水是生命之源、生态之基、生产之要，是生态系统中的关键环境要素，也是影响生态系统健康的重要因子。水位是反映湖泊生态状况的重要指标，将水位维持在合理区间，是维护湖泊生态系统结构与功能的基本要求，也是湖泊发挥应有生态服务功能的根本保障。作为长江中游两大通江湖泊之一，洞庭湖在水资源调蓄、生物多样性保护、污染物消纳等方面发挥着极其重要的作用。但是，随着江湖关系的改变，洞庭湖枯水期水位下降，湖盆加速萎缩，由此引发了一系列生态环境问题。东洞庭湖是洞庭湖水系中面积和湖容最大的湖盆，也是国家级自然保护区和国际重要湿地，其发挥的生态服务功能尤为重要，面临的问题也尤为突出。因此，在东洞庭湖开展生态水位研究，探索维护湖泊生态服务功能的有效途径，对开展长江流域湖泊生态系统保护具有重要意义。 本文研究了生态水位的概念和属性，突出水位的生态过程特征，提出了湖泊动态生态水位的概念，即满足不同生态保护目标要求的水位区间在时间轴上形成的序列值。分析了东洞庭湖自然地理、水文情势、湿地鸟类、水生生物、水质及主要水污染物负荷特征，识别出东洞庭湖主要生态服务功能及其生态保护目标和敏感期。采用决策树分类法对2003～2016年共322景有效MODIS遥感影像进行解译分类，得到16天合成的东洞庭湖水体、草滩、泥滩和芦苇湿地面积。结合东洞庭湖各水文站实测水文数据，建立了东洞庭湖水位—面积—湖容曲线以及水均衡模型。梳理明确越冬候鸟栖息地维护、长江江豚栖息地维护以及污染物消纳3种生态服务功能及其保护目标与各类湿地面积、湖泊水位的逻辑关系，建立数值模型，计算得到满足3种生态服务功能及保护目标的生态水位及其适用条件。以时间为轴线，对3种生态水位及防洪警戒水位进行有机融合，得到基于多目标的东洞庭湖动态生态水位。对比实测水位数据和相关研究成果，分析了动态生态水位的保证率以及与相关研究成果的协调性，提出东洞庭湖在生态水位保护方面存在的问题和建议。 主要成果： (一)依托时间序列遥感影像和水文数据，建立东洞庭湖水位—面积—湖容曲线。东洞庭湖水位—面积曲线为S=4.4306×Z²-165.11×Z+1653.3(S为东洞庭湖水体面积，Z为岳阳水文站水位，下同)：水位—湖容曲线为V=1.4769×Z³-82.555×Z²+1653.3×Z(V为东洞庭湖调蓄湖容)。 (二)计算满足3种生态服务功能及其保护目标的东洞庭湖生态水位及适用条件。越冬候鸟栖息地维护生态水位：20.52～23.46m，适用条件：敏感期11～2月、罗纹鸭(越冬候鸟代表物种)种群数量4300～15732只。长江江豚栖息地维护生态水位：19.10～24.00m，适用条件：敏感期2～3月、种群数量110～150头、种群密度0.89头／㎞²。污染物消纳生态水位：21.00～28.00m，适用条件：氨氮浓度不高于0.98㎎／L、入湖流量小于14000m³／s。 (三)融合得到满足越冬候鸟栖息地维护、长江江豚栖息地维护、污染物消纳、洪水调蓄等多目标的东洞庭湖动态生态水位。1月生态水位为20.52(21.00)～23.46m，2月生态水位为20.52(21.00)～24.00m，3月生态水位为19.10(21.00)～28.00m，4～5月生态水位为21.00～28.00m，6～9月生态水位为21.00～32.5m，10月生态水位为21.00～28.00m， 11～12月生态水位为20.52(21.00)～23.46m。其中，括号内的数值为水文或水质较差条件下(氨氮浓度≥0.95㎎／L或流量≤14000m³／s)的最小生态水位。 关键词：生态水位，东洞庭湖，越冬候鸟，长江江豚，栖息地维护，污染物消纳

 Water is the source of life, the core of ecosystem, the basis of production, and the key factor influencing the environment as well as the ecological health. Water level is one of the most important indicators of lakes' ecological condition. Maintaining the water level in a reasonable range is a basic requirement for keeping the structure and function of ecosystem, and a fundamental guarantee for lakes to give out its ecosystem services. Therefore, with the changing of relationship between the Yangtze River and relevant lakes, stage of the Dongting Lake was decreasing in low water period, the lake basin was shrinking, resulting in a series of ecological problems. As a lake basin with the largest area and capacity in the Dongting Lake, as well as a national natural reserve and an international key wetland, the East Dongting Lake plays an extremely important role in ecosystem service. On the other hand, the East Dongting Lake is also facing prominent ecological problems. Therefore, it is meaningful to guide and promote the protection of the Yangtze River ecosystem by studying on ecological water level and ecological health in the East Dongting Lake. Based on the analysis of characters of ecological water level, conception of lake's dynamic ecological water level was firstly proposed, which is the changing water level within timeline that would guarantee multiple ecosystem services in different gradations annually. By analyzing the features of geography, hydrology, migratory birds, aquatic mammals, water quality and main water pollutants, this thesis identified the main ecosystem services and sensitive periods of the East Dongting Lake. 322 MODIS images of the East Dongting Lake obtained in the period of 2003～2016 were interpreted using decision tree classification method. Moreover, each image was classified into 4 types of wetland: water, grassland, mudbank and reed community. A model of relationship among water level, water area and lake capacity was established using observed data in the terms of water area and water level in time series. In order to maintain the habitat of migratory birds and aquatic mammals as well as capacity of pollutant absorption, logical relationships between ecosystem services and water level were analyzed, and calculating methods of ecological water level in the East Dongting Lake was explored. Then, different ecological water levels for different ecosystem services were achieved, as well as their application conditions. According to the timeline, dynamic ecological water level in the East Dongting Lake was obtained by using a fusion method. Guaranteed degree of dynamic ecological water level and coordination with related research results was analyzed by contrasting with measured water level and these research results. Finally, problems from ecological water level and suggestions were promoted. Conclusions are as follows: 1)The relationship between water level and area in the East Dongting Lake could be expressed as S=4.4306×Z²-165.11×Z+1653.3. S means area of the lake, Z means water level monitored by the Yueyang station. The relationship between water level and capacity could be expressed as V=1.4769×Z³-82.555×Z²+1653.3×Z. V means the capacity of the East Dongting Lake. 2)The ecological water levels for these services are as follows: ecological water level for migratory bird habitat protection is 20.52～23.46m, ecological water level for aquatic mammal habitat protection is 19.10～24.00m, and ecological water level for pollutant absorption is 21.00～28.00m.The application conditions of these 3 ecological water levels were analyzed. 3)By analyzing main ecosystem services in different periods, data fusion of different ecological water levels for ecosystem services was conducted, and dynamic ecological water level based on timeline in the East Dongting Lake was gained. Jan.: 20.52(21,00)～23.46m, Feb.: 20.52(21.00)～24.00m, Mar.: 19.10(21,00)～28.00m, Apr.～May.: 21,00～28.00m, Jun.～Sep.: 21.00～32.5m,Oct.: 21.00～28.00m, Nov.～Dec.: 20.52(21,00)～23.46m. The values in brackets mean lowest ecological water levels applicable in poor hydrological and environmental conditions. KEY WORDS : Ecological water level, the East Dongting Lake, migratory bird, Neophocaena asiaeorientalis, Habitat protection, Pollutant absorption