2010年调水调沙期间黄河利津段对人造异重流的响应

RESPONSE OF WATER-SEDIMENT DISCHARGE OF HUANGHE(YELLOW RIVER)TO THE HYPERPYCNAL FLOW CAUSED BY WATER-SEDIMENT REGULATION IN 2010

黄河调水调沙期间是目前观测黄河口泥沙异重流的有利时机。黄河入海含沙量、粒度和流量是决定河口异重流产生和发育的基本条件。自2010年6月19日黄河第10次调水调沙启动,在利津站进行了同步取样及测深、测流观测,以掌握调水调沙期间黄河入海水沙特征变化,预测河口泥沙异重流发生时间。观测结果显示:在调水调沙初期上游水库联合低泥沙浓度放水情况下,流量急剧加大,河道底床被冲刷,大量底床粗颗粒泥沙再悬浮造成利津站水体含沙量和输沙量有所增加,粒度粗化;观测后期受小浪底水库排放的泥沙异重流影响,利津站流量迅速减少,含沙量和输沙量显著增加,且细颗粒泥沙含量明显增加,河道底床被淤积。此阶段黄河入海含沙量和悬沙粒度满足河口泥沙异重流产生条件,据此可以预测河口泥沙异重流产生的时间。同时,巨量细颗粒泥沙短时间内以泥沙异重流的形式输送入海,势必会在河口处引起快速的河口地貌地形变化和生物地球化学效应。

The water-sediment regulation provides a good opportuttity for the observation of the hyperpyc- nal flows at the Huanghe （Yellow River） estuary. The concentration （SSC） and median grain size of the suspended sediment are important factors to the formation of hyperpycnal flows. During the 10th water- sediment regulation on June 19th , 2010, in order to study the variations in water and sediment discharge off the Huanghe River mouth and to predict the formation of hyperypycnal flow, synchronous survey were carried out at the Lijin station, which includes the sampling of the suspended sediment and measurement of the bathymetry and current system. The results suggest that when the reservoirs on the upper reaches of the river started to release water with low suspended sediment concentration （SSC） on schedule, the water discharge recorded at the Lijin station increased sharply, together with the intensification of riverbed ero- sion. A great amount of the coarser particles were resuspended from the riverbed, resulting in the increase in suspended sediment concentration （SSC） and sediment load （SL） of the water, as the major contributor to the rise of suspended concentration of coarser sediment. In the later stage, under the influence of hyper- pycnal discharge off the Xiaolangdi Reservoir, the water discharge recorded at the Lijin station decreased quickly, while the SSC and SL remarkably increased off the Lijin station up to the river mouth. The re- markable increase in fine sediment concentration led to the heavy siltation on the riverbed. It was possible to predict the hyperpycnal process at the river mouth, since both high SSC and fine particles concentration are the necessary requirements for the formation of hyperpycnal flow. The hyperpycnal flow would not on- ly deliver a large amount of sediments from the river to the coastal sea in a short period, but also bring im- pact to the geomorphological and biogeochemical evolutions of the estuary.