• 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

2010 Vol. 21, No. 2

Display Method:
Mechanism of channel pattern changes and its numerical simulation: Ⅰ. Numerical model
ZHOU Gang, WANG Hong, SHAO Xue-jun, JIA Dong-dong, HU De-chao
2010, 21(2): 145-152.
Abstract:
In this paper,an improved two dimensional (2-D) numerical model for river flow,sediment transport and bank erosion is presented and applied to study the mechanism of channel pattern changes.The effect of secondary flow at river bends is taken into account in the 2-D model by adding a dispersion stressterm in the momentum conservation equation of river flow.The 2-D model simulations were compared with the laboratory experiments conducted in a curved flume,as well as with the field measurements from a long river section between Shashi and Shishou in the upper Jingjiang Reach of the Yangtze River.The laboratory comparison result reveals that the 2-D model in simulating the bank failure calculation is improved in comparison with other commonly used methods.The results also show that the 2-D model is able to simulate the field measurement.The imp roved 2-D model is relatively simple,easy to use,more reliable,and can be better to simulate fluvial processes in natural river channels compared to classical methods.
Mechanism of channel pattern changes and its numerical simulation: Ⅱ. Application
ZHOU Gang, WANG Hong, SHAO Xue-jun, JIA Dong-dong, HU De-chao
2010, 21(2): 153-160.
Abstract:
An improved two dimensional (2-D) numerical model for river flow,sediment transport and bank erosion is presented and tested in Part Ⅰ of this paper series.Using the 2-D model,a series of numerical experiments are further carried out in an idealized river channel with different variations of channel patterns in this study.The impact on channel pattern changes by various factors,such as initial channel slope,sediment supply,water discharge,and resistance to bank erosion is studied using the model simulations.The numerical results of river channel planform change,longitudinal bed profile,channel cross section,water surface profile and channel sediment transport are analyzed and discussed.The channel patterns simulated by the improved 2-D model agree well with the classic theory of channel pattern formation.
Three dimensional numerical simulation of external flow field around tetrahedron frame with a single attached wall
GAO Zhu, YIN Jie, TANG Hong-wu, GUO Hong-min
2010, 21(2): 161-166.
Abstract:
The Tetrahedron Frame Groups (TFG) protection method,a new engineering measure to prevent bank erosion and promote sediment deposition,has been widely adopted in many river engineering practices in China.However,due to the unique geometric forms of TFG,it is difficult to measure the external flow in TFG,which limit further understanding about the mechanism of the TFG protection method.A three dimensional (3-D) hydrodynamic model is developed on the platform of the Computational Fluid Dynamics (CFD) platform fluent to simulate the external flow field and drag around the Tetrahedron Frame (TF) with a single attached wall in clear water environment.The simulation results are compared with the Acoustic Doppler Velocimetry (ADV) experimental measurements.The result shows that the 3-D model can effectively supplement the experimental study of the complex flow fields,which provides valuable information for the mechanism study of the TFG protection method.Giving different values of hydraulic parameters,the diagram of drag coefficient CD vs Reynolds number Re is obtained using the 3-D model.The diagram shows that the drag coefficient in TF with a single attached wall tends to be a constant value of.1.557 when the Reynolds number is larger than 105.
Numerical model for dam-break flow based on Godunov method
ZHANG Da-wei, CHENG Xiao-tao, HUANG Jin-chi, HE Xiao-yan
2010, 21(2): 167-172.
Abstract:
In order to better understand the risk of dam-break flooding and to reduce the potential of live and property losses,a Godunov-type coupled numerical model based on one dimensional (1-D) and two dimensional (2-D) modules is developed to simulate different dam-break flows.The Harten-Lax-van Leer (HLL) scheme is used in the 1-D module; while,the Roe's method is adopted in the 2-D module for unstructured meshes.The 1-D and 2-D modules are coup led using an overlapping-region method for exchanging the key hydraulic information.The model is tested with two experimental cases of dam-break flow in the curved channel and in the straight channel with sudden enlargement.Results show that the coupled numerical model is able to simulate the dam-break flow of the two cases with good reliability and applicability.The model has the potential for practical applications in simulating large scale dam-break floods.
Distributed rainfall-runoff simulating based on cellular automata for small watersheds
TANG Fu-ping, LI Man-chun, QIN Fen
2010, 21(2): 173-178.
Abstract:
A distributed hydrological model based on cellular automata (CA) is developed to simulate the rainfallrunoff process in small sized watersheds.The distributed model is built by extending cellular states and transformation rules,as well as the time step in the general CA model.The model consists of five substates with five cellular parameters and two transform ation rules,and is fully integrated with a geographic information system (GIS) platform.The model is validated using the observed rainfall-runoff data from the Chabagou watershed in the Loess Plateau region of the Yellow River Basin.The results show that the three evaluation indexes,the deterministic coefficient,the peak time error and the peak forecast error,all reach certain accuracy.The simulated runoff process can also be visualized on the GIS platform.The CA based distributed hydrological model shows potential efficacy of simulating event based rainfall-runoff processes in small watersheds.
Order statistics in flood frequency analysis
LIU Jiu-fu, XIE Zi-yin, BAO Zhen-xin, ZHU Yuan-sheng
2010, 21(2): 179-187.
Abstract:
In this article,the definition,sampling distribution and its statistical characteristics of order statistics and generalized order statistics in flood frequency analysis were systematically presented,and then the sampling distributions,the statistical characteristics and the relationship of them were studied with the mathematical experiment and Monte Carlo method.The relationships between expected value,median of order statistics and generalized order statistics will establish the base of theory for systematically analyzing and evaluating the curve-fitting method.
Regional drought analysis approach based on copula function
LU Gui-hua, YAN Gui-xia, WU Zhi-yong, KANG Yan-xia
2010, 21(2): 188-193.
Abstract:
A regional drought index is proposed,which can take into account sub-grid variations in drought severity as well as in drought disaster area.The Copular function is used to establish the joint distribution of drought duration and severity over a region.There turn period of the joint distribution can be used to study the characteristic of historical drought events and estmi ate the current drought return period.The index is applied to study the 2006 droughtevent in Chongqing,southwest of China.The resultrevea ls that the drought development can be adequately reconstructed using the index.The drought characteristics,such as intensity and duration,can also be well quantified by the index.The calculated return period of joint distribution for the 2006 event is 118 years,which reflects the observed reality from the drought disaster.The result demonstrates the miportance of considering the sub-grid drought variations and the significance of using the joint distribution in the estab lishment of the index.The index can thus have the potential of representing the severity of a regional drought in a comprehensive manner.
Spatiotemporal variability of reference evapotranspiration over the Northeast region of China in the last 60 Years
ZENG Li-hong, SONG Kai-shan, ZHANG Bai, WANG Zong-ming, DU Jia
2010, 21(2): 194-200.
Abstract:
Based on the daily meteorological measurements of 106 meteorological stations in Northeast China from 1951 to 2007,the daily reference evapotran spiration (ET0) and yearly ET0 are estmiated using the Penman-Monteith equation1 Gridded annual and annual-average ET0 values for the region are produced using the inverse distance weighted interpolation method.The spatiotemporal variability of ET0 is analyzed using the methods of Mexican hat wavelet transform,Mann-Kendall test,the rotated empirical orthogonal function,and the inclination rate.The results show that:(1) a slightly increasing trend (3.89 mm/10a) is detected in the regional-average ET0 tmie series,and the regional ET0 minmium and maxmium are found in 1953 and 1982,respectively; (2) the temporal variability of regional-average ET0 has a quasi-periodicity of 8216 years experiencing four alternating stages (low-high-low-high),and in which an intensified ET0 oscillation of 8210 years is observed; (3) the annual-average ET0 ranges from 600 mm to 1.60 mm,and appears as obviously spatial difference exhibiting semiring-shaped isogramswith a gradual ET0 increment from Northeast to Southwest; and (4) the annual-average ET0 shows a increase trend over 72161% of the region doma in based on the analysis of inclination rate,while the opposite result is obtained for the rest of the region; the maxmium and minmium values of inclination rate are 3016 mm/10a at Nenjiang station and 224.4 mm/10a at Yebaishou station,respectively.
Validation of soil moisture retrieval in arid and semi-arid areas
LI Qin, CHEN Xi, Frank Veroustraete, BAO An-ming, LIU Tie, WANG Jin-lin
2010, 21(2): 201-207.
Abstract:
The objective of this study is to present an approach based on the thermal inertia approach to estimate the profile of soil moisture content (SMC) in the top 1m soil column using Moderate Resolution Imaging Spectroradiometer (MODIS) imagery.In the approach,both diurnal Land Surface Temperature (LST) difference and broadband albedo (α0) are used to determine the spatial-temporal variation of SMC.The SMC retrieval rationale is that the high Apparent Thermal Inertia (ATI) values represent the high soil moisture contents,and the opposites are true for the low ATI values.The approach assumes that the water flux in the top 1m soil column is proportional to the difference in SMC at the surface and bottom of the soil column.The water balance equation can then be applied over the soil column,which results in the establishment of a relationship between the areal mean of SMC in the soil column and the remotely sensed surface SMC.The established SMC relationship is calibrated using the experimental data and a new soil texture classification technique based on the existing Chinese soil type classification.The SMC relationship is validated over a typical arid and semiarid area in Xinjiang.The observed soil texture data is used in the app lication of the SMC relationship.Results show that the SMC relationship has the best performance for the loam and loamy clay types of soils,as the values of estimated SMC are very much close to the Time Domain Reflectometry (TDR) observations.In comparison with the TDR observation,amarginal relative error of 2.16% is found in the estimated SMC in a subarea with the sandy type of soil1 Our result demonstrates the potential of using the established SMC relationship to map the spatial-temporal variation of SMC in the top 1m soil column using the MODIS imagery over arid and semi-arid areas.
Correcting the smoothing effect of ordinary Kriging estimates in soil moisture interpolation
YANG Yu-ting, SHANG Song-hao, LI Chao
2010, 21(2): 208-213.
Abstract:
Ordinary Kriging of geostatistics is an effective tool in studying the spatial variability of soil moisture and describing its spatial distribution.Like other interpolation methods based on the criterion of least-squares,ordinary Kriging estimates present a serious inherent drawback well known as the smoothing effect with decreased variation of estimates.In this study,the post-processing approach of Yamamoto is used to correct the smoothing effect of ordinary Kriging estimates in observed soil moisture interpolation.The result shows that the Yamamoto's approach can effectively correct the smoothing effect,and the real soil moisture spatial distributions can thus be preserved without losing local accuracy.
Spatial variability of soil infiltration characteristics and its pedo-transfer functions
LIU Ji-long, MA Xiao-yi, ZHANG Zhen-hua
2010, 21(2): 214-221.
Abstract:
Based on the experimental data collected from the first terrace in Yangling station,we perform both multifractal analysis and jointmultifractal analysis to investigate the spatial variability and relationship between the stable infiltration rate and soil infiltration characteristics,and establish the pedo-transfer functions (PTFs) of soil infiltration characteristics.The results show that the infiltration characteristics are multifractal.The observed spatial variability of stable infiltration rate and the beginning 30-min cumulative infiltration are mainly caused by the different sand and clay contents in the soil samples.The multi-scale analysis results show that the spatial variations of soil sand content and organic matter content have significant influences on the spatial variability of steady infiltration rates.The beginning 30-min cumulative infiltration is mainly affected by the distributions of slit and clay content which are the same factors in multi-scale as the observation scale.Two pedo-transfer functions of infiltration characteristics are established with the joint multifractal analysis and the beginning 30-min cumulative infiltration,respectively.The computational error of the former is less,the later is relatively larger.
Soil moisture retrieval from multi-resource remotely sensed images over a wheat area
ZHANG You-jing, WANG Jun-zhan, BAO Yan-song
2010, 21(2): 222-228.
Abstract:
The aim of this study is to use the multi-resource remotely sensed images over land surfaces in a semi-arid region in northern China to infer the soil moisture content (SMC) in the presence of wheat.The multi-images include Advanced Synthetic Aperture Radar (ASAR),Landsat Thematic Mapper (TM) and Moderate-resolution Imaging Spectroradiometer (MODIS).The influence of vegetation on the satellite signal can be described by a water-cloud model.The vegetation water content (Mv),an important parameter in the water-cloud model,was synchronously measured with the corresponding satellite passes over the wheat area.The evaluation of the relationship between Mvand four satellite-derived vegetation indices (VIs) shows that the NDWI (normalized difference water index) from TM has the closest relationship with Mvas revealed by the correlation coefficient of 0.87.Based on the established Mv-NDWI relationship,combining the water-cloud model with the soil moisture retrieval over bare soil conditions,a semi-empirical model is developed for estimating SMC over a wheat area.A sensitivity analysis is also performed on the model parameters.In comparison with the insitu soil moisture observation,a satisfactory result is obtained in the soil moisture retrieval using the semi-empirical model as revealed by the RMSE (root mean squared error) of 3.83% and the correlation coefficient of 0.9.The spatial distribution of soil moisture deficits in the study area is also produced.
Characteristics of interflow in purple soil of hillslope
XU Qin-xue, WANG Tian-wei, LI Zhao-xia, CAI Chong-fa, SHI Zhi-hua
2010, 21(2): 229-234.
Abstract:
The interflow constitutes an important portion of total runoff in purple soil of a hillslope.A series of artificial field simulation experiments were conducted to explore the characteristic of interflow in the purple soil of hillslpoe in the different rainfall intensities and land surface conditions.Experimental results show that the observed runoff coefficient and the average interflow for the interflow on undisturbed wastelands are 3 to 15 times and 7 to 33 times that of the observed on bare cultivated lands,respectively.Such characteristic differences in interflow generations on the two lands will become more evident with the increase of rainfall intensities.The observed runoff coefficient for the interflow on bare cultivated lands decreases significantly with the increase of rainfall intensities,while such a characteristic of interflow is not found on undisturbed wastelands.Interflow generations on undisturbed wastelands vary with land surface conditions such as soil compactions and vegetation densities.Surface soil compaction due to heavy rainfall and the decrease in vegetation cover will contribute to a significant reduction of interflow generations on undisturbed wastelands.
Influence of controlled irrigation on CH4 and N2O emissions from paddy fields and subsequent greenhouse effect
PENG Shi-zhang, YANG Shi-hong, XU Jun-zeng
2010, 21(2): 235-240.
Abstract:
The methane (CH4) and nitrous oxide (N2O) emissions from controlled irrigation paddy fields were observed by using the static chamber gas chromatography (GC) method.The objective of the study is to investigate the influence of the controlled irrigation technique on the CH4 and N2O emission process and the subsequent greenhouse effect.The results show that during a life cycle of rice crop,the total CH4 emission from the controlled irrigation paddy field can be reduced by as much as 73.2% to 85.0% compared to that from the flood irrigation ones,and the emission is found to be most active in the early to mid-tillering stage of rice growth.By contrast,controlled irrigation would lead to a 10.6% increase in the total N2O emission from paddy fields during the most tmie of rice growth.The average N2O emissions from controlled and flood irrigation paddy fields are 106.65mg/m2 and 96.40 mg/m2,respectively.It is estmiated that the global warming potential (GWPs) contributed by CH4 and N2O emissions from controlled irrigation paddy fields would be 726 kg/hm2,which should result in a 59.1% emission reduction compared with that from flood irrigation ones.Our study suggests that using the controlled irrigation technique would significantly reduce CH4 and N2O emissions and the subsequent GWPs.
Field survey and analysis of influence of suspended sediment on algae growth
ZHU Wei, JIANG Mou-yu, ZHAO Lian-fang, TIAN Tao
2010, 21(2): 241-247.
Abstract:
A field survey was carried out in Neijiang that is an oxbow lake located within the Zhenjiang-Yangzhou segment in the lower reach of Yangtze River.Sediment concentrations,water transparency,underwater light intensity,algae species and biomass in the oxbow lake were monitored periodically.The observed data were analyzed.Results show that fine suspended particulate matters with the granular size less than 75 μm can constitute more than 80% of the total suspended sediment load in the lake; among which,clay grains account for 20%-50% of the fine suspended sediment.The mean values of sediment concentration in the lake are 40mg/L and 70mg/L for low and high water period,respectively.The gross algae biomass is basically within 100×104 cell/L and dominated by green algae species.The light attenuation resulting from the suspended sediment load in the lake obeys the exponential law,and the relationship of green algae biomass and sediment concentration is also exponential.The diffuse attenuation coefficient appears to be linearly correlated to the sediment concentration.We thus conclude that the suspended sediment can inhibit the algae reproduction process through indirectly declining the underwater light intensity.Such an inhibition can be quantified by the relationship of algae cell density and sediment concentration.
Carrying capacity of water environment in the Huaihe River basin
DOU Ming, ZUO Qi-ting, HU Rui, LI Gui-qiu
2010, 21(2): 248-254.
Abstract:
A compound model for studying interactions amongst socioeconomics,water resources,and water environment in the Huaihe River basin is developed based on the determinate notion of carrying capacity of water environment.According to the constraint conditions of supporting the maximum size of socioeconomic activity in a region,maintaining good water environment,the compound system and the water availability,etc,a zonal water environment carrying capacity model is developed.The carrying capacity evaluation method and criteria are also proposed.The zonal model is applied to 71 computational elements in the Huaihe River Basin,and the results of carrying capacity of water environment are assessed using the proposed evaluation method and criteria.
Diffusive boundary layer and its resistance on salt release from deposited sediments in a polder reservoir
GAO Zeng-wen, ZHENG Xi-lai, ZHAO Quan-sheng
2010, 21(2): 255-260.
Abstract:
The diffusive boundary layer (DBL) is a zone for exchanging matter across sediment-water interface between the mixture of solid sediment and interstitial water from an overlying body of water.The exchange of substances between deposited sediments and overlying water must also pass through the DBL.In this study,two series of flume experiments with and without wind blowing conditions were conducted to study the salt release process from sandy sediments in a polder reservoir.The thickness of DBL was directly measured.The experimental salt fluxes through the DBL under the two wind conditions were inter-compared and compared with the estimations using the Fick's first law in an effort to explore the role of DBL in contact inhibition of salt release.Results indicate that the observed salt fluxes under the two wind conditions show a marginal difference.Under the steady wind condition,a DBL with a constant thickness of 3.5 cm is observed right above the deposited sediment.The molecular diffusion is found to be the dominant mechanism for salt transport within the DBL.The latter can suppress the hydrodynamic enhancement on the exchange of substances between deposited sediments and overlying water.The thicker the DBL is,the stronger the inhibition will be.Thus,the presence of DBL in a polder reservoir can result in a delay of natural clearing process of polluted water.The effect of salt release from deposited sediments on the water quality will be a long lasting process.
Phase modulation of short wind waves by long waves
CONG Pei-xiu, ZHENG Gui-zhen, PEI Yu-hua
2010, 21(2): 261-266.
Abstract:
Laboratory Experiments were conducted in a water-wave tank to explore the phase modulation of short wind waves in particular in their high-frequency spectrum by monochromatic,mechanically generated long waves (LW).Using the intrinsic mode decomposition (IMD) method,the observed surfacee levation tmie series is decomposed into a set of intrinsic mode functions (MIFs) that can be related to short wind waves with different oscillation scales,and the squared amplitudes of MIFs are phase averaged along the profile of LWR esults show that the energy distributions of short wind waves with different oscillation scales present different characteristics.The dominant wind wave energy decreases with the increase in the LW steepness,which is distributed in-phase with the LW and symmetric with respect to the LW trough.In contrast,the mesoscale wind wave energy increases with the increase in the LW steepness.The energy of the upwind quadrant of the LW is slightly higher than that of the downwind one.Finally,the energy of high frequency wind waves also increases with the increase in the LW steepness,but decreases with the increase in the fetch length.The energy of the upwind quadrant of the LW is significantly higher than that of the down wind one.
Hydrodynamic mechanism of evolvement trends in radial sandbank of South Yellow Sea, China
CHEN Ke-feng, LU Pei-dong, WANG Yan-hong, YU Guo-hua
2010, 21(2): 267-273.
Abstract:
The recent studies show that the water channels and sandbanks in radial sandbank of South Yellow Sea (SYS) have been gradually migrating southward.Hydrodynamic analysis on the mechanism of such evolvement trends is thus crucial for the regional development in the coastal zones of Northern Jiangsu province.In this study,the staged evolution of coastlines and seabed topographies since the northern retrieval of the Yellow River estuary is first studied,and a numerical tidal wave model is then established to investigate the hydrodynamic characteristics of the tidal wave system in SYS and evolutions of the Yellow River delta in the different stages.The results show that because of the coastal zone erosions and vanishing of the delta formed by the abandoned Yellow River estuary in Northern Jiangsu province,both tidal elevation and hydrodynamic condition in radial sandbank of SYS have been strengthened,and the strengthened regions are found to be gradually migrating southward.The large-scale southward regional reinforcement of dynamic axis of flow is likely to be one of the major contributing factors causing the entire sandbar regions of SYS migrating southward.
A review of hydrological uncertainty analysis based on Bayesian theory
LIANG Zhong-min, DAI Rong, LI Bin-quan
2010, 21(2): 274-281.
Abstract:
The hydrological system is extremely complex.The hydrological process in a region is mainly determined by natural conditions and human activities on the region.Both determ inistic and stochastic hydrological processes often coexist in the system.The uncertainty analysis in hydrological modeling plays a vital role in searching for regularities of hydrological processes.The Bayesian theory is one of the most widely used approaches to analyzing uncertainties in hydrological modeling.In this paper,we review the recent progresses on the application of an app roach in hydrological frequency analysis,flood forecasting,as well as the coupling of deterministic and stochastic methods.Perspectives and recommendations on the subject are also provided.
Advances in the assessment of ecological water requirements in estuaries
SUN Tao, XU Jing, LIU Fang-fang, ZHAO Rui, YANG Zhi-feng
2010, 21(2): 282-288.
Abstract:
Effects of freshwater inflow on water environment and biological processes in the estuarine ecosystem are analyzed by considering the great diversity of influencing factors with a significant temporal and spatial variability under the interaction between river and ocean.The methods for quantifying environmental flows are divided into three types based on different ecological objectives,which include biological resources objectives,habitat objectives,and integrated multi-objectives.Research progresses are reviewed for different types of methods in this study.The main challenges are discussed according to the objective op tim izing,the relationship between objectives and freshwater in 2 flow,and the limited availability of different methods for the environmental flow assessment in estuaries.The results indicate that identifying an index of the ecosystem health could serve as a scientific foundation for determining environmental flows.Ecohydrological modeling based on the key elements of the estuary ecosystem could be an effective approach in determining environm ental flows in estuaries.