Chilika Lake

Chilika Lake is a brackish-water coastal lagoon situated on the eastern coast of India, spanning the Puri, Khordha, and Ganjam districts of Odisha at the mouth of the Daya River where it meets the Bay of Bengal. It is the largest coastal lagoon in India and one of the largest brackish-water lagoons in the world, with a surface area that fluctuates seasonally between roughly 900 square kilometres in the dry season and over 1,165 square kilometres during the monsoon. Chilika holds particular legal distinction as the first Indian site designated under the Convention on Wetlands of International Importance (the Ramsar Convention, signed in Ramsar, Iran, in 1971), entered on the Ramsar List on 1 October 1981 along with Keoladeo National Park. The lagoon is separated from the Bay of Bengal by a long sandy ridge and connected to the sea through a tidal inlet, a hydrological feature central to its ecological character.

The ecological mechanics of Chilika rest on its salinity gradient, which makes it a transitional ecosystem between freshwater and marine environments. Freshwater enters from the western catchment via the Mahanadi distributaries and 52 inflowing rivers and rivulets, while seawater enters through the mouth connecting the lagoon to the Bay of Bengal. This mixing creates distinct salinity zones—the northern, central, southern, and outer channel sectors—each supporting different biotic communities. The lagoon functions as a critical wintering ground for migratory waterfowl arriving along the Central Asian Flyway, hosting more than a million birds at peak season from breeding grounds as distant as the Caspian Sea, Lake Baikal, and the Aral Sea. It supports over 225 species of fish and is the largest wintering ground for migratory birds on the Indian subcontinent.

Chilika is the only known habitat in India that supports a resident population of the Irrawaddy dolphin (Orcaella brevirostris), a species listed as Vulnerable on the IUCN Red List and protected under Schedule I of the Wildlife Protection Act, 1972. The Nalabana Bird Sanctuary, a 15.53 square kilometre island within the lagoon, was notified as a protected area in 1987 and submerges during the monsoon, re-emerging as a critical roosting site in winter. The lagoon also sustains a fishery economy on which roughly 200,000 fishers across more than 130 villages depend, harvesting prawn, crab, and fish, which links Chilika's ecological management directly to coastal livelihoods and social equity.

Management of Chilika falls to the Chilika Development Authority (CDA), constituted by the Government of Odisha in 1991 as a body for restoration and integrated management of the lagoon. The CDA's signature intervention was the hydrological restoration of 2000, when a new mouth was opened to the sea near Sipakuda to reverse the siltation and choking of the natural inlet that had reduced salinity and tidal flushing. This intervention restored the salinity gradient, revived fish and prawn yields, reduced invasive freshwater weed proliferation, and increased the Irrawaddy dolphin count. In recognition of these restoration outcomes, Chilika was removed from the Montreux Record in 2002—becoming the first site globally to be delisted from that register of wetlands under threat—and the CDA was awarded the Ramsar Wetland Conservation Award in 2002.

Chilika should be distinguished from adjacent wetland categories with which it is frequently confused. It is a lagoon, not a lake in the limnological sense, defined by its connection to the sea and its brackish salinity, distinguishing it from freshwater Ramsar sites such as Loktak Lake in Manipur or Wular Lake in Jammu and Kashmir. It differs from a Montreux Record listing, which is a register of Ramsar sites where ecological change has occurred or is likely; Chilika's history involves both inclusion and removal from that record. It is also distinct from a National Wetland or a Ramsar site simpliciter, as it carries the dual status of Ramsar site and host to a notified wildlife sanctuary under domestic statute.

Contemporary controversies surrounding Chilika centre on aquaculture encroachment, particularly illegal prawn gheri (enclosure) farming that has fragmented the lagoon and triggered conflict between traditional fisher communities and commercial operators, prompting Supreme Court and Odisha High Court interventions. Renewed siltation pressures, the periodic need to maintain artificial sea-mouths, the spread of invasive species such as Phragmites karka, and the threat of recurrent cyclones—including Cyclone Fani in 2019 and Cyclone Yaas in 2021, which altered the lagoon mouth—keep the lagoon's hydrology under continuous engineering management. Climate-driven sea-level rise and changing monsoon patterns introduce long-term uncertainty into the salinity regime that underpins both biodiversity and fishery yields.

For the civil-services aspirant and the working environmental policy practitioner, Chilika is a paradigmatic case study in wetland restoration, integrated catchment management, and the operational meaning of the Ramsar Convention's "wise use" principle. It illustrates how a science-based hydrological intervention can reverse ecological degradation while restoring livelihoods, and it anchors UPSC General Studies Paper III discussion of biodiversity conservation, the Central Asian Flyway, and India's domestic implementation of multilateral environmental agreements. Chilika's trajectory—from Montreux Record inclusion to award-winning delisting—remains the canonical Indian example of effective adaptive wetland governance.