近30年来鄱阳湖湖盆地形演变特征与原因探析

利用鄱阳湖1980、1998和2010年3期湖盆水下地形数据,结合出、入湖泥沙输移数据以及流域水土流失、水库建设等资料,较为系统地研究鄱阳湖近30年来湖盆冲淤的时空变化特征及其影响因素.研究表明,1980-1998年,松门山以南主湖体位置淤积现象明显,平均淤高0.82 m,该淤积主要是由这一阶段内流域水土流失加剧所引起的;1998-2010年,在大规模植树造林和水库建设等人类活动影响下,鄱阳湖淤积现象减缓.但是在入江水道上湖盆高程显著下降,平均下降速率高达30.75 cm/a,这与入江水道处持续采砂和水流冲刷等因素有关;近30年来,"五河"入湖的洲滩区域冲淤变化及趋势有所差异,修水、抚河及赣江三角洲呈现逐渐降低的趋势,饶河入湖漫滩总体上以淤积为主,且地形坡度趋于变缓.研究结果对鄱阳湖水资源合理开发、水利工程建设及航运管理等均具有一定的实践和参考价值.

Bottom topography change patterns of the Lake Poyang and their influence mechanisms in recent 30 years

In this study, extensive investigation was done on the changes in bottom topography across the Lake Poyang through geographical information systems(GIS) techniques and comparison of underwater topography data of 1980, 1998 and 2010. Possible mechanisms behind the topographic changes were also discussed based on watershed hydrological data(e.g. sediment transport, soil erosion and reservoir construction). The results showed that (1) the main water body region was obviously deposited with an average deposition value of 0.82 m during 1980-1998. These alterations of bottom topography were frequently caused by the increased soil erosion in the upstream of the basin. (2) During 1998-2010, the deposition trend of the bottom topography among Lake Poyang was slowed down to some extent. This was probably caused by the afforestation and reservoir construction program. However, in this period, bottom topography in the channel entrance was decreased remarkably with the average declining rate of 30.75 cm/a. The increases in flow discharge and gravel extraction have been considered as the main causes of this topographic change in the region. (3) In recent 30 years, the changing trends of deposition/erosion among five rivers' alluvial cone were different. Bottom topography elevation in Xiushui, Fuhe and Ganjiang alluvial cone expressed gradually decreasing trend, while Raohe alluvial bay showed a rising tendency as a whole. The results of the study are of great theoretical and practical significance to water resources reasonable utilization, dam construction and shipping management across the Lake Poyang.