Abstract: According to the available water resources and the predicting water consumption in different developing stages of Heihe River Basin,the water resources capacity of this basin has been caculated.After the second stage of water development and utilization,the available water resources for agriculture irrigation should has some increase besides it firstly meet the need of population,environment and industry of middle reaches area in the coming 50 years.Water resources should not be the limiting factor to social-economic development,by which oasis and agriculture may develope sustainably.But in the Zhangyi basin on eastern Heihe branch,the available water resources for agriculture irrigation in the first 20 years of the next century will has deficit due to water-saving index.As long as the water-saving index is to be finished by 60% in the first 20 years,the fast development of social economics in the second 20 years ought to has ensurance of water resources.

Key words: Heihe River Basin, water resources, capacity