Academic literature on the topic 'Vakhsh River (Tajikistan)'

The Vakhsh River is one of the major rivers in Tajikistan. The quantitative analysis of watershed topography and developmental characteristics in Vakhsh River catchment can reflect the morphological characteristics of the region, which is of great significance for revealing the quantitative relationship between the hydrological and the geomorphological process. In this paper, the D8 algorithm and the spatial analysis method were used to extract the river networks, the catchment boundary profile lines and the longitudinal valley profile lines of the four major tributaries in the Vakhsh River from the ZY3-DSM of 10 meters resolution. On this basis, five quantitative indices including the frequency of wave, amplitude of wave, gully density, the longitudinal slope and roundness rate were used to analyze the watershed landform and its development degree. According to the experimental results, the catchment have a high surface complexity and a mature landform. Yovonsu river catchment which is in the downstream of Vakhsh River is oval and has low terrain complexity with large frequency and small amplitude. Among the midstream and upstream, the Mukson River has developed into geriatric terrain that is the most mature and has the highest surface complex, while the Obikhingon River and the Kizilsu River have developed into a stable maternal terrain. In terms of topography, the boundary elevation of the Obikhingon is basically in accordance with the normal distribution, while the Kizilsu and the Muksu show a peak state with elevations of 4,000–5,000 m and 5,000–5,500 m, respectively.

The Rogun hydropower plant is being constructed in Tajikistan, in the valley of the Vakhsh River. The construction site is located in a narrow gorge separating the Vakhsh and Surkh-Ku ridges. Most of the hydroelectric complex structures are located within a single tectonic block, which is bounded by two faults - Ionakhsh and Gulizindan, which are proximal to the Vakhsh regional fault. The study of stress distribution around the diversion tunnel was carried out by numerical simulation, which aimed to identify the stress distribution in the strongly dislocated heterogeneous rock massif before and after the tunnel creation. The underground cavity of the tunnel is a significant factor influencing the natural stress field of the rock massif. An area with critical values of the strength coefficient in the working roof, caused by the presence of a weak layer of Lower Cretaceous siltstones, is revealed in the tunnel location. The size of this area reaches two tunnel diameters. The change of stresses and their concentration around the underground working can cause deformations in the roof (collapse or rock bumps).

Millions of people in Uzbekistan, Turkmenistan, Tajikistan, and Kyrgyzstan are dependent on the freshwater supply of the Vakhsh River system. Sustainable management of the water resources of the Vakhsh River Basin (VRB) requires comprehensive assessment regarding future climate change and its implications for streamflow. In this study, we assessed the potential impacts of projected climate change scenarios on the streamflow in the VRB for two future periods (2022–2060 and 2061–2099). The probable changes in the regional climate system were assessed using the outputs of five global climate models (GCMs) under two representative concentration pathways (RCPs), RCP4.5 and RCP8.5. The probable streamflow was simulated using a semi-distributed hydrological model, namely the Soil and Water Assessment Tool (SWAT). Evidence of a significant increase in the annual average temperature by the end of the 21st century was found, ranging from 2.25 to 4.40 °C under RCP4.5 and from 4.40 to 6.60 °C under RCP8.5. The results of three GCMs indicated a decreasing tendency of annual average precipitation (from −1.7% to −16.0% under RCP4.5 and from −3.4% to −29.8% under RCP8.5). Under RCP8.5, two GCMs indicated an increase (from 2.3% to 5.3%) in the average annual precipitation by the end of 2099. The simulated results of the hydrological model reported an increasing tendency of average annual streamflow, from 17.5% to 52.3% under both RCPs, by the end of 2099. A shift in the peak flow month was also found, i.e., from July to June, under both RCPs. It is expected that in the future, median and high flows might increase, whereas low flow might decrease by the end of 2099. It is concluded that the future seasonal streamflow in the VRB are highly uncertain due to the probable alterations in temperature and precipitation. The findings of the present study could be useful for understanding the future hydrological behavior of the Vakhsh River, for the planning of sustainable regional irrigation systems in the downstream countries, i.e., Uzbekistan and Turkmenistan, and for the construction of hydropower plants in the upstream countries.

Abstract. In the often discussed Aral Sea basin (Central Asia), water availability depends essentially on the high mountains located in its eastern part, especially from the Pamir Alay Range where the Vakhsh and Pyandj Rivers, the main tributaries of the Amu Darya River, flow. In this region, the cryosphere, glaciers, and snow cover significantly impact the water cycle and the flow regime, which could be deeply modified by climate change. The present study, part of a project funded by the EU FP6, analyzes the hydrological situation in six benchmark basins covering areas between 1800 and 8400 km2, essentially located in Tajikistan, with a variety of topographical situations, precipitation amounts, and glacierized areas. Four types of parameter are discussed: temperature, glaciers, snow cover, and river flows. Two time periods are considered: (i) a long time series ending in the 1990s with the collapse of the Soviet Union and based on field observations and data collection; (ii) a May 2000 to May 2002 interval, using scarce monitored data and satellite information to follow snow cover dynamics. The results confirm the global homogeneous trend of temperature increase in the mountain range and its impacts on the surface water regimes. Concerning the snow cover, significant differences are noted regarding the location, the elevation, the orientation and the morphology of the respective basins. Finally the expected changes in the flow river regime are regulated by the combination of the snow cover dynamics and the increasing trend of the air temperature. It confirms the high sensitivity of this region to the warming as identified by the 4rd IPCC Assessment Report.

Rogun dam is a 335m high clay core rockfill dam which will be constructed on Vakhsh River in Tajikistan. Originally, two diversion tunnels with similar geometry were designed for discharging the seasonal floods, up to 3290m3/s. River diversion was carried out in November 1987 and a 45m high rockfill cofferdam was constructed. However, because of two collapses in the diversion tunnels, the cofferdam was overtopped in May 1993. Reconstruction of these tunnels started in 2009 and the collapsed areas were repaired. Nowadays, the design of complementary rehabilitation including new concrete lining for those parts of the tunnels will be used as tailrace tunnels are underway. The present paper describes the present conditions of diversion tunnels No. 1 and 2, explains the procedure used for the structural design of these tunnels, and presents the results of such design.

Strains among the states of Central Asia caused by overuse of the region?s scarce water resources have been increasing in recent years. This is especially true for the relations between Tajikistan, upstream, and Uzbekistan, downstream, on the Amudarya River. Major controversy exists over constructing Rogun Dam on the Vakhsh River, a tributary of the Amudarya River. Construction of Rogun Dam, with a planned height of 335 m (1099 ft), began in 1976 but was stopped in 1991 with the breakup of the former Soviet Union. The intent of this dam is to supply Tajikistan with energy, but a side effect will be the changed flow regime of the Amudarya River to downstream states (especially Uzbekistan). The major impact will be on the agricultural sector of Uzbekistan. The objectives of this study are to estimate the monetary impacts of Rogun Dam and propose mitigation measures to minimize impacts. The study investigates the nature and extent of those impacts and indicates policy implications to mitigate negative consequences of the possible water shortage in summer by assessing the baseline situation and comparing that situation with future status-quo (no changes) level of water. Future water shortage could cost Uzbekistan annually over US $609 million economic loss in agriculture, reduce the country?s GDP by 2.2%, and result in 336,000 unemployed people. If Uzbekistan changes its present water use practice and increases water use efficiency, the future water shortage during irrigation periods will not as seriously affect the country?s economy, as adaptive management measures could cut the losses by 40%.