Study On Index System And AHP-Fuzzy Comprehensive Evaluation Model In River Health Assessment

Rivers provided human being with lots of ecological services. However, with the rapid increase of population and economy, health and ecological services deterioration of river ecosystem were becoming serious. As river degradation becoming the primary problem faced by the river ecosystem of countries all over the world, more attention has been paid to river restoration and sustainable river management. As a new tool to assist management of rivers, the river health has become the major focuses in the field of ecology and environment science.In this thesis the concept of river health was expatiated, and the assessment methods for river health were systemically studied. Based on the connotation of river's health and river's characteristics of study area from Shijiao to Sixianjiao reaches in downstream of Beijiang River, an index system for river health was established. It included an objective layer, a rule layer with 5 factors and an index layer with 20 defined indexes. The objective layer generalized to the river health highly, reflecting the total level of the healthy condition of river by the river health index (RHI). The rule layers, which consider the water resources, water environment, aquatic biology, river structure and riparian zone, reflected the river health attribute and level from different sides. The index layer included 20 qualitative and quantitative evaluation indicators. Furthermore, the five-grade assessment standard described as "very healthy, healthy, sub-healthy, disease and very disease" were established based on the analysis of river health concept and its connotation.The detailed description for steps of using the method of analytic hierarchy process to confirm indicator weight was provided in this thesis. Judging by objective layer, the most important factor in the rule layers was the water environment, which weight was 0.371. And the most important indicator in the index layers was the water quality, which weight was 0.247. Then a model of AHP-fuzzy comprehensive evaluation model was designed to carry out the assessment. Taking the area at Shijiao-Sixianjiao reaches in downstream of Beijiang River as a case, based on the index system and fuzzy comprehensive evaluation model established in this thesis, the situation of river health of the studied area was evaluated to reveal its health grades and disadvantages, it make the theory and method gain practical test. The assessment results showed that the situation of river health in the. studied was healthy. However, the sub-healthy accounted for 21.76%.Therefore, it was necessary to adjust and control the situation of river health, and the appropriate measures and suggestion were recommended.The research on the index system for evaluating the health of the river at downstream of Beijiang River was the basic work to provide decision-making base for rivers protection, maintenance and restoration, and it will provide reference to the evaluation work of the health of the Pearl River Basin and to the water resources management, rational development and utilization, the effective and scientific protection in the future. The evaluation index system has been studied in this thesis to pave the path for the further improvement of the system. The research results were of great theoretical and practical significance.