The river flows in a north-easterly direction, cutting through the upper course of the deep valley in the
Barisan Mountains in Toba Regency, then flows through the Asahan Regency and eventually empties into the Strait of Malacca The largest city on the Asahan is
Tanjungbalai, Asahan with a population of more than 180,000 people. The river houses the
Sigura-gura Dam, which supplies power to the North Sumatran Province. Tributaries of the Asahan include the Silang,
Silau, Nantalu, Masihi, Lauran, and Baru River. == Geography ==