近70年长江干流寸滩站以上流域水沙关系变化及其驱动因素

以长江干流寸滩水文站以上流域为研究对象,基于1953-2018年的实测水沙资料,采用线性回归、Mann-Kendall趋势检验和水沙关系曲线分析径流、输沙的时间趋势及其关系变化,并采用双累积曲线法分析水沙变化的驱动因素。结果表明:寸滩站以上流域多年平均径流量为3425亿m^3,多年平均输沙量为3.61亿t;多年平均月径流量为294.8亿m^3,多年平均月输沙量为3013万t,且主要分布在6-10月,分别占年径流泥沙总量的70%和95%以上。趋势分析显示,流域年降雨量和径流量变化趋势不明显,年输沙量呈极显著减小趋势;月径流量在1-4月显著增加,其他月份变化不显著,而各月输沙量均呈显著减少趋势。水沙关系曲线均可用幂函数拟合,拟合参数受时间尺度影响,统计检验显示悬移质输沙量实测值与水沙关系曲线的估算值差异不显著。双累积曲线分析发现水利工程建设和水土保持等人类活动是寸滩水文站输沙减少的主要原因,其作用占69%~93%,其中2000年以来人类活动的贡献超过90%。

Variation of Water-Sediment Relationship and the Driving Factors Above the Cuntan Station of the Yangtze River Main Stream in Recent 70 Years

Based on the measured runoff and sediment data of Cuntan hydrologic station that at upper situating Yangtze River’s main stream,this study analyzed the temporal trends of runoff and sediment transport as well as the variations of their relationships during 1953-2018 by statistical methods including linear regression,Mann-Kendall test,and sediment rating curve.Double mass curve was further used to analyze the driving factors of water and sediment variation.The results showed that the average annual water and sediment discharge of Cuntan station was 342.5 billion m^3 and 361 million tons,respectively.The average monthly water and sediment discharge was 29.48 billion m^3 and 30.13 million tons,respectively,which mainly distributed in June to October,accounting for more than 70%and 95%of the total annual runoff and sediment,respectively.The trend analysis indicated that the variation trends of annual precipitation and runoff were not obvious,however,annual sediment discharge showed a significantly decreasing trend.The monthly runoff increased significantly from January to April and the changes in other months were not significant,while the monthly sediment discharge showed a significantly decreasing trend in each month.In this study,the relationships between water and sediment could be fitted by power functios,and the fitting parameters were affected by the time scale.Statistical test detected that there was no significant difference between the measured value suspended sediment load and the estimated values by sediment rating curve.Double mass curve analysis found that human activities,such as water conservancy construction and soil and water conservation,were the main factors driving the sediment reduction in Cuntan station,accounting for 69%~93%in different decades,among which human activities had contributed more than 90%since 2000.