Asia's largest freshwater oxbow lake, located in Bihar, is:

Kanwar Lake (also called Kabartal Wetland or Kanwar Jheel) in the Begusarai district of Bihar is described as Asia's largest freshwater oxbow lake.

Formation:

• It was formed by the meandering of the Gandak river, as a loop of the river was cut off from the main channel.
• It lies in the floodplain between the Ganga and the Burhi Gandak, and expands greatly during the monsoon.
• Its area varies widely with the seasons, from about 26 to more than 60 square km.

Ramsar status:

Kanwar Lake was the first wetland of Bihar to be declared a Ramsar site.

Biodiversity:

• It is an important wintering ground for migratory birds from Central Asia, such as ducks, geese and waders.
• It supports about 165 or more bird species, including threatened species such as the Sarus crane and vultures.
• It also has many fish species and aquatic plants.

Protected area:

The Kanwar Lake Bird Sanctuary was notified in 1989.

Livelihoods and threats:

• Local people depend on it for fishing, farming and grazing.
• Drainage for agriculture, siltation, encroachment, illegal hunting and the spread of invasive weeds have shrunk the lake.

Oxbow lakes in India:

• Oxbow lakes are common on the floodplains of the Ganga, Brahmaputra and Kosi.
• In Bihar and Assam, they are known by local names such as "maun", "chaur" and "beel".

Ramsar sites of Bihar:

Kanwar Lake was followed by other Ramsar sites in Bihar, such as Nagi and Nakti bird sanctuaries (2024).

Why not the other options?

• ✗Sambhar is a saltwater lake in Rajasthan.
• ✗Kolleru is a large freshwater lake in Andhra Pradesh between the Godavari and Krishna deltas.
• ✗Bhimtal is a lake in the Kumaon hills of Uttarakhand.