In the early 19th century, Ulsoor lake was an important water body as it supplied water to the new Bengaluru Cantonment. About double the size of the current water body orginally, the lake was divided in half by a road in the early half of the 20th century. And today only the southern part remains. Sadly, it receives massive volumes of sewage from east Bengaluru. This sewage cannot be diverted as it flows through storm water drains, and diversion would starve the lake of fresh rain water. Unfortunately, the lake and its inlets have been rejuvenated using an engineering-heavy, cement and stone approach. The original vegetation-lined canals and wetlands no longer exist. These used to slow the inflow of water, filter out large pollutants, and decompose the sewage, cleaning the water that entered it.
Relying solely on electricity-intensive sewage treatment plants has not worked well for many lakes in Bengaluru because of the high cost involved and difficulties in maintenance. We need to explore a return to natural ecological ways of treating water. As Jakkur and Kaikondrahalli lakes have demonstrated, this can be done by restoring the wetlands, planting inlet channels with appropriate vegetation, creating floating islands that can be used to absorb excess nutrient load, aerating the lake at inlets, and experimenting with other natural approaches.
If we implement a number of low cost, low maintenance solutions, with regular monitoring of water quality by local residents involved in “citizen science,” Ulsoor lake could become a model of sustainable treatment for other lakes in the city to follow.
Professor of Sustainability at Azim Premji University...