ENVIRONMENTAL DEGRADATION OF AN URBAN LACUSTRINE WATER BODY IN PUNE , INDIA

A.Waran, M.Mhasavade, S.Yewalkar, D.Kulkarni, P.Kulkarni, T.Vaishampayan, P.Deshpande, S.Manchi, K.Sahasrabuddhe and A.Patwardhan*

Department of Environmental Sciences, University of Pune, Pune - 411007.

* Research And Action in Natural Wealth Administration (RANWA), C - 26/1, Ketan Heights, Kothrud, Pune - 411029, Maharashtra, India.
 e-Mail : ranwa@pn3.vsnl.net.in
Corresponding author - ankurpatwardhan@hotmail.com

Key words - Lacustrine water body, environmental profile, human impact 

Pashan Lake is situated between 18°32'7"N and 73°46'58"E near Pune in Western India. The present paper assesses the impact of urbanization on the water quality with a focus on ongoing changes in biotic communities as well(Patrick,1972). Six sampling points were selected of which 2 are point sources and 4 non point sources of pollution to evaluate the spatio-temporal trends in water quality. Surface water samples are collected from these established sites once a month and analyzed for different physico-chemical parameters like pH, Temperature, Dissolved Oxygen, Free CO2, Chlorides, Phosphates, Total Alkalinity, Total Hardness ( APHA,1992) .Composite water samples were subjected to microbial analysis which includes determination of Most Probable Number, Total Viable Count and Plankton Analysis (Lackey,1938).For the quantitative estimation of aquatic fungi the Sector Analysis method described by Willoughby (1962) was employed. Besides exploring the relationship between birds and surrounding vegetation qualitatively, the paper also focuses on the impacts of degrading water quality on fishes and aquatic molluscs. Folk perceptions on the changing ecology of the lake were taken by interviewing fishermen and locals. Pashan Lake is a manmade lake, built by bunding Ram River. The catchment area is 40 sq.km . Since long it has been attracting migratory birds. Gole (1972) recorded the temporal variation in these winter visitors with notes on their ecological niche. Ghate and Vartak (1981)listed angiosperm flora at Pashan lake. Kanhere and Gunale (1999) recorded the trends in water quality with emphasis on phytoplankton studies. The surrounding area has witnessed a tremendous change because of the ever expanding city limits which has reflected in decrease in scrub vegetation surrounding the lake. 

Table 1 highlights the important factors that have changed drastically during the last two decades owing to stress of urbanization.

Table 1 Temporal changes in various environmental attributes

Deforestation on nearby hills has caused heavy siltation resulting in decrease in the depth of the lake. This has reflected in reduction in the number of Pochards (deep diving duck) which prefer to occupy the central deep portion of the lake. They are now outcompeted by Pintails and Shovellers (dabbling ducks) which prefer shallow water. The increasing number of these ducks in the central position is an inexpensive indicator of decrease in the depth of the lake. Amphibious/ marshy flowering plants are found to dominate the area replacing aquatic species like Nymphea and emergents like Typha. This has affected the nesting habit of birds like Pheasant Tailed Jacana. The aquatic weeds like Ipomoea carnea and I. aquatica, has covered the banks, nearly invading the fringe vegetation. Birds like Spot Bill Ducks favouring this have increased in number. Little Cormorant and Black Winged Stilts which favour organically polluted water (Gole, 1985) are also increasing in number. This can be further supported by the variation in the Dissolved Oxygen content of water as it is supposed to be the best indicator of the status of surface water quality.(Hem, 1970 ).

Table 2 highlights the alteration in water quality which is an indication of ever increasing stress on the water body for discharge of waste into it, which necessarily ruled out the possibility of supply of water for drinking purpose. 

Table 2 Physico-chemical and Microbial Analysis

This trend in water quality has been reflected in an increase in fishes like Tilapiawhich tolerate organic pollution. Introduced fishes like these outcompeted the native fishes like Cirrhinus fulungee (Syhes) Reba and Salmostroma boopis (Geinaces), the former believed to have become locally extinct. Euglena and Oscillatoria are found to be constant species during plankton analysis. Bivalves which prefer unpolluted water were replaced by pollution tolerant Bellamya bengalensis (Raut et al, 2001). 

For the eco-restoration of Pashan Lake, appropriate management strategies like

1. Diversion of sewage line from the lake. 

2. Dredging of silt and removal weeds.

3. Planting native trees like Acacia nilotica and Zizyphus jujube which are favoured for nesting istead of exotics like Eucalyptus around the lake.

4. Allowing controlled grazing by cattle to keep check on Ipomea.

5. Planting of trees on nearby hills to avoid runoff.

Acknowledgement :- 

We are thankful to HOD to provide necessary laboratory facilities. Thanks  are also due to RANWA for providing technical guidance in conducting the project.

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APHA, AWWA AND WEF; 1992 . Standard Methods for examination of water and waste water. (18 th edition ).

GHATE, V.S. AND Vartak, V.D1981 Studies on aquatic flowering plants of Greater Pune area. Part I. Enumeration. Jr. Poona Uni.(Sci. and Tech.) 54:121-129. 

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