A Shrinking Lake

Straddling the border between Kasachstan and Uzbekistan is a lake that was not long ago the fourth largest in the world. That the once mighty Aral Sea currently has the far less impressive ranking of eighth largest is due to intensified irrigation of nearby cotton and rice crops which now claims virtually all the water from the two main feeder rivers. The results have been serious and widespread ecological and economic disruption. (More details about this fascinating story are available here).

This image shows the Aral Sea and the Amu-Dar'ja delta (that's the red patch to the south indicating agricultural activity) as it looked in 1996 when viewed from the vantage point of space (by the MSU-SK instrument on RESURS-01, a Russian earth observation satellite).

A series of images like this one collected between 1960 and the present reveal the dramatic retreat of the shoreline and the growth of the islands visible in the lake as the sea level declines. For example, the small lake in the north separated off from the Aral Sea in 1987; the elongated E-W oriented island in the upper third of the remaining lake became a peninsula in 1996 when its eastern edge joined the shore. Within about 4-5 years the small gap remaining to the south of the long N-S oriented island in the western part of the lake is expected to close. Eventually the small gaps left at the western and northern ends of these two islands will close, completing the process of separation of the deep western basin from the shallow eastern portion of the Aral Sea.

Satellite remote sensing provides the technology to reliably monitor and document this shrinkage process, and the data required by local decision makers who are striving to establish sound water management and agricultural policies.

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