CHENNAI: The Tamil Nadu State Wetlands Authority has drastically reduced the proposed interim Zone of Influence (ZoI) around the Pallikaranai Ramsar wetland from 3,358 hectares to 128.19 hectares, a contraction of about 96%, raising questions over whether the revised boundary adequately accounts for the marsh’s wider hydrological connections. Madras high court will pronounce its verdict in the case on Wednesday.
The authority said the revised interim zone covers parcels across 36 survey numbers that could potentially affect the hydrology of the Ramsar site. The exercise followed representations from landowners, developers and others, as well as a review of historical satellite imagery, drainage pathways, land use, infrastructure and hydrological connectivity.
The proposed zone is an interim arrangement and not the final delineation, the authority clarified. The final boundary will be determined after scientific and cadastral exercises and ground-truthing under the Wetlands (Conservation and Management) Rules, 2017.
However, an urban ecologist, who worked extensively on protection of the marsh and doesn't want to be identified, questioned whether the revised proposal adequately captures the landscape through which water reaches the marsh. “Essentially, what they have done is all the channels that drain into Pallikaranai marsh, which they have considered as Zone of Influence. They have not considered the water bodies, only the channels,” the ecologist told TNIE.
It was argued that water does not flow exclusively through defined channels. During heavy rainfall, water also moves as sheet flow across low-lying terrain, making the surrounding wetlands and open spaces important to the marsh’s hydrological functioning.
The expert also pointed to 64 satellite wetlands that, according to the ecologist, have not been adequately considered in the revised exercise. These water bodies and their connecting drainage systems form part of the wider landscape that sustains Pallikaranai.
The Citizen’s Charter for the Pallikaranai Watershed, published last month by the Chennai Wetlands Action Collective and Oorvani Foundation, describes a 306-sq-km watershed with a cascade of 65 major lakes and hundreds of ponds. It cites a survey identifying 452 water bodies, of which 165 have already been lost. The report advocates watershed-based planning that protects natural water flows and restores disrupted hydrological connections.
The ecologist also questioned the significance of including small government-owned parcels and drainage channels that are already subject to public control, arguing that their inclusion alone may not substantially improve the marsh’s protection if surrounding developable land remains outside the zone.
In his statement, PMK president Anbumani Ramadoss questioned the authority’s priorities, alleging that the swift reduction of the zone appeared intended to protect construction interests. He said the buffer must be scientifically determined, while the wetland’s own boundaries must be surveyed and officially notified to prevent further encroachment.
The authority, however, has proposed safeguards within the interim zone, including prohibiting obstruction or diversion of established drainage channels, dumping waste into drainage pathways, discharging untreated sewage into connected watercourses, permanently altering hydrological connections and permitting highly polluting Red Category industries. Construction would require a no-objection certificate from the District Level Wetlands Management Committee.
The central question is whether these safeguards, applied across a much smaller area, can protect the ecological integrity of a marsh that receives water from a far larger catchment. A scientifically defensible boundary must account for both identifiable drainage channels and the wider landscape through which floodwater moves.
The reduction may address immediate concerns over development restrictions, but the final exercise will need transparent mapping, field verification and an assessment of connected wetlands, low-lying areas and historical flood pathways, experts say.