Annual discharge and annual suspended sediment loads of Beipei Hydrological Station of the Jialing River catchment were analyzed to describe the trend of Jialing River over the last five decades (1956-2006). These loa...Annual discharge and annual suspended sediment loads of Beipei Hydrological Station of the Jialing River catchment were analyzed to describe the trend of Jialing River over the last five decades (1956-2006). These loads were also analyzed to ascertain the influential factors associated with its variation with the help of Kendall's Tau-b correlation analysis and regression analysis. The results indicated that the Jialing River annual discharge showed no significant trend at >95% confidence level while the annual sediment load appeared to have a significant decrease trend over the last 50 years. A decrease in the annual sediment load was particularly apparent after the year 1985, at which a substantial shift in the sediment level occurred. This shift is attributed to the construction of numerous dams in 1980s. However, after the year of 1985, two periodical stages (1986-1991 and 1992-2006) with distinct sediment load and sediment-runoff ratio were identified. The period 1992-2006 is characterised by low sediment load, which is most probably due to the impact of large scale of soil and water conservation, which took place at the end of the 1980s. Last, models describing the relationship between the discharge and the sediment load, discharge and sediment-runoff ratio as well as between the sediment load and sediment-runoff ratio were constructed.展开更多
Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhuj...Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhujiang River(Pearl River)Estuary,to investigate the short-term variation in suspended sediment concentrations(SSCs)and the relationship between the SSC and turbulent kinetic energy,bottom shear stress(BSS),and relative wave height.Based on extreme event analysis results,extreme events have a greater influence on turbulent kinetic energy than SSC.Although a portion of the turbulent kinetic energy dissipates directly into the water column,it plays an important role in suspended sediment motion.Most of the time,the wave-current interaction is strong enough to drive sediment incipience and resuspension.When combined,the wave-current interaction and wave-induced BSSs have a greater influence on suspended sediment transport and SSC variation than current-induced BSS alone.The relative wave height also has a strong correlation with SSC,indicating that the combined effect of water depth and wave height significantly impacts SSC variation.Water depth is mainly controlled by the tide on the beaches;thus,the effects of tides and waves should be conjunctively considered when analyzing the factors influencing SSC.展开更多
The construction and operation of the Three Gorges Reservoir and the cascade reservoirs upstream have significantly altered the processes offlow and sediment in the main and tributary channels of the Yangtze River.Thi...The construction and operation of the Three Gorges Reservoir and the cascade reservoirs upstream have significantly altered the processes offlow and sediment in the main and tributary channels of the Yangtze River.This has led to substantial adjustments in the riverbed through erosion and deposition,thereby impactingflood protection,water resource utilization,navigation,and the aquatic environ-ment in the Yangtze River basin.In this study,prototype measurements were used to analyze the variations in runoff and sediment load in the main channel of the Yangtze River,as well as the changes and evolution of the riverbed.Mathematical modeling was done to predict the trends in reservoir sedimentation and riverbed adjustments.The results indicate that,apart from the significantly increased runoff and sediment load in the river source region(Zhimenda station)over the past two decades,there is no clear unidirectional trend of increasing or decreasing in the main and tributary annual runoff of the Yangtze River.However,the release of reservoir outflows undergoes significant changes throughout the year due to reservoir regulation.Suspended sediment load in the upper Yangtze River has been decreasing since the 1990s,especially after the operation of the Three Gorges Reservoir and the four cascade reservoirs in the lower reach of the Jinsha River.The factors influencingflow and sediment variations include mainly climate change and human activities such as reservoir operation and soil and water conservation.The significant changes inflow and sediment conditions have disrupted the original relative equilibrium state of the main channel of the Yangtze River,leading to riverbed adjustments.The river sections in the upper reach,located within reservoir areas,have shifted from erosional state under natural conditions to accumulative state,while the middle and lower reaches have transitioned from a relatively equilibrium state to a process dominated by erosion and reconstruction.Overall,the river regime in the reservoir area and downstream of the Three Gorges Dam remains relatively stable,but there have been adjustments in some local river sections,for example,in the curved sections,particularly in the sharply curved sections downstream of the Three Gorges Dam,where gradual or abrupt chute cutoff has occurred.In the foreseeable future,the river channel downstream of the Three Gorges Dam will remain in an unsaturated state regarding sediment transport.The process of river channel erosion will persist for a long time and have far-reaching consequences.Some long straight sections,multiple bifurcation sections,and sections with large curvature are expected to undergo certain adjustments in the river regime,necessitating continuous observation,long-term monitoring,and timely river management and channel governance.展开更多
基金supported by the National Natural Science Foundation (40901135)973 program (2007CB40720301)+1 种基金National Key Technology R&D Program (2008BAD98B02)the open fund of Institute of Changjiang River Scientific Research program (YWF0716/TB01)
文摘Annual discharge and annual suspended sediment loads of Beipei Hydrological Station of the Jialing River catchment were analyzed to describe the trend of Jialing River over the last five decades (1956-2006). These loads were also analyzed to ascertain the influential factors associated with its variation with the help of Kendall's Tau-b correlation analysis and regression analysis. The results indicated that the Jialing River annual discharge showed no significant trend at >95% confidence level while the annual sediment load appeared to have a significant decrease trend over the last 50 years. A decrease in the annual sediment load was particularly apparent after the year 1985, at which a substantial shift in the sediment level occurred. This shift is attributed to the construction of numerous dams in 1980s. However, after the year of 1985, two periodical stages (1986-1991 and 1992-2006) with distinct sediment load and sediment-runoff ratio were identified. The period 1992-2006 is characterised by low sediment load, which is most probably due to the impact of large scale of soil and water conservation, which took place at the end of the 1980s. Last, models describing the relationship between the discharge and the sediment load, discharge and sediment-runoff ratio as well as between the sediment load and sediment-runoff ratio were constructed.
基金The National Key Research and Development Program of China under contract No.2016YFC0402603the Guangdong Provincial Department of Natural Resources Project under contract No.42090038the Guangdong Provincial Department of Ocean and Fisheries Project under contract No.42090033.
文摘Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhujiang River(Pearl River)Estuary,to investigate the short-term variation in suspended sediment concentrations(SSCs)and the relationship between the SSC and turbulent kinetic energy,bottom shear stress(BSS),and relative wave height.Based on extreme event analysis results,extreme events have a greater influence on turbulent kinetic energy than SSC.Although a portion of the turbulent kinetic energy dissipates directly into the water column,it plays an important role in suspended sediment motion.Most of the time,the wave-current interaction is strong enough to drive sediment incipience and resuspension.When combined,the wave-current interaction and wave-induced BSSs have a greater influence on suspended sediment transport and SSC variation than current-induced BSS alone.The relative wave height also has a strong correlation with SSC,indicating that the combined effect of water depth and wave height significantly impacts SSC variation.Water depth is mainly controlled by the tide on the beaches;thus,the effects of tides and waves should be conjunctively considered when analyzing the factors influencing SSC.
基金Changjiang Water Science Research Joint Fund of the National Natural Science Foundation of China,Grant/Award Numbers:U2240206,U2240224Research Project on Major Scientific and Technological Issues in Watershed Water Management of MWR of China,Grant/Award Number:CKSC2020791/HL+2 种基金Fundamental Research Funds for Central Public Welfare Research Institutes of China,Grant/Award Number:CKSF2023328/HLKey Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province of China,Grant/Award Number:2021SS01Natural Science Foundation of Hubei Province,Grant/Award Number:2021CFB146。
文摘The construction and operation of the Three Gorges Reservoir and the cascade reservoirs upstream have significantly altered the processes offlow and sediment in the main and tributary channels of the Yangtze River.This has led to substantial adjustments in the riverbed through erosion and deposition,thereby impactingflood protection,water resource utilization,navigation,and the aquatic environ-ment in the Yangtze River basin.In this study,prototype measurements were used to analyze the variations in runoff and sediment load in the main channel of the Yangtze River,as well as the changes and evolution of the riverbed.Mathematical modeling was done to predict the trends in reservoir sedimentation and riverbed adjustments.The results indicate that,apart from the significantly increased runoff and sediment load in the river source region(Zhimenda station)over the past two decades,there is no clear unidirectional trend of increasing or decreasing in the main and tributary annual runoff of the Yangtze River.However,the release of reservoir outflows undergoes significant changes throughout the year due to reservoir regulation.Suspended sediment load in the upper Yangtze River has been decreasing since the 1990s,especially after the operation of the Three Gorges Reservoir and the four cascade reservoirs in the lower reach of the Jinsha River.The factors influencingflow and sediment variations include mainly climate change and human activities such as reservoir operation and soil and water conservation.The significant changes inflow and sediment conditions have disrupted the original relative equilibrium state of the main channel of the Yangtze River,leading to riverbed adjustments.The river sections in the upper reach,located within reservoir areas,have shifted from erosional state under natural conditions to accumulative state,while the middle and lower reaches have transitioned from a relatively equilibrium state to a process dominated by erosion and reconstruction.Overall,the river regime in the reservoir area and downstream of the Three Gorges Dam remains relatively stable,but there have been adjustments in some local river sections,for example,in the curved sections,particularly in the sharply curved sections downstream of the Three Gorges Dam,where gradual or abrupt chute cutoff has occurred.In the foreseeable future,the river channel downstream of the Three Gorges Dam will remain in an unsaturated state regarding sediment transport.The process of river channel erosion will persist for a long time and have far-reaching consequences.Some long straight sections,multiple bifurcation sections,and sections with large curvature are expected to undergo certain adjustments in the river regime,necessitating continuous observation,long-term monitoring,and timely river management and channel governance.
