| City is the place where the population is concentrated, and it is the political, economic and cultural center of the surrounding areas. Water is the lifeline of the city and an important resource to maintain the health of ecosystems and sustainable development of the city. A long period of time, the development and utilization of urban water resources only emphasize the production and living water and don't pay attention to the water demand of ecological environment, which lead to the following eco-environmental problems: the city's rivers becoming sewage rivers, land subsidence caused by over-exploitation of groundwater, the artificial lakes, ponds shrinking and even dried up in the urban area. These issues seriously restrict the development of the city, influence the quality of the living environment of residents, and threaten the security of human life and property. The purpose of the study on urban eco-environmental water demand is to improve the urban ecological environment, to achieve harmony between man and nature as well as the sustainable development through maintaining a reasonable eco-environmental water demand and controlling the human activities within the extent permitted by water resources, water environment and aquatic ecosystems.In this paper, firstly some related concepts such as ecological water requirements, environmental water requirements, ecological use of water, environmental water and so on, are analyzed and summarized in a concept system of eco-environmental water demand. According to the space, time and man-made characteristics, the city's ecological environment water demand mainly refers to natural systems water demand, including greenbelt, lakes and groundwater water demand. Then, the urban eco-environmental water demand calculation methods are described, which include the two main urban greenbelt and lakes ecosystems. The calculations of greenbelt system consist of greenbelt vegetation and soil water demand. The calculations of rivers and lakes system consist of evaporation, water leakage and their own existence water demand. Secondly, the natural and social factors which impact the urban eco-environmental water requirements are analyzed. Then a reasonable classification of cities is done from the perspective of eco-environmental water requirements. The detailed calculations of index weights are showed. Then based on the built-up areas and other 15 indicators of Baoding City in 2006, the Baoding City belongs to a medium-sized city level.Then in the light of specific circumstances of Baoding city, the minimum eco-environmental water demand in 2005 is 1105.13×104m3 and the water demand of green space and rivers ecosystem is respectively 497.60×104m3 and607.53×104m3. Meanwhile the Greenbelt eco-environmental water demand in 2010 and in 2020 can be forecasted and the result is 727.24×104m3 and 1158.11×104m3. Finally, to meet the ecological environment water demand, some measures are brought forward, for instance water conservation, rainwater ecologically and water quality improvement and restoration of river body. With the further development of urbanization and the eco-city construction, urban eco-environmental water demand study will constantly be improved in theory and practiced more on a wide range of applications.
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