Research On River Ecological & Environmental Modeling Based On Instream Flow Incremental Methodology

River ecological and environmental modeling is currently a hot research area. In particular, eco-environmental water demand and ecological restoration are two important research topics in the area and have attracted extensive research overseas. Both qualitative methods such as 7Q10 and Montana, and quantitative methods such as habitat methods have been developed for determining the eco-environmental water requirement. In developed countries, researchers attach great importance to natural river restoration, applying methods that involve less hard engineering work. In China, we are beginning to explore river ecological and environmental modeling. Studies on eco-environmental water demands largely focus on concepts and simplistic calculation methods. Our achievements in the area of river channel ecological restoration are limited.Based on a thorough assessment of exiting methods, the dissertation concluded that it is of great theoretical and applied significance to research the Instream Flow Incremental Methodology (IFIM). IFIM is used to determine the eco-environmental water requirement based on the physical habitat simulation (PHABSIM). PHABSIM takes endangered or precious fishes as index species. It quantifies the relationship between the weighted useable area for the fishes (WUA) and the river discharge. The method not only assists in protecting endangered and precious aquatic species, but also provides scientific guidance on the allocation of water resources, resolving the conflicts among industrial, domestic and ecological water demands. In the area of ecological restoration, one of the aims is to recover the variety of aquatic species and to create more habitats for endangered or precious species. IFIM can evaluate the results of river channel ecological restoration programs and optimize the design of these programs.The dissertation discussed the theoretical connotation of eco-environmental water demands and ecological restoration, and studied the theory of IFIM in detail. IFIM is a theoretical system, consisted of many modules. The method takes representative species as index species. It models hydraulics factors, habitat suitable indices and water quality elements (including water temperature). The water quality model is one-dimensional in the existing system. However, the pollutant concentration field is often two-dimensional. For example, the water temperature resulted from effluent from coal-burning and/or nuclear power plants would need two-dimensional numerical modeling. The dissertation developed a two-dimensional water quality mathematical model to simulate the temperature field and concentration field influenced by a point source using the finite difference method. This model provideda hydraulic and water quality basis for analyzing the habitat. Finally, the thesis obtained a quantitative relationship between Chinese Sturgeon reproductive habitat and the discharge. Optimal designs of the branch and egg structure for ecological restoration were also examined using River₂D software.River ecological and environmental modeling concerns ecology and environment. Although the EFIM method links both areas and has been widely applied overseas, it still has problems that need to be addressed. In terms of ecology, the relationship between species population dynamics and discharge, as well as the food chain and discharge, need to be addressed further. In the environmental area, the influence of sediment transport on aquatic species is yet to be investigated further.