IS THE NUBIAN SANDSTONE AQUIFER SYSTEM BEING DEPLETED?
Analysis of the Gravity Recovery and Climate Experiment (GRACE)-derived Terrestrial Water Storage (TWS) inter-annual trends over the NSAS revealed an area of significant TWS depletion (1.3 ± 0.66 × 109 m3/yr) that is correlated with the Dakhla Basin in Egypt. Findings include (1) excessive groundwater extraction, not climatic changes, is responsible for the observed TWS depletion; (2) we estimate that the Dakhla Basin in Egypt, if mined at present extraction rates, could last for a period approaching 4000 years. If, instead, we were to adopt the projected rates of artificial extraction in 2070 (2.8 × 109 m3/yr) and the present natural discharge rates (0.506 × 109 m3/yr), it will be consumed in less than half this period (1500 years), and in an even shorter time period (350 years) if the extraction rates continue to double every 50 years; and (3) observed depletions over the Dakhla Basin and their absence across the remaining segments of the NSAS suggest that the aquifer is at near-steady conditions except for the Dakhla Basin that is witnessing unsteady transient conditions. Implications for applying the methodologies advocated for assessment and optimum management of a large suite of fossil aquifers worldwide are clear.