CS(AR)-3/2007-08 : Water quality management plan for Rejuvenation of Sagar lake

Abstract

The Sagar lake situated in the Sagar town of Madhya Pradesh state is famous for its historical importance. It is considered to be the lifeline of the Sagar town, in terms of providing drinking water supply and in maintaining the town risk free from environmental hazards. The health of the lake since last two-three decades has severely been deteriorated and is under threat of further deterioration because of uncontrolled and unabated human interventions on it and its catchment. The quality of lake water is primarily being deteriorated because of flora and fauna fanning, accelerated developmental activities in the lake catchment. disposal of city wastewater as well as sewage through a number of septic tanks in the surroundings, and considerable silt inflow through the Kanera canal which feeds to the lake during the monsoon season.

The lake has a periphery of 5230 m with a maximum length of 1247 m and width of 1207 m. Mean depth of the lake is 2.69 in with a maximum depth of 5.3 m at full- capacity level. The lake is divided into two parts. the main lake with water spread area of 107.7 ha at full-capacity level and the other part of the lake with water spread area of 37.03 ha. The volume of the lake is 389 ha-m at full-capacity level. The catchment area of the lake is 1817 ha. out of which the water spread area is 145 ha.

In order to assess the physico-chemical constituents of the lake water, twelve parameters. viz. temperature. transparency, pH, dissolved oxygen (DO), alkalinity, hardness, nitrate, chloride, phosphate, iron, total dissolved solids and fecal coliform have been analyzed from the samples collected bimonthly during the period 2006 to 2008 from twenty-one locations, at three different depths in each location, of the lake. The lake water has been found yellowish green and has high algal activity. The transparency and dissolved oxygen of the lake water have been found extremely low. DO. BOD, iron contents have been found beyond the permissible limits in respect to the Class A categorization of IS:10500 standards and hence the lake water has been found unfit to use for drinking water purpose. A comparison of the present status of lake water with the status of the water quality of the lake in the year 1990 showed that the pollution level of the Sagar lake has increased considerably over the past eighteen years. The high concentrations of nitrogen and phosphorous has put the lake into the hyper-eutrophic state. The analysis of seasonal variation indicated that the concentration of chloride, nitrate and iron have increased during summer and decreased during monsoon season due to dilution of lake water. The analysis of annual variation of water quality constituents indicated that transparency and dissolved oxygen followed the decreasing trend while alkalinity, nitrate, phosphate and iron contents followed increasing trend. An overall water quality index has been developed based on the water quality standards set by various agencies to categorize the water quality status of the lake_ It has been found that the lake water is of poor quality suggesting unfit for drinking water purpose. The lake water quality has been found to reach the alarming stage and thus needs urgent attention for its restoration. For rejuvenation of the Sagar lake, a water quality management plan has been suggested.