Study of hydro-chemical characteristics of Lake Nainital in response of human interventions, and impact of twentieth century climate change

In the recent past, lake water is greatly deteriorated due to the global climate change and anthropogenic activities because they affect both quantity and quality of the available water. Lakes in mountainous regions are generally small, and therefore more sensitive to natural/human-induced perturbations. In this study, the effect of twentieth century global climate change and human interventions was analysed for Lake Nainital, located in a densely populated valley of Kumaun Himalaya. For this purpose, gridded (0.5⁰ × 0.5⁰ and 0.25⁰ × 0.25⁰) climatic (T _Mean, T _Max, T _Min, DTR and rainfall) data of period 1901–2000 available on monthly time steps were employed for detecting an annual and seasonal pattern of change in the climatic variables in the lake region. The samples of water collected between February 1994 and July 1996 for different months from the lake were used for determining the physical and chemical characteristics of the lake water. The samples were analysed for: field parameters (temperature, pH, EC), major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃ ⁻, SO₄ ²⁻ and Cl⁻), and nutrients (NO₃ ⁻ and PO₄ ⁻). Results derived from the chemical analysis of water reveal that anthropogenic activities, increased in recent past, have accelerated the deterioration and eutrophication processes of the lake. However, decrease in mean annual and monsoonal rainfall will affect the various components of water balance and may cause reduction in the lake volume in the future.