Jal Mahal - Man Sagar Lake

Man Sagar Lake

Status of water quality

In recent years, with urbanization of Jaipur city and areas surrounding the lake, ecological system of the lake and its vicinity area deteriorated drastically. It got silted up heavily thereby reducing the surface area of the lake. The silt deposited (estimated to be about 2,500,000 cubic metres) was contaminated with effluents (untreated sewage) from the city drainage causing intense eutrophication. The ground water around the lake was also found to be highly contaminated and created serious health hazards. The rainwater combined with sewage water flow from the city resulted in the lake water emnating foul smell. Water samples collected from the lake were tested, which clearly showed that water quality was not uniform. It was extremely poor in southeast, south and southwest caused due influent nalas. The water quality parameters of BOD and total nitrogen recorded were 20 mg/L each. BOD values indicated high level of organic matter. COD denoted a very high level of oxidisable chemicals. Nitrate and phosphate content were excessive. Coliform number was more than 500 times the normal. The Chloride content was found to be fatal to plants and fishes.

Hydrology

The fresh water into the lake is seasonal during rains between July and September. This flow originates from 325 small and big streams that drain the hilly catchment of the lake. But the two municipal nalas from the Jaipur city contribute the perennial flow to the lake. The volume of water in the lake has been assessed as 3,130,000 cubic metres at the maximum water level. During lean season, it is said to be about 360,000 cubic metres from October to June. The depth of water at the deepest location in the lake is recorded to be a maximum of 4.5 metres (15 ft) and a minimum of 1.5 metres (4.9 ft). In addition, the stored water was also used for irrigation on the downstream end of the lake during summer months resulting in drying up of the lake in these months.