Chilika Lake

Also called: Chilka · Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Class 7, Ch 1 "Geographical Diversity of India"; Class 11, Ch 5 "Natural Vegetation"

Meaning

Chilika Lake (also called Chilka) is Asia's largest brackish-water lagoon. It is a shallow, partly salty body of water on the Odisha coast, at the south-western edge of the Mahanadi delta, and a long sandy ridge separates it from the Bay of Bengal [3].

• It matters because it is where river water meets sea water. It feeds large fisheries and birds.
• It was one of India's first two Ramsar sites (1981) [2].
• It is also India's best-known example of a lake that was saved by restoring its water flow.

Explanation

How a lagoon like Chilika forms

• Lagoon: a shallow body of water near the coast. A sand bar or barrier island separates it from the sea, but it still joins the sea through one or more mouths.
• Formation (cause → process → result):
• Cause: waves and coastal currents carry sand along the shore.
• Process: the sand piles up into a bar or spit (a long, narrow ridge of sand) across the opening of a bay.

• Result: the water behind the bar is cut off from the open sea, except at its mouths. This makes a lagoon.

• In the classification of lakes by origin, Chilika is a lagoon (coastal) lake. It is the same type as Pulicat and Vembanad, and is not tectonic, glacial or crater-made.

Why its water is brackish

• Brackish water is partly salty. It is less salty than the sea and saltier than a river.
• Water comes into Chilika from two directions:
• Sea water flows in and out through the mouth with the tides.

• River water pours in during the monsoon from the Mahanadi delta side.

• Result: the salinity (saltiness) changes sharply by season and from one part of the lake to another [3].

• The lake is less salty in the monsoon, when fresh water comes in.

• Parts near the mouth are saltier than parts near the river inflow.

• This mix of fresh and salt water supports many kinds of life.

Life in the lagoon

• Fish: Chilika supports 118 fish species [3].
• Birds: 33 waterbird species breed, spend the winter or stop over here (Ramsar Information Sheet) [3].

• Nalabana Island is a bird sanctuary inside the lake. Large flocks of winter migratory birds gather there.

• Irrawaddy dolphins live in the lagoon, especially near Satapada.

Decline and restoration

• How it was harmed:
• Silt from the catchment slowly choked the mouth.
• Less sea water came in, so salinity fell.
• Freshwater weeds spread, and the fish catch dropped.

• Chilika was put on the Montreux Record in 1993. This is the Ramsar list of sites whose ecological character has changed, is changing or may soon change because of human interference [4].

• How it was saved:

• In 2000, the Chilika Development Authority opened a new mouth to the sea.
• Sea water came back, the weeds died off, and the fish and dolphins recovered.
• Chilika was removed from the Montreux Record in 2002.

Where it occurs

• State and districts: Odisha, spread over Puri, Khurda and Ganjam districts [3].
• Setting: at the south-western edge of the Mahanadi delta, on India's east coast. A sandy ridge separates it from the Bay of Bengal [3].
• Places inside the lake:
• Satapada: the main area for Irrawaddy dolphins.

• Nalabana Island: a bird sanctuary for winter migratory birds.

• Ramsar status: designated 1 October 1981, covering 1,16,500 ha [3][2].

• NCERT: Class 9 (Contemporary India-I, "Drainage") names Chilika as a lake on the east coast.
• Other lagoons of the same type in India: Pulicat (AP–Tamil Nadu border, north of Chennai) and Vembanad (Kerala, Alappuzha to Kochi).

Don't confuse with

• Pulicat Lake: India's second-largest brackish lagoon, on the AP–Tamil Nadu border. The barrier island Sriharikota (home of the Satish Dhawan Space Centre) separates Pulicat from the sea, not Chilika. Pulicat is not a Ramsar site (as on 21 April 2026) [2].
• Vembanad Lake: India's longest lake (Kerala). As a Ramsar site, Vembanad–Kol (1,51,250 ha) is bigger than Chilika (1,16,500 ha), so Chilika is not India's second-largest Ramsar site [2].
• Kolleru Lake: a freshwater lake between the Godavari and Krishna deltas in Andhra Pradesh, not a brackish lagoon. Its main damage came from fish and prawn ponds dug across the lake bed, not from a choked sea mouth.
• Sambhar Lake: an inland saline lake in Rajasthan with no link to the sea. Its salt comes from evaporation in a closed basin. Chilika's salt comes from sea water entering through its mouth.

Prelims Hooks

• Chilika = Asia's largest brackish-water lagoon, in Odisha at the south-western edge of the Mahanadi delta [3].
• India's first two Ramsar sites (1981): Chilika (Odisha) and Keoladeo Ghana National Park (Rajasthan) [2].
• Order of large Ramsar sites by area: Sundarban (4,23,000 ha) > Vembanad–Kol (1,51,250 ha) > Chilika (1,16,500 ha) [2].
• Montreux Record: Chilika was added in 1993 and removed in 2002, after a new mouth was opened in 2000 by the Chilika Development Authority.
• Feature–place pairs: Irrawaddy dolphins → Satapada; bird sanctuary → Nalabana Island.
• Trap: Sriharikota separates Pulicat, not Chilika, from the Bay of Bengal.

Mains Points

• Lagoons are where the drainage system meets the sea.
• Chilika takes monsoon river water from the Mahanadi delta and tidal sea water through its mouth. This makes its salinity change by season and by place [3].

• This brackish mix supports 118 fish species and 33 waterbird species [3], and fishing communities depend on it (GS-I, GS-III).

• Catchment damage → lagoon decline.

• Deforestation in the catchment → siltation → the mouth chokes → less sea water and lower salinity.

• Result: freshwater weeds spread, the fish catch falls, and the lake goes onto the Montreux Record (1993).

• Restoration works when it fixes how water flows.

• Opening a new mouth in 2000 brought sea water back, revived fish and dolphins, and got Chilika removed from the Montreux Record in 2002.
• The model is a dedicated lake authority (the Chilika Development Authority) plus Ramsar listing. India's Ramsar list has grown to 99 sites (as on 21 April 2026) [2], and this model can be used for other stressed wetlands (GS-III environment).

Related concepts

• Wular Lake
• Loktak Lake
• Pangong Tso
• Pulicat Lake
• Kolleru Lake
• Vembanad Lake
• Sambhar Lake

Read more

• Lakes of India