The present study deals with the investigation of wind velocity observed by the Doppler radar. The first phase of paper is the observation of wind using the Doppler radar. Observations have been carried out by using the Doppler radar which is installed in the suburb of Sapporo, Hokkaido, Japan. Horizontal and vertical wind components are estimated by applying the VAD (Velocity Azimuth Display) method to the Doppler data. We make sure that the VAD method can precisely estimate the wind components. The second phase is the utilization of wind data for investigation of rainfall field. The geostrophic wind observed by the Doppler radar is incorporated into the Kao model so that three dimensional wind components are estimated in the planetary boundary layer. The rainfall field is simulated by applying such wind distribution to the Kessler parameterization. The above methodorogy offers considerable promise for the progress of physics-based rainfall models and forecast methods.

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The raindrop size distribution (DSD) was measured with electro mechanical disdrometers. The measurements discussed here contain around 10, 000 distributions, each registered as 5 minute mean. Different types of precipitation at different locations have been used from the period of 1988-1990.The dependence of the DSDs on rainfall intensity was analyzed and the Z-R relation was estimated using DSD parameters and various regression method. Results indicate DSD derived Z-R relation is not always better than regression methods, and the estimated DSD parameters were different between DSD derived ones and Z-R derived ones. One of the Z-R regression method, quasi-least-square method, was applied to the on-line calibration of Z-R parameters, and the capability was pointed out.

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he application of radar rainfall measurements to hydrologic practices involves many difficulties in identifying radar constants B and β, and calibrating radar information via use of ground measurements and so forth. It is of practical importance to take into account the space scale difference for comparing radar measurements with ground information precisely.
The present study converts ground point rainfalls to the average areal rainfall, using the Kriging method, and shows its effect on the identification of B and, β, and calibration.
The Kriging method enables one to estimate the average rainfall over a given catchment area, quantify the accuracy of areal estimates, provide data input for auto-matic contouring and design the raingauge networks.

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he temporal and spatial distributions for radar rain can be analysed by fractal theory. The fractal dimensions of the storm are calculated by the box counting with an average 1.38 for the perimeters of rain, and the range between 1.5 and 1.9 for the contours of rain rate. Moreover, the dimensions for the spatial and temporal distributions are derived from the scaling of rain field with the range 2.7 to 2.8, and the range 1.6 to 2.0, respectively. The latter values coinside with those for the contours of rain rate. By using the above results, the predictional simulations for rain random process are calculated with the midpoint displacement technique.

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The study is based on the precipitation data measured by densely distributed raingauges. First, a small-scale, short-term thunderstorm is analyzed by Isohyetal, Thiessen and weighted distance method. Then an index of raingauge network density in an urbanized small river basin is proposed and the degree of areal-rainfall estimation errors in each method is made clear.

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Steadiness and homogeneity of hydrological quantities are mainly assumed in a customary stochastic analysis. This study gives reconsideration to this assumption, through checking homogeneity of shape of frequency-distributions. Judgement of homogeneity is given by AIC on the basis of multinomial-distribution model. If every distributions are judged not homogenous, practical grouping of those distributions is proposed by the same method.
Numerical calculation is carried out with daily precipitation in Gifu city from 1891 to 1990. It is shown that six-parts dividing model in order of maximum daily precipitation is most suitable.

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In this paper, basic structuers of rainfall prediction models based on multi-point time series data are studied. According to medium-and meso-scales of precipitation areas, the life spans of precipitation are assumed to consist of two spans longer and shorter than eleven hours. It is concluded from studies based on multi-point data over Western Japan that the product form of regressive models for the long and short components is best. The accuracies of the prediction models for various (1-, 3- and 6-hour) lead times are shown.

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The design rainfall is usually determined based on the probabilistic characteristics of point rainfall. Spatial distribution of rainfall, however, plays an important role in run-off process. This paper discus the spatial characteristics of rainfall and proposes a simulation algorithm of design rainfal.
A Fourier series is used to express the rainfall field. In the equation, the linear term is connected to the volumetric design rainfall and Fourier coefficients and phase angles are discussed.

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This study presents an extension of the discrete stochastic model used to justify anisotropic bivariate hydrological quantities such as precipitation or runoff discharge in dry season. The theory of discrete distribution is obtained in the form of bivariate binomial distribution and bivariate negative binomial distribution. In those two type of distribution, bivariates have different parameters and correlation. The estimation of parameters is discussed by separating marginal and joint distribution in a maximum likelihood method. The results applied by negative binomial model prove to fit well for the data of runoff discharge series.

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Conditional probability distributions of runoff discharge and water storage at a flood control reservoir given several hour lead forecasted rainfall intensities are theoretically derived using expectation techniques on the linearized relationship of storage function between rainfall and runoff intensities and on the relationship between runoff (inflow), outflow, and water storage of the flood control reservior. By simulation based on this theory, significance of rainfall forecasts with various levels of accuracy is investigated.

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This paper presents an optimization method for finding noninferior solutions of multiobjective multireservoir problem with stochastic inflows. Constraint technique, decomposition iteration, and simulation analysis are conjunctively used to deal, respectively, with multiobjective optimization (or vector optimization), large-scale multireservoir system, and stochasticity of inflows, which represent three difficult points in water resource systema nalysis.T he effectivenesso f the method is justified by applying it to the modeled multireservoir system in Tone river basin.

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If the hydrological characteristics of river basin is obvious, high level prediction of inflow to flow in reservoir can be performed. On the other hand, the automatic operation of dam is generally desired to lighten works for administrator controlled of dam. Fuzzy theory can be applied to the operating system of dam which is difficult to be expressive by numerical formula.
In this paper, the possibility of the application of fuzzy theory to the operating system of dam is investigated comparing the results simulated by fuzzy theory with the results operated by actual operator.

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In this paper, two different approaches to forecast runoff using the fuzzy inference method and neural network (NNs) are described. The actual applicability of this two methods is assessed and compared through making 1-hr, 2-hr, 3-hr lead time forecast of runoff in BUTTERNUT CREEK, NY. The good results indicate that both of these two approaches are very effective for runoff prediction.

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A system for operating many sluice ways located along retarding basins using a real-time runoff prediction scheme is developed. In the Ueno Retarding Basins (area: 250ha, pondage: 9.0 million m³) in Japan, there are thirty-six sluice ways andduring a flood at least seventy-two operators must stand by to operate the sluice ways. But it has been very difficult to arrange such many people. In this system, to operate many sluice ways one after another with as few people as possible, the stage of the river at each sluice way is predicted on a real-time basis and the time when the stage rises up to the operation stage at each sluice way is given. For the flood data from September 19 to 20 in 1990, this system was simulated and the time when the stage of the river rised up to the operation stage ofeach sluice ways was predicted and compared to the actual operation time.

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This paper presents the methodology to obtain optimal reservoir operation for water supply by use of Drought Duration Curve (DDC rule curve). Optimum DDC rule curve is chosen in comparison with drought safety indices. New method named Staged DDC rule curve is adapted to lessen the possibility of reservoir exhaustion and excessive water saving. Inflow forecasting can be incorporated with DDC rule curve for the improvement of reservoir operation.

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A set of DDC·FDC Rule Curves for Bhumibol and Sirkit Reservoirs in Thailand weredeveloped. The concept is applicable for operation of large reservoirs in any tropical monsoon region with rice paddy agriculture. They assume that the irrigation demand for a reservoir is reciprocal to inflow to the reservoir, which was remarkably well satisfied in the Bhumibol Reservoir in Chao Phraya River Basin. DDC·FDC Rule Curves are so named since they are the solutions of a chance constraint reservoir operation model where drought duration curves (DDC) and flood duration curves (FDC) were used as deterministic equivallence of sum of future streamflows. The obtained rule curves suggested that the Chao Phraya reservoir system was not large enough to provide as much water required now. In order to hold a 5% failture rate, with the storage of 1990 and 1991, as much as 60% of supply cutmay be necessary.

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For real runoff process, rainfall input, output (discharge) and its transformation system of the input to the output may be represented by a stochastic process.Therefore, the runoff system can be described by random differential equations. In this paper, authors theoretically derive differential equations to calculate the first four moments of the stochastic response from a storage function model to a stochastic rainfall input.

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A numerical run-off model is presented as a tool for planning and management of a distributed system of smallscale rain storage facilities in urbanized catchment area. The model has the following features: Artificial channel networks are automatically constructed from digital altitude data. It eliminates a troublesome process of data install and saves a time of computation: Function of storage facilities is easily taken into account. The model was successfully tested at Shiogama City in Miyagi Pref.

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This paper studied the drainage capacity of rain water drainage system in urban areas. For this purpose we used the linear response model developed for urban runoff analysis and then introduced a linear response relation between rainfall and discharge. Using this relation we produced the method to estimate the drainagecapacity of the system of drainage pipes with previously known hydraulic properties. The estimation method proposed here was carried out in the drainage capacity analysis in Nagayama catchment area, Tokyo, and proved to be applicable for urban runoff control.

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In this paper, runoff simulation for urban sewer system using SUM combined with computer mapping is discussed. The metho d of input-output data formation for SUM is modified using computer mapping. To reduce the computation time and capacity, the effect of the simplification of sewer system on the results of simulationis examied as for EXTRANof SUM and the comparison of the runoff computation accuracy of RUNOFF with kinematic wave model is carried out as for RUNOFF of SWMM.

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Frazil ice is an ice crystal formed in turbulent water. Its production is closely related to the ice cover formation in rivers and gives severe trouble for water intakes during winter. Field observations of frazil ice formation and water temerature were performed in Yubetsu and Niuppu river in Hokkaidou to investigate conditions for frazil ice production in rivers. From these observations it is concluded that massive production could occur when the daily air temperature is less than -7.5°C, and suppercooling of water is an indication of frazil ice initiation. A variation of hourly water temperature is simulated favorblly by a simple model using air temeperature as an input.

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Ice process of Lake Ogawara in Aomori Prefecture is observed for 1983-1986 winters. From these observations it is concluded that the complete ice cover is initiated when wind stress on the primary ice sheet is not sufficient to fail the sheet by bending at the shore. The sheet thickness for a day is calculated for air temperature.
Proposed criteria for the formation of complete ice formation of the lake gave a satisfactory explanation for observations.

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The cold region river forms a large quantity of frazil slush during the winter period. Frazil slush often causes the clogging of the intake structure at water-power plant. So we developed the ice control structure, it is proved that the installation of the structure prevents the trouble of the intake structure. In the present report, we describe the relation between the growth of the ic e dam and water temperature, and frazil slush accumulation is proved to depend on the installation of the ice control structure.

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This paper presents an attempt to apply the weekly weather forecast data for a snowmeltr unoff prediction. The basin is 1.0km² in area and elevation ranges from390 to 800m above sea level. The snowmelt model makes use of digital terrain data with 20m grid spacing. Energy balance components are calculated for each grid element taking topographic variations of solar radiation into account. In ordar to use the snowmelt model in the forecast situation, it is necessary to predict the meteorological data for any future time period. In this study, 1) the insolation is calculated by the forecasted percentage of sunshine, which is divided into 15 weather conditions; 2) and the temperature is calculated as a function of time elapsed. One week ahead forecasting results by the snowmelt runoff model using the weather forecast data are accurate enough for practical purpose.

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The spatial and temporal variation of energy budget on the snow surface were investigated at four experimental sites from March to June in 1992. The parameters in the energy budget equation describing snowmelt were determined based on the observated data at each site. The result of energy budget for each site showed that the ratio of the radiative and turblent energy to the whole depend on season and topography.

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Snow volume in Tohoku district is evaluated by using measured snow covered area and snow depth distribution model. Snow covered area is detected from NOAA/AVHRRda ta by authors shceme. In order to obtain snow distribution of whole Tohoku district, a new method is used to composit three different images. The snow depth distribution is studied empirically. The dependency of snow depth on height, latitude and longitude is comfirmed by referring AMeDASda ta. Combining above methods, snow volume in Tohoku district at the first ten days of Feburary is estimated.

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This study investigates the assesment on the development of golf links in terms of the headwater conservation function. Mathematical runoff model developed by authors are applied to a virtual basin based upon Shirakawadani experimental basin in Tokushima prefecture, and simulates the change of daily runoff discharge in various conditions concerned with the infiltration and water retention capacities. The reduction of the capacities by the development of golf links cause the accelerative decrease of daily runoff discharge.

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Based on 500 boring data, counter maps of upper boundary of gravel layer and lower boundary were made. From each map, this aquifer North area has deep and wide trap and South area has small pitches.
Discharge and EC are observed at 10 springs in 1991-1992, runoff stability defined by monthly mean discharge and mean EC values are corrected to gravel layer depth (GD).
From the relationship betwee n discharge and EC, spring systems are divided into dilution type and multi-storage type.
These types are strongly affected by topography of lower boundary gravel layer.

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The flow mechanisms of the tidal rivers are very complicated and these are different from general rivers. The Takase River is important in the southeast of Aomori Prefecture and its estuary is a typical tidal river. We had measured the velocity and the chlorideion distributions of this river for the past three years. Furthermore, we measured the velocities, the chlorideion concentrations and water temperature at frequencies of 0.5Hz in September, 1992, and calculated the power spectrum using the these values.

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Large eddy simulations with meshes fine enough to resolve the roads have been performed to investigate the characteristics of convective boundary layer over Otemachi and the Imperial Palace as an example of urban area. Nondimensional profiles of mean temperature and turbulent intensities agree well with experimental data, and it is shown that the vertical convection and the entrainment are more effective when the ground surface is heated uniformly. It is also shown that many thermals grow up from the asphalt roads while the down stream region are generated around the Imperial Palace.

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Meteorological field observations were conducted at Am-river in summer to evaluate the effect of urban rivers on microclimate of the adjacent city region. The observation in the river course consists of measurements on velocity, temperature and humidity profiles by using captive balloons and measurements on momentum, heat and vapor fluxes performed on flood plain and water body. The development of internal boundary layers on vegetated flood plain and water surface associated with cooling of the atmosphere were observed. The role of flood plain and water body in heat exchanging process are discussed based on the results of the flux measurements.

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Field observation was carried out around the Turumi river and in the Tama river to estimate their cooling effect on the thermal environment in the surrounding area. The hourly measurement of air temperature distribution revealed that the affected zone by the Turumi river was restricted to the region close to the river course. The infrared thermal image sensor was applied to identify the correlation between the land cover and the surface temprature in the Tama river. It was found that at noon the surface temperature was the highest on revetment works, then pavements, playground and the lowest on grass field.

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To evaluate the effect of river and canal on thermal environment, we performed the field observation at the Tama River and the Shibaura Canal. The detailed measurement of vertical temperature distribution within the river and the canal and measurement of urban temperature along the street crossing the river and the canal were carried out and horizontal extent of cooling effect were confirmed by these observation. In the Tama River, the cooling effect is restricted in day time, while in the Shibaura Canal, this cooling effect appeared in night time.

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Global warming resulting from increasing concentrations of atmospheric carbon dioxide and other trace gases may alter various hydrologic process in drainage basins. The global effects on water resources may depend on characteristic of each region, precipitation and vegetation, etc. So present flow regime is compared in three basins, which is dominated by different major phenomena, rainy season (baiu), typhoon and snow accumulation and melt On some scenarios, sensitivity of water resources is evaluated at each basin by an index of dam necessary capacity to secure necessary flow at downstream point to examine global warming effects and the differences are compared in three basins.

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Vegetation in rivers is a key to improve a favorable river environments to provide amenity space or space for various wild lives, but it brings an undesirable effect during flood. Recently, hydraulics of flow with vegetation is studied from the above-mentioned view point, but there is few informations about how the vegetation zones grow in rivers naturally, how they can be controlled artificially, how they are idealized in fundamental analyses or experiments in laboratories. In order to accumulate informations to answer the above questions, field survey of species and growing patterns of plants related to flood-plain morphology is conducted in the river Tedori. The survey data are inspected to clarify the relation among vegetation characteristics, river morphological characteristics and the time series of river discharge.

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While the water plants in small rivers through city play an important roll on the environment of rivers and have a function to purify the water quality, the water plants increase the roughness of a water channel. In Nikaryo channel passing through Kawasaki city, we surveyed the distribution of water plants and measured the velocity profiles at cross-section with water plants. It was revealed that the states of water plants varies with the passage of time and the area occupied by water plants becomes the dead water zone. And it was showed that the longitudinal water level distribution could be evaluated, applying the sheer stress model using the boundary mixing coefficient to the flow in the open channel with the water plants, and Manning's roughness coefficient N of the flow with water plants is about 0.08.

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Lately Low-water discharge had become the centre of wide interesting the urban river. In the present report we have studied the methods of estimation for “Shinsui” water discharge (water level).
The summary of the result is; Firstly, We studied the methods of estimation for hydrological statistics grounds.“Shinsui”water discharge gave definition to average 275 day discharge of period of ten years.Secondly, we obtained the methods of estimation on the lands scape assessmemt and on the photograph of urban river difference from discharge.Thirdly, we obtained the methods of estimation on the ecological grounds, and we obtained a map of relation between hydroulic condition and ecological condition. and Finally, The methods of variable flow by the time and space was obtained.

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In recent years people have become to take a great interest in riversides, especially, those function as a place for enjoying leisure activities. Therefore not only flood protection and water usage but also the river environment must be considerd in the river improvement plan. It is necessary to investigate what awareness and requirements people have for the river environment. In this paper we describe the results of the questionnaire survey on the inhabitant sense for the river environment carried out at two urban river catchment in Kanazawa city.

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Evacuation is one of the most important flood disaster mitigations. It is necessary to know the actual condition of evacuation for its simulation and planning. However, evacuation has different actual conditions according to flood plain conditions which are flood plain gradient, inundation depth, and so on. We have questionnaires with relation to actual evacuation in the two river basins, namely, the Mifune and the Rokkaku river. People there suffered considerable losses from flood in 1988 and 1990 respectively. We analyze the answers, then we get evacuation velocity, evacuation ratio, etc.

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A computer model is developed which can simulate the changing process of inhabitant's consciousness on flood disaster due to flood experience and time passage. In order to express the consciousness which influences refuge actions, two parameters are introduced:“outlook on flood disasters” which express usual consciousness on flood damage, and “information dependency” which express the effect of information on individual actions. The process in which these parameters are changed by flood experience and time passage are expressed by fuzzy inference rules. The model is installed in Flavor system of Common Lisp as an object-oriented model and is applied to the refuge simulation in Nagasaki City.

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Four thousand years ago, ancestors of China had used the spreading measure to mitigate flood damages in the Yellow river. Later, this measure formed an effective system in flood defense together with levee projects. Nowadays, many reservoirs have been built for flood control. However, it is difficult to build reservoirs in the middle and downstream of main rivers in China. The utilization of spreading and detention areas (SDA) are an effective way to mitigate extraordinary floods, but this is accompanied with the severe social problems. For the tradeoff of SDA is difficult to estimate, this measure is still in argue. This measure has been practiced for many years and still be used in China. In recent years, with the advance of flood forecasting and reservoir operation, SDA got effective. This study focus on the SDA in 4 main rivers of China, a comprehensive study is made concerning with the historical, the geographic, the climatic and the social conditions. Major problems of SDA are discussed.

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The chemical changes of groundwater and springwater were observed in the Tsukuba experimental forested basin. The springwater holds a chemical feature that the concentration becomes lower in SiO₂ and larger in NO₃-N than the groundwater. Rather the springwater seems to have the chemical feature close to the forest soilwater. The result proves that the springwater originates from the soilwater runoff as an interflow, and gives the full interpretation to the NO₃-N runoff behavior during the storm events, i.e. the NO₃-N concentration in the streamwater during the recession limb overshoots the baseflow level prior to the runoff event. In addition, the soilwater suction was investigated, using newly devised tensiometer. The tensiometer detected upward water flux in soilwater, which raised the marked increase in the springwater discharge.

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This paper reports on a preliminary study for improvement of a lake with springs in an urban area. Water balance, water quality and bottom sediment were examined. The flow rate was measured at 25 sample sites around the lake from Dec. 1991 to Nov. 1992. The water flow rate was ca. 520000m³/d during the experimental period and the spring rate about 90%. The water quality in this area is dependent on the springs. It is marked by a heigh concentration of No³-N and Po⁴-P. The amount of bottom sediment was ca. 10000m³ in KE-lake. The physical and chemical properties were simillar to Andosol.

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Unusual growth of undesirable algae caused by eutrophication has brought water quality problems of water bloom or odor in some reservoirs. Countermeasures against the phenomenon are to understand a growth mechanism of the algae and to prevent undesirable floating algae from rapid increase.
The water purification system proposed in this paper provides an environment to grow desirable algae, filamentous algae, which works to remove T-P and T-N from the river pouring into thereservoir and inorganics from the reservoir surface, resulting that increase of undesirable floating algae is to be prevented in the reservoir. Besides the system works to remove undesirable algae and oder from the discharge flow.
Explained and reported in this paper are on characteristics of the water purification system using filamentous algae and field experiments confirming the system to be effective for reservoir water purification.

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Unusual growth of undesirable algae caused by eutrophication has brought water quality problems of water bloom or odor in some reservoirs. Countermeasures against the phenomenon are to understand a growth mechanism of the algae and to prevent undesirable floating algae from rapid increase.
The water current control system proposed in this paper works in surface of reservoir to produce circulating layer which restricts supply of sun light and nutrition by maintaining the layer during flood and to prevent the undesirable algae from rapid increase.
Explained and reported in this paper are on the water current control system and field experiments to confirm the effect of dispersed aeration-circulation apparatus forming thick layers.

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A commercial or industrial large city often develops at the hinterland of a deep bay owing to its high defensibility against stormy sea. However, the exchange rate of sea-water between the inside and the outside of the bay is very low, so that the water is much polluted by industrial and domestic waste water in many cases. The Dokai Bay has also the same social problem. In order to solve the problem we propose an idea of improvement of water quality in this paper, which is that clean sea water of Hibiki open sea is introduced into Dokai Bay. Various conditions for water purifications have been attempted by using the diffusion simulations of COD. It has been clear that introduction of clean sea water (3m³/sec.) into the innerpart of Dokai Bay is very effective for purification.

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Two-dimensional experiments have been performed to clarify the interface movement and mixing phenomena in a two-layered stratified flow system exposed to wind stresses at the surface. The mixed-layer dynamics in the enclosed water body can be classified according to Wedderburn number, represented by the product of the aspect ratio and Richardson number. It is observed that the upwelling phenomena of density interface occur only in the range of Wedderburn number smaller than 4.0. In the case of an inclined bottom, the upwelling at the windward side becomes smaller compared with the flat bottom cases.

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Two-types of wind-induced density currents are analytically examined by using a turbulence model. Discussed here are two-dimensional two-layer stratification systems; they are (1) a completely closed system in which both ends are bounded by fixed walls such as lakes and reservoirs and (2) an open system with no fixed boundaries like oceans. Flow and mixing regimes are related to the dimensionless governing parameters which are scaled in terms of the wind shear friction velocity, the horizontal and vertical dimensions of the water body and the buoyancy anomaly of the thermocline interface.

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The effect of the wind speed on salt diffusion was studied by observations of the longitudinal distribution of Cl concentration in the surface layer of the Ishikari River, which shows highly stratified flow. The measurements were carried out during the dry season. Also, the time series of Cl concentration in the surface layer of two points in the river course are compared with each other and with the time series of wind speed at the points. This comparison appears to enable the prediction of surface salinity distribution.

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In this paper, some results of field observation concerning the anual and short-term behavior of salt intrusion in Lake Abasiri is reported. From the data analysis, we found that this lake has two layers of salt and fresh water vertically and that the lower layer of salt water is gradually ascending in this decade and it has no soluted oxygen. In the field observation in the river, we found that the salt water intruded into the lake in the form of salt wedge. Because of the occurence of record breaking heavy rainfall in this catchement area just before the observation, the thickness of the upper layer became from about 5 to 7 meter.
In order to make clear the mechanism of long-term trends of the lake, we proposed the model of tank-model type. In the final section of this paper, we compared the numerical results with the field data and we found the good agreement.

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