Decline in suspended sediment concentration delivered by the Changjiang (Yangtze) River into the East China Sea between 1956 and 2013
Decline in suspended sediment concentration delivered by the Changjiang (Yangtze) River into the East China Sea between 1956 and 2013
复制标题
DOI：
10.1016/j.geomorph.2016.06.009
复制
发表时间：
2016-09-01
期刊：
影响因子：
3.9
通讯作者：
Gao, Jinjuan
中科院分区：
文献类型：
--
作者：
Dai, Zhijun;Fagherazzi, Sergio;Gao, Jinjuan
流入海洋的河流中悬浮泥沙浓度(SSC)的时间演变提供了对分水岭侵蚀过程的重要洞察，并决定了内大陆架的演变。近年来，泥沙从河流向海洋的输送受到了特别的关注，但很少有人关注河流含沙量的变化和动态，特别是亚洲最长的河流--长江--中国。根据大同水文站日、月流量的长期时间序列，研究了长江输往中国东海的含沙量的变化及其可能的原因。SSC数据进一步与覆盖整个流域的年降水量的水文分析进行了比较。结果表明，1956-2013年间土壤含沙量呈下降趋势，可分为三个阶段：(1)1956-1970年丰水期含沙量高(0.69 kg/m(3))，枯水期含沙量低(0.2 kg/m(3))：(2)1971-2002年丰水期含沙量相对较高(0.58 kg/m(3))，枯水期含沙量低(0.15 kg/m(3))；(3)2002年后，丰水期含沙量较低(0.19 kg/m(3))，枯水期含盐量较低(0.09 kg/m(3))。这三个时期的年平均悬浮物浓度分别为0.62、0.42和0.18 kg/m(3)。与1956-1970年相比，1971年-2002年和2002-2013年期间，SSC与排水量之间的额定曲线斜率分别下降了2%和30%。长江沿岸的土壤侵蚀、堤坝建设和堤防加固是造成悬沙浓度变化的主要原因。流量的波动也控制着SSC的长期变化。从1956年到1970年，土壤侵蚀的影响超过了蓄水的影响，这可能是造成SSC较高的原因；1970-2002年期间，蓄水的影响增加，而土壤侵蚀的影响减小，共同导致SSC的小幅下降。2002年以来，土壤侵蚀的影响进一步减小，三峡库区后方的大范围泥沙滞留是发生极低悬沙的主要原因。本文对长江泥沙资源和水质的管理提供了一个更好的策略。我们的结论可以很好地应用于类似人类活动的海洋中的其他河流。(C)2016爱思唯尔B.V.保留所有权利。
The temporal evolution of suspended sediment concentration (SSC) in a river debouching into the ocean provides vital insights into erosion processes in the watershed and dictates the evolution of the inner continental shelf. While the delivery of sediment from rivers to the ocean has received special attention in the recent past, few studies focused on the variability and dynamics of river SSC, especially in the Changjiang (Yangtze) river, China, the longest river in Asia. Here, variations in SSC delivered by the Changjiang River to the East China Sea and possible causes of its variability were detected based on a long-term time series of daily SSC and monthly water discharge measured at the Datong gauging station. The SSC data are further compared to a hydrological analysis of yearly precipitation covering the entire catchment. The results indicate the presence of a decline in SSC in the period 1956-2013, which can be divided into three phases: (i) high SSC (0.69 kg/m(3)) in the wet season and low SSC (0.2 kg/m(3)) in the dry season from 1956 to 1970; (ii) relative high SSC (0.58 kg/m(3)) in the wet season and low SSC (0,15 kg/m(3)) in the dry season from 1971 to 2002; and (iii) low SSC (0.19 kg/m(3)) in the wet season and very low SSC (0.09 kg/m(3)) in the dry season after 2002. These three periods have a mean yearly SSC values of 0.62, 0.42, and 0.18 kg/m(3), respectively. Compared with 1956-1970, the slope of the rating curve between SSC and water discharge decreased, respectively, by 2% and 30% during the period 1971-2002 and 2002-2013. Soil erosion, dam construction, and banks reinforcement along the Changjiang River are the main causes of SSC variations. Fluctuations in water discharge are also controlling the SSC long-term variations. Specifically, from 1956 to 1970, the effect of soil erosion overrules that of darn impoundment, which is likely responsible for the high SSC; during the period 1970-2002, the influence of dam impoundment increases while that of soil erosion decreases, which together produce a small reduction in SSC. Since 2002, the impact of soil erosion further decreases and large-scale sediment trapping behind the Three Gorges Darn is responsible for the occurrence of extremely low SSC. The results presented herein for the Changjiang River can inform a better management strategy of sediment resources and water quality for both the river and the coast. Our conclusions can be well applied to other rivers discharging in the ocean subject to similar human activities. (C) 2016 Elsevier B.V. All rights reserved.