渭河干流下游造床流量与有效流量的时空变化特征

Spatial and Temporal Distribution of Dominant Discharge and Effective Discharge in the Lower Reaches of Weihe River

为研究渭河下游河流演变关键特征流量的变化特性,采用改进的马卡维也夫法与水沙频率组合法,计算并分析了咸阳、临潼与华县水文站的造床流量与有效流量的时空变化特征,探讨了造床流量、有效流量与平滩流量之间的关系。结果表明:年均流量在1934—2014年呈波动性下降趋势,含沙量在1980年前呈增加趋势,此后至2014年急剧下降;造床流量由1980—1989年之前的561~1586 m 3/s减小到之后的254~885 m 3/s;有效流量除了华县站在1930—1959年时段内急剧减小外,其他年份波动变化。在空间上,造床流量除了临潼站在1990—1999年大于下游华县站之外均呈现下游大于上游的特点;有效流量除了临潼站在1970—1979年小于上游咸阳站和在2000—2009年略大于下游华县站之外也呈现下游大于上游的特点,这与径流量的沿程增大密切相关。年均径流量、含沙量与输沙率对造床流量影响较大,而含沙量与输沙率对有效流量影响较小。在渭河下游,平滩流量最大,造床流量次之,有效流量最小,三者并不一致,采用平滩流量法计算渭河下游的造床流量是不合适的。

To understand the key discharges of river evolution in the lower reaches of Weihe River,the Makovieve method and frequency combination of water and sediment method were used to calculate the dominant discharge and effective discharge in Xianyang,Lintong and Huaxian stations.In addition,we discussed the relationship between the key discharges and bank-full discharge.Conclusions are as follows.In terms of time,from 1934 to 2014,the average annual runoff showed a wave decline,and the sediment concentration showed an increasing trend before 1980,and then dropped sharply in the period from 1980 to 2014.The dominant discharge decreased from 561~1586 m 3/s before the period 1980—1989 to 254~885 m 3/s after that period.The effective discharge fluctuated in other years except for the sharp decrease in Huaxian station during the period from 1930 to 1959.In terms of space,the dominant discharge showed the phenomenon that discharge of the downstream was larger than that of the upstream except that the discharge in Lintong station was larger than that of downstream in Huaxian station in 1990—1999.The effective discharge showed the phenomenon that the discharge of the downstream was larger than that of the upstream except that the discharge in Lintong station was smaller than that of the upstream of Xianyang station in 1990—1999 and was little larger than that of downstream of Huaxian station in 2000—2009,which was closely related with the increasing runoff along the river.The average annual runoff,sediment concentration and sediment transport rate had great influence on the dominant discharge,however,the sediment concentration and sediment transport rate had less influence on the effective discharge.In the lower reaches of Weihe River,the bank-full discharge was the largest,followed by the dominant discharge,and the effective discharge was the smallest,which was not consistent.Therefore,it is not appropriate to use the bank-full discharge method to calculate the dominant discharge in the lower reaches of Weihe River.