This paper deals with the propagation of the interface between the open channel flow with free surface and the pressurized pipe flow, which is related to the flood and storm water intrusion into the underground space such as a sewer network, a subway system and a underground market. The fundamental phenomena are reproduced numerically by using the simulation model developed in the paper. The basic equations are composed of the continuity and momentum equations for both water and air flows under the assumption of incompressible flow. Numerical procedures with the treatment of the propagation of interface are shown in detail and applied for the typical flows which may occur in the underground space. It will be pointed out from the comparison between the calculated and experimental results that it is necessary to take account of the effect of the air pressure in the model.

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The matrix analysis of flood flows in open channel networks is introduced. Two methods, i. e., the characteristic method and the 4-point implicit method, are used to discretize the primary equations. Computed values by characteristic method are compared with ones of 4-point implicit method and together with observed values. Computed values by two methods are nearly agreed with observed values. It is confirmed that the solutions by characteristic method have a little instability under the condition of steep water profiles.

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A Galerkin type finite element method is presented to simulate the inundation in low-lying area. The moving boundary technique to express the flood front and the iteration to obtain the stable numerical solution are combined with the method.
The inundation in the low-lying area in Hamada city caused by the heavy rainfall of July 15, 1988, has been calculated using the presented simulation method. The peak values of flooded water level obtained from the calculated results agree well with the highest flood traces observed in the inundated area.

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In this paper, firstly, a calculation method for non-uniform open-channel flow accompanied by the transition between superand sub-critical condition is developed on the basis of the MacCormack explicite time-splitting scheme and the applicability of the method is clarified based on the experimental results obtained by the authords using a flume with wide variation in width and slope. Secondly, concerning with the standard steady open-channel flow routings, a model for the estimation of the mean energy slope is Drowsed with the numerical examples.

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When square post put an interval on the side wall of open channel, water surface profile is variable by acceleration and deceleration of velocity at continued sudden contraction and sudden enlargement. when waterway is tunnel, flow patern is changed from open channel to pipe. lt have an influence to construction's safety by conveyance and pressure.
In this paper, we watch a separation region formed behind a square post, meet the equation of continuity at outside of a separation region, water surface profile of non-uniform flow was able to calculate easily by step method.

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Calculations of sub-and super-critical flows with unsteady hydraulic jump are important to investigate the planning or design of a river system. When we use the governing equation with conservative type and apply the defference method, the numerical oscillations have happened in the case of unsteady flow with discontinuities. Accordingly, in this paper, we will introduce the TVD-MacCormack scheme and analyze the surface water profile with the hydraulic jump. Finally, taking off techniques of the numerical oscillations are considered by using computed results for practical examples.

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A numerical study on the 2D and 3D flows over wavy surface with arbitrary shaped boundary has been performed by applying a higher-order upwind scheme and the orthogonal mesh generating technique. In the 2-D cases, we first simulated flows over the sinusoidal solid surface. Numerical results agree reasonably well with the analytical solutions derived by the perturbation method. In the second the flows over dune-shaped solid surface were calculated and the velocity and shear-stress distributions as well as vorticity component ω_z were well predicted. Finally, a flow over the doublesinusoidal surface was simulated via the same scheme and the 3D motions of the fluid on the wavy surface were clarified.

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When supercritical flow rush into a bifurcated channel with different discharge ratio from its width ratio, a hydraulic jump is forced to occur under some conditions. This paper investigate these conditions. First, a valid condition for Bernoulli equation applied to before and after points of a bifurcation was derived and compared with experimental data with jumping states. The outer region of the condition was roughly corresponding to the generation condition of hydraulic jumps. Second, a condition for an entrance of bifurcated channel to provide for jump was obtained from the gradually varied flow equation with lateral inflow. The result shows that the condition satisfy the experimental data.

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The type of hydraulic jump changes according to the Froude number F. When F is less than about 1.2, the water surface is smooth. On the otherhand, for a larger F, a series of small rollers develops on the surface of the jump. However, when the influence of side walls is strong enough to affect the flow at the central part of the channel, the jump is smooth and the height of the jump increases appreciably, even if F is fairly larger than 1. 2. In this paper, we showed that this phenomenon is caused by an interaction between the jump and the turbulent boundary layer.

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In this paper, the experiments were performed to investigate behavior of large scale vortices, the three-dimensional characteristics of the turbulent structure and sand waves in the confluent flow with a training dike, which was produced from the merging of two parallel streams. The results show that the secondary currents with a vortex diameter of about a flow depth exist in the confluence and they develop due to the interaction of corner secondary currents during the merging process. In addition, the three-dimensional characteristics of main flow velocity, Reynolds stresses and turbulent energy are discussed by comparing the confluence flow with the two dimensional turbulent wake behind the thin flat plate.

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This study is concerned with flow chracteristics in a gradually expanding smooth rectangular open channel. The spatially evolution of mean velocity-, Reynolds stress-, and turbulent intensity-profiles in the longitudinal direction were investigated experimentally. Cole's wake parameter is expressed as a function of the pressure gradient, assuming the entire mean velocity profiles to be described by Cole's law. It is found that the distributions of Reynolds stress and turbulent intensities under the adverse pressure gradient differ substantially from these in the favorable pressure gradient.

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The purpose of this study is to investigate the moving characteristics of pesticides scattered in patting-greens caused by heavy rain.
The experimental research was carried out with sand-layer column models. The hydraulic characteristics of unsaturated infiltration were discussed with the experimental results of tensiometers and thermometers. The pesticides concentrations of pore-water and soil-samples were determined by method of gaschromatography (FTD).
Most of the scattered pesticides were adsorbed into soil particles of the shallow layer and therefore the squeezed amounts into groundwater were very little.

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In the present paper, the simulation results of infiltration of trichloroethylene from the natural river bed to groundwater region is shown. The method of characteristics (MOC) and iterated alternating direction implicit method (IADI) was applied to the computation of two-dimensional convection-dispersion equation and groundwater flow equation. It was found that the infiltration from the river bed when the groundwater level was high in the steady state becomes large while small when the level was low. In the transient period of the groundwater table from high to low or from low to high levels, spread of trichloroethylene showed an opposite tendency due to the unsteady velocity field which contributes to the convection of mass transport.

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Large-scale experiment by using lysimeter was conducted to clarify the infiltration of soil water through three-layered formation structure, composed of top loam, fly ash and bottom loam, the calcium leaching from the fly ash, and the leached calcium migration through the bottom loam layer. The results showed that the infiltration through each layer was expressed in van-Genuchten's models, and that the permeability of fly ash was sensitively dependent on water content. Henry type model was applicable to the calcium leaching. The calcium migration through bottom loam layer was described by the combined model which consisted of a reversible Henry model and an irreversible first-order reaction model.

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Effect of the fertilizer on chemical properties of ground water was investigated from March to November in a farm land of West of Fukuoka City. The variation of dissolved oxygen (DO) and nitrate (NO3-N) concentrations in ground waters with time was greatly different by the surface conditions of the land: paddy field or vegetable field. In the case of the former, the DO and NO3-N concentrations decreased gradually from May and showed a minimum at the end of August. While, in the case of the latter, the concentrations were highly constant. Despite that the large amount of phosphate was manured, its concentration in ground waters was low.

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This paper aims to evaluate the applicability of a single phase model for heat diffusion phenomena caused by saturated flow through porous media. These were based on laboratory experiments using vertical bead columns. Since permeability of bead column is increased by seepage of hot-water into cold porous media, a new method for the seepage experiment is adopted to fix Darcy velocity. The coefficient of heat diffusion, κ, which is a main parameter of the model was identified from the experimental data. The behavior of κ values under various conditions were investigated and was used as a means of evaluating the single phase model. In this research, it was shown that κ values are linear function of the heat transfer velocity. The relationship between the heat dispersivity β which characterizes κ values, and the spatial scale of flow is also discussed.

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A stochastic modeling technique has been developed to investigate mass transport in a network of discrete fractures. In order to characterize rock mass geometry for modeling, fracture lengths and spacings were measured on the planar rock face at the site. Fracture lengths and spacing values follow negative exponential distributions. A network is generated using probability density function. The mass transport was calculated using the Monte Carlo simulation procedure. Results shows that mass dispersion have complex patterns. These patterns arise from the limited number of fractures for mass to migrate the through the fracture network.

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This paper presents a method for the estimetion of transverse dispersivity in a homogeneous isotropic coastal aquifer where salt water intrusion takes place and the mixing zone of fresh-salt water is observed. An approximate solution of the concentration profile on the axis perpendicular to the fresh-salt water interface is derived from a similarity approach and compared with the concentration profile measured in a filed experiment. A two-dimensional numerical simulation on salt water intrusion and dispersion is performed using the dispersivities estimeted by the proposed method. Numerically predicted concentration profiles agree well with the experimental data.

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The paper gives a preliminary analysis of intensively sampled soil and wheat plant tissue in the field in order to determine spatial properties of some selected heavy metals in a sludge-applied agricultural soil in northern Tunisia. A preliminary geostatistical analysis shows that both soil and plant metal contents have a spatial structure with a range of less than about 10 m. The sludge application has affected mainly Cu contents of both soil and plant tissue.

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Constant head borehole test is analyzed using a numerical model of the Richards equation. Steady state analysis is used to develop an efficient model scaled with respect to soil conductivity, thus allowing it to be used for the estimation of soil conductivities from field test results. Analytical formulae based on free-surface assumptions and those taking soil capillary effects into account are assessed by comparing with the numerical model results. The steady state analysis method is extended to the estimation of conductivities in uniform anisotropic soils. Field tests and results are discussed.

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An efficient and accurate finite-difference scheme is presented for solving the one-dimensional Richards' equation. The numerical model is based on the ‘mixed’ form of Richards' equation which ensures the mass conservation. The Newton-Raphson scheme is incorporated in order to effectively handle the nonlinearity of the equation. An ‘updating’ coefficient is introduced to further enhance the convergence rate. The effect of the updating coefficient on the required number of iterations per time step was examined as well.

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Water path through unsaturated media was examined for its fractal dimension by experiments with glass-beads and by computer simulations using ‘water path invasion model’ which involves the effects of capillary force and gravity.
Experimental results showed that the water path developed fractal pattern and its fractal dimension decreased as particle size increased. Computer simulations showed that the model can produce the similar nature of fractal water path to the experimental results, if it is supposed that smaller pores can play no role for water path development.

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This paper presents an experimental investigation on the movement of water vapor in a sand column, which is comprised of dry, capillary and saturated zones, and the relationship between the vapor pressure profile and evaporation velocity. The vapor pressure is obtained from the simultaneo us measurements of temperature and relative humidity. It became clear that the evaporation actively occurred near the capillary fringe and most of the evaporated water vapor moved toward the atmosphere and the remaining water vapor moved downward and then condensed. The experimental results for the vapor pressure profiles well agreed with the theoretical results based on the one way diffusion theory. A comparison between the theoretical and experimental results demonstrated the importance of the effect of the vapor pressure gradient across the dry zone on the evaporation velocity.

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A physically based mass and heat transfer model is presented and the theoretical results were compared with the experimental data measured under field conditions. The validity of a set of mass and heat balance equations as well as numerical schemes was discussed through sensibility analyses. In order to predict the evaporation from a bare soil, the model and simulation technique were applied to some practical data collected from a test site in southern France.

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Daily observed field soil moisture is analyzed by use of a finite difference model of Richard's equation including water uptake by plant roots. The hydraulic parameters, which specify the hydraulic properties of unsaturated soil, are optimally estimated through sensitivity analysis. The numerical results show that the effect of the root water uptake on the soil moisture movement is significant in the drying process.

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The permeability may be one of useful indices when determining the excavation-loosened zone of fractured rock mass. The permeability of dry rock mass is measured by a vacuum bohehole logging test which is similar to the standard gas well buildup test used in the petroleum industry. The permeability is calculated from the pressure recovery in the borehole. Then, it is important to know the change in the pressure recovery process due to the size and/or position of the loosened zone.
In this study, numerical analyses were performed to find out the relationship between the pressure recovery process and the loosened zone. The results indicate that the vacuum test provides the useful information on the degree of looseness and the size of loosened zone.

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The permeability in fractured rock mass is expected larger in the excavation-damaged zone than in the non-damaged zone. Hence, it is possible to find out the damaged zone based on the permeability measured by the pressure recovery test in the borehole. In this case, it is important to konw how the randomness of openings affects the results of pressure recovery test.
Numerical 2D-model of fractured rocks were used herein to study the variation in the pressure recovery process due to the randomness of openings. The results show that if the loosened zone extends beyond the test section the pressure recovery becomes definitely fast.

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A method of estimating both three-dimensional wind field and conversion rate of water vapor by the use of information on echo detected by threedimensionally scanning radar is presented. The basic equations are consisted of three conservation equations in terms of the air with the assumption of isotropic convergence, the liquid water and saturated warer vapor with the assumption of pusedo-adiabatic process. The estimated wind field is consistent with the structure of precipitation in qualitative sense and the wind field estimated from dual doppler observation in quantitative sense.

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The application of radar rainfall measurements to hydrologic practices involves many difficulties in identifying radar constants B and β, calibrating radar information via use of ground measurements and so forth. The currently used method compares radar areal rainfall directly with ground point rainfall in spite of the difference of space scale. It is of practical importance to develop a new method which can take into account the space sacle difference for comparing radar measurements with spatial ground information precisely.
The present study converts ground point rainfall to average areal rainfall, using the Kriging method which enables one to estimate the average rainfall over a given catchment area, quantify the accuracy of areal estimates, provide data input for automatic contouring and design the raingauge networks.

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A new numerical model has been developed to investigate the hydrological and micrometeorological phenomena near around the 3D arbitrary-shaped boundary. This model has the following features.
1) Adaptive grid method is adopted to generate the grid system. Using this method, orthogonality and density of the grid are easily and arbitrarily controlled. 2) Momentum, heat, and vapor fields are solved simultaneously. For the parameterization of turbulence, LES model is adopted. 3) Distribution of insolation on the ground surface is considered. The temperature of the ground surface is determined from the energy budget.
The flow near the isolated mountain is calculated and the results get agreement qualitatively with the experimental data.

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Numerical experiments have been performed to investigate the effect of phase change of a working fluid (H₂O: vapor, cloud and rain) on the merging process of thermal convection in the atmosphere. The following results are obtained.
1) The phase change of H₂O promote the merging of thermal convection. The aspect ratio of a convective cell with phase change is much larger than that without phase change.
2) Convective cells merge and change their wave length more often after reaching the upper boundary than before.

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The terrain slope is a real-world feature. In this study, the effect of a slight terrain slope on the flow structure is studied in connection with the problem of the urban heat island by a proposed two-length scale κ-ε model. Findings indicate that even a slight slope can cause appreciable change in the flow structure. The degree of alteration depends on both the slope and the temperature difference between the rural and urban area

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This paper addresses the characteristics of climate change due to global warming using simplified climate model. The proposed model can take into account physics-based climate processes as well as the interactions between atmospheric and hydrologic processes in the mid-latitude. Since the present study simulates only the longitudinal climate change, the computational burden can be significantly reduced. The vertically and longitudinally averaged mean temperature and mean water vapor content between 30°N and 50°N latitudes are considered as atmospheric state variables, while soil and sea temperatures and water storage amount are considered for describing the behavior of hydrologic systems. Special attention is directed to the investigation of the various effects on the global warming using this model. The climate changes due to increasing CO₂ are investigated in some numerical experiments.

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A hydrologic cycle model is developed in order to evaluate water budget and the mechanism of the cycle of water movement within a forested watershed. This model is built by four basic processes, rainfall interception, transpiration, soil moisture and runoff, taking account of SPAC (Soil-Plant-Atmosphere Continuum).
This model is applied to a small forested watershed in Tokushima Prefecture. It is concluded that this model can explain the diurnal and long-term hydrologic trends of soil moisture whose behavior is related to rainfall interception, transpiration and rainfall-runoff.

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For estimation of evaporation rate from large area including a lot of fields which have different characters, for example roughness and wetness, the way how to average evaporation in each fields must be known. In order to estimate the effect of difference of ground surface, the effects of advection and development of internal boundary layer must be investigated.
In this paper, a numerical simulation by a two-dimensional model has been undertaken. In this model, the advection in atmosphere and the ground water flow are included. And some results by this simulation model have been given.

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System dynamics analyses' based on the Air-Plant-Soil Model have been performed to investigate the response characteristics of evaporation and runoff phenomenon to the change of enviromental factors (temperature, humidity, and rainfall).
The following results are obtained.
1) Leaf area density had much effect to the three kinds of evaporation of plant canopies (evaporation from leaf, soil and canopy surface).
2) In the dry atmosphere, evaporation from plant canopies increased in accordance with the temperature, while in moist air, it decreased.
3) When the interval of rainfall became longer (the total amount of rainfall being constant), the ratio of evaporation to the runoff increased.

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It is a well known phenomena that the discharge varies as time in a day time by evapotranspiration suction. This phenomena can be observed in a small upper mountainous basin at low flow stage. The precise observations were taken place in two basins having area 0.18km² and 0.060km². Each basin shows discharge variations clearly. Numerical simulations based on Richards's equation taking acount of evapotranspiration were carried out and the calculated discharge rate were compared with the observational one. The simulation model can explain simple decrease phenomena, but for complex stage as discharge recovery, the model is not sufficient to explain the phenomena.

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In the runoff analysis, not much attention has been paid to the process of flowing down the channeling system embedded in a basin. The existence of the channeling system in any basin all the way up to the basin divide indicates, however, this process to be an important part in the runoff analysis. The objective of this paper is to show how this process governs the concentration process of the basin runoff. A distributed rainfall-runoff model is used for this purpose in which the longitudinal distributions of channel geometry and flow resistance can be taken into account. Firstly, the sensitivity analysis of the parameters governing the channel geometry and the flow resistance showed that the runoff model is quite stable to some of the change of the parameters. Secondly, the effects of both spatial and temporal distribution of rainfall within a basin have been investigated with this model. Finally, the propagation of flood flow along channeling system is investegated to obtain the relationship of the time of peak flow, drainage area at each channel and the rainfall intensity.

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Recently, weather radar and geographic information systems are available to forecast the runoff. It is important to establish the distributed runoff models to make effective use of these spatially variable informations. This paper discusses effects of subbasin scale with distributed runoff models. For this purpose, it is approached that (1) the formula of transmitted channel network geometry under changing map scale in a catchment and the relationship between the properties of subbasin topography and map scales are investigated analytically;(2) the distributed runoff model based on channel network properties is derived. Consequently, the relationship between peak discharge and subbasin scale is derived, and an optimum subbasin scale for hydrologic response is shown.

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For real runoff process, the inputs, the output and the transformations of the inputs to the output may be represented by the stochastic process. Therefore, the runoff system can be described by the random differential equations.
In this paper, we examine the stochastic response of runoff outputs (q) to inputs (r) that is random procam in the runoff system that is described by the storage function model.
The results may be summarized as follow.
The variance (σq²), increases as the value of the storage coefficient (p) and average rainfall input increase.

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The present paper describes practical issues and their resolutions for increasing predictive capabilities of real-time flood forecasting methods. Special attention is directed to explicit incorporations of the water level-discharge (H-Q) relationship and rainfall measurements by radar into the filter prediction formulation.
It is well recognized from hydrologic practices that measurement errors involved in the H-Q relationship are quite significant in flow and water stage forecastiong problems. The current approach proves extremely helpful in assessing the relative importance of modeling and measurement errors, and inaccuracy in rainfall forecasts for flood prediction applications.
For the behavior of watershed response, the present study uses a nonlinear storage routing model converted from the kinematic wave equations where accurate linkages between the parameters for the two approaches are maintained. The proposed algorithms. were applied to the river stage forecasts of the 1988 Flood data in the Uryu River, which is a tributary of the Ishikari River.

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It is very important to investigate the global water circulation and budget for the understanding and the prediction of the global changes. The distribution of precipitation minus evaporation over the globe is estimated by the atmospheric water balance, using the ECMWF global analysis data for the period 1985 to 1988. The calculated vapor flux convergence -∇_H·Q shows good correspondence with former estimations of annual mean evaporation minus precipitation in the meridional profiles. The global annual runoff from land surface to ocean is estimated to be as much as 167 mm/year. -∇_H·Q also shows good relationship with the annual runoff of large rivers, especially in the northern hemisphere.

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During the vertical water migration from rainwater to through-fall and stemflow, almost all of the chemical constituents raised their concentrations, and the most marked substance is the potassium, of which concentration in the stemflow takes the value of more than twenty times higher than the rainwater. In the meantime of passing through the soil zone, the solute chemistries get drastically changed to be stabilized and consequently the variation range of streamsolute concentrations becomes far below those of rainwater, throughfall and stemflow. In addition the element budget in the Tsukuba forested basin showed that the cycling amount of the essential elements available for forest plant growth becomes ten times as high as the input by rainwater and output by streamwater.

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The use of specific electrical conductance of water (C) as a geochemical tracer in flow component separation has been based primarily on certain assumptions about its physical and chemical properties. These assumptions, however, are based on unrelated data, such as in temperature conversions, or based purely on intuition, such as in mixing functions. However, a better approach would be to experimentally analyze these assumptions. This paper studies the basic relationships between C, temperature & pH and also their respective mixing functions. An understanding of these properties would lead to better modeling using C.
This study found that different C-temperature function exists for each kind of flow water source, and a complete sampling is required for an accurate estimate of this function. This study also found that the quality of water should be considered for future studies using C.

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In order to evaluate the buffer capacity of watershed to acid deposition, it is necessary to know both the pathway of precipitated water and the accompanying chemical change of the water. We observed temporal variations in the chemistry and isotope composition of the groundwater and streamwater in a mountainous basin during a storm. Based on these results, we divided streamwater into 3 components; preicipitated water, soil water and groundwater. It was found that soil water runoff through aquifer was an important component in stream discharge and streamwater chemistry in this basin during a storm.

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This paper deals with the water exchange process in two connected lakes, one of which is connected to the open sea. The field observations are made in polyhaline lakes, Myojin-ike which are connected to the Japan Sea by a pipe. The result of the observations implies that there exist water exchange through porous media to the Japan Sea, besides the pipe flow. A simplified model to predict water level variations in two lakes is proposed considering these processes. The calculation shows a good agreement with the observation.

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In snow areas, spring runoff, comprising mostly snowmelt, is the supply source of hydroelectric power and public water. The authors has been made a fundamental experiment to investigate the role for melting process of snow by atmospheric factors.
In this study, spectral analysis according to the above experimental, is applied to the hydrologic daily data of the real basin of the Okutadami dam. As a result of this analysis, daily total runoff component for the period of snow melting are separated, into three runoff ones and it is understood that the correlation between heat flux and the amount of snowmelt is high in the low·frequency domain.

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An evaluation method of total precipitation (snow and rain) volume in the Taki dam basin from a few meteorological points is discussed. This method is based on comparison of snow depth data at observation points with the snow survey conducted once a year. 1) Evapotranspiration and groundwater balance are evaluated by Thornthwaite method and by simple model respectively. 2) Water balance in the basin is studied in snowmelt season. 3) Taking account of the relationship between snow moisture volume and snow area from NOAA-AVHRR data, snow depth distributions is estimated.

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The objective of this paper is to apply the distributed snowmelt runoff model to a basin with no information on snow covered area (SCA). At first, we estimate the spatial distribution of snow water equivalent (SWE) using the snowmelt distribution model on the snow-line already obtained. The changes of SCA during snowmelt season are simulated successfully using the topographical distribution of SWE. The result of application of the distributed snowmelt runoff model including the simulated SCA is in good agreement with observed hydrograph.

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A new distributed rainfall-runoff model is developed to estimate a daily flow including snowmelt runoff.
It is basically a four-tank cascade model. Each cascade tank is corresponding to an element basin with different discretization scale. The discretization scale becames grater toward the lower tank. The runoff from each tank is routed through a quasi-channel network system. The model was applied to the Uchikawa Dam basin. It was found that the model was able to simulate the rainfall and snowmelt runoff.

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