Assessing variability of water quality in a groundwater-fed perennial lake of Kashmir Himalayas using linear geostatistics – A paper in Journal of Earth System Science

The study of the hydrochemistry of the Manasbal lake was done to find out whether the lake water was fit for drinking, irrigation and other purposes.

Eighteen water samples were analysed for major ions and trace elements to assess the variability of water quality of the lake for various purposes. Geostatistics, the theory of regionalized variables, was then used to enhance the dataset and estimate some missing spatial values. Results indicated that the concentration of major ions in the water samples in winter was higher than in summer.

The scatter diagrams suggested the dominance of alkaline earths over the alkali elements. Three types of water were identified in the lake, namely Ca–HCO3, Mg–HCO3 and hybrid types, which reflects the initial stage of evolution of the lake water. The lake water was found to be controlled by rock–water interaction with carbonate lithology as a dominant source of the solutes. The major (Ca2+, Mg2+, Na+, K+, NO3 and HCO− 3 , CO3 and Cl) and trace elements of the lake water were within the World Health Organization standards, indicating that the lake water is potable and suitable for other purposes.

Although NO3 concentration (ranging from 1.72 to 2 mg/l), is within the permissible limit and not very alarming, the gradually increasing trend is not acceptable. Significant temporal variation was found in the trace elements Fe2+,Mn2+, Ba2+ and Sr2+, which may be due to the hydrological conditions in the watershed as well as biological productivity in the lake.

This study is significant as hydrogeological information on such high altitude lakes in India is scanty. It is however, important to guard the lake’s spatio-temporal variability as the water is used for domestic as well as agricultural purposes. However, regular monitoring using an optimal monitoring network at a suitable frequency is recommended to detect any unacceptable variability of pollutants and adopt appropriate remedial measures.

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