The most beautiful and popular part of the backwaters, the Vembanad Lake spans several districts in Kerala. The longest lake in India and the largest in Kerala, the Vembanad Lake is approximately 14 km wide at its broadest point. The total area drained by the lake is 15,770 sq. km, which accounts for 40% of the area of Kerala.

Fed by 10 rivers including the six major rivers of central Kerala namely Achenkovil, Manimala, Meenachil, Muvattupuzha, Pamba and Periyar, it boasts of a rich bio-diversity.

The gateway to the Great Backwaters is the magnificent eight-armed Ashtamudi Lake in Kollam, which connects to the vast Vembanad Lake that flows through Alappuzha and Kottayam districts, before opening out into the sea at the Kochi port.

Home to more than 20,000 waterfowls - the third largest such population in India, the Vembanad Wetland System is included in the list of wetlands of international importance, as defined by the Ramsar Convention for the conservation and sustainable utilisation of wetlands in 2002.

So called because of its 8 arms or channels, Ashtamudi Lake is the gateway to the backwaters. This 16 km long lake is the second largest in Kerala, with numerous navigable canals and rivers interconnecting almost all the regions of South Kerala. The Ashtamudi is also home to several endangered marine species.

Ashtamudi is home to 57 species of birds, of which 6 are migratory and 51 resident; 45 insect species, 26 species of butterfly and 97 species of fish.

Spread across the districts of Kollam and Alappuzha, the Kayamkulam Lake covers an area of 60 sq. km and merges with the sea at the Kayamkulam barrage. The lake used to be connected to the sea most of the time except during the dry season when a bar like formation separated it from the sea. Now the bar has been opened up permanently for the construction of the Kayamkulam Fishing Harbour.