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Earth from Space: Declining Aral Sea

10/07/2009 5686 views 9 likes
ESA / Applications / Observing the Earth

These Envisat images highlight the dramatic retreat of the Aral Sea’s shoreline from 2006 to 2009. The Aral Sea was once the world’s fourth-largest inland body of water, but it has been steadily shrinking over the past 50 years since the rivers that fed it were diverted for irrigation projects.

By the end of the 1980s, it had split into the Small Aral Sea (north), located in Kazakhstan, and the horse-shoe shaped Large Aral Sea (south), shared by Kazakhstan and Uzbekistan.

By 2000, the Large Aral Sea had split into two – an eastern and western lobe. As visible in the images, the eastern lobe retreated substantially between 2006 and 2009. It appears to have lost about 80% of its water since the 2006 acquisition, at which time the eastern lobe had a length of about 150 km and a width of about 70 km.

The sea’s entire southern section is expected to dry out completely by 2020, but efforts are underway to save the northern part.

The Kok-Aral dike, a joint project of the World Bank and the Kazakhstan government, was constructed between the northern and southern sections of the sea to prevent water flowing into the southern section. Since its completion in 2005, the water level has risen in the northern section by an average of 4 m.

As the Aral Sea evaporated, it left behind a 40 000 sq km zone of dry, white salt terrain now called the Aral Karakum Desert. Each year violent sandstorms pick up at least 150 000 tonnes of salt and sand from the Aral Karakum and transport it across hundreds of km, causing severe health problems for the local population and making regional winters colder and summers hotter. In an attempt to mitigate these effects, vegetation that thrives in dry, saline conditions is being planted in the former seabed.

In 2007, the Kazakhstan government secured another loan from the World Bank to implement the second stage, which includes the building of a second dam, of the project aimed at reversing this man-made environmental disaster.

Envisat acquired these images on 1 July 2006 and 6 July 2009 with its Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution Mode to provide a spatial resolution of 300 m.

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