A Study On The Ecological Health Assessment Of Dawen River

River is the cradle of human civilization.With the development of industrial civilization, a great deal of wasted water is let out into rivers and the water resources are in short supply. At the same time, the ecological health of river is becoming worse and worse. As river degradation has become the primary problem faced by the river ecosystem of all countries, more and more attention has been paid to the assessment of river health and river ecological restoration. Based on the previous studies, the thesis tries to establish a river ecological health assessment index system and apply it to the ecological health assessment of Dawen River. The data in the study is collected both directly by doing much fieldwork and indirectly from some concerning departments. The methodology adopted in the thesis is the combination of qualitative approach and quantitative approach.The whole thesis consists of six parts.The first part is the introduction to the thesis. It mainly discusses the background, objectives and significances of the study, and the pattern and techniques involved in the study.The second part is devoted to the concept of ecosystem health, the concept of river ecosystem, and the structure and functions of river ecosystem. Besides, it also reviews the development of the studies on river ecological health and its assessment methods both at home and abroad.In the third part, the author firstly summarizes the relevant theories on river ecological health assessment in and out of China. Then in combination with the present situation of river degradation and ecological environment in China, the author establishes a river ecological health assessment index system by defining three assessment objectives and four assessment principles. The index system is composed of 5 sub-indices which include the riverside banding, hydrology, river environment, river biology and social economic situation along the river, and 23 indicators. This system also has a five-level assessment grade. By comparing different river ecological health assessment methods, the author decides to adopt the fuzzy synthetical assessment method. In addition, in this part, the author also improves membership function and creates the corresponding assessment matrix.In the fourth part, firstly, the author presents the geographical, social and economic conditions of Dawen River, its ecological situation and its problems; then, based on the index system created in the third part and related national standards, the author puts forward the Dawen River ecological health assessment standard; thirdly, after deciding the weightiness of different index which is conducted by studying the marks given by the experts and by using the improved analytical method, the author employs the fuzzy synthetical assessment method. to assesses the ecological health of Dawen River; finally, the author draws the conclusion that the ecological health of Dawen River belongs to submorbidity, and its biggest degree of membership is 0.3858. According to the manximam membership principle, the ecological health of Dawen River is on the lower edge of submorbidity. Dawen River is in urgent need of harnessing and ecological restoration.The fifth part introduces the concept of ecological restoration and sets the ecological restoration goals in accordance with assessment results. It also proposes some measures to restore ecological health of Dawen River from a macro angle and further puts forward a practical and feasible project which includes reducing pollution and planting more native vegetation.In the sixth part, the author sums up the main points of the thesis and points out the limitations of the study.