Sea to disappear within 15yrs
2003-07-22 11:04
Paris - The Aral Sea is disappearing even faster than expected, according to a new study that says its southern part will have become a puddle just 15 years from now.
Once the world's fourth largest inland sea, the Sea began to be catastrophically depleted by schemes in the 1960s and 70s to dam the main rivers that feed it in order to grow cotton in arid Soviet Central Asia.
It is now a quarter of its size of 50 years ago and has broken into two fragments, the North Aral Sea, for which a rescue attempt has been launched, and the South Aral Sea, which has been virtually abandoned because of the cost of restoring it.
The first hydrographic survey of the South Aral Sea since the early 1990s has shown that its depth is plummeting and salinity soaring, the British weekly New Scientist reported Monday on its website.
Older Soviet-era models predicted that, at worst, the sea level would drop from 57 metres above sea level in 1965 to 34 metres in 2002, and would end up 1.6 times as salty as normal seawater in 2002.
But research led by Peter Zavialov from the Shirshov Institute of Oceanology in Moscow has found that the South Aral is now just 30.5 metres above sea level and 2.4 times saltier than seawater.
Zavialov believes the faster-than-expected evaporation and saltiness are due to a feedback mechanism.
Lots of salt is seeping into the South Aral Sea from its eastern banks. Very salty water is dense and so it sinks to the bottom of the sea.
That means the less salty layer, about 20 metres deep, lies at the top of the lake and is more exposed to summer heat and evaporation. The higher the rate of evaporation, the smaller this layer becomes, the researchers believe.
Zavialov's paper is published in full in the journal Geophysical Research Letters.
The desiccation of the Aral Sea is causing great environmental and health problems.
The receding sea bed has exposed huge salt plains that produce dust storms and spread disease. Fishing has been wiped out, and agriculture is close to following it.
The United Nations Environment Programme (UNEP) says that every day 200 000 tonnes of salt and sand from the uncovered sea bed are carried by the wind and dumped on farmland within a 300-kilometre radius of the sea, destroying pastures and arable land.