Quantification of groundwater–surface water interactions using environmental isotopes: A case study of Bringi Watershed, Kashmir Himalayas, India

Abstract

Environmental isotopes including $${\updelta }^{18}$$ O, $${\updelta }^{2}$$ H and $$^{3}$$ H of precipitation, streams and springs were determined in the mountainous Bringi catchment of Kashmir Himalaya, dominated by carbonate lithology. The isotopic signature of winter precipitation is reflected in stream and spring water in late spring and is, therefore, representative of snow melting. The spring waters in September bear the enriched isotopic signatures of summer rainfall. The strong correlation ( $$r^{2} = 0.97$$ ) between the isotopic composition of streams and springs indicates the streams and springs either share similar catchments or the springs are recharged by the streams. Chloride mass balance and isotopic mass balance studies suggest that the surface recharge component averages 337.35 m $$^{3}$$ /s, which is about 75% of total stream discharge during the high flow period. Similarly, the contribution of surface water to groundwater recharge during the low flow period averages 7.5 m $$^{3}$$ /s, which is about 18.6% of total stream flow. Furthermore, the mean residence time of the springs calculated from the tritium decay equation is very short (<1 year). The residence time is longer for Kongamnag and short for Achabalnag, which is further supported by dye testing.