The water balance of Central Asia is widely discussed by many authors and is studied in different institutes, such as the Central Asian Institute for Applied Geosciences, the Faculty of Geography in the Moscow State University, the Department of Geography in the Western Michigan University, etc. [1
]. The present state of the Aral Sea reflects the catastrophic processes in the Central Asia water balance which are connected with both global climate change and anthropogenic processes, such as the realization of the Kara-Kum Channel Project and damming the water outflow from the Caspian Sea to the Kara-Bogaz-Gol Bay [10
The state of the Aral Sea provokes the anxiety of governments of Central Asia and neighboring countries. In actuality, the Aral Sea drying can significantly impact the regional climate, as well as having an influence on the global climate [18
]. A major problem of confronting countries in Central Asia is the redistribution of water resources and optimization of their usage [20
]. This problem has arisen because of the diversion of the Amu Darya and Syr Darya rivers for agricultural purposes and energy production. Unfortunately, this action was initially realized without a scientific environmental impact assessment. Continuation of current policies and practices, with respect to the regional water cycle, is counter-productive to an effective resolution of the existing problems [22
Optimization of using the Syr Darya and Amu Darya waters requires the coordination of strategic solutions by five countries of Central Asia concerning the distribution of restricted water resources [24
]. Regional water crises take place as a result of the absence of effective agreements among Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, addressing the coordinated use of the main water source—the Amy Darya River [21
]. Over the last century, the Soviet Union has constructed a system of dams and irrigation channels to solve the irrigation problem that was stimulated by the rapidly growing population. The transfer of water from Siberian Rivers to the Aral Sea Basin was discussed as one possible solution of the water crisis in Central Asia [7
]. The Soviet Union’s disintegration closed the discussion on the resolution of this problem and the Aral Sea water level continues to drop. The water resources of Amy Darya and Syr Darya are formed within the framework of their drainage basin of 534,739 km2
and mainly in the high mountains [25
]. Data approximations with respect to water consumption associated with population growth in the countries of Central Asia are as follows: Uzbekistan—2596 m3
/year/person, Turkmenistan—4044 m3
/year/person, Tajikistan—1843 m3
/year/person, Kyrgyzstan—1371 m3
/year/person, and Kazakhstan—1943 m3
/year/person. Approximately 93.4 percent of the Amu Darya River water is used for irrigation [20
]. Total draw-off from Amu Darya equals 61,500 km3
/year. The effectiveness of irrigation systems is about 50 percent [20
Many experts proposed different methods for overcoming the Aral Sea water crisis. Spoor [27
] discussed the approaches to the efficient water management and sustainable land use in the Former Soviet Central Asia, when decisions were made centrally. In the post-Soviet era, decision making procedures are complicated and the political independence factor of five countries of Central Asia makes water resources allocation possible only through contracts in the framework of collaborative agreements. Micklin [11
] analyzed the primary motivations, both climatic and economic, concerning the transfer of the flow of Northern European Rivers southward to Central Asia. Considering different nominally, practically realized projects, Micklin [12
] made the conclusion that restoring average river inflow to the Aral Sea at about 56 km3
/year needs more than 100 years. Kostianou et al. [28
] consider in detail the satellite monitoring possibilities to optimally manage water resources in Turkmenistan, at the zone where Kara-Bogaz-Gol and other important elements of the Aral Sea water cycle are located. It is evident that stabilization of the Central Asia water balance can be realized only by optimal control of existing water resources including the Amu Darya and Syr Darya Rivers. The solution of existing problems is usually realized by means of modeling tools [6
]. A new method based on the modeling of the water balance of Central Asia and a scenario for its control is proposed in this paper.
3. Results and Discussion
Drastic changes of the water cycle in Central Asia after known anthropogenic actions seem impassable under existing economical and political systems taking place in five independent republics. Further, the Aral Sea ecosystem degradation will result in further deterioration of the human population’s living conditions. Realization of the EPS necessitates their cooperation, including that of Iran. The EPM allows the evaluation of the EPS realization to partially restore the sea’s hydrology along with its area stability. It is supposed that current and future climatic trends in the Aral Sea region conform to global climate change [18
]. Wind fields in this region are represented in Figure 3
Simulation experiments are realized for spatial resolution Δϕ = Δλ = 1/6° and temporal scale Δt
= 1 day. Equations (1) and (2) are digitized according to these parameters. Boundary conditions for balance equations are evaluated on the base of existing meteorological and satellite data of Central Asia [28
]. The starting time for the EPS realization is t0
= 2020 when, WCS
= 78,200,000 km3
= 15 km3
= 75 km3
= 38 km3
= 79 km3
= 42.6 km3
= 150 km3
, and WLS
= 0.00011 km3
It is accepted that evaporation/precipitation relations for principal water sources to the atmosphere humidity are fluctuated no more than 5% during the next decades and have average assessments, as represented in Table 2
. As it was shown by in-situ and remote sensing measurements, the land cover elements play a slight role in comparison with reservoirs in the water balance of Central Asia [4
]. Land surface plays a certain role in the heavily populated areas where agricultural vegetation is prevailing. Total database of land covers in Central Asia was synthesized in a framework of remote sensing measurements by means of flying laboratory IL-18 of the Former Soviet Union [5
]. This laboratory was equipped by the radio-locators with synthetic aperture, microwave radiometers of different wavelengths, gravimetric and inertial devices, large-format and frame TV, aero-camera and other complementary devices. The land covers and reservoirs are classified with spatial resolution of 200–500 m, depending on the region.
Practically, water evaporated from agricultural irrigable areas does not arrive at the Aral Sea zone because of the wind rise. Therefore, simulation experiments show that atmosphere/land surface water balance outside irrigable areas is practically neutral.
The following EPS versions are considered:
EPS-1: Only Kara-Bogaz Gol is used as a natural evaporator.
EPS-2: Kara-Bogaz Gol and other natural evaporators are used.
EPS-3: In addition to EPS-2, the river water diversion is decreased by 5% and rainmaking technology is used.
EPS-4: In addition to EPS-2, the river water diversion is decreased by 10% and rainmaking technology is used.
The precision of simulation results is mainly defined by the climate scenario. Existing scenarios of global climate change propose a wide range of average global temperature change. This problem and its connected discussions are not considered here. Following from Krapivin et al. [5
], the next climate change in the Central Asia scenario is accepted. Three climatic zones are marked out: mid-latitude desert, steppe and humid continental. During the last years from 1960, climate change in these zones has increased average annual temperatures in the range from 0.1 °C to 1.1 °C. It is supposed that this trend in change of the average annual temperature is preserved until 2150.
Finally, simulation results are given in Table 3
and Table 4
, which show hydrological elements of the Aral Sea Basin in their dynamics after the EPS-4 realization. These results demonstrate the existence of an effective strategy for the management of the Central Asia water resources using the EPM manipulations and tools for the big data processing [56
Certainly, use of the EPS-4 has numerous restrictions and uncertainties. Nevertheless, 10 percent of river flow return is really realized taking into consideration that water losses in irrigation systems of Central Asia are about 50 percent. A quota of 10 percent equals 4.5 ± 0.2 km3
/year. Water losses from irrigation systems lead to waterlogging and an increase of the level of ground waters. During the last two decades, the level of ground waters was increased from 3 m to 1.2–1.5 m in many regions of Central Asia [12
Existing separate data shows that the Aral Sea area had been reduced to 78% of its 1960 size and water volume had decreased by about 90%. The most dangerous situation is formed in Central Asia, due to the increased salinity, by more than 12 times the salinity of sea water, which negatively impacts the fishery industry. The salinity of the Aral Sea increased from 10 g/L to 135g/L, depending on separated basins of the Aral Sea [11
]. The Aral Sea prior to its modern desiccation had an average salinity around 10 g/L. As a result, the Aral Sea degradation leads to socio-economic and public health problems, taking into account increased sand-storms and desertification [36
]. Present-day processes of free salts migration cause negative consequences for agriculture within the Central Asian countries. Remote sensing tools, such as the IL-18 laboratory, can provide regular monitoring of land covers with the assessments of their characteristics and delivering reliable information for decision making offices.
Realization of the EPS-4 gives perspective to partly restore the Aral Sea within this century. Detailed analysis of simulation experiments allows the assessment of different components of the Central Asia water cycle and the understanding of the role of each country in water cycle stabilization. As it follows from Table 3
and Table 4
, the Aral Sea recovery can be realized under conditions which are to be acceptable for all countries of Central Asia.
The recovery scenario proposed and partly analyzed in this paper opens the perspective to identify a solution to the Aral Sea problem and to overcome the existing contradictions between the governments of Central Asia concerning optimal and equitable management of water resources. Many experts propose different views on this problem—from optimistic to pessimistic [1
]. An optimistic project is realized in Kazakhstan by means of Amu Darya riverbed management [9
In actuality, existing runoff of Amy Darya and Syr Darya to the Aral Sea is assessed by ≈11–13 km3/year when 43–47 km3 of river waters are taken away for irrigation (92%), industry (4.3%) and population use (4.4%). The EPS-4 provides for the increase of up to 20 km3/year of river runoff to the Aral Sea, together with additional evaporation of the Caspian water and deployment of rainmaking technology, such as cloud seeding with, for example, silver iodide, potassium iodide, frozen carbon dioxide, or liquid propane. In this case, precipitation in the Aral Sea Basin can potentially increase to ≈1500–2000 mm/year, depending on the climatic situation under evaporation of ≈900–1000 mm/year. The result of the EPS-4 utilization is a function of many uncertain environmental conditions, such as climate change, strategies of the independent republics in the water use, population growth and the river runoffs to the Caspian Sea.
The Aral Sea crisis is to be solved at the expense of a complex approach to the sustainable development of the Central Asian region, taking into consideration an array of scientific, social and ecological aspects. It is evident that the following actions are to be initiated:
Reconstruction of existing old irrigation systems;
Development and introduction of effective irrigation technologies such as drip irrigation;
Reconstruction of municipal water supply systems, and
Optimization of the drainage runoffs.
Preliminary analysis of the Central Asia water cycle shows that there exist reserves for the improvement of the ecological situation and for ultimate initiation of the Aral Sea recovery process. Existing reservoirs such as Sarykamysh Lake (≈5000 km2
), geographically located between the Caspian Sea and the Aral Sea, can be water sources for the Aral Sea. Lake Balkhash (16,400 km2
) can also be considered as an important element of the Aral Sea water balance. Certainly, realization of these actions requires the adequate capital investments and scientific efforts to optimize this process. Principally, global ecoinformatics proposes tools for the solution of such environmental tasks [5
]. Realization of the EPS-4 is possible in the framework of the UN Program, when it is possible to focus scientific efforts on the synthesis of global water cycle models, in the framework of which EPM can be used as a sub-block. In this case, the optimal strategy for Central Asia water balance can be defined and realistic monitoring procedures can be identified. Only in this case, social and economic stresses existing in practically all countries of Central Asia will find a solution and human vulnerability will be reduced. Undoubtedly, reliability of these results depends on regional climate change scenarios [18
]. Therefore, it will be created in such a manner that information-modeling technology would combine operative monitoring data with the water balance model and with assumptions of timely decision making, to correct regional changes in the agricultural and social strategies.
Certainly, the reliability level of modeling results is an important aspect of the results shown in Table 3
and Table 4
. Table 5
gives some characteristics for the EPM precision level. Average deviation of the EPM results from the observed volume of the Aral Sea equals 8.3%. The EPM precision can be considered as consistent with the reliable description of the Aral Sea hydrological regime. As it follows from Table 5
, the EPM can be considered as a tool for primary assessment of different scenarios for the Aral Sea water balance management. It is evident that practical EPM use needs additional development.
The results of Table 3
show that separated water bodies of the Aral Sea, existing at the present time, will be merged after 35–40 years of EPS-4 realization. It shows that a principal solution of the Aral Sea problem exists, and its volume of the 1960′s can be reached during visible time. Versions of the Evaporation/Precipitation Scenario, considered here, will help to form the recovery strategy [6
Overcoming the Aral Sea crisis needs preliminary solutions of socio-economic problems existing in Central Asia, which at the present time is a barrier for the constructive consideration of alternative plans. Many publications propose different methods to search for the solution to the Central Asia water problem, including scenarios and models [5
]. It is evident that the Aral Sea does not exist in isolation from the Caspian and Black Seas, and the Don and Volga Rivers. Therefore, these water resources are to be taken into consideration under the improvement of the method considered in this paper.