Amu Darya

Amu Darya (ancient Oxus; Russian Amudar’ya; Turkmen Amuderya; Uzbek Amudaryo; Tajik Dar”yoi Amu), largest river of Central Asia. The Amu Darya is formed by the junction of the Pandj and Vakhsh rivers in the Pamirs mountain region, on Tajikistan's southwestern border. The river measures 2,540 km (1,580 mi) in length. It follows a northwest course between Tajikistan and Afghanistan, continues northwest between Turkmenistan and Uzbekistan, and then flows north through Uzbekistan into the Large Aral Sea (Russian Bol’shoye Aral’skoye More), which separated from the northern Small Aral Sea (Russian Maloye Aral’skoye More) in the late 1980s. The Amu Darya’s main tributaries are the Panj and Vakhsh rivers, which both rise in the Pamirs. The Panj forms part of the boundary between Tajikistan and Afghanistan, and the Vakhsh flows through southwest Tajikistan to join the Amu Darya at the Afghan border. Since the 1950s the Amu Darya has been heavily tapped for irrigation, 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. Inflows from the Syr Darya River, which empties into the Small Aral Sea from the east, have also drastically diminished in recent decades. As a result, the volume of the Aral Sea dropped by about 80 percent between 1960 and 1996. The largest single cause of the decline in the Amu Darya’s water level is the Garagum 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 cu km (about 5 cu mi) per year—about one-ninth of all the water diverted in the Aral Sea basin. Reduced water flow has restricted water transportation 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 extensive vegetation, but most of the delta has dried up 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 westward 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 overflows went into Lake Sarykamysh.