The Aral Sea

This chapter presents key background information on the Aral Sea and its region. The Aral Sea Basin’s geographical setting is discussed, including location, climate, topography, soils, water resources, constituent nations, and basic demographic parameters. Next, the physical characteristics of the Aral Sea (size, depth, hydrochemistry, circulation patterns, temperature characteristics, water balance, etc.) prior to the modern desiccation that began in the 1960s are summarized. This is followed by treatment of level fluctuations of the Aral and their causes prior to the modern drying. The final section is devoted to tracing the most important events in the history of research and exploration of the Aral up to 1960.

Fauna of the Aral Sea has very poor species composition. Its poverty is connected to the geological history of the sea. Originally in the Aral Sea there were at least 180 species (without Protozoa) of free-living invertebrates. Their fauna had heterogeneous origins. Prior to the modern recession/salinization, species originating from freshwater, brackish-water and saline continental water bodies predominated. The remaining were representatives of Ponto-Caspian and marine Mediterranean-Atlantic faunas. Parasitic fauna had poor species composition: 201 species were indigenous and 21 were introduced together with fishes. It had a freshwater character. Ichthyofauna consisted of 20 aboriginal and 14 introduced species. The aboriginal fish fauna consisted of species whose reproduction typically occurs in fresh water. There was no fishery on the Aral Sea and local people caught a few of fish only from the rivers until in the mid 1870s Russians came here. After 1905, a newly built railway stimulated further development of commercial fishing, and the Aral Sea became an important fishing water body. The majority of fishes were commercial. Bream, carp and roach provided approximately two-thirds of commercial catch tonnage. In the twentieth century, there was an increase in species diversity. It was a result of intentional and accidental introductions of initially absent species. Though biodiversity grew by 14 species of fishes and 4 species of free-living invertebrates, only a few of them became commercially viable or valuable as food for fishes. A large number of vertebrate species inhabited the Aral Sea, its shore and islands, the Syr Darya and Amu Darya, and the deltas and lakes of these rivers in their lower reaches. The Aral Sea and its shores provided nesting sites for a large number of various floating and near shore birds. Tugay forests along the banks of the rivers constituted a type of oasis where many animal species lived. By the 1960s the flora of the Aral Sea included 24 species of higher plants, 6 species of charophytes and about 40 other species of macroalgae.

This chapter reviews the available data on the Aral Sea level changes and presents the current thinking on the sea’s recessions and transgressions prior to its modern desiccation. The geomorphologic, sedimentologic, paleoenvironmental, archaeologic and historiographic evidence is reconsidered and combined on the basis of calibrated ¹⁴C ages. The geomorphologic data appear contradictory and require re-examination. Lithology and paleoenvironmental proxies of the sediment cores provide much consolidated information, as they record lake level changes in sediment constitution by deep and shallow water facies and layers of gypsum and mirabilite, which are of special importance for determination of low levels. High levels are recorded in several on-shore outcrops. The new archaeological data from the now dry bottom of the Aral Sea and its surrounding zone in combination with the historiographic records provide a robust model for level changes during the last two millennia. Discovery of tree stumps in different parts of the bottom indicate low stands of the lake as well. During the last two millennia, there were two deep natural regressions of ca. 2.1–1.3 and 1.1–0.3 ka (1,000 years) BP (Before Present) followed by the modern anthropogenic one. The lake level dropped to ca. 29 m asl. Their separating transgressions were up to 52–54 m asl. The middle to early Holocene record of level changes is probably incomplete. Currently the middle Holocene regressions are documented for the periods of ca. 5.5–6.3, 4.5–5.0 and 3.3–4.3 ka BP. The early Holocene history of the Aral shows a long period of a shallow lake.

This chapter deals with two related water issues: the water resources of the Aral Sea Basin and the Aral Sea’s water balance. The Aral Sea’s size is dependent on the water resources in its basin and how much these are depleted by human usage. The chief water resources are the large basin rivers Amu Darya and Syr Darya and groundwater. The author discusses the size and character of these and their sufficiency for meeting human demand. Contrary to popular belief, the Aral Sea Basin is reasonably well endowed with water resources. But the high level of consumptive use, overwhelmingly for irrigated agriculture, has resulted in severe water shortage problems (see Chap 8). Since the Aral Sea is a terminal (closed basin) lake with no outflow lying amidst deserts, its water balance is basically composed of river inflow on the gain side and evaporation from its surface on the loss side. Precipitation on the sea’s surface contributes only about 10 % to the positive side of the balance. Net groundwater input is difficult to determine with any accuracy and likely had minimal influence until recent decades when, owing to major drops in river inflow, its impact on the water balance has grown. The Aral’s water balance was very stable from 1911 until 1960. However, since then it has been consistently negative (losses more than gains) owing to very substantial reductions in river inflow caused by large consumptive losses to irrigation. This was particularly pronounced for the decadal periods 1971–1980 and 1981–1990. More river flow reached the sea over the period 1991–2000 and its water balance, although remaining negative. However, the water balance situation deteriorated during the subsequent decade (2001–2010) owing to recurring droughts. The decidedly negative water balance has led to rapid and continuing shrinkage of the sea. (See also Chaps 9 and 11).

Regression of the Aral Sea began in 1961. At first changes in the fauna were primarily the result of fish and invertebrates introductions. In the 1970s regression accelerated. The main factor influencing fauna is increasing water salinity. In 1970s–1980s invertebrate fauna went through two crises. Freshwater species and brackish water species of freshwater origin became extinct first. Then Ponto-Caspian species disappeared. Marine species and euryhaline species of marine origin survived, as well as species of inland saline waters fauna. By the end of the 1990s the Large Aral became a complex of hyperhaline lakes. Its fauna was passing through the third crisis period. Incapable of active osmoregulation, hydrobionts of marine origin, and the majority of osmoregulators disappeared. A number of species of hyperhaline fauna were naturally introduced into the Large Aral. Salinization of the Aral Sea has resulted in depletion of parasitic fauna. All freshwater and brackish-water ectoparasites and significant part of helminthes began to disappear. Together with the disappearance of hosts, the parasites associated with them in their life cycle had to disappear. Regulation of the Syr Darya and Amu Darya and decreasing of their flow altered living conditions of the Aral Sea fishes, especially their reproduction. In 1971 there were the first signs of negative effects of salinity on adult fishes. By the middle of the 1970s natural reproduction of fishes was completely destroyed. Commercial fish catches decreased. By 1981 the fishery was lost. In 1979–1987 flounder-gloss was introduced and in 1991–2000 it was the only commercial fish. After the flow of the Syr Darya again reached the Small Aral, aboriginal fishes began migrating back to the sea from lacustrine systems and the river. This allowed the achievement of commercial numbers of food fishes. Since the end of the 1990s the Large Aral Sea is a lake without fishes. Regression and salinization of the Aral Sea caused destruction and disappearance of the majority of vegetational biocenoses.

The Aral Sea was once the world’s fourth largest inland body of water in terms of surface area. A lake basin, fed by two rivers, the Amu Darya and the Syr Darya, it supported a diverse ecosystem and an economically valuable fishery. Intensive agricultural activity related to cotton production with high water demands during the Soviet era caused excessive water diversion for irrigation purposes from the rivers. As a result, since the early 1970s, the shores of the sea have been steadily receding. The disappearance of the Aral Sea has caused several severe environmental and economic impacts. The fishery is no longer viable. The seabed became exposed leading to the airborne dispersal of salts and pesticide residues. The river delta flora and fauna have deteriorated such that fewer species exist. The decreasing level of the Aral Sea was accompanied by a rise of salinity, which resulted in the degradation of the ecosystems in the Aral Sea area as well as those of the fertile delta lands. The exposed seabed has turned into a desert, which at the present time is a source of tons of salty dust, blown away by the wind and carried along for thousands of kilometers. The quality of river water and other sources for drinking water have deteriorated. Environmental degradation in the Aral Sea area, especially in the south part in Karakalpakstan has resulted in decline of the socio-economic and public health situation.

Irrigation is highly developed in the Aral Sea basin. In 2010, irrigation networks covered 8.1 million ha here and accounted for 84 % of all water withdrawals. Irrigation as a highly consumptive user of water is the primary cause of the desiccation of the Aral Sea as it has severely diminished the inflow to the Aral from the Amu Darya and Syr Darya. Irrigation has a long history in the Aral Sea Basin dating back at least 3,000 years. During the Soviet era, irrigation was greatly expanded and water withdrawals for it increased considerably, primarily to grow more cotton. In the post-Soviet period, the area irrigated only increased slightly while water withdrawals for it declined somewhat. The latter has been primarily due to shrinkage of the area planted to high water use crops such as rice and cotton and not to the introduction of more efficient irrigation techniques on a substantial scale. Irrigation systems in the Aral Sea Basin since collapse of the USSR have badly deteriorated owing to lack of proper maintenance of them and insufficient investment in them. And the problems of soil salinization and water logging continue to worsen. There is certainly much that could be done to improve irrigation and use less water for it. This in turn could allow much more water to be supplied to the Aral Sea. But significant improvement of irrigation will require much greater effort and investment along with institutional reforms.

Central Asian major river basins link the countries of Afghanistan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan. Water management in Central Asia continues to be the most important transboundary environmental issue and the biggest problem remains how to allocate water for upstream hydropower production and downstream irrigation. Disagreements between the upstream and downstream states have increased regional tensions and slowed development plans. National responses to existing cooperative opportunities are essentially driven by a policy of national self-sufficiency in energy and water. While it is reasonable to be concerned about water and/or energy security, it is also critical to understand that a policy of self-sufficiency incurs substantial costs for all. As long as self-sufficiency dominates the policy agenda, the benefits of cooperation will not materialize. International water law could provide a rational avenue toward achieving international consensus on both use and allocation of water resources in the basin, with international legal agreements to reinforce the consensus. Incentives to cooperate through the application of the benefit-sharing concept as a development model in the basin would include decreased costs and increased gains in many dimensions of regional cooperation, including the benefits that stem from better agricultural practices and its competitiveness, joint developing of the region’s energy resources, and better management of regional environmental risks.

The Aral Sea region is a rapidly transforming landscape due to the continuous desiccation process. This study describes the vegetation and landscape dynamics in the lower Amu Darya Delta and adjacent parts of the dried sea bottom using MODIS (Moderate Resolution Imaging Spectroradiometer) surface reflectance data and EVI time series for the years 2001–2011. The potential of MODIS time series for monitoring landscape and vegetation dynamics of the dried sea bottom adjacent to the lower Amu Darya Delta was evaluated concerning data availability and spatial and temporal resolution. Two time series with different quality considerations were generated to subsequently characterize the yearly changes in the dried part of the sea bed, a simple layerstack (LS) of observations and quality-filtered and smoothed time series using a double logistic function (DL). The EVI (Enhanced Vegetation Index) values show a small dynamic inter- and intra-annual range. The majority of the EVI values fluctuate between −0.2 and +0.1, which indicates generally low vegetation dynamics in the desiccated areas. Looking at the inter-annual behavior of the LS/DL time series plots, the noise of the data and data fluctuations seem to become less for areas which have been dry for a longer period. A regional differentiation of the landscape dynamics between the Eastern and the Western basin of the southern Aral Sea could be observed. The observation points for the Western basin show a more stable behavior of the EVI values in comparison to the samples on the Eastern basin as seasonal or inter-annual flooding is less frequent. A typical pattern as a result of clear vegetation dynamics could not be observed in the EVI, LS and DL time series plots.

Space technologies have been widely used over the last 10 years for water surface monitoring worldwide and they have shown their capability to monitor components of the water cycle and water balance at regional scales and on time scales ranging from months to decades. We present here the applications of space data from radar altimetry and satellite imagery (Terra/MODIS) over the Aral Sea Basin (ASB). Radar altimetry, which has been designed to study the ocean, has opened a new era in monitoring lakes, rivers and reservoirs. The recent missions of satellite altimetry (Topex-Poseidon, Jason-1/2, Envisat, ERS-1 and ERS-2) have made it possible to measure with great precision inland sea level variations that can be used to determine water mass balances. Radar altimetry, coupled with complementary in situ data, has allowed quantifying precisely the water balance of the Aral Sea since 1992 as well as balances for large reservoir systems along the Syr Darya, in particular Chardarya and Toktogul, and for Lake Aydarkul. This approach has also made it possible to ascertain the water balances of lakes and wetlands in the deltas of the Syr Darya and Amu Darya.

Satellite imagery, from low to high resolution (1 km to a few meters) offers a useful tool to monitor surface water area for lakes and floodplains. MODIS data for example provide every 8 days, the surface water area from 2000 to 2012, with a spatial resolution of 500 m. It has been used to create a spatial time series for the Aral Sea and the lakes and wetlands in the deltas of the Amu Darya and Syr Darya where water area has been precisely measured. Along with in situ observations and hydrological modelling, space observations have the potential to improve significantly our understanding of hydrological processes at work in large river basins, (including lakes, reservoirs and floodplains) and their influence on climate variability and socio-economic life. Unprecedented information can be expected coupling models and surface observations with data from space, which offer global geographical coverage, good spatial-temporal sampling, continuous monitoring over time, and the capability of measuring water mass change occurring at or below the surface. Based on these different techniques we have determined the surface area of water features within the Aral Sea Basin, as well as volume variations, which are the key parameters to the understanding of the hydrological regime in ungauged basins. A focus on the Aral Sea and the water bodies in the deltas of the Syr Darya and the Amu Darya rivers over the last 20 years from satellite data is presented in this chapter, with some implications for the water balance. We will also describe the specific behaviour of the Western and Eastern basins of the Large (South) Aral Sea over the last 5–6 years

The desiccation of the Aral Sea since 1960 has been a notorious and well-documented example of anthropogenic ecological devastation. Equally ominous has been the devastating impact on the livelihoods and health conditions of the human populations inhabiting the Aral Sea region. As a socio-ecological crisis, the Aral Sea’s recession has demonstrated interrelationships between humans and the biophysical environment. An important societal dimension through which to access these relationships is the Aral basin’s regional economy. The Aral crisis itself has largely been a result of the large-scale Soviet-era water diversion projects whose impetus was primarily the production and export of cotton. The Aral Sea Basin today remains a globally important cotton production and export region. The most important economic activities devastated by the crisis have been fishing and fish processing. Once defunct enterprises, these activities have only recently been revived with the recent rehabilitation of the northern Aral Sea in Kazakhstan. This chapter examines the post-1960 developments of the cotton sector within the Aral basin and the fishing sector in the Aral Sea itself. Nature-economy linkages inherent in these sectors inform broader generalizations regarding human-environment interrelationships in the Aral Sea Basin today.

This chapter is a report about an international expedition to the northern part of the Aral Sea that took place from August 29 to September 16, 2011. The expedition was organized by the Zoological Institute of the Russian Academy of Sciences in St. Petersburg Russia and received logistical support from the Barsakelmes Nature Preserve (Zapovednik) headquartered in the Kazakhstan City of Aralsk and the Aralsk Branch of the Kazakhstan Fisheries Institute. The major focus of the expedition was to investigate the biological and hydrological improvements to the Small Aral Sea that had occurred as a result of raising its level by 2 m in 2005–2006 as well as what might be done to further improve the ecology and economic value of this water body in the future. The expedition also visited the channel that connects the Western and Eastern basins of the Large Aral Sea as well as the former Barsakelmes Island, now a desolate plateau on the dried bottom of the Aral Sea.

The Aral Sea in 2012 consisted of four residual water bodies with different hydrological regimes. The Kok-Aral dam raised and stabilized the level of the Small Aral Sea. Growth of salinity has stopped and a process of gradual salinity reduction is in progress. By the autumn 2011 water salinity in the open part of the Small Sea dropped to 8 g/l. The future of its biota depends on future salinity. If the current regime will remain, then the decrease in salinity will continue and the Small Aral will turn from a brackish to a nearly freshwater body. This freshening will cause substantial changes in the fauna as a result of the disappearance of marine and brackish species and reintroduction of freshwater forms. Currently two variants of further rehabilitation of the Small Aral are under consideration. The first one involves an additional dam at the entrance to Saryshaganak Gulf to create a reservoir out of it and the filling of this water body via a canal from the Syr Darya. The Small Sea under this plan would then have both freshwater and brackish water parts. The second variant is to increase the level and area of the Small Aral Sea by raising the height of the Kok-Aral dam. In this case, all the Small Sea remains brackish except the existing freshened zone in front of the Syr Darya Delta. Both these variants would avoid further strong freshening of the Small Aral Sea and associated with this adverse changes in the fauna. The expected future of the biota of the residual hyperhaline water bodies of the Large Aral is quite different. In this case, there is no possibility of reducing their salinity leading to recovery of fauna represented by marine and widely euryhaline species. On the contrary, even stronger salinization is likely. The East Large Aral Sea could dry out completely, and the West Big Aral could turn into a lifeless water body akin to the Dead Sea.

The Aral Sea between 1960 and 2012 lost 85 % of its area and 92 % of its volume, while separating into four residual lakes. The Large Aral on the south endured a level drop of 25 m and rise of salinity from 10 g/l to well over 100 g/l. Over this period, the sea suffered immense ecological and economic damage including the destruction of its valuable fishery and degradation of the deltas of its two influent rivers. Nevertheless, in spite of this calamity, and contrary to reports that the sea is a lost cause (popular reports that the sea will “disappear” are simply false), hope has remained that the sea and its deltas could be partially rehabilitated. Various restoration scenarios are discussed. Full revitalization of the sea in the foreseeable future is extremely improbable, but cannot be ruled out for distant times. The project implemented in the first decade of the present century to partially restore the Small (northern) Aral Sea so far has been eminently successful. Partial restoration of the Large (southern) Aral is more problematic as it would be more costly and complicated than the north Aral project. Nevertheless, it is certainly worthy of further investigation. Projects to improve the deltas of the Amu Darya and Syr Darya are also underway. The interested reader should also see Chap.​ 14 which analyses the potential for biological rehabilitation of the Aral and Chap.​ 16 focusing on the grandiose Siberian water transfer schemes developed during the Soviet era to radically improve the water balance of the Aral Sea Basin.

The twentieth century was the era of mega-engineering thinking. This was a worldwide phenomenon, but perhaps had its clearest expression in the Soviet Union, a nation with a well-developed ideology promoting man subduing nature for purported human betterment. Soviet plans to transfer huge amounts of water long distances from Siberian rivers to Central Asia were initially conceived, during the Stalinist era, as a way to fundamentally transform the physical environment of this region. During the period 1960 to the mid 1980s, these projects were primarily seen as the best means to provide more water for irrigation expansion and, secondarily, as a way to provide more water to the Aral Sea. After several decades of intense scientific study and engineering development, a final design for Siberian water transfers was on the verge of implementation when an abrupt change of national policy in 1985–1986 put it in on hold for the foreseeable future. The plan foundered owing to Russian nationalist opposition, enormous costs, a changing political environment, and the threat of significant environmental damage. The collapse of the USSR has probably doomed the project although it continues to be promoted by Central Asian governments and even some prominent Russians as a means to bring back the Aral Sea.

Climatic and environmental changes in the Aral Sea Basin represent a complex combination of global, regional, and local processes of variable spatial and temporal scales. They are driven by multiple interconnected factors, such as changes in atmospheric circulation associated with global warming, regional hydrological changes caused by mountain-glacial melting and massive irrigation, land-use changes, as well as hydrological, biogeochemical, and meso- and microclimatic changes in the Aral Sea and its quickly expanding exposed dry bottom. Human vulnerability to climate change involves many dimensions, such as exposure, sensitivity, and adaptive capacity and affects various aspects of human-environmental interactions, such as water availability and stress, agricultural productivity and food security, water resources, human health and well-being and many others at various spatial and temporal scales.

The first part of this final chapter summarizes the introductory chapter plus the chapters contained in Parts I, II, and III, exclusive of Chap.​ 18, to remind the reader of the key aspects of each. The second part lays out what in the author’s view are the key lessons to be learned from Aral Sea and its modern desiccation. The final part lists and briefly discusses what needs to be done in terms of research and monitoring of the Aral Sea.