Amu Darya or Amudarya (both: ämōō´ däryä´, ä´mōō där´yə), river, c.1,600 mi (2,580 km) long, formed by the junction of the Vakhsh and Pandj rivers, which rise in the Pamir Mts. of central Asia. It flows generally northwest, marking much of the northern border of Afghanistan with Tajikistan, Uzbekistan, and Turkmenistan before flowing through the Kara Kum desert of Turkmenistan and Uzbekistan, and entering the S Aral Sea through a delta. The river drains c.180,000 sq mi (466,200 sq km). It flows swiftly until it reaches the Kara Kum where its course braids into several channels.
The Amu Darya provides water for irrigation, but this heavy draw on its water has prevented the Amu Darya from replenishing the Aral Sea. Additionally, the river's water is contaminated by agricultural runoff and industrial wastes released in its basin. The Kara Kum Canal (c.500 mi/800 km long) carries water from the Amu Darya near Kelif across S Turkmenistan to Ashgabat and supplements the flow of the Tejen and Murgab rivers. The Amu Darya is paralleled by the Trans-Caspian RR, which has lessened the river's importance as a transport route. In ancient times the Amu Darya was called the Oxus and figured importantly in the history of Persia and in the campaigns of Alexander the Great.
The Amu Darya, also known in the past as the Oxus River, forms the principal boundary between Afghanistan and the Tajik and Uzbek republics, a distance of about 680 miles (1,094 km). The Amu Darya begins in the Pamir mountains, runs a total distance of about 1,500 miles (2,414 km), and eventually empties into the Aral Sea.