The largest rivers on Sumatra drain from west to east into the Strait of Malacca. In the north, the Asahan River once linked trade between the Batak people who live inland and the Malay people who live along the coast. The Asahan is now dammed, however, and produces hydroelectricity for the industries of North Sumatra. In the south, river ports such as Jambi on the Hari River and Palembang on the Musi River are located upstream, away from the extensive mangrove swamps and marshes of the coast. Passenger ferries and small riverboats provide services along the main rivers.