鄱阳湖洪泛系统水位-面积迟滞关系的形成机制及演变

Formation Mechanism and Evolution of Stage-area Hysteretic Relationships in Floodplain System of Poyang Lake

鄱阳湖是连接长江的吞吐型湖泊,洪泛特征明显,湖泊水位和淹没面积的季节变化和空间差异悬殊,表现出高度的非线性特征。基于2000~2018年鄱阳湖区多源遥感数据和实测湖泊水位数据,采用ESTARFM (Enhanced Spatial and Temporal Adaptire Reflectance Fusion Model)融合模型重构高时空分辨率淹水数据的方法,研究分析了鄱阳湖水位-面积迟滞关系形成机制与演变规律。结果表明:鄱阳湖水位-面积迟滞关系空间差异显著,同时存在逆时针和顺时针两种迟滞形式,其形成机制主要归因于湖泊上、下游表现出的河、湖相洪泛特征以及汇、排水过程的差异;鄱阳湖洪泛区广泛存在的碟形湖对增大鄱阳湖区上游站点迟滞度,减小下游迟滞度具有重要影响;近年来,受区域气候变化、湖区采砂活动以及三峡工程建成运行等造成的湖泊本身泄流能力和流域来水变化的影响,鄱阳湖区不同站点的水位-面积迟滞关系发生了显著变化。三峡工程多阶段实验性蓄水前后,以湖口、星子和都昌站为代表的北部湖区水位-面积关系迟滞度在2000~2003、2004~2009和2010~2018年分别呈现出先增大后减小的过程,而棠荫和康山站为代表的南部湖区则呈现出先减小后增大的过程。研究结果对于深化通江湖泊洪泛系统水文复杂性的认识、促进湖泊生态系统的管理实践具有重要的科学意义。

Poyang Lake is a typical alternately filled lake that connects to the Yangtze River.Flooding characteristics of the lake are obvious with lake water level and inundation area vary significantly in season and space,showing highly nonlinearity.Based on the observed water levels and reconstructed high spatial-temporal resolution inundation dataset of the Poyang Lake according to multi-source remote sensing data from 2000 to 2018 by adopting the ESTARFM model(Enhanced Spatial and Temporal Adaptive reflection fusion model),this study explored the formation mechanism and evolution of stage-area hysteretic relationships in the lake.The results show that the hysteresis of stage-area varied significantly across the lake.Both clockwise and counterclockwise hysteretic functions can be observed in the Poyang Lake.The formation mechanism of the two hysteretic functions is mainly attributes to the different flooding characteristics of river and lake facies and the differences of converge and drainage processes in the upstream and downstream of Poyang Lake-floodplain system.Duchang station in the middle of the lake shows the smallest stage-area hysteresis across the whole Poyang Lake,while the Kangshan station at the southernmost of the lake shows the largest stage-area hysteresis.Seasonal lakes that widely exist in the floodplain settings of Poyang Lake have important impact on increasing the hysteresis of upstream stations and reducing the hysteresis of downstream stations in the lake.In recent years,the stage-area hysteresis of different stations in the Poyang Lake have changed significantly due to the alteration of the lake outflow capacity and catchment inflow caused by regional climate change,sand mining activities in the lake and the operation of Three Gorges Project.Before and after the multi-stage experimental impoundment of the Three Gorges project,the hysteresis of stage-area in the northern Lake area represented by Hukou,Xingzi and Duchang stations experienced a process of first increasing and then decreasing during the periods of 2000-2003,2004-2009 and 2010-2018,respectively,while opposite process was observed in the southern lake area represented by Tangyin and Kangshan stations.