Surface water resources

The Amu Darya and the Syr Darya are the two primary rivers draining into the Aral Sea, with a total basin area of over 1,737,000 km2, which includes parts of six states. The estimated (pre-development) mean annual flow the two rivers used to discharge into the Aral Sea was 115 km3, but the estimated current total flow is around 10 per cent of that, due to massive water resource developments in the upstream parts of the Basin, which took place primarily in the second half of the twentieth century. The existing observational meteorological and hydrological networks in the Basin are not sufficient to support informed water management. The observational networks have declined since the 1990s and have not been improved since then. Regional water data sharing is also suboptimal at present. The flows of both main rivers in the Basin are primarily meltwater-dependent. Meltwater from snow and glaciers together contributes close to 70 per cent and 80 per cent of the mean annual river flow of the Amu Darya and Syr Darya Basin, respectively. Snowmelt runoff significantly outweighs that of glaciers. The Basin contains some of the world’s most complex and largest water management infrastructure, including the world’s longest canal, the Kara Kum in Turkmenistan, and what is soon to be the world’s highest reservoir, the Rogun dam in Tajikistan (currently under construction). Water infrastructure primarily serves two economic sectors-irrigated agriculture and hydropower. The network of irrigation canals in the Basin is dense and complex, covering thousands of kilometres. There are over 80 reservoirs in the Basin with an individual capacity of over 10 million m3. Upstream riparian countries-Kyrgyzstan and Tajikistan-are implementing ambitious development plans of new hydropower facilities. A characteristic feature of water infrastructure in the region is its ageing, causing it to require costly maintenance. Tajikistan, Kyrgyzstan, Uzbekistan and Turkmenistan are among the ten most vulnerable states to climate change in Europe and Central Asia. There is high uncertainty about possible future impacts on water availability, although warming trends are already clear and flow reduction is very likely in the distant future. Future reduction of glaciers and seasonal snow cover due to climate change will most likely affect mainly the seasonality of river flow and only marginally impact mean annual flow itself in both large basins