The Kerala backwaters are a chain of brackish lagoons and lakes lying parallel to the Arabian Sea coast (known as the Malabar Coast) of Kerala state in southern India. The network includes five large lakes linked by canals, both man made and natural, fed by 38 rivers, and extending virtually half the length of Kerala state. The backwaters were formed by the action of waves and shore currents creating low barrier islands across the mouths of the many rivers flowing down from the Western Ghats range.
The Kerala Backwaters are a network of interconnected canals, rivers, lakes and inlets, a labyrinthine system formed by more than 900 km of waterways, and sometimes compared to the American Bayou. In the midst of this landscape there are a number of towns and cities, which serve as the starting and end points of backwater cruises. National Waterway 3 from Kollam to Kottapuram, covers a distance of 205 km and runs almost parallel to the coastline of southern Kerala facilitating both cargo movement and backwater tourism. The important rivers for north to south are the Valapattanam (110 km.), Chaliyar (169 km.), Kadalundipuzha (130 km.), Bharathappuzha (209 km.), Chalakudy (130 km.), Periyar (244 km), Pamba (176 km), Achankovil (128 km.) and Kalladayar (121 km.). Other than these, there are 35 more small rivers and rivulets flowing down from the Ghats. Most of these rivers are navigable up to the midland region, in country crafts.
Vembanad is the largest of the lakes, covering an area of 2033 km². The lake has a large network of canals that meander through the region of Kuttanad.
The backwaters have a unique ecosystem: freshwater from the rivers meets the seawater from the Arabian Sea. A barrage has been built near Thanneermukkom, so that salt water from the sea is prevented from entering the deep inside, keeping the fresh water intact. Such fresh water is extensively used for irrigation purposes.
Many unique species of aquatic life including crabs, frogs and mudskippers, water birds such as terns, kingfishers, darters and cormorants, and animals such as otters and turtles live in and alongside the backwaters. Palm trees, pandanus shrubs, various leafy plants, and bushes grow alongside the backwaters, providing a green hue to the surrounding landscape.