Environmental isotopes investigation in groundwater of Challaghatta valley, Bangalore: A case study

Radiogenic isotopes (3H and 14C) and stable isotope (18O) together with TDS, EC and salinity of water were used to discriminate qualitative and quantitative groundwater age, probable recharge time, flow respectively in groundwater of Challaghatta valley, Bangalore. The variations between TDS and EC values of sewage, corporation water, bore and open wells with concomitant variations in salinity confirmed an immerse relationship with the depth of wells, Also, the source of recharge and contamination of groundwater as sewage. However, lighter ä18O bearing water more commonly occurred at higher elevations and heavier at lower elevations in the entire valley presenting a clear enrichment in ä18O probably due to evaporation and confirming major source of surface water as South - West monsoon. The groundwater samples in valley contained higher 3H except five samples (OW21, OW24, BW5, BW20 and BW24), suggesting recent recharge and categorized as modern age water. Further, from the results of 14C it is inferred that some groundwater samples in Challaghatta valley belongs to old water regime with pmC values ranging between 58 and 112