BANGALORE: The number of water bodies in Bangalore has decreased by 35.09 per cent between 1973 and 1997. And the number of man-made lakes in the existing Bangalore City Corporation and Bangalore Development Authority area has fallen from 262 in 1960 to 81 lakes at present.

According to a study conducted by a team of scientists of the Centre for Ecological Sciences (CES), Indian Institute of Science, water bodies which were once the source of drinking water in Bangalore, no longer meet the requirements of the city.

Since Bangalore has no natural wetlands, they were built for many hydrological and agricultural purposes. Tanks were constructed for drinking purposes and in 1870 Bangalore, with an area of 40 square kms, supported 29 waterbodies.

However, most of the major tanks have been lost to the rapid urban development activities, says Prof. T.V. Ramachandra of CES. Darmombudi tank is now converted into the current city bus-stand, Miller's tank has been converted into a residential layout, a filled up Sampangi tank has given way to Kanteerva Stadium, Chelgatta tank has led to a golf course, the football stadium stands on Shuleh tank and Koramangala tank has been converted into a sports complex.

"Remote sensing data show that the Bangalore area supported 379 water bodies in 1973, 138 of which were distributed in the north and 241 in the south. This has been reduced to 96 (north) and 150 (south) respectively as on December 1997", says Prof. Ramachandra. Besides, due to removal of vegetation in the catchment area, siltation has occurred and the water-holding capacity of these bodies has diminished, explains Prof. Ramachandra.

These wetlands also act as recharge zones for ground water in the city area. The ground water in the city area. The ground water level has gone down from 35-40 ft to 250-300 ft in 20 years, lament ecologists.

As an example of the deterioration condition, Prof. Ramachandra gives the case of Kamakshipalya tank, situated in the western part of the city along the old Magadi Road. This tank, covering an area of about one hectare, was a source of drinking water to neighbouring areas till the mid '80s. But now the tank has four inlets, bringing in sewage from the upstream, resulting in acute pollution.

"The study also shows a 93 per cent reduction in the number of water bodies over a period of 100 years. The temporal and physical changes in the water bodies, apart from harming the populace have also harmed the biodiversity of flora and fauna in Karnataka", rues Prof Ramachandra.