Temporal and spatial variation of the stable isotopes in the waters of Sutlej and Beas rivers

Abstract

In the present study, the spatial and temporal variation of the values of stable isotopes (δ 18 O and δ 2 H) of river water and spatial variation of values of groundwater and rainfall have been evaluated. The water samples from seven stations of Sutlej river and Beas river each, fourteen stations of groundwater (deep and shallow), and twelve stations of rainfall were collected at different times from 2008 to 2015. The water samples were analysed for stable isotopes (δ 18 O and δ 2 H) and the values were expressed with units per mil (or per thousand). The box and whisker plots of values of δ 18 O, δ 2 H, and d-excess for each station of both the rivers Sutlej and Beas were plotted. The isotopic water lines have been used to identify the evaporation and precipitation sources. Kendall’s correlation coefficient has been used to know the similarity in the isotopic composition of different sources. Linear regression was performed between the δ-values of 18 O, 2 H, d-excess, geographic factors, and climatic factors. The results showed the water of Beas river has enriched values of stable isotopes than the Sutlej river. At each station of both rivers, the isotopic composition varied significantly with time. The regression results did not show any correlation between the δ-values and climate factors indicating the sources of water during different seasons of the year. The regression between δ-values and geographical factors was also weak. Improvement in the value of R 2 has taken place when multiple linear regression was done considering latitude, longitude, and elevation as independent variables. Still, the value of R 2 is not equal to 1. Multiple linear regression had also been performed considering the rainfall, temperature, and relative humidity together. The isotope characterization of water from different sources is useful for understanding various hydrological processes and the scientific management of the water resources in the study area.