近50余年荆江三口水沙变化特征及驱动力分析

Characteristics of runoff and sediment discharge of Three Channels from Jingjiang River in 1956 through 2009

以荆江三口(松滋口、太平口和藕池口)入洞庭湖的代表性控制站1956-2009年长系列水文数据为基础,运用Mann-Kendall趋势突变检验、双累积曲线等方法探讨三口水沙变化特征并对其驱动力进行了分析。结果表明:近50余年来,松滋口、太平口和藕池口年径流量和年输沙量呈不断减少的趋势,以藕池口变化最为显著,其突变时间最早(1978年和1986年)。松滋口年径流量和年输沙量趋势性改变的时间分别为1980年和2003年;太平口年径流量趋势性改变的时间为1972年和1986年,年输沙量为1998年和2003年;藕池口年径流量趋势性改变的时间为1967年、1972年和1989年,年输沙量为1998年和2003年。年径流量和年输沙量趋势性改变是由于上游径流量的不断减少及诸多人为工程共同作用的结果,其中裁弯和三峡工程的影响最为明显。裁弯主要因大幅减少三口径流量而减少输沙量,三峡工程主要因直接减少悬浮泥沙浓度而减少输沙量。

Based on the hydrological data in 1956 through 2009 at representative gauging stations, the charac teristics of the runoff and sediment discharge of the Three Channels from the Jingjiang River are investigated, using MannKendall trend test and double mass analyses. The results show that the annual runoff and the an nual sediment load of the Three Channels decreased significantly during 1956 2009. Moreover, the time of the earliest abrupt change was in the Ouchi Channel （in 1978 and in 1986）, indicating which had the most serious changes. The time of tendency change of annual runoff and annual sediment load was in 1980 and in 2003 in the Songzi Channel, respectively; in 1972 and in 1986 for annual runoff, and in 1998 and in 2003 for annual sediment load in the Taiping Channel, and in 1967, in 1972 and in 1989 for annual runoff, and in 1998 and in 2003 for annual sediment load in the Ouchi Channel. The reduction of annual runoff and annual sediment load were mainly caused by the decrement of runoff from the upstream river and by commissioning of hydroprojects, especially the cutoffs in the Jingjiang River and the commissioning of the Three Gorges Project. The cutoffs were mainly through reducing the annual runoff to reduce the annual sediment load, while the Three Gorges Project is directly reducing the suspended sediment concentration.