Contents - Previous - Next
This is the old United Nations University website. Visit the new site at http://unu.edu
3. The Aral Sea basin
Human driving forces
Social and economic changes
Societal recognition of the Aral Sea problem
Possible solutions and rescue scenarios
The Aral Sea basin trajectory
Saving the Aral Sea
Nikita F. Glazovsky
The ecological situation in the Aral Sea basin is one of the most complex in Central Asia. The situation is aggravated by the fact that environmental degradation is accompanied by a deterioration in economic and social conditions. Many of the problems of the Aral basin, however, are typical of many other arid and semi-arid regions of the world.
An analysis of the Aral Sea ecological crisis shows that any reliable estimate must address the whole Aral Sea basin, and the sea itself should also be the subject of surveys. The Aral Sea basin includes the basins of the Syr Darya and Amu Darya rivers, which flow into the sea, and also the Tedzhen and Murgabi rivers, the Karakum canal, and shallow rivers flowing from Kopet Dag and western Tien-Shan, as well as the areas with no runoff among these rivers and around the Aral Sea (fig. 3.1). Administratively, the region covers all of Uzbekistan and Tadzhikistan, portions of Kazakhstan (the Kzyl Orda and Chemkent areas and the southern part of the Aktyubinsk area), Kirghizstan (the Osh and Narym areas), and Turkmenistan (without the Krasnovodsk area), and also part of north Afghanistan and north-eastern Iran. The area of the whole basin amounts to about 2 million km². Special attention in this chapter is paid to the so-called Priaralye (the Aral area), a territory that lies in immediate proximity to the Aral Sea shores and includes the Amu Darya and Syr Darya deltas.
Landscapes of arid and semi-arid regions are known to be very sensitive to global climatic changes and to tectonic events and other physical processes. The Aral region is one of the centres of origin of civilizations and farming, and primitive forms of artificial irrigation have existed here for more than 2,000 years.
Natural variations and human activity led to significant ecological changes in the Aral basin during historical time. The sea itself often rose and fell considerably. During the Quaternary period, variations in the level of the Aral Sea evidently reached 36 metres. But in spite of such important earlier variations in the level of the sea, fluctuations during the first half of the twentieth century did not exceed 1 metre, and the ecological situation was quite stable up to the end of the 1950s. Substantial variations have taken place during the last 30 years, however, and this chapter focuses on this time-period.
Fig. 3.1 The Aral Sea basin
Important changes have occurred in practically all of the components of the environment in the Aral basin over the past 30 years. The following discussion treats the most important of these.
The mean perennial runoff from source areas in the mountainous regions of Central Asia and Kazakhstan during 1911-1960 amounted to 116 km³ per year. Of this, 60 km³ was diverted for irrigation and lost in the deserts, whereas 6 km³ reached the Aral Sea, thus keeping its level relatively stable.
Beginning with the 1960s, the runoff to the Aral, in spite of some peaks in wet years, began to fall and decreased to approximately 4 km³/year. In some years the runoff to the Aral did not exceed 1-2 km³ (fig. 3.2 below). Available data suggest that only 10-15 per cent of the runoff decline was associated with climatic variations and that the main factor was the development of irrigation.
By our calculations, the total length of the drainage network in the arid zone of the former USSR stretches to 150,000-200,000 km, which is 10-15 times longer than the main rivers in this region. As a result of the discharge of drainage waters to the desert, vast new water basins without outflow have been formed, of which the Sarykamysh and Arnasai lakes are the largest.
The Sarykamysh lake in the south-eastern portion of the Usturt plateaux was formed as a result of discharging the drainage runoff from the left-bank irrigated massifs to the lower reaches of the Amu Darya river. These discharges started early in the 1960s. Currently, the lake covers an area of about 3,000 km² and has a volume of 26 km³. Mineralization of the lake waters is continuously increasing: from 3-4 grams/litre (g/l) in the early 1960s to 12-13 g/l in 1987 (Shaporenko 1987). Annual increases in mineralization amount to 0.5-0.6 g/l.
The Arnasai lake (and, more precisely, the Arnasai lacustrine system) was formed on the site of the Aidar solonchak northward of the Nuratau ridge as a result of the diversion of discharge waters from irrigated massifs on the left bank of the middle reaches of the Syr Darya river. The area of this water basin has varied from 2,330 km² to 1,750 km², the water volume from 20 km³ to 12.5 km³, and mineralization in different parts of the lacustrine system from 4 g/l to 13 g/l (Nikitin and Lesnik 1982). As a result of a discharge of drainage waters into Karakum, swamps emerged that cover an area of over 200,000 (and perhaps 250,000) ha (Rozanov 1986).
Reduction in runoff has led to changes in the number and area of lakes in the Amu Darya and Syr Darya deltas. The area of natural lakes has continuously shrunk while the number of lakes during the first period of water-basin drying increased owing to the fragmentation of large lakes (table 3.1).
Table 3.1 Changes in the number and area of natural lakes in the Amu Darya and Syr Darya deltas, 1936-1980
|Region||Period||No. of lakes||Area of lakes (km²)|
|Amu Darya delta||1936||346||2,330|
|(excluding Sudochye lake)|
|Syr Darya delta||1936||558||1,490|
Sources: Nikitin (1977) and Chebanov (1989).
Variations in the Aral Sea
Prior to the 1960s, the Aral Sea area amounted to 68,300 km², comprising a water surface area of 66,100 km² and islands of 2,200 km². The volume of the sea water amounted to 1,066 km³ (Nikolayeva 1969). The maximum sea depth was 69 m, but depths of less than 30 m were common over much of the sea. The sea level, meanwhile, fluctuated in the 52-53 m range.
Mineralization of the Aral waters during the past 100 years of instrumental observations has varied within a range of 10-12 g/l, and constant salinity has been sustained owing to two main processes sedimentation of poorly soluble components owing to water evaporation and salt accumulation in narrow bays often connected only periodically with the Aral Sea (especially in the south-eastern part of the sea) and in depressions without outflow near the seashore.
Table 3.2 Water budgets of the Aral Sea prior to the 1960e (km³/year)
|Groundwater runoff||0.7-0.3||Filtration to the banks and diversion to the lagoons||1-2|
River runoff and evaporation were key factors in the water budget (table 3.2). Two rivers - the Amu Darya and Syr Darya - maintain river runoff. Some 20 fish species (including commercial ones), 266 species of invertebrates, and 94 species of superior and inferior plants existed in the sea.
With decreased river inflow beginning about the early 1960s, the water budget of the sea changed. The sea area decreased to 34,800 km² and the volume to 304 km³ by 1990. Over the same period, the level of the sea fell to 37.8 m, a drop of more than 15 m from the preceding period (fig. 3.2). A significant part (about 33,000 km²) of the sea floor dried up, the configuration of the shoreline changed, and water mineralization increased to 33 g/l. As water mineralization increased, the spawning sites of fish disappeared and a deterioration in the forage reserve led to a decline in fish, with only five species remaining. Nearly all limnoplankton and numerous haloplankton became extinct (Aladin and Khlebovich 1989; Williams and Aladin 1991).
Owing to the recession of the sea, the climate in the Aral area has changed (Molosnova, Subbotina, and Chanysheva 1987). Summer and winter air temperatures at stations near the shore increased by 1.52.5°C, whereas diurnal temperatures increased by 0.5-3.3°C. At coastal stations the mean annual relative air humidity decreased by 23 per cent, reaching 9 per cent in spring and summer. Recurrence of drought days increased by 300 per cent. Spring now comes 7 days later and autumn 12-13 days later (the date on which the mean diurnal temperature passes the zero value) than previously. The last spring frosts shifted to later dates and the first autumn ones occurred some 1012 days earlier. The annual cycle of precipitation also changed. In 1959 the maximum precipitation fell during February-March and the minimum during September, whereas in 1970-1979 the maximum was observed in April and the minimum in July. A three-fold increase in reflected solar radiation in the Aral area due to a sevenfold rise in the albedo of the area previously occupied by the Aral Sea has contributed to an increase in the continentality of the climate (Kondratyev, Grigoryev, and Zhvalev 1986).
Fig. 3.2 Changes in river water inflow to the Aral Sea, 1960-1990 (Key: R = change in river water inflow [km³ per year]; S = sea area ['000 km²]; L = sea level [m]; V = sea volume [km³]; M = mineralization of sea waters [g/l])
In the arid conditions of the Aral Sea basin, the depth of ground-water is a key issue. Above a certain critical level, intensive water evaporation begins, water transformation intensifies, and soil salinization occurs.
Groundwater levels rose in many regions as a result of irrigation development. Thus, in the Tashauz area, land with a groundwater level above 2 m amounted to 20 per cent in 1959-1964, whereas in 19781982 it comprised 31.5 per cent. Over the whole of Turkmenia, 87 per cent of the irrigated land has groundwater levels that have risen by at least 2.5 m; over 26 per cent of the area, levels are now higher by 1.5 m. In Uzbekistan, groundwater levels are above the critical value on 1.6 million ha.
In the delta regions of the central Asian rivers, variable changes in the depth of the groundwater level have occurred. Thus, according to F. I. Khakimov (1989), drops in the water level in the rivers and sea have produced a lowering of groundwater levels of up to 50 cm per year on non-irrigated territories subjected to desertification. In some regions, beginning in the early 1960s, groundwater levels have fallen by 10-15 m. On irrigated land, by contrast, the levels have risen by up to 50 cm per year. In many regions, in fact, the level has risen by fully several metres. In the Karakalpak Republic, for example, the area of land with a critical groundwater situation increased from 72 per cent to 90 per cent during 1975-1989.
Salinization and desertification
Rises in the groundwater level and water evaporation cause intensive soil salinization. Thus, in the newly irrigated areas of the Murghab oasis of Turkmenistan, the area of slightly salinized and unsalinized land decreased from 50 per cent to 25 per cent over eight years, and that of salinized land grew from 50 per cent to 75 per cent. In the Tedzhen oasis, 48,000 out of 70,000 ha of irrigated land are salinized. And in Turkmenia, 86.7 per cent of all irrigated land is salinized. In Uzbekistan, moderately and severely salinized soils constitute 60 per cent of all irrigated land. In some regions, the areas of salinized land are even larger; in Central Feigana, for example, they amount to 83.9 per cent, including 7.1 per cent of severely salinized and 31.3 per cent of moderately salinized irrigated lands (Popov 1988). In the Karakalpak Republic, 377,000 ha out of the 485,000 ha of irrigated land are salinized. Asimilar situation prevails in other republics of the Aral basin: 35 per cent of irrigated land is salinized in Tadzhikistan, 40 per cent in Kirghizia, and 60-70 per cent in Kazakhstan (Khakimov 1989).
As a result of decreases in river runoff and falling river water levels, and also owing to the fall in the Aral Sea level, the Syr Darya and Amu Darya river-beds have begun to function as drains, leading to even more rapid desertification of the coastal band.
According to F. I. Khakimov (1989), alluvial-meadow and swamp-meadow soils are shifting into meadow-takyr and meadow-deserts. Meanwhile, the humus content of soils has decreased, and sodium and magnesium levels in the soil have risen. V. A. Popov (1988) has predicted that, if the desertification trend continues, the area of hydromorphic geosystems in the southern Aral area will decrease by 2,000 ha, but the area of the xeromorphic geosystems will more than double. The area of halomorphic geosystems, which increased almost sixfold from 1965 to 1985, will likely remain at the current level.
In the cultivation and inundation of land a number of animal species have perished. The total number of animals is decreasing, but the population density is increasing on the unploughed sites on the banks of canals. Thus, L. A. Persianova, Yadgarov, and Saraeva (1986) found that on irrigated land in the Dzhizak area 9 out of 27 species had disappeared and 4 more were endangered. Of 21 reptile species, 2 will probably perish completely.
As a result of the Syr Darya delta drainage, flocks of waterfowl have been displaced during migration from the lower reaches of the Syr Darya river to the lakes of Turgai. Accumulations of white and Dalmatian pelicans have been observed beyond the northern boundary of the former Aral Sea (Novikova and Zaletayev 1985). Accumulations of migrating waterfowl have also appeared both in water reservoirs and in filtrational lakes formed in Central Asia (Zaletayev 1976). Meanwhile, newly formed wastewater basins have created conditions for large hibernation sites for waterfowl in a number of regions. Overall, the diversity of mammals inhabiting the Aral area has decreased from 70 to 30 species and the number of bird species from 319 to 168. The disappearance of nesting sites for many bird species has led to the disappearance of 38 of the 173 bird species nesting in the lower reaches of the Syr Darya.
Tugai communities in the deltas are also endangered. These tugais were extremely rich florally since they had 576 superior plants, including 29 endemic to Central Asia. Currently, owing to desertification, 54 species are on the verge of extinction (Novikova 1985; Sagitov, personal communication). Reed thickets, meanwhile, have perished in the Karakalpak Republic in the Amu Darya delta, and the relict tugai forests are also becoming extinct.
Data on environmental pollution at the beginning of the study period are practically absent; therefore, only data on current pollution levels can be provided.
Soil pollution in the Aral region is observed throughout the agricultural zones. In almost all regions the DDT content in soils is about 27 times above the maximum permissible concentration (MPC) and in some regions it is 46 times higher (Izrael and Rovinski 1990). Territories with polluted soils amount to about 30-66 per cent of the surveyed areas. These soil pollutants end up in water sources. Organochlorine pesticides are recorded along the entire length of the Amu Darya and Syr Darya, and at some sampling stations their content exceeds MPC values. A specific peculiarity of the Aral basin is the increase in river-water mineralization owing to the discharge of drainage waters from irrigated massifs.
Mineralization of drainage runoff from irrigated massifs reaches 20 g/l, usually amounting to 2-8 g/l. The value of salt removal from irrigated massifs with drainage runoff reaches 60-70 t/ha. A significant part of the drainage runoff is discharged to rivers, leading to increased river-water mineralization. Thus, Syr Darya water mineralization increased in the lower reaches from 0.8 g/l, in 1960 to 1.8 g/l. in 1985 (fig. 3.3). A similar process is observed in the Amu Darya, where river-water mineralization has reached 1.7 g/l.
As a result of extensive irrigation, the ion content of river runoff has changed. Salt removal from the irrigated massifs has exceeded that from land in areas of river runoff formation (table 3.3). In spite of the reduction in the volume of river runoff, the inflow of salts to large lakes has increased. The Caspian Sea has experienced similar impacts. New lakes of ion surface runoff have also appeared, the largest of which are the Arsanai lake in the Syr Darya basin and the Sarykamysh lake in the Amu Darya basin.
Fig. 3.3 River water mineralization in the Syr Darya, 1950-1990
Table 3.3 Ionic surface runoff in the Aral region (millions of tons per year)
|Prior to the last stage of irrigation development||At the present stage|
|Inflow from outside the region||13||13|
|Removal from land in the areas of runoff formation||41||38|
|Removal from irrigated land||-||67|
|Supply to land and to small salt lakes||25||76-66|
|Runoff to Sarykamysh and Arnasai salt receiving lakes||-||32|
|Runoff to the Aral Sea||29||10-20|
a. Data on ionic runoff are not precise, since continuous transformation of ionic runoff is still proceeding.
Salt flow to land has also increased, owing to water filtration, the withdrawal of groundwater for irrigation, and the discharge of drainage waters to oasis margins. Thus, irrigation developments have led to the mobilization of enormous salt masses accumulated earlier in the land and their redistribution over a vast territory of arid areas.
Air pollution in the Aral Sea basin is significant, as it is in many other regions of the former USSR. Thus, in the Tashkent area in the Fergana valley, and in some other nearby regions, air pollution exceeds maximum USSR permissible concentrations by 1.5-6 times. Pollution connected with agricultural production is, however, the most dangerous problem. Under conditions of cotton monoculture, extensive amounts of fertilizers, defoliants, and herbicides were used on irrigated land. Fertilizer use on irrigated land in Central Asia, for example, exceeds the level in Russia by several times. DDT, now forbidden, was widely used in the region until 1982, and a high DDT presence in soils is still apparent (table 3.4). Up to 54 kg/ha of pesticides are still used in the basin (as compared with a mean value of 3 kg/ha in the USSR).
The use of airplanes in the application of pesticides has also caused air pollution and has led to direct human exposures. Pesticides have also entered the food chain through fodder and drinking water. Up to 13 per cent of water samples from open reservoirs and 37 per cent of food products have contained pesticides.
Contents - Previous - Next