| Hydro project brings lots of social and economic benefits such as flood control,power generation,irrigation,navigation and water supply.However,hydro project also alters the river hydrological processes and topography and changes the habitat conditions of aquatic life.Focusing on the influence of reservoir operation on large aquatic organism,the thesis simulates and analysis the habitat changes under different operating models through eco-hydrology and eco-hydraulic analysis.With Yangtze Finless Porpoise as the research subject,this thesis surveys and studies the habitat characteristics of the main stream of the Yangtze River,lakes linked to the main stream and semi-natural reserve of Yangtze Finless Porpoise,discusses the response relationship between the finless porpoise behaviors and the hydrological process,and also shows the influence of different operating models of the Three Gorges Project on finless porpoise habitat through numerical simulation.At last,the thesis discusses the feasibility of countermeasures to protect finless porpoise.The results of the thesis include:(1)Summary of the research results of Yangtze Finless Porpoise and existing problems.Based on literature research,the thesis summarizes the population size and behavior of Yangtze Finless Porpoise and the impact approach of water conservancy project.(2)Study of the response relationship between the finless porpoise behaviors and the hydrological process.Using one-dimensional model and two-dimensional model,the thesis studies the characteristics of typical habitat of Yangtze finless porpoise which are commonly featured with rich food,clean water,water depth between 2m-25m and high diversity of landscape,However,the topographic,hydrological and hydraulic features are only the necessary but insufficient conditions for Yangtze Finless Porpoise’s habitat.Food is the main factor for the finless porpoise to choose habitat.Because of the impact on downstream hydrological processes and sediment transport which affects the distribution of fish,hydro projects,in an indirect manner,influence the habitat selection of finless porpoise.(3)The thesis shows the impact of the Three Gorges Project on Yangtze Finless Porpoise habitat during the initial impoundment.Using numerical model,the thesis analysis the impact of Three Gorges on main stream of Yangtze River,lakes and Tian-e-zhou oxbow.The results are:The main branch of Luxikou braided channel keeps being scoured and left branch filled up;The exchanging time between Tian-e-zhou oxbow and main-stream of Yangtze River is shortened 5 days than before;The water levels in dry season of Dongting Lake and Poyang Lake are lower than before.From January to March,the water level of Dongting Lake basically is same as before.That influences the hydrological and hydraulic condition of finless porpoise.(4)The long term impact of the Three Gorges Project on Yangtze Finless Porpoise habitat is assessed.The situations of habitats continue deteriorate.The exchanging time between Tian-e-zhou and main-steam of Yangtze River is 24 days,shorted 65%than before.The habitat characteristics of main branch in Luxikou changes little;the habitat characteristics of left branch reduce largely.The water levels in day season of Dongting Lake and Poyang Lake are lower than before.(5)The connected program of Tian-e-zhou oxbow and Hei-wa-wu oxbow could execute water quantity exchanging and water quality improve with reasonable gate schedule.The left branch of Luxikou-braided channel will be filled up in dry season with less bio-diversity and even cutout.Engineering measures are needed in Luxikou branch to build ex-situ conservation for Yangtze Finless Porpoise. |
