三峡水库运行后洞庭湖水沙变化及影响因素

水库建设改变江湖关系，影响下游水沙情势，进而对流域状况、人类生活和社会发展产生影响。本文根据2003—2019年洞庭湖三口、四水及长江水沙数据，运用Mann-Kendall趋势检验、滑动平均值等方法分析洞庭湖水沙变化趋势，并用Mann-Kendall突变分析方法对有显著变化的站点进行突变分析。结果表明，2003—2019年，荆江三口各水文站年输沙量、弥陀寺站与康家岗站年径流量有显著变化且具有突变点，荆江三口其余各站年径流量及四水各站水沙无显著变化。其中弥陀寺年径流量和年输沙量变化的突变点分别位于2014年和2010年，其余存在显著变化的各站年输沙量突变点皆位于2008年前后。长江干流来水来沙是影响洞庭湖水沙的重要因素，受2008年三峡水库开始175 m试验性蓄水影响明显，采砂活动等因素也可能与洞庭湖湖区冲淤情况存在关联。

Variations in flow and sediment in Dongting Lake and its influencing factors after operation of Three Gorges dam

Reservoir construction modifies the relationship between rivers and lakes and affects the downstream flow and sediment conditions, thereby impacting the river basin, human life, and social development. Using the 2003-2019 data series of runoff and sediment discharge in the Dongting region, variation trends in flow and sediment are analyzed using Mann-Kendall trend test and slip averaging, focusing on their abrupt changes through Mann-Kendall mutation analysis. The results show that for this period, significant variations with abrupt change points are noticeable in the annual sediment discharges at Dongting Three Entrances and the annual runoffs at the hydrological stations of Mituosi and Kangjiagang, while no significant variation can be detected in the annual runoff at the Entrances’ other stations or in the annual runoff or sediment discharge in the Dongting Four Tributaries. The abrupt change points of flow and sediment at Mituosi were in 2014 and 2010 respectively, while the rest were around 2008. The incoming flow and sediment from the Yangtze mainstream, which had been obviously affected by the 2008 test impoundment to 175 m of the Three Gorges dam, was an important factor of the variations in Dongting’s water and sediment. And sand mining and other factors were also possibly related to the scour and deposition in this lake.