Research On Eco-environmental Water Demand In Southern China

According to ecosystem service, character of the area including elastic strength of ecology, bio-diversity, water and soil conservation and resource environment, have been drawn as the index system aiming at the actual state of ecological environment of the area. Based on the natural structure of the ecosystem, the whole area is divided into two subsystems-river and land. River index system is different from land index system. Subsystem heath is appraised based on its index system. Two subsystem health results are synthesized into area ecosystem health. Because ecosystem is dissipative structure and character of ecosystem health grade is fuzzy, application of a multi-objective and multilevel fuzzy optimization model combined with entropy weight coefficient is assessed to the regional ecosystem health.According to the characteristic of the river ecosystem, the view that river hydrology change is the motive power of maintaining river ecosystem integrality is pointed out after having expatiated on a relation between river ecological environment and river hydrology change. It turned out to be that the hydrology change of the river is reflected through the change of the flow. Hydrological indexes based on ecological relevant factors in the flow-Quantity, time, frequency, lasting and rate of change are selected. The bigger the difference of indexes of hydrology is, the greater its impact on ecosystem is. Therefore, the method of descending dimension ascertain hydrology index which is limitative factor of river ecosystem. A new method of instream flow is put forward. The relation between the regional ecosystem health and composite index of hydrology has been studied to make certain the degree of hydrology change of river, which will offer the theoretical foundation for sustainable utilization of the water resource. The case in Guangdong Province has proved that the hydrology index method applied to instream flow is feasible.Wet perimeter method is the simplest way on the basis of survey data and suitable for the moist area. Shortcoming that 'inflection' point in wet perimeter method always determined subjectively by eye from a graph is analyzed. The subjectivity is overcome by defining the break in shape using mathematical techniques that was put forward by Gippel. The principle of instream flow based on wet perimeter method is put forward. The instream flow of probability distributionand space variability are studied. Principle component analysis and multiple regression analysis on principle components have been adopted in a runoff dataset to investigate the relation between runoff characteristic value and instream flow. After comparing the method of wet perimeter and hydrology index of instream flow with analysis, the result that hydrology index method is more beneficial than wet perimeter has been drawn.