重大水利工程运用对长江入海径流量的影响

Impact of large-scale water projects on the Yangtze River

采用长江大通水文站1950～2011年逐日平均流量资料，运用Pettitt突变点检验法对年、枯季、汛后平均流量序列进行突变点分析。用突变点对时段平均流量序列进行分段，采用M—K趋势性检验法分析各段及整体序列的变化趋势。结果表明，20世纪初，长江上游区域呈现降温、降水减少是造成年平均径流量缓慢下降的原因。20世纪80年代以来全球气候变暖，可能是导致1988～2011年的枯季平均径流量相对1950～1987年有明显的抬升、发生均值突变的原困之一；上游水库群在枯季对长江下游的径流补给加剧了枯季人海径流量上升趋势。汛后平均径流量在1990年和2003年都出现了突变点：1950～1990年问，显现出微弱的下降趋势；1990～2003年问虽然为上升趋势，但平均径流量明显低于前40a；2003～2011年期间转为较为明显的下降趋势，同时平均径流量也低于以往。从三峡工程蓄水运行时间来分析，2003年之后的汛后径流趋势转变可能与j峡工程运行有直接关系，但需要进一步的证实。

Based on daily-averaged discharges of Datong station at the Yangtze River, Pettitt change-point tests were employed to detect the change-points of discharge time series accounting for the duration of a year, dry season, flood season, flood recession period and each month, respectively. The discharge time series were divided into several segments by change-points. The tendency of discharges was explored by Mann-Kendall method. The results show that the temperature reduction and precipitation reduction in the upstream of the Yangtze River are the main reasons of the average discharge＇s slight decreasing. The global warm since 1980s may be one of the reasons why the average discharge of dry season during 1988 and 2011 is higher than the one during 1950 and 1987. The discharge replenishment of the reservoir groups in the upstream strengths the increasing trend of discharge into sea of dry season. The average discharge of flood recession period, whose change points of appear in 1990 and 2003, experiences a slight reduction from 1950 to 1990 before an increasing trend can be found until 2003. Between 2003 and 2011, the discharge experiences a significant decrease and is lower than before. According to the timetable of impoundment of the Three Gorges Project, the changes of the average discharge of flood recession period may be caused by the Three Gorges Project, but more evidences are needed.