水库运用对宁蒙河道水沙条件的影响

依据实测资料分析了龙羊峡、刘家峡2水库运用对宁蒙河道水沙条件的影响,结果表明:①两库调蓄运用改变了进出库站的径流年内分配,汛期水量占年水量的比例由建库前的60%降为40%左右;出库大流量历时缩短,小流量历时延长;非汛期出库流量普遍加大。②两库运用后,宁蒙河道汛期沙量占全年的比例由建库前的81%~87%降为78%~60%;头道拐汛期大于2000 m3/s流量级历时由年均32.3 d减少到2.4 d,占汛期历时的比例由26%减少到2%。③水库调蓄洪水使得对内蒙古河段支流汇入的高含沙水流的稀释作用减弱,加重了干支流汇合口局部河道的淤堵。

Influence of Reservoir Operation to the Silt Discharge Condition of Ning-Mong Section of the Yellow River

The paper analyzes the influence of the operation of Longyangxia and Liujiaxia reservoirs to the silt-discharge condition of Ning-Mong section through the observed data.The conclusions are as follows: a) the two-reservoir operation has changed the annual runoff distribution of inflow and outflow of the reservoir and the runoff proportion of the flood season reduced from 60% before the reservoir to about 40%;the duration of big outflow discharge has reduced and the duration of small discharge increased;the outflow discharge of non-flood season has generally increased.b) After putting into operation of the two reservoirs,the annual proportion of quantity of water in flood season of Ning-Mong section has reduced from 60% before the reservoir to about 40% and the annual proportion of sediment in flood season reduced from 81%-87% before the reservoir to 60%-78%;the duration of discharge greater than 2 000 m3/s in flood season has reduced from 32.3 d to 2.4 d of annual average.The duration proportion reduction of the flood season is from 26% to 2%.c) The reservoir storage and regulation have reduced the function of dilution of high sediment concentration flow of tributaries jointed at Inner Mongolia section,worsening the silt-up of local channel at the confluence of the main river and tributary.