FACTBOX-Key facts about the disappearing Aral Sea

June 24 (Reuters) - The Aral Sea, once the world's fourth largest lake, has shrunk by 70 percent in recent decades in 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.

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 metres, 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 risen, according to the World Bank.

* 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. Average life expectancy is 66 years compared to 70 in Almaty.

* The first phase of a World Bank restoration project is due to be completed at the end of 2008. Total cost is $86 million, including a $64.5 million World Bank loan to the Kazakh government.

The aim is to secure the northern Kazakh pocket of the Aral Sea at 42 metres above Baltic Sea level and improve ecological conditions in the area. The project includes construction of the Kok-Aral dike which separates the northern sea from the southern part, and several hydraulic structures on the Syr Darya river.

* The World Bank is considering a follow-up project to improve environmental and economic conditions further, a scheme estimated to cost $300 million. It includes returning water to the port of Aralsk and nearby villages, rehabilitating delta lakes and improving river flows.

* Similar efforts have been impossible in Uzbekistan, where most river water is still directed to cotton production -- one of the main pillars of the Uzbek economy. The south part continues to shrink. Experts, including the World Bank, doubt the Aral Sea will be ever restored to its original size. (Editing by Catherine Evans)