中文摘要：

山西省桑干河流域地处我国黄土高原干旱半干旱区，水资源开发利用与生态环境矛盾十分突出，同时水资源供需矛盾形势十分严峻。从水资源开发利用中的生态环境问题出发，指出生态环境需水量是地表水体维持特定的生态环境功能所必须蓄存和消耗的最小水量，在此概念基础之上，构建计算河流系统生态环境需水量的理论方法。以桑干河为例，分河流生态基流、水面蒸发量、入渗需水量、输沙需水量以及污染物自净需水量5部分，概算了桑干河河流系统的生态环境需水量。研究结果对提高水资源利用效率、改善生态环境有着重要的理论意义和实用价值。

英文摘要：

Sanggan River is located in the semi-arid area, where the contradiction between the development and entironment of water resources is terribly outstanding So is the contradiction between supplying water and demanding water. From the eco-enviromnental problems in water resources development an utilization, the authors point out that eeo-environmental water demand is the minimum water which must be reserved and consumed to maintain specific eco-environmental function by surface water body. On the basis of this concept, it lays the theoretical foundation for calculating river system eco-environmental water demand. With Sanggan River as an example, river fundamental eco-environmental demand, water surface evaporation demand, infiltration requirement, water for river sediment, and pollutants in water demand self-purification water demand are divided to assess regional river system eco-environmental water demand. The research provides a scientific basis for eco-environmental construction and exploitation and utilization of water resources.