• 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

2011 Vol. 22, No. 2

Display Method:
Variations of surface humidity and its influential factors in Northwest China
HUANG Xiao-yan, ZHANG Ming-jun, JIA Wen-xiong, WANG Sheng-jie, ZHANG Ning
2011, 22(2): 151-159.
Abstract:
Based on the daily data of 112 meteorological stations from 1960 to 2009,the potential evaporation(PE) is calculated using the UN Food and Agriculture Organization(FAO)Penman-Monteith model,and then the humid index is reconstructed from the PE in Northwest China.With the method of Inverse Distance Weighted,Mann-Ken-dall,etc,the temporal and spatial variations of humid index are discussed,as well as its impact factors.The result indicates that the humid index increases in the last 50 years with an increasing rate of 0.006/10a,which are obvious in spring and winter.From northwest to southeast,the humid index displays a marked high-low-high trend in spatial distribution.According to the spatial variation,the study areas can be divided into three sub-regions:obvious increasing,light increasing and continuous decreasing.The influential factors have different impacts on the surface humidity index during different times in the past 50 years,showing a positive correlation with precipitation and-relative humidity,and negative correlation with sunshine duration,potential evaporation and wind speed.
Global calibration of Hargreaves equation and its applicability in China
HU Qing-fang, YANG Da-wen, WANG Yin-tang, YANG Han-bo
2011, 22(2): 160-167.
Abstract:
As one of the simplest empirical methods for positional evapotranspiration(ET0) calculation,it is still lack of systemic evaluation for Hargreaves equation's computational accuracy and applicability evaluation in different climatic regions.In this paper,the Hargreaves equation is calibrated using the global optimization algorithm SCE-UA(Shuffled Complex Evolution method developed at University of Arizona).The value of ET0 calculated by the Penman-Monteith equation is used as the benchmark.The global calibration is done using a monthly time step at 105 climate stations distributed over the continental China as well as on Hainan Island.The regional distribution of the calibrated parameters is analyzed and influencing-actors on the parameters are investigated.The applicability of the calibrated Hargreaves equation in seven different climatic regions is synthetically evaluated for the longterm consistency and the seasonal consistency.The influencing factors on the accuracy of the calibrated Hargreaves equation are investigated using the method of correlation analysis.Results show that globally calibrated parameter values of the Hargreaves equation using SCE-UA are essentially different from that recommended by Food and Agriculture Organization(FAO) of the United Nations.However,the accuracy of the equation is highly promoted and the calibrated parameters at the 105 stations exhibit a certain regional regularity and may vary with annual precipitation and temperature.At almost all the stations on the Qinghai-Tibet Plateau,Northwest and Southwest China,the calibrated Hargreaves equation is applicable all year round.In contrast,poor calculation of ET0 is found in all seasons in South China.The calibrated Hargreaves equation is only valid during summer and autumn seasons over Northeast and North China and the Xinjiang Autonomous Region.Generally,the disability in calculating the aerodynamic component of ET0 is the main source of errors causing computational defect in the Hargreaves equation over different regions.The accuracy of the calibrated Hargreaves at most stations is notably related to the ratio(K) of the aerodynamic component to ET0 calculated by the Penman-Monteith equation.The computational accuracy deteriorates with decreasing of K.The opposite is true for annual precipitation and temperature.While,effects of relative humidity and wind speed on the computational accuracy are rather complicated,varying with regions.
Effects of spatial detail of soil data on distributed hydrological modeling
LI Run-kui, ZHU A-xing, QIN Cheng-zhi, CHEN La-jiao, LIU Jun-zhi
2011, 22(2): 168-174.
Abstract:
Effects of different soil data resolutions on distributed hydrological modeling and total water yield were investigated using a modeling approach.The semi-distributed SWAT(Soil and Water Assessment Tool) model and the fully distributed WetSpa(Water and Energy Transfer between Soil,Plant and Atmosphere) Extension were used in this study.Both the US SSURGO(Soil Survey Geographic) soil data and the detailed SoLIM(Soil-land Inference Model) soil data were utilized in the modeling investigation.Results show that different soil data resolutions will lead to a large discrepancy in modeling water yield at simulation points distributed over a watershed.However,the difference in simulation of total water yield decreases with increasing the area of watersheds.Based on the modeling experiment,it is recommended that detailed spatial data will be required where the simulation primarily focuses on the spatial distribution of water fluxes,while the data condition could be relaxed for the simulation of total water yield especially for large-sized watersheds.
Climate change and its impact on water resources in Yixun River basin
YANG Zhi-yong, YU Ying-dong, WANG Jian-hua, YAN Deng-hua
2011, 22(2): 175-181.
Abstract:
In recent decades,the global climate has changed markedly characterized by the increasing temperature,and the water resources and the environment are all influenced significantly.Haihe River basin is one of the most intense river basins in water resources in China,and its water resources could be very sensitive to the climate change.In this paper,considering it is less affected by human activities,the Yixun River basin is used as the research region.Based on the previous studies in the context of future climate change in Haihe River,a total of twenty climate change scenarios are constructed.The Spatial Averaging Watershed Hydrological Model is used to simulate hydrological cycling under different climatic change scenarios in the Yixun River basin.The model is characterized as a watershed-scale distributed hydrological model.Climate change impacts on water resources in the basin are analyzed.Results show that the increase in runoff lost to evaporation could be as high 3.8 mm with a temperature rise of 1℃.The increase in precipitation could lead to the rise in both evaporation and runoff.Among those two,50% of the precipitation rise would be lost to the evaporation process,and the increase in runoff could be as high as 30% as the result.Both runoff and evaporation could be more sensitive to higher temperature and extreme precipitation.The runoff condition in the Yixun River basin could be further deteriorating under a changing climate that is characterized by rising in temperature and the uncertainty in precipitation trends.
Adaptive wavelet denoising method based on sample entropy
SHANG Xiao-san, WANG Shi-cheng, WANG Zhen-long, WANG Dong
2011, 22(2): 182-188.
Abstract:
It is a key problem of properly selecting and determining the threshold value for wavelet denoising.In this paper,a new method is proposed to adaptively determine the threshold for wavelet analysis.The method uses the character of sample entropy and combines it with wavelet denoising method.Using the method,the sample entropy values are computed for noise time series with different threshold values.The relationship between the sample entropy values and the corresponding threshold values can thus be obtained.As the result,the threshold value is determined at the point with maximum entropy.The method is tested using the synthetic data and annual runoff series from Yingluoxia on the Heihe River basin and Huayuankou on the Yellow River basin.Results show that the method is able to separate the signal and noise from hydrological time series with a good denoising performance.The resulting signal is able to retain the characteristics of hydrological time series and evaluation indexes.The method also offers a new approach to determine the threshold value for wavelet denoising.
One-dimensional model for coupling surface water flow with solute transport for border fertigation: Ⅰ. Model solution
ZHANG Shao-hui, XU Di, LI Yi-nong, BAI Mei-jian
2011, 22(2): 189-195.
Abstract:
Improvement of stability,convergence and computational efficiency in numerical modeling of surface water flow and solute transport for border fertigation is useful to design and evaluation of border fertigation systems.In this study,a one-dimensional model for coupling surface water flow with solute transport for border fertigation is developed and presented.The model is based on the implicit-explicit time scheme,and uses the finite-difference method,the finite-volume method,and the finite-element method to discretize the space derivative of the physical flux vector linear approximation,the space derivative of the physical flux vector,the solute diffusion vector and the bottom element vector.The governing equations for the model can thus be solved numerically.
One-dimensional model for coupling surface water flow with solute transport for border fertigation: Ⅱ. Model verification
ZHANG Shao-hui, XU Di, LI Yi-nong, BAI Mei-jian
2011, 22(2): 196-202.
Abstract:
In this accompanying study,we compare and analyze the differences in stability,convergence,precision and efficiency resulting from the use of two methods in the solution of the one-dimensional model for coupling surface water flow with solute transport for border fertigation(1-DMCSWFSTBF).The first method is the hybrid numerical method,while the second one is the Roe finite volume method.Results show that the hybrid numerical method produces better numerical stability and convergence compared to the Roe finite volume method.Under the same circumstances of measurement,the former method is 2.5 times more computationally effective than the latter one,and the corresponding average relative error and water balance error are also improved.Thus,1-DMCSWFSTBF based on the hybrid numerical method can significantly increase the computational stability and convergence,and can effectively improve the computational precision and efficiency.The model can be used as an effective simulation tool for the design and performance evaluation of border fertigation systems.
Hydrodynamic model for complex flow in open-channel networks
ZHU De-jun, CHEN Yong-can, WANG Zhi-yong, LIU Zhao-wei
2011, 22(2): 203-207.
Abstract:
A hydrodynamic model for open-channel networks is established using the newly proposed junction-point water stage prediction and correction(JPWSPC) method,which treats backwater effects at the junctions.In the model,the Saint-Venant equations are discretized using the Preissmann scheme.The resulting equations are solved using the Newton-Raphson method.The model needs neither specific node-numbering nor setting up and solving branch equations.Thus the model is applicable to both dentritic and looped channel networks,and more robust and efficient.
Modeling soil moisture responses under evaporative conditions
YANG De-jun, ZHANG Ke-feng
2011, 22(2): 208-214.
Abstract:
Based on the finite element method(FEM) and the modified integrated Richards equation model(IRE),the responses of soil moisture under the evaporative condition for 5 different soil types were numerically studied in this paper.Numerical experiments were carried out on the 100-cm high soil columns subject to a constant potential evaporation of 0.5 cm/d and free drainage from near saturation.The results show that the variations in vertical distributions of soil moisture content for the 5 soil types exhibit a single inflexion at about the depth of 20 cm,and the curvature in upper region is greater than that in lower region.The variation in soil moisture content is more rapid in the first 15 days than that in the late period.The three-phase theory for evaporation can thus be confirmed by the results.The cumulative evaporation and water loss at the lower boundary are highly related to the soil textures.Furthermore,the changes in the amount and rate of total soil moisture are also found to be soil texture specific.Results obtained by both IRE and FEM methods are in good agreement,indicating that the simple IRE method is reliable and can be used for modeling soil water dynamics.
Bed load transport with bed seepage
LU Yan, LU Yong-jun, LI Shou-qian
2011, 22(2): 215-221.
Abstract:
The bed load transport rate in a river can be affected by the seepage-induced non-hydrostatic pressure distribution that is due to the difference in water level between the free surface in the river and the vicinal groundwater table.The objective of the study is to investigate the effect of seepage flows on bed load transport rates through laboratory flume experiments.The experiment focuses on the modification of dune geometry resulting from seepage flows and the celerity or the propagation of the sand dunes.The results show that the influence of flow suction on both dune celerity and height tends to be positive,while the opposite is true for the injection flow.By analysis of experimental flume data for sand dunes,qualifying the effect of seepage flows on bed load transport rates can be carried out.As the result,a modified formula for better estimating the average rate of bed load transport is proposed.
Experimental study on overtopping breaching of noncohesive homogeneous embankment dams
ZHANG Da-wei, HUANG Jin-chi, HE Xiao-yan
2011, 22(2): 222-228.
Abstract:
Most experimental studies on overtopping breaching of embankment dams use small-sized sediment grains and little differences in the diameter profile of sand specimens.Aiming at the issues of sediment sizes,two distinct types of sediments are used in this experimental study.The experiment reveals that the breaching processes of two types of dams are basically identical under relatively strong erosion conditions.During the overtopping event,the down cutting phenomena are most likely observed and the backward erosion phenomena occur only near the crest of the dam.The entire breaching process can be divided into three stages.In the first stage,a headcut is formed near the lower margin of the dam crest.In the second stage,the headcut collapses and the erosion actions become violent.In the third stage,antidunes occur and the erosion actions terminate.Experiments also detect that the downstream slop of the dam has a significant effect on the breaching process.The steeper the slope is,the faster the degradation rate of the crest is and the larger the flood peak discharge is.Moreover,a flat hydrograph is produced by the embankment dam-breach flood,which contains coarse sand particles.The corresponding value of the flood peak tends to be smaller compared to that of resulting from small-sized materials.However,it is worth mentioning that a large difference in sediment sizes will have a limited effect on the peak discharge.
Experimental study of critical flow energy for slope erosion under the influence of vegetation cover
XIAO Pei-qing, YAO Wen-yi, SHEN Zhen-zhou, YANG Chun-xia
2011, 22(2): 229-234.
Abstract:
The critical flow energy for slope erosion is an important characteristic value measuring the erodibility of a soil.Using simulated rain of three intensities(45 mm/h,87 mm/h and 127 mm/h),an experiment study was conducted on the critical flow energy for slope erosion under different underling conditions.The experiments were made for bare soil,grass and shrub slopes of gradient 20°.The result shows that the sediment transport rate can be linearly related to the flow energy and to the fluid shear stress under all underling conditions.Such a linear relation appears to be validated for the unit stream power and the specific energy.The critical shear stress values are respectively 0.86 N/m2,2.86 N/m2 and 1.65 N/m2 for bare soil slope,grass slope and shrub slope; while,the values for the critical unit stream power are 0.003 6 m/s,0.0127 m/s and 0.0169 m/s,and values of 0.074 cm,0.11 cm and 0.13 cm are found for the specific energy.The study reveals that larger critical flow energies would be required for slope erosion under vegetated conditions compared to that of bare soil.The experimental data provides a valuable asset for the mechanism study of water and sediment yields under the influence of vegetation cover,which is important to the ecological rehabilitation projects.
Determination of Brooks-Corey soil hydraulic parameters through vertical infiltration experiments
MA Dong-hao, ZHANG Jia-bao, HUANG Ping
2011, 22(2): 235-241.
Abstract:
A new method is proposed for estimating soil hydraulic parameters in the Brooks-Corey model.The method uses only one-dimensional vertical infiltration experiments,thus,measurement of saturated hydraulic conductivity is not required.The method is tested in two soil textures in Fengqiu County.The result shows that the Brooks-Corey soil parameters estimated by the new method are quite comparable to those of using the horizontal absorption method when the gravitational potential is balanced by the matric potential(capillary potential) and the soil stays wet long enough.Using the estimated parameters,the infiltration process simulated by the Brooks-Corey model is in good agreement with the observation.The new method saves time and effort,and can help to avoid the numerical dispersion problems as well as multiple solutions compared to other methods such as the horizontal absorption method and the inverse parameter method.
Design and simulation of a foreseeable algorithm for canals
SHANG Yi-zi, WU Bao-sheng, LI Tie-jian, WANG Guang-qian
2011, 22(2): 242-248.
Abstract:
Water level hold at specified locations within each reach is of the utmost importance for reliable and efficient management in a channel.A new algorithm for the control of unsteady flows in open channels is presented.An innovative control method is first analyzed,and then synthesized to construct a foreseeable module.The algorithm can thus be obtained by implanting the predicative module into a linear quadratic regulator(LQR).Using LQR,the canal operation problem can thus be reformulated as an optimal control problem,which regulates the gate discharge using the water level error as its constraints.The logical structure of the new algorithm is identified using an impulse response test,and the performance of the algorithm is tested on the platform of the "digital canal of the middle route of south to north water diversion project".The result shows that the algorithm performs well,is able to cope with the planned demand for large quantities of water,and is potentially useful for real applications.
Three-dimensional visualization of temporal and spatial processes of water and sediment simulation for digital river basins
YE Yun-tao, JIANG Yun-zhong, LIANG Li-li
2011, 22(2): 249-257.
Abstract:
Based on a common grid and introducing the particle systems from the field of computer graphics,the paper presents a new method for visualizing the dynamic behavior of simulated water and sediment movements in digital river basin.Some of the key techniques involved in the development of the method are discussed in detail.These techniques are the data structure design for storing particle and grid cell information,the random generation of a particle that is controlled by the computational grid,the local searching and positioning of the particle,the flow field conversion from Euler representation to Lagrange representation using the self-adaptive Runge-Kutta method,and the design of particle shapes with water and sediment information.The issue of the uneven distribution of particles during the course of flow field change has been solved.The new method is tested and applied in the flow visualization system developed for the Yangtze River reach between Three Gorges and Gezhouba.
Application of the radial point interpolation method to numerical simulation of waves
JI Xiao-qiang, FENG Wei-bing, ZHANG Yu
2011, 22(2): 258-265.
Abstract:
Numerical simulation of nearshore waves has become an important topic in coastal dynamics.However,there are certain drawbacks associated with the use of rectangular grids for numerical wave modeling from deep water to shallow water,such as selecting grid resolution and treating complex boundaries.Performing the pre-processing procedure can also be a difficult task to accomplish on an orthogonal curvilinear grid or an unstructured grid.As the result,a radial point interpolation method has been developed recently in computational mechanics.The hyperbolictype mild-slope equation is used to describe wave propagation in shoaling water.The equation is spatially discretized using the meshless method,and the forth-order Adams-Bashforth-Moulton predictor-corrector scheme is employed to perform time updating.A nearshore wave model is thus obtained.The model is tested in an experimental topography consisting of an elliptic shoal and in a circular channel case.The result shows that the meshless method can effectively simulate the nearshore wave propagation with a satisfactory accuracy.The method can better treat complex boundary conditions.
Experimental studies and characteristics analysis of sea ice flexural strength around the Bohai Sea
JI Shun-ying, WANG An-liang, SU Jie, YUE Qian-jin
2011, 22(2): 266-272.
Abstract:
In the oil/gas exploitation of Bohai Sea,the physical and mechanical properties of sea ice are important to determine the design parameters of offshore structures,and also have important influence on the ice dynamics.With the increasing applications of ice-breaking conical structures,the investigation of sea ice flexural strength is more valuable since it is the most important factor to calculate the ice force.In this study,the sea ice flexural strengths were measured in situ and in door around the Bohai Sea at nine sites.Meanwhile the salinity,velocity and loading rate were also measured in the experiments.The characteristics of sea ice flexural strengths were analyzed at the Laizhou Bay,the west shore of Liaodong Bay,and the east shore of Liaodong Bay.Finally,the influences of brine volume(salinity,temperature) and stress rate on the sea ice flexural strength were analyzed.Based on the linear function between flexural strength and stress rate,and the negative exponential function between the flexural strength and the square root of brine volume,a double-parameter equation is established to determine the sea ice flexural strength.This study can be used to determine the ice load on the conical and slope structures in ice-covered regions.
Experimental study on the effect of wave disturbances on the phosphorus dynamics in shallow lakes
DING Yan-qing, ZHU Guang-wei, QIN Bo-qiang, WANG Yong-ping, WU Ting-feng, SHEN Xia, HONG Da-lin
2011, 22(2): 273-278.
Abstract:
An experimental study was conducted in the water flume to investigate the effect of wave disturbances on the phosphorus releasing from the sediment in shallow lakes.The dissolved oxygen(DO)was measured every 5 seconds using an oxygen microelectrode sensor that is located at 1 cm above the sediment-water interface.Two wave amplitudes(2 cm and 10 cm) are used in the experiment.Results show that the strong wave disturbance can result in a rapid increase in suspended solids and total phosphorus concentrations.However,the influence on the soluble reactive phosphorus(SRP) concentration is insignificant.Wave disturbance can significantly increase the DO concentrations on the sediment-water interface and in the overlying water.For example,the observed DO concentration increases from 2.90 mg/L to 4.09 mg/L under the strong wave condition.Wave disturbance also increases DO penetration depth into the sediment.On the contrary,wave disturbance significantly reduces the SRP concentration in the interstitial water from the top 10 cm of sediment.The experiment reveals that the wave disturbance rapidly increases the particulate phosphorus concentration in the water,but has a minimal effect on the SRP concentration.The reason may be due to the complicating factors in controlling the SRP behaviors in shallow lakes.
Advances in the study of projection of climate change impacts on hydrological extremes
YANG Tao, LU Gui-hua, LI Hui-hui, HE Hai, WANG Xiao-yan
2011, 22(2): 279-286.
Abstract:
The study of climate change impacts on hydrological extremes including floods and droughts has been widely recognized as one of the main scientific issues that need to be addressed with priority.This article reviews recent advances in the relevant study with emphasis on the methodologies used for statistical downscaling and the approaches of using rainfall-runoff models to construct extreme scenarios under climate change conditions.The pros and cons of the methodologies and approaches are also discussed in order to propose some novel ideas dealing with hydrological extremes under climate change conditions.As the result,we recommend the use of multi-model ensemble techniques,data assimilation methods,and scale transformation in hydrological modeling.This could potentially reduce uncertainties in the construction of extreme scenarios under climate change conditions.
Review of current research and future directions of low impact development practices for storm water
SUN Yan-wei, WEI Xiao-mei, POMEROY C A
2011, 22(2): 287-293.
Abstract:
The low impact development(LID) approach is an innovative site design strategy offering benefits in utilization of urban storm water and eco-environment protection.The paper introduces the concept,background,design goals and guidelines of LID,and reviews the current research on LID practices,design methods,monitoring and model simulation.Based on the analysis of benefits and limitations of LID,we identify the field monitoring practices,media testing,modeling and watershed retrofit studies as for future research directions.The introduction of LID storm water management practices could be an alternative approach to the utilization of storm water and eco-environment protection in China.
2011, 22(2): 294-294.
Abstract: