Use of electrical resistivity tomography in delineating zones of groundwater potential in arid regions: a case study from Diriyah region of Saudi Arabiaاستخدام الشكل السطحي للمقاومة الكهربية في تحديد نطاقات المياة الجوفية فيالمناطق الجافة: دراسة لمنطقة الدرعية –المملكة العربية السعودية

A detailed geophysical investigation in the form of electrical resistivity tomography (ERT) was carried out using the SYSCAL Pro Unit at two locations with a dipole–dipole configuration in one of the private farms in Diriyah area of Riyadh, Saudi Arabia with the purpose of delineating the approximate depth of the water-bearing formations. The survey helped in delineating a superficial moist zone at the first site which was mainly due to the seepage from surface water pipes used for irrigating the date palms. At the second site, a potential water-bearing zone was detected starting from a depth of 23 to 46 m. However, an already existing bore well in close vicinity of the site of the second survey showed a water table depth of 85 m, indicating the presence of a layered aquifer. Finally, it was concluded that a shallow bore well drilled up to a depth of 50–60 meters would be able to tap the water resources of shallow water-bearing horizon discovered at the second site during the survey; however, the yield of the bore well might not be sustainable over a longer period of time. The survey at the first site did not show any promising groundwater potential up to the investigated depth which was around 70 m. The study confirms the usage of ERT surveys for exploring sources of freshwater supplies in arid regions.