In the field of hillslope hydrology it is very important to understand the spatial characteristics of the soil so as to make accurate lumping representations in modeling. In order to clarify the spatial characteristics of soil permeability in mountainous slope, experiments were made on soil samples taken from the field. In the experiments, 96 undisturbed 10 cm long samples were taken from 35 locations. The spatial variations of parameters of unsaturated peamiability K=K_s(ψcr/ψ)^ηand void ratio n were examined.
Results show the coefficient of variability of Ks and η are small but large for the unsaturated characteristics ψcr and η The corelogram analysis shows the soil characteristics are independent when they taken more than 1 meter apart. Keywords: peameability, heterogeneity, mountainous forest soil, semivariogram

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Effects of surface flow and percolation rate on water path flow through unsaturated media inserted by circle surface were examined. Experimental results showed that convection caused by capillary force go behind obstacle, and that the dispersion of discharge water concentration was influenced by detour water quality. Simulation using ‘water path invasion model’ could produce similar convection only by considering surface flow effect and showed that realistic percolation rate produces considerable non-percolation zone.

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This paper discussed the estimation methods for saturated hydraulic conductivities (ko) of soils under various initial conditions, using borehole falling head tests (FHT). Parameters relating to soil properties were determined by soil tests and preliminary analyses. In addition, an empirical formula specifying the initial condition of the surface soil layer was introduced on the basis of the field data observed by tensiometers. As a result, ko values evaluated from FHT carried out for the dry soils are in good agreement with the values obtained by constant head tests.

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In recent studies, the importance of preferential flow in mountainous slope have become obvious. To model these phenomena, we should explain the saturated/unsaturated flow in large pores. As the first step to do it, in this paper, based on measurements of water content θ and water flux Q of unsaturated flow in smooth- and rough-walled pipes (8mm dia. and 6.8mm dia.), those phenomena was physically explained and modeled. In smooth pipes, the relation between θ and Q was devided into the three domains, laminar, turbulent and transmission flow. Laminar and turbulent flows were modeled physically. In rough pipes, laminar and turbulent flows appeared, and both were modeled. These flows were explained physically as elemental phenomena in preferential flow.

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How to estimate the effective rainfall is one of the important problems unsolved in flood runoff analysis. During a runoff-producing storm, the runoff due to deep percolation of the infiltrated water is analyzed based on unsaturated flow theory and tank model in a experi-mental river basin. Moreover, authors compare the estimated effective rainfall through unsaturated flow theory, tank model and entropy method and find these coincide with each other.

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The Green-Ampt model is generalized to model infiltration into a multi-layered soil during an unsteady rain. One dimensional numerical simulation scheme of the Richards equation is also developed which is suitable to deal with transfers between two kinds of boundary conditions…water flux control and water head control. Modeling results of the generalized Green-Ampt model are compared with a numerical simulation for cases of 2 and 3 layered soil as examples. It is shown that the proposed model matches the Richards equation quite well with computation time less than tenth of the latter, thus promising to play a role in watershed modeling.

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In the case of field measurement of heat and moisture transfer, a surface layer is treated as a finite thickness to obtain the surface temperature and soil moisture content caused by experimental difficulties. Since the discussion of the surface layer from the viewpoint of engineering is not matured, it is customary that when the energy or mass balances at the soil surface are evaluated, the thickness of soil sampling and set-up depth of soil heat flux plate depend on each researchers experience.
This paper aims to propose an appropriate thickness of the soil surface layer by applying α-β method to a surface layer model and present the characteristics of heat energy and mass balances of the surface layer model under the drying process.

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The Heat Balance at Meiji-Shrine Forest, where is one of the largest green area in Tokyo Metropolitan, is observed by botha meteorological (MT) and a plant-physiological (PT) method. 70% of net radiation is distributed to latent heat flux. The diurnal variation of evaporation estimated by MT don't agree qualitatively with that by PT, because the latter is strongly affected by the local meteorological conditions of the sampling site. The characteristics of the stomatal conductance to meteorological conditions can be modeled well by Jarvis equation. The stomatal conductance modified by Jarvis model to exclude the local meteorological conditions, agree very qualitatively with the bulk stomatal conductance estimated by MT.

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Evapotranspiration is one of the most impotant components of hydrological circulation for water resources planning and management. Simple method requiring a few meteorological data which are easily obtained is necessary for analysis on water balance in large-scale area, especially in developing countries. Furthermore, evaporation caused by rainfall interception, and transpiration should be divided, because they are different hydrological processes in themselves. In this study, a simple mathematical models for separately estimating daily transpiration and evaporation in rainfall events were developed. The models were applied to the observation obtained in a small forested mountain basin in Tokushima prefecture, and the validity of the models were investigated.

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Spatial variation of surface heat and water fluxes should be reasonably integrated. In this paper, spatial distribution of evapotranspiration at a bare field and an irrigated paddy field a re estimated. Based on a set of micro meteorological observations at the surface boundary lay er on the fields, bulk transfer coefficients are estimated first. By using the data of field observation, distributions of soil moisture and surface temperature, and the estimated bulk transfer coefficients, evaporation from soil surface and evapotranspiration from paddy field are calculated. The results show that information of the distributed hydro-meteorological conditions is needed for more exact evaluation of the regional average evapotranspiration.

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With the increasing economic growth in the and regions, and with the growing need for new water resources, the demand of new water supply systems for irrigation are becoming high. One of the most water-safe method for irrigation is the trickle method. In this method, water for irrigation must be supplied just on root zone with the help of emitters. The problem associated with the trickle irrigation is the salinization, this leading to such problem as threatens irrigated agriculture, slow infiltration, water logging and crusting. Gypsum has been shown to be effective in reducing the sodium content in soil, but it is inconvenient for trickle irrigation and currently too costly. The dynamics of soil salinization is strongly affected by evaporated water and by plant water uptake. Therefore, any hydraulic solution for reducing the salinization needs a good understanding of the flow pattern and moisture content and their relationship with the evaporation and water uptake by plants under the use of trickle irrigation. The flow pattern and the moisture distribution under trickle irrigation was simulated numerically and experimentally. The hydraulic properties of the studied soils were estimated in this study. To maintain high water content in the upper part of the soil under trickle irrigation, a sub-layer was used beneath the top soil layer and its hydraulic properties were examined.

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A new device for continuous computing and recording of the energy balance terms at the bare soil surface in greenhouses is described with some of its principle advantages and characteristics. Bare soil condition in greenhouses was simulated in this study to understand well the effect of the greenhouses on the distribution of the heat balance terms at the ground surface. The downward net radiation flux was directly measured; sensible heat, latent heat and soil heat fluxes were calculated from the data of the air temperature, air relative humidity, the surface temperature and the air velocity. The results of a field trial over a bare soil surface demonstrate the new device's reliability and operational effectiveness for experimental periods of many days.

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Evapotranspiration is one of the most impotant components of hydrological cycle in forested basins for water resources planning and management. Because transpiration is closely related to soil moisture, it plays an impotant role especially in the time of drought. This study focuses on transpiration decline caused by the limitation of extractable soil water and the increase of vapor pressure deficit. A mathematical transpiration model developed by authors was applied to the observation obtained in a small forested basin and a critical soil moisture at which transpiration began to decline was identified. The proposed model could describe the transpiration decline in the basin during drought periods.

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We developed a method to lump runoff processes of slope systems taking into account a distribution of basin topography. In our method, we measure topographic quantities such as slope length and so on by using the Basin Geomorphic Information System (BGIS), and lump slope systems by using the cluster analysis technique on the assumption that the similarity of runoff characteristics among slope elements is evaluated with that of topographic characteristics. Applying our method to an actual basin, we obtained the following conclusions:(1) Our method reduced an amount of runoff calculation to about one-20th of that without employment of our method, (2) Coefficient of variation of a topographic quantity was valid for the criterion for giving the number of clusters.

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The observed rainfall is described as a random step function whose step height belongs to some stochastic process. On the other hand, the theoretical equations to calculate the first four moments of discharge require stochastic properties of rainfall defined as continuous function. In this paper, it is assumed that the observed rainfall is approximated by the first order autoregressive process. In this paper, authors strictly derive the auto-covariance function for rainfall defined as continuous function and theoretical equations which give the first four moments of discharge based on storage function model.

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In this study we investigate a performance of three layer soil model which is used in SiB model through comparison with the precise vertical resolution soil model. The governing equations of precise model are based on Richards' equation. and modified Picard iteration scheme is used in the numerical calculation.
Assuming the vertical profile of soil moist ure within soil layer and adding the ground water level in prognostic variables, we propose a two dimensional soil model for use in the land surface process models which can treat the effect of topography on soil moisture field and resultant latent heat flux.

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Distributed hydrologic models can be used to simulate hydrologic processes in a catchment considering the spatial variability of catchment characteristics such as landcover, topography and other physical parameters. Remote sensing images provide a very effective means of estimating landcover parameters of a catchment as they can be used to estimate the temporal and spatial variation of a large area at high resolution. In this study different sets of landcover maps of the Agno river basin in the Philippines were derived from satellite images using different landcover classification strategies, which include supervised, unsupervised and hierarchical classifications. The best classification images were judged by aerial photographs and site visits. Hydrological simulations were carried out with a distributed hydrologic model using different landcover maps obtained to identify the model sensitivity to the landcover data and to estimate the changes in hydrologic processes with changes in landcover patterns. Results show different components of the hydrological cycle are affected to different degree depending on landcover information.

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Flow accumulation method is the most common technique used in extracting river networks from digital elevation model (DEM) data. This method allows the extraction of networks with arbitrary density, that is, different threshold areas can be used to generate channel network with different density. Here, the effect of threshold area on width function and area function is examined. The scaling structures of width function and area function are studied using their singularity spectra. With the aid of singularity spectrum, it's easy to identify the differences in river networks resulting from different threshold areas. This paper discusses the stability of width function and area function and the limiting threshold areas for deriving catchment area function.

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A grid square of a meso-scale or macro-scale hydrological model usually includes various kinds of single land-use surfaces (elements). In order to estimate three fluxes from a grid square, fluxes from each element have to be averaged. For this purpose, Scale Issue has been researched by many researchers.
In this paper, numerical simulations were undertaken and considerations about upscaling from micro-scale to meso-scale was also undertaken, focusing on the aerodynamic resistance between the surface and the ‘blending height’. Defining the resistance of a whole grid square by parallel summation of the corresponding elemental resistances, the areal average fluxes were found to be similar.

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The effect of topography to severe rainfall from cumulus, cumulonimbus is investigated numerically. To represent bottom topography in AE-type primitive model, we use σ-coordinate and tensor analysis. The Poisson equation translated into σ-coordinate has been solved numerically by using FFT and a iteration method. We obtain reasonable result from this method. Knowledge about effect of topography on severe rainfall is obtained from investigation of the numerical result. A couple of knowledge are:(a) Low topography functions as a trigger of cumulus but takes no effect on cumulus after it activated.(b) Downdraft and precipitation particle dropping caused by high topography prevent cumulus from developing.

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Numerical simulations of Mesoscale wind fields and cumulus clouds in summer over Kanto region have been performed using RAMS (Regional Atmospheric Modeling System). This non-hydrostatic model include the advanced technique of weather prediction;(1) the microphisics parameterizations;(2) multi-grid nesting;(3) FDDA (Four Dimensional Data Assimilation). A total of three numerical experiments lead the following results.(1) The results of wind fields agree well with AMeDAS data.(2) Local wind fronts and clouds are simulated by nesting grid system.(3) The cloud over central Japanese mountains area agree qualitatively with the image from NOAA.

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Purposes of this study are to represent a cold air which occurs on the land surface in winter seasons and to calculate cold air flow on Feb. 17-18, 1996 when snow clouds acompanying a cold air flow appeared around Ishikari Bay. We assumed that a cold air is caused by radiative cooling effect and differential equations are given considering bouyancy effects. By Kaito baloon observation a cold air flow extended to Ishikari Bay the best at 6:00 on Feb. 18. Numerical calculation result indicates that an extended front shape of a cold air flow which causes snow clouds by an ascend wind agrees with an acutual snow clouds' shape at 6:00. And we found that a resistence coefficient between a cold air flow and monsoon and an upper wind are important to predict an extended cold air flow.

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In urbanized areas, heavy rainfall in short periods of time and in small areas can potentially result in extreme damage. It is important, therefore to estimate the short duration PMP (Probable Maximum Precipitation) which takes heavy rainfall into consideration when planning for river management in or near urbanized areas. In this study, traditional methods for PMP estimation are reviewed, and a new method for short duration PMP estimation, which uses a one-dimensional cumulonimbus model developed by Ferrier and Houze, is proposed. In this method the authors introduce the concept of rainfall potential which allows for the analysis of heavy rainfall. Finally, we show the capabilities of the newly proposed method.

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The rainfall intensity on the ground is usually not equivalent to the rainfall intensity estimated from the conventional radar. To improve the accuracy of the radar-estimated rainfall, we observe and analyze the vertical profile of the rain drop size distribution (DSD), then create a new formulation of the vertical profile of DSD. Based on the obtained information, first, a new formulation of DSD which considers rainfall type, rainfall intensity and observed DSD from the Disdrometer is developed. Then, the analysis of the vertical profile of DSD in the selected rainfall type is carried out to investigate the possibility of determing relationships among parameters for the DSD.

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The characteristics of meso-β scale rainfall observed by a single Doppler radar are presented. Horizontal wind is estimated by VAD analysis and obtained from upper-air chart. AMeDAS data is also used with analysis of rainfall characteristics. We obtained the following results.(1) The direction of vertical shear of the prevailing wind is parallel to the rainband.(2) The rainband is formed by several cells which are composed of cumulonimbus clouds.(3) Relative warm air on the ground was supplied from the side or front of the rainband.(4) Convective clouds with a great echo intensity stand in vertical direction and clouds above that tilt to the windward, when the direction of vertical shear of the prevailing wind changes in altitude.(5) Rain layer with a great echo intensity was formed by a strong updraft.(6) the advection velocity of rainband was the same as one of the prevailing wind at 6km in altitude which is at the top of radar echo.

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Rainfall is the most important and direct agent that causes flood disaster. It is therefore the flood forecasting essentially depends on forecasting of rainfall. With radar rainfall data remotely observed by the Foundation of River & Basin Integrated Communications, i. e. FRICS, a new methodology is developed for accomplishing short-term rainfall forecasting, wherein two main components are included:(1) settlement of rainfall vector movement with modified correlation method and Fuzzy rule, and (2) determination of spatial and temporal distribution of rainfall intensity using neural network (NN) approach. Reasonable results have been derived with a high accuracy through rainfall data on a real time basis.

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In this paper, the time-space characteristics of the runoff system in small urban river basins is made clear, using well-observed rainfall and water level data. In urbanized area where sewer system are complete equipped, rainfall-runoff relation is extremely direct. In other words, the rainfall is collected into the rivers so efficiently that the flood in the downstream would rise rapidly. Future application, of the gained knowledge, in urban rainfall drainage management is also examined in this study.

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To achieve advanced control in sewer systems, operators should be provided with computer-aided control systems. In the present study, genetic algorithms were applied to the learning of fuzzy control rules used in a combined sewer pumping station. Pumping rates were determined by fuzzy logic controllers using input variables such as rainfall intensity, sewer water level, and river water level. Genetic algorithms involve the procedures of selection, crossover, and mutation. After evaluating the effects of parameters, fuzzy control rules were efficiently improved to fit pump operation conducted by human operators.

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A neural network is developed to forecast flood discharge. Network training is conducted using back-propagation with simulated annealing, where rainfall and discharge data as input and discharge data as output. These hydrologic observation data are generally included in various types of errors, so we applied fuzzy theory to these data including errors. After training is completed, the neural network is used to forecast for 3 and 6 hours ahead using only the current observation data as input. The authors have shown that fuzzified neural network is capable of learning the complex flood runoff process and can get reasonable estimations.

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KT Model is a daily natural runoff model. I propose it and show it's good results in NAGARAGAW so Acalled natural river. It's very simple model with only one constant K relating to basin recharge and recession in low-water. The daily natural runoff is dtermined by the daily precipitaion and the daily air temperature. Loss in natural runoff is evaporation. It refers to air temperature. In this basin I obtained K=30 and a relation of evaporation and air temperature E=1.03+0.083T.

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As the first step to evaluate sediment transport in the Abukuma River basin, arainfall-runoff model has been developed to reproduce runoff phenomenons of the basin. This model considers not only overland flow but also infiltration, throughflow and exfiltration to aproach praticical phenomenons on the hillslope. A runoff computation of throughflow is practiced utilizing continuous equation and Darcy's law changing some parameters. The computed hydrographs with or without throughflow are compared with observed data, and the validity of this model and the effects of throughflow on the hydrograph are examined.

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This study focused on the runoff characteristic of total nitrogen and phosphorusduring a storm event in a forested basin. The stream water was separated into four runoff components using a tank model, and the correlation between those components and the temporal changes of stream water concentration of total nitrogen and phosphorus was investigated. It is clarified that stream water concentration of total nitrogen and phosphorus are formed by the temporal change of runoff components. Then, the modeling of runoff of total nitrogen and phosphorus from a forested basin is employed using a tank model.

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The hysteresis shown in specific conductivity (SC)-discharge (Q) relationships during rain events has been previously utilized to verify the presence of preferential flows of new water. This series of observations were made in a catchment where isotopic data have shown that stored water is the predominant outflow during rainfall events. The SC response during rain events and a laboratory column test complemented the conclusion of isotopic study, viz. the runoff mechanism is discharge of stored (non-event) water. It is shown that any runoff mechanism giving a higher SC in the falling limb of hydrograph (for the same Q value) will generate an and clockwise hysteresis in the SC-Q relation, even in the absence of a preferential flow of new water.

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Predicting runoff using a kinematic model has become a useful tool, but to model this process special care must be taken when the infiltration for a given event is estimated. In this paper, hydrographs due to runoff with different initial infiltration capacity of soil and various types of rainfall are discussed for a Brazilian semiarid area using data obtained from a test field in the area. In the discussion, the Green and Ampt infiltration equation during a steady rain is used and the moisture-tension parameter is studied separately. Thus a new method for estimating this parameter for a Brazilian semiarid area is proposed.

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The specific discharges of the mean annual flood and the mean annual lowflow were compared in different rivers in Southeast Asia and the Pacific. It was found that the specific discharges of the mean annual floods have two groups, relatively high and relatively low while they as a whole show a decreasing trend with the size of catchment. Most rivers that belong to the relatively low group are under the influence of reservoir regulation upstream. The specific discharges of the mean annual lowflows have also two groups, one concentrated around 0.1-1.0m³/s/100k²and the other below that range, both decrease slightly with the catchment area. They were found dependent on the dryness of the region and the reservoir regulation. Few unregulated rivers seem to show the influence of land cover such as forests, paddy fields and base rocks. A dryness index, m/n, the number of months that have the mean monthly rainfall less than 10mm and 30mm, was introduced and shown operational.

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Runoff from semi-arid zone shows some distinct characteristics, for examples, rivers are ephemeral and channel losses are usually very arge. This paper makes clear these characteristics using the data of rainfall and runoff stations in semi-arid zone of Kenya. The main results are;(1) the potential of evaporation is around 3000mm/year whereas raiofall amount is around 300mm/year, (2) intensity of channel loss is about ten times of potential evaporation, (3) in spite of semi-arid zone, sone rivers are perennial, and the source of flows are supposed to groundwater from volcano, nanely M. Kikimanjaro.

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Meteorologicaol bservationand measuremento fheat and moisture in soil are carried out in an experimentalf ield at United Arab Emirates (U. A. E.) T. he purpose of this experiment is to make a model of heat and moisture transfer in soils for saving the irrigation water in arid region.
The movement of water vapor in soils is evaluated by the experimental technique using thermo-hygro meter, which is developed by authors. This technique is useful for the monitoring of evaporation-drying process of soil after irrigation. The characteristics of temperature, humidity and water vapor density profile in soils are similar to those observed by indoor experiments on the evaporation from sand layer under diurnal climate variation.

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A physically based distributed mathematical hydrological model has been developed. In this model, the hydrological processes of water movements are modeled either by finite difference representation of the partial differential equations of mass, momentum and energy conservation or by empirical equations derived from different research. Main processes of hydrological cycle, such as overland and river flow, unsaturated flow and ground water flow are modeled by St. Venant equation, Richard equation and Boussenq equation respectively. The model is applied in Ping catchment of Chao Phraya river basin, Thailand. The catchment area of the basin is 6, 300 sq. km. The results show the good agreement between simulated andobserved hydrological responses. The preprocessing and post processing of the data are done in GIS. An interactive software has been developedf or data input.

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The objective of this study is to investigate heat and water transfer processes over the permafrost region. For this analysis, we develop a 1-D energy and water transfer model which can consider permafrost hydrogical processes, and apply it to the permafrost region on the Tibetan Plateau. The result of analysis indicates that the model which is developed in this study can represent heat and water transfer and the active layer depth accurately. By using this model, the impacts of climate change on the permafrost hydrological processes are demonstrated.

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The objective of this study is to retrieve regional snowfall distribution from standard meteorological data and remotely sensed snow covered area using a distributed hydrological model. Two snowfall models are implemented into a distributedhydrological model to simulate snowfall, snowmelt and runoff processes during a complete snowfall-snowmelt cycle from Nov.1, 1992 to May 31, 1993 over Uono River basin. Hydrographs and images of snow covered area are derived for various sets of parameters in snowfall models and compared with the observed ones. In order to select parameters, a criteria is proposed to consider errors of both hydrograph and snow covered area. Using this criteria, reasonable parameters which represent the regional snowfall distribution are obtained for above two snowfall models.

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The purpose of this study is to develop a model to estimate the density of snowpack in wide area. Numerical model, which is based on heat balance model and considers consolidation process, is constructed to investigate the snow density variation at various regions. This model is applied to over 200 AMeDAS points in Japan and are results are compared with observed data. The relationship between snow density variation and other factors, which are snow depth variation, maximum snow depth and minimum temperature, is investigated using the calculation and theestimation model on the snow density in wide area using snow depth variation.

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In this paper, we improve the two-phase mixture model which we proposed in the previous paper: Assuming a non-linear relation between the moisture of free phaseand the infiltration flux within snowpack, we add an upper limit and a lower limit of moisture of trapping phase and estimate the model parameters by a method based on the least square method.
As a result, we find that the non-linear model agree much better with the experimental results than a linear model. Moreover weexamine the transition of moisture profiles of infiltration process.

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Spring runoff is mostly comprised snowmelt and is very important on water resource as public water and etc. And Many studies have been conducted on forecasting and estimation of snowmelt volume.
In this paper, firstly, characteristic ofsnowmelt runoff is investigated using spectral analysis. Next, Snowmelt water is estimated by Heat budget method that takes in planting cover information in the Yuda basin. And it is investigated that plant cover distribution have influence on snowmelt water. It is clear that it is necessary the information of plantcover distribution of theriver basin in the analysis of snowmelt water.

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In recent years, it has become important to consider environment around the constructed river according to the demands of the citizens.
Now, we are constructing the fishways considering hydraulic characteristics and ascending effectiveness in Akigawa River.
This paper presents a summary of the field reserch according to the velocity measurement and other observation in the fishways.

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Previously, fishways were designed to assist migration of only commercial fish. However, new emerging concept of river environment management requires fishways to provide “biopath” for many species of fish. In this paper, the new methodology for fishway design is discussed. IFIM (instream flow incremental methodology), which was derived for habitat evaluation, is here developed to apply to fishway evaluation. Not only the hydraulic condition of flow in fishway but also the influence of time series of discharge are taken into account to evaluate the fishway design. The procedure of the methodology is explained for an example of fishway of triangular section with large roughness.

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It is required for hydraulic engineers to manifest the hydraulic and environmental characteristics of riffles and pools. We conducted a field observation at Aki-river in Akiruno-city in Tokyo on 11 and 12, Sept.'96. In the observation, the spatial variations of hydraulic and environmental characteristics were measured in detail using various devices. It is found that the both of the diameters and the standard deviations of the large scale channel-bed gravels are the important factors in determining the texture of water surface. The amount and spatial variation of dissolved oxygen is governed mainly by the photosynthesis of waterweeds growing on the gravels.

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The ecological investigations on fiddler crabs (Genus Uca) have been conducted on the Sumiyoshi tidal flat in the Yoshino river mouth from 1993. This flat is one of a paradise of Uca arcuata and Uca lactea lactea which are specified to the rare species on the reddata book. This paper reports the results of inhabitant surveys of crabs (which include 1) active individual densities, 2) mud properties at their habitats, 3) sampling of crab larvae) and numeric calculation of the dispersion process of the crab larvae just after the larval release.

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This paper proposes a effective method using eve for the selective withdrawal from two layered system. Experimental studies were conducted on its effectiveness. Flow field effected by the eve was studied using the flow visualization technique and classified into three types. The experiments also revealed the two mechanisms of effectiveness, namely due to, (1) separation of withdrawal line, (2) energy dissipation caused by the eve.
Finally, this paper proposed the equation for the field design which could give the most efficient position and the width of the eve for the selective withdrawal from the two-layered system.

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The diffusion behavior of a horizontal buoyant jet discharged from a multiple pipe was investigated both experimentaly and numerically. Velocity and temperature of the jet were measured with FLV, thermocouples and propeller velocimeters, changing the number of pipe and the height of an outlet and the distance between the pipes. In each cases, a three-dimensional turbulence closure model (k-εmodel) was applied to simulate the behavior of the jets. The performance of the three-dimensional model was evaluated by the comparison of the numerical results with the experimental measurements.

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A three-dimensional k-εmodel was applied to calculate the diffusion of a forced plume in a coastal area, and the field observations were conducted to investigate diffusion process of a forced plume. The results of the calculation showed that the vertical eddy viscosity, the direction and the longitudinal distance of forced plume diffusion agreed well with the observation data.

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