Evaluating Groundwater Potential in Arid Regions through Pumping Tests: Insights from the Nubian Sandstone Aquifer, Western Desert of Egypt

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, located in the Western Desert of Egypt, a crucial zone within Egypt’s 1.5 million-feddan reclamation project. Using an extensive dataset from 29 deep pumping wells, we reveal extreme variations in aquifer properties and well performance. Results show that the aquifer has high transmissivity and hydraulic conductivity values, particularly in the western extent of the study area, indicating potential for large-scale agricultural and industrial development projects. Moreover, the storage coefficient at 3x10-5 to 0.13x10-4 shows that the aquifer is a confined aquifer system. However, the spatial variability of aquifer thickness (150 m to 594 m) and local variations of well efficiencies (4 to 80%) and appreciable (+ 80 m to + 115) amount of localized water flow through the aquifer, indicate the risk of over extraction and the necessity to adapt and manage the resource diligently. One of the key findings revealed in this study is that specific capacity (Sc) is a better indicator of well efficiency compared to transmissivity (T). Our study ultimately shows that while regional geological characteristics are essential, it is the local geological settings and wellbore conditions that ultimately determine sustainable water availability. The findings of this study help to understand better how large fossil aquifers respond to high rates of extraction and contribute in a meaningful way to a broader discussion on water security in transboundary aquifer systems.