Chennai may get one more reservoir as a source of its drinking water supply.
The Water Resources Department is studying technical feasibility of creating a riverine reservoir across the Kosasthalaiyar river at Sadayankuppam-Edayanchavadi in north Chennai. The reservoir, with a tail end regulator, would be formed on about 400 hectares of space available between the two arms of the Kosasthalaiyar under the Napalayam bridge.
Forming a freshwater body with bund raised to a depth of nearly six metre in the space available at the confluence point near Sadayankuppam would help conserve water often inundating neighbouring areas and prevent seawater intrusion, the officials said. It is the confluence point of Red Hills reservoir’s surplus course with the river.
Noting that the proposal would help address the altering cycles of flood and drought, the officials said the proposed storage structure would revitalise the groundwater, which had turned saline, in the coastal aquifer in the region. Drinking water could be provided to north Chennai areas like Manali New Town.
The two dilapidated check dams at Edayanchavadi and Sadayankuppam arms of the river would be converted into regulators. The reservoir, which would act as a flood cushion, would be designed to store a minimum of 600 million cubic feet (mcft) of water and store an additional 200 mcft groundwater through artificial recharge.
Several north Chennai areas have been heavily impacted as saline water ingress has extended about 15 km inland beyond Manali from the coast, the officials said. The department had announced that a study would be conducted at a cost of ₹5 crore to create riverine reservoirs in four locations on the Kosasthalaiyar riverbed this year.
Threat of salinity
Meanwhile, hydrogeologists have expressed concern over interventions close to the coast.
L. Elango, professor, department of Geology, Anna University, said there are possibilities of the region east of reservoir to become more saline during monsoon failures and the reservoir drying up.
Waterbodies may be created in upper reaches for groundwater recharge. Nature-based projects such as increasing mangroves in the triangular region and along the water courses may be chalked out.
Officials said the proposal would not affect mangroves as it was located away from the proposed site and ash pond of the thermal power plant would not be a source of pollution as it was away from the water spread area. Once the technical feasibility, design and detailed project report are ready, the State government will decide on funding the scheme.
