黄河干流头道拐河段凌汛期小流量过程变化及其影响因素研究

A study of low discharge process and impacting factors of Toudaoguai Reach in Inner Mongolia of the Yellow River during ice flood period

黄河干流内蒙古段河道冬季流凌封河期,河道水量除一部分转化为冰量外,很大一部分转化为槽蓄水量而贮存在河道中,导致下游头道拐河段出现小流量过程,上游河道流量转化为槽蓄水量和贮存的冰量越大,小流量持续时间越长,开河期发生凌汛洪水风险越高。通过对1998-2016年头道拐站凌讯期流量变化过程分析,重新界定了小流量上限阈值为330m3·s-1,并且以此值为标准进行小流量过程研究,分别采用R/S极差分析法、Fourier变换分析法对近年来小流量过程变化特征进行分析;结合非线性概率Logit模型和Probit模型对小流量过程的影响因素进行讨论。结果表明:小流量持续天数变化呈现缩短趋势;同时,小流量过程与上游相对来水之间变化关系显著且过程同步,而滞后于河道槽蓄水量变化过程;通过Logit模型和Probit模型分析各影响因素变化时相应小流量持续时间变化的响应概率大小,明确河道冰流量是小流量过程第一影响因素,气温条件是小流量过程的决定因素,首封位置和相对来水量是小流量过程重要影响因素。

During icing period,with the exception to freezing,large amount of water from the section of the Yellow River in Inner Mongolia is converted into channel storage. This will lead to a long low discharge process at Toudaoguai Hydrology Station. Longer low discharge process will lead to ice flood during the break-up period. The critical low discharge value,330 m3·s-1,was defined after analyzing the changing process and characteristics of Toudaoguai Hydrology Station discharge from1998 to2016. Based on this value,analysis of low discharge process was conducted using R/S range analysis method,Fourier transformation method and multiple linear regression analysis. The Logit and Probit nonlinear probabilistic models were used to discuss factors of low discharge process at the same time. The result showed that the number of low discharge days was decreasing,and there was a significant impact relation between low discharge process and change in upstream relative discharge. The low discharge process synchronized with change in upstream relative discharge,but lagged behind the change in channel storage. By using Logit and Probit models to analyze the response probability of duration of low discharge changing with each influence factors,ice discharge was a primary influence factor of low discharge process. The temperature and condition of the freeze-up site,as well as the relative coming discharge,were the main factors also.