We see a lot of change with the 40+ years of Landsat imagery, along with the historical aerial imagery in the archives at EROS. The drying of the Aral Sea is likely the most dramatic change occurring over the past several decades in this imagery.
The Aral Sea once covered about 68,000 square kilometers, a little bigger than the U.S. state of West Virginia. It was the 4th largest lake in the world. It is now only about 10% of the size it was in 1960. Coastlines receded several kilometers from what were once coastal communities.
The Aral Sea is a terminal lake. Large permanent snow fields and glaciers in mountain ranges feed the two major rivers that flow into it, but it has no outlet. Syr Darya flows into the northern part of the Aral Sea. Amu Darya flows into the southern part. (Darya means river in the Turkic languages of central Asia.)
The precipitation rate over the Aral Sea is very low, less than 200 millimeters per year. However, 1,000–1,200 millimeters of water evaporates from the sea each year. Therefore, stability of the water level greatly depends on inflow from these two rivers, which has diminished over the past few decades leading to the shrinking of the lake.
The sea has in fact split into two separate bodies of water, referred to as the North Aral Sea and the South Aral Sea. The North Aral has stabilized but the South Aral has continued to shrink and become saltier. Up until the 1960s, Aral Sea salinity was around 10 grams per liter, less than one-third the salinity of the ocean. The salinity level now exceeds 100 grams per liter in the South Aral, which is about three times saltier than the ocean.
The effects of this dramatic change are far-reaching, geographically, environmentally, and economically. The subsequent sections describe how a body of water this size could nearly disappear so quickly.
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