Kallada River is a major river discharging into the Ashtamudi Lake. The Kallada river, which originates near Ponmudi from the Kulathupuzha hills Western Ghats is formed by the confluence of three rivers, viz., Kulathupuzha, Chenthurnipuzha, and Kalthuruthipuzha, and after traversing a distance of about through virgin forests finally debouches into the Ashtamudi wetland at Peringalam near Kollam. With a maximum depth of at the confluence, it is Kerala's deepest estuary.