Abstract: This paper discusses the seriousness of bank erosion phenomena in the lower Yellow River,and evaluates some current numerical models for simulating the longitudinal and lateral deformations of riverbed.A conclusion is drawn that they are not applicable to simulate the full bed deformation process in the lower Yellow River Finally,a new 2-D composite model consisting of a 2-D-flow sediment mathematical submodel and a riverbank-erosion submodel is established.Through using all kinds of enhanced measures,this model can be used to simulatre both longitudinal and lateral deformations of riverbed in natural rivers,especially in the lower Yellow River.
Abstract: The numerical model proposed in the previous paper is tested in this paper.Through simulating bank retreat processes for a schematic river reach under different bed score and deposition conditions,it indicates that the rate of bank retreat during scouring is greater than that in deposition.Then,the full bed deformation process of the Huayuankou Laitongzhai wandering reach in the lower Yellow River is simulated numerically,and good agreements are obtained between calculated and prototype-measured data such as the water level,velocity fields,and cross-sectional profiles variations.Both examples show that the proposed model is capable of simulating the longitudinal deformation of riverbed,and the process of bank retreat and advance,especially the bank lateral erosion and failure process.
Abstract: Based on the 218 flood events data of the lower Yellow River from 1950 to 1985,different channel transverse adjustment at Huayuankou reaches of the lower Yellow River at rising and falling stages during flood events are distinguished.At the rising stage,the width to depth ratio at Huayuankou reaches exhibits the tendency of generally increasing.The higher the maximum sediment concentration of the flood events,the larger the width to depth ratio.When the flood peak-increasing ratio is lower than 3,the width to depth ratio is in direct rat io to it.When it is higher than 3,the width to depth ratio is in inverse ratio to it.At the falling stage,the situation is just on the contrary When the maximum sediment concentration of the flood events is lower than 15 kg/m3 or higher than 300 kg/m3,the width to depth ratio is in net decrease.When the flood peak-increasing ratio is higher than 3,the width to depth ratio of the most flood events will decrease.The deformation of the channel during flood events is firmly related to sediment concentration.When the sediment concentration of the flood events is low,the decrease of the width to depth rat io is mainly at rising stage.When the sediment concentration of the flood events is high,the decrease of the width to depth ratio is mainly at falling stage.
Abstract: To explore the properties of daily flow variation in the Yangtze River and its prediction by using a new approach, the issue of chaotic properities of daily flow at Yichang station has been addressed systematically and fully.Based on the obtained results,some new models have also been developed.The findings from this comprehensive exploration are divided into several parts.This paper contains the first part,in which the stress is put on optimum determination of delay time.The determination of delay time is very important for chaotic analysis.Two traditional methods(autocorrelation and real vector) are applied to this determination.In addition,a new method,named as general correlation function method,has been put forward. The results show that the general correlation function method is a reasonable and operational method for determination of delay time.
Abstract: To explore the properties of daily flow variation in the Yangtze River and its prediction by using a new approach, the issue of chaotic property of daily flow at Yichang station has been addressed systematically and fully.The findings from this comprehensive exploration are divided into several parts.This paper contains the second part,in which the stress is put on optimum determination of embedding dimension.The determination of embedding dimension is also very important for chaotic analysis.Three methods are applied to this determination.They are saturated correlation dimension,false nearest neighbors and real vector field.Their properties,advantages and disadvantages are analysed in this paper.The results show that the optimum embedding dimension must be determined based on comprehensive analysis and in combination with consideration of optimum wide window.
Abstract: According to the basic idea of pressure correction algorithm for the Navier-Stokes equations,the water level correction algorithm for the shallow water equations is proposed in the paper,which can greatly reduce restrictions on time step.By reconstructing the coefficient matrix of the original algebraic system,a high-resolution finite element scheme based on unstructured grids is established,so that both the requirement of high-order of accuracy and non-oscillatory condition are satisfied.For the sake of convergence or fasting convergence,the friction terms of the momentum equations are transposed and linearized.Comparisons with analytical solutions are made and good agreements are obtained.
Abstract: Flow regime in the mountain river is characterized by its complex boundary topography,fluctuating water level and rapid flow velocity.A two-dimensional horizontal numerical model,which is solved by the mixed five-diagonal finite difference algorithm,is developed for modeling water level and flow velocity in the mountain river.This model is verified by the topographic and depth-averaged flow velocity data from the Jingangbei-Chaoyangqiao section near Chongqing in the Jialingjiang River.Good agreements are found in comparison with the measured water level and flow velocity.
Abstract: Based on exact the Riemann solution,this paper presents a Godunov-type scheme for 1-D shallow-water equations with uneven bottom.Central difference and the Riemann solution with "water level formulation" are used in the discretisation of the source term to keep the scheme well-balanced.Numerical experiments are presented to demonstrate that the scheme is robust,versatile and high in resolution.
Abstract: Mineral nitrogen losses in dryland involve ammonia volatilization,nitrate leaching and denitrification.The objective of this paper is to investigate the relationship between soil mineral losses and soil moisture as well as mineral nitrogen content under water-saving irrigation conditions.The field experiments were carried out in a field with winter wheat and corn for three years.Based on the observations of field experiments and the analysis of relationship among initial soil mineral nitrogen content,irrigation amount,fertilizer supply,and mineral nitrogen losses,a conceptual model is developed to estimate soil mineral nitrogen losses and evaluate the impact of irrigation water and fertilizer N input on the environment.The results show that crop grain yield increased with the increased nitrogen losses.Nitrogen use efficiency is also limited by soil water content under water-saving irrigation conditions.
Abstract: Surface and bottom water samples in the Yangtze River estuary were collected in the summer of 2001,following estuarine mixing procedure.Major ions Mg2+,Ca2+,Na+ and K+ are determined.The results show that pollution has litt le in fluence on pH situation in the Yangtze River estuary.Concentrations of major ions in mixing zone increase with salinity and the ratio of dissolved Ca/Mg decrease.Change in major ions in the Yangtze River estuary can be simulated by a linear mixing model between riverine and sea waters.There is no obvious difference between surface and bottom waters in major ion compositions.
Abstract: Based on optical parameter data of different lake regions from 2001 to 2002 obtained in situ,the zonal distribution, the seasonal variation,the vertical distribution and the daily variation feature of beam attenuation coefficient are analyzed and the causes are explained.The attenuation coefficient,concentrations of chlorophyll-a(Chl-a) and total suspended matter (TSM) of Taihu Lake water and of some abroad lakes water are contrasted,which detailedly expounds the optical properties of Taihu Lake water body.The results show that the zone distribution of beam attenuation coefficient is estuary > Wuli Lake > Lake center,Lake center > Meiliang Lake,Meiliang Lake > Gonghu Lake,and Gonghu Lake > Easter Taihu Lake; the seasonal variations are different because the main affecting factors of beam attenuation coefficient at different zones are different; the beam attenuation coefficient at noon is bigger than that of morning and afternoon; there are two types of beam attenuation coefficient vertical distribution,one of which decreases step by step,the other decreases at first and varies little then; and the spectral properties of beam attenuation coefficient show that it is bigger at short wavelength than that of long wavelength and with a high value at 670nm.
Abstract: Dalian is one of the most important coastal cities in Northern China and famous for its beautiful scenery and its tourism.As is known,the sea around the city comprises the most noticeable advantages.The protection of the ecological environment of the sea is a necessary premise to the development of the social economy of Dalian.However,in recent years,the increase of the quantity of drainage resulting from the development of its economy has led to the deterioration in the water quality in the near sea.It has formed the major problem of ecological environment in Dalian city.Through researches,this essay not only analyzes the variation of water conditions and the causes,but puts forth some measures to improve it.
Abstract: Based on the multi-uncertainty characteristics of river hydrology and water quality information,the blind number theory in unascertained mathematics is used to calculate river water environmental capacity.Through the calculation,not only the expected value of allowable load of a predominant pollutant for a river but also its corresponding confidence level can be obtained.The case study shows that the results received from the unascertained mathematics theory accord closer with practical situation than the traditional method of water environmental capacity calculation.
Abstract: A fractal method is employed to estimate soil hydraulic conductivity from the particle-size distribution data(PSD) in the paper.The pore surface fractal dimension is first determined using the PSD curve,and then used in the fractal conductivity models of Mualem and Burdine to predict the field conductivity function.Compared with hydraulic conductivity obtained from the laboratory water retention curve using the statistical pore-size distribution models,the PSD based fractal method produces much better results for 217 samples from the UNSODA soil hydraulic database.
Abstract: Based on the simulated rainfall experiments,the relationships between the velocity-discharge,depth of runoff-discharge,the velocity-the depth,resistance coefficient with the Reynolds number in rill runoff are established systematically studied; the effects of rain intensity and slope on hydraulic feature,the erosion characteristics of various runoff types and runoff fluidization states and hydro-power elements,and the hydro-driving characteristics and erosion processes in shallow furrow and gully are researched preliminarily.The results are very important to explain the dynamic mechanism of sediment-water flow under various types of gully erosion in erosion chain and occurrence and evolution of soil erosion chain.
Abstract: Based on objective satisfaction degree and objective comprehensive degree,a new interactive multi-objective decision-making method is proposed.The function of objective comprehensive degree is described by the Euclid distance,so that the objective weight,usually given by subjective experience,can be avoided.The new method can reflect the objective wishes of the policy-maker in the full decision-making process,and there is more objective and less subjective effect.The results show that this method is reasonable in practice,and can be used in water resources system planning.
Abstract: The evaluating methods for the flood non controlling structures under influence of flood involve direct and indirect economic losses computation approaches,the environmental pollution assessment methods for contained-toxicant structures,and ground water pollution of contained-toxicant structures.These methods are key techniques of influences of flood on flood non-controlling structure Based on the methods mentioned above,the national guidebook or criterion for flood effects on flood non-controlling structures can be worked out.
Abstract: A method for creating a long range flood prediction model is developed by using the principal components of factor field.First,the principal component of fields of 500 hPa height and Pacific sea surface temperature which have important effect on rainstorm and flood of region are analysed with their principal component as predictor.Then,compulation of correlation and stepwise regression is operated to creat the model.The compulation procedue are quite complete.Applying that model to predict the yearly maximum stream content of Beijiang River flow region shows that the model is effective.
Abstract: The paper selects seven indexes that depute the development of nine cities in Jilin province to analyse quantifica-tionally the status of sustainable utilization of city water resources in this region,filters three main factors from the seven indexes by the factor analysis method,water pollution and discharge,water environmental quality and water resources factor,and assesses the harmony degree of these three main factors by the analytic hierarchy process method.On the basis of assessment, suggestions for sustainable utilization of water resources in Jilin province are provided.
Abstract: This paper introduces the advances and status in research of various direct methods(include two categories,i e, laboratory and field methods) and indirect methods such as the Pedo transfer function,the Fractal,the Morphology,the Numerical inverse method and the empirical formula etc.for determining soil hydraulic properties,including their inherent advantages and deficiencies.In order to extend the application and enhance the prediction accuracy,new experimental techniques need to be cont inuously introduced and measurement instruments improved.Concurrent ly,the comprehensive studies integrating all theoretical and experimental information relevant to the prediction of unsaturated soil hydraulic properties should be carried out.
Abstract: For about thirty years,along with the increasingly groundwater pollution,the investigators have paid more and more attention to the solute transport in fractured media,especially a single fracture.They have done many laboratory and field experiments and made some responsible mathematic models.Papers on solute transport in a single fracture in literatures are col 2 lected.From these papers the fundamental properties of the transport are summarized and the related experiments are compared and analyzed.With all these experiments,several important factors which influence the process of solute transport in a single fracture are concluded,such as matrix diffusion,dispersion,surface sorption,etc.This paper also presents some typical mathematic models,and discusses the validity and limitation of these models.
Abstract: The studies on numerical simulation of contaminant transport and flow in North China type fracture-karst media last decades are reviewed,the numerical methods and computational techniques which have been developed to solve problems of contaminant transport and flow are examined.The key and well-noticed problems in connection with the numerical simulation, which include parameter identification and scale effect,numerical dispersion and libration,non-Darcy flow and Non-Fickian transport,study of stochastic methods,and so on,are highlighted.Attempts have been made to compare and contrast representative numerical methods,and the direction for future research is suggested.
Abstract: Soil water is the primary limiting factor for crop growth,vegetation rehabilitation and eco-environment construction Hillslope soil water movement and transformation is reviewed,including rainfall infiltration and soil water redistribution,soil water transformation,and soil water dynamic change For a successful project of vegetation rehabilitation,soil-plant-atmosphere on the hillslope should be considered to be a physical continuum,and its interfaces of water movement and transformation should be studied based on the processes and mechanisms of atmospheric water,surface water,plant water,and soil water.
Abstract: The hydrological process plays an extremely important role in wetland formation,development,evolution and disappearance.Although many hydrological models on precipitation interception,streamflow and evapotranspiration have been developed,they need to be verified and improved.Sheet flow is difficult to model and calculate due to many factors affecting it.Furthermore,the groundwater system of wetland is especially important for seasonally flooded wetlands.The vertical hydraulic linkage in peatland is still uncertain.In addition,human activities and climate changes must be brought into integrated hydrological models for sustainable wetlands management.So far,there are only few integrated wetland hydrological models.The main study direction in wetland hydrology is to reinforce wetland hydrological monitoring,combine multiple approaches and modern technologies and develop integrated wetland hydrological models.
Abstract: This paper summarizes the research of robuast estimation theory,introduces the fundamental theories,methods and characteristics of robust estimation,and analyses its application situation in hydrology.Some problems worth to further more study are also put forward.