Factors controlling groundwater chemistry of Renigunta area, Chittoor District, Andhra Pradesh, South India: A multivariate statistical approach

Abstract

Groundwater is a major source of water supply for domestic, agricultural and industrial purposes, particularly in semi-arid regions. Managing this resource in terms of quality and quantity is a crucial issue in order to fulfil the increasing need for water. In this study, Groundwater from 31 sampling sites of Renigunta area were collected during the pre-monsoon season of 2018. The order of major ions in the groundwater was as follows: Na+ > Ca2+ > Mg2+ > K+ and HCO3– > SO42− > Cl−. The data reduction techniques, for instance, factor analysis grouped the sampling sites into three distinct groups which are attributed to the overall influence of major ions, silicate weathering, and sulphate reduction processes. The cluster analysis in Q-mode grouped the sampling sites into fresh, hard and very hard categories whereas the cluster analysis in R-mode gave three distinct groups which are attributed to the overall impact of rock-water interaction, silicate weathering and dissolution of sulphate and chloride. Geochemical modelling reveals that the saturation index (SI) values of all wells were undersaturated concerning chloride and sulphate. In addition, the Gibbs plot reveals that water-rock interaction was the key process that governs groundwater chemistry in the study area, whereas the CAI-I and CAI-II indicate that the ion exchange process in between (Na+ + K+) and (Ca2+ + Mg2+). Even though, most wells are within acceptable limits, few cross them and some are quite close to acceptable limits indicating that water quality may deteriorate in the near future. Proper water quality monitoring is needed for groundwater sustainability in the study area. Keywords: Groundwater, Hierarchical cluster analysis, Factor analysis, Gibbs ratio, MINITAB, MINTEQ, Indices of Base Exchange, Renigunta