城市生态环境需水量研究--理论与方法

生态环境需水量是一个整合的新概念。从降水量概念和水资源量概念两个角度界定了城市生态环境需水量的概念与内涵 ,分析其类型和属性特征 ,建立了城市生态环境需水量的方法体系 ,包括城市分类的指标体系与方法、基于降水量概念和水资源量概念的城市生态环境需水量计算方法与等级划分方案 ,为城市生态环境需水量研究提供理论依据与方法支持

Study on urban eco-environmental water requirements: theory and method

Water resources are of great importance in maintaining urban sustainable development. With a rapid increase of population and economy, urbanization leads to the scarcity of urban water resources and other challenges on urban eco-environment, such as degradation of greenbelt, shrink of rivers and lakes, water pollution, descent of groundwater level, etc. The problems were due not only to that the relationship between water resources and eco-environment has been ignored for a long time, but also to that the amounts of eco-environmental water use are not fulfilled. With the improvement of understanding of eco-environmental water use, eco-environmental water requirements (EEWR) gradually play an essential role in water resources allocation. EEWR, a newly emerged concept, refers to the water resources that should be allocated to eco-environment to maintain healthy ecosystem or eco-environmental quality. Urban eco-environmental water requirements (UEEWR), meaning the water requirements of urban natural ecosystem, include two implications when applied to different aspects. On the one hand, it means the water resources present in water cycle of ecosystem. On the other hand, it refers to the water resources consumed during the process of transpiration, evaporation, leakage, etc. UEEWR includes the water requirements for urban greenbelt, rivers, lakes and wetlands. According to the eco-environmental functions, UEEWRs can be divided into different categories. It is an integration of water quality and quantity, with temporal and spatial characteristics. On the basis of the theory system of UEEWR, the methodology of UEEWR is built up as follows. (1) Urban classification is the basis of study on UEEWR. A total of five kinds of elements are selected to build up the indicator system of urban classification. They are weather and climate, conditions of water resources and eco-environment, urban functions and characteristics, and urban size. At the same time, an integrated assessment model based on fuzzy sets is used in urban classification. (2) Based on the concepts of precipitation and water resources, calculation approaches of UEEWR are put forward, respectively. They include the formulas of (a) vegetation water requirements, (b) soil water requirements, (c) ecological base flow in river channels, (d) water requirements of lake maintenance, (e) water requirements of water surface evaporation, (f) water requirements of leakage and (g) water requirements of exchange in lakes. (3) According to the characteristics of different categories of UEEWR, a total of six indicators are chosen to create a grade system. These indicators are (a) ratios of actual to potential evaporations, (b) ratios of actual soil moisture to field capacity of soil moisture, (c) ratios of runoff transection areas to river transection areas, (d) ratios of actual water surface areas to lake areas, (e) depth of rivers and lakes, (f) water renewal period of lakes. Finally, the following five grades are set up for all categories of UEEWR: minimum, small, medium, excellent, maximum.