黄河下游排沙特性及其对径流需求量的分析

Characteristics of Sediment Outflow and Analysis of the Runoff Needed by Sediment Outflow in the Lower Yellow River

通过黄河下游特征水沙年及三门峡水库不同方式运行期间泥沙输入与输出的分析、排沙能力对水沙条件依赖关系的分析 ,论述了黄河下游排沙特性 ,并对黄河排沙的径流需求量作了探讨。为黄河流域可持续发展工程建设 ,如南水北调供水规划、建立黄河流域水资源配置体系 。

The main points of this paper are as follows: 1. The lower Yellow River is a known aggrading river, in which about three\|quarters of the oncoming sediment were exported, and the rest was deposited on the channel since 1950. On the other hand, it is a river with grading tendency, which has a strong self\|adjusting function. So the degradation almost arises every year and the degradation stage usually occurs in Mar., Apr. and from Sept. to Oct. 2. For exception the period 1960～1973, that is early in putting the Sanmenxia reservior into operation, the sediment quantity of inflow or outflow of flood period accounted for over 85% of the annual total in the lower Yellow River since 1950. And the intensity of sediment outflow is generally small during the degradation. Therefore it is very important for decreasing channel deposition to seize flood opportunity to release sediment. 3. After aggradation over a period of years, the lower Yellow River presented the degradation for a few years running such as 1983～1984 with plentiful runoff. It is an incarnation of self\|adjusting behaviour of the aggrading river for tending to balance with longer temporal scale. 4. The analogue of process of sediment outflow on the Lijin station, the reach of the Yellow River mouth, manifested that annual runoff being equal, the difference of annual sediment outflow may be in excess of 100 percent due to difference of runoff process. So it is necessary for the channel tending to steady state to use reservir artificial flood peak to release sediment. 5. The annual sediment outflow of the lower Yellow River depends on both annual runoff and sediment load and their processes, on both tendency and strength of channel self\|adjustment. For example, the runoff needed by releasing per ton of sediment was only 20m 3 in 1959, owing to rich on\|coming sedimnet and concentration of runoff process in this year. And the corresponding runoff was over 110 m 3 in 1987, owing to poor on\|coming flow and sediment. As to 1965, the first year after the operational mode of the Sanmenxia reservior just changed from storing water and retaining sediment to storing clear water and releasing the muddy, the runoff needed by releasing per ton of sediment amounted to 88 m 3, owing to serious depositon of river channel. On the average the runoff needed by releasing per ton of sediment was about 36 m 3 in the 1950's. 6. The analogue of process of runoff\|sediment outflow indicated: If western line project of water deversion from the Yangtze River into the Yellow River is accomplished, the annual runoff of the Yellow River flowing into sea may be over 500×10 8m 3 and the channel of its lower reach due to heavy scour will change from the suspended river to a normal one.