Reckless desilting could kill Doddakallasandra Lake’s rich biodiversity: Study

Ignoring ecological concerns, the ongoing restoration work of the city’s Doddakallasandra Lake through brute de-silting could kill its rich biodiversity, an ActionAid study has warned.

The Justice N K Patil Committee clearly mandates that de-silting should be minimal to remove only the sludge.

Polluted by years of sewage and chemical inflow, the 21.16-acre lake in Konanakunte, South Bengaluru, was taken up for restoration by the Bruhat Bengaluru Mahanagara Palike (BBMP) in July 2020. But local residents, who organised under the Doddakallasandra Lake Protection Committee, are clear that the waterbody’s biodiversity had to be protected at all cost.

Every lake has a foreshore, a corner of its area where water enters, and a bund region where the water is stored. The Justice Patil Committee had stipulated that de-silting be marginal or shallow at the foreshore and deepest at the bund area. This way, the report noted, the lake ecology could be supported since 70% of the bird species thrive on shallow waters.

But the ground reality came as a shocker for ActionAid and its 10 student volunteers who measured the lake bed gradient using GPS essentials on February 26. “Foreshore region height should be suitable for shallow waters, but it starts with 6-8 feet deep. It does not leave any room for shallow waters thereby loosing up to 70% of the bird diversity,” the report noted.

The team also found that values at foreshore and the island region were around 800-805 metres in different parts of both regions. “It seems that the height around the foreshore and some parts around the island region are similar. The area around the island region seems to be not de-silted appropriately to maintain the gradient.”

ActionAid’s Biodiversity Report had identified 354 trees of 42 species, 43 species of plants and shrubs, 37 species of butterflies, and 71 bird species in the lake’s ecosystem. Eleven of these were of migratory birds with two dubbed “nearly extinct” by the International Union for the Conservation of Nature, informs Raghavendra B Pachhapur, Programme Manager, ActionAid Association.

The Justice Patil panel is clear that the current practice of saucer shaped de-silting should be given up as it leads to huge bund making, creating storage capacity beyond the need. “Saucer-shaped deepening of lake bed will affect the wetland formation in the foreshore region of the lake, which is essential to filter the water that enters the lake and important from an ecological point of view.”