Investigation of groundwater resources using electrical resistivity sounding and Dar Zarrouk parameters for Uthal Balochistan, Pakistan

Abstract

Uthal is a small town in the Balochistan province of Pakistan. It has an arid to semi-arid climate and groundwater is the primary source of freshwater for domestic and agricultural uses. To evaluate groundwater's nature, an electrical resistivity survey (ERS) was conducted in Uthal. Groundwater investigation for 25-point data was carried out with the PASI Electrical Resistivity Imaging System, using the Schlumberger array. The data was acquired with a maximum current electrode spacing of 300 m. The geoelectrical parameters measured were analyzed by IPI2win software by curve matching, and five geoelectrical layers were identified, and the Dar Zarrouk parameters were calculated. The top thinnest layer of unconsolidated material had a resistivity between 600 and 2600 Ωm. The second layer was of unconsolidated sand and gravel with a resistivity of 50–11,500 Ωm; the third with dry sand and clay had a resistivity of up to 200 Ωm; the fourth showed a thick freshwater zone with a resistivity between 75 and 100 Ωm followed by a thick layer of sand and clay with fresh water had resistivity between 48 Ωm and 90 Ωm. The Dar Zarrouk parameters, longitudinal unit conductance S is from 0.1 to 1.65 mho; transverse unit resistance T greater than 25,000 Ωm2; longitudinal resistance RS is from 50 to 1350 Ωm and transverse resistivity RT from 22 to 1150 Ωm. ERS data and Dar Zarrouk parameters showed that the study area has freshwater resources in the subsurface. Saline water is present in isolated locations in small pockets, resulting from dry surface conditions. The results of ERS data and Dar Zarrouk parameters show no occurrence of seawater intrusion.