The wind-water two-phase erosion and sediment-producing processes in the middle Yellow River basin, China

Based on data from the middle Yellow River basin, a wind-water two-phase mechanism for erosion and sediment-producing processes has been found. By using this mechanism, the extremely strong erosion and sediment yield in the study area can be better explained. The operation of wind and water forces is different in different seasons within a year. During winter and spring, strong wind blows large quantities of eolian sand to gullies and river channels, which are temporally stored there. During the next summer, rainstorms cause runoff that contains much fine loessic material and acts as a powerful force to carry the previously prepared coarse material. As a result, hyperconcentrated flows occur, resulting in high-intensity erosion and sediment yield.     

Decadal trends and causes of sedimentation in the Inner Mongolia reach of the upper Yellow River,China

Using hydrological and sediment data, this study investigated decadal trends in sediment erosion/deposition in the Inner Mongolia reach of the upper Yellow River. The calculated yearly sediment erosion/deposition show that the reach was dominated by aggradation, degradation, and aggradation successively in three periods with the years around 1961 and 1987 as break‐points. By constructing relations between water discharge and sediment load, the contributions of key factors to the changes in sediment erosion/deposition in the reach were quantified. Results show that the sediment retention behind the main stem dams, the increase of natural runoff, and the decrease of sediment inputs from tributaries and upstream watershed were the main factors causing the transition from aggradation during 1955–1961 to degradation during 1962–1987. The reduction of natural runoff, the decrease of sediment retention behind dams, and the rise of sediment supply from tributaries were the key causes of the reversal from degradation in 1962–1987 to aggradation in 1988–2003. Water diversion has played an important role in the long‐term aggradation of the Inner Mongolia reach. The main stem dams had functioned to alleviate siltation after 1961, but their effects on siltation reduction had been gradually diminishing since the 1990s. Copyright © 2015 John Wiley & Sons, Ltd.     

Sediment flux into the sea as influenced by different source areas in the drainage basin: example of the Yellow River,China

Abstract

The runoff and sediment of large rivers usually come from different source areas, which make different contributions to the sediment flux into the sea. This has been studied with the example of the Yellow River in China, whose suspended sediment flux into the Bohai Sea accounts for 19.4% of the world total. The drainage basin of this river can be divided into four major water and sediment source areas. The sediment flux into the sea is found to be closely related to the water and sediment from the different source areas in the drainage basin and, accordingly, an empirical regression model has been established to express this relationship. According to this model, in each tonne (t) of sediment from the fine sediment producing area (FSA), 0.85 t (for yearly series) and 0.72 t (for event series) can be transported into the sea; in each tonne of sediment from the coarse sediment producing area (CSA), only 0.21 t (for yearly series) and 0.34 t (for event series) can be transported into the sea. Since the 1970s, the Yellow River's sediment flux into the sea has declined markedly and this reduction can be attributed to a great degree to the soil control measures in the fine sediment producing area. Coupling the models of this study to the previously established models for estimating the impacts of soil control measures on water and sediment balance in the Yellow River basin, a quantitative prediction may be made for the change of sediment flux into the sea that might result from climate change and human activities in the future.     

黄河中游小北干流段持续淤积期的主槽摆动特点

黄河中游小北干流河段为典型的游荡型河段,主槽经常发生摆动,揭示主槽摆动特点对研究该河段的河床演变规律具有重要意义.以1986-2001年小北干流段汛后卫星遥感资料与实测29个淤积大断面地形资料为基础,计算了断面及河段尺度的主槽摆动宽度与强度,定量分析了持续淤积期小北干流段的主槽摆动特点及其主要影响因素.计算结果表明:主...     

Sediment retention by check dams in the Hekouzhen-Longmen Section of the Yellow River

Coarse sediment retention by check dams is analyzed for five typical catchments in the Hekou-Longmen section of the midstream of the Yellow River, which is an area of high .coarse sediment concentration. The catchments are the Huangfuchuan, Kuye, Wuding, Sanchuan and Qiushui River Basins. The amount of coarse sediment retained by check clams in these areas for different periods was measured. Sediment reduction due to check clams is compared with other soil conservation measures and the results show that check clams are the most effective to rapidly reduce the amount of coarse sediment entering the Yellow River. If the average percentage of the drainage area with check clams for the five typical catchments reaches 3.0%, the average sediment reduction ratio can reach 60%. Therefore, to rapidly and effectively reduce the amount of sediment, especially coarse sediment, entering the Yellow River, the area percentage of check clams in the Hekou-Longmen section should be kept around 3%. The Kuye and Huangfuchuan River Basins are the preferred main catchments in which such water conservation measures are implemented.     

Using sediment rating parameters to evaluate the changes in sediment transport regimes in the middle Yellow River basin,China

This study analyses the changes in sediment transport regimes in the middle Yellow River basin (MYRB) using sediment rating parameters. Daily streamflow and suspended sediment concentration data were collected at 35 hydrological stations from the 1950s to 2016, which can be divided into three periods based on the type and intensity of human activities: the base stage before 1970, the restraining stage from 1971 to 1989, and the restoration stage after 2002. Data within each period were fitted by log‐linear sediment rating curves and the sediment rating parameters were utilized to analyse the spatial and temporal variations in sediment transport regimes. The results show that sediment rating parameters are indicative of sediment transport regimes. In the base stage and the restraining stage, the hydrological stations can be categorized into four groups based on their locations on the rating parameter plot. The stations with small drainage basins were characterized by the highest sediment transport regime, followed by those located in the coarse‐particle zone, the loess zone, and the mountainous/forest zone. In the restoration stage, the difference in sediment transport regimes between different geomorphic zones became less distinguishable than in previous stages. During the transition from the base stage to the restraining stage, sediment rating parameters showed no significant changes in sediment transport regimes in all four geomorphic groups. During the transition from the restraining stage to the restoration stage, significant changes were observed in the coarse‐particle zone and the mountain/forest zone, indicating that the revegetation programme and large reservoirs imposed a stronger influence on sediment transport regimes in these two zones than in the rest of the MYRB. This study provides theoretical support for evaluating sediment transport regimes with sediment rating parameters.     

Influence of storm-related sediment storage on the sediment delivery from tributary catchments in the upper Waipaoa River,New Zealand

Although much is known about overall sediment delivery ratios for catchments as components of sediment production and sediment yield, little is known about the component of temporary sediment storage. Sediment delivery ratios focused on the influence of storm-related sediment storage are measured at Matakonekone and Oil Springs tributaries of the Waipaoa River basin, east coast of New Zealand. The terrace deposits of both tributaries show abundant evidence of storm-related sedimentation, especially sediment delivered from Cyclone Bola, a 50 year return rainfall event which occurred in 1988. The sediment delivery ratio is calculated by dividing the volume of sediment transported from a tributary to the main stream by the volume of sediment generated at erosion sites in the tributary catchment. Because the sediment delivery volume is unknown, it can be calculated as the difference between sediment generation volume and sediment storage volume in the channel reach of the tributary. The volume of sediment generated from erosion sites in each tributary catchment was calculated from measurements made on aerial photographs dating from 1960 (1:44 000) and 1988 (1:27 000). The volume of sediment stored in the tributary can be calculated from measurements of cross-sections located along the tributary channel, which are accompanied by terrace deposits dated by counting annual growth rings of trees on terrace surfaces. Sediment delivery ratios are 0·93 for both Matakonekone catchment and Oil Springs catchment. Results indicate that Oil Springs catchment has contributed more than twice the volume of sediment to the Waipaoa River than the Matakonekone catchment (2·75 × 10⁶ m³ vs 1·22 × 10⁶ m³). Although large volumes of sediment are initially deposited during floods, subsequent smaller flows scour away much of these deposits. The sediment scouring rate from storage is 1·25 × 10⁴ m³ a⁻¹ for Matakonekone stream and 0·83 × 10⁴ m³ a⁻¹ for Oil Springs stream. Matakonekone and Oil Springs channels respond to extreme storms by instantaneously aggrading, then gradually excavating the temporarily stored sediment. Results from Matakonekone and Oil Springs streams suggest a mechanism by which event recurrence interval can strongly influence the magnitude of a geomorphic change. Matakonekone stream with its higher stream power is expected to excavate sediment deposits more rapidly and allow more rapid re-establishment of storage capacity. Copyright © 1999 John Wiley & Sons, Ltd.     

Sediment jamming of a trunk stream by hyperconcentrated floods from small tributaries: case of the Upper Yellow River,China

ABSTRACT

The tributary–trunk stream relationship is investigated with respect to hyperconcentrated flows and coupled wind–water processes in the Yellow River, China. Ten small tributaries that drain only 3% of the total drainage area of the trunk stream transport large amounts of relatively coarse sediment from the desert to the trunk stream during hyperconcentrated floods. The resultant strong sedimentation often jams the trunk stream, leading to serious disasters. This study reveals the cause of this interesting phenomenon and proposes countermeasures for disaster reduction. A typical sediment-jamming event (SJE) in July 1989 was thoroughly analysed based on the observational data, including the beginning, development and final stages of the event. An index of the geomorphologic effectiveness of the tributary on the trunk stream and a number of indices describing SJEs and the influencing factors are adopted, based on which a discrimination relationship for the occurrence of SJEs is established and some statistical relationships are also established. The SJE’s hydrological and geomorphologic impacts are discussed at short timescales (from several days to one month) and at long time scales (up to 46 years). The results may help to gain a new insight into the study of the tributary–trunk stream relationship, and provide useful information for sediment management and disaster-reduction planning in the drainage basin. Countermeasures are suggested to reduce the channel sedimentation and the risk of sediment-jamming disaters.

Editor M.C. Acreman Associate editor Q. Zhang     

Physically based simulation of the streamflow decrease caused by sediment‐trapping dams in the middle Yellow River

As a result of climate change/variation and its aggravation by human activities over the past several decades, the hydrological conditions in the middle Yellow River in China have dramatically changed, which has led to a sharp decrease of streamflow and the drying up of certain tributaries. This paper simulated and analysed the impact of sediment‐trapping dams (STDs, a type of large‐sized check dam used to prevent sediment from entering the Yellow River main stem) on hydrological processes, and the study area was located in the 3246 km² Huangfuchuan River basin. Changes in the hydrological processes were analysed, and periods of natural and disturbed states were defined. Subsequently, the number and distribution of the STDs were determined based on data collected from statistical reports and identified from remote sensing images, and the topological relationships between the STDs and high‐resolution river reaches were established. A hydrological model, the digital Yellow River integrated model, was used to simulate the STD impact on the hydrological processes, and the maximum STD impact was evaluated through a comparison between the simulation results with and without the STDs, which revealed that the interception effect of the STDs contributed to the decrease of the streamflow by approximately 39%. This paper also analysed the relationship between the spatial distribution of the STDs and rainfall in the Huangfuchuan River basin and revealed that future soil and water conservation measures should focus on areas with a higher average annual rainfall and higher number of rainstorm hours. © 2015 The Authors Hydrological Processes Published by John Wiley & Sons Ltd.     

Sediment budgets for a sediment‐laden river: the lower Wei River in the period 1960–1990

Fluvial sediment delivery is the main form of sediment transfer from the land to the sea, but this process is currently undergoing significant variations due to the alteration of catchment and base level controls related to climate change and human activities, especially the widespread construction of dams. Using the lower Wei River as an example and an integrated approach, this study investigates the variation of fluvial sediment delivery, as well as the connectivity under the effects of both controls. Based on hydrological records and channel cross‐section surveys, sediment budgets were constructed for two periods (1960–1970, 1970–1990) after the dam was closed in 1960. In the period 1960–1969, due to the elevated base level (327.2 ± 1.62 m) caused by the dam, the aggradation rate was 0.451 × 10⁸ t yr^‐1 in the channel and 0.716 × 10⁸ t yr^‐1 on the floodplain, indicating that the positive lateral connectivity between these locations was enhanced. As a consequence, serious sediment storage resulted in a sediment delivery ratio (SDR) that was smaller than that occurring before 1960. In the period 1970–1990, sweeping soil and water conservation (SWC) measures were implemented, resulting in a reduction of the connectivity between the trunk and tributaries, and a decrease of ~31% in the mean sediment input. In addition, together with the base level fluctuation in the range of 327.47 ± 0.49 m, the annual variation in sediment storage was primarily dependent on the water–sediment regime affected by the SWC. The negative lateral connectivity was enhanced between the channel and floodplain via bank erosion. Consequently, the aggradation rate was reduced by 89% on the floodplain and by 96% in the channel. Sediment output continued to decrease primarily due to the SWC practices and climate changes in this period, whereas the SDR increased due to the enhanced longitudinal connectivity between the upstream and downstream. Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of dilution on downstream channel sedimentation in large rivers: the Yellow River,China

Due to the temporal decoupling of water and sediment sources in a large river basin, a flood from a sediment source area with high suspended sediment concentration (SSC) may be diluted by flow from a major runoff source area with low SSC. In this paper, this dilution effect is considered for 145 flood events from the Yellow River, China. Two indices (β₁ and β₂) describing the dilution effect are proposed, based on water and sediment from the clear water source area and the coarse sediment producing area. Regression equations between channel sedimentation (S_dep) and β₁ and β₂ are established based on flood events and annual data, respectively. The results show that dilution reduces channel sedimentation in the lower reaches by 34?1% and that this is related to a reduced frequency of hyperconcentrated flows in the lower reaches. The Longyangxia Reservoir for hydro‐electric generation has stored huge quantities of clear runoff from the upper Yellow River during high‐flow season since 1985, greatly reducing the dilution of the hyperconcentrated floods and therefore enhancing sedimentation in the lower reaches. For the purpose of reducing sedimentation, changing the operational mode of the Longyangxia Reservoir to restore the dilution effect is suggested. Copyright © 2013 John Wiley & Sons, Ltd.     

Sedimentation of overbank floods in the confined complex channel–floodplain system of the Lower Yellow River,China

The channel boundary conditions along the Lower Yellow River (LYR) have been altered significantly since the 1950s with the continual reinforcement and construction of both main and secondary dykes and river training works. To evaluate how the confined complex channel–floodplain system of the LYR responds to floods, this study presents a detailed investigation of the relationship between the tempo‐spatial distribution of sedimentation/erosion and overbank floods occurred in the LYR. For large overbank floods, we found that when the sediment transport coefficient (ratio of sediment concentration of flow to flow discharge) is less than 0.034, the bankfull channel is subject to significant erosion, whereas the main and secondary floodplains both accumulate sediment. The amount of sediment deposited on the main and secondary floodplains is closely related to the ratio of peak discharge to bankfull discharge, volume of water flowing over the floodplains, and sediment concentration of overbank flow, whereas the degree of erosion in the bankfull channel is related to the amount of sediment deposited on the main and secondary floodplains, water volume, and sediment load in flood season. The significant increase in erosion in the bankfull channel is due to the construction of the main and secondary dykes and river training works, which are largely in a wide and narrow alternated pattern along the LYR such that the water flowing over wider floodplains returns to the channel downstream after it drops sediment. For small overbank floods, the bankfull channel is subject to erosion when the sediment transport coefficient is less than 0.028, whereas the amount of sediment deposited on the secondary floodplain is associated closely with the sediment concentration of flow. Over the entire length of the LYR, the situation of erosion in the bankfull channel and sediment deposition on the main and secondary floodplains occurred mainly in the upper reach of the LYR, in which a channel wandering in planform has been well developed.     

Delineation of reservoirs using remote sensing and their storage estimate: an example of the Yellow River basin,China

Reservoirs are an integral component of water resources planning and management. Periodic and accurate assessment of the water storage change in reservoirs is an extraordinarily important aspect for better watershed management and water resources development. In view of the shortcomings of conventional approaches in locating reservoirs' spatial location and quantifying their storage, the remote sensing technique has several advantages, either for a single reservoir or for a group of reservoirs. The satellite‐based remote sensing data, encompassing spatial, spectral and temporal attributes, can provide high‐resolution synoptic and repetitive information with short time intervals on a large scale. Using remote sensing images in conjunction with Google Earth and field check of representative reservoirs, the spatial distribution of constructed reservoirs in the Yellow River basin was delineated, and their storage volume and the residence time of the stored water were estimated. The results showed that 2816 reservoirs were extracted from the images, accounting for 89·5% of the registered total. All large‐ and medium‐sized reservoirs were extracted while small reservoirs may not be extracted due to coarse resolution and cloud‐cover shadows. An empirical relationship between the extracted water surface area and the compiled storage capacity of representative reservoirs was developed. The water storage capacity was estimated to be 66·71 km³, about 92·7% of the total storage capacity reported by the authority. Furthermore, the basin was divided into 10 sub‐basins upon which the water's residence time was analysed. The water discharge in the basin has been greatly regulated. The residence time has surged to 3·97 years in recent years, ranking the Yellow River in the top three of the list in terms of residence time and flow regulation among large river systems in the world. It is expected that it will be further extended in future owing to decreasing water discharge and increasing reservoir storage capacity. Copyright © 2011 John Wiley & Sons, Ltd.     

The impact of vegetation restoration on erosion-induced sediment yield in the middle Yellow River and management prospect

Serious soil erosion on the Loess Plateau has be-come the focus of world attention.As early as the1950s China has started soil and water conservation work on the Loess Plateau in order to improve the lo-cal eco-environment and mitigate the threat of the coarse sediment in the middle Yellow River to the river channel at downstream.Facts proved that the best alternative is the integrated management of hill slopes and gullies in combination with biological and engineering measures.Biological m…     

Characterizing and identifying bedforms in the wandering reach of the lower Yellow River

The lower Yellow River （LYR） is a fully alluvial system with a fine-grained bed that has a high proportion of silt.Bathymetric survey data collected with a Multi-Beam Echo Sounder （MBES） from the wandering reach of the LYR indicates that the bedforms are characterized by large aspect ratios （wavelength/height）and low lee-side angles.Since the Xiaolangdi Reservoir （XLD） has been operational in the middle reach of the Yellow River,bedforms have been dominated by two-scales of dunes,that is,a frame...     

Tide‐modulated hyperpycnal flows off the Huanghe (Yellow River) mouth,China

Few hyperpycnal flows have ever been observed in marine environments although they are believed to play a critical role in sediment dispersal within estuarine and deltaic depositional systems. The paper describes hyperpycnal flows observed in situ off the Huanghe (Yellow River) mouth, their relationship to tidal cycles, and the mechanisms that drive them. Simultaneous observations at six mooring stations during a cruise off the Huanghe mouth in the flood season of 1995 suggest that hyperpycnal flows observed at the river mouth are initiated by high concentrations of sediment input from river and modulated by tides. Hyperpycnal flows started near the end of ebb tides, when near‐bottom suspended sediment concentration (SSC) increased rapidly and salinity decreased drastically (an inverse salt wedge). The median grain size of suspended particles within the hyperpycnal layer increased, causing strong stratification of the suspended sediments in the water column. Towards the end of flood tides, the hyperpycnal flow attenuated due to frictions at the upper and lower boundaries of the flow and tidal mixing, which collapsed the stratification of the water column. Both sediment concentration and median grain size of suspended particles within the bottom layer significantly decreased. The coarser sediment particles were deposited and the hyperpycnal flows stopped. The intra‐tidal behaviors of hyperpycnal flows are closely associated with the variations of SSC, salinity, and stratification of the water column. As nearly 90% of riverine sediment is delivered to the sea during the flood seasons when hyperpycnal flows are active, hyperpycnal flows at the Huanghe mouth and the river's high sediment loads have caused rapid accretion of the Huanghe delta. Copyright © 2010 John Wiley & Sons, Ltd.     

Impacts of climate change and hydraulic structures on runoff and sediment discharge in the middle Yellow River

Due to climate change and its aggravation by human activities (e.g. hydraulic structures) over the past several decades, the hydrological conditions in the middle Yellow River have markedly changed, leading to a sharp decrease in runoff and sediment discharge. This paper focused on the impacts of climate change and hydraulic structures on runoff and sediment discharge, and the study area was located in the 3246 km² Huangfuchuan (HFC) River basin. Changes in annual runoff and sediment discharge were initially analysed by using the Mann–Kendall trend test and Pettitt change point test methods. Subsequently, periods of natural and disturbed states were defined. The results showed that both the annual runoff and sediment discharge presented statistically significant decreasing trends. However, compared with the less remarkable decline in annual rainfall, it was inferred that hydraulic structures might be another important cause for the sharp decrease in runoff and sediment discharge in this region. Consequently, sediment‐trapping dams (STDs, a type of large‐sized check dam used to prevent sediment from entering the Yellow River main stem) were considered in this study. Through evaluating the impacts of the variation in rainfall patterns (i.e. amount and intensity) and the STD construction, a positive correlation between rainfall intensity and current STD construction was found. This paper revealed that future soil and water conservation measures should focus on areas with higher average annual rainfall and more rainstorm hours. Copyright © 2015 John Wiley & Sons, Ltd.     

Sediment transferring function of the lower reaches of the Yellow River influenced by drainage basin factors and human activities

Since 1986, with a sharp decrease in water dis-charges, the Yellow River has entered a period charac-terized by low discharges and seasonally occurring dry-ups[1,2]. Since 1999, more strict management of water diversion has been imposed, and therefore the dry-ups have been well under control. However, the lower reaches of the Yellow River is still predominated by low-discharges, and has become a man-induced shrinking river. In the past 40 years, significant effect of soil and water conservat…     

Predictability of sediment transport in the Yellow River using selected transport formulas

This paper evaluates the applicability of the sediment transport methods developed by Engelund and Hansen, Ackers and White, Yang et al., and van Rijn, together with the Wuhan methods developed in China, to the Yellow River, which has highly concentrated and fine-grained sediment. The sediment data includes over 1000 observations from the Yellow River, 32 sets of data from a canal, and 266 sets of data from laboratory flumes. The best predictions were obtained by the Yang 1996 method, the Wuhan method, and the modified Wuhan method by Wu and Long, while reasonably good predictions were also provided by the van Rijn 2004 method. The Engelund and Hansen, the Ackers and White, and the van Rijn 1984 methods in their original forms are not applicable to the Yellow River. The predicted results for total load concentrations were as good as for bed-material concentrations, even though the total load includes a large portion of wash load.     

Analysis and partitioning of terrestrial water storage in the Yellow River source region

In order to increase the capability to understand and quantify the spatial differences in terrestrial water storage (TWS), and to reflect the unique energy balance processes and soil freeze–thaw mechanisms in the Qinghai-Tibet Plateau (QTP), this study improved the energy balance processes of the water and energy transfer processes model, including its surface radiation calculations and snowmelt module. By integrating these improvements, a water and energy transfer processes model in Qinghai-Tibet Plateau (WEP-QTP) for the Yellow River source region (YRSR) is developed. Using the improved WEP-QTP model to perform simulations, we assessed the daily changes in snow cover, soil moisture (SM), permafrost (PM), and groundwater storage (GWS) in the YRSR. Our analysis revealed an increase in TWS of 0.24 mm/yr from 1961 to 2020. Snow water equivalent (SWE), SM, PM, and GWS have proportional contributions of 8.33%, 216.67%, −154.17%, and 29.17% to the increased TWS, respectively. SM is the primary component of TWS. Temperature (T), precipitation (P), evapotranspiration (E), and solar radiation (Rs) influence the spatiotemporal variations in TWS, as well as those of its components. The increase in P is the primary cause for the rise in TWS, SWE, and SM, while the increase in T predominantly contributes to the decrease in PM. Furthermore, permafrost degradation and climate-induced warming and humidification lead to increased infiltration, resulting in elevated GWS.