Estimating the impacts of climate change and human activity on regional hydrological cycle in the Aral Sea Basin
Overcoming regional water problems requires an understanding of both natural hydrological conditions and social and historical changes in regional water policy. Central Asian nations face serious water problems, and here we review the circumstances surrounding water resources in the Syr Darya and Amu Darya River basins in terms of water management changes and climatic trends. Two major rivers – the Syr Darya and the Amu Darya – originally flowed into the Aral Sea, once an inland lake that was the world’s fourth largest in water area. In the 1960s, the Soviet Union started large-scale irrigation projects in the vast dry steppes extending through the mid and downstream basins of these two rivers. Irrigated land grew from about 4.5million hectares (ha) in 1960 to about 7 million ha in 1980.
During these two decades, the population almost doubled from 14 million to 27 million, as did the amount of water taken from the rivers, from 64.7 km3 to 120 km3 – over 90 percent of which was used for irrigation. By 1999, irrigated farmland occupied 7.90 million ha and water taken from the rivers ranged from 110 to 117 km³. The main crops promoted were water-consuming – cotton, rice, wheat, maize, and grass. The huge increase in water diverted to irrigated areas dramatically decreased water flowing into the Aral Sea, disturbing the balance between water inflow and evaporation from the lake, drastically reducing the lake area and rapidly raising the saline concentration from 10‰ to 35‰. The Aral Sea became divided into the Small Aral in the north and the Large Aral in the south, both of which continue to shrink.
Reduction has been particularly swift in the Large Aral, where water is shallower, especially in the east, and the Large Aral is being separated into eastern and western parts. The combination of these processes has triggered many problems, including the disappearance of fisheries from the Aral Sea, the contamination of basins by agricultural chemicals, damage to the health of local inhabitants including a lower life expectancy, and the deterioration of the environment and basin ecosystems. After the Soviet Union’s collapse in 1991 and the independence of republics around the basins, bitter conflicts arose over water use from the two natural rivers between countries upstream and downstream.
We focus on water issues involving the Syr Darya and Amy Darya that emerged following the breakup of the Soviet Union. In addition the impact of water management changes on water circumstances in the basins, and trends of general hydrological conditions due to regional climate change are to be examined. For example, meteorological data shows that the Aral Sea basin has experienced strong temperatures warming over the last 30 years, melting snow earlier in spring and causing water shortages in summer. Some local researchers have reported extensive land cover changes caused by both human impact and temperature warming. To clarify this problem, we used long-term hydro meteorological and satellite data analysis. Additionally, a meteorological station has been installed in order to understand the hydrological system and to make a hydrological modeling of the Kyzylkum desert in Uzbekistan since 2006.