The report provides an account of the findings of water quality studies of Lake Nainital and surroundings. Even though quite a few water quality investigations have been conducted by other researchers, they were more focused on biological aspects and overlooked the hydrological aspects. Further, not all of the earlier studies on Nainital incorporated the groundwater quality aspects, which are essential to establish the background values that can be ascribed to the geology of the region. Only after establishing these, the pollution levels can be assessed.

During the investigations, the major ions namely calcium, magnesium, sodium, potassium, bicarbonate, sulfate and chloride were analyzed. Apart from this the in-situ physico-chemical parameters such as temperature, pH and electrical conductivity were determined. The dissolved oxygen content of the lake water were monitored regularly at different depths and at different locations of the lake to assess the pollution levels during different seasons. The trace elements such as iron, manganese, lead, boron, zinc and copper were also analyzed.

The results indicate that the lake water is hard in nature, and the hardness exceeds the desirable limit prescribed in the IS:10500 standards of BIS.  All the springs and groundwater drawn through wells located within the lake basin are hard owing to the local geology, which is characterized by calcareous rocks, such as slate, limestone and dolomite. The lead content in the lake as well as surrounding springs also exceed the IS: 10500 standards. The source of the lead could also be ascribed to the local geology.

The report also discusses the possible sources of different ions in aquatic environment, the temporal variations in concentrations of different ions in the lake water, surrounding springs as well as nallahs. The eutrophication level in the lake has reached an advanced stage and it is classified as hypereutrophic. The limiting factor in the eutrophication of the lake is phosphorus. The external load of soluble reactive phosphorus can be reduced substantially if the inflows through the nallahs are diverted during non-monsoon season.

This report presents complete details of the investigations carried out, the sampling strategy adopted and the analytical procedures followed including the accuracy of measurements and analysis. Possible methods that can be adopted for amelioration of the lake water quality have also been suggested.

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