Earth and Planetary Science

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

Muhammad Jahangir Khan

Department of Earth & Environmental Sciences, Bahria University Karachi Campus, Pakistan

Syeda Rida Fatima Bokhari

The State Key Laboratory of Information Engineering in Surveying, Wuhan University, China

Umair Bin Nisar

Centre for Climate Research and Development, COMSATS University, Islamabad Campus, Islamabad, Pakistan

Farhad Ali

Department of Earth & Environmental Sciences, Bahria University Karachi Campus, Pakistan

DOI: https://doi.org/10.36956/eps.v1i1.520

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Abstract

Availability of subsurface fresh water in coastal cities of the world is a growing problem due to sea level intrusion and less seepage. The authors have utilized an integrated data dataset in which conventional geophysical methods were used to collect primary data for the groundwater resources in Karachi and geospatial approaches were used to generate the hydrogeological model. It aimed to investigate geological/hydrogeological conditions of any aquifer system in the study area. The geophysical survey was planned 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 were processed in an iterative process to improve the signal to noise ratio and obtain smooth field data curves for delineation of the aquifer. The authors 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 of these parameters. The results identified an aquifer system in the depth ranging from 53.3 meters to 143.9 meters. The aquifer in the area is 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.

Keywords: Aquifer, Vertical electrical sounding, Weighted overlay analysis, GIS

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