Prospects for the Early 21st Century in Research of the Yellow River
CHEN Ming-zhong1, LIU
Xiao-yan2
(1.Ministry of Water Resources,P.R.China;2.Yellow River Conservancy Commission,MWR)
Abstract: There is a long history to do research work on the Yellow River, but, systematic and comprehensive research and practice on the Yellow River have started since 1949. During past 50 years, the people's awareness of water-sediment movement law has achieved a great leap in a qualitative way, which has pushed the technology on harnessing the Yellow River rapidly. Meanwhile, the approach and model of water resources development and utilization have been formed and developed gradually. However, the Yellow River is a complicated river indeed, people still have not fully mastered water-sediment movement law and its characteristics, which therefore constrains further improvement of the Yellow River harnessing and technical level of development. There is still a long and arduous way to go for the research work on the Yellow River in the 21st century.
¡¡¡¡The article reviews research results on the Yellow River of the 20th century, and analyzes current existing key scientiic and technological issues related to harnessing and development of the Yellow River, and puts forward recent key research subjects in terms of realizing sustainable utilization of water resources, ensuring safety of flood control and promoting modernization of management on the Yellow River.
Key words: the Yellow River; progress in research; practice of Yellow River harnessing; prospects for the early 21st century in research
XU Jiong-xin
(Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of
Sciences)
Abstract: Since 1986, the lower Yellow River enters a new period that is characterized by small discharges with seasonal desiccations. As a result, strong sedimentation occurs. The sedimentation can be classified as three types in terms of different morphological units, i.e., the vertical deposition of natural levee, the vertical deposition of riverbed and the lateral deposition of riverbank. The rates of the three types of deposition have been measured and reported in this study.
ªª¡¡The adjustment of channel shape of the lower Yellow River at small discharges is closely related to the rates of the three types of deposition. A multi-regression equation has been established to express the relationship between the three rates of deposition and the channel shape adjustment index ¦µ that is defined as the ratio of the bankfull width to depth before the adjustment, to that after the adjustment. The equation can be used to estimate the channel adjustment tendency for different reaches of the lower Yellow River.
ªª¡¡Influenced by the difference in channel boundary material and by the downstream variation in water discharge and sediment load, the three indices of channel deposition rate show clear tendency of downstream variation. Controlled by this, the manner of channel adjustment also shows clear difference downstream.
ªª¡¡Under the hydrological regime dominated by small discharges, the tendencies of adjustment of channel slope and bankfull slope are inverse, i.e., the channel slope tends to decrease but the bankull discharge increases. At the present, the former tendency is dominant; thus the sediment carrying capacity of the lower Yellow River tends to decrease, which intensifies channel sedimentation.
Key words: river sedimentation; channel adjustment; river shrinkage; human influences; the Yellow River
Flow Analysis and Scour Computation of the Dike-Break
ZHANG Xiu-zhong WANG Guang-qian
(Department of Hydraulic Engineering, Tsinghua University
Abstract: Based on the shallow water equations and non-equilibrium sediment transport equation, a mathematical model is developed to predict flow motion and scour hole evolution of an instantaneous dike- or dam-break. In order to simulate the complex flow phenomenon accurately and conveniently, a high-resolution finite element scheme is adopted to capture the dam-break bore. Flow analysis and scour computation are then conducted for various breach widths, discharges and soil compositon of an instantaneous dike-break. The results provide hydrodynamic conditions for structural and stability analysis of the steel, timber and earth-rock combined dam.
Key words: dike-break; scour hole; high-resolution finite element scheme; numerical simulation
Numerical Modeling of Local Scour around Spur Dikes
PENG Jing1, Nobuyuki
Tamai2, Yoshihisa Kawahara2
(1.Water Environment Department, CIWHR; 2.Department of Civil Engineering, Tokyo
University)
Abstract: Local scour and deposition around submerged spur dike was numerically simulated in the present paper. A sediment transport model of bed load that interacts with 3D turbulent flow was developed. Computation of the bed load transport considered the influences of bed slope on both critical bed shear stress and bed load transport rate. The developed model was applied to a spur dike flow over movable bed. The predicted scour hole profiles agreed reasonably well with the measured. The results clarified transient characteristics of local scour with time and the bed topography at equilibrium state.
Key words: local scour; trubulence; three-dimensional model; spur dike
Vertical Profiles of Sand-Mass Flux in Wind Tunnel
NI Jin-ren, LI Zhen-shan
(1.Center for Environmental Sciences,Peking University;2.The Key Laboratory of Water
and Sediment Sciences,Ministry of Education China)
Abstract: Existing experimental results for vertical profiles of mass flux of blown sand have shown quite different patterns in the near-bed region.To investigate these patterns and their formation cause,series of experiments were conducted for vertical and longitudinal profiles of mass flux using vertical array traps together with the horizontal sand trap composed of internal compartments in a wind tunnel¡£Five wind velocities and two particle sizes were chosen for a variety of experimental runs.Results show the satisfactory agreement of the measured profiles with the exponential decay distribution in the upper region but the deviation from the conventional law in the near-bed region.The extent of the deviation decreases with the increase of airflow shear velocity and sand grain diameter in air.Explanations were given to the cause of deviation in terms of sand motion characteristics,whereas the trend estimation of the deviation was made based on the longitudinal decay distribution measured by means of the horizontal sand trap.
Key words: aeolian mass flux profile; wind tunnel experiment; near-bed region
CHENG He-qin, LI Mao-tian
(State Key Laboratory of Estuarine & Coastal Research,East China Normal University)
Abstract: A succession of high-resolution large-scale bedform movements composed of very fine sand is shown by the high resolution survey records.They are detected by Thermal Depth Recorder,Sonar Side-scan,Endeco Current Meter along two profiles,and Optical Suspended Concentration Meter,Acoustic Suspended Concentration Profiler and D.GPS at one fixed station in the Changjiang Estuary during the last period of 1998 disastrous flood.There are several times of those detected during the dry season.These results can provide the practical data about the tremendous quantities of bedload transport,which is the mainly ambiguously long-standing problem resulting in serious shallowing in docks and navigation channels,especially for the present construction of Deep Water Channel in the Changjiang Estuary.
Key words: 1998 disastrous flood; channel bed micro-configuration; sand dune; resuspension
Dynamic Analysis of Sediment in the Yellow River
ZHANG Xue cheng, WANG Ling, GAO
Gui-cheng
(Bureau of Hydrology)
Abstract: Based on the field data from 1950 to 1999, this paper analyzed the annual variations and annual distribution of the runoff, sediment amount and concentration in the middle and lower Yellow River. Sediment changes in the lower Yellow River during the different operations of Sanmenxia reservoir are also analyzed. The result shows that sediment characteristic values in the Yellow River have been changed greatly in the last 50 years. For example, variability of the runoff, sediment amount and concentration is asynchronous, and the runoff proportion in the flood season becomes lower, but the sediment amount proportion in the flood season becomes higher.
Key words: sediment; dynamic analysis; the Yellow River
Sediment Delivery Ratio in the Upper Yangtze River
JING KeAbstract: Three conditions for defining the sediment delivery ratio are discussed in this paper, including grain size, time, and space. It is found that the main problems in the studies of sediment delivery ratio in the upper Yangtze River are lack of reliable data of sediment yield, unclear defined division between suspended and bed load, and non-quantified percentage of sediment yield from slopes and gravitational sediment yield in the total. For solving the afore-said problems, the author has done some theoretical analysis on the sediment delivery ratio in river channels and gullies and qualitative analysis on some landform indices that reflect sediment delivery ratio. The research results are that the sediment delivery ratio in the high and medium high mountain areas is close to 1 (excluding areas suffering gravitational soil erosion and debris-flow), but smaller in the hill and wide valley areas in the upper Yangtze River.
Key words: sediment; delivery ratio; the upper Yangtze River
Comparison of Desert Sand Particle Sizes Obtained from Sieving and Settling Approaches
WU Shi-liang, NI Jin-ren, LI Zhen-shanAbstract: Sieving and settling analyses for sediment particle size are primary approaches widely used inengineering practice. In order to compare the particle sizes obtained from the two different approaches, aseries of experiments were conducted for sediment samples ranged from 0.062mm to 2.0mm. The results show that the particle diameters from settling analysis are apparently greater than those from sieving analysis. The former is subject to change while different settling-velocity formulas are used for calibration.Revising relation between particle diameters in terms of sieving and settling analyses were established. In addition, the differences were found among the existing results from different investigators owing to various influencing factors such as analysis approach, experimental equipment, the formula of settling velocity used to calculate the particle diameter, the range of the particle size, and so on.
Key words: particle-size analysis; sieving approach; settling approach; particle diameter measured by sieve; particle diameter measured by settling tube
Study on Two-Dimensional Sediment Mathematical Models and Problems in Application
ZHAO Ming deng, LI Yi tianAbstract: Based on sediment diffusion and bed deformation equations, the recovery saturation coefficient and the feature of suspended load profile are analysed, and a new recovery saturation coefficient is given. For moving boundary, a new discretizing scheme with high accuracy and good stability is provided. The simulated results of the bed deformation in Nanjing reach of Yangtze River show that the proposed sediment mathematical model and method are reasonably good.
Key words: sedimentation mathematical model; recovery saturation coefficient; moving boundary; bed deformation
Design of the Movable Bed Model for the Dongzhuang Reservoir on the Jinghe River
ZHANG Hong wu1, ZHANG Jun hua2, WANG Guo dong2, CHAI Qiu-feng3, ZHANG Long rong2, YAO Wen yi2Abstract: Based on the research on the geometry deformation and the properties of model sands, this paper finishes the design of the hyperconcentrated flood model of the Dongzhuang reservoir on the Jinghe River by using the latest results on the movable model similarity laws about the Yellow River and density currents. Then, calibration tests have been carried out by using the data of the Bajazui Reservoir on the Jinghe River, whose hydraulic and sedimentation characteristics are similar to the Dongzhuang Reservoir. It is shown that the model can well repeat the prototype sediment movement and the transport properties.
Key words: Dongzhuang Reservoir; movable bed model; hyperconcentrated flood; similarity condition
Estimation of the Sedimentation in Longyangxia Reservoir
GAO Xue-jun,FENG Ling
(Bureau of Water Resources in the Upper Yellow River,YRCC,)
Abstract:Tangnaihai and Guide are the two hydrologic stations to control the incoming flow and out flow of longyangxia reservoir.There are 30-year gauge-station records before the construction of the reservoir.Through the correlation analysis of the two stations,the coresponding estimated sediment discharge at Guide station without considering the existence of the reservoir can be obtained.Therefore,the sedimentation in longyangxia reservoir can be estimated by the diffenence of the measured data at Guide station and the estimated values without the reservoir construction.
Key words:Longyangxia Reservoir;sedimentation;estimation
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