LONDON (TIP): All is not lost for the fastdisappearing Aral Sea, a saline lake in central Asia. Nasa satellites have discovered large amounts of water – almost half of its capacity – hidden in the central part of the watershed, raising hopes of reviving what was once the fourth largest itit in the worldit.

The Aral Sea It has lost 90% of its water volume in the last 50 years. The new data says although the long-term water picture for the Aral Sea watershed in Central Asia is bleak, short-term prospects are better than previously thought. Its watershed – the enormous closed basin around the sea – encompasses Uzbekistan and parts of Tajikistan, Turkmenistan, Kyrgyzstan and Kazakhstan. Kirk Zmijewski and Richard Becker of the University of Toledo, Ohio, wanted to find out whether all of the water was gone for good, or whether some of it might have ended up elsewhere in the watershed, behind dams or in aquifers.

They also wanted to gauge whether decreasing rainfall had contributed to the catastrophic water loss. The researchers used data from Nasa’s Gravity Recovery and Climate Experiment satellites to map monthly changes in mass within the watershed from 2003 to 2012. They mapped the entire Aral Sea watershed and found that each year throughout the decade, the watershed lost an average of 4.6 to 5.4 cubic miles of water or the equivalent of one Lake Mead per year – only about half as much as the rate at which the Aral Sea itself is losing water (5.8 cubic miles or 24 cubic kilometers).

“That means that roughly half the water lost from the Aral Sea has entirely left the watershed, by evaporation or agricultural uses, but half is upstream within the watershed,” said Becker. Decreasing rainfall in the region has been widely reported, and the researchers wanted to quantify its role in the water loss.Unexpectedly, they also found no change in precipitation since 2002.