Integrated Geophysical and Geospatial Approaches for Delineating Groundwater Potential Zones in Karachi, Pakistan

Abstract

Availability of subsurface fresh water in coastal cities of the world is a growing problem due to sea level intrusion and less seepage. We have utilized an integrated data analysis in which conventional geophysical methods was used to collect primary data for the groundwater resources in Karachi and geospatial approaches were used to model the hydrogeological parameters. It was aimed to investigate geological/hydrogeological conditions of any aquifer system in the study area. The geophysical survey was conducted to acquire electrical resistivity data in the outskirts of Karachi. The geophysical survey was carried out at twenty-one stations by adopting vertical electrical sounding technique with schlumberger configuration. The field data was processed in an iterative process to improve the signal to noise ratio and obtain smooth field data curves for delineation of the aquifer. We have interpreted field data to model the geological information and determine the hydrogeophysical parameters of respective layers. These parameters including the number of layers, aquifer resistivity, aquifer lithology, aquifer thickness and depth to the aquifer, are determined at each field station. The acquired dataset of hydrogeophysical parameters was used to build a geospatial database. The multi-criteria analysis and decision-making process were utilized in GIS based program to model spatial distribution models of hydrogeophysical parameters. The results identified aquifer system in the depth ranging from 53.3 meter to 143.9 meter. The aquifer in the area are mostly sandstone having sufficient thickness which varies from northeast to south and southwest due to undulating topography of the area. The maximum potential of the groundwater is identified in the south which is suitable for water exploration because of low resistivity zone, high aquifer thickness, and flow of drainage network.