Aral Sea, salt lake, c.12,000 sq mi (31,080 sq km), in south-western Kazakhstan and north-western Uzbekistan. Generally very shallow, it attains a maximum depth of c.180 ft (58 m).
Geologically separate from the Caspian Sea since the last Ice Age, the Aral Sea was once only slightly saline. Its western and northern shores are the edges of the arid Ustyurt Plateau; the Kyzyl Kum desert stretches to the south-east.
Mentioned in Arab writings of the 10th century, the Aral Sea was called the Khwarazm (or Khorezm) Sea by later Arab geographers. In the 18th century it was reached by Russians, who called it the Blue Sea.
Fed by the Syr Darya and Amu Darya rivers, the sea supported local fishing and was navigable from Muinak to Aralsk.
In the 1950s the Soviet Union decided to cultivate cotton in the region, and since the early 1960s the Syr Darya and Amu Darya have been used for large-scale irrigation, reducing the flow of freshwater into the sea. Evaporation and water diversion have resulted in a major environmental problem, shrinking the Aral by half.
The quality of its remaining water has deteriorated, increased salinity has killed fish, and the health of those living along the shore has suffered. Regional weather has been affected as well, becoming harsher as the sea's moderating climatic influence has diminished.