干旱区生态环境知识资源中心

Many Central Asian river basins are transboundary and characterized by a combination of extensive irrigation farming and an arid climate in the lower catchments. Both aspects - the transboundary character with different national water management plans and the overexploitation of the limited water resources lead to environmental, socio-economic and political problems which require - in the light of growing economies and the climate change - immediate solutions. Based on extensive field work and database evaluation (meteorological, hydrological and statistical data) from the Zarafshan River (Tajikistan/Uzbekistan) and the Tarim River (Kyrgyzstan/China), the status quo of the water resources is assessed and scenarios for the impacts of climate change on the water availability and water use are outlined. The results show that the extensive withdrawal of water for irrigation farming (with cotton being the most important crop) and the discharge of agricultural drainage water lead to severe water stress in the downstream parts of both catchments. The water deficit is so high that both rivers do not reach their tributaries (Amu-Darya and Lop Nor/Taitema Lake) any more. In the lower Zarafshan River (inter) national thresholds for several pollutants are exceeded permanently, while in the lower Tarim River the falling groundwater level is leading to the deterioration of the valuable Tugai forests. And while short-term measures, like the water transfer from the Boston Lake to the lower Tarim, can relieve some of the pressure, the ongoing climate change and socio-economic growth in both catchments require a more integrated, sustainable management approach. The rapidly shrinking glaciers in the headwater regions (-50% until 2050) and the drastic rise of the air temperature (and thus the evapotranspiration) will increase the annual water deficit (e.g. in the Zarafshan River catchment from currently 1.6 km(3) to up to 5.8 km(3)), making a more efficient (re-)use of water a necessity.