Powai Lake - Hydrology and Water Quality

Hydrology and Water Quality

It is reported that the average rainfall at Powai is about 2,540 centimetres (1,000 in), and the lake overflows for about for sixty days each year. The overflow from the lake flows into the Mithi River. Silt studies conducted in 1995 estimates that 4500 lakh cubic metres of silt has been deposited in the lake since its construction. It supplied two million gallons of water to Bombay (now Mumbai) when it was built. Following the construction of the Tansa dam and creation of the reservoir, in 1892, Powai waters were used for irrigation. The lake drains a catchment of 6.61 km2 (part of the Powai-Kanheri hill ranges which also drain into the adjoining Vihar Lake and Tulsi Lake). The dam, built in stone masonry has a height varying from 3 m to 6m with top level of the dam kept at E.L. 58.5 m (with Town hall datum). Government of Maharashtra reports that due to eutrophication of the lake water from untreated sewage and garbage from nearby residential and slum colonies, the lake water is unfit for drinking water use. Hence, the lake is now used for recreation, gardening, cattle washing and fishing. The water of the lake is also supplied to Aarey colony and Larsen & Toubro for non domestic uses. Dissolved Oxygen (DO) level at the bottom of the lake is reported to be 0.71 mg/litre and at surface 4.11 mg/litre, average value of pH is 7.2 and COD is 42.70 mg/litre on the surface and 119 mg/litre at the bottom of the lake.