Groundwater Exploration Using Remote Sensing and GIS Techniques Coupled with Vertical Electrical Soundings from Hard Rock Terrain: A Case Study in Salem District, Southern India

In South India, Salem District can be geologically classified as a hard rock terrain. More than 90% of the district is underline by hard rock of Archaean. The tectonic activities like weathering, fracturing or faulting aid in development of secondary porosity. The weathering and fracturing in hard rocks are highly variable within a very short distance which challenges the location of potential sites. Under such a scenario, a baseline information on various groundwater controlling factors namely Geology, Geomorphology, Topography, Lineament, Drainage and Soil is imperative. Remote Sensing (RS) and Geographical Information System (GIS) techniques are the major tools in deciphering the surface and sub-surface conditions. The study gains importance since an integrated approach using RS and GIS for mapping the structural features have been field checked with collateral data including Vertical Electrical Sounding (VES) while targeting high yielding bore well locations. The entire study are was mapped on 1: 25,000 scale using IRS-P6, LISS-IV satellite data and Shuttle Radar Topography Mission (SRTM 90 m) elevation data. Under the GIS environment, drainage and lineament densities and slope were calculated. Suitable weights were assigned for each layer parameters. Based on the above data analysis, ground water potential maps were generated in the hard rock terrain of Salem District (Southern India). The potential map was divided into six prospective zones (i.e., excellent, very good, good, moderate to poor, Poor and very poor). The above systematic analysis helped to locate 21 VES points wherein the shallow aquifers and deeper fracture zones could be delineated. In majority of these locations, High yielding (755–49 liters/minute) bore wells were drilled with good correlation of litho logs which greatly helped in providing the much needed rural water supply schemes in this water-scarce area of Salem District.