基于Copula函数的头道拐水沙关系频率分析研究

Discussion on Runoff⁃Sediment Relationship and Frequency of Toudaoguai Hydrologic Station Based on Copula Function

为了掌握黄河中游水沙关系的变化特点和变化趋势,基于黄河头道拐站1958—1990年33 a和1998—2017年20 a的水沙资料,通过P-Ⅲ型曲线分别建立年径流量与年输沙量的频率曲线,对年径流量和年输沙量进行丰平枯划分;基于Copula函数对水沙关系进行变异诊断,构建年径流量-年输沙量联合分布模型并通过拟合优度检验选取最合适的Copula函数,计算水沙丰平枯组合遭遇频率。结果表明:头道拐水文站在1958—1990年和1998—2017年的年径流量和年输沙量呈下降趋势,1990年水沙关系发生变异;1958—1990年水沙关系存在一个变异点(1965年),1998—2017年水沙关系不存在明显的变异点,整体水沙关系存在一定的平稳性;1966—1990年和1998—2017年两个时期的水沙丰平枯组合遭遇频率中丰枯同频高于丰枯异频,1966—1990年的年径流量和年输沙量在较大值处相关性较强,1998—2017年年径流量和年输沙量整体相关性较强,水量和沙量的丰平枯变化趋势基本一致。

In order to grasp the characteristics and trends of the relationship between runoff and sediment at the upper and middle reaches of the Yellow River,based on the water and sediment volume data of the Yellow River Toudaoguai Station in the 33 years from 1958 to 1990 and the past 20 years from 1998 to 2017,the P-Ⅲcurve was adopted to establish the runoff and sediment discharge frequency and divide annual runoff and annual sediment transport into hight,medium and low flow.It carried out mutation diagnosis of runoff and sediment relationship,and joint distribution model of annual runoff and annual sediment transport was constructed based on copula function by the goodness of fit test.Finally,it calculated the encounter frequency of wet⁃normal⁃dry runoff and sediment combination.The results show that the annual runoff and sediment discharge of Toudaoguai Hydrological Station in 1958-1990 and 1998-2017 show a downward trend and the relationship be⁃tween runoff and sediment is remarkable especially after 1990;There is a variation point(1965)in the relationship between water and sedi⁃ment during 1958-1990.There is no obvious variability point in the water and sediment relationship between 1998 and 2017 and there is a certain stability in the overall runoff and sediment relationship;the synchronous frequency in the frequency of the combination of wet⁃normal⁃dry runoff and sediment is greater than that the asynchronous frequency during 1966-1990 and 1998-2017,the annual runoff and annual sediment transport in the previous period have a strong correlation at the annual sediment load is larger.The correlation between annual runoff and annual sediment transport in the latter period is stronger and the variation trend of annual runoff volume has similar variation tendency to the annual sediment.