The handling of some soil hydraulic properties applying the nonuniformity of soil structure was considered to analyze the infiltration and drainage on the artificial depression areas in the urban park. On the sample in which soil texture and its particle density are equal, soil water retentivities and other properties in saturated ranges received clearly the effect of the bulk density distribution. Then we experimented the soil water retentivities and conductivities on the several bulk densities from the same soil origin, in this case, these rearrangements resulted in comprehensive estimation about both properties is available in unsaturated range (Ψ_e>Ψ).
However, some considerable problems were left, when the critical point Ψ_cr (almost equal to air entry potentialΨ_e, nec essary for estimating soil hydrological characteristics on the basis of those relations, was decided.

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A numerical model which can compute air temperature, specific humidity and wind velocity distribution within a single district of few square kilometers was developed by adding the effect of urban building and the forest canopies to a mesoscale turbulent closure model. The effects of anthropogenic heat are also accounted for in the model. The new model was tested with different kinds of canopies. Results of computations indicated that temperatures of the ground surface and walls of buildings depend much on the building density. The validation of the model, conducted using observational data, indicates that the model is capable of computing the wind velocity and air temperature in the urban area with resonable accuracy. The comparison of the results of the new model with existing models on the urban climate indicates that the new model can produces more realistic results.

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In this study the stormwater runoff analysis was carried out for three urban basins of hills, upland and lowland. The fi-nal infiltration capacities were measured under the similar condition of actual rainfall using a rainfall simulator in a field for each type of land use. A stormwater runoff model was developed combining a effective rainfall model taking account of the infiltration characteristic of each land use and a rainfall runoff model using physical equations. The results indicat-ed the ability of infiltration capacities measured by a rainfall simulator as a criterion and the model applicability for the stormwater runoff analysis of urban basin.

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The field observations were performed in Ginza office area in summer 1996, to investigate the characteristics of heat balance in complicated urban canopies. The sensible heat was measured by two methods, one was “eddy correlation method” and another was “scintillation method”. The following results were obtained; 1) The observed latent heat flux was very large and comparable to the sensible heat flux. This was proved to be caused by cooling systems introduced to office buildings. 2) The artificial and latent heat on a holiday were less than those on a weekday. 3) The sensible heat observed by scintillation technique agreed well with that by the eddy correlation method. And also, the longer measure ment path of scintillation meter (130m in this case) compared to that of sonic anemometer (only 15cm) could make the fluctuations smaller. 4) The displacement height (d) was found to be very sensitive to the results of scintillation methods and the way how to determine it was discussed.

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Brutsaert (1979, 1982) suggested a method for the complementary model taking atmospheric stability into account on the basis of the Monin-Obukhov similarity theory. Katul and Parlange (1992a, 1992b) and the authors (1993) independently published the papers on the estimation of latent and sensible heat fluxes including the effects of the atmospheric stability. Parlange and Katul (1992c) actually estimated the latent heat flux using the complementary model suggested by Brutsaert. This paper describes a regional complementary model utilizing the remotely sensed data to estimate the actual evapotranspiration in broad areas. The proposed method is summarized as follows.First, the new method estimated the regional air temperature in the atmospheric surface boundary layer using meteoro logical routine data and surface temperatures derived from the Landsat TM data. Secondly, the authors applied the esti mated air temperatures on the evaluation of the regionally distributed drying power of the air in the Penman potential evaporation composing the complementary relationship. The authors' method enables the complementary model to esti mate the distribution of the actual evapotranspiration in regional areas. The values of the latent heat flux obtained by the proposed method have almost coincided with those by the other method already reported by the authors (1994, 1996).

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This paper describes (1) how the normalized difference vegetation index (NDVI) evaluation changes and (2) how the NDVI-based evapotranspiration estimation changes, as the spatial resolution of remote sensing images becomes coarser. This analysis uses a degradation algorithm based on the MTF. With the airborne MSS images of 6.25-m resolution, images simulated have resolutions of 16, 30, 50, 80, and 250m, which are corresponding to the resolution of ADEOS/AVNIR, Landsat/TM, MOS-1/MESSR, Landsat/MSS, and ADEOS-II/GLI, respectively. The study area is the Seto-Nagakute area (3×6km) consisting of urbanized areas, forest and cultivated areas. From the pixel-based analysis the authors have found that the mean of NDVI does not change remarkably as the spatial resolution becomes coarser. Meanwhile, the means of estimated evapotranspirations for the 6.25- and 250-m images are about 48 and about 47mm/month respectively. The standard deviation of estimated evapotranspirations gradually becomes smaller as the spatial resolution becomes coarser. Consequently, the NDVI and the estimated evapotranspiration averaged over the area concerned do not depend much on the spatial resolution of the remotely sensed image. The authors also assess the effect of urbanization on monthly evapotranspiration, using a diagram based on the forest, cultivated and urbanized land classes.

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The variation in N03--N concentration and the natural abundance of 15N (δ15N value) in streamwater was measured during a rainfall event. NO3--N concentration was positively correlated with discharge rate, but δ15N value was negatively correrated. The initial increase of N03--N concentration in streamwater was accompanied by a linear decrease of δ15N value from 0.2‰ to -1.4‰. Discharge of soil solution from surface soil layer explained this variation. When the NO3--N concentration decreased, δ15N value increased exponentially from -1.2‰ to 6.0‰. This variation could not be explained by the mixing of soil solutions, but it agreed with the classical equation of Rayleigh used to calculate the change in δ15N value during denitrification. We concluded that the decrease in NO3--N concentration in streamwater was caused by denitrification in the saturated soil layer during a rainfall event.

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