Considering the water balance of an atmospheric column, annual vapor flux convergence is nearly equal to the precipitation minus evapotranspiration. Connecting this information with the conventional basin water balance can estimate the annual runoff, evapotranspiration and the change of basin water storage. Such a method to evaluate the water balance is called as the atmospheric water balance method and used for the analysis in global scale. The global distribution of vapor flux convergence is estimated using the objective analysis data of 4 dimensional data assimilation by ECMWF (European Centre for Medium-Range Weather Forecasts). The accuracy of the vapor flux convergence is compared with the climatic mean runoff by defining the geographic information on the boundaries of large river basins. Global distribution of precipitation and river runoff are overlaid in 2.5° degree mesh of the globe, and the global distributions of evapotranspiration and the basin water storage are estimated. The fresh water transportations between oceans and the role of rivers in the south to north transportation of water in the globe are evaluated by defining the position of discharge from continents to the ocean. The atmospheric water balance method is one of the powerful tool to estimate the global water balance and water cycle, and it is expected to be used for the monitoring of their variabilities.

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We examined the possibility of improvement in a porous asphalt pavement for runoff control by the installation of a infiltration pipe under the pavement. From the result of many infiltration experiments at our experimental rainfall infiltration facilities, it made clear that the infiltration rate through the porous asphalt pavement is influenced by the volume of pore and permeability of the pavement and if storm water puddled on the surface of the pavement then rainfall infiltration becomes fast. And the construction of the infiltration pipe under the porous asphalt pavement will improve the final infiltration rate of the infiltration pavement about 5mm/hr. Furthermore, we build up a model which can simulate rainfall infiltration and runoff at the infiltration pavement with the infiltration pipe based on infiltration process in the pavement and infiltration pipe. By this model, we prove that the construction of the infiltration pavements with infiltration pipes is one of effective storm runoff control facilities in urban area.

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We must consider an influence of pollutants from non-point sources on water quality of a river for environmental control of a river basin. Especially, in urban area, storm runoff water is much polluted by non-point pollutants. But, until now most simulation models which are developed for environmental control of river basin for predicting water quality of the river have not considered pollutants from non-point source. Therefore, we developed “The Water Quality Control System of River Basin” which has the simulation model considering non-point pollutants flushed out with storm runoff. This system can evaluate the environmental effects of construction of a sewerage system and installation of household wastewater treatment tanks on all houses in the basin. And this system can display longitudinal change and daily change of water quality at any point of the river.

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In order to quantify direct interactions between solid particles and turbulence in solid and liquid two-phase flows, we investigate an interaction between turbulence generated by uniformly falling particles and the ocsillating grid turbulence. A hydraulic experiment shows that modulation of turbulence intensities of fluid phase which have been pointed out in the preceding studies occurs even in the oscillating grid turbulence and that the modulation of turbulence intensities is anisotropic. A simple model which is proposed to interpret the direct interaction reproduces tendency of the experimental results well.

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Numerical method of the solution of water quality equation for rivers is proposed on the basis of the method of characteristics. The movement of water in non-tidal or tidal rivers is simulated by solving the continuity equation and momentum equation for unsteady flows by the implicit finite difference method. Then, water quality changes are simulated along the trace of the movement of water by solving the water quality equation. The results of simulation of water quality are presented to understand the pollution process in tidal rivers.

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A one dimensional model to predict the long term stability of channel bed elevation and grain size profile is proposed. The model is tested using the geometric conditions of the Ishikari River. By a series of calculations using different discharge profiles, it is shown that the two different characteristics of grain size distribution, with and without an abrupt change in the longitudinal direction, can be formed simply by changing the discharge scale. It is also shown that the formation of the bed elevation profile as well as the grain size profile can be calculated using time series of actual discharges over a wide range of magnitude.

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At the inception of channeization, gullies are seen to be formed at the downstream end of plateaux. Those gullies migrate upstream to become channels and develop into complex systems of channel network. In this paper, a mathmatical model of gully formation is presented. Velocity and surface profiles of sheet flow over the plateau with the perturbed downstream end are calculated by solving St. Venant shallow water equations with the use of singular perturbation techniques. The calculated results show the tendency of flow concentration into indentations at the downstream end as expected. Applying the “threshold concept” to the results, characteristic wavelength of the order of (depth/plateau slope) is obtained, which is of the same order as that obtained from the “upstream-driven theory”.

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The validity has been investigated of the standard k-ε model for oscillating-grid turbulence, whose stationary field is in balance between the diffusion of the turbulent energy and the dissipation rate of the energy. The nonlinear k-ε equations give the exact solutions for the turbulent energy, the dissipation rate of the energy, the vertical flux of the energy, the eddy viscosity and a characteristic length scale. The experimental data satisfy very well the relations expected theoretically between the turbulence quantities. It shows the standard k-ε model to be applicable to the diffusion-dissipation balanced turbulence. The exact solutions include three model parameters. Their values based on the experimental data show that the model constants accepted widely in the k-ε model are valid, and that the ratio of the pressure-velocity correlation to the triple correlation between fluctuating velocities takes -0.49. The exact solutions can describe the turbulent properties much better than the empirical relationships adopted by many researchers.

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Sediment transport in sheet-flow mode is simulated by DEM (distinct element method) with special reference to the momentum transfer due to the interparticle collision. The mean-velocity profile and the root-mean-square value of the velocity variation of sediment particles are calculated through a statistical operation of the simulated motion of sediment particles. The important role of interparticle collision in the momentum transfer in sheet flow is clarified by observing the typical snapshot of the motion of particles and the trajectories of particles. Furthermore, the sediment transport rate in oscillatory flow is predicted by using the result of the simulation; and the formula of the sediment transport rate is proposed as the approximation of the results of the simulation.

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Characteristics of waves and currents in the coastal area are investigated through the analysis of field data obtained at the depth of 15m of Niigata and Ishikawa coasts. Strong currents in the alongshore direction as well as rise in the mean water level were generated after the passage of a low pressure system accompanied by strong wind. It was found that the current velocity had close correlation with atmospheric pressure, mean water level and wind velocity with time lags of 3 to 20 hours behind. Numerical simulation based on depth-integrated momentum equations revealed that wind stress and Coriolis' force were major driving forces which induced and maintained coastal currents.

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Riprap scour protection has been commonly used for piers. But the method of the design is rather empirical. In order to establish the practical and reasonable methods of design, the mechanism of the seepage flow in the scour protection should be carefully examined. The seepage flow is measured both in a hydraulic model test and in a field measurement at Akashi Strait Bridge. A design method of grain size of the inner and surface layer rubble mounds, thickness of rubble mound layer and construction area is proposed.

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Water particle velocities and suspended sand concentration near the bed were measured just outside the breaker zone of the Ajigaura coast facing the Pacific Ocean. Data were obtained for 1 hour under the condition that wind waves were superimposed on swell. It was found that the low-pass-filtered concentration had strong correlation with the energy level of the incident wave. The transport of sand by the long wave component was in the offshore direction. The bottom shear stress and the pore-water pressure were estimated taking the wave atiltness into account. The sand concentrations in half wave periods had correlation with the bottom shear stress of the previous wave but less correlation with the pore-water pressure variation. The long wave component in the sand concentration was found to be simulated by a numerical model based on one dimensional diffusion equation.

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The production of biodegradable plastics, polyhydroxyalkanoates (PHA) from volatile fatty acids (VFA) by aerobic or anaerobic/aerobic activated sludge was investigated. The anaerobic/aerobic activated sludge produced co-polyesters composed of 2-4 monomer units from VFA (C2-C5), and that the contents in dried sludge were as high as 7.8-18.2wt%. The anaerobic/aerobic activated sludge produced co-polyester composed of [R]-3-hydroxybuyrate (3HB), [R]-3-hydroxyvalerate (3HV), [R] -3-hydroxynonanoate(3HN), and [R]-3-hydroxydecanoate (3HD) with high yield of 40wt% from acetic acid as the sole carbon source in nitrogen-free wastewater for 6-12h. It was suggested that PHA production from wastewater treatment was possible by using the anaerobic/aerobic activated sludge.

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Denitrification rate (K_DN) of suspended activated sludge in the high rate nitrogen removal process using immobilized nitrifiers was investigated in relation to BOD-SS loading and temperature. A demonstration plant and two pilot plants were operated with BOD-SS loading from 0.83 to 14.5mg-BOD₅/g-SS/h and temperature from 12 to 27°C. K_DN (mg-N/g-SS/h) was almost proportional to the amount of accumulated organic matter (A) multiplied by its metabolism rate constant (κ). K_DN changed little with the seasonal change of temperature, as the A value increased with the decreasing temperature, though decreased the κ value. It was found the proportional increase of the A value to BOD-SS loading resulted in the proportional increase of K_DN.

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The concept of the ecological economy system is proposed taking the price of paper as an example. The ecological cost is defined as such cost as decided when we produce, consume and dispose any goods without deteriorating ecosystems. The ecological price of paper is determined on ecological goals by the estimation of raw wood price, energy cost, pollution prevention cost, the expense for the industrial waste disposal and paper refuse disposal, that is about 2.6 times the present price of paper. Determinations of the ecological price have disclosed the recycled paper is preferred to the vergin paper under the ecological economy system.

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In this study, the start-up of UASB reactor and analyses of granular bacterial structures were discussed by using high concentration soy wastewater from fish food process at 35°C. The granular sludges cultivated by synthetic substrate containing mainly glucose were used as inoculun material. When the start-up was finished, 60-70% TOC removal efficiency, and 30-50% lipid removal efficiency were obtained under the TOC loading rate of 10-12kg.m.^-3. d^-1. When the treated water was not recycled under the operational conditions, the bacteria distribution of the granules was vertically different. Almost all of the granules in the upper part of sludge bed consisted of Methanothrix-like bacteria while the granules in the lower part presented multi-layer bacterial structures. The exterior layers of the granules predominantly consisted of bacterial cocci and short rods. The interior layers consisted of a considerable number of Methanothrix-like bacteria.

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Relationship between oxygen transfer coefficients and turbulence parameters near air-water interface is examined using oxygen transfer coefficients measured in open channels by many researchers. Turbulence parameters are estimated from common hydraulic parameters such as depth and friction velocity.
The examination is made mainly with measurements in laboratory channels. Some problems in applying energy dissipation model to open channels and usefulness of 1.25 power turbulence intensity model are shown. It is indicated that oxygen transfer coefficients measured in open channels including natural streams fall into three groups. Comparing with measurements in stirred vessels, an equation based on a turbulence intensity model for estimating reaeration coefficients of rivers is presented.

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The purpose of this paper is to report a computational method for finding optimal controls of multi-reservoir operations, based on the method of K. Ohno's new approch to DDP with Newton's Method. We added a line search technique to it for the stability of numerical computation and combined the method with modified Bell-Jacobson's ε-Algorithm to cope with singular control. We refer to it as SDN-DDP.
The simulation study shows that the method can accurately solve optimal control problems of multi-reservoir and water demand systems under a strictly convex cost function, with some computational quantities

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Water surface oscillation was found in a typical pool and weir fishway installed on a diversion weir in the Kinokawa River, Wakayama Prefecture. It was clarified through field observations that the transverse waves consisted of one-meter-high seiches with beats across the fishway. Non-overflowing baffles, installed in the center sections of weirs in the fishway, effectively to reduced the transverse waves, providing good resting areas for migrating fishes.

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We investigated application of a non-equilibrium suspended sediment model into analyses of the river bed variation in the upper reach of the Tenryu-gawa river having a flood plain immediately up a contractive section of the river channel. On the assumption that the river flooded on a large scale, the sectional mean velocity was determined according to flow profiles obtained by non-uniform flow calculation based on a measured discharge. In areas where the river channel was supposed to have the single cross section, one-dimensional river bed variation analysis was conducted without regarding non-equibrium characteristics. The flood plain, on the other hand, was divided into two areas, that is, the main channel and the flooding area, and one-dimensional analysis was implemented by applying the known non-equilibrium suspended sediment equation for each area. The analyses showed that the longitudinal variation of the river bed and the flood plain after the flood could be estimated at a relatively high accuracy by appropriately setting the grain size, variation of the discharge from the equilibrium condition to the non-equilibrium condition, and treating of the suspended and bed load.

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Turbulent structure over strip roughness in open channel flow with various roughness spacing is simulated with a modified low Reynolds number k-ε turbulence model. The effect of the free surface is taken into account in the process of the calculation. The turbulence characteristics in response to the roughness spacing is predicted. Comparisons with the experimental data are generally adequate, in which the predictions for velocities are better than those for turbulent shear stresses and resistance coefficient. The values of the turbulent kinetic energy increase apparently in neighbor of the upstream corner of the roughness. The mixing effects of the flow become strong with the decrease of the roughness spacing.

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The United States has been confronted with an array of environmental problems in recent times. New types of pollutants are permeating groundwater aquifers and the stratosphere threatening air and water quality, the global climate, and the quality of life. Bioprocesses, specifically anaerobic digestion, can play an important role in stabilizing organic wastes, in detoxifying hazardous wastes, in modulating the greenhouse effect of pollutants, and in recovering renewable energy from the pollutant carbon. This paper examines the probable role that anaerobic digestion, in particular, two-phase anaerobic digestion, can play to alleviate current environmental problems in the United States.

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A laboratory study was used to develop a simplified kinetic model, to evaluate the kinetic parameters, and to provide rational design parameters for a pilot plant treating flax retting wastewater by means of the simulation of optimal operation of the UASB reactor. The results indicated that the developed model can be used predicatively for assessing plant performance and when the concentration of the influent is at the range of 5.5-7.3gCOD/l, the concentration of the hard-biodegradable materials is 0.46gCOD/l.

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