Knowledge Base
 

Surface water

Central Asian water resources are comprised of renewable surface water and groundwater, as well as return flow associated with human activity. Water resources are mostly available in the Syrdarya and the Amudarya basins. Independent basins (closed drainage basins adjacent to the Amudarya basin ) are formed by the Kashka Darya, Zerafshan, Murgab and Tedzhen rivers, which have lost their hydrological links to the main river. The water resources of Kazakhstan and Kyrgyzstan are also formed in other basins, e.g. Kazakhstan has seven additional independent river basins, while Kyrgyzstan has four.

Surface flow formation

Central Asian water resources are comprised of renewable surface water and groundwater, as well as return flow associated with human activity. Water resources are mostly available in the Syrdarya and the Amudarya basins. Independent basins (closed drainage basins adjacent to the Amudarya basin ) are formed by the Kashka Darya, Zerafshan, Murgab and Tedzhen rivers, which have lost their hydrological links to the main river. The water resources of Kazakhstan and Kyrgyzstan are also formed in other basins, e.g. Kazakhstan has seven additional independent river basins, while Kyrgyzstan has four.

Hydrologically, the region comprises three major zones: flow formation zone; flow transit and dispersion zone, and river deltas . The construction of large dams and reservoirs tends to impact significantly on flow regimes in downstream river sections. In the transit and dispersion zones, hydrological regimes and water quality are changed as huge volumes are withdrawn for industry and agriculture, while return flows containing salts, chemicals and other pollutants find their way back into the river.

The Amudarya is the largest river in the region. It stretches for 2,540 km from the Pyandj headstream and has a basin of 309,000 km2. From the point where the Pyandj flows into the Vakhshay, the river is known as the Amudarya. The river’s main catchment area is in Tajikistan, from where it flows along the border between Afghanistan and Uzbekistan, crosses Turkmenistan, flows back into Uzbekistan and finally into the Aral Sea in Uzbekistan.

In its midflow, the Amudarya is joined by two right tributaries, the Kafirnigan and the Surkhan Darya, and one left tributary, Kunduz. Futher down to the Aral Sea, it is not joined by a single tributary. Melting snow and glaciers provide whatever water it receives. The flow, therefore, is the strongest in summer and the weakest in January and February. This annual pattern favours the use of the Amudarya waters for irrigation. All along the valley from Kerka to Nukus, the Amudarya loses a large part of its flow through evaporation, filtering and abstraction for irrigation. In terms of silt content, the Amudarya clearly ranks first in Central Asia and is one of the first in the world.

The Syrdarya ranks second in terms of run-off , even though it is actually the longest river in Central Asia. From the source of the Naryn, its tributary, , the Syrdarya has a length of 3,019 km and the basin area of 219,000 km2. Its sources are in the Central Tyan Shan Mountains. The Syrdarya is formed where the Naryn and the Kara Darya converge. It is fed by melting glaciers and, to a larger extent, by melting snow. The river is at its fullest in spring and summer, starting in April and reaching its peak in June. Its main catchment area is in Kyrgyzstan, then the river crosses Uzbekistan and Tajikistan and empties into the Aral Sea in Kazakhstan.

Other major inter-State rivers are:

  • The Chu, 1,067 km, watershed area 62,500 km2, originating in Tyan Shan in Kyrgyzstan and dissipating in the Asikol depression , in Kazakhstan;
  • The Talas, 661 km, watershed area 52,700 km2, originating in Kyrgyzstan and terminating in the Muyunkum sands in Kazakhstan;
  • The Tarim, 2,030 km, watershed area 1 million km2, originating in Kyrgyzstan and Tajikistan, and flowing mostly through China; and
  • The Irtysh, 4,240 km, watershed area 1,643,000 km2, part of it crossing Kazakhstan in the east and flowing into the Ob river in the Russian Federation.

Extremely important, in terms of their integrated use for the socio-economic development of individual countries, are also the waters of the Ili river in Kazakhstan, Lake Issyk Kul, etc.

In future, the Islamic Republic of Iran, Afghanistan, the Russian Federation and China may become involved in the regional cooperation on water issues. It would, therefore, be appropriate to expand the scope of any further diagnostic studies to cover the concerns of all those countries.

Surface water resources

The overall assessment of water resources of rivers in the Aral Sea basin, including the Amudarya and the Syrdarya, has been made on the basis of the annual hydrological data published by the hydrometeorological agencies for the entire period of surveys within the framework of the WARMIS programme. The arithmetic mean of the total run-off in the Aral Sea basin for the entire period of observations (1911-2000) is 112.609 km3/year, inclusive of 77.093 km3/year for the Amudarya and 34.076 km3/year for the Syrdarya.

The resulting hydrographs describing the annual flow in the basins of the Amudarya and Syrdarya for the entire period under review reveal a certain pattern in the annual flow fluctuations. The hydrograph for the Amudarya basin indicates three 19-year cycles from 1934 to 1992, while that of the Syrdarya basin indicates six 12-year cycles from 1928 to 1997.

The average long-term run-off for each basin was assessed on the basis of an arithmetic mean of values relating to each complete cycle of water availability fluctuations. Such an approach makes it possible to reflect the trends that existed throughout certain periods – low- and high-water years, the years of lowering and rising water availability, etc. The Scientific and Information Centre of the Interstate Coordination Water Commission (SIC ICWC) recommends that the Amudarya trends should be assessed using the data from 1934-92 and those for the Syrdarya with data from 1951-1974. The resulting average flow is shown in tables 1 and 2. The average annual flow for the Amudarya basin was thus calculated to be 79.280 km3/year and that of the Syrdarya basin 37.203 km3/year. Hence, the total annual average for surface water (river) resources in the Aral Sea basin is estimated at 116.483 km3/year. This result agrees well with calculations carried out by the Sredazghiprovodkhlopok Research Institute in 1984 for the Amudarya (79.4 km3/year) and in 1987 for the Syrdarya (37.1 km3/year) under the master plans of integrated water resources use and conservation for the respective rivers.

Annual water resource availability varies – depending on water levels – from low (95% probability) to high (5% probability ) within the following range: 58.6 - 109.9 km3 for the Amudarya and 23.6 - 51.1 km3 for the Syrdarya.

The data in table 3 show that up to 25.1% of the entire run-off in the Aral Sea basin is formed in Kyrgyzstan, 43.4% in Tajikistan, 9.6% in Uzbekistan, 2.1% in Kazakhstan, 1.2% in Turkmenistan, and 18.6% in Afghanistan and the Islamic Republic of Iran.

This assessment requires further verification due to certain inconsistencies between figures contained in the National Reports by Kyrgyzstan and Tajikistan and the Glavghidromet Agency of Uzbekistan. For example, according to Kyrgyzstan’s report, 27.4 km3 out of the annual run-off of 46.04 km3 in the Syrdarya basin are formed on its territory, as are 1.93 km3 of the annual run-off of 93.42 km3 in the Amudarya basin. According to Tajikistan, 64 km3 (55% of the total annual river run-off in the Aral Sea basin) come from Tajikistan, including 62.9 km3 of the Amudarya and 1.1 km3 of the Syrdarya. The Hydrometeorological Agency (Glavghidromet) of Uzbekistan has argued that the SIC ICWC figures for the Syrdarya run-off in the Fergana Valley, the Arys river and its lower reaches are underestimated and those for the Chirchik overestimated. The Agency estimates the average annual run-off at the Syrdarya at 38.5 km3/year. It also finds that flow values for Turkmenistan (3.16 km3/year) are underestimated, while those for Tajikistan are overestimated. It should be noted that the run-off of the Kara Darya basin is partly formed in China, while that of the Amudarya partly comes from Afghanistan and the Islamic Republic of Iran , and that these values require further verification.Some inconsistencies have been found between tables 2 and 4 and the draft “Water Strategy Outline for the Aral Sea Basin”.

These discrepancies can be explained by differences in calculation methods and algorithms, as well as in the statistic samples used by different reports. However, these disparities are well within the limits set for the deviations from the average long-term run-off of the Amudarya and the Syrdarya, which, overall, makes existing estimates acceptable.