In the present study, a total of sixty groundwater samples, twenty each for the pre-monsoon, monsoon and post monsoon seasons of 2018, were collected from selected locations in the Mewat district of Haryana, India. Electrical conductivity (EC) was measured at the site and total dissolved solids (TDS) were estimated. Samples were analysed for anions (chloride, sulphate, and bicarbonate) and cations (calcium, potassium, magnesium, and sodium). Multiple regression analysis was performed to analyse the data and report the dominant ions. Piper trilinear diagram and Gibbs plots were used to find out the water type and the factors controlling the chemistry of the groundwater, respectively. The saturation index of CaCO₃, CaSO₄ and NaCl was determined, using the PHREEQC MODEL. Sodium and calcium among cations, and chloride among the anions, had the highest degree of affinity and strong significance for all three seasons. The calcium–chloride water type dominated for all three seasons and Gibbs plot depicted that most of the Na⁺/Na⁺ + Ca²⁺ and Cl⁻/Cl⁻ + HCO₃⁻ ratios show the weathering of rocks to form minerals as the major reason behind the ionic chemistry of the groundwater. The highest level of dissolution is encountered in the case of NaCl, followed by CaSO₄, whereas CaCO₃ depicts precipitation. The geochemical aspects of weathering, evaporation and ion exchange are the major processes responsible for high salinity, and anthropogenic activities are leading to its expansion. The findings from this study will be useful in management and remediation of groundwater salinity of the region.

The Upper Godavari (UG) catchment, India, faces critical water quantity and quality challenges driven by high evaporation rates and spatially variable rainfall, which significantly affects the catchment's hydrodynamics and threatens agriculture-based livelihoods. Understanding groundwater recharge processes and the impact of contaminants is essential for effective groundwater management. This study employs stable isotopes and tritium, alongside major ion geochemistry, to investigate hydrological processes in the riverine belt of the Western Ghats, characterized by Deccan basaltic terrain. Groundwater, surface water, and precipitation samples were collected in pre- and post-monsoon seasons (2022-2023). Post-monsoon stable isotope signatures indicate recharge predominantly from Indian monsoonal precipitation, while pre-monsoon stable isotopes reflect evaporation. The stable isotope signatures of the shallow aquifers imply rapid recharge and higher vulnerability to evaporation and contamination from agricultural runoff. In contrast, the stable isotope signatures of the deeper aquifers suggest older, more distant recharge sources with minimal recent contribution. Surface water closely resembles isotopically lighter monsoonal precipitation, and this plays a key role in recharging shallow aquifers. Tritium (³H) concentrations in groundwater (0.64 to 7.6 TU) locally exceed the annual average tritium concentration in modern rainfall (~7 TU), and locally higher values are observed post-monsoon and lower values pre-monsoon. This implies that most of the water in the subsurface is derived from recent rainfall with low transit times. Lumped parameter models (LPM) were used to estimate the mean transit times (MTTs) of groundwater, which ranged from