Vembanad Lake (Malayalam: പനാട്ടു്കായല കായല്, Vembanad Kayal or Vembanad Kol) is the longest lake in India , and the largest lake in the state of Kerala . It is also one of the largest lakes in India. A lake spanning several districts in the state of Kerala, it is known by different names in different localities viz. Punnamada Lake in Kuttanad , Kochi Lake in Kochi. The Port of Kochi is located around two islands (the Willingdon Island and Vallarpadam ) in a portion of this lake known as the Kochi Lake. The celebrated Nehru Trophy Boat Race is conducted in a portion of this lake, in the Kuttanad region, known as the Punnamada Lake. High levels of pollution have been noticed at certain hotspots of Vembanad backwaters.

Government of India has identified the Vembanad wetland under National Wetlands Conservation Program Punnamada Lake (Malayalam: നമടക്കായല്കായല്) is the portion of Vembanad Lake located in the Kuttanad region of the district of Alappuzha. It is in this part of the lake that the celebrated Nehru Trophy Boat Race is conducted.

Kochi Lake (Malayalam: ചിക്കായല്കായല്) is the portion of the Vembanad Lake located in and around the Kochi mainland. Among the several groups of small islands that the Kochi Lake forms home are, Vypin, Mulavukad , Vallarpadam, Willingdon Island etc. Kochi Lake is home to the Kochi Port which is build around the Willingdon Island, as well as the Vallarpadam island.

The Vembanad wetland system covers an area of ​​over 2033.02 km² making it the largest wetland system in India. Of this, an area of ​​398.12 km² is located below the MSL and a total of 763.23 km² is located below 1 m MSL. The lake is bordered by Alappuzha, Kottayam , and Ernakulam districts. It lies at sea level, and is separated from the Arabian Sea by a narrow barrier island. Canals link the lake to other coastal lakes to the north and south. The lake surrounds the islands of Pathiramanal , Perumbalam and Pallippuram . The Vembanad Lake is approximately 14 kilometers wide at its widest point. The lake is a part of Vembanad-Kol wetland system which extends from Alappuzha in the south to Azheekkode in the north, making it by far, India’s longest lake at just over 96.5 km in length. The lake is fed by 10 rivers flowing into it including the six major rivers of central Kerala namely the Achenkovil, Manimala , Meenachil, Muvattupuzha , Pamba and Periyar. The total area drained by the lake is 15,770 km², which accounts for 40% of the area of ​​Kerala. Its annual surface runoff of 21,900 Mm accounts for almost 30% of the total surface water resource of the state.