Achankovil River, Achankovilaru in the vernacular, is formed by the confluence of several small streams originating from the hills of Rishimala, Pasukidamettu and Ramakkalteri in eastern
. This small river, less than 130 km long, passes through Mavelikkara,
and Karthikapally Taluks before joining the Pamba River at Veeyapuram in Alappuzha District
Pandalam, the place associated with Lord Ayyappa, is on the banks of this river. The Achankovil Dam is built on this river.