3D inversion of magnetic data to delineate subsurface structures controlling groundwater recharge and discharge at Wadi Al-Assiuty, Egypt

Abstract

This study aims to enhance our understanding of groundwater accumulations in the Wadi Al-Assiuty region, with an emphasis on supporting the development of new urban settlements and national industrial initiatives. To achieve this objective, airborne magnetic data were processed and analyzed, enabling the delineating the subsurface structures and their impact on groundwater flow patterns. The research also aimed to assess the aquifer’s thickness within the area. Satellite-based digital elevation data were interpreted to map the primary drainage patterns, highlighting watersheds and basins where surface water tends to accumulate. Additionally, aerial magnetic data were employed to detect the sedimentary cover and evaluate the thickness distribution of the Nubian aquifer, ultimately identifying the most promising aquifer with the highest thickness and greatest potential groundwater reserves.

The magnetic data analysis employed three primary techniques. First, source edge detection was applied to identify sources with varying magnetic intensity anomalies. Second, the depth of the basement surface was calculated, corresponding to the base of the Nubian aquifer in the study area. Third, 3D magnetic data inversion was used to create a three-dimensional model of the basement rocks, aiding in the identification of optimal locations for drilling deep groundwater wells. The overarching goal is to locate areas with strong groundwater exploration potential, which is critical for Egypt’s sustainable development. To ensure accuracy, the results are constrained by incorporating previous geological, geophysical, and drilled wells data.

Wadi Al-Assiuty, a major Egyptian wadi, exhibits a rectangular drainage pattern (angular streams) interspersed with sub-dendritic to subparallel sub-basins, which reflects the structural control of the stream network. The resulting maps, generated through linear transformations and derivative-based techniques, reveal that NW-SE and E-W fault systems play a significant role in controlling the recharge of the aquifers from surface run-off water, the deep Nubian sandstone aquifer, and the Nile River. Notably, the depth to the basement varies widely, ranging from 200 m to 4800 m below the surface. This study aligns with Egypt’s 2030 sustainable development plan, particularly focusing on promising desert areas that could be transformed into agricultural development zones.