Ecological water demand in the typical polder of Dongting Lake

Dongting Lake is the largest lake in the middle reaches of the Yangtze River in China. After the completion of the Three Gorges Project, the relationship between the Yangtze River and Dongting Lake has a significant change with the decreased diversion ratio. Besides, due to the overexploitation of local human activities, some dry-up reaches appeared in the Dongting Lake region, especially in the polders with high strength  human activities. In order to scientifically understand the evolution law of water resources in those protective embankments in lakeside areas, and understand the relationship between human activities and ecosystem stability, the study works on the ecological water demand that coupled with the ecological capacity of the environment. As a typical polder, the Yule polder is selected as a case study in the Dongting Lake region. The objective is to obtain the ecological water demand process which can maintain the requirements of water quantity and quality of water to maintain water ecological needs under the condition of significant human impacts. Based on the actual situation of vegetation coverage, aquatic organism growth status and protection goals, and water demand of the industrial and agricultural population, taking the satisfaction degree of ecological water demand as an indicator, healthy of local water ecology is to be evaluated. Combining the hydrological situation of entire Yangtze River basin, the temporal distribution characteristics of ecological water demand in the Yule polder is analyzed, and also the feasibility of measures such as diverting Yangtze River water to alleviate the fragility of water ecology in the Dongting Lake region is discussed. These results could provide experience for solving similar problems in other regions.