Geophysics and remote sensing applications for groundwater exploration in fractured basement: A case study from Abha area, Saudi Arabia

Abstract Groundwater can be the only salvation in arid or semi-arid mountainous areas , especially for those covered by basement rocks. The fractured groundwater aquifers are characterized by a lack of extension in all directions and the distribution of the main fractured and shear zones. An integrated approach of satellite remote sensing and geophysical techniques was used to investigate groundwater occurrence in the fractured aquifers of the mountainous area north of Abha city. A digital elevation model (DEM) was used to extract the streamlines and determine the eastward direction of the surface water flow. The average annual precipitation over the study area shows a positive increase trend estimated at 156 mm yr-1 based on Tropical rainfall measuring mission (TRMM) data during the 2002–2018 period. Seven vertical electrical soundings (VES) using Schlumberger array and twelve time-domain electromagnetic soundings (TEM) using an induction loop with size 50 by 50 m were conducted to detect accumulated groundwater in irregular shape pockets within the fractured basement rocks of the area. VES's and TEM indicate the occurrence of water saturation zones at depths varying from 45 to 60 m. The thickness of the saturated zone exceeds 100 m in some parts, extending toward the northeast-southwest direction parallel to the fractures and faults. The integrated approach provides a reliable study to better understand the groundwater occurrence in fractured basement aquifers.