An Assessment Of Ecosystem Health For Dongting Lake And Its Restoration

The Dongting Lake is one of the classic complex lakes in the world, which 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. Dongting Lake plays a critical role in the environment and economy of the Hunan Province and the entire Yangtze River water system. Its functions include transportion, aquatic production and environmental improvement as well as a flood barrier for the Jing River region and the mid and downstream region of the Yangtze River. But, with the development of society and economy, under the duble function, human and nature, Dongting Lake came forth many eco-environmental problems such as atrophy, eco-environmental deterioration, and so on. It has became the confinement factors to the development of society and economy.The whole paper is consist of four master parts, and the detailed contents of the parts are as follow:Firstly, the paper analysed the tipicile ecological and environmentla problems of the Dongting Lake, it try to describe and briefly analysed the major environmental issues of the Dongting Lake region, which included escalating water pollution, rising eutrophycation, decrease of biological diversification, severe flood disaster, silt stagnation, shrink of the water body,soil erotion and schistosomiasis, and so on.Secondly, based on the concept and goal of ecosystem health, the paper compared all sorts of methords chosed a indicator species to assessed the Dongting Lake ecosystem health which are consisted of external indicators, environmental indicators and ecological indictors.Thirdly, based on the monitoring data from 2000 to 2006 of Dongting Lake, the water environment quality is analyzed considering the indicates such as TN,TP,COD,Chla,metals ,and so on. The paper also assessed the Nemerow water quality index and the eutrophication of the different parts of Dongting Lake.According to the phytoplankton , zooplankton and zoobenthos'biomass, we attempt to apply esergy (Ex) , structural esergy (Exst), trophic state index (TSI), and diversity (DI) to the assessment of the Dongting Lake ecosystem health. The result reveal the Dongting Lake ecosystem is falling into a steady , eutrophication and illhealth state.And the last, we introduced the theory of eological recovery and restoration, bring forward the suggestions to recovery the Dongting Lake ecosystem. Combined with the dredging engineering, the changes in CODMn capacity, TN capacity and TP capacity of Dongting Lake before and after dredging were simulated based on the analysis of the Dongting Lake actuality water environmental quality in the paper, and the reasons were also analyzed. It was found that dredging engineering enhanced the water environmental capacity of Dongting Lake. Especially in the lower water and higher flux, the water environmental capacity increased more. Under the same source of explicit pollution, the dredging was helpful for improving the water quality of Dongting Lake, and it could ameliorate the eutrophic state of Dongting Lake in a certain extent.