昕水河流域“水文法”基准期降水输沙相关关系统计方法研究

Exploration on statistical methods for analyzing correlations between rainfall and sediment discharge in base period by hydrologic method in the Xinshui River Basin,Shanxi Province of northern China

【目的】基于昕水河流域日尺度降雨和输沙数据,分析1958−2015年昕水河流域降水与输沙变化趋势及相关关系,比较年降雨量、汛期降雨量、侵蚀性降雨量、轻度产沙降雨量、中度产沙降雨量、强度产沙降雨量等6种统计标准和降水空间分布对“水文法”基准期分析降水输沙相关关系的影响,筛选最佳的降水输沙相关关系统计方法,提高“水文法”的计算精度。【方法】利用Mann-Kendall非参数检验方法分析降水量与输沙量变化趋势,双累积曲线法判定“水文法”基准期,Pearson相关分析法比较水沙关系相关性结果。【结果】昕水河流域年降水量无显著变化趋势,年输沙量呈显著下降趋势;6种统计标准下的水沙关系相关性由高至低依次为:强度产沙降雨量、年降雨量、侵蚀性降雨量、中度产沙降雨量、轻度产沙降雨量、汛期降雨量;低降雨强度但高降雨量降雨事件对研究区产沙贡献小,剔除产沙无效降雨能提高水沙关系相关性;午城、黄土、蒲县雨量站水沙关系相关性较好,大宁、桑峨雨量站水沙关系相关性较差。【结论】昕水河流域年输沙量变化与三北防护林及淤地坝建设等地表人类活动变化直接相关;研究区的产沙主要发生在夏秋季的强降雨事件中,强度产沙降雨量用于降水输沙相关关系研究结果最优,汛期降雨量不适用于降水输沙相关关系研究,产沙无效降雨会增加水沙关系研究的偏差,在缺乏降雨强度准确数据时,应选择降雨历时短、降雨量大的产沙有效降雨进行水沙关系分析;在流域尺度,降水空间分布对降水输沙相关关系有影响,距流域出口站距离较近雨量站降水数据的水沙相关关系较好。

[Objective]This paper analyzes the trend and relationship between rainfall and sediment discharge in the Xinshui River Basin in Shanxi Province of northern China from 1958 to 2015 based on the daily rainfall and sediment discharge data,aiming to select the best statistical method according to the effects of rainfall spatial distribution and six statistical criteria of rainfall on calculating the relationship between rainfall and sediment discharge used for the“hydrologic method”in base period.The six statistical criteria of rainfall included the annual rainfall,the flood season rainfall,the erosion rainfall,the mild sand-producing rainfall,the moderate sand-producing rainfall and the heavy sand-producing rainfall.[Method]Mann-Kendall method was selected to analyze the trend of rainfall and sediment discharge,double mass curve was applied to determine the base period of“hydrologic method”,and Pearson correlation analysis was used to compare the results of correlation between rainfall and sediment discharge.[Result]There was no significant changing trend of annual rainfall in Xinshui River Basin,but the annual sediment yield showed a significant decreasing trend.The Pearson correlation coefficients between rainfall and sediment yield under the six statistical standards were ordered from high to low as follows:the heavy sand-producing rainfall,annual rainfall,the erosion rainfall,the moderate sand-producing rainfall,the mild sand-producing rainfall and flood season rainfall.The contribution of rainfall with low intensity but high amount on sediment was small.The correlation coefficient between rainfall and sediment yield can be enhanced by eliminating the invalid rainfall for sediment.The correlation coefficients between rainfall and sediment discharge of Wucheng,Huangtu,and Puxian rainfall stations were higher,and the results of Daning,Sang’e rainfall stations were lower.[Conclusion]The change of annual sediment yield is directly related to the human activities such as the Three North Protection Forest Project and the construction of check dams.Sediment discharge is mainly caused by heavy rainstorm in summer and autumn.The heavy sand-producing rainfall can be used to analyze the relationship between rainfall and sediment discharge,and the flood season rainfall is not suitable for the analysis of the relationship between rainfall and sediment discharge.Invalid rainfall for sediment will increase the deviation of the correlation coefficient between rainfall and sediment discharge.Rainfall with short time duration and high amount should be selected to analyze the correlation coefficient between rainfall and sediment discharge when rainfall intensity data are scarce.The relationship between rainfall and sediment discharge is influenced by the spatial distribution of rainfall stations at the watershed scale.