Managing non-renewable groundwater from transboundary fossil aquifers is a critical global challenge for achieving water and food security in arid regions. While these aquifers are often modeled at a regional scale, sustainable extraction hinges on understanding local-scale heterogeneity, which can jeopardize large-scale agricultural projects. This study investigates the significant spatial variability of the Nubian Sandstone Aquifer in the Sahl Baraka area, El Farafra Oasis, Egypt, a crucial zone within the nation’s 1.5 million-feddan reclamation project. Using an extensive dataset from 29 deep pumping wells, we characterized the aquifer’s properties and performance. The findings initially show promising conditions: high values of transmissivity and hydraulic conductivity, especially in the eastern extent of the study area, indicate significant potential for large-scale agricultural and industrial development. The storage coefficient (3 × 10− 5 to 0.13 × 10− 4) also confirms that the aquifer is ‘confined’. However, this potential is complicated by the extreme spatial variability we encountered. We observed dramatic variations in aquifer thickness (150 m to 594 m) and highly inconsistent efficiencies (4% to 80%) of local observed wells. Combined with considerable localized flow (pumping effectively occurred from + 80 m to + 115 m), these results indicate substantial risk associated with significant over-extraction and the need for active stewardship of the resource. A methodological finding was that in such heterogeneous settings, Specific Capacity (Sc) is a more practical diagnostic tool for well efficiency than transmissivity (T), as seen in its strong negative correlation with the well loss coefficient (C) (R² = 0.706). Overall, our study reveals that while regional scale geological characteristics are essential, it is the local geological characteristics and conditions of the wellbore define sustainable water availability. Findings shed considerable light on how large fossil aquifers respond to high rates of extraction, providing important localized data to contribute to the comprehensive discussion at regional scales on water security related to transboundary aquifer systems.
Mourad et al. (Mon,) studied this question.