Spatial and temporal variations of suspended sediment deposition in the alluvial reach of the upper Yellow River from 1952 to 2007 Suiji Wang a, ⁎, Yunxia Yan a , Yingkui Li b a Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China b Department of Geography, University of Tennessee, Knoxville, TN 37996, USA abstract article info Article history: Received 28 May 2011 Received in revised form 28 October 2011 Accepted 22 November 2011 Available online xxxx Keywords: Suspended sediment deposition (SSD) Human impact Reservoir construction and operation Water and soil conservation Alluvial channel Yellow River The suspended sediment deposition (SSD) in the alluvial reach between the Qingtongxia station and the Toudaoguai station of the upper Yellow River has shown a dramatic variation since 1952. However, its spatial and temporal changing pattern and driving factors are still not clear. This paper examines the detailed spatial and temporal var- iations of the SSD based on the annual suspended sediment load at five gaging stations located in this alluvial reach in 1952–2007. The mean annual SSDs in four sub-reaches (Qingtongxia–Shizuishan, Shizuishan–Bayangaole, Bayangaole–Sanhuhekou, and Sanhuhekou–Toudaoguai) were calculated and analyzed for different periods. The mean annual kilometric SSDs in 1952–2007 were -0.228 10 5 , 0.97 10 5 , 0.165 10 5 and 0.006 10 5 ta -1 km -1 in the four sub-reaches, respectively, with the highest SSD occurred in the Shizuishan–Bayangaole sub-reach. Re- sults also suggested that SSD was mainly accumulated in 1952–1959 before major reservoirs were constructed and in 1986–2007 after three major reservoirs (Qingtongxia, Liujiaxia and Longyangxia) were constructed in the main stream. During 1960–1985, all sub-reaches except the Shizuishan–Bayangaole sub-reach experienced chan- nel erosion. Although climate change may play some roles, the changes in SSD were mainly influenced by human activities. In particular, the water and soil conservation actions, such as the construction of check dams from 1958 in upper stream tributaries, intercepted significant amount of suspended sediment and cause the net erosion of the main channel in the 1960s. The operation of the Qingtongxia reservoir reduced the SSD in this downstream reach in the 1970s and 1980s because upper stream suspended sediment was trapped by the reservoir and reservoir-released relative clear water scoured the downstream channel. Although the Liujiaxia and Longyangxia reservoirs trapped relatively small amount of suspended sediment, they stored a large amount of water during the flood season, reducing the discharge and the erosion capability of the downstream flow. Therefore, this opera- tion mode may increase the SSD in this river reach. In addition, with the gradual loss of the Qingtongxia reservoir's capacity in sediment storage, more suspended sediment was released to the downstream channel, causing strong SSD in this reach after 1990. © 2011 Elsevier B.V. All rights reserved. 1. Introduction River channel evolution occurs primarily in response to the changes of natural factors such as climate, surface material, sediment supply, and so on. However, with the population increase, human activities be- come a more and more important influencing factor. For example, Brown (1997) indicated that there is a long history of human–riverine interactions throughout the Holocene. The influence of human activities on river channel dynamics was intensified with the continuous increase in population and human activities, especially after the industrial revo- lution in the 1800s. Human activities, such as reservoir construction, sand mining, bank revetments, and land use alterations, have signifi- cantly changed the natural dynamics of river channels (Batalla et al., 2004; Kesel, 2003; Surian, 1999; Surian and Rinaldi, 2003; Wellmeyer et al., 2005). Human impacts on channel morphology and fluvial processes in- clude both indirect and direct influences (Kiss et al., 2008). For example, as indirect influences, land-use change and river regulation in a river basin can alter runoff and sediment yield. As a direct influence, the con- struction of dams can intercept upstream sediment and fundamentally change the fluvial hydrology (Draut et al., 2011; Kiss et al., 2008). Al- though much progress has been made in the study of channel dynamics in response to human activities, the changes in ways and by degrees of sediment transportation and the response of river channels down- stream from the constructed dams are still not clear (e.g., Draut et al., 2011; Grant et al., 2003; Kummu et al., 2010; Renwick et al., 2005; Walling and Fang, 2003; Wang and Li, 2011; Williams and Wolman, 1984; Yang et al., 2007). Here, we examine the spatial and temporal var- iations of the suspended sediment deposition (SSD) in the alluvial reach of the upper Yellow River and discuss their major influence factors asso- ciated with human activities. Catena 92 (2012) 30–37 ⁎ Corresponding author. Tel.: + 86 10 64889036; fax: + 86 10 64851844. E-mail address: wangsj@igsnrr.ac.cn (S. Wang). 0341-8162/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.catena.2011.11.012 Contents lists available at SciVerse ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena