Hydrogeochemical Characterization of Groundwater Using Conventional Graphical, Geospatial and Multivariate Statistical Techniques

Groundwater from 25 bore wells of Nagari area were obtained and assessed for physico-chemical characteristics and the major ion concentrations in the pre-monsoon period of 2018. From the results it is found that groundwater has elevated levels of SO42−(64%), Cl−(24%), Ca2+ (28%) and Na+ (3%) which are unsuitable for drinking purposes. The spatial distribution diagrams show that the ions were highly concentrated in both NE and Eastern directions. Cluster analysis in Q-mode results four clusters which are fresh, nearly fresh to brackish, moderately brackish and brackish in nature, while the R-mode cluster analysis shows that weathering of silicates, chloride and sulphate minerals which are caused by agricultural fertilizers, sewage and industrial discharge are the main factors regulating groundwater chemistry in the study area. Factor analysis results three factors, in which Factor 1 is a hardness-controlled factor, factor 2 is an unaffected and low mineralised factor and factor 3 shows high mineralisation due to the impact of each and every ion in groundwater. In accordance with the WHO standards, 52% well samples are unfit for drinking purposes. Parameters such as the sodium percent (%Na), sodium adsorption ratio (SAR), Kelly’s ratio (KR), magnesium ratio (MR) and permeability Index (PI) show that 22 well samples (88%) are satisfactory for irrigation uses with exceptions such as KR (2 samples) and MR (1 sample). A total of 15 well samples (60%) are suitable for irrigation when USSL and Wilcox classifications are considered. Bivariate plots show that weathering of silicates is the major governing mechanism of groundwater hydrochemistry. The Indices of base exchange (IBE-I and IBE-II) reveal that the reverse ion exchange prevails in groundwater of investigated region.