Vertical electrical sounding (ves) for salinity assessment of water-bearing formations

Abstract

Electrical resistivity surveys (1-D) were carried out at selected sites in the region between the confluent rivers (Ravi and Jhelum) of Punjab, Pakistan, to audit tubewell placement and depth in order to minimize the amount of salt applied to the soil through irrigation. The Schlumberger electrode configuration was employed to collect the resistivity data and the resultant resistivity vs depth models for each site were estimated. From the interpretation of vertical electrical sounding (VES) data, the sites had one to three aquifer layers of different salinity levels and fitness for irrigation (FFI) classes ranging from good groundwater quality (FFI1) to highly saline up to 6.4 dS m−1 (FFI3). Twenty-one tubewells were investigated and it was found that not only were most wells theoretically suboptimally placed (57%) with respect to the best water quality available but also 33% were sunk at too deep a level, bypassing aquifer layers of better water quality [FFI1]. From the cost–benefit analysis, it was estimated that a total of 64 000 Pakistan rupees could have been saved on five wells through installation costs due to suboptimal depths. It is concluded that VES is an effective method for the evaluation of existing wells and aquifer systems. Copyright © 2017 John Wiley & Sons, Ltd.