Uploaded by Gulzira Kdirbaeva

Changes of the Aral Sea ecosystem

PhD., Docent Guzlira Kdirbaeva
Aral Sea, Kazakh Aral
Tengizi, Uzbek Orol
Dengizi, a oncelarge saltwater
lake of Central Asia. It
straddles the boundary
between Kazakhstan to
the north
and Uzbekistan to the
The shallow Aral Sea was once the world’s fourth
largest body of inland water. The remnants of it
nestle in the climatically inhospitable heart of
Central Asia, to the east of the Caspian Sea. The Aral
Sea and its demise are of great interest and
increasing concern to scientists because of the
remarkable shrinkage of its area and volume that
began in the second half of the 20th century—when
the region was part of the Soviet Union—and
continued into the 21st. That change resulted
primarily because of the diversion (for purposes of
irrigation) of the riverine waters of the Syr
Darya (ancient Jaxartes River) in the north and
the Amu Darya (ancient Oxus River) in the south,
which discharged into the Aral Sea and were its main
sources of inflowing water.
The Aral Sea depression was formed toward the end
of the Neogene Period (which lasted from about 23 to
2.6 million years ago). Sometime during that process
the hollow was partially filled with water—a portion
of which came from the Syr Darya. In the early and
middle parts of the Pleistocene Epoch (about
2,600,000 to 11,700 years ago), the region appears to
have dried up, only to be inundated again sometime
between the end of the Pleistocene and the
early Holocene Epoch (i.e., after about 11,700 years
ago)—the latter instance being the first time by the
Amu Darya, which had temporarily changed its
course from the Caspian to the Aral Sea. After that,
except for some relatively brief dry spells between the
3rd and 1st centuries BCE, the two rivers’ combined
flows generally maintained a high water level in the
sea until the 1960s.
The Aral Sea area is characterized by a desertcontinental climate that features wide-ranging
diurnal air temperatures, cold winters, hot
summers, and sparse rainfall. The rate of
precipitation—an annual average of 4 inches (100
mm) in all, occurring mainly in the spring and
autumn—is only a tiny fraction of the lake’s
traditional rate of evaporation. Northwesterly
winds prevail in autumn and winter, and
westerly and southwesterly winds are common in
spring and summer.
In 1960 the surface of the Aral Sea lay 175 feet (53 metres)
above sea level and covered an area of some 26,300 square
miles (68,000 square km). The Aral Sea’s greatest extent
from north to south was almost 270 miles (435 km), while
from east to west it was just over 180 miles (290 km).
Although the average depth was a relatively shallow 53
feet (16 metres) or so, it descended to a maximum of 226
feet (69 metres) off the western shore. The sea’s northern
shore—high in some places, low in others—was indented by
several large bays. The low-lying and irregular eastern
shores were interrupted in the north by the huge delta of
the Syr Darya and were bordered in the south by a wide
tract of shallow water. The equally vast Amu Darya delta
lay on the lake’s southern shore, and along the lake’s
western periphery extended the almost unbroken eastern
edge of the 820-foot- (250-metre-) high Ustyurt Plateau.
The rapid shrinkage of the Aral Sea led to numerous
environmental problems in the region. By the late 1980s
the lake had lost more than half the volume of its pre-1960
water. The salt and mineral content of the lake rose
drastically because of that, making the water unfit for
drinking purposes and killing off the once-abundant supplies
of sturgeon, carp, barbel, roach, and other fishes in the lake.
The fishing industry along the Aral Sea was thus virtually
destroyed. The ports of Aral in the northeast and Mŭynoq in
the south were now far from the lake’s shore. A partial
depopulation of the areas along the lake’s former shoreline
ensued. The contraction of the Aral Sea also made the local
climate noticeably harsher, with more-extreme winter and
summer temperatures.