Pallikkaranai drainage swamp is a fresh water swamp adjacent to the Bay of Bengal near Chennai. It is located about 18 km south of Chennai city at latitude 12 o 54'40" and longitude 80 o 14'00".

This swamp is bounded on the East by Old Mahabalipuram road and South B-Canal, on the West by Tambaram - Velachery road, on the North by Velachery Village, on the South by Karanai - Navalur road. This swamp drains an area of 235 sq.km. and the surplus water from the swamp falls into the Bay of Bengal via Oggium Maduvu, B-Canal, Kovalam back waters and Kovalam creek.

The topography of the swamp is in such a way that it always retains some fresh water storage in it, thus forming a very useful and beautiful aquatic ecosystem. This swamp has many flora and fauna. Many aquatic lives like fish, frog, snails and many micro organisms are found here. Many birds feed and breed here. The swamp feeds more than   one thousand water buffaloes daily. The Chennai metropolitan development authority (CMDA) planned to divert the swamp area for other urban development purposes on a large scale which included industrial development. The CMDA appointed Mott Mac Donald International (MMI) of U.K to under take a study in the area and to suggest measures to render the area fit for development.

Then in the context of the "Singapore Corridor" which was then under the consideration of Government of Tamil Nadu (GOTN) for development in the swamp area, the CMDA engaged M/S KBN Engineering and Applied Sciences to conduct an EIA of the area in view of the proposed development. Unfortunately the consultants have under estimated the environmental impact and damage to this aquatic ecosystem.

But in the past two decades, the swamp has been encroached upon for other purposes like construction of an Engineering College, Arts College, Hospital, Sewage treatment plant, solid waste disposal, Madras Rapid Transport System (MRTS), NIOT buildings, firewood wholesale market etc. Thus about 30% of the swamp has already been diverted for other purposes.

But from the beginning the Tamil Nadu P.W.D had   their own reservations on diverting the swamp area for other purposes, as it would affect the draining capacity of the swamp and cause flooding in the adjacent areas. So P.W.D proposed the formation of a reservoir in the remaining area after delineating the area already encroached. This will prove to be a blessing in disguise if implemented.

This paper gives the hydrology, usefulness, environmental sensitiveness, biological diversity, socio-cultural aspects etc. associated with this aquatic ecosystem. It also explains how far the formation of a reservoir in the swamp would be effective in preserving this aquatic ecosystem.

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