Mansagar Lake - Ministry of Environment and Forests

Sengupta, M. and Dalwani, R. (Editors). 2008. Proceedings of Taal2007: The 12th World Lake Conference: 1530-1541

Mansagar Lake: Past, Present & Future K. P. Sharma1, Subhasini Sharma2, Shweta Sharma2, P. K. Sharma1, R. C. Swami1, P.K. Singh1and G. S. Rathore2 1 Department of Botany, University of Rajasthan, Jaipur -302004 2 Department of Zoology, University of Rajasthan, Jaipur -302004 Email: [email protected]

ABSTRACT Mansagar is spread over in about 130 ha with a maximum depth (>7m) at the dam’s outflow point is a man-made lake polluted with municipal and industrial sewage since 1962 through 2 main wastewater drains namely Brahampuri and Nagtalai. Water-hyacinth infestation in 1975 suppressed algal growth whereas addition of its organic produce catalyzed water quality deterioration. This lake suffered maximum when unprecedented down pour for 2days in August 1981 deposited enormous amount of sand and silt through wastewater drains. After 45 years of neglect, Ministry of Environment and Forest, New Delhi and State Government of Rajasthan have ventured into its restoration which is being executed by Jaipur Development Authority (JDA). This includes revamping of existing 27MLD Sewage Treatment Plant near Bhrampuri from which 7MLD treated water will be diverted to lake for compensating evaporation losses, lake front promenade along Amber road, road construction along south – east bank, desilting of lake, islands for bird nesting, check dam (about 5ha) for storing rainy season hill run off to forest wild life and manual removal of water-hyacinth. JDA has funded to State Forest Department for conserving soil and water on the forested hills surrounding lake from three sides. During Limnological studies of the lake (JDA sponsored), we found very low Secchi disk transparency (7m) at the dam’s outflow point. It has a catchment of 23.5km2, about 40% of which falls inside the dense urban area is presently the major source of water (about 90%) in the lake in the form of storm water runoff during rainy season while sewage in the dry weather. The remaining 60% watershed in the form of denuded and forested hills virtually contributes very little on account of impediments such as human settlements and hotels in the foot hills on western side and construction of roads on three sides of the lake (Fig.1b). The maximum level of the lake is at 99.0m contour at which volume of water is 3136569.75MCM. The lake glory as a pristine water body lasted until the former rulers had their control over the city and its surroundings having thick forest cover and a very thin human settlement of cowmen. The unpleasant history of the lake began shortly after independence, when new administration of Jaipur diverted walled city sewage in 1962 through 2main wastewater drains namely Brahampuri and Nagtalai. The most notorious aquatic weed water-hyacinth (Eichhornia crassipes) entered in the lake in 1975. It suppressed algal growth markedly disturbing lake trophic structure and also accelerated siltation by adding dead organic matter that catalyzed water quality deterioration leading to mass fish mortality (Sharma et al. 1978, Goel 1980, Trivedy 1980). This lake suffered maximum when unprecedented down pour for 2 days in August 1981 deposited enormous amount of sand and silt through two drains. After 40 years of neglect, under the banner of National Lake Conservation Programme of Ministry

of Environment and Forest, New Delhi, the State Government of Rajasthan received funding for lake restoration which is being executed by the Jaipur Development Authority (JDA). The total cost of this project is Rs. 24.72crores; of which 70% is the Government of India contribution while the rest is borne by the State Government.

Figure 1a. Satellite photograph of Mansagar lake.

Figure 1b. Mansagar lake during summer (2007).

LAKE WATER QUALITY MONITORING Physico-chemical Characteristics Water quality of lake had been maintained at 10 sampling sites for more than two years (March 2005May 2007). The sampling at each site was made both from the surface and at 1m depth (sub-surface), with the exception of site 1 receiving municipal and industrial sewage in to the lake. Two surface water samples were collected from this site, one from wastewater outfall (S1a) and the other was from 100m of outfall (S1b). The remaining 9sites (S2-S10) from which both surface and sub-surface samples were collected are far away from each other. Temperature, dissolved oxygen and free carbon di oxide content of the water samples were estimated at the lake while other parameters in the laboratory following standard methods (APHA1989). Since water quality data of surface samples are almost similar to sub-surface samples and therefore,

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these are pooled and seasonal variations in values of various parameters are presented in Table 1. Table 1. Physico-chemical characteristics of Mansagar lake water in different seasons during March 2005- June 2007. Parameters/ Sites Temp. O L EC O L pH O L TH O L Chloride O L Sulphate O L Sulphide O L TKN O L TP O L BOD O L COD O L DO O L FreeCO2 O L

Summer (April- June) 2005-06 2006 -07 NA 21.0-24.0 NA 20.0-26.0 3.6-6.5 2.6-5.1 2.1-3.06 2.1-5.1 7.6-8.4 7.2-8.3 7.2-8.1 7.9-8.9 860-1620 694-1050 576-748 568-720 568-917 536-1040 219-880 424-630 NA 154-374 NA 166-212 NA Nil -17.3 NA Nil – 0.3 55-145 53-150 48-120 31-80 5.9-6.9 3.96-9.04 5.2-7.8 4.6-10.04 202-350 154-589 135-330 120 - 287 425-988 319-1830 268-498 224-355 1.0-4.9 Nil 1.3-17.5 Nil -11.7 132-350 Nil Nil - 647 Nil - 97

Rainy (July – October) 2005-06 2006 -07 NA 22.0-30.0 NA 23.0-29.0 1.4-2.39 1.3-4.5 1.24 -3.7 0.9-3.23 7.1-7.8 7.6-8.3 5.2-8.2 7.8-8.5 300-568 414-876 400-992 456-604 136-358 310-838 267-615 366-462 95-1578 98-448 82-1160 100-558 NA Nil -6.4 NA Nil -1.28 51-66 31-73 11-39 13-50 0.45-3.75 3.08-5.04 0.6-9.95 2.82-6.31 16-540 155-333 10-185 74-189 30-1051 204-416 13-365 151-298 Nil -3.6 Nil -7.3 1.5-12.1 1.61-16.2 22-145 5-95 Nil - 335 Nil - 44

Winter (Nov. – March) 2005-06 2006 -07 14.0-20.0 12.0-19.0 14.0-22.0 8.0-21.0 1.85 -2.7 2.6-3.3 1.71-2.71 1.9-2.84 7.6-8.4 7.4-7.9 6.9-8.8 8.1-8.9 576-716 432-728 464-664 480-736 318-412 216-556 310-412 444-850 130-1432 68-224 144-1556 98-228 NA 1.74-8.1 NA Nil -9.3 60-121 35-82 21-106 13-60 4.8-6.21 3.93-5.97 2.2 – 8.7 1.97-8.56 132-205 218 - 364 26-361 31-240 271-643 239-376 54-610 102-480 Nil -1.35 Nil -2.6 0.5-21.4 3.0-16.7 8-66 40-244 Nil - 41 Nil - 73

O = Outfall (Site 1-2); L = Lake samples (Site 3-10); NA = Not available; Except for pH and EC (mS), all values are in ppm.

In general, values of all the parameters were significantly higher at the Outfall sites (S1a, b) in comparison to other sites (S2-S10). Secchi disc transparency was found very low (