Amu Darya

Amu Darya (ancient, Oxus; Russian, Amudarya; Turkmen, Amuderya; Uzbek, Amudaryo; Tajik, Dar'yoi Amu), largest river of Central Asia. The Amu Darya originates at the junction of the Panj and Vakhsh rivers, its main tributaries, in the lofty Pamirs, and is about 2,495 km (about 1,550 mi) in length. It follows a north-west course, forming the border between Tajikistan and Afghanistan, then continues north-west between Turkmenistan and Uzbekistan, and then north through the Karakalpakstan (Qoraqalpoghiston) region into the Large Aral Sea (Russian, Bolshoye Aralskoye More), which separated from the Small Aral Sea (Russian, Maloye Aralskoye More) in 1988.

Since the 1950s the river has been heavily tapped for irrigation (mostly of cotton, which uses large quantities of water), which has greatly reduced its water level and the amount of water reaching the Aral Sea. During the 1980s, several years passed in which little or no water reached the Aral Sea from the river. As a result, and due to the fact that inflows from the Syr Darya have also drastically diminished in recent decades, the volume of the Aral Sea dropped by about 80 per cent between 1960 and 1996. The largest single contributor to the decline in the Amu Darya's water level is the Kara Kum Canal, the longest canal in the former Soviet Union and one of the longest in the world. Near the town of Oba the canal diverts water from the river at the rate of about 12 cubic km (5 cubic mi) per year—about one ninth of all the water diverted in the Aral Sea basin. Reduced water flow has restricted water transport on the Amu Darya, which was once navigable for light draft vessels over nearly half its length. The lower reaches of the river once contained a large delta that supported an extensive vegetative cover, but most of the delta has disappeared due to reduced water flow.

Over the centuries the river has shifted its course several times. In the 3rd and 4th millennia bc the Amu Darya flowed westwards from the Khorezm Oasis into Lake Sarykamysh, and from there to the Caspian Sea. From the 17th century until the 1980s the Amu Darya emptied exclusively into the Aral Sea, except during periods of intense flooding, when the overflow went into Lake Sarykamysh.