Water shortage and its sustainable management are important issues in the Manas River basin. In this paper, the evaluation model has been developed based on entropy and projection pursuit theory, and then the sustainable level of water resources has been evaluated from water, social, economic and ecological environment systems. The result showed that the evaluation method is reliable and reasonable. As a new method for evaluating water resources, it can provide scientific basis for the sustainable use of water resources. The main conclusions are as follows:
(1) Considering the relative close characteristic of the river basin in arid inland, a comprehensive index system on evaluating sustainable use of water resources has been suggested in this paper. It includes 14 indexes and four subsystems about water resources condition, society, economy and ecological environment.
(2) By the coupled entropy and projection pursuit theory, we can have a greater understanding of the present state of sustainable use of water resources. The results showed that the utilization potential of water resources trends to increase. The utilization level was poor and the water resources potential was small in 2000. The sustainable level of water resources would get better with water saving irrigation practice and industry structural adjustment in 2010 and 2020.
(3) The water resources condition is the most important factor to affect water resources sustainable level in the basin. In order to accomplish the water resources sustainable use, some measures has been put forward as follows: a) paying more attention to the deep exploitation of water resources; b) reducing the agricultural water use and implementing water saving irrigation; c) developing water-efficient industry; d) increasing the ratio of micro-salty water in irrigation; e) and looking for new water resources. Through these measures, the gap between the supply and demand of water resources can be minimized, and also the water resources sustainable utilization level would be improved.