近60a来洞庭湖水位演变特征及其影响因素

基于1956-2015年洞庭湖主要控制站实测水文数据，运用Mann-Kendall检验法、主成分分析法对比分析了近60 a来洞庭湖东、南、西三个湖区水位演变特征及其影响因素。结果表明：从调弦口堵口至葛洲坝截流后，南咀和城陵矶站同流量下水位均升高，但南咀站平均水位受三口分流能力减弱而下降（0.03 m），城陵矶站平均水位受湖盆泥沙淤积和长江干流顶托作用而上升（1.33 m）；三峡水库运行后，湖盆冲淤基本持平，湖泊同流量下水位基本不变，由于该时段长江流域整体为相对枯水期，因而与葛洲坝截流后相比湖泊年平均水位下降约0.31~0.58 m。近60 a来南咀站平均水位呈显著下降趋势（p<0.05），而城陵矶站水位呈显著上升趋势（p<0.01），说明湖泊水位影响因素作用存在空间异质性。洞庭湖年内水位存在涨（4-5月）~丰（6-9月）~退（10-11月）~枯（12月-次年3月）的变化特征，葛洲坝运行期丰水期水位上涨明显，三峡运行期各月水位均有下降，受水库调度方式影响7-10月水位降幅最大。洞庭湖流域降水量、四水入湖和出湖径流大小以及长江干流水情是洞庭湖水位变化的主要影响因素，三口来沙变异条件下的洞庭湖冲淤量变化是湖泊水位变化的次要因素。

Dynamics of water level of Lake Dongting during the past 60 years and the associated driving factors

The associated driving factors for the variations of the water level of Lake Dongting were investigated based on observed hydrological series from 1956 to 2015 for the major gauging stations in the Lake Dongting watershed. Our results indicated that:(1) After the curving cut-off of the lower Jingjiang River and the closure of the mainriver at Gezhouba, the contribution percentages of the discharge of Three Outlets to the total inflow discharge to Lake Dongting decreased, resulting in a decreased water level of Lake Dongting at Nanzui. The increase of draining capability of the lower Jingjiang River, together with the increased sediment deposition in Lake Dongting, resulted in increased water levels at Chenglingji. After the operation of the Three Gorges Reservoir (TGR), rainfall in the lake watershed decreased notably and sediment erosion rate overrode that of deposition rate, water levels in Lake Dongting drop 0.31~0.58 meters compared with that during the period after the closure of the main river at Gezhouba. (2) Water level in Nanzui during the past 60 years decreased significantly (p<0.05), while water level at Chenglingji station showed a significant increasing trend (p<0.05), indicating driving factors of water level have different impacts on different lake regions. (3) Water level of Lake Dongting rose in April-May, remained in high level in June-September, decreased in October-November, and remained in low level in December-March. During the period after the closure of the mainriver at Gezhouba, water level of Lake Dongting during flood period rose notably, and decreased during the post-TGR period, and this is especially pronounced during July-October owe to flood-storage dispatch of TGR. (4) The rainfall in the lake Dongting watershed, the runoff of the four rivers into Lake Dongting, and the discharge of Yangtze River have been the main driving forces of the water level variations of Lake Dongting during the past 60 years. The suspended sediment deposition rate in Dongting Lake basin, resulting from the runoff and sediment discharge of the Three Outlet, is a secondary factor of the long-term variations of water level of Lake Dongting.