Aral Sea desiccation

Water availability has fluctuated in the Aral Sea as a result of natural and anthropogenic forces. Anthropogenic effects in the second half of the twentieth century brought about an environmental disaster, as the sea shrank drastically, with deadly effects on agriculture, vegetation, and human and animal populations in the region.

Background

The dramatic drying of Central Asia’s Aral Sea is sometimes called one of the greatest ecological disasters of the twentieth century. Over the past ten thousand years, the area and volume of this internal lake have greatly fluctuated as a result of both natural and anthropogenic forces. Anthropogenic forces in particular greatly reduced the sea at the end of the twentieth century, from 67,500 square kilometers in 1960 to 17,382 square kilometers in 2006.

The Aral Sea is located in an area of cold temperatures and deserts: the Karakumy is to the south, the Kyzylkum Desert is to the southeast. The sea’s 1.8-million-square-kilometer drainage basin encompasses six central Asian countries: Iran, Turkmenistan, Kazakhstan, Afghanistan, Tajikistan, and Uzbekistan (including the Karakalpak Autonomous Republic). Kazakhstan and Uzbekistan are physically adjacent to the Aral Sea. Although nine streams flow within the drainage basin, the Syr Dar’ya and the Amu Dar’ya are the major rivers. Dar’ya translates from the Turkic languages of central Asia as “river.”

In 1918, the Soviet Union decided to develop the area around the Aral Sea to grow cotton. The decision was economic: Cotton, “white gold,” provided revenue for the government. Herbicides, pesticides, and fertilizers were heavily used to bolster crop production, and the Amu and Syr Dar’ya were diverted for irrigation.

The Soviet irrigation programs were inefficient, with open waterways and irrigation basins subject to evaporation. Open-air channels were dug through sandy deserts with the thirteen-hundred-kilometer Karakam Canal diverting between 20 and 30 percent of the Amu Dar’ya’s flow west to Turkmenistan.

Between 1987 and 1989, the Aral Sea divided into the small Aral Sea in the north, fed by the Syr Dar’ya, and the large Aral Sea in the south, supplied by the Amu Dar’ya. Using the years 1960 to January, 2006, as a baseline, the water level of the little Aral fell by 13 meters, the large Aral by 23 meters.

UNESCO added documents charting the decline of the sea between 1965 and 1990 to its Memory of the World Register, intended to protect important historical documents from being lost through neglect or deliberate destruction, in 2011. The organization felt it was important that people be able to study how the dessication, which UNESCO's website describes as an "ecological tragedy," came to be.

Further drying during this time caused the once-larger southern Aral Sea to split into two lakes, known as the eastern and western basins. In 2014, due to a combination of the factors already causing dessication and a year of unusually dry weather, the eastern basin of the Aral Sea dried up completely for the first time in 600 years. As of 2018, the eastern basin remains dry, and has become known as the Aralkum Desert.

Displaced Fishing Industry

Historically, the Aral Sea fishing industry employed several thousand workers and provided, according to commercial fishing reports, one-sixth of the Soviet fish supply. The lowered lake level reduced the industry and increased the distance between the lake and fishing ports. Decreased water flow to the river deltas and wetlands diminished fish spawning and feeding, so that of the thirty-two fish species formerly existing in the lake, only six survived. Those remaining survived by inhabiting small water areas of river deltas—areas that play a large role in regenerating lake fish supplies. Commercial fisheries did not exist after the mid-1980s.

When lake water is reduced by evaporation and freshwater input is negligible, salts within the water are concentrated and approach the salinity of a typical ocean, 35 grams of salt per liter. Since the Aral Sea was becoming more saline in the 1970s, a saltwater fish, the Black Sea flounder (Platichthys flesus lulscus) was introduced into the sea. The intent was to enable the lake’s fishing industry to survive, but by 2003 the flounder no longer existed in the Aral Sea, whose salinity had reached greater than 70 grams per liter.

Hazardous Lakebed Deposits

As the Aral Sea shrinks, calcium sulfate, calcium carbonate, sodium chloride, sodium sulfate, and magnesium chloride are deposited on the exposed seafloor. In addition to these salts, pesticide residues of organochlorines, dicholorodiphenyl-tricholoethanes(DDT), hexachloro-cyclohexane compounds (HCH, Lindane), and toxaphene remain. Other toxic materials present are the result of biological weapons testing and failed industrial sites.

The region immediately surrounding the Aral Sea—Uzbekistan, Kazakhstan, and parts of Turkmenistan—are affected by hazardous dust and salt storms. Most major storms occur in a one-hundred-kilometer margin along the north-northeastern coastal zone. Some 60 percent of these storms trend southwesterly, for 500 kilometers, depositing salts, agrochemical dusts, and aerosols on the delta of the Amu Dar’ya. This southern river delta region is densely populated, so toxic storms affect human and animal health and economic stability. Another 25 percent of the storms trend west, moving over and beyond the Ust-Urt plateau, an area of livestock pastures.

Toxic dust storms harm the human food supply and physical health of domestic and wild animals. The human risk associated with airborne salt and dust is high, and greater than average incidences of respiratory illnesses, eye problems, throat and esophageal cancer, skin lesions and rashes, and liver and kidney damage are reported in the Aral Sea region.

Aral Sea Geology

The Aral Basin has experienced geologic cycles of diversion and desiccation. During the Pliocene epoch, the ocean withdrew from Eastern Europe and Turkestan, leaving remnant basins such as the Aral, Caspian, and Black seas. Late Pliocene continental crust movements created a more permanent depression in the area of the Aral Sea, which was filled with water, some of which came from the ancestral Syr Dar’ya.

The effects of the Pleistocene epoch are recorded by terrestrial sedimentary deposits. Eolian processes operated in the Aral depression during the early and middle Pleistocene. During the late Pleistocene, fluvial processes filled the depression by inflows from the ancestral Amu Dar’ya; then, the basin was filled for a second time with waters from the Syr Dar’ya.

Both rivers affect lake level changes, but when the 2,525-kilometer course of the Amu Dar’ya migrates away from the basin, lake level drops. Diversions of the Amu Dar’ya are natural, resulting from filling fluvial channels during heavy rains or floods. Some river diversions are the result of human actions, such as improper or failing irrigation systems or intentional destruction of river dams and levees during political upheaval or war.

Aral Sea Restoration

The Aral Sea cannot be reestablished to its pre-1960 status, because to do so would mean curtailing irrigation, which uses 92 percent of all Aral water withdrawals. Curtailment of irrigation would mean crop failure and economic and social collapse in the Aral Basin. After the fall of the Soviet Union in 1991, Kyrgyzstan, Uzbekistan, Turkmenistan, Kazakhstan, and Tajikistan joined together to address the Aral Sea crisis. Two major agencies were formed by these new regional states. with the International Fund for the Aral Sea (IFAS) taking the lead role in 1997. Also, the United Nations, the European Union, and many other international aid agencies operated to improve the region.

In order to regulate flow in the little Aral, Kazakhstan and the World Bank constructed an eighty-five-million-dollar, thirteen-kilometer earthen ditch connected to a concrete dam with gates and spillways. Completed in November, 2005, this system brought early success: The water level increased to 42 meters from 40 meters, and, by summer of 2006, the lake area increased by 18 percent. Salinity decreased by one-half to almost 10 grams per liter in 2006, but future levels will vary, by area, from 3 to 14 grams per liter. Decreased salinity increases fish population, aiding the fishing industry and the Kazakhstan economy. A former fish-processing plant has reopened in Aralsk, Kazakhstan, to process lake carp, Aral bream, Aral roach, Pike perch, and flounder—the top five species caught in autumn, 2007.

The fish population of the north Aral has continued to grow; the total weight of fish caught in a year increased from 1,360 tons in 2006 to 7,106 in 2016. While far short of the peak amount of 48,000 tons of fish in 1957, the improvement is significant, and has been an economic boon to the surrounding area. However, the return of the fish population has also led to an increase in illegal fishing, which experts are concerned will interfere with the careful management needed for the population to continue to rebound.

In 2024, the USAID Oasis project created a 500-hectare demonstration site for a new environmental restoration plan. This plan involves planting large numbers of black saxaul shrubs to reduce dust storms in the region. Despite these recovery efforts, the Aral Sea remained at just 10 percent of its original water surface area. Much of the remainder of the Aral Sea had been renamed the Aralkum Desert.

Context

The Aral Sea Basin has become synonymous with irreversible environmental disaster. The entire region demonstrates the potential for humans to act as geomorphic change agents. The area’s inhabitants diverted rivers for irrigation; replaced desert vegetation with such crops as melons, cotton, and rice; and altered natural water chemistry to salinities greater than that of ocean water. Anthropogenic environmental degradation has also affected human health in the Aral Basin.

Populations around the sea are in a state of upheaval, dislocation, and poverty as a result of the collapse of the fishing industry and a lack of government support from the former Soviet Union since the early 1990s. Essential medications and adequate hospital facilities are not available when economic conditions are stagnant. Health problems begin in the youngest populations: High infant mortality, low birth weight, growth retardation, and delayed puberty are present in the basin.

Poor quality and insufficient quantities of drinking water in the basin have increased typhoid, hepatitis A, and diarrhea in all age groups. High levels of mineralized water within the basin may contribute to kidney and liver diseases. Also increasing are acute respiratory diseases—killing almost one-half of all children. Dust storms sourced from former seabeds deliver salt and toxic chemical sediments to humans and areas of human habitation.

Possibly the greatest health risk is from pesticides, which contaminate the water and food supplies and infiltrate during dust storms. Pesticides may be applied to crops, especially cotton, several times during a growing season. Lindane (HCH) has also been used biannually to rid sheep’s skin and fleece of vermin.

It is difficult to determine the relative importance of each human health issue, especially when population groups may suffer multiple medical problems and live in impoverished conditions. What is clear is that residents of the Aral Sea are experiencing a pronounced health crisis, not unlike the environmental one that surrounds them.

Key Concepts

• anthropogenic: caused or produced by humans
• hazardous: poisonous, corrosive, flammable, explosive, radioactive, or otherwise dangerous to human health
• herbicides: substances or preparations for killing plants, such as weeds
• pesticides: chemical preparations that kill pests, including unwanted animals, fungi, and plants
• Pleistocene epoch: first half of Quaternary period, beginning about two million years ago and ending about ten thousand years ago
• Pliocene epoch: Tertiary period, beginning about ten million years ago and ending about two million years ago, known for its cool climate, mountain building, and increased mammal populations

Bibliography

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