Delineation of shallow groundwater potential zones using integrated hydrogeophysical and topographic analyses, western Saudi Arabia

Abstract

Groundwater potentiality mapping is currently receiving more attention, particularly in arid regions, where natural freshwater resources are limited and scarce and instead costly unconventional methods such as seawater desalination are widely used to satisfy water demands. Water demand in Makkah city is considered a vital task, which receives millions of visitors every year for religious purposes. The present study evaluates the potential zones of groundwater in the southwest Makkah city applying hydrogeophysical modeling approach that integrates geoelectrical resistivity in form of vertical electrical sounding (VES), ground-penetrating radar (GPR), and topographic analyses. VES results indicate five main geoelectric layers: (1) dry wadi-fill deposits with a true resistivity varying from 73 to 650 Ohm.m and average thickness of 3.14 m, (2) partially saturated sands with a resistivity range between 19 and 43 Ohm.m and average thickness of 13 m, (3) water-bearing layer of saturated sands with a resistivity range between 55 and 110 Ohm.m, and average thickness of 52 m, (4) highly fractured diorite rocks with resistivity values ranging from 750 to 1450 Ohm.m and average thickness of 1.5 m, and (5) fresh diorite basement rocks with a resistivity of more than 4000 Ohm.m. Results of GPR profiles support the gained results of the VES technique, and together they are confirmed by the wells data. The integrated results suggest a structural control on the groundwater accumulation and call for a detailed mapping of alluvium-covered faults to provide a high-resolution mapping of groundwater occurrences and ensure environmental sustainability in southwest Makkah city.