# Mamallan Reservoir Explained: Chennai’s Thirst vs. a Living Wetland

URL: https://technosports.co.in/mamallan-reservoir-explained-chennais/  
Published: 2026-09-30  
Updated: 2026-09-30  
Author: Reetam Bodhak

Chennai needs water, and Kovalam’s marshes need protection. The Mamallan Reservoir sits right where those two needs collide.

It’s being developed as Chennai’s sixth major drinking water source, at an estimated cost of Rs 342.60 crore. It’s located in Chengalpattu district along the East Coast Road, across the Kovalam-Nemmeli backwater basin. [dtnext](https://www.dtnext.in/news/tamilnadu/fishing-community-eco-groups-renew-calls-to-drop-mamallan-project)[dtnext](https://www.dtnext.in/news/tamilnadu/fishing-community-eco-groups-renew-calls-to-drop-mamallan-project)

### Mamallan Reservoir: Project Snapshot

| Detail | Info |
| --- | --- |
| Location | Kovalam-Nemmeli basin, Chengalpattu |
| Area | 5,161 acres |
| Capacity | 1.65 TMC |
| Cost | Rs 342.60 crore |
| Purpose | Chennai’s drinking water security |

### Why Is It Being Opposed?

**Ecology.** Residents’ groups say it would encroach on the Kovalam-Nemmeli salt marsh, a habitat for over 200 resident and migratory bird species. Since it’s a wetland, it acts as a natural sponge, and hydrology matters here. If you’re new to the term, [Wikipedia’s wetland page](https://en.wikipedia.org/wiki/Wetland) is a good primer.

![](https://technosports.co.in/wp-content/uploads/2026/09/mamallan-1.jpg)

**Flooding.** Residents also fear the project could alter drainage patterns of the Pallikaranai and Kovalam marshland catchments. [thenewsminute](https://www.thenewsminute.com/tamil-nadu/chennai-omr-residents-oppose-mamallan-reservoir-over-flooding-and-wetland-concerns)

**Seawater risk.** Fishing communities and eco groups argue that studies by the Water Resources Department and IIT Madras did not adequately assess storm surges and seawater intrusion. One expert warned it could become a “large saltwater lake” if seawater breached the bunds. [dtnext](https://www.dtnext.in/news/tamilnadu/fishing-community-eco-groups-renew-calls-to-drop-mamallan-project)[dtnext](https://www.dtnext.in/news/tamilnadu/fishing-community-eco-groups-renew-calls-to-drop-mamallan-project)

**Livelihoods.** PMK leader Anbumani Ramadoss has said it threatens the livelihoods of around 5,000 fishing families. [newstodaynet](https://newstodaynet.com/2026/08/03/anbumani-urges-tvk-govt-to-shelve-mamallan-reservoir-project/)

### The Other Side of the Story

Supporters aren’t ignoring these concerns. One OMR activist argued a reservoir is essential given future drinking water demand. The reservoir is proposed to serve the OMR region, which still depends on private water tankers for part of its needs. [deccanchronicle](https://www.deccanchronicle.com/southern-states/tamil-nadu/opposition-swells-against-mamallan-reservoir-1981300)[thenewsminute](https://www.thenewsminute.com/tamil-nadu/chennai-omr-residents-oppose-mamallan-reservoir-over-flooding-and-wetland-concerns)

### Where Things Stand?

More than 50 organisations and over 1,100 citizens have petitioned the Chief Minister to scrap the project. Nearly 30 youth groups also marched in Chennai, demanding an independent environmental study. Sources reviewed did not show a final government decision, so check for fresh updates. [thenewsminute](https://www.thenewsminute.com/tamil-nadu/chennai-omr-residents-oppose-mamallan-reservoir-over-flooding-and-wetland-concerns)[verified](https://community.verified.realestate/article/mamallan-reservoir-under-fire-as-youth-groups-rally-to-protect-marshlands/)

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### FAQs

### **Q1. Why is Mamallan Reservoir being built?**  

It aims to add a sixth major drinking water source for Chennai. Backers see it as vital for long-term supply.

### **Q2. Why do fishers and residents oppose it?**

  
  
They fear flooding, wetland loss, seawater intrusion and damage to fishing livelihoods. Many want an independent study first.