Factbox: Key facts about the disappearing Aral Sea

MOYNAK, Uzbekistan (Reuters) - U.N. Secretary General Ban Ki-moon visited the shrinking Aral Sea on Sunday and urged regional cooperation to tackle what environmentalists describe as one of the worst man-made ecological disasters.

Lakes and seas are disappearing around the world, partly as a result of global warming but mainly due to mismanagement of water resources linked to irrigation projects.

The Aral Sea, once the world’s fourth largest lake, has shrunk by 70 percent in recent decades.

Other endangered sites include Central Asia’s second-largest lake, Balkhash, as well Lake Chad in Africa and Lake Qinghai, China’s largest expanse of inland water.

Below are key facts about the Aral Sea.

* Fifty years ago, the Aral Sea was the world’s fourth inland sea, after the Caspian Sea, Lake Superior and Lake Victoria. It started shrinking due to Soviet irrigation projects, its surface area declining by more than 50 percent, to 30,000 square km from 67,000 square km, between 1960 and 1996. The sea level dropped by 16 meters, according to the World Bank.

* The sea straddles the former Soviet Central Asian republics of Kazakhstan and Uzbekistan. It split into a large southern Uzbek part and a smaller Kazakh portion in 1990.

* Central Asia, one of the world’s driest regions, has two main rivers, the Syr Darya and the Amu Darya. Both used to feed the Aral Sea. In the 1960s Soviet planners built a network of irrigation canals to divert their waters into cotton fields in Uzbekistan and Turkmenistan, starving the sea of its life blood.

* Mismanagement of land and water resources has caused degradation extending to the entire Aral Sea basin, damaging fish production and causing high salinity and pollution as well as violent sand storms. Fresh water supplies have diminished and human health problems have increased, the World Bank says.

* Kazakhstan pledged to restore its portion of the Aral Sea when it gained independence from the Soviet Union in 1991. The Aral Sea region is among the poorest in the oil producing state. At least a quarter of its population lives below the poverty line, and the average monthly income is three times below that of Kazakh financial capital Almaty, according to official data.

Writing by Maria Golovnina and Conor Sweeney; editing by Philippa Fletcher