三门峽水库淤积末端位置确定和预估的地貌学方法

本文主要用地貌学的方法来研究三门峡水库淤积上延的问题。运用河床沉积物法和纵剖面抛物线法,确定了渭河下游淤积末端的位置在渭汗21-22断面附近,并作了综合性预估;实践证明,在目前水库运用方式下不会影响西安。用同样的方法还确定了北洛河的淤积末端在洛淤17-18断面附近,北干流的末端在黄淤59断面附近,这与水利部门用断面法、同流量水位和体积法所得的结论基本一致。由于洛淤17-18断面和北干流黄淤59断面附近正处于纵剖面的坡折,所以淤积末端再继续上延比较困难。

GEOMORPHOLOGICAL APPROACH TO THE DETERMINATION AND PREDICTION OF THE POSITION OF SEDIMENTATION END OF SAN-MEN-XIA RESERVOIR

Variables affecting the upstream extension of sedimentation in the reservoir are rather complicated. Generally, it is controlled by the rising of the base level immediately above the dam, the gradient of the original channel, the variation of the discharge and the sediment coming into the reservoir and the operation of the reservoir, in addition to the above variables, the upstream extension of sedimentation in San-Men-Xia Reservoir is due to its particular geographic conditions. San-Men-Xia Reservoir is situated at the confluence of the Yellow River, Luo He River and wei River, with Tqng-Guan as its natural narrow gap.After the construction of San-Men-Xia Reservoir, the river bed at Tong-Guan has been raised by 4-5M, which acts as a local base level for the main river and the tributaries above it.As the river bed is raised due to the sedimentation and the backwater of the Yellow River is increased, a sand bar is formed at the mouth of Wei-He River, causing the backwate in the channel to rise and the backward sedimentation from the lower part to the upper part to take place in the lower Wei-He River,Bei-Lao-He River and the Northern Trunk of the Yellow River.This paper primarily deals with the upstream extension of sedimentation in San-Men-Xia Reservoir by using geomorphological approach. Using the river sediment method and parabolic longitudinal profile method, it has been determined that the sedimentation end in the lower wei-He River is located near the Wei Yu 21-22 cross-sections,and a comprehensive prediction has been made.It has been proved that the backward sedimentation will not involve Xi-An in the present operating mode of the reservoir.lt has been determined in the same way that the sedimentation end in the Bei Lai He River is near Luo Yu 17-18 cross-sections and the sedimentation end in the Northern Trunk of the Yellow River is near Huang Yu 59 cross-section.This conclusion coincides with that drawn by water conservancy organizations using the cross-section method, method of water table under the same dischargs and volume method, since the the wei Yu 21-22 cross-sections, Luo Yu 17-18 cross-section and Huang Yu 59 cross-section in the Northern trunk are situated at the break of their longitudinal profile respectively, further upstream extension of the sedimentation end will be difficult.