Since the 1960's, the salinity of the Aral Sea has increased. This was caused
by evaporation of sea water by the sun. Remember, the Aral is a closed
system with no outlet. All water loss from the sea itself is from evaporation.
During evaporation, only the water is removed, the salt stays behind,
increasing the salinity of the remaining water. The salinity
of the sea was also increased due to agricultural practices.
Leached cations (salts) from irrigated lands enter the Aral Sea.
This is an environmental consequence of bringing desert soils into agricultural production.
In some areas surface salt sheets now rim the shore for over 100 km.
The wind picks up the salt and deposits it elsewhere, including
the agricultural regions. Approximately 47 million tons of dried salt are
deposited onto the surrounding agricultural regions each year.
Some of this salt helps forms huge dunes that can be seen
on the southeastern side of the Aral Sea in this image.
Other deposits of salt are found as salt pans, which are also visible in the western portion of
the following
image (NM21-740-87 taken in 1996 from the Russian Space Station, MIR.) Also notice
the sheets of salt rimming the shores of the sea.