Bed dam planned across the Adyar to divert surplus water to quarries

A 3.9 km cut and cover channel is proposed from the dam at Kavanur

The Water Resources Department plans to build a bed dam across Adyar river downstream of Chembarambakkam reservoir and divert surplus water to Sikkarayapuram quarries to be used for the city’s water supply.

The Adyar carried flood water joining in the upper portion, apart from the surplus released from Chembarambakkam reservoir, during the recent rain.

The department recently submitted a proposal to build a bed dam across the river near Kavanur and divert water through a 3.9 km-long cut and cover channel to the Sikkarayapuram quarries. This new channel would have a carrying capacity of 400 cusecs (cubic feet per second).

The existing 2 km course branching out from Thanthikal channel would be improved to carry double its capacity of 50 cusecs. It carried water from Chembarambakkam and from catchment areas en route, such as Manapakkam and Sikkarayapuram, to the quarries.

“Attempts to increase the carrying capacity of this canal will demand tedious masonry work at the reservoir’s sluice and also more funds. We decided to build another channel that could transport floodwater faster to the quarries,” said an official. The proposal is under the scrutiny of the government.

The reservoir not only serves as a drinking water source but also feeds a few irrigation channels.

According to sources, in this season, the branch canal from Thanthikal channel brought a good quantity of water to the quarries, which are buffer sources for the city’s water supply. The 22 quarries in Sikkarayapuram received an inflow sufficient to store 2,000 million litres this season alone. Similarly, five quarries in Erumaiyur have 800 million litres of water. The depth of these quarries varies between 30 m to 52 m.

However, the Chennai Metropolitan Water Supply and Sewerage Board is focusing on drawing water from reservoirs and has kept these quarries as reserve. The Sikkarayapuram quarries have a combined capacity to store 350 million cubic feet.

There were suggestions that it could be increased up to 1,000 mcft if these quarries were merged as a single large source. However, it would need intervention and permission of various government agencies, sources said.

The Department of Geology, Anna University, suggested diverting surplus water from Chembarambakkam lake to the quarries through a combination of open channel and a pipeline.

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