三峡工程运行对洞庭湖水环境及富营养化风险影响评述

洞庭湖的江湖关系受自然因素及人为因素影响，其江湖关系的变化影响洞庭湖水文、水质、水环境容量和营养状态.近年来洞庭湖的富营养化指数不断升高，但水环境变化及富营养化风险变化的原因错综复杂，如何区分三峡工程运行等人类活动和气候变化等自然因素对洞庭湖水环境、富营养化风险的影响是洞庭湖江湖关系研究的难点.根据近年来洞庭湖江湖关系、水环境或富营养化水平的相关研究，对洞庭湖由于三峡工程运行导致的江湖关系变化，以及该变化对洞庭湖水环境、富营养化风险的影响的研究进展进行系统梳理、分析、总结和评述.现阶段研究得出，三峡工程运行导致的江湖关系变化影响洞庭湖不同时段的水环境容量，在一定程度上改善了枯水期和泄水期洞庭湖水质；三峡工程运行后洞庭湖水体中的ρ（TP）有所降低，但洞庭湖湖体ρ（TN）、ρ（TP）仍相对较高，已能够满足藻类生长的需求，水华发生的制约条件是水体透明度和水流流速；江湖关系变化后洞庭湖富营养化风险增大的时段是蓄水期，其他时段富营养化风险减小；流速较低的东洞庭湖湖滩区、蓄水期流速降低明显的南洞庭湖滩区水华发生的风险增大，为水华发生的敏感区域.大型枢纽工程对通江湖泊污染物迁移转化影响的机理分析、对通江湖泊水环境影响的模拟及相关参数研究、对湖泊水环境及富营养化风险的长期影响等方面的研究还有待进一步完善. 

Impacts of the Three Gorges Dam Operation on Water Environment and Eutrophication of Dongting Lake: A Review

River-lake interaction between the Dongting Lake and the Yangtze River has beensignificantly altered by physical factors and artificial factors, such as climate variability, rapid socio-economic development in Dongting Lake catchments, and operation of the Three Gorges Dam (TGD) in the upper Yangtze River. Altered river-lake interaction has great impacts on water environment of Dongting Lake. Water quality deterioration worsens the eutrophication of Dongting Lake recent decades. However, river-lake interaction and its associated mechanisms that give rise to potential impacts from the TGD are difficult to distinguish from interactions and impacts from the other factors. An improved understanding of the impacts of TGD operation on river-lake interaction, and impacts of altered river-lake interaction on water quality and eutrophication of Dongting Lake will provide significantly improved scientific bases to develop regulation strategies for the construction and operation of large hydraulic reservoirs. In this paper, these impacts was summarized and analyzed based on the conclusions of river-lake interaction, water quality and eutrophication trends of Dongting Lake in recent decades. The altered river-lake interaction impacted by TGD operation improved the water quality and increased the environmental capacity of Dongting Lake in dry season (from December to March) and pre-flood releasing (from April to May).After TDG operation water total phosphorus (TP) in Dongting Lake was decreased, however, the limiting conditions for algal bloom were water transparency and flow velocity. The risk of eutrophication in Dongting Lake increased during the TDG storage period, and decreased during other periods. During storage period, there were increased risks of eutrophication in easternand southern Dongting Lake with low flow velocity, which were the sensitive lake regions for algal bloom. Further studies should be focused on the mechanism of the impacts of large dam projects on pollutants transportation and transformation in a long sequence.