Use of GIS-AHP tools for potable groundwater potential zone investigations—a case study in Vairavanpatti rural area, Tamil Nadu, India

Abstract

Vairavanpatti is a rural area in the district of Sivagangai, Tamil Nadu, India, prone to water deficiency. Azimuthal square array for vertical electrical sounding (VES) techniques were used to delineate the geoelectrical layers at five different locations. Groundwater samples were collected in 15 locations and analyzed for pH, EC, TDS, TH, T-Alk, Ca, Cl, SO4, Fe, and SiO2 levels. The minimum and maximum apparent resistivity values recorded in location 5 with 37.6 Ωm and location 4 with 1150.7 Ωm. Most of the quality parameters exceeds the WHO (2008) and BIS (2012) guideline values except pH and SO4. Iso-resistivity maps for apparent resistivity values suggest at 10-m intervals a total depth of 80 m. The iso-resistivity maps and spatial distribution maps were reclassified with respect to their desired values based on WHO (2008) and BIS (2012) guidelines for drinking water. Analytical hierarchy processes (AHPs) were used to assign the weights for each reclassified layers. The relative importance of layers for potable groundwater and potential zone were identified, in which the consistency ratio is kept as below 0.1. The result shows that the 23% groundwater of northern part is not suitable for drinking purposes. In the overall study area, 51.33% of the southwest, southeast, and central parts possess potable groundwater with moderate potential. In northern part, 22.42% have non-potable and moderate potential while 13.38% of the northeastern part contains good potential of potable groundwater. All other categories are 12.21% of potable and poor potential, 0.5% of non-potable with good potential, and 0.16% of non-potable with poor potential of groundwater in the study area. Rainwater harvesting and artificial recharge must be implemented in these areas to improve the potential and quality of groundwater. It is understood that AHP-enabled GIS can be used effectively in the identification of potable and potential groundwater zone in any complex regions.