Hari Rud (hä`rē r
d), river, c.700 mi (1,130 km) long, rising in the Kuh-e Baba range, central Afghanistan, and flowing west and then north into the steppes S of the Kara Kum desert in Turkmenistan; its lower course forms part of the Afghanistan-Turkmenistan border. The river irrigates the fertile valley of Herat, NW Afghanistan, and ends in the Tejen oasis in Turkmenistan, a wheat, cotton, and cattle raising area. In Turkmenistan, the river is called Tejen; in ancient times it was known as the Arius.