Multiobjective Water Resource Allocation Model for Toktogul Reservoir

by Daene C. McKinney and Ximing Cai

The principal surface water sources of the Aral Sea region are the river basins of the Amudarya and Syrdarya. The source of these rivers is in the mountainous republics of Kyrgystan and Tajikistan where water use for energy production competes with water use for agricultural production in the down-river countries of Kazakstan, Turkmenestan, and Uzbekistan and flows into the Aral Sea. The issues surrounding the Aral Sea crisis are international, and policy solutions require regional cooperation among the newly independent Central Asian Republics (CAR). Since water flows among all of the Republics and since it is shared in different ways, there must be significant cooperation among the water sharing Republics, especially in the Syrdarya basin.

One of the major sources of the Syrdarya River is the Naryn River in the mountainous Kyrgyz Republic. This source is controlled by a cascade reservoirs of which Toktogul Reservoir is the major one. The downstream countries do not have much local water source, but they do have large irrigated lands and they must rely on the water releases of the upstream countries. Under the Soviet Union, the management of this river was an intra-national issue and the river was managed by a central authority for the combined benefit of the entire region. The primary benefit derived from the management of the river was the provision of water for irrigated agriculture in Uzbekistan and Kazakstan. Upon the collapse of the Soviet Union in 1991, the river basin was split into four sovereign nations with competing interests in the waters of the Syrdarya River. The Kyrgyz Republic’s primary objective in managing the river is to maximize the production of hydroelectric power in from Toktogul reservoir. In conflict with this are the downstream countries, Uzbekistan and Kazakstan, whose objectives are to maximize their utilization of water for irrigation. This situation has led to a major international conflict over the waters of the Syrdarya.

The critical factors affecting this international water management problem are the temporal characteristics associated with the objectives of the upstream and downstream countries. In the Kyrgyz Republic, the peak demand for domestic power occurs in winter, while in the downstream countries, the peak demand for irrigation water occurs in the summer.

The actions of the upstream and the downstream countries are neither totally consistent nor totally in conflict with one another. Since the major runoff period occurs in the summer, the Kyrgyz Republic would like to release some water in the summer period, which helps to meet the downstream irrigation needs; but at the same time, they would like to store water for power generation in the winter when there is little runoff. The Kyrgyz Republic’s preferred release during April to September is generally expected to be less than the downstream irrigation requirement, except in a wet year. Generally, the Kyrgyz Republic generates more hydroelectric power in summer months than what they need for domestic use, and in the winter months they have to use thermal power plants to meet the power demand. Therefore they try to export hydroelectric power during the summer months to compensate for the cost of fuel for the thermal power plants in winter.

Since more than one republic is involved in downstream irrigation water allocation, an even distribution of water use rights may be considered equitable. That is to say, in case of a water shortage, it might be fair for various demand sites to share the shortage. On the other hand, for crop irrigation needs, water supply should be even from month to month during the vegtation season. For example, if June irrigation demand is totally satisfied, but only half the irrigation demand is satisfied in July, this will not be good for plant growth. It may be better to deliver, say, 75% of the irrigation demand over in both June and July.

The objective of the work described here is to aid the countries of the Syrdarya River basin to develop a long-term water and hydroelectric power sharing agreement. As part of these activities a policy analysis tool has been developed to help decision makers from the Syrdarya basin republics come to an agreement for the allocation of water releases from Toktogul reservoir on the Syrdarya River. This multicriteria decision analysis tool can be used to promote an understanding of the tradeoffs between water releases made for agricultural production and those made for hydroelectric power generation. The scope of the work addresses the need for the development of a multi-objective screening model to aid in the determination of fair and equitable arrangements for sharing the waters of the Syrdarya River between the CAR countries of Kyrgistan, Uzbekistan, Kazakstan, and Tajikistan. Such a model may prove to be useful in assisting CAR decision makers in negotiating agreements or treaties between the countries of Kyrgistan, Uzbekistan, Kazakstan and Tajikistan over the distribution of releases from the reservoir.

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