Abstract: Based on view of the probability theory, probability explanations of net tainfall process over watershed and discharge hydrograph of watershed outlet are given.On the basis of these, the convolution integral equation is derived by theory of distributed function of random variate in probability theory, and probability meaning of the instantaneous unit hydrograph (IUH) of watershed is again obtained under obviouser conditions.Equivalent relationship among first order moment about the origin of IUH of watershed, lag time of watershed and average concentration flow time of watershed is proved, and a computational method of average concentration flow time of watershed is given.Finally, two methods of determining the IUH of watershed are presented by means of probability theory.
Abstract: According to the characteristics of the water and land resources utilization of arid plain oasis, a hydrological model based on agriculture area soil water movement is established.The water movement and exchange in deferent media and phases are investigated, and the influences of human activities such as irrigation, exploiting groundwater are also taken into consideration.The model divides the research area into five water balance modules : river module, spring-well module, reservoir-lake module, agriculture area module and non-agriculture area module, and the water exchanges between these modules are made through surface channel and groundwater movement.The model can analyze the main runoff-evaporation in an oasis such as the evaporation or evapotranspiration in agriculture area, non-agriculture area, and the groundwater transfer between agriculture area and non-agriculture area.
Abstract: Based on the research on the pilot of Akesu River basin oasis in northwest China, this paper introduces the development and application of the runoff-evaporation hydrological model for arid plain oasis.An anatomization on the relative analyzed results is also provided.It is found that the modeling results fit the water monitoring results well with efficiency value greater than 90% and multi-year average relative error value of 3.6%.The case study indicates that the runoff-evaporation hydrological model works well in arid area, more applications of the model in northwest China may be possible.
Abstract: A 1-D and 2-D zonal coupling solution method for flow and sediment transport in estuaries is proposed.By defining f ictit ious domain at the interface of different computational sub-domains and making use of the characterist ics of non-structured meshes and element assembly procedure of the finite element method, a strong zonal coupling algorithm is established which puts all the influence coefficients of the 1-D and 2-D linking nodes into the fictitious nodal elements in the global matrix of the system equations.Compared with conventional zonal coupling algorithms which usually use simple matching conditions, the developed method can greatly improve the calculat ing stability.Finally, the algorithm is applied to simulate flow and sediment transport in an estuary.The results agree well with the measured data, and large time step can be achieved, which shows that the proposed algorithm is correct and reliable.
Abstract: The flood with hyperconcentration in the midstream Yellow River frequently causes the bottom tearing scouring.Based on the analysis of the bottom tearing scouring,this paper sets up the physical mode about the bottom tearing scouring and derives the mechanics equation of the bottom tearing scouring and the critical condition of the water and sediment,and the results of calculation agrees with the measured records.Based on the analysis of the equation and condition,the starting current velocity formula about the pill sediment is further pnwed.The twa formulas derived possess important theoretical value to the research of river floor variation and sediments starting caused by the flood with hyperconcentration.
Abstract: Flow in the Yellow River carries sediment in high concentration,and most of sediment transport occurs during the summer time.As the result the calculation of unsteady sediment transport is one of the most important tasks in the Yellow River.This paper presents the unsteady sediment concentration formula accounted for realistically in a model that has predictive power.Applications of the model to Sanmenxia resemvir are shown and compared with field measurement whenever possible.
Abstract: A numerical model to simulate sediment transportation and riverbed variation in river networks is presented.Flow simulation is based on commonly used the gradation method,in which the matrix formed junction equations are divided by subarea groups.For simulation of sediment transportation process,several methods are compared to describe sediment diversion at the junction nodes,together with analysis of their advantage and suitable situation in application.By means of the sediment diversion methods,sediment transport equations can also be solved by the gradation method with the divided junctions groups.The technique to handle junction nodes in which water and sediment deposition can be stored is also discussed for applying to flood retarding basin.Finally,with the data of Dujiatai retarding basin in Hanjiang River,the validity of the model is checked,and the result shows that the model can be applied in wide practice and is worth recommending.
Abstract: The mean velocity characteristics of turbulent jet interacting with surface standing wave were studied experimentally.The experiments were performed in a square water tank.The turbulent jet was driven by a constant head water tank, and the surface standing wave was generated by a plunger-type wave maker.The jet nozzle was positioned under the antinode of the standing wave.The wave amplitude was measured with a capacitance wave gage and the data acquisition system.The velocity profiles were measured with a laser doppler velocimeter.Based on the measurements, it was concluded that the generated waves were nearly perfect standing waves, and the results of turbulent jets were well consistent with the published one.The measurement results of turbulent jet interacting with surface standing water wave indicated that the velocity profiles of the turbulent jets in the momentum-dominated far field were still Gaussian, the imposition of the wave oscillations was to deform the jet structure from circular to elliptic, and the wave oscillations enhanced greatly on the jet mixing.
Abstract: The long non-linear waves in shallow water propagation is studied experimentally and numerically.Fnrst order and second order incident boundary condition on fixed incident boundary are derived for numerical simulations,based on the cnoidal motion of wave maker paddle,which shows that the prediction with second order incident boundary condition is more accurate than the prediction with first order incident boundary condition.The Fourier analysis of measured and computed time history of water elevations with second order incident boundary condition shows that there is periodic transformation for different component of waves along wave flume,while no periodic transformation with first order incident boundary condition.
Abstract: The standard k-ε turbulence rmdel was used to simulate turbulence characteristics of submerged hydraulic jump with the Froude number 8.19 and submergence factor 0.24.The tracking method of the moving free surface was investigated.The numerical predictions including surface profiles,hydrodynamic pressures,mean velocities and turbulence intensities were presented and compared with available experimental data.They provide insights into both the macroscopic structure and the turbulent structure of submerged hydraulic jumps.
Abstract: The distributed sediment samples in the Xuanwu Lake were collected to analyze the influence on the water quality of nutrient layer distribution condition in sediments and its physical and chemical characteristics.Through the dynamic water exchange experiments,we estimate and rmdel quantitatively the releasing process of nutrient from the sediments,the influence mechanism of consequent concentration variation of T-P and T-N in above water to the interfacial material exchange correlation of the Xuanwu Lake eutmphication.The research results show that even if the pure water is used to exchange the polluted water in the lake,after a long time exposure of surface layer sediment,a great deal of organic and integrated nutrients wauld degrade into inorganic nutrient.In the early exchanging of lake water the released T-P and T-N increase continually acting as the service to inter pollution sources.This is mainly owing to the vertical distribution of T-P and T-N in the bed sediment collected during the dry period of the Xuanwu Lake.In the long run,the concentration of T-P in the above water will maintain at a high level of 0.1mg/L.The above research results provide theoretical and practical basis for relevant ecological restoration project.
Abstract: An unsteady water quality rmdel for looping river network is developed for water pollution control planning of the Wenruitang River basin in Wenzhou City.It is based on the Saint Venant equations and the conceptual model(the contunuously stirred tank reactor,CSTR).The rmdel is made up of the hydrological sub-rmdel and the water quality submodel.It can show the dynamic changes of COD,ammonia-nitrogen and DO in the river network.With the model,water environmental capacity of Lucheng river network is estimated.The short-term and long-term pollution control objectives are also worked out.After the study on characteristics of water quality restoration,it can be concluded that the irregular measures such as polluted watercourse flushing and aeration could be taken.Furthermore,nine scenarios on polluted watercourse flushing are analyaed quantitatively,and river reaches required aeration are screened out,too.
Abstract: Changes of the erosion type and the rill erosion process under simple rainfall is one of the key problems in soil erosion research.By placing rare earth elements(REE) on different soil depth across the slope,the simulated rainfall is applied to study the change of erosion type and the rill erosion process.The results indicate that the main erosion type is sheet erosion at the beginning of the experiment,and serious erosion happens after the rill erosion appears.Accumulated the sheet erosion amount and rill erosion increase with the rainfall time,and the increase rate of the latter is bigger than of the former.The ratio of sheet erosion to total erosion decrease and the ratio of rill erosion to total erosion increases with the time passing by.At the end of the experiment,the rill erosion amount reaches 2 to 4 times of the sheet erosion.In this paper,a new REE tracer method is proposed to quantitatively distinguish the sheet erosion amount and the rill erosion amount.Also it can be used to study the process from sheet erosion to rill erosion,and it would be a new method to study the erosion process on slope.
Abstract: The multiple objective decision making-ideal point method,which is applied in water environmental quality assessment,is discussed in this paper.Since the assessment standard actually is not a point but an interval,a defect exists in the traditional multiple objective decision making-ideal point method which deals with the assessment standard by using ideal point.In order to overcome the defect,a new method,multiple objective decision making-ideal interval method (MODMIIIM), is suggested and its constitutional principle and method are given for assessing the water quality.The result shows that the MODMIIM is easier and more available than the projection pursuit model and the neural network method,more rational than the traditional ideal point method.It is a superior assessment method for various comprehensive assessment problems about water environmental quality.
Abstract: A model for the unsaturated soil hydraulic conductivity is established based on an assumption that the soil can be represented as a continuum fractal porous medium.The model contains three physical parameters : a coefficient λ, the fractal dimension D and the critical volume fraction αc.The saturated and unsaturated hydraulic conductivities are connected by the parameter λ.The fractal dimension (D) represents the soil porous structure and the critical volume fraction (αc) which accounts for the differential porosity from the smallest pore size for continuous flow to the largest pore size in the soil.The unsaturated soil hydraulic conductivity estimated by the model is compared with the experimental data of various soils.
Abstract: The waterrock interaction(WRI) process is a stochastic one.The mathematical model of WRI is set up on the basis of principles of chemical therm-dynamics,which is solved by using the Monte-Carlo method.A case study is carriedout, in which some characteristic values,i.e.average one,standard deviation and coefficient of standard deviation,are used to reveal the WRI state and its variation within the domain.It is known from the result that within the system:(1)the related interactions may take place by themselves,(2) the relative large value of standard deviation shows the probability of the system approximate to equilibrium state,and (3) the acidification of groundwater is mainly produced by the oxidation of organic substances in shale.
Abstract: The study on soil moisture dynamic is instrumental in establishing the quantitative linkage between hydrologic dynamics and ecological patterns and processes.The experiment based on the auto-weighing lysimeters aims to study the soil moisture dynamics and evapotranspiration (ET) of revegetated and bare desert dune area.The results reflect that during the experimental periods between March 31 and October 21, 2002, the soil moisture dynamics is highly related to the individual rainfall events, the areas of Artemisia ordosica Krasch and Caragana korshinskii Kom vegetation have a grossly equal magnitude in overall ET through the growing period, and the daily ET is 1.31 mm/d and 1.22 mm/d, respectively.The soil moisture decreases greatly in the Caragana korshinskii kom vegetation during the non-rainfall time for more than one month, especially within the soil profile of plant root concentration depth of 40-60 cm and 100-140 cm.After a long time of intra storm period, the ET rate of Artemisia ordosica vegetation decreases from the former value of 1.8 mm/d to 0.9 mm/d, the corresponding values of Caragana korshinskii kom vegetation and the bare desert dune area are from 2.2 mm/d to 0.6 mm/d and from 1.1 mm/d to 0.4 mm/d, respectively.To the overall deep drainage from the bare desert area, it accounts for 113.4 mm.Hence, the order of magnitude of annual rainfall fraction (40.5%) turned into groundwater recharge for similar areas varies between 0 and 50%, which has been shown by some previous investigators.Consequently, the results of this study fit the situation in the high middle of this interval.The artificial re-vegetation uses this part of precipitation effectively by eliminating the deep infiltration.
Abstract: In order to show objectively the dynamic change characteristic after ecological water transporting project,and realize the goal to provide the scientific evidence for extensive restoration and reconstruction in the lower reaches of Tarim River,nine monitoring sections and thirty-nine monitoring wells are built along the 321km river way to rmnitor the variation of groundwater level.After nearly three years' monitoring and analyzing in this region,it is found that the groundwater levels have different change characteristic in lengthways and transverse direction respectively.These results indicate that the benefits of ecological water transport will be present gradually.Therefore,the assessment of ecological water transporting project on environment should be done in the future several years.In addition,on the basis of the analysis on groundwater level after water transport,the suggestions on adjusting the way and scale of ecological water transport are presented.
Abstract: As a core problem of regional sustainable development strategy research,evaluation of regional water resources sustaining utilization system is a complex system which consists of indexes of population,resources,environment,economy and society,whose key problem is how to quantify with reasonly the weights of each index of the system.To resolve the problem, the application of an analytic hierarchy process (AHP) is studied in this paper.In order to correct the consistency of judgement matrix in the AHP,a new method,named AGA-CAHP,is proposed to check the consistency of judgement matrix and,at the same time,compute rank weights by using the accelerating genetic algorithm developed by the authors.The results of theoretical analysis and case study show that the AGA-CAHP has visual,pradical,stability and high precision,and that the AGA-CAHP can be applied to other practical evaluation systems.
Abstract: Due to the limitation that the objective weight or subjective weight is considered separately in the multi-objective deci sio n-making,the concept of a tradeoff coefficient is imported,and a fuzzy iteration methodology paying attention to subjective and objective decision-making,which,at the same time,gives a objective weight and the relative membership degree of alternative,is presented in this paper.Since this rmdel takes into account,in the meantime,the objective intent of decision-maker and the natural property of alternative,the ranking of alternative is more feasible and reasonable then former method.Rnally,a case is applied in the appraisal of reserwir flood control to show that the model is scientific and practical.
Abstract: By traditional differential equation oriented sunulation, the sunulation modeling and proceess can he hardly revealed, the program only can be applied to the special water conveyanc, system.In this paper we conduct a study of the new way to carry out simulation modeling for water conveyance system.With the help of the Simulink software, we apply the structural drawing oriented simulation to water conveyance system.Using the structural drawings to construct the simulation model, we can make the simulation visual easily.On the other hand, the simulating can be controlled betimes according to the feedback information of visualization.We at last improve the feasibility of the new simulating method by an engineering instance.
Abstract: The measures of water resources development with technical feasibility can be economically and rationally analyzed by using the marginal cost analysis method.Therefore, the connotations of several measures in regional water resources development,such as saving water,treating waste water and potentializing other water sources are defined,and the characters of marginal cost curve of these measures are analyzed.According to the principle of marginal cost equilibrium and the theory of mutli-objective decision of water resources system,a method of comparative decision of marginal cost and a goal programming model are proposed to choose the optimal combination of various measures for regional water resources development.The computed example shows the feasibility and effectiveness of the proposed procedures.
Abstract: Low flow and flood are extreme hydrology,but researching profundity of low flow is lower than that of flood.This paper summarizes mostly contents and methods about the research of low flow at home and abroad,including three contents: (1) analysis on factors that influence the runoff of low flow,(2) frequency analysis and the methods dealing with zero of low flow,and (3) calculating and forecasting of low flow system.Then this paper puts forward some foreland researching contents in the domain of low flow,discusses about traditional methods of probability statistics and time-sequence analysis,and emphasizes new technique,"3S"(RS,GIS,GPS) technology,in applications of low flow at the present time.This paper provides important referent worthiness for more researching low flow in the future.
Abstract: Chaotic and stochastic behavior have different character in essentiality, the describing methods for the two characters are not scone each other, and identification of chaotic and stochastic behavior of rainfall and streamllow tune series in the watershed is the most unfxutant basHnent for modeling and forecasting it.In the last decade, many hydrologists have ergaged in the study of the diagnosis of chaotic behavior and the chaotic prediction methods of rainfall and streamllow tune series.The reconstruction of the phase space and the diagnosis of chaotic behavior as well as the chaotic prediction methods of rainfall and streamflow time series are reviewed.The two luniting conditions, the problem of data size and data noise are also discussed in chaon theory application to rainfall and streamflow tune series.
Abstract: The latest progress in study of the regional flood frequency analysis is reviewed in the paper.The classic index flood method is discussedfirst,then a number of principles that should be observed in the regional flood frequency analysis are analyaed.The conclusions about some critical questions in the regional flood frequency analysis such as data checking, hydrological region identification,and hormgeneity testing of the hydrological regions are presented finally.