Once completed, the combined storage may go up by 2,500 mcft, say experts

In what could be a first initiative of its kind in several years, four major reservoirs that form the source of drinking water supply for the city will be dredged.

This is expected to improve storage capacity in the reservoirs at Poondi, Cholavaram, Red Hills, and Chembarambakkam. The water bodies supply nearly 65 % of the drinking water for the city.

While the dry beds of these lakes remind people of the severe drought, experts see it as an opportunity to remove silt accumulated over the decades.

According to records, the reservoir in Chembarambakkam existed from the Pallava period and those in Red Hills and Cholavaram were created around 1876-1877. Poondi reservoir was the last to be added among the four reservoirs and was created particularly to cater to the needs of Chennai in 1944.

Water goes waste

At present, the four reservoirs have a combined capacity to store 11 tmcft. But sources in the Water Resources Department, which maintains the reservoirs, said only 80% of their capacity could be stored due to the siltation. Despite copious rainfall, a huge volume of water drained into the sea, and this was glaring during the floods in 2015.

Although the projects had been implemented during different periods to strengthen bund and repair shutters, no major work had been carried out to dredge the lakes. The height of the bund of these lakes was raised up to two feet to increase storage by 200 mcft as part of one of the earlier projects. The department has now sent a proposal to the government to allow removal of ‘savudu’ soil (a coarse type of earth) and is awaiting government order. “We plan to deepen the lakes by at least one metre depending on the water spread area. We may get to store at least 2,500 mcft in the lakes once the dredging operation is over,” said an official.

Nearly 6.40 crore cubic metres silt is expected to be removed from the lakes and the proposal would bring revenue to the government through sale of ‘savudu’ soil that is commonly used for filling purpose. The work may begin within a month after receiving the State government’s nod.