防止河道断流的最小生态环境需水量

桑干河流域属于干旱半干旱区，降水量少，水土流失严重，生态环境十分脆弱。由于水资源短缺，水资源开发利用与生态环境矛盾十分突出，造成城市用水和工业用水挤占农业用水，农业用水又挤占生态用水的格局，引起自然植被退化、河流断流、河床淤积、地下水大面积超采等一系列生态环境问题。本文以桑干河流域为研究对象，以生态环境需水量理论为基础，提出了河道在保证不断流临界状态下河流最小环境需水量的计算方法，即为防止河道断流的最小生态需水量。

Lowest eco-environmental water demand to prevent the river blanking

As Sanggan river basin is located in arid and semi-arid land,there are many characteristics of nature,such as little rainfall precipitation,serious soil erosion and so on,so the ecological environment is very fragile.Because of water resources shortage,contradiction between economic development and utilization of water resources and ecological environment has become very sharp,which incluces the urban water and water for industrial takes up the agricultural water,and the agricultural water takes up the water available for ecology,causing a series of ecological environment issues such as natural vegetation degradate,river blanking,riverbed deposit and groundwater exceeding adopting by a large scale.Based on the theory of eco-environmental water demand,the calculation methods of minimum eco-environmental water demand are proposed.