Hydrogeophysical Investigation by Resistivity, Pumping Test and Evaluation of Hydraulic Properties using Ves Data, East of Sargodha, Punjab, Pakistan

Abstract

Geophysical study for groundwater in east of Sargodha using vertical electrical sounding (VES) has been conducted. The aims are to assess the groundwater potential, aquifer forms, depth to aquiferous zones, aquifer parameters and geoelectric layers. A field survey data of 2009 was provided by Pakistan Council of Research in Water Resources (PCRWR) Islamabad. Thirty seven vertical electrical soundings were performed using Schlumberger arrangement with half current electrode dispersing (AB/2) extending from 2 to 300 m and half potential terminal (MN/2) from 0.5 to 20 m with a SAS 4000 Terrameter. The obtained geoelectrical data were interpreted with partial curve matching, resistivity and equivalent thickness of different sub-surface strata and computer iteration using interpex IX1D software and the outcomes were confirmed by bore hole data. The results showed maximum of four geoelectric layers comprising clay, silty clay, clayey silt, silty sand and gravel sand lithology and with some confidence the dry/saturated and fresh, brackish and saline water interfaces. Result shows close correlation between VES and borehole records provided valuable information on subsurface hydrogeologic condition. The results of VES also indicate unconfined aquifer in the study area with significant clay horizon at some regions but if these are near the surface, it may consider confined aquifers. The geoelectrical resistivity value ranges from 2.1 ohm-m to 1589 ohm-m while the average depth of water table found 5.4 m. The average values of aquifer parameter in the study area obtained from different wells namely CWT-23, CWT-24, CWT-25, CWT-26 and CWT-42 were 6766.08 m/day for transmissivity, 24.312 m2/day for hydraulic conductivity, 0.0023 for specific yield and 0.0029 for storativity. The outcomes demonstrate that VES survey can recognize the layer containing water and nature of groundwater depth and thickness for its advancement. Dar zarrouk parameters have been deduced from quantitative interpretation of 37 schlumberger vertical electrical sounding (VES) point within study area. Goals of the research were to characterize the aquifer in the area and evaluate its potential vulnerability to contaminant seepage in terms of protective capacity of the overburden rock materials using Dar-Zarrouk (D-Z) parameters. The water samples were collected from 21 sites covering all conceivable drinking water sources i.e. tube well, water supply, bore and hand pumps and 16 parameters for groundwater characteristics like pH, Turbidity, HCO3, CO3, Ca, Mg, Hardness, Cl, Na, K, SO4, NO3, PO4, TDS, Fe and EC were statistically analyzed comparing with world health organization standards and correlated. The study area consists of strong, moderate, weak and inverse correlations among different parameters. The results vii of hard water shows that only 4.76 percent samples are coming in soft water range, whereas 4.76 percent is moderately hard, 19.05 percent is hard and 71.43 percent is related to very hard water zone. There is no excellent quality of water in the study area on the bases of electrical conductivity, whereas 23.81 percent is good quality water, 14.28 percent is in permissible water quality range, 33.33 percent is related to doubtful and 28.57 percent is unsuitable water in study water. The spatial distribution map shows that parameters vary spatially with respect to time. The piper plot shows the water type in 2003 and 2004-05 is Na-HCO3 and 2015 it is Na-Cl type water.