Seasonal variation in the major ion chemistry of Pandoh Lake, Mandi District, Himachal Pradesh, India

Pandoh is a beautiful Lake surrounded by Shivalik sequences (Lesser Himalaya) in the Mandi District of Himachal Pradesh. A comprehensive and systematic study on the seasonal pattern of major ions (Cl-, PO43-, HCO3-, NO3-, SO42-, Na+, K+, Ca2+, Mg2+) and SiO2 was carried out to understand the geochemical processes controlling water quality. There is marked seasonal variation for almost all ions. Carbonate weathering and atmospheric precipitation are strong factors controlling the chemistry of major ion such as Ca2+, Mg2+ and HCO3- in the winter and summer seasons. In the monsoon season, relatively low concentrations of all the ions were observed due to dilution effects. Ca2+, Mg2+ and HCO3- generally account for about 70% of the total ions throughout the year. The ratios Ca2+ + Mg2+/Na+ + Cl-, HCO3- /(Ca2+ + Mg2+), (Ca2+ + Mg2+)/T-2(+), (Na+ + K+)/T-z(+) indicate that carbonate weathering is the main control on water chemistry in conz z trast to other Himalayan lakes. The low concentrations of Na+ and K+ indicate a minimal contribution from the weathering of silicate minerals to Pandoh Lake. Correlation matrix and principal component analysis were used to identify various factors influencing the ionic strength of Pandoh Lake waters. The overall water quality variation (in space and time) as well as comparison with the quality of other Himalayan lake water indicates that this lake is non polluted, however there are indications of possible enrichment of nutrients (eutrophication) in the near future in the Himalayan region of the Indian subcontinent. Hence Pandoh Lake deserves further detailed attention for management of the water resource to preserve its eco-hydrological status. (c) 2007 Elsevier Ltd. All rights reserved.