, downscaling, reconstruction, and decision-oriented groundwater monitoring. The review is based on 274 screened records and a coded core set of 73 studies, of which 58 were used in structured regional evidence maps. The manuscript cites 63 references overall, including methodological, product, and benchmark references. Selection, coding, and evidence-strength ratings follow a PRISMA-informed workflow. This review provides a region-centered, uncertainty-aware synthesis rather than a new basin-scale retrieval. New hydrological insights for the region Across MENA/GCC case studies, the strongest evidence indicates basin-integrated TWSA/GWSA decline in intensively managed aquifers, but inference strength varies with basin size, product lineage, leakage/scaling treatment, component separation, validation data, and reference-period choices. We propose minimum reporting and validation requirements for decision-ready GRACE-based groundwater assessment, including product disclosure, anomaly-baseline definition, leakage/scaling correction, TWSA-to-GWSA partitioning, uncertainty propagation, and independent validation using wells, discharge, altimetry, GNSS/InSAR, or documented water-use data.