CHANGES OF MAJOR ECOLOGICAL AND ENVIRONMENTAL ISSUES IN DONGTING LAKE REGION

With the evolution of sediment,hydrological regime and pollution,major environmental issues have gradually changed around Dongting Lake in recent decades.Especially under the impacts from the Three Gorges Project,returning farmland to lake project and the increasing of climate extremes,Dongting Lake is undergoing low water level occurrences.The water level dropped 2.03 and 2.11 m at the outlet of the lake in 2006 and 2009 respectively,caused by the water storage of Three Gorges Reservoir.The water quality has deteriorated from grade Ⅳ to grade Ⅴsince 2008.Low water level accelerated the change in wetland structure and the degradation in wetland function.Invasive plant has threatened the biodiversity and the stability of habitat.Due to continuous decrease in sediment discharge,Dongting Lake,for the first time,changed from trapping to supplying net sediment to the Yangtze River in 2006.The environmental conflict around Dongting Lake is changing from flood dominated to flood and drought coexisted.These environmental changes have reflected the social structure transformed from traditional agriculture to a comprehensive development in agriculture,forestry and industry,as well as changes in the lake-catchment interaction.