978-0-00-812422-9 COLLINS CAMBRIDGE AS AND A LEVEL GEOGRAPHY

Case Study
figure 1.35 Aral Sea catchment area
The Aral Sea
The Aral Sea is one example of how irrigation can have significant consequences
on an area. Formerly the fourth-largest lake in the world, spanning 68 000 sq
km, the Aral Sea has been steadily shrinking since its waters were first redirected
by Soviet irrigation projects in the 1960s. The loss of water from the Aral Sea to
a catchment some 500 km away has meant there has been a reduction in the
amount of evaporation and evapotranspiration in the basin, contributing to a
lack of cloud cover and resultant rain. The frequency and intensity of rainfall is
thought to have declined over the past 30 years.
The drying up of the Aral Sea is often considered to be one of the greatest
management disasters in history. Between 1954 and 1960 the government of
the former Soviet Union ordered the construction of a 500 km-long canal that
would take a third of the water from the Amudar’ya River to an immense area
of irrigated land in order to grow cotton in the region. Some 5 per cent of the
nearby reservoirs and wetlands have become deserts and more than 50 lakes
from deltas, with a surface area of 60 000 hectares, have dried up. Although
irrigation made the desert bloom, it devastated the Aral Sea.
2001 2015
figure 1.36 The shrinking waters of the Aral Sea.
The blowing dust from the exposed lakebed, contaminated with agricultural
chemicals, became a public health hazard. The salty dust blew off the lakebed and
settled onto fields, degrading the soil. Croplands had to be flushed with larger
and larger volumes of river water. The loss of the moderating influence of such
a large body of water made winters colder and summers hotter and drier. As the
lake dried up, fisheries and the communities that depended on them collapsed.
The increasingly salty water became polluted with fertilisers and pesticides.
In 2005 the World Bank and the government of Kazakhstan constructed a
13 km dam at a cost of US$85 million. By 2008 fish stocks had returned to their
1960 levels. In 2008 the North Aral was subject to a US$250 million project to
rejuvenate the area, though progress is slow.
figure 1.37 Boats in what is now desert around the Aral
Sea, Uzbekistan.
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Hydrology and fluvial geomorphology