Abstract: The fractional advection-dispersion equation (FADE) is a new theory for simulating solute transport,but it needs to be validated whether the FADE can be directly used to simulate the scale-dependent transport without considering the scale effect of the dispersion.The dispersion coefficient is calculated by fitting the analytical solution of FADE to the laboratory data for long homogeneous and heterogeneous columns,and the relationship between the dispersion coefficient of FADE and the transport scale is then analyzed.It is found that the fractional dispersion coefficient of FADE increases with the transport scale,and the scale effect of the dispersion coefficient in the heterogeneous soil is much more significant comparing to that in the homogeneous soil.The relationship between the dispersion coefficient and the distance can be described using an exponential function for the homogeneous soil and a power law function for the heterogeneous soil,respectively.Except for the nonlinear scale-dependent dispersion coefficients,the linear time-dependent and distance-dependent dispersion coefficients are used,and then three types of the modified FADE with their explicit finite difference approximations are established to simulate the scale dependent transport in both the columns Parameters in the later two dispersion coefficient functions are fitted with the measured transport data at the location of 100 cm for both the columns.Thus we use the finite difference schemes with the obtained scale-dependent dispersion coefficients to simulate and predict the transport in other locations.The results indicate that the simulated concentrations with the proposed three scale-dependant dispersion coefficients are in good agreement with the measured concentrations for the homogeneous soil,while the agreement for the heterogeneous soil is less sat isfactory.
Abstract: The groundwater monitoring network design involves the determination of the sampling locations and sampling frequencies to characterize the contaminant plume in an aquifer over space and time.This paper introduces a spatial sampling reduction method,the Delaunay method based on Delaunay triangularization,to identify and eliminate the redundant sampling wells of an existed long-term contaminant monitoring network.Considering that the Delaunay method is applicable to both the heterogeneous aquifers and inserting additional sampling locations in the insufficient monitoring network,a modified Delaunay method coupled with contaminant transport model is developed to deal with these issues.The results of this study indicate that the modified Delaunay method can be used as an efficient tool for the cost-effectively spatial sampling network design mean while keeping the accuracy of the characterization of the contaminant plume.
Abstract: Water is one of the most sensitive and restrictive factor for the sustainable social and economic development.Especially,in the arid and semi-arid zones,water resources have become one of the pressing critical problem for the economic development and the ecosystem conservancy.Around the proper objective and scale of the ecological environment and the core task of the reasonable utilization of water resources,the paper studies ecological evolution and ecological water demand of Ningxia using the techniques of RS and GIS,and gives some creative suggestions.After the analysis of the ecological significance,the existing ecological conditions and the water resources in the watershed,the theories and studies on the ecological evolution and ecological evolution are put forward with the new ideas of the ecological water demands.
Abstract: A river quality management model is proposed for the optimal waste load allocation in a tidal river basin,taking into account the impacts of stochastic pollutant discharge and dynamic hydrological conditions on water quality during a tidal cycle.The model is known as the maximization of total allowable waste load,subject to meeting water quality standards at checkpoints along the river.The waste load is regarded as a stochastic variable following the log-normal probability distribution based on statistical data,and the constrains on water quality levels are expressed in a probability form.A genetic algorithm is used to solve this stochastic programming model.A case study shows that the optimal waste load allocation can achieve water quality standards in stochastic conditions,and the model's outcomes are clearly different from those of the conventional deterministic linear programming model 1 The computational results imply that a genetic algorithm is effective to solve complicated stochastic programming models.
Abstract: This study presents an approach to the determination of the trophic parameters of chlorophyll-a from field reflectance spectra in Nanhu lake in eutrophic status in Changchun.The reflectance spectra was measured using ASD FieldSpec spectrometer from April to september in 2004.Based on in situ water samplies and the reflectance measurements,the features of the spectral reflectance of the water are discussed.Algorithms are developed to evaluation the spectral data.The single band R753nm,the spectra ratio of R753nm /R681nm,and the reflectance first-derivative of 700 nm,showing a linear relationship,are found to be significantly correlated with the concentration of chlorophyll-a,and the determinative coefficient R2 gained by using the single band is higher than that gained with other two models.There is satisfactory correspondence between hyperspectral models and chlorophyll-a concentration,therefore,it is possible to monitor the water quality of Nanhu lake throngh the hyperspetral remote sensing data.
Abstract: Wujiangdu reservoir is located at the mainstream of Wujiang river,the biggest tributary in the upstream of Yangtse River.The surface water was collected monthly near the dam of Wujiangdu reservoir from Oct 2003 to Sept.2004.The water sample and sediment cores were at the same station in (December) 2003,and April and July 2004 respectively.The concentrations of the dissolved silicon (DSi) in the water column and the porewater were determined,and the (Chl-a) concentrations of chlorophyll-a in the water column were analyzed.Other parameters such as temperature and dissolved oxygen were measured in situ.The result shows that the DSi concentration in the surface water ranged from 0.53 to 3.96 mg/L,with average of 1.74 mg/L; and the DSi concentration in the porewater is about 7 times higher than the overlying water.The DSi concentration in the stratified water bodies increases with their depths,compared with the increase of porewater,firstly,and then decrease with its depth.The good inverse relationship between DSi and Chlorophyll a suggests that the variation of DSi concentration in Wujiangdu reservoir is determined by the biological activities.
Abstract: The Tai Hang Tung Storage Scheme (THTSS) is an essential component of the West Kowloon Drainage Improvement-StageProject that will be implemented to solve the flooding problem in Mongkok-a congested and densely populated district of the Hong Kong Special Administration Region Over the years rapid development and changes in land use have resulted in significant increases in surface stormwater runoff,and the existing drainage system failed to cope with severe rainstorms.Rather than digging up roads and widening/adding existing drains,an economic drainage improvement plan calls for the construction of a 100,000 m3 underground storage tank upstream of the flooding black spots,below an existing football field in the vicinity of the Tai Hang Tung/Tat Chee Road junction.The upstream storage can serve to attenuate peak floods and protect downstream areas from flooding.Due to the complicated flows in the stormwater drainage system (including subcritical and su percritical open channel flows,pressurized flow in closed conduit,side weir overflows,and transitional flows at junctions),a 1D numerical model of the unsteady flow is developed to study water stages and flow characteristics for different side weir ar rangements,based on the observations provided by a 1:22 undistorted Froude scale physical model under the steady inflow.The key findings of the physical and numerical model studies are reported herein.The studies have resulted in an optimal design of the flood storage scheme; the physical model tests and the numerical model results indicate that THTSS can enhance the flood control capacity to cope with a one in 50 year rainstorm.
Abstract: Many experiments,the analytic solutions and the numerical simulations are conducted to investigate density currents.But turbulence is usually neglected or sometimes considered by using the simple turbulence model among them.In this paper,a 3-D mathematic model with the explicit algebraic Reynolds stress/fluxes turbulence model (EARSM) is developed to simulate the anisotropic buoyant turbulent flows.The collocated,unstructured finite volume method is applied to solve the Navier-Stokes equations and the pressure coupling is treated using the SIMPLEC algorithm.The case of 3-D density currents' spreading on the slope with 15 angle is simulated Results show that the spreading velocity of the front computed at the present is consistent with the experiments.Also,the present model successfully reproduces the flow characteristic and the configuration of density currents,and shows its good convergent performance.The model can be extended to simulate density currents' spreading in natural environment with complex geometry and topology.
Abstract: Based on the observed data and the former research,the ergodic hypothesis is introduced to analyze the process of the reformation in the middle-lower Han river after the construction of Danjiangkou reservoir.It is concluded that the phenomena of replacement of spatial and temporal process is typical in the erosion development,the coarsen of riverbeds,the sediment concentration and the change of river regime,etc.The phenomena originate from the same response to the same generation in the self organized process of rivers in the process.Change of flow and sediment conditions,inflow of branches,the different river boundary conditions and the different respond methods caused by the different of river boundary conditions are the cause of complex response in replacement of the spatial and temporal process.The proper numerical method of replacement of spatial and temporal may be useful to the rivers downstream of many reservoirs.
Abstract: The merits and shortcomings of the protection method adapted now in China for the scour at piers are analyzed.The principle of the local scour at piers is described here.By a series of experiments,the effect of tetrahedron frame protection method (TFPM) is studied Furthermore,it proves that the TFPM has some engineering value for protecting local scour at piers.
Abstract: With an increasing trend of the urbanization in most domestic cities,urban water environment will be influenced greatly.This paper probes into the spatial-temporal trends of water quality of the five rivers with the watershed area above 100 km2 in Shenzhen city,and explains the correlation relationship between the land use type and the water quality indicator by using the statistical analysis and the spatial analysis.The results show that the water quality of these five rivers from 1996 to 2004 is deteriorated and the land use type of these watersheds has close relationship with different water quality indicators,specially,the usage of arable land,orchard land and construction land will obviously result in the organic pollution of the instream water quality.This study indicates the water resources protection from the perspective of the land structure optimization and land use planning.
Abstract: The ratio of the skewness coefficient to the variation coefficient is computed with uniform method for the rainfall data from 5 100-13 600 stations with durations of 10-min-3-day and 210 stations with durations of 1-day-90-day and 1-year.The ratio of skewness to variation (Rsv) characteristics of the Pearson type Ⅲ frequency distribution are approached; the regional distribution of Rsv and the Rsv-duration relation are analyzed,and the same affected factors on Rsv are studied.On the condition of the data at present,the single Rsv value of 3.5 is not suitable for each region and each duration in rainstorm frequency analyses.
Abstract: Based on the theory of linear dual-source evapotranspiration (ET) model,this paper develops a remote sensing model for estimating the land surface ET.The remote sensing model has two characteristics: to (1) simplify the VITT method and improve the accuracy of determining soil water status in a semiarid irrigation area,and (2) introduc the dual-source model in calculating land surface ET and improve the calculation accuracy of the mixed pixels.The remote sensing model is applied for calculating the land surface ET about a 1 000 km2 in North China Plain by using 13 Landsat TM and ETM+images during the period 2000-2002.It is illustrated that the remote sensing model based on dual-source linear concept can get good estimates when applied in semiarid irrigated area.
Abstract: Lakes are valuable water systems,used for production of drinking water,fisheries and recreation,and can be an important indirect indicator of climatic change MODIS data is suitable for regional to global operational observation as moderate resolution imaging spectroradiometer,costing little and having high temporal coverage.But the mixed pixel is a common problem.The objective of the study is to develop high accuracy sub pixel mapping algorithm.Firstly,we use the multi endmenber linear spertral unmixing technique to estimate the lake fraction in the each mixed pixel,and develop an algorithm,to locate spatially the water body within mixed pixels corresponding to the water proportion in the pixed.The algorithm produces a finer sub-pixel lake map relative to the source MODIS image.The results indicate that it is an efficient and promising sub pixel map ping algorithm.
Abstract: This paper researches the integrated method of urban debris flow risk assessment.The method involves the debris flow hazard zonation,the urban vulnerability evaluation and the risk assessment.The debris flow hazard zonation on the alluvial fan of the study area is caused by overlaying the distributed flow depth and velocity maps,which are produced through the numerical simulation.The detailed land cover information is derived by using the Quickbird high spatial resolution satellite imagery,and then we evaluate the vulnerability value through the different land-use features.Based on a GIS statistical and analytical tool the urban debris flow risk assessment for the study area is completed.This risk zonation map can be used for the debris flow mitigation by identifying hazard prone areas allowing for the avoidance through zoning or other land use polices,and provide risk information for the residents who live in the debris flow prone areas in order to plan the evacuation and prevention.
Abstract: The paper chooses 365 cities to study the current situation of water demand,water supply and water shortage.The result are summarised in six sub areas.The study shows water demand of the all study cities is 66 34 billion cubic meters,the water supply is 59.99 billion cubic meters,and the water shortage is 6.35 billion cubic meters.If ground water is not being over used,the water shortage is still about 9.57 billion cubic meters.If we extend those datum further to all Chinese cities,the shortage of water supply is 10.5 billion cubic meters.According to the water shortage standard established in the paper,275 cities are lake water,of which 93 severe water shortage ones.The paper analyzes the character,distribution and influence of water shortage.
Abstract: The paper summarizes the advances of basin water resources real-time allocation,and expatiates the necessity and the development of the water resources management in Heihe River basin.Due to the impact of human activities on hydrological cycle,the one-dimensional static hydrological model can not adapt to basin hydrological cycle.Therefore,the two-dimensional dynamic hydrological model,which gives full consideration to human activities,is developed.The paper gives the principles of the basin water resources real-time allocation,i.e.to operate by the long term water resoures allocation,to consider long term water allocation with short term goals,to make real-time decision,and to modify the results dynamically.An example application to Heihe River basin illustrates the process of the water resources real-time allocation.The study makes a probe into basin water resource real-time allocation and may provide an example for arid and semi-arid areas in North China.
Abstract: Based on adding the cation high molecular weight polymer into the turbid suspended liquor containing 85 kg/m3 of sediments,this paper discusses the changing hydrodynamic turbulent conditions in the process of flocculation,such as shearing rate r (or velocity gradient G) and shearing time t,and the use of the settlement and the image analysis technology,the factor "fractal dimension D" which can characterize the fractal properties in quantity and the evolution regularities of the fractal structures of the bridging-flocculated aggregates.The results show that there are two critical values about hydrodynamic turbulent strength Gt (G1t1= 2350±100 at rapid flocculation stage and G2t2= 12400±100 at slow flocculation stage) when fractal structures reach the optimum state.It is found in experiment that the optimum Gt value is nearly the same when the compactness of the fractal structures of the bridging flocculated aggregates reaches the highest point of the different raw silt content.When raw silt content is low,r or G value should be reduced and t value increased However,the value of the fractal dimen sion D decreases Furthermore,when the fractal structures of flocs formed by the addition inorganic coagulant and the bridging-flocculation aggregates formed by the additional high molecular flocculant reach the optimum state with the same raw silt content,the former needs the higher Gt value,corresponding to the lower G value and the longer t value and the average mass fractal dimension D3 value of floc is higher,but the fractal structure of floc appears frangible.
Abstract: According to the observed data of water and sediment,deposition and erosion,flood information,etc since 1950,the interrelationship among water volume of the sediment transport,the oncoming water and sediment,the flood discharges,the index of sediment and flow matching,the water and sediment diversion,the permissible deposition in the river course,etc,are studied in this paper.Based on the sediment transporting law and the index a formula which can be used to compute the water volume of the sediment transport in flood period and flood season at the controlling stations of the Lower Yellow River is set up.The formula expresses quantitatively the impact of water and sediment changing,and permissible deposition to the water volume of the sediment transport This research is very important for the plan and utilization of water resource and is very significant for keeping the Yellow River health.
Abstract: A new two-step control method based on the principle of optimality is proposed for the gravity-flow in open channel system.The first step is to control all the levels (or volumes) in the channel to reach the goal levels (or volumes).The second step is to adjust the channel flow of all sections to realize the stabilized level.The optimization flow control model is built,which make the levels reach the goal levels in the shortest time.The corresponding constraints for this model,the downstream water demands,the maximum water levels,the allowable drawdown rate of water level,the allowable discharge capacity of the channel,the minimum frequent of switching on and off the pump,and so on,are constituted.The solution to the problem is proposed by using linear the program method or decomposing a large and complex system into two or three small and simple systems.The example application of this method shows that the time during which the water levels reach the target levels and keep them stable can be reduced from a few days to a few hours.
Abstract: With the background of the global climate change,the study of the global hydrological cycle is paid more attention to by governments and scientists.The research programs of the global hydrological cycle are introduced in this paper.And the achievements of these programs are discussed.There are three main achievements: the basic data,the hydrological cycle simulation models,and the land-atmosphere coupling theory and method.In the end,the future progress of the global hydrological cycle is prospected.
Abstract: The recent research techniques of the simulation method for water resources system are improved rapidly due to the enhanced recognition of the system and the development of the related information technology.The development of the integrated simulation system is a trend for the management and planning of water resources.In this paper the current situation and new progress of the simulation techniques for water resources system are introduced briefly.The informatics and computational techniques play very important roles in facilitation of the water-related models.Combined with characteristics of water resources system,the standard conceptualization of a river makes it necessary to construct a general simulation model for the water resources system.Based on the comparison of the different methods and models of simulation,the common concerns of general water system model are summarized and the prospect of future research is put forward.
Abstract: Some appropriate assessing methods for instream ecological flow or environmental flow requirements are established after many years research.Each method differs in its data requirements,procedures for selecting flow requirements,and ecological assumptions.An applicable method is chosen based on the current information and the goals.Four categories of the common methods,namely,hydrological index methods,the hydraulic methods,the holistic methods,and habitat methods,available for assessing instream environmental flow,are reviewed according to their applicability.