A 30m-height tower has been installed in a uniform low-storied residential area in Tokyo, Japan. Radiation, heat, water vapor and CO₂ fluxes were measured continuously for one year. In this study, the seasonal and diurnal variations of fluxes were discussed using the data which were ensemble-averaged over all clear days of one month. The contributions of garden trees, concrete materials, transportation, human lives, and human body to latent heat and CO₂ fluxes were also investigated. The main conclusions are as follows. (1) Latent heat flux observed in the daytime during summer was larger than the conventional value. Assuming that this is only due to evaporation from garden trees-their area portion is less than 30%, the latent heat flux per unit vegetation area should be twice as much as the value reported for the forest near the urban. Garden trees might have a high potential to evaporate vapor due to the oasis effect. Concrete materials are found to be one of the evaporation sources and the contribution is not negligible in winter. (2) CO₂ flux was positive throughout the year. The most dominant emissions of CO₂ are attributed to human lives and vehicles due to the consumption of fossil fuels. The magnitude of CO₂ flux in winter was larger than that during summer. This seasonal change is mainly due to the increase of fuel consumption in human lives during winter and the absorption of CO₂ by plant photosynthesis in summer.

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A long-term field measurement was performed to investigate turbulent transfer in a densely built-up urban surface layer. The turbulent transfer efficiencies of heat, vapor, and CO₂ were examined. In the morning the low-frequency eddies penetrating the entire atmospheric boundary layer transfer water vapor efficiently due to the entrainment of dry air from upper to the surface. M.O.S. theory predicts that relative transfer efficiencies are unity and have no dependency on stability. But ratios for vapor/heat and CO₂/heat observed show that the transfer efficiencies of vapor and CO₂ are smaller than heat. This tendency is more significant in unstable condition. In order to discuss this result, wavelet analysis for transfer efficiency of scalars was conducted. The thermal structure and organized structure transfer heat efficiently. Vapor and CO₂ are also transferred as well as heat by some structures. But they are not or adversely transferred by other structures. Followings are considered as this reason. (1) Heat is an active scalar and produces the thermal structures by itself. Hence, the heat is transferred most efficiently. Vapor and CO₂ are transferred passively and the efficiency is less than heat. (2) The absorption/source of vapor and CO₂ is inhomogeneous. As a result, the heterogeneity of vapor and CO₂ concentration distribution causes their transfer efficiency lower.

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Two-dimensional shallow water equations (SWEs) are often used to simulate the inundating process caused by dike breakage. However, the accuracy of the results simulated is greatly affected by complicated land covers, which maybe concealed when a coarse DEM is used. To correctly simulate the inundating situations in a local region with a complex topography or with rapidly varied hydraulic gradients, nesting models have to be applied. Conventional approaches to deal with this problem are: 1) using a fine mesh over the entire domain, which is computationally intensive and in some cases uncontrollable. 2) using a variably spaced mesh, which may result in cells with a large aspect ratio and refinement in areas where such detail is not necessary. 3) a recently developed local grid refinement method, which can eliminate those problems, but in this method only the boundary values at the shared interfaces are used in the simulation that may lead to the information of the coarse grid region is not fully participated in the simulation process of the nesting model at the refined local region. In this paper, therefore, a new nesting method of local grid refinement for the 2D SWEs, which can fully incorporate the coarse grid values into the simulation process of the refined grid domain, is presented so that the aforesaid problems can be overcome.
Due to the complicated conditions of land covers in the flooding region, and only Manning coefficient n in the 2D SWEs has a relevantly good correlation with this complexity, it is necessary to make efforts to seek out an approach to estimate its spatial distributions accurately in order to further improve the accuracy of the numerical modeling. With the availability of higher resolution satellite image data of IKONOS and the classification functions of ERDAS-IMAGINE software have made it possible to evaluate the effects of vegetations and buildings on the inundating simulation.
Results of the case study indicate: (1) the new method of local grid refinement is applicable. (2) the satellite image of IKONOS with a resolution of 1×1 m can be employed to extract the parameters of vegetations and buildings in each computational grid of DEM with a resolution of 250×250 m and then the spatial distributions of the Manning coefficient can be estimated with these parameters. (3) the effects of vegetations and buildings on the inundating simulation are remarkable. (4) pumping strategy is an active approach worthwhile applications in the aspects of tackling with flood intrusion although it is a result obtained in special conditions of Kofu basin, where the elevation of the basin is much lower than those of the Fuefuki and the Ara Rivers.

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It is required to sequestrate CO₂ for solving global warming problem. One of the measures proposed for CO₂ sequestration is large-scale afforestation in arid land. From this viewpoint, we set a demonstration/research area in Leonora, Western Australia (Abe et al., 1997; Matsumoto et al., 2000; Yamada et al., 1999). In the present study, the stable isotopes analyses (δD, δ¹⁸O) was conducted for roots and branches of natural tree species, and ground water and soil water in the specific arid area. It was estimated that the water source of Eucalyptus camaldulensis is ground water, and Acacia aneura and Hakea preissii, soil water. The time variation of the ratio through before to after a rainfall event was also measured for several tree species including those artificially planted under different conditions. It was found that the response of trees to the event has varieties depending on not only their species but also their environmental conditions. The present results show the possibilities of selection of tree species fitting for the actual water conditions and application of suitable water management technologies to a specific tree for the most efficient afforestation of arid areas.

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Deeply under the ground, especially in redevelopment area in mega cities like Tokyo, drainage pipe system with huge-diameter has been laid in recent years. The water flow containing air-mass or bubbles in a drainage pipe shows the different hydraulic characteristics than usual open channel flow, and the compressed air in horizontal pipes occasionally blows manhole covers off when heavy and concentrated rainfall occurs and massive water rushes into the drainage pipe system. In order to simulate such complicated hydraulic phenomena of the flow in drainage pipe, we proposed an unsteady numerical model which can express the effects of compressed air-mass over the free surface of the flow or compressed bubbles in closed channels to the water flow. The air-flow discharge outgoing through vertical pipes and air pressure was calculated. Comparing the simulated results with the hydraulic experiments conducted by the authors, we could confirm the validity of the present numerical model.

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Recently, the development of GIS (Geographic Information System) technology has made it possible to handle a vast amount of data associated with spatially distributed hydrological parameters with their attribute information. Also, it helps the development of distributed runoff models which can consider the temporal and spatial variation both of water quantity and quality.
The purpose of this paper is to develop the GIS based distributed runoff model to simulate accurately the temporal and spatial distributions of many hydrological characteristics considering both water quantity and quality.
In this paper, GIS based distributed runoff model is developed by including the followings: the snowfall and melting process, irrigation process for paddy field, and variation process of water temperature. The developed model was applied to calculate the temporal and spatial variation of the water quantity and quality for the Shonai River Basin and the Geumho River Basin. The model showed highly precise results because of the modification of the channel network and extraction of hydrological parameters using GIS, and including sub-models such as snowfall and melting with calibration of model parameters.

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Environmental isotopes database for natural water in Asian-Pacific region was utilized for following three purposes: (1) to determine “common” isotopic characteristics of natural water in Japan, (2) to construct the prediction equation for isotopic characteristics statistically by using meteorological and geographical parameters, (3) to clarify the main physical process for determining δ value of natural water.
For δ value of shallow groundwater and river water, the prediction equation could be constructed as functions of the latitude and the wind speed of sampling point by using correlation matrix and multiple regression analysis. The latitude, the influential explanatory variable, is an indicator of location, and seems to be a proxy for some physical parameter. Single regression analysis between δ value and geographical and meteorological parameters suggested that isotopic temperature effect was the most effective for determining δ value physically. The prediction equation for d value was constructed as a function of duration of sunshine. The GIS analysis suggested that its spatial change was similar to that of “the amount of precipitation brought in winter season”. In Japan, the d value of precipitation in winter is higher than in summer. Hence “the duration of sunshine” would include the property of precipitation brought.

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