To save a portion of the floodwater that routinely drains into the sea, a check dam is set to be built across the Kosasthalaiyar river in Thirukandalam, Tiruvallur district, 27 km from the city.
The Water Resources Department (WRD) will begin work in April, once the project’s design and technical aspects are approved of and hopes to complete it within a year’s time.
Another benefit of the check dam will be in the saving of huge amounts of water that are lost every time surplus water from the Poondi reservoir is released into the Kosasthalaiyar river during the monsoons.
This project, which was mooted during the formulation of the Krishna water supply scheme three decades ago, remained on paper for several years due to the opposition towards land acquisition.
However, now, the design of the check dam has been altered to ensure there is no land acquisition in the locality for the speedy execution of the project.
The check dam will be constructed between Tamaraipakkam anicut and Cholavaram lake.
Last year, the State government had announced that a large storage structure would be built in Thirukandalam, which is nearly 27 km away from Chennai, to store Krishna water received from Andhra Pradesh and to meet the increasing drinking water needs of the expanded metropolis. However, the plan had to be dropped, as it would involve acquisition of several plots of private land to increase the river’s width and would inevitably result in a delay.
Officials of the WRD said that unlike a normal check dam built at a height of up to 1.5 metres this structure will be nearly 6.5 m high.
The river’s flood banks, which have eroded in some spots owing to sand mining, will also be raised up to a height of 10 metres.
Only then, about 150-200 million cubic feet of water, which is equal to one week of the city’s water supply, can be stored in the 195-metre wide river.
The structure will help retain surface water for nearly 9 km on the river. Ground water in surrounding villages, including Thirukandalam and Arikambedu, will be recharged once the check dam is completed.
At present, the water table in the area has dipped below 100 feet, owing to illicit sand mining. Several farmers have been forced to give up paddy cultivation and move to growing flowers, for want for water. Officials said the check dam is expected to increase the water table by at least a few metres.
A major share of the project cost of Rs. 35 crore, is being funded by the National Bank for Agriculture and Rural Development.
Means of conveying water from the storage structure for Chennai’s water needs will be decided depending upon the amount of water to be stored and when water is available, officials said.