长江上游不同水沙来源区产沙量变化对宜昌-汉口河段泥沙冲淤量的影响

长江上游流域的水沙特性表现出显著的地域分异，体现出水沙异源的特点，可以划分为两个多沙区和一个少沙清水区，即金沙江下游多沙区和嘉陵江多沙区，其余地区构成少沙清水区。以有关水文站的年系列资料为基础，研究了上游不同来源区产沙量变化对宜昌-汉口河段泥沙淤积速率的影响。研究表明，宜昌-汉口^#河段冲淤量与嘉陵江产沙区产沙量的变化有很好的同步关系。宜昌-汉口^#河段冲淤量与金沙江下游产沙区产沙量的变化，在20世纪80年代末以前有较好的同步关系，此后则不具有同步关系。这意味着，自从20世纪80年代以来，嘉陵江产沙区产沙量的变化对宜昌-汉口^#河段冲淤量的变化起着主要的控制作用，金沙江下游江产沙区产沙量的变化对宜昌-汉口^#河段冲淤量变化的控制作用较小。这一事实表明，对金沙江下游的治理亟待加强。以宜昌-汉口^#河段冲淤量Sdep，Y-H作为因变量，北碚站的年输量Qs，北碚、屏山站的年输沙量Qs，屏山、宜昌站年最大流量Qmax，宜昌以及3口分沙比Rw，div为影响变量，运用1955-1997年间的资料建立了多元回归方程，在此基础上对各个影响变量的变化对河段冲淤量的变化的贡献率进行了估算。结果表明，Qs，屏山、Qs，北碚、Qmax，宜昌以及Rw，div的贡献率分别为18．75％，42．06％，36．53％，2．64％。由此可见，嘉陵江重点产沙区产沙量变化对宜昌-汉口^#河段冲淤量变化的贡献率要大于金沙江下游重点产沙区。研究还得到，使宜昌-汉口^#河段不淤的两个重点产沙区的年产沙量之和的临界值为2．1亿t/a。

Sediment deposition in Yichang - Hankou reach of Changjiang River as influenced by sediment yield from different source areas

According to the areal differentiation of the runoff and sediment load in the Changjiang River basin,three major source areas can be identified for the upper Changjiang River basin,i.e.,the major sediment producing area of lower Jinsha River,the major sediment producing area of Jialing River,and a relatively clear water area.Based on annual data from relevant hydrometric stations,this study investigated the influence of sediment yield from different source areas in the upper Changjiang River basin on sediment deposition in the Yichang-Hankou reach of the middle Changjiang River.Good synchronic variations have been found in annual sediment yield from the Jialing River basin and in the sediment deposition in the Yichang_Hankou reach.It has been also found that before 1980,the annual sediment yield from the lower Jinsha River basin varied synchronically with sediment deposition in the Yichang-Hankou reach,but no synchronic variations could be seen afterwards.This means that since 1980,the variation in sediment deposition in the Yichang-Hankou reach is controlled by the variation in sediment yield from the Jiangling River basin,rather than by the variation in sediment yield from the lower Jinsha River basin.A multiple regression equation has been established between the annual sediment deposition amount(S_(dep,Y-H)) in the Yichang-Hankou reach and 4 influencing factors: annual sediment load(Q_(s,Beibei)) at Beibei station on the Jialing River, annual sediment load(Q_(s,Pingshan)) at Pingshan station on the Jingsha River,annual maximum discharge(Q_(max,Yichang))at Yichang station on the Changjiang River,and the ratio of flow diversion through 3 outfalls on the Jingjiang River.On this basis,the relative contributions of the variations in above 4 influencing factors to the variation in S_(dep,Y-H) has been assessed.The contributions from Q_(s,Pingshan),Q_(s,Beibei),Q_(max,Yichang) and R_(w,div) were calculated as 18.75%,42.06%,36.53% and 2.64%,respectively.Thus,the contribution from the variation in sediment yield of the Jialing River basin is much more than that from the Jinsha River basin.