Hydrogeochemical signatures of spring water in geologically diverse terrains: a case study of Southern Western Ghats, India.

Out of 5 million Indian spring water systems, a few were characterised for hydrochemistry and freshwater potential. The present study focuses on analysing the hydrochemistry, discharge, and drinking/irrigation water quality of both cold and thermal spring clusters namely Southern Kerala Springs (SKS) and Dakshina Kannada Springs (DKS) of Southern Western Ghats, India. Currently, eleven springs from SKS and ten from DKS including one thermal spring (TS) with temperature ranges from 34 to 37 °C were considered. The study revealed that cold springs (CS) of SKS are Na-Cl type, while the thermal and cold-water springs in DKS are Na-HCO3 and mixing water type, respectively. Two distinct mechanisms predominantly define the hydro-chemical composition of the springs-SKS are influenced by precipitation, whereas DKS is likely by chemical weathering processes. While comparing the major ions and saturation indices of thermal springs (TS), it is evident that silicate minerals predominantly affect the chemical composition of water. CaCO3- is oversaturated in TS water and tends to precipitate as a scale layer. PCA showed that both geogenic and anthropogenic factors influence water chemistry. WQI categorized the CS in both the clusters are in the "Excellent" rank as compared to TS. Irrigation water quality signifies that the cold springs are only suitable for irrigation. Moreover, it is evident from the discharge that both SKS and DKS were rainfed in nature. Discharge monitoring designated that the CS could augment drinking water supplies in the nearby regions indicating the necessity of conservation and sustainable use considering future freshwater scarcity.

Isotopic tracing of leachate percolation from municipal solid waste dump sites to groundwater in diverse climatic zones of India.

Groundwater resources in tropical regions are largely dependent on recharge by rainwater infiltration through soil layers with variable time. However, the rainwater infiltration through soil is a serious concern in urban tropics where it interacts with landfills at the dumpsites, potentially contaminating adjoining groundwater. In this study, the stable isotopic compositions of oxygen and hydrogen (δ18O and δ2H, respectively) in groundwater and leachates, adjoining municipal dumpsites in urban tropics (Bangalore, Kolkata and Durgapur located in diverse rainfall zonation of India), were analyzed to investigate their recharge sources and trace the possible mixing of leachate contaminants under three diverse climatology. The measured values of δ18O and δ2H suggested that the groundwater in these sites reflects higher recharge by rainwater. However, the d-excess values indicated secondary effects suggesting the groundwater has experienced significant modifications. The end member analysis using δ18O-d-excess relation pinpointed an additional leachate contribution from adjoining dumpsites. The critical fraction of leachate infiltration to groundwater quantified using two component mixing model ranged between (i) 1 and 33% in Bangalore, (ii) 5 and 13% in Kolkata and (iii) 18 and 76% in Durgapur, with its variability dependent on seasonality and aquifer connectivity. This information is crucial for groundwater management to secure water quality and to quantify potential hydrological contaminants particularly in drier seasons and drier regions, when and where the demand for groundwater is high, respectively.