1970年以来赣江流域水沙变化及归因分析

Water and Sediment Changes in the Ganjiang River Basin of China since 1970 and Its Attribution Analysis

水沙变化研究主要关注径流和产沙总量的变化,对水沙变化的过程要素如降雨、径流和产沙三者间关系的演变特性的研究相对不足。赣江为鄱阳湖流域的最大支流,其输入鄱阳湖的水量和沙量均占总量的60%以上。赣江水沙变化驱动分析,过去主要以定性评估为主,只有少数研究采用了基于定量的归因分析。本文收集了赣江流域1970—2015年期间的水沙变化数据;采用Mann-Kendall检验法进行水沙序列数据的趋势分析;基于带虚拟变量的回归方法确定降雨、径流和产沙间关系的变异;借鉴“水文法”的思路进行了水沙变化的归因分析。研究结果表明:(1)赣江流域降雨并无趋势变化,人类活动也并未导致降雨径流关系的变化,故径流在研究时段内基本保持不变;(2)人类活动显著改变了径流产沙关系,使得径流含沙量降低了约67%,导致流域产沙在1994年后锐减,减幅达65%;(3)人类活动导致1994年以后的产沙减少了71%,而降雨使产沙增加了7%。流域产沙的锐减可认为完全由人类活动所致,水库拦沙应是人类活动减沙的主要方式。对赣江水沙变化过程要素的定量研究有助于对水沙变化总量的理解,研究结果可为我国南方相似地区流域综合管理提供借鉴。

Investigation on fluvial sediment migration in response to climate change and engineered activities is a prerequisite for watershed managements. The research on water and sediment changes mainly focused on the change of runoff and sediment yield in a drainage basin, but less attention was paid to the evolution characteristics of the process factors of water and sediment change. Currently, the evolution characteristics of the relationship among rainfall, runoff and sediment production was neglected in water-sediment research. The Ganjiang River is the largest tributary in the Poyang Lake basin, and its water and sediment flowing into the Poyang Lake accounts for more than 60% of the total inflow of the Poyang valley. In this research, it studied the runoff and sediment transport of the Ganjiang River basin from 1970 to 2015. The changes in the runoff and sediment yields were detected by Mann-Kendall trend analysis, and the changes in the relationships between them were examined by regressions with dummy variables. Quantitative attribution analyses were conducted by ‘hydrology method’ which has been widely applied in the water-sediment research on the Yellow River basin of China. The results show that:(1) Rainfall have been no tendency change since 1970 in the Ganjiang River valley, and the runoff also remained invariant over the period, which suggests that intense human activities did not alter the rainfall-runoff relationship in the basin;(2) Other than the runoff, human activities greatly altered the sediment yield and sediment concentration, with a decrease by 67% in runoff. Noticeably, basin sediment yield had greatly reduced by 65% after 1994;(3) Human activities had decreased basin sediment yield by 71% after 1994, but rainfall increased the basin sediment yield by 7%. The sharp reduction in basin sediment yield can be totally attributed to human activities, among which the reservoir interceptions probably played a dominant role. Quantitative research on the water-sediment change process in the Ganjiang River is helpful to understand the total amount change of water-sediment in the basin, and results of this research have implications for integrated watershed management in other humid areas in southern China.