Dynamic characteristics and influencing mechanisms of suspended sediment discharge at the outlet of Dongting Lake

doi:10.3969/j.issn.1000-5641.2018.04.016

Abstract

Abstract: Dongting Lake's storage capacity is of vital significance to the Changjiang River. The changes in suspended sediment discharge (SSD) from Dongting Lake to the Changjiang River are closely linked to both the lake's evolution and the lake-river relationship. Based on long-term hydrologic data from 1951-2015, the dynamic characteristics of SSD at theDongting Lake outlet and associated controlling factors were analyzed by using percentile, coefficient of variation, and wavelet analysis. The results showed that the SSD time series (1951-2015) could be divided into three sub-periods, namely 1951-1970,1971-2002, and 2003-2015. Specifically, SSD of the first two periods exhibited decreasing trends, while SSD during the 2003-2015 period displayed on upward tendency. Apparent seasonal fluctuations were observed in SSD with a majority of sediment transported in March-December and in March-August during 1951-1970 and 1971-2015, respectively. However, the peak monthly SSD shifted from April in 1951-2002 to May in 2003-2015. Moreover, periodic 44-year and 24-year oscillations were detected across the entire SSD data set. The variation in SSD at the outlet of Dongting Lake can be explained by runoff, water conservancy projects, and the lake's erosion-deposition pattern. It was found that runoff at the outlet of Dongting Lake was the important factor induced the seasonal fluctuation and primary periodic oscillation of SSD. The Jingjiang Cut-off Project is likely responsible for the significant SSD decrease during the period 1971-2002. Annual average SSD over the period 2003-2015 decreased by 30.1% in comparison with 1971-2002 following opening of the Three Gorges Dam. In addition, the SSD series showed an increasing trend after 2007 as the Dongting Lake basin shifted from a deposition state into an erosion state.

Key words: Dongting Lake, suspended sediment discharge, water conservancy projects

CLC Number:

P933

YU Ya-wen, DAI Zhi-jun, MEI Xue-fei, WANG Jie, WEI Wen. Dynamic characteristics and influencing mechanisms of suspended sediment discharge at the outlet of Dongting Lake[J]. Journal of East China Normal University(Natural Sc, 2018, 2018(4): 159-170.

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