In a bid to mitigate seawater intrusion in coastal aquifers north of Chennai, the Water Resources Department is constructing a combination of storage structures across Araniar river at Andarmadam, near Pazhaverkadu.
The Department has completed nearly 75% of the work on the barrage and a sub-surface dyke across the 130 m-wide river at a cost of ₹13 crore.
Officials said the storage structures were being built 3 km upstream of the confluence point of the Pazhaverkadu estuary.
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Water salinity
Although groundwater in the Minjur-Ponneri belt is available at a depth of 2-3 m, it has turned saline. Whenever backwaters flow into the river owing to tidal action, the salinity of the water would extend up to 5 km till Vanjivakkam.
“We have designed a combination of storage structures to address seawater ingress and help storage of floodwater and groundwater recharge. The sub-surface dyke built for a depth of 7 m at Andarmadam will prevent seawater intrusion into freshwater aquifers in the area,” said an official.
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The barrage, which is a storage structure with regulator arrangements, is built to store additional amount of water in the river.
The 2 m-high structure, with 11 shutters, is expected to help store 500 million cubic feet of water in the river.
“The flood carrying capacity of the river in the area is about 20,000 cusecs. Once the structures are completed, water flow in the river could be retained for an additional four months,” the official said.
Groundwater quality
It would help restore groundwater quality in 10 surrounding villages, including Sirupazhaverkadu, Vanjivakkam, Andarmadam, Pralayampakkam, Kattur and Kadapakkam in the Ponneri belt.
Several villages depend on the river and waterbodies in the region for cultivation, including of paddy, and for drinking water needs.
The project, which is being executed with financial assistance from the National Bank for Agriculture and Rural Development (NABARD), is expected to be completed in one or two months, the officials added.