Tamil Nadu reservoir plan divides communities over water and wetlands
Tamil Nadu’s proposed Mamallan Reservoir is intended to address drinking-water shortages and flooding in the southern Chennai Metropolitan Area. The project has received coastal regulation clearance and construction began in January 2026, but fishing communities and environmental groups fear major changes to wetlands, fisheries, bird habitat and local water flows.
Tamil Nadu’s proposed Mamallan Reservoir is being presented as a way to improve water supplies and reduce flooding in the rapidly urbanising southern Chennai Metropolitan Area, but its planned construction across wetlands has prompted opposition. The Water Resources Department proposed the reservoir in the Kovalam sub-basin between the Old Mahabalipuram Road and East Coast Road. The project covers parts of Thiruporur and Thirukalukundram taluks in Chengalpattu district.
The project received Coastal Regulation Zone clearance and construction formally began in January 2026. The current TVK-led coalition government is also backing the scheme, according to the supplied report. Phase I would cover 1,770.5 hectares, with a water-spread area of about 17.71 square kilometres.
It would have a storage depth of three metres, a single-filling capacity of 1.655 TMC and annual storage capacity of about 2.25 TMC. More than 30 kilometres of earthen bunds and associated drainage and regulator systems are planned. Project documents say the reservoir could supply up to 170 million litres per day for nine months each year.
It is expected to serve about 50,000 people in 12 villages as well as expanding areas of the southern metropolitan region. The department also says the reservoir would store runoff from 69 upstream tanks and a free catchment, helping to reduce inundation, recharge groundwater and limit seawater intrusion. The catchment covers 41,408 hectares.
However, the site is described as a landscape of marshes, salt pans, backwaters and wetlands supporting fishing and birdlife. An environmental assessment identified 102 bird species and said migratory birds use the area for feeding and roosting during the monsoon. Fishing communities, residents and environmental groups fear that raising water levels from the present 0.5-to-1.5-foot range to about three metres would substantially alter the area’s hydrology.
The Madras Naturalists Society said the marshland’s biodiversity could not be replaced.
This independently written report is based on information supplied by the named publisher. Vertrix News has not independently verified the source report.