As part of the measures to tackle floods and droughts affecting Chennai, the Water Resources Department (WRD) proposes to restore a cascade of tanks in the western suburbs and convert them into sources of drinking water.
The project, proposed under the Chennai City Partnership Programme, is under scrutiny, and awaits funds from the World Bank. The network of 10 urban tanks is spread from Thirunindravur to Retteri. Surplus water from each of these tanks drains into the subsequent one and reach Retteri.
The tanks include those at Thandurai, Sekkadu, Vilinjiyampakkam, Paruthipattu, Ayapakkam, Arabath eri, Ambattur and Korattur. Metrowater has already been developing the waterbody at Retteri as a source of drinking water.
WRD officials said many tanks in the Kosasthalaiyar sub-basin were neglected. As the areas around them were urbanised, links between the tanks went missing, with portions of the surplus channels having disappeared over the years.
This often led to flooding of the surrounding localities and wastage of rainwater that would have drained into these tanks.
Through this ₹26 crore restoration project, the WRD expects to mitigate floods in the vulnerable areas and augment storage for drinking purposes.
Capacity to be increased
The original capacity of the tanks is 965.50 million cubic feet (mcft), and the project will help to increase their capacity to 1,351.70 mcft and to recharge the groundwater table in neighbouring areas. Once the project is completed, the tanks together would have more storage than the new reservoir at Thervoy Kandigai Kannankottai, which can store 500 mcft.
The WRD plans to raise the full tank level of these waterbodies. Besides providing shutters and rebuilding weirs, which allow surplus water to flow out, the bunds would be fortified and foreshore bunds formed.
“We are also planning to construct an off-take channel from the stretch of the Cooum river near the Korattur check-dam. Once the check-dam is reconstructed, the stored water will be conveyed to the Thirunindravur tank,” an official said.
Measures will be taken to construct channels to bridge the gaps, especially near Thirunindravur and between Paruthipattu and Ayapakkam. However, sewage release into the tanks from Sekkadu to Retteri is a major challenge.
The surplus channel from Ayapakkam to Korattur, too, carries rainwater mixed with sewage.
