三峡水库1956—2017年坝下径流特征分析

采用三峡水库坝下宜昌水文站1956—2017年日径流监测数据和长江上游80个国家气象站年均降水量长系列资料,利用一元线性分析法、滑动平均法、线性趋势回归法、非参数统计检验法、Mann-Kendall秩次相关、累积距平法和滑动T检验法分析三峡工程运行前后坝下径流的变化特征,其成果可为三峡工程调度提供参考。结果表明:三峡水库坝下宜昌水文站径流量变化趋势具有显著阶段性。三峡水库蓄水运行前宜昌水文站径流量和上游降水量相关性超过90%,该时期径流量主要受上游天然来水影响。三峡水库运行后,径流量主要受人类活动影响。宜昌水文站径流年际变化减少趋势不显著,长江上游降水量呈显著减少趋势。坝下径流量和上游降水量在2002年发生了突变且变化趋势相同,但径流量减少趋势不显著。径流年内分布发生了一定变化,其中汛期径流量占年径流总量百分比从72%下降到66%,枯期径流量占年径流量总量百分比从11%增加到15%。三峡工程调蓄是人类活动的直接表现,枯期宜昌水文站径流量增大是三峡工程生态效益的具体体现。

Runoff Characteristics in the Downstream of the Three Gorges Reservoir Dam from 1956 to 2017

The daily runoff monitoring data from 1956 to 2017 at the Yichang hydrological station in the downstream of the Three Gorges Dam and the long time series of annually-averaged precipitation data over 80 national meteorological stations in the upper reaches of the Yangtze River were used to analyze and test the runoff variation characteristics before and after the operation of the Three Gorges Dam by the method of linear regression analysis,moving average method,linear trend regression method,nonparametric statistical tests,Mann-Kendall rank correlation,cumulative anomaly and moving T-test.The results can provide reference for the Three Gorges project dispatching.The results show that the runoff variation trend under the dam has significantly different phases.Before the impoundment operation of the Three Gorges Reservoir,the correlation coefficient between the runoff at the Yichang hydrological station and the upstream precipitation was over 90%.The runoff during this period was mainly affected by the upstream natural water.In contrast,after the operation of the Three Gorges Reservoir,the runoff was mainly affected by human activities.The interannual variation of the runoff at Yichang hydrological station showed no significant decrease trend,while the precipitation in the upper reaches of the Yangtze River showed a significant decrease trend.The runoff and the upper precipitation changed suddenly in 2002 and the trend of changes were the same,but the trend of runoff reduction was not significant.There was a certain change in distribution of runoff during a year.The percentage of annually averaged runoff decreased from 72%to 66%in the flood season,but increased from 11%to 15%in the dry period.The storage and regulation of the Three Gorges Reservoir is a direct manifestation of human activities.The increasing runoff at the Yichang Hydrological Station during the dry period is a concrete embodiment of the ecological benefits of the Three Gorges Project.