Abstract: The unsaturated hydraulic conductivity is a key parameter of porous media applied to groundwater pollution prediction and assessment. The fractal approach is employed in derivation of a power law equation consistent with the empirical Camp bell's Law to predict unsaturated conductivity of porous media. The power exponent is a function of the pore-wlume fractal dimension and random walk dimension,which respectively characterize the static and dynamic properties of the media,but the contribution of the static property to water rmvement is dominant. The analytical comparison of the reported experimental data of fractal dimensions with the corresponding power exponents indicates that the derived power law equation is valid for predicting the unsaturated conductivity of porous media.
Abstract: In this paper,a new approach of automatic generation of 3-D tetrahedral element mesh based 2-D triangle mesh is presented.The key principle of the algorithm is that the original prismatic polyhedron is formed by planer triangular mesh crossed with vertical section,and then divided into several tetrahedral elements according to the information parameters zonation in aquifers.The moving free groundwater table is also taken into account during the course of mesh generation in each calculation step.The programming procedure of tetrahedral meshing is also stated in detail in the paper.It is concluded that the algorithm is a valid,effective and convenient approach to the description of spatial stratum formation in complex aquifer such as lens or sharp lithofacies and etc,so as to provide 3-D mesh data for numerical calculation1
Abstract: With experiment data under different water and nitrogen treatments,this paper studies the changing patterns of nitrogen nxwement and transformation,losses of amrmnia wlatilization and nitrogen leaching,nitrogen distribution within rice plant,nitrogen balance in paddy fields. The results shows that amrmnia wlatilization is high under water saving irrigation (WSI) compared with continuous flooding (CF) because the soil solution concentration is higher. Although concentration of NH4 and NO3- in the percolation water is higher under WSI,total nitrogen leaching loss is lower because the total percolation loss is much lower than those of CF. Under WSI conditions,more nitrogen supply splits can decrease nitrogen losses and increase nitrogen efficiency. WSI practice is propitious to nitrogen recovery and its transferred to grain. The WSI regime produces optimal water and fertilizer management for paddy rice when 250-400 kg/hm2 of urea is applied through three splits.
Abstract: The k-ε turbulence model is used to establish a mathematical model for round negative buoyant vertical jets in flow ing environment. The model and the method are verified with the comparison between the calculated results and experimental data Streamlines and density contours in different section are given. It is also found that there is a low density region behind the inlet and the jets branch off after impinging the boundary and the density near the side is higher than which in the middle of the channel.
Abstract: Starting with the influence on the movement rules of small cavities,the mechanisms of emerging a single spherical bubble are study from the aspect of the turbulent coherent structure near the wall. A dynamic equation is established for the bubble and single spherical sand under the non-turbulent coherent structure near the wall,and then under the turbulent coherent structure near the wall. Through comparison,it can be seen that the turbulent coherent structure near the wall influences directly the cavitation of the bubble.
Abstract: The present work is an experimental investigation of confined water jet in jet pump.The confined jet in a converging conical inlet and in a constant-diameter pipe of the jet pump is measured by particle imagine velocimetry(PIV).The throat-to-nozzle area ratio of jet pump is 4.75.The Reynolds number based on nozzle outlet velocity and nozzle diameter D of jet pump is 3.68×105.The effect of flow rates on flow field of jet pump is studied by changing the flow rates from 0.20 to 0.80.Velocity vectors,centerline velocity decays and axial velocity contours on the symmetry plate of the jet pump are obtained for four flow rates of 0.20,0.35,0.60,0.80 within a length of X/D=13.8.The results show that the confined jet in jet pump depends strongly on the flow rates when the area ratio is fixed.The smaller the flow ratio is,the quicker the centerline velocity decays are,and the shorter the jet's length of the high-velocity zone is.All results obtained in this paper provide a reliable basis for theoretical study and optimal design of jet pumps.
Abstract: This paper presents a 3-D current numerical model for the Yangtze River estuary with baroclinic-diagnosis mode in vertical σcoordinate system.A vertical eddy-viscosity coefficient is obtained from the advanced k-kl turbulence closure model, and the density baroclinic effects are embodied by the 2-D invariable-uneven salinity field.It shows the results from baroclinic-diagnosis mode well consistent with reality.The transition feature from back and forth current to rotary current is re-acted successfully.In addition,several tidal junction points appeare near branch points when tidal wave propagate from four river forks, the position of which change with runoff,tide and topography.
Abstract: Nowadays,Bositeng Lake is the biggest inland fresh water lake in China. However,the mineralization degree of the lake had preponderated over 1.0 g/L since 1970's,1.8 g/L in 1980's,and now about 1.3 g/L. Based on the observation data,the variable trend of mineralization degree of the lake is discussed in this paper. The main and key factors that influence the mineralization degree of the lake are analyzed and decided by the water quantity-quality-ecology system model. Finally, countermeasures about mineralization control are put foreword.
Abstract: This paper firstly reviewed the current situat ions of applications of remote sensing techniques to inland water quality monitoring and its development process,and explored the principles and methods of applying different kinds of remotely sensed images to inland water quality monitoring.As examples,it also presented the applications of remote sensing techniques to monitoring several main variables of inland water quality,including chlorophyl-a,suspended material and dissolved yellow substances.Finally,some key problems existing in this field were discussed and some suggestions were proposed.
Abstract: A large amount of sewage above the standards drain into the Cao'e estuary,making highly pollution in the estuary.To seek the effects of effluent sewage on water quality in the estuary,a 2-D depth-average mathematical model is used to calculate the distribution of water quality on the two cases of effluent sewage up to and above the standards.The results show that the water will be contaminated and the water quality above the fifth class occured if effluent sewage is above the standards, and satisfy to the territorial request of the third class water quality function if effluent sewage is up to the standards.Therefore it is very important to controll Shaoxing effluent sewerage for protecting the water quality in Cao'e estuary.
Abstract: In order to predict the effect of the river improvement on the channel evolvement at the wandering-braided reach of the lower Yellow River,based on the theory of fluvial dynamics,the complex ersponse of the channel changes to the river improvement at the wandering-braided reach of the lower Yellow River is studied by the physical model experiment.The results show that the regulation of channel section is related to the restrainted degree of man-made boundary,flow variation and sediment concentration.When the plan layout of regulation project system is reasonable and the quantity is enough,the channel section will be developed to a narrow and deep channel by river improvement,which will make the wandering-braided reach into a restricted tortuous channel.Meanwhile,the flood carrying capacity and sediment transport competency are increased.The regulation of fall at different reach doedn't develop parallelly after the river improvement.
Abstract: The Jiujiang reach evolution of the Yangtze River recent forty years is rationally simulated by the digital evevation model(DEM)and the GIS technology The research result are as follow:Jiujiang river channel is general charactered by erosion from 1963 to 2002,and the total erosion volume is 14.977×106m3;From 1963 to 1972,the general result is sedimentation,the total disposition quantity is 6.505×106m3,the average rate of disposition is 0.65×106m3/a;From 1972 to 2002,the general result is erosion,the total erosion volume is 20.720×106m3,and the average rate of erosion is 1.036×106m3/a;And the main area of disposition locats in the south bank area including the middle channel and the middle area of the lower channel and the main area of erosion locats the channel north bank area and the south bank area of the lower channel The channel change is due to the result of the channel borderline conditions,the water flow,the suspended sediment load and the human activities The cont inual erosion of the south bank area along the middle and lower channel bring the more pressure to flood prevention.
Abstract: According to the requirement of mass and energy continuity of water and sediment and the analysis the water sediment model of single reach,a numerical model for calculation og the normal river system is established in this article,and tested by the observed data of the the Jingjiang River and the Dongt ing Lake in 1997. The result shows that the computed data and observed fits well,which indicates that it is suitable to sum the complex boundary of the Jingjiang-Dongt ing Lake and is applicable.
Abstract: The mediums and the places of the water evolvement have formed the ecological storeroom of water(ESW).Based on the analysis of the primary theory of ESW,the evolution and variation of the ESW in the East Liaohe river basin(ELRB) are analyzed with the key desktop of GIS.The ESW provided by river system is 204.08mm in the ELRB and 39.83% of the multi-year average precipitation.The one-time ESW provided by slop system in the ELRB is 97.35mm and 19.48% of the ecological water requirement by slop system and 47.70% of the ESW provided by the river system.The ESWs provided by river system and slop system have features of spatial variation.The total ESW in the ELRB has high value network centered with the channel and the high value island centered with lakes and reservoirs.
Abstract: Based on the measured data,annual water consumptions are estimated for different land useing types by applying evaporation coefficient method,and the ecological water use is analyzed in Weiganhe river plain oasis The results show that: (1)The water consumption for farm field and forest land,grassy marsh land and low lying land,waste land with sparse vege tations,waste land without vegetat ions are 947-1 026 mm,791-845 mm,308-415 mm,137-172 mm respectively; (2)The evaporation coefficient are 0.83-0.86,0.68-0.72,0.27-0.35,0.12-0.15 respectively;And(3)the amount of ecological water use is 11.8 to 13.7×108m3,which accounts for 45 to 49% of sum of irrigated water,groundwater recharge and precipitat ion The results can provide the important scient ific basis for rational water resources allocation in the plain oasis is northwestern China.
Abstract: In the growth stage of winter wheat(from April to May in 2002),the canopy temperature,air temperature,volumetric soil water content were measured for the non-irrigation winter wheat.Beside,the canopy temperature,canopy-air temperature difference and volumetric soil water content are analyzed in this paper.The results indicate that the canopy temperature at 14:00 can reflect soil water content of the soil layen in 20 cm deep,but relativity in other soil levels has bigger fluctuation;the change of the volumetric soil water content in the depth 40 cm can be preferably reflected by the changes of canopy-air temperature difference at 14:00,the relational coefficients are 0.988 66(20 cm),0.993 89(40 cm),respectively which indicate that it can used as the base for monitoring regional soil water content through the retrieval regional canopy temperature; And during jointing stage and grain filling stage,the higher precision by canopy-air temperature difference simulating volumetric soil water content can be used as an empirical model for monitoring regional volumetric soil water content.
Abstract: On the basis of the development of laboratory equipment from which soil moisture can be measured automatically, the temporal variations of soil water content distribution during evaporation and post evaporation were analyzed,of which,the film hole ratios and irrigation quotas were diferent. Then after,through calculation and analysis of the cumulative evaporation, the three-factors empirical function of cumulative evaporation determined by evaporation time,open hole ratio and irrigation quota was developed. The function was based on the theoretical relation of Gardner's equation for bare soil evaporation,it can be considered as an extension of the Gardner's equation Moreover,the influences of open hole ratio and irrigation quotas on relative cumulative evaporation and cumulative evaporation per unit film hole area were analyzed,and the related estimation functions are also provided.
Abstract: The evapotranspiration estimation model is presented based on energy balance through remote sensing.The parameters of the model could be modeled using empirical and semi-empirical formulas;Based on net radiation convert coeffcient and Bowen ratio,combining theory of Sequin and Itier derive the daily evapotranspitation experience model of calculation;in respect that the temperature can influence the instantaneous evapotranspiration,which improve the estimation accuracy of the daily average evapotranspiration.As in different area,adjusting net radiation convert coefficient only can solve the daily evapo-transpiration calculation problem from the instantaneous evapotranspiration value.Through a case study in Heilongjiang Province,it proves that this model has strong practicality and can offers scientific basis for the operation of drought monitoring system.
Abstract: In the relatively dependent and most integral unit of catchment area in hilly red soil landscape,we study the yearly dynamics of surface water resources including rainfall,evapotranspiration and water storage.The results show that the water volume ratio among soil evapotranspiration,dike and pool storage,drainage from catchment area is about 7:2:1.The water distribution in sloping field of soil and water conservation type among vegetation interception,soil,surface runoff is 3:5:2. And the water storage volume of 1m of 1 hm2 unit in sloping field of soil and water conservation type is 864.0-1 067.0 m3 more than non-conservation type in rainy seasons,and 647.0-855.0 m3 more in less rain seasons.The more results show that the water storage volume for agricultural irrigation use is about 12% of yearly rainfall.The dike and pool for storage use should be about 11% of the catchment area.The expanding dyke and pool area to resist seasonal drought is not effective if about 10% of the land area is in hilly red soil regions.The solution is to develop the vast potential of hydraulic engineering and "soil reservoir" effect.
Abstract: As a key parameter of multi-purpose reservoir operation,flood limit water level plays a critical role in achieving the balance between flood control and economic benefit such as hydro-power generation and navigation improvement etc.The currently adopted flood limit water level pays too much attention to the floods of low probability,thus reducing the economic benefit of the reservoir during the flood period.It is theoretically and applicably essential to adopt a dynamic flood limit water level in the operation.According to the general operation rules of Three Gorges Reservoir(TGR),a real-time model under dynamic flood limit water level is developed and used to simulate the TGR operation by using the daily river flow series of the Yichang gauging station about 40 km downstream to the dam site of the TGR during the period of 1882-2001.The multi-objective criteria and a comprehensive evaluation model are proposed and developed to measure and assess the TGR operation risks.The optimum scheme is obtained by comparing nine alternatives of dynamic flood limit water level schemes.
Abstract: Based on the multi-time scale and the nonlinear character of the daily discharge time series,the wavelet network model a hybrid model between wavelet and artificial neural network(ANN),is presented.The suggested model has super advantage with its absorbing some merits of wavelet and artificial neural network.The predicted accuracy has been risen and the length of predicted time has been lengthened.The prediction of daily discharge at Cuntan station of the Yangtze River in China is researched.The results show that the presented model is satisfactory.
Abstract: Based on the characters of water dispatching project in the main steam of Yellow River,this paper presents the principle and purpose of the sustainable water dispatching,and establishes a combined decomposition-coordination models for water dispatching of the main steam of Yellow River,which consists of the operation model of cascade reservoirs in the up reaches,the combined operation model of Sanmenxia reservoir and Xiaolangdi Reservoir in the middle reaches,the spatial al-location model,and the optimization model of scenario evaluation.The model presented is advantageous in efficiency and flexibility of development,easy for application and clear data flow.The solving strategy of the combined models is also presented1 The preliminary applications show that the model is successful and efficient.
Abstract: This paper dissects formation of water resources in mountain areas,scatter and disappear of water resources in plain areas and duality composition in artificial oases etc main features of water cycle in the inland river basins of Hexi Region through analysis of water cycle in the inland region of Northwest China.It is revealed that the water resources of the basin is transferred and related each other in water cycle.Moreover the water consumption in mountain areas,the transformation between surface water and groundwater and consumption increase caused by the artificial oases construction in the Hexi Corridor, and the water shortage of down streams in the inland river basins are quantitatively analyzed.Discussions of delivering entire concept of water cycle in the river basin,evaluating local water cycles between mountain and plain areas,and achieving a virtuous cycle in comprehensive rehabilitation of inland river basins of the West-China development are put forwards finally.
Abstract: On the basis of a revised model of wanderings mathematician,this paper presents a 2-D dynamic programming model for the optimal alignment of channel with known segment function.The model takes the longitudinal slope of the channel and qualitative alignment scheme of each segment as system variables.The minimum works investment is taken as objective function,and the following factors such as the water levels at the head and end of channel,segment transfer of each alignment are regarded as constrains.There are a better results in the optimal alignment with this method than with the traditional one in the application cases.
Abstract: The common methods characterizing chaotic system are briefly introduced in this paper.The most domestic and overseas advance in this filed are summarized,it is concluded that the main applications of chaos theory in hydroscience focused on hydrologic time series analysis and nonlinear prediction model.The most problems revealed in the past studies,such as delay time,data size,noise,are analyzed and discussed in this paper,so the hypothesis of chaotic character of hydroscience problems is reasonable.But as for any finite and noisy time series,it is almost impossible to determine strictly whether the phase-space is a determinate or stochastic system because whether pure stochastic or chaos is an ideal state of mathematics. Any observation achieved through single method may not be used as evidence of chaos in hydroscience problems,can only be regarded as chaotic character.Various ways should be employed to characterize chaos of hydroscience and define whichone, chaos or stochastic is dominating.Finally,we suggest that the fractal chaos dynamical system and the mean of combining chaos with neural net provide several new methods in the future studying.
Abstract: Based on a large number of papers published in more than 30 kinds of journal which deal with different aspects of water sciences,simultaneously,the important national projects and project research reports of the National Natural Science Foundation of China in the recent four years,such as "Study on ecological environmental change in the West China",one of national key scientific and technological projects during the past five years also are referred tol A review of advances on hydrological cycle and surface water has made.