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Session 4Limnology of Lakes, Reservoirs and Wetlands

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Chairman: Dr. Chakrapani B. K.

Rapporteur: Sudira H. S

Ecological Changes in the Irrigation Tanks of the Tiruvanamalai District of Tamil Nadu A Trend Study

Sampath K.


The present investigation was carried out during January and February 2002 on 88 irrigation tanks out of the 433 tanks surveyed 10 years ago in the tiruvanamalai district with the objectives of ascertaining the likely changes in bird population and threats. All the birds encountered were enumerated by walking over the bund around the tank. The various parameters like water level, encroachment, siltation, social forestry activity, infestation by weeds, submerged vegetation, agricultural practices carried out, nature of water surface, colour of water, hunting and trapping of birds and socioeconomic status of the people were investigated. Alltogether 212,227 birds belonging to 69 species were recorded. The density of birds which was 28.51 birds during the erstwhile study has marginally dropped to 25.04 birds during the present investigation. In the present study only 25 tanks became full this year and quantum of water received by other tanks varied widely. Almost all the tanks suffer from siltation and encroachment. In the 56% of the tanks which were brought under social forestry activiy, the area covered ranged from 10 to 75%. The record of 70% of tanks suffered from infestation during the previous investigation has increased by 13% now and the extent of infestation ranged from 10 to 100%. Except 10 tanks, which possessed sparse submerged vegetation all other tanks had moderate growth. The hundting and trapping of birds, which took place in 15% of the tanks during the previous study has increased by 5% over the years.

Address: Society for Environmental Education and Conservation
2/71, 5th Cross, Kanakasabai Nagar
Chidambaram 608 001. Tamil Nadu, India