Evaluation of potable groundwater zones identification based on WQI and GIS techniques in Adyar River basin, Chennai, Tamilnadu, India

Abstract

The main objective of this study is to identify the potable groundwater zones in Adyar River Basin (ARB) that forms the major river of Chennai metropolitan and significantly contributes to the demands of this big city's water supply. Twenty eight groundwater samples were collected during postmonsoon and premonsoon seasons in 2016 from the wells of ARB which is downstream of Chembarambakkam Lake, which supplies drinking water to Chennai metropolitan city. All the water samples were analyzed using Portable meter and Ion Chromatography for physico-chemical parameters and major ions such as pH, TDS, Ca, Mg, Na, K, Cl, HCO3, SO4 and NO3. The analytical results were compared with the WHO, USEPA & BIS guideline values and reported that some of the samples exceeds these guideline values for drinking water quality. Spatial distribution maps were prepared to identify the potable groundwater available regions based on these water quality parameters. Piper and Gibbs plots are generated to identify the nature and type of groundwater with processes controls the groundwater chemistry. Principal component analysis was done to interpret the possible sources of chemical compounds present in the groundwater. To precisely delineate the potable groundwater region in ARB, Water Quality Index (WQI) approach is employed with the basic water quality parameters and spatial distribution maps were prepared using GIS for the obtained indexes. It is found that only 10.71% and 17.86% of the study area groundwater is within the excellent water quality for drinking during postmonsoon and premonsoon respectively, whereas 42.86% in postmonsoon and 14.29% in premonsoon is found as poor quality groundwater for drinking. The groundwater of the northwestern and western part of ARB is under very poor and unsuitable category for drinking in both the seasons. This region of ARB is recommended for implementation of artificial groundwater recharging to improve the groundwater quality and make it suitable for drinking.