Abstract: Rational redistribution and utilization of water resources for farming irrigation and natural ecology in the mainstream area of the Tarim River Basin is critical to the ecology and environment improvement. The monthly satisfaction degrees of irrigation water of all the irrigated areas were simulated with the Water Evaluation and Planning System (WEAP) model based on the assigned water volume from the “Shortterm Comprehensive Improvement Plan of the Tarim River Basin” and the premise of the minimum ecological water demand. The water demand of natural vegetation was estimated through the quota method and the minimum water demand of the mainstream at 90% reliability rate of stream flow. The volumes of available water resources were computed by subtracting the ecological water demand and water loss along the river channel from the assigned quota, and they were 1.217×10⁹ m³, 7.45×10⁸ m³ and 5.69×10⁸ m³ under the stream flow reliability rates of 50%, 75% and 95%, respectively. The WEAP model was developed for estimating the satisfaction degrees of irrigation water in the mainstream area of the Tarim River Basin by inputting the modeling factors and data, such as the rivers, river channels, reservoirs, irrigated areas, water supply priority, monthly volume of available water resources, crops, irrigation programs of all the irrigated areas and water loss of the reservoirs. The satisfaction degrees of irrigation water in all the irrigated areas were simulated. Satisfaction degree of irrigation water in the areas irrigated by both rivers and reservoirs was higher than that in the areas irrigated by rivers only. Shortage of irrigation was the most serious in November and March, and then in April and May in the mainstream area of the Tarim River Basin.

Key words: ecological water demand, irrigation water demand, satisfaction degree, WEAP model, mainstream of the Tarim River