Abstract:
Lakes are the primary sources of drinking water in hilly regions, where the scope of boring tubewells, canals and
lift irrigation is limited. Nainital Lake is the principal source of water supply for Nainital, a popular hill station
situated around 1937m above the mean sea level (MSL), in the foothills of the outer Himalayas. The Nainital
Lake is the major tourist attraction and forms the economic backbone of Nainital town, India. Thus, the water
quality of the lake, and the influent runoff characteristics are of critical importance. Eutrophication is the primary
water quality issue. To reduce the excessive external nutrient loading, identification of the major influent
drain and estimation of pollutant loads is a crucial step. We characterized various water quality parameters (pH,
turbidity, BOD5, COD, PO4-P, T-P, NO3-N, Pb, Cd, Zn and Cu) and pollutant loads over a period of one year,
which included a rainy season. The runoff drain contributing the major share of the pollutants to the lake was
identified. Nitrogen and phosphorous budgets over the one-year period revealed that wet weather flow is the
major contributor of nutrients to the lake. Phosphorous is the limiting nutrient, which controls eutrophication.
The Phosphorous load into the lake during the wet weather season was twelve times more than that during the
dry weather season.
