近40年来长江流域水沙变化趋势及可能影响因素探讨

利用Mann Kendall方法，分析了近40年长江流域主要水文站点（长江干流水文站：屏山站、宜昌站、汉口站与大通站；支流水文站：嘉陵江的北碚站和汉江的皇庄站）的流量及输沙率的变化特征。结果表明：①长江流域流量与输沙量变化受人类活动（土地利用、水利设施建设等）与自然因素（如降水的时空变化）综合因素影响，变化趋势表现出复杂性，上、中、下游各有特点；②长江流域屏山站以上流域输沙率有上升趋势（1~5月份上升趋势达到95%的置信度水平），这与上游河床坡度较大，使泥沙不易沉积以及暴雨与降水增加有关；③长江中下游输沙呈显著下降趋势。计算结果表明，宜昌-汉口河段是长江流域泥沙主要沉积区，加上葛州坝与三峡工程的建成与投入使用，从而进一步使中下游输沙量呈下降趋势。由于下游降水增加，使下游径流量自1980s以来有微弱上升趋势，但未达到95%的置信度水平，中上游流量变化不显著。对上、中、下游人为因素与自然因素对流域流量与输沙量的变化贡献率方面需要做进一步的研究。

CHANGING CHARACTERISTICS OF SEDIMENT YIELD AND DISCHARGE DURING PAST 40 YEARS IN CATCHMENT OF THE YANGTZE RIVER

Trend of the sediment load and streamflow of Pingshan,Yichang,Hankou and Datong station along the mainstem Yangtze River and the Beipei station in the Jialingjiang River,the Huangzhuang station in the Hanjiang River was analyzed with the help of Mann Kendall trend analysis.The results indicate that:①The sediment yield of the upper catchment of the Yangtze River is in significant upward trend and is in downward trend in the middle and lower cachment of the Yangtze River;②Various influencing factors combined to result in the complicated changing patterns of the sediment yield and streamflow in different parts of the Yangtze River catchment.Natural factors (e.g.precipitation changes) exerted more influences on streamflow changes in the upper catchment of the Yangtze River.In the middle and lower cachment of the Yangtze River,climatic changes and human activities (human use of water resources) combine to have impacts on streamflow variability;③Jump time of sediment yield is in good agreement of the time when the construction and function of water reservoir starts;④Water reservoirs exert more influences on the sediment yield changes and these influences are more obvious in the river catchment of smaller drainage area than in river cachment of larger drainage area;⑤Smaller riverbed slope leads to tremendous deposition of sediment yield in the middle cachment of the Yangtze River,which together with construction of Three Gorges Dam will further reduce the downstream discharge of the sediment yield in the middle and lower catchment of the Yangtze River.