Major ion chemistry, catchment weathering and water quality of Renuka Lake, north-west Himalaya, India

The water samples collected from Renuka Lake during pre-monsoon, monsoon and post-monsoon seasons were analyzed to know water quality related to major ion chemistry and other essential parameters. The water is found to be slightly alkaline having pH value 7.22-8.66. Both Ca2+ and Mg2+ are observed as the dominant cations, whereas SO42- and HCO3- are dominant anions during all seasons. The Piper plot has shown Ca2+-HCO3- type of water during pre- to post-monsoon seasons. Alkaline earth metals (Ca2+ and Mg2+) are noticed to exceed over alkali metals (Na+ and K+), and weak acid (HCO3-) surpass over strong acid (SO42-) in all seasons. The carbonate weathering of surrounding rocks is found to be the dominant source of major ions for the lake during pre- to post-monsoon. The WQI values 176.45-184.91 from monsoon to pre-monsoon have revealed that the water of Renuka Lake is unsuitable for drinking. The higher value of WQI is mainly due to increased concentration of F-, which is produced fromthefluorapatite, cryolite and mica etc., and anthropogenic activities. Its concentration more than standard permissible limit may be veryharmful for human being and aquatic species. However, based on sodium per cent (11.88-15.62%), sodium adsorption ratio (0.48-0.61) and residual sodium carbonate (<2.5meq/L), the water quality is determined fit for irrigation. The lake has indicated seasonal variations of Ca2+, Mg2+, Na+, K+ and HCO3-, etc., which may be due to changing temperature, monsoon rain and human activities. Thus, stringent mitigation measures are required to reduce increased concentration of various physiochemical parameters and preservation of the Renuka Lake.