Some areas in the southern suburbs were spared of waterlogging during the recent heavy rain, thanks to the ongoing restoration work at Sembakkam lake.
Spread over 100 acres, the lake faced several challenges, inlcuding encroachments and sewage pollution. It did not have a defined supply channel and surrounding localities were waterlogged whenever the lake filled up.
However, areas such as Chitlapakkam and Sri Sarvamangala Nagar were not warlogged during the recent rain because of the ongoing eco-restoration work. The project is being implemented jointly by the Nature Conservancy India, the Care Earth Trust and IIT-Madras with permission from the Water Resources Department (WRD).
While the flood regulator constructed by the NGOs helped in regulating the surplus water discharge, the channel built by the WRD diverted water from upstream localities such as Selaiyur, Rajakilpakkam and Chitlapakkam to Sembakkam lake.
Moreover, the storage capacity of the waterbody has been increased by 36% because of deepening of the lake and strengthen of the embankment. Efforts are on to prevent flow of sewage into the lake and also to install a wastewater treatment system.
Nisha Priya Mani, project manager-cities, Nature Conservancy India, said nearly 6-7 million litres of sewage is estimated to be flowing into the lake daily. Work would be taken up to treat sewage with constructed wetlands with phragmites species that would act as a biofilter and absorb pollutants in the wastewater flowing into the lake.
The low-cost technology would use sedimentation basins and aeration system to reduce pollutants, improve water quality and restore lake habitat. The level of dissolved oxygen, one of the quality parameters, would be increased from the present 2 mg per litre to 4 mg/l once the work was completed in six months, she said.
The progress of work was discussed periodically with residents. Various challenges, including the impact of the pandemic and the heavy rain last year, figured at a meeting held last week.
M. Ravi, secretary, Sri Sarvamangala Nagar Residents’ Welfare Association, said the eco-restoration work and culverts prevented waterlogging in the area. “We have suggested removal of encroachments behind Thiru.Vi.Ka. Nagar and Vinobaji Nagar. The lake boundary must be demarcated and fenced. Provision of sewer connections must be expedited in Pallavaram,” he said. Residents wanted a water channel to divert water from Pachamalai Hills into Sembakkam lake.
