The Tamil Nadu government has received final Coastal Regulation Zone (CRZ) clearance from the Tamil Nadu Coastal Zone Management Authority for the construction of a large new reservoir near Kovalam. With this crucial green signal, the long-pending project aimed at strengthening Chennai’s long-term water security is now set to enter its first phase of construction.

The reservoir will be developed over 4,375 acres at an estimated cost of ₹471 crore. It is designed to store up to 2.25 TMC of surplus monsoon and floodwater annually, making it the city’s sixth major reservoir.

Strategic Location Between ECR and OMR

The reservoir will be created close to the shoreline between the East Coast Road (ECR) and Old Mahabalipuram Road (OMR) corridors in the Thiruporur–Kovalam sub-basin. This location allows the project to intercept excess floodwater flowing through the entire coastal catchment, unlike conventional hill dams that capture runoff only from limited upstream areas.

According to the Water Resources Department, coastal reservoirs are more efficient for flat, densely urbanized coastal regions as they store floodwater in estuarine zones and regulate seawater intrusion.

170 MLD Water Supply for Extended GCC Areas

As per the official project document, the reservoir will directly supplement Chennai’s drinking-water supply with up to 170 million litres per day (MLD) for nearly nine months every year.

Water from the reservoir will be distributed to extended areas under the Greater Chennai Corporation, including:

• Sholinganallur
• Medavakkam
• Pallikaranai
• Siruseri
• Kelambakkam
• Mamallapuram
• Other rapidly developing southern and IT corridor zones

Once commissioned, the reservoir alone is expected to contribute 17.17% of the city’s present water demand, significantly easing pressure on existing water sources.

Groundwater Recharge and Seawater Intrusion Control

Beyond surface storage, the project is expected to deliver major environmental benefits. The reservoir will:

• Indirectly enhance groundwater recharge
• The reservoir will act as a freshwater barrier that prevents salty seawater from pushing into underground freshwater sources along the coast.
• Improve long-term water sustainability for peri-urban and coastal communities

These benefits are particularly important for southern Chennai, where rapid real estate growth and rising population have placed heavy stress on groundwater systems.

Why Coastal Reservoirs Are Different from Hill Dams

The Water Resources Department has clarified that traditional mountainous dams capture runoff from only limited upstream catchments. In contrast, coastal reservoirs store water in estuaries and floodplains, enabling:

• Capture of floodwater from the entire catchment
• Better flood mitigation
• Reduced dependency on distant river systems
• Improved resilience against drought cycles

This makes the Kovalam reservoir a critical adaptation project for Chennai’s changing climate and urban expansion.

A Major Boost to Chennai’s Long-Term Water Security

With CRZ clearance now secured and tenders already floated for the first phase, construction is expected to commence shortly. Once operational, the new reservoir will become one of the most important additions to Chennai’s water infrastructure in decades, supporting:

• Expanding residential corridors
• IT and industrial zones along OMR
• Coastal tourism hubs near Mamallapuram
• High-density suburban housing clusters

The project directly aligns with Chennai’s long-term strategy to diversify water sources beyond monsoon-dependent surface reservoirs.