The Aral Sea was once the world's fourth largest lakes in the world and now much of it is a vast desert. Aral was fed by two rivers, the Amu Darya and Syr Darya, which brought snowmelt from mountains to the southeast, and local rainfall.
In the 1960's, the Soviet Union diverted water from the two rivers into canals to supply agriculture in the region.
With the loss of water, the lake began to recede. Fertilizers and chemical runoff contaminated the lake bed. As the lakebed became exposed, winds blew the contaminated soil onto the surrounding croplands, meaning even more water was needed to make the land suitable for agriculture.