潼关高程对渭河河床演变的影响

本文根据渭河下游河段自三门峡水库建库42年以来的大断面地形变化以及泥沙淤积资料，运用河床演变分析法，分析了潼关高程对渭河淤积演变的影响。分析发现，潼关高程的大幅度抬升和下降引起溯源发展的淤积和冲刷的行波，行波传播速度大约每年10km，传播过程中幅度逐步减弱。通过相关分析，发现潼关高程抬升是引起渭河下游特别是临潼以下河段淤积的主要原因，咸阳及其以上河段的淤积与潼关高程基本无关，渭河上游来水量对冲刷减淤起了很大作用，来沙系数影响略小。本文进一步建立了一种淤积平衡模型，用以模拟渭河下游淤积过程。模拟结果表明，模型能正确地模拟淤积过程，潼关高程抬升引起的渭河下游淤积有一个平衡淤积量。如果潼关高程维持在一定水平不变，渭河下游的淤积就会逐渐趋近于这个平衡淤积量，大约30年左右就会接近这个平衡。目前渭河下游累积淤积量已经接近潼关高程328.5m的平衡淤积量。如果潼关高程保持不变，渭河下游将随着来水量的波动而发生小幅度的冲刷和淤积，不会发生累积性的大幅度淤积。

Effect of Tongguan's elevation on the fluvial process of the lower Weihe River

The effect of Tongguan's elevation on the fluvial process of the lower Weihe River is studied in this paper. The rising and reduction of Tongguan's elevation cause retrogressive siltation and erosion, which propagate and attenuate upstreamward. The propagating speed of the retrogressive erosion and siltation is about 10km/year. Correlation analysis is performed for the sedimentation volume of the lower Weihe River with the rising of Tongguan's elevation, annual runoff and the ratio of the average sediment concentration over the average discharge(C=S/Q). The result indicates that the rising of Tongguan's elevation is the main cause of the sedimentation, but Tongguan's elevation exhibits no effect in the reaches upstream of Xianyang. The annual runoff of the river plays an important role in the scouring of the channel bed and the ratio C=S/Q shows less effect on the sedimentation. A model of sedimentation equilibrium is proposed in the paper. Calculation with the model agrees well with the data of sedimentation, which proved that there is indeed an equilibrium sedimentation volume for the lower Weihe River. If the rising of Tongguan's elevation maintains unchanged the sedimentation of the lower Weihe River may reach the equilibrium volume in 25-30 years. At present the sedimentation of the lower Weihe River approaches to the equilibrium volume.