• 全国中文核心期刊
  • 中国科技核心期刊
  • 美国工程索引(EI)收录期刊

2016 Vol. 27, No. 2

Display Method:
A study of the characteristics of sedimentation in the Lower Yellow River during overbank floods
ZHANG Min, HUANG Heqing, ZHANG Xiaohua
2016, 27(2): 165-175. doi: 10.14042/j.cnki.32.1309.2016.02.001
Abstract:
The stratigraphic structure of floodplains records the character of overbank floods occurred in the past, typically their magnitude, frequency and duration. For estimating and forecasting sediment load carried by overbank floods and for preventing from flood disasters and protecting wetland ecosystems, this study investigates the relationship between sedimentation and overbank floods in the lower Yellow River. Using the data from the Hydrological Yearbook of the Yellow River, our detailed analysis shows that during very large floods the channel of the river flow is erosional while the floodplain appears aggradational when S/Q (S is the sediment concentration and Q is the flow discharge) is smaller than 0.03. When S/Q is larger than 0.03, however, both channel and floodplain accumulate sediment. The amount of sedimentation in the floodplain is determined by the ratio of Qmax/Qp (Qmaxis the peak flow discharge and Qp is the bankfull flow discharge), the water volume over the floodplain and S. In contrast, the erosion in the channel is related not only to the water volume and sediment load of the floods but also to the sedimentation in the floodplain. During the normal overbank floods, both channel and floodplain accumulate sediment when S/Q is larger than 0.023, but when S/Q is smaller than 0.023, the channel is erosion while the floodplain appears aggradational. The channel erosion is related to S/Q and water volume of the floods while the sedimentation in the floodplain is mainly related to sediment concentration. Along the whole length of the lower Yellow River, the erosion in the channel and the sedimentation in the floodplain are concentrated mainly in the upstream reach of Sunkou, while the downstream reach of Sunkou experiences only slight erosion or minor aggradationt.
Experimental of the influence of different near-bank riverbed compositions on bank failure
YU Minghui, CHEN Xi, WEI Hongyan, HU Chengwei, WU Songbai
2016, 27(2): 176-185. doi: 10.14042/j.cnki.32.1309.2016.02.002
Abstract:
Six sets of experiments were carried out in a bend flume to study the impact of the cohesion of channel bed on the failure of cohesive banks. For comparison, the flume bed was consisted of cohesive and non-cohesive sediment, respectively. Results showed that, for channel bend with non-cohesive bed, the outer bank of the bend was eroded while a mixture of collapsed bank material was deposited near the inner bank. Net aggradation occurred at the channel bed. For channel bend with cohesive bed, both the channel bed and the outer bank were eroded. Degradation at the main flow area of the channel bed was greater than that near the outer bank. The bank toe of the outer bank of the bend with non-cohesive bed was more prone to be scoured than that of the bend with cohesive bed. Due to the adjustment of the flow structure near the outer bank of the bend, the turbulence kinetic energy of the flow can double and the circulation intensity can rise to as great as eleven times of its initial value, thus aggravating bank erosion and collapse and accelerating the transport of wasted sediment. Severe erosion occurred at the bank toe of the channel with non-cohesive bed, and the volume of collapsed bank material was two to four times of that aggravated at the bed. The wasted bank material contributed as sediment source for the riverbed. The height difference between the channel bed and the floodplain of the channel with non-cohesive bed was relatively smaller and the cross section was wider and shallower after scouring. This paper represents a preliminary study on the influence of the riverbed compositions on the channel erosion and bank failure. The results may help to guide bank protection and regulation of fluvial rivers.
Study on the sediment scouring rules by dynamic water effect in approach channel under the action of ship lock sluicing
XU Jinchao, LI Yun, XUAN Guoxiang, LIU Benqin, JIN Ying
2016, 27(2): 186-195. doi: 10.14042/j.cnki.32.1309.2016.02.003
Abstract:
In order to reduce the cost of desilting, and improve the efficiency of navigation, the desilting in the downstream approach channel by ship lock sluicing is studied with engineering practice. A two-dimensional numerical water-sediment model has been established for simulated analysis, and the hydraulic test of flow field and sediment field has been employed for verification. It explores the rules of sediment deposition in the entrance of approaching channel, analyzes the hydraulic characteristics of water conveyance system in ship lock, studies the scouring effect in the different scouring discharge, scouring time and initial siltation thickness, and obtains the relationship between water discharge of ship lock and the maximum siltation thickness. The results show that the maximum siltation thickness is decreasing with the increasing scouring time linearly under the same initial terrain and discharge, and the slop of sediment thickness is increasing with the scouring discharge. When the thickness decreases to a critical value, the scouring effect becomes weakened with the increasing scouring speed. Research results may provide theoretical reference for the desalting technology of the channel by the use of lock emptying.
Study on integrated allocation and dispatch model of water quality and quantity for the Yellow River
PENG Shaoming, ZHENG Xiaokang, WANG Yu, HE Liupeng, LIU Juan, WANG Weihao
2016, 27(2): 196-205. doi: 10.14042/j.cnki.32.1309.2016.02.004
Abstract:
The synchronous coupling of water quality and quantity is a challenging problem for integrated water resources allocation and delivery. Using the section of the Yellow River from Lanzhou to Hekouzhen as the study area, this paper presents the coupling of water quality and quantity models through the application of decomposition, coordination, coupling, and control processes while using real-time data transmission and feedback techniques. The online identification and process control of allocation and delivery targets are obtained by using parameters such as water extractions, discharges, and water quality in different functional zones. An integrated model of allocation and delivery of water quantity and associated water quality is established to manage the river network. The model is characterized by a range of unique functions such as loop iterations, on-line feedback, and rolling updates. By extrapolating from the runoff sequence of 1956 to 2000, the water demand and drainage quantities in 2020 are estimated. Consequently, the scheme of integrated allocation and delivery of water quantity and resultant water quality for the Yellow River section from Lanzhou to Hekouzhen is proposed using model optimization control methods. The results indicate that the surface water consumption in 2020 for the upper section of Hekouzhen will be 12.52 billion cubic meters through the application of the coordinated control and rational allocation methods. This represents a reduction of 0.672 billion cubic meters compared with the estimated surface water consumption values in the "Eight-Seven Diversion Scheme" of the Yellow River. In addition, the loads of key pollutants, such as COD and ammonia nitrogen, entering the Yellow River are predicted to reduce by 50.6% and 65.7%, respectively. Overall, this integrated model allows for the optimization of water quantity and the water quality associated with it and their subsequent control in a range of functional zones.
Study of sediment transport by tsunami waves: Ⅴ:influence of mangrove
CHEN Jie, GUAN Zhe, JIANG Changbo
2016, 27(2): 206-213. doi: 10.14042/j.cnki.32.1309.2016.02.005
Abstract:
In recent years, frequent tsunami disasters have caused huge losses. Mangrove forests had significant effects to tsunami disaster mitigation. The laboratory experiments were conducted to investigate the changes of cross-shore beach profiles by the tsunami waves under the influence of mangrove. The mangrove models were made of polyvinyl chloride circular tubes. The 1/10-1/20 composite slopes were constructed using the non cohesive sand. A series of solitary waves was selected as incident wave in the flume. The results show that the mangrove has great influence on the beach profile evolution. The tsunami scouring could significantly decrease as plant distribution density appropriate increase and distribution of plants optimizing. Based on the experimental data presented in this paper, an empirical relation was obtained to express the relationship between trend of beach erosion/deposition area, dimensionless maximum of deposition/erosion depths and vegetation distribution density and mode, dimensionless tsunami wave height, dimensionless specific weight parameter, beach slope etc. The study shows the internal connection of between sandy beach profile evolution and mangrove, hydrodynamics of tsunami wave, sediment and beach slope. The findings of this study have the potential to assist the tsunami disaster mitigation.
Research on the distributed “river-subsidence area-groundwater” coupling simulation of coal mining subsidence area: Ⅰ:theory and development
LI Hui, LU Chuiyu, SUN Qingyan, WANG Hao, YAN Lingjia, ZHANG Bo
2016, 27(2): 214-223. doi: 10.14042/j.cnki.32.1309.2016.02.006
Abstract:
Understanding the ponding mechanism and water cycle processes in mining subsidence areas has important practical significance for local ecological environment governance. It can also provide the scientific basis for research on comprehensive utilization of water resources in subsidence areas. This paper puts forth the control equation for mining subsidence areas based on water balance. The relationship between ponding and other hydrological factors is described in detail, and the "river-subsidence area-groundwater" coupling simulation model with a strong physical mechanism is developed based on the distributed hydrological simulation. The model can be used as a quantitative analysis tool for research in aspects of coal mining subsidence areas, such as the mechanism of ponding, transformation of water cycle, prediction of water situation changes, and the influence on the local water cycle due to the subsequent sinkage.
Effects of soil shear strength and runoff erosivity on slopes with different vegetation cover
XIAO Peiqing, YAO Wenyi, WANG Guoqing, YANG Chunxia, SHEN Zhenzhou
2016, 27(2): 224-230. doi: 10.14042/j.cnki.32.1309.2016.02.007
Abstract:
The combined effects of soil shear strength and runoff erosivity is important to quantitatively express the relationship between soil erosion resistance ability, runoff detachment, and transport capacity. We used field data and simulated rainfall experiments to study the effects of grass and shrub cover on runoff and sediment yield and its mechanical mechanism. Based on standard field plots data, runoff reduction on grass and shrub plots decreased by 28.1%-56.5% and 85.7%-100%, respectively, and sediment reduction on grass and shrub slopes decreased by 84.9%-90.7% and 98.5%-100%, respectively, compared with the bare plot. Under simulated rainfall intensities of 45, 87 mm/h and 127 mm/h on a 20° slope gradient, runoff reduction on grass and shrub slopes decreased by 51.9%-90.9% and 61.7%-80.6%, respectively, and sediment reduction on grass and shrub slopes decreased by 93.6%-99.2% and 95.5%-99.2%, respectively, compared with the bare slope. Vegetation can enhance soil shear strength. Soil shear strength was proportional to the vertical pressure on the shear surface, and it was consistent with Coulomb's law of shear strength. Soil cohesive force was negatively correlated with runoff as well as sediment yield. Runoff and sediment yield decreased with the increase in soil cohesive force. Sediment yield increased with the increase of flow shear stress, and there was a significant linear relationship between the two. The critical flow shear stresses of the grass slope and the shrub slope, respectively, were 2.64-3.16 times and 2.44-3.18 times that of the bare slope. The sediment transportation rate had a linear relationship with the flow shear stress. The critical flow shear stress and soil shear strength and the critical flow shear stress and soil cohesive force were significantly correlated. These relationships illustrate the mechanical effects of the soil erosion process. The results are useful for quantifying runoff and sediment reduction and understanding the mechanical process of soil erosion.
Modified unsaturated water flow model selection method and application to field experiments
MAO Wei, ZHU Yan, SHI Liangsheng, LIU Zhao, DAI Heng, YANG Jinzhong
2016, 27(2): 231-239. doi: 10.14042/j.cnki.32.1309.2016.02.008
Abstract:
Most popular unsaturated-saturated water flow models were developed based on solving different forms of Richards' equation. Because these models all have their unique applicability and computational accuracy, it is important to select the most reasonable and efficient model for specified problems. This research used a Bayesian Model Averaging (BMA) method to select the optimal one from six types of unsaturated water flow models (Picard-h model, Picard-θ model, Picard-mix model, Ross model, Kinematic wave model, and water balance model), using real data from field infiltration experiments. The BMA method was first implemented to estimate the model accuracy. Then a modified version of BMA for model selection was proposed to consider the model accuracy and computational cost simultaneously. The results demonstrated that Ross is the optimal model with the best model accuracy and computational efficiency. The modified BMA method will increase the probability of an efficient model and can provide a more comprehensive and reasonable model selection.
Comparison of laboratory methods for determining water retention curves in purple soil
WANG Honglan, TANG Xiangyu, XIAN Qingsong, LIU Chen, GUAN Zhuo
2016, 27(2): 240-248. doi: 10.14042/j.cnki.32.1309.2016.02.009
Abstract:
Four laboratory methods, namely, the sand box, the HYPROP system, pressure plates and the dewpoint potential meter, were used to determine soil water retention curves (SWRC) for samples of farmland purple soil. SWRC were determined over the whole entire moisture range for samples obtained from two horizons (i. e., 2-7 cm, 7-12cm). Measured data was compared to identify the most reliable method. The root-mean-square errors of the soil water content (ERMS(θ)), established under low suctions (h>-100 cm), the sand box and HYPROP system were small (0.026-0.082 cm3/cm3) with the coefficient of determination (R2) between measured water retention curves by the two methods being greater than 0.962. Contrastingly, the ERMS(θ) of soil water content, established under high suctions (h<-330 cm), using pressure plates and the dewpoint potential meter were larger (0.062-0.097 cm3/cm3), with lower R2 values (0.775-0.952). In conclusion, the selection and combined use of appropriate methods for SWRC determination, over the entire soil moisture range, should be decided upon according to the soil's pore size distribution and the application objective.
Advection and diffusion characteristics for uniform bed load particles from a semi-mechanistic model accounting for forces exerted on individual particles
FAN Niannian, NIE Ruihua, YANG Kejun, LIU Xingnian, CHEN Ridong
2016, 27(2): 249-255. doi: 10.14042/j.cnki.32.1309.2016.02.010
Abstract:
An episodic Langevin equation, which could account for forces exerted on individual particles and simulate stochastic and episodic motion characteristics of particles, is developed in order to reveal the control factor of normal or anomalous advection and diffusion characteristics for uniform particles. Using a model embedded with different distributed resting times, we study advection and diffusion characteristics by analyzing the statistical data of a large number of simulated particle trajectories. The results reveal that for uniform particles, because of the constraint of thin-tailed velocities of active particles, super-diffusion does not necessarily occur, even if their step lengths are heavy tailed. Diffusion characteristics are determined by the tail of resting times; for heavy-tailed resting times, sub-, normal, and super diffusion could all occur. The proposed semi-mechanistic model is further compared with other stochastic models, and the step time is ignored as it could result in right advection but wrong diffusion characteristics, which could be generalized for studying stochastic variables, i. e., the higher the moment of the studied stochastic variables, the more complex the model.
Experimental study on runoff and sediment yield from engineering deposition with gravel in the northern windy-sandy region, Shaanxi
KANG Hongliang, WANG Wenlong, XUE Zhide, GUO Mingming, LI Jianming, BAI Yun, DENG Liqiang, LI Yanfu
2016, 27(2): 256-265. doi: 10.14042/j.cnki.32.1309.2016.02.011
Abstract:
Engineering deposition is a special geomorphic unit which exhibits very serious soil and water loss in improvement and construction projects. Experimental research regarding the soil erosion laws of geomorphic units with different compositions and ratios under different rainfall conditions is an urgent concern. In the present study, indoor artificial rainfall simulation was applied to investigate the processes of runoff generation and sediment yield on the slope of deposition with gravel in the northern windy-sandy region of Shaanxi province, China. The results reveal the following:① The runoff coefficient influenced by infiltration rate, which changed due to the existence of gravel, first increased and then decreased linearly when the gravel content increased with a critical content of 10%, and increased linearly with the increase in rainfall intensity. ② The overland flow velocity on rocky deposition was lower than the velocity on homogeneous deposition. Stronger effects of gravel on delaying runoff were found with the increase in rainfall intensity, but the effects of rainfall intensity on velocity were weaker when the gravel content increased. ③ The soil detachment rate increased significantly after 24-33 min in the period of runoff generation. Gravel mainly affected the erosion rate after the significant increase. ④ The gravel increased the sediment yield under 1.0 mm/min rainfall intensity, while it decreased the total sediment when the rainfall intensity was higher. The results of this study are useful for providing reliable experimental information for the erosion model development of national engineering depositions.
Comparative evaluation of secondary flow correction methods for consecutive bend flow simulation
ZHOU Gang, YAO Shiming, QIN Cuicui, JIA Peng
2016, 27(2): 266-279. doi: 10.14042/j.cnki.32.1309.2016.02.012
Abstract:
Secondary flow has a substantial influence on water flow, mass transportation and riverbed evolution. However, conventional 2-D depth-averaged models usually ignore the influence of secondary flow. Furthermore, the suitability of existing secondary flow correction models is debatable. To select a secondary flow correction method that can be applied to complex consecutive bends, two typical linear model calculation schemes, the Delft3D and Lien methods, are evaluated. The influence of secondary flow is considered in the 2-D depth-averaged models proposed in this paper by calculating the dispersion stresses added to the 2-D shallow water momentum equations in orthogonal curvilinear coordinates. Four unique consecutive curved flume experiments were chosen to evaluate the simulation effects. The evaluations compared the simulated water levels and velocity distributions for a conventional 2-D model and two kinds of secondary flow correction methods. Analysis of the simulation results demonstrates that the performance of the Delft3D secondary flow correction method is the better of the two methods tested. The method has higher degrees of freedom and is suitable for different complexity levels of consecutive bend simulations. While Lien's secondary flow correction method is not suitable for sharp consecutive bend flow simulations, it can be used effectively to simulate weak or moderate bends, however, care should be taken for consecutive bends of moderate curvature. Therefore, comparison of the two methods shows that the Delft3D modeling method is the better choice for simulating flow in consecutive bends.
Field observations on water temperature and stratification in a seasonally ice-covered shallow thermokarst lake
HUANG Wenfeng, HAN Hongwei, NIU Fujun, LI Zhijun
2016, 27(2): 280-289. doi: 10.14042/j.cnki.32.1309.2016.02.013
Abstract:
In order to better understand the thermodynamic characteristics of seasonally ice-covered shallow lake, the ice freezing and melting processes, water/ice temperature variation, as well as meteorological conditions were measured in a typical thermokarst lake in central Qinghai-Tibet Plateau from October 2010 until July 2013. The temporal variations of lake temperature, development of thermocline, and the effects of lake ice on lake water thermal structure were investigated. Results indicated that a significant surface sublimation/ablation took place over the entire ice season. The daily and seasonal vertical structures of the lake temperature are significantly dominated by the change of air temperature, surface radiative fluxes, wind speed, ice thermodynamics, and heat fluxes from the lake bottom sediment. During the cycle of "ice free-freezing onset-ice growing-melting onset-melting ice breakoff-ice free", the lake temperature takes up an annual cycle of "stratification-overturning-inversion stratification-inversion-normal stratification-overturning-stratification". The thermal stratification consists only of epilimnion (mixing layer) and thermocline. Both layers can be replaced by a strong mixing process caused by strong gusts. Thus, compared with large lakes, the seasonal ice-covered shallow lakes have quite different thermodynamic characteristics.
Composite roughness of rectangular ice-covered rivers
CHEN Gang, ZHANG Yurong, ZHOU Mi, GU Shixiang
2016, 27(2): 290-298. doi: 10.14042/j.cnki.32.1309.2016.02.014
Abstract:
Composite roughness is a crucial parameter in determining the stage-discharge relationship using Manning's formula. Due to the increased resistance resulting from ice cover, a stage-discharge relationship developed in open water is not applicable to the ice-affected reason. This calls for the development of a new stage-discharge relationship. According to the Einstein hydraulic radius separation theory, the flow cross section of a rectangular ice-covered river may be divided into bed, ice and side-wall subsections. Based on the determination of hydraulic radius and sectional area of each flow subsection, this paper presents an analytical solution of composite roughness for flows in rectangular ice-covered rivers. Comparisons of the calculated results with measured data from literature show that the proposed formula does well in predicting the composite roughness of rectangular ice-covered rivers. Compared with Einstein formula and Sabaneev formula, the proposed formula produces more accurate results. For wide ice-covered rivers, if width-depth ratio is greater than 20, hydraulic radius may be considered approximately equivalent to flow depth as a simplification of relatively high precision.
Influence of hydroelectric development on water temperature downstream the Pubugou hydropower station of the Dadu River
TUO Youcai, ZHOU Chenyang, LIANG Ruifeng, LI Kefeng
2016, 27(2): 299-306. doi: 10.14042/j.cnki.32.1309.2016.02.015
Abstract:
To research the influence of hydroelectric development on water temperature of the Dadu River, a comparative analysis was done to describe the characteristics of temporal and spatial water temperature changes downstream river reach after and before completion of the Pubugou hydropower station by means of prototype observation and numerical simulation. The study showed that compared with natural condition, the current water temperature downstream the Pubugou reach had clear features of both averaging and delayed effects, as well as the phenomena of low temperature water in spring and summer and high temperature water in autumn and winter with the biggest drop of 2.4 ℃ at Gongzui tailrace in April and the biggest rise of 3.3 ℃ at Pubugou tailrace in December. The temperature stratification didn't occur in small lower reservoirs downstream the Pubugou reach, but the reservoir water weakened the water temperature rising along the reach. The water temperature process downstream the Pubugou reach was simulated well by the model that took the mechanical energy conversion into consideration, and the conversion rate of "mechanical energy and internal energy" came to 55% after calibration.
Advances in ecological environment impacts of water trading
LI Chunhui, SUN Lian, ZHANG Nan, WANG Xuan, CAI Yanpeng, XU Meng
2016, 27(2): 307-316. doi: 10.14042/j.cnki.32.1309.2016.02.016
Abstract:
In the situation that social and economic development is restricted with limited water supply, water trading is one of the most effective mechanisms to solve the water resource crisis in the world. Water trading disturbs natural distribution of water resources over spatial and temporal scales, thus has both positive and negative influences on the water quality and quantity, leading to various ecological and environmental consequences. However, there are few researches on the reviews of impacts on ecological environment of water trading. In this paper we extensively reviewed large numbers of studies regarding the impacts of water trading on water resources system. Then four main research points were proposed and analyzed, i. e., tradable water and their corresponding impacts on water quality and quantity, as well as relevant aquatic ecosystems. Based on the existing research of domestic and abroad, four potential extension researches could be undertaken in the future:① the establishment of the quantitative approaches for the impacts, ② the enhancement of studies upon specific water related subjects (e. g. water quality, ground water, and return flow), ③ the illumination of multiple water trading modes and their impacts, and ④ the consideration of the inherent uncertainties of these impacts of water trading.
Reconsidering ecologically-sound environmental operations at reservoirs
LUO Wenguang, YANG Guolu, SONG Yunhao, LU Jing
2016, 27(2): 317-326. doi: 10.14042/j.cnki.32.1309.2016.02.017
Abstract:
Applying principles of scientific development, this study analyzes long-standing questions related to ecological operations at reservoirs. Three aspects were analyzed based on previous scholarly work:what defines an ecological operation, associated engineering practices, and practices for establishing a system. The research discovered that there are many different interpretations of what it means to be an ecologically-based operation; there are different understandings of the impact that reservoir operations have on the local ecology and environment; and there is wide diversity in how non-biological factors are considered in the ecological operation of reservoirs. Given this diversity, the study examines the concepts of environmental and ecological operations at reservoirs, reservoir ecological operation and reservoir ecological and environmental operation and their operation systems, and explicitly analyzes the scientific nature and feasibility of those ecological and environmental operation approaches. This analysis is designed to inform future operational development, provide scientific guidance related to ecological and environmental operation practices, and improve the overall operations of reservoirs in a comprehensive way.