乐昌峡水利枢纽年径流变化特征及趋势分析

Analysis on Annual Runoff Characteristics and Trends of Lechangxia Hydro-junction Project

为优化乐昌峡水利枢纽调度工作,利用变差系数、径流水文频率、Spearman秩次相关检验、Mann-Kendall趋势检验方法对坝址处年径流变化特征和长期趋势性开展相关分析,结果表明,枢纽建库前后不同长度序列的水文年径流特征变化不大;年径流大小分级可利用水文频率划分为丰水(含特丰)、偏丰、平水、偏枯、枯水(含特枯)等5个等级;在1958—2022年年径流序列中,特枯年均发生在20世纪60年代,特丰年均发生在1997年之后,2004年后连续18 a未发生过枯水年;坝址处1958—2022年逐年径流长期趋势不显著,但是构造6 a以上滑动平均新的序列有长期上升的趋势;利用Mann-Kendall突变检验发现6 a滑动平均新序列在1972年标签处开始发生突变。

Analyzing the annual runoff variation characteristics and long-term trends at the dam site of the Lechangxia hydro-junction project plays an important role in ensuring reservoir operation.The present study applied the coefficient of variation,runoff frequency,Spearman rank correlation test,and Mann Kendall test methods to analyze the annual runoff variation characteristics and long-term trends.Research shows that,there is few change in the hydrological annual runoff characteristics of different length sequences before and after the construction of the reservoir;annual runoff can be divided into five levels:wet year(including extraordinary wet year),slightly wet year,normal-flow year,slightly low-flow year,and low-flow year(including extraordinary low-flow year);in the annual runoff sequence from 1958 to 2022,the extraordinary low-flow years all occurred in the 1960s,the extraordinary wet years all occurred after 1997,and there have been no low-flow years after 2004;the long-term trend of annual runoff year by year from 1958 to 2022 is not significant,but there is a long-term increasing trend in constructing a new sequence of 6-year or more moving averages;the 6-year moving average at the 1972 label had abrupt changes by using the Mann Kendall mutation test method.