The Research On Assessment, Prediction And Restoration Of Dongting Lake Ecosystem Based On Health Theory

Dongting Lake receives the water from the four rivers: the Xiang River, the Zi River, the Yuan River and the Li River, and also exchanges water with the Yangtze River. It is an inland lake with the function of adjusting and storing. However, with the development of society and economy, under the double function, human and nature, Dongting Lake came forth many eco-environmental problems such as atrophy, eco-environmental deterioration, and so on. It has become the confinement factor to the development of society and economy.In order to safeguard the overall situation of flood safety and construct a healthy Dongting Lake, and also to protect the safety of the environment and support sustainable economic and social development in the Dongting Lake ecosystem, health evaluation prediction and restore technology for a new large-scale management of the provision of policy guidance and technical support is very necessary and urgent. Several techniques in following different aspects: current Situation assessment, trend prediction and ecological restoration of Dongting Lake ecosystem are investigated in this dissertation. The main contributions of this dissertation are described as follows.1. Dongting Lake ecosystem health status assessmentHealth Dongting Lake was defined as health in 3 functions: Yangtze River flood redistribution and storage functions; balance ecosystem; support sustainable economic and social development. Then build assessment index system and model of Health Dongting Lake. Dongting lake ecosystem health was assessed. The results indicate that Dongting Lake ecosystem is in poor health.2. Dongting Lake health forecastingThe development of the national economy, changes in the industrial structure and the implementation of the Three Gorges Project will impact the Dongting Lake, thereby affecting the health status of the Dongting Lake. The paper predicts the health status of the Dongting Lake:(1) A GA based eutrophication model was presentd to predict eutrophication state of Dongting Lake. The results indicate that: the eutrophication was going from bad to worse.(2) By calculated amount of external and ecological water needed, water deficit (P90%) was gained. The results indicate that: with the economic growth, water deficit (P90%) will increase, and health degree of water supply will be worse.(3) The Three Gorges Reservoir can improve the capability of Yangtze River in control flood, but it can't greatly change the health degree of Dongting Lake in Yangtze River flood redistribution and storage.(4) The seasonal operation of the Three Gorges Reservoir can control flood, then decrease probability of flood destroy dyke. So decreases communicate probability of snail fever.3. Ecological risk assessment of Dongting LakeAccording to the present generally accepted ecological risk assessment process: risk source analysis, receptor analysis, exposure analysis, hazard analysis and risk assessment, we carried out a pilot study for Dongting Lake ecological risk assessment. Then, we presented using toxicity pollution index to quantify the hazard which outside man-made pollutions did to ecosystem, in the first time. Using this method, combined with ecological index, ecological fragility index and natural disaster index, we assessed ecological risk of Dongting Lake ecosystem. By analysis and assessment, it was considered that the ecological risk of flood is highest; the next is pollutions, especially of phosphorus. These two risk sources could not be neglected.4. Dongting Lake ecosystem restoration and reconstructionA series of reconstruction measures were proposed considering the three functional requirements of Dongting Lake. That is not a way out of advanced individual measures, but a comprehensive way. Dongting Lake is the comprehensive organism, the individual control measures can not achieve the goal.We need individual measures to optimize portfolio and spend the smallest price to reconstruct Dongting Lake to the healthy state. Based on this, we present a multi-objective decision-making model framework of comprehensive reconstruct of healthy Dongting Lake; we can use the optimized results of the model to offer support means for decision-making of comprehensive reconstruction.5. The impact analysis of dredging project to Dongting Lake ecosystemFirstly, based on computed results of SSARR hydrological model, using SMS hydraulics model simulated the flood water level variation before and after the dredging. The effects of dredging were visualized by GIS techniques. Then by solving de Saint-Venant system of equations, we gained a stage-discharge relation equation. By this equation, we using Shiguishan monitoring station of the Li River as small targets simulated the stage-discharge tend before and after dredging. Secondly, the benefits of the water environmental remediation caused by dredging, was predicted. The results indicate that dredging has benefits of the water environmental remediation.