Study On Theory And Process Of Ecological Water Requirement Of River Basin

The river basin is a complete natural geographic unit and also is a unique human geography unit. Defining and studying EWR(ecological water requirement) from the watershed perspective can put forward more specific requirements for the rational allocation of water resources. On the basis of summing up the results of previous studies, the paper study the EWR in-depth, and Zhangweinan Canal was chosen as the ease study area.On the basis of summing up the results of previous studies, this paper study the ecological water requirement in-depth, and Zhangweinan Canal was chosen as the ease study area.First, the mechanism of EWR of river basin was investigated based on the fundamental theories, the definition of EWR was perfected and the study system of EWR was established. Second, according to environment conditions and the EWR characteristics of Zhangweinan Canal, the study system and method suitable for this basin was established. The EWR of Zhangweinan Canal basin were calculated and integrated, and the process of EWR was analyzed. Last, The paper put forward reasonable proposals for water resource management of river basin. The main results are as follows,1. EWR of river basin is defined as that a certain quality and quantity of water is needed for the ecological system of river basin to maintain a certain structure, function and ecological processes in a certain time and space conditions. This definition reflects the spatial and temporal variability, threshold, quantity and quality of unity, dynamic and targeted characteristics of EWR.2. EWR system of river basin is established on two levels of ecosystem types and ecological environment functions. Basin as a module is divided into aquatic ecosystem and dry land ecosystem, and turn to the three modules. Then functional EWR types are given to meet the environmental functions.3. EWR of Zhangweinan Canal basin is divided into EWR of aquatic ecosystem and EWR of dry land ecosystem in order to maintain the status of ecological environment. The former includes rivers, lakes and reservoirs, and the environment function set method is used. The latter includes forest, grassland and farmland, and the calculation method is direct approach based on GIS.4. The range of yearly EWR in Zhangweinan Canal is68.52to19.803billion m3. Aquatic ecosystem is26.09-2.682billion m3accounting for25.54%to26.26%of multi-year average of total water resources in watershed. Dry land ecosystem is42.43to17.121billion m3, but part of the EWR in dry land does not take up the available water resources.5. EWR of Zhangweinan Canal basin shows significant features in time and space. In one year, the amounts of EWR of total and aquatic are more in flood season than in dry season, and the EWR of dry land ecosystem is mainly EWR during the growing season. In space, the order of EWR is Zhangwei River plain area> Zhangwei River mountain area> downstream plain area.6. Aaccording to research results, some suggestions about water resources management are put forward in Zhangweinan Canal Basin. On the one hand, in different months, the different water distribution program should be formulated according to the variation of EWR. It must be ensure that the coordination of the flood season and non-flood season. The water of flood season should be full used as the diversion of river outside, and the water of non-flood season should be ensure, on the other hand, the allocation of ecological water in space should be coordination to follow the spatial variation of EWR of river basin.