Effects of cascade reservoir systems on the longitudinal distribution of sediment characteristics: a case study of the Heihe River Basin

Yu Wang,Qi Feng,Juan-Juan Liu,Yu-Hua He,Wei Liu,Xu Wang,Bao-Long Li

doi:10.1007/s11356-021-15760-y

Abstract

Spatial variations in grain size parameters can reflect river sediment transport patterns and depositional dynamics. Therefore, 22 surficial sediment samples taken from the Heihe River and its cascade reservoirs were analyzed to better understand the impact of cascade reservoir construction on sediment transport patterns in inland rivers in China. The results showed that the longitudinal distribution of sediment grain size in the Heihe River was significantly affected by the influence of the cascade reservoirs. The retention rate in the cascade reservoir of the Heihe River reached 79% (193.53 Mt/year), which caused most of the fine sand to accumulate in the reservoir, and the sediment fining degree reached approximately 50%. However, the water discharged from the dam caused serious erosion of the riverbed and coarsening of the sediment, and the coarsening degree was approximately 500%. The backwater zone of the reservoir was influenced by both backwater and released water, and the coarsening degree of sediment was approximately 101%. Sedimentary environmental analysis revealed that the characteristics of the sediment grain size in an upstream tributary of the Heihe River were more influenced by source material than by hydrodynamic conditions, while the grain size characteristics of the mainstream sediments were controlled mainly by hydrodynamic conditions. The characteristics of sediment transport in different reaches of the Heihe River were studied, and the results may provide references for the operation of cascade reservoirs and the sediment control of reservoirs.

Highlights

River sediments are a significant component of river ecosystems created by soil erosion in river basins (Bravard et al 2014), and their grain size distribution is affected by multiple factors, including sediment sources and hydrodynamic conditions (Snelder et al 2011; Zhu et al 2014; Pan et al 2015)
The nutrients adsorbed onto sediment particles, especially phosphorus, will accumulate with the sedimentation of river sediments (Muller et al 2007), which may lead to algal blooms in reservoir areas (Yang et al 2018a, b, Zhou et al 2013)
The results of this study provide the spatial variations in basic sediment information for the Heihe Rivers, thereby supporting environmental protection and water resource utilization in this area

Summary

Introduction

River sediments are a significant component of river ecosystems created by soil erosion in river basins (Bravard et al 2014), and their grain size distribution is affected by multiple factors, including sediment sources and hydrodynamic conditions (Snelder et al 2011; Zhu et al 2014; Pan et al 2015). Cascade reservoirs generate electricity to alleviate the energy crisis and control floods and adjust the uneven spatiotemporal distribution of water resources. Such a large artificial lake can have significant negative effects on a river’s hydrodynamic conditions, including water level fluctuations (Lu and Siew 2006; Wang et al 2013) and decreased velocity (Klaver et al 2007; Wei et al 2008). The lower reaches of dammed rivers, which have relatively clear water, often experience bed incision and bank collapse; these effects can further adversely impact riparian infrastructure and riverine ecosystems and cause the drawdown of the alluvial water table (Vörösmarty et al 2003; Minear and Kondolf 2009; Ran et al 2013)

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Results

Conclusion