Abstract:
The rationalization of water use for irrigation can be achieved through the optimization of water distribution between irrigation districts and water users. One of the basic steps in the rationalization of water use for irrigation is the optimization of water distribution for large water districts.
The distribution of limited water resources in the small river systems in the Aral Sea zone is problematic, because of the absence of water share agreement between countries, which were part of the Soviet Union and absence of the economical and environmental indices of water use in the region. One of these small water systems in Uzbekistan is the Zerafshan River system. The Zerafshan River begins in the Nurata-Turkestan Mountains of Tajikistan-Uzbekistan highlands. Its length is 500 km, and the average flow changes from 220-320 cubic m/sec at the headwaters, to 3 cubic m/sec where it ends. . In the past, the river flowed into the Amudarya River, but presently it ends in the Bukhara Oasis in southern Uzbekistan. The river provides water for 5 regions of Uzbekistan and a small part of Tajikistan. The Samarqand region of Uzbekistan receives 60% of its total flow, which is used for irrigation and domestic use. In the past Tajikistan captured 10% of average flow, but plans to increase the amount of water taken to the 25% in the future. The Kashkadarya region uses 3-5%, and Dzijjak region uses 2-3% of Zerafshan water, mostly for irrigation. The Navoi and Bukhara regions of Uzbekistan use the other 25-30% of water. The Navoi region uses water for irrigation and for cooling the Navoi power plant. The plans of Tajikistan to increase water withdraw from the Zerafshan River and continuously water shortage in the Samarqand region and the low efficiency of the water use in the lower part of the river requires analyzing and optimizing the water distribution in the Zerafshan river basin.
