The Aral Sea is a landlocked endorheic sea (a watershed from which there is no outflow of water, either on the surface as rivers, or underground by flow or diffusion through rock or permeable material) located in Central Asia. It lies between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south.
Since the 1960s, the Aral Sea has been shrinking, as the rivers that feed it (the Amu Darya and the Syr Darya) were diverted by the Soviet Union for irrigation.
The Aral Sea is heavily polluted, largely as the result of weapons testing, industrial projects, and fertilizer runoff before and after the breakup of the Soviet Union.
The major ecological problem is that diversion of the Amu Darya and Syr Darya rivers for irrigation has shrunk the Aral Sea dramatically; the Aral Sea has been drying up for about 40 years. This has brought about a number of ecological and economic problems for the sea and the area.
Russia decided in 1918 that the two rivers that fed the Aral Sea, the Amu Darya in the south and the Syr Darya in the northeast, would be diverted to try to irrigate the desert, in order to grow rice, melons, cereal, and also, cotton; this was part of the Soviet plan for cotton, or "white gold", to become a major export. (This did eventually end up becoming the case, and today Uzbekistan is one of the world's largest exporters of cotton).
The sea's surface area has shrunk by approximately 60%, and its volume by 80%. In 1960, the Aral Sea was the world's fourth-largest lake, with an area of approximately 68,000 km² and a volume of 1100 km³. By 1998, it had dropped to 28,687 km² and became the eighth-largest.
Over the same time period its salinity has increased from about 10 g/l to about 45 g/l. As of 2004, the Aral Sea's surface area was only 17,160 km², 25% of its original size, and still contracting.
Even the recently discovered inflow of submarine groundwater discharge into the Aral Sea will not in itself be able to stop the desiccation. This inflow of about 4 billion cubic metres per year is larger than previously estimated. This groundwater would originate in the Pamirs and Tian Shan mountains and seek its way through geological layers to a fracture zone at the bottom of the Aral Sea.
In 1987, the continuing shrinkage split the lake into two separate bodies of water, the North Aral Sea and the South Aral Sea; an artificial channel was dug to connect them, but that connection was gone by 1999 as the two seas continued to shrink. In 2003, the South Aral further divided into eastern and western basins; the evaporation of the North Aral has since been partially reversed.
Work is being done to restore in part the North Aral Sea. Irrigation works on the Syr Darya have been repaired and improved to increase its water flow, and in October 2003, the Kazakh government announced a plan to build a concrete dam (Dike Kokaral) separating the two halves of the Aral Sea.
The South Aral Sea, which lies largely in poorer Uzbekistan, was largely abandoned to its fate, but the project in the North Aral has brought at least faint glimmers of hope: "In addition to restoring water levels in the Northern Sea, a sluice in the dike is periodically opened, allowing excess water to flow into the largely dried-up Southern Aral Sea."
As it has dried, the South Aral has left behind vast salt plains, producing dust storms, and making regional winters colder and summers hotter. Attempts to mitigate these effects include planting vegetation in the newly exposed seabed.
As of summer 2003, the South Aral Sea was vanishing faster than predicted. In the deepest parts of the sea, the bottom waters are saltier than the top, and not mixing. Only the top of the sea is heated in the summer and it evaporates faster than would otherwise be expected. Based on the recent data, the western part of the South Aral Sea is expected to be gone within 15 years however the eastern part could last indefinitely.
