水沙条件与侵蚀基准面对河流水位的叠加效应——以渭河下游为例

为探究水沙条件与侵蚀基准面共同影响下的河道水位变化特征与机理,采用极值水位-极值流量和同流量下水位分析方法,研究了近70年来渭河下游的水位变化及其成因。根据三门峡水库三个运行模式,将水位时间序列(1950—2017)划分为4个阶段,即P1(1950—1959)、P2(1960—1973)、P3(1974—2002)和P4(2003—2017)。华县水位总体为上升趋势;咸阳水位在P1和P2阶段波动,P3和P4阶段则持续下降。侵蚀基准面抬高导致渭河下游河道大幅淤积,这是华县水位抬高的主要原因;咸阳水文站受侵蚀基准面影响较小,上游来沙大幅减少导致河床冲刷,加之近期河道综合整治,促使了其水位下降。渭河下游水位在未来可能延续下降趋势。研究成果对渭河下游及类似河流管理具有重要理论与实践意义。

Combined effects of water-sediment conditions and erosion base level on river stage: Case study of lower Weihe River

This paper presents an extreme stage-extreme discharge analysis and a specific-gauge analysis on the change in the lower Weihe River stage during the past 70 years to explore the characteristics and mechanism of river stage changes and their causes under the combined effects of water-sediment conditions and erosion base level. Considering the three operating modes of the Sanmenxia reservoir, we divide the time series (1950-2017) into periods of P1 (1950-1959), P2 (1960-1973), P3 (1974-2002), and P4 (2003-2017). The water stage was generally on the rise at Huaxian; it fluctuated at Xianyang in P1 and P2, while continuously decreased in P3 and P4. The rise in the erosion base level, represented by Tongguan elevation, caused a large-scale sedimentation in the lower Weihe and thus became the major cause for the Huaxian stage rising. The Xianyang hydrologic station was less affected by the base level. Its water stage downtrend was originated from riverbed scour caused by the drastic reduction in incoming sediment, and comprehensive management of river channels promoted this trend. By our predictions, the water stage in the lower Weihe may continue its downtrend in the future. The results help the management of the lower Weihe basin and other similar rivers.