Odisha

Chilika Lake, spanning parts of Puri, Khordha, and Ganjam districts, is India's and Asia's largest brackish-water coastal lagoon, with an area that varies seasonally between roughly 900 and 1,165 km² (it is also frequently cited as the second-largest coastal lagoon in the world, after New Caledonia's lagoon, so phrase your answer as "Asia's largest" to stay safely correct across sources). It formed as a lagoon: a barrier sandspit sealed off a shallow bay of the Bay of Sea, leaving a body of water that mixes seawater (entering through a narrow mouth) with freshwater from several rivers draining into it, producing the brackish (part-salt, part-fresh) water that defines a lagoon. It was designated India's first Ramsar site, in 1981 — one of the very first two wetlands in the entire country to receive the designation.

Chilika is ecologically exceptional on two separate counts. First, it holds India's only resident population of the Irrawaddy dolphin, a rare estuarine dolphin species; a 2007 census counted around 138 individuals in the lake. Second, it hosts one of Asia's largest congregations of migratory waterfowl each winter, with Nalabana Island — a roughly 15.5 km² island within the lagoon, declared a bird sanctuary in 1973 and now the core Ramsar-notified zone — recording counts of migratory birds reaching into the hundreds of thousands in peak years (one single-site count in 2008 recorded around 450,000 birds).

Chilika is also the standard current-affairs case study for lagoon restoration through deliberate re-engineering: by the late 1990s, the lagoon's natural mouth to the sea had silted up and shifted, cutting the tidal flushing that kept the ecosystem healthy and causing fish yields to collapse. In September 2000, authorities dredged a new artificial mouth through the barrier beach at Satapada/Satapura, based on detailed scientific and hydrological modelling — shortening the effective outflow channel by roughly 18 km. The intervention is now cited as a conservation success story: fish yields rose from around 1,269 tonnes in 1995–96 to nearly 11,878 tonnes by 2001–02, and Chilika was removed from the Montreux Record (Ramsar's list of sites facing adverse ecological change) in 2002 as a direct result — one of the very few Ramsar sites in the world to have been removed from that list.

Memory hook: "Chilika: first Ramsar site (1981), Asia's largest brackish lagoon, home to India's only Irrawaddy dolphins, and the lagoon that dug its own new mouth in 2000 to save itself." Four facts, one chained sentence.

Practice Recall: Before reading on, name the year Chilika was designated India's first Ramsar site, the rare dolphin species found only here in India, and the year its new artificial mouth was opened.

Answer: 1981; Irrawaddy dolphin; September 2000.

Chilika's internal geography is itself sometimes tested: the lagoon is conventionally divided into four ecological sectors running from north to south — a northern sector where freshwater river inflow dominates, a central sector of mixed brackish water (the most biologically productive zone and the one holding most of the dolphin sightings), a southern sector, and the outer channel connecting to the sea near the mouth — each with a different salinity gradient that shapes which fish and plant species dominate it. Kalijai Island, a small island within the lagoon holding a temple to the goddess Kalijai, is a popular pilgrimage and boat-tourism destination and is often paired in tourism-geography questions with Nalabana's bird-sanctuary status as Chilika's two named islands, one religious and one ecological.