Groundwater samples from alluvial aquifers of Bathinda district, southwest Punjab were measured for physicochemical parameters as well as major ion chemistry to evaluate the groundwater suitability for drinking and irrigation purposes and to present the current hydrochemical status of groundwater of this district. Temporal variations were analyzed by comparing the pre- and post-monsoon groundwater chemistry. Most of the samples showed contamination: F⁻ (72 %), Mg²⁺ (22 %), SO₄ ²⁻ (28 %), TH (25 %), NO₃ ⁻ (22 %), HCO₃ ⁻ (22 %) and TDS (11 %) during pre-monsoon and F⁻ (50 %), Mg²⁺ (39 %), SO₄ ²⁻ (22 %), TH (28 %), NO₃ ⁻ (22 %) and TDS (28 %) during post-monsoon above permissible limits for drinking, while rest of the parameters fall within the limits. Irrigation suitability was checked using sodium absorption ratio (SAR), residual sodium carbonate (RSC), percent sodium (Na%) and permeability index (PI). Most of the samples fall under good to suitable category during pre-monsoon period, but fall under doubtful to unsuitable category during post-monsoon period. Presence of high salt content in groundwater during post-monsoon season reflects leaching of salts present in the unsaturated zone by infiltrating precipitation. Hydrochemical data was interpreted using Piper’s trilinear plot and Chadha’s plot to understand the various geochemical processes affecting the groundwater quality. The results indicate that the order of cation dominance is Na⁺ > Mg²⁺ > Ca²⁺, while anion dominance is in the order Cl⁻ > HCO₃ ⁻ > SO₄ ²⁻. The geochemistry of groundwater of this district is mainly controlled by the carbonate and silicate mineral dissolution and ion exchange during pre-monsoon and leaching from the salts deposited in vadose zone during post-monsoon. The main sources of contamination are soluble fertilizers and livestock wastes. This study is significant as the surface water resources are limited and the quality and quantity of groundwater are deteriorating with time due to anthropogenic inputs.

Quality assessment of groundwater for drinking and irrigation was evaluated in parts of Nalgonda district of Telangana state, India. The overall groundwater quality and the suitability to drinking and irrigation were evaluated by hydrochemical analysis of 78 groundwater samples. The water quality parameters were compared with that of the limits set by World Health Organisation (WHO) and Bureau of Indian Standards (BIS). Groundwater is found to be contaminated by fluoride and nitrate ions. The water quality indices (WQI) suggest that during pre-monsoon, 72.5% samples are suitable for drinking while 86.8% are suitable during post-monsoon. Indicators like sodium absorption ratio (SAR), electrical conductivity (EC), percent of sodium (Na %), residual sodium carbonate (RSC), permeability index (PI), magnesium ratio (MR), residual sodium bicarbonate (RSBC), salinity hazard (SH), potential salinity (PS), soluble sodium percentage (SSP), and magnesium ratio (MR) were estimated for assessing the irrigation suitability of the groundwater samples. Wilcox, United States Salinity Laboratory diagrams (USSL diagram) and Doneen’s chart infer that most of the samples are suitable for irrigation purpose and the suitability improves during post-monsoon. The geochemical evolution of the groundwater was also studied using Piper’s and Chadha’s diagrams. The major facies found in groundwater are Na–Mg–HCO₃–Cl, Na–Mg–HCO₃, Na–HCO₃, Mg–Ca–HCO₃, Mg–Na–HCO₃ and Na–Cl. Rock-water interaction, ion exchange and evaporite dissolution were found to be the major geochemical processes governing the groundwater chemistry.

Multivariate statistical analysis and inverse geochemical modelling techniques were employed to deduce the mechanism of groundwater evolution in the hard-rock terrain of Telangana, South India. Q-mode hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to extract the hydrogeochemical characteristics and classify the groundwater samples into three principal groups. Use of thermodynamic stability diagrams and inverse geochemical modelling in PHREEQC identified the chemical reactions controlling hydrogeochemistry of each of the groups obtained from statistical analysis. The model output showed that a few phases are governing the water chemistry in this area and the geochemical reactions responsible for evolution of groundwater chemistry along the flow path are (i) dissolution of evaporite minerals (dolomite, halite); (ii) dissolution of primary silicate minerals (albite, anorthite, K-feldspar, biotite); (iii) precipitation of secondary silicate minerals (kaolinite, quartz, gibbsite, Ca-montmorillonite) along with anhydrite and calcite; and (iv) reverse ion exchange processes.