Spatial distributions of the downward radiation and the snowmelt rates on a forest floor were calculated under the meteorological conditions in the snowmelt period using estimated three dimensional distributions of the foliage density at a sparse and a dense forest sites with and without leaves. Using the calculated spatial distributions, we evaluated the spatial representativeness of the daily downward radiation and that of the daily snowmelt rates measured at anywhere on the forest floors. The global solar radiation didn't represent the spatial average. The downward long-wave radiation represented the spatial average. The snowmelt rates showed good representativeness except in the leaved sparse forest. The calculated distributions also showed the following results. The spatial variations of the snowmelt rates were small in spite of the large spatial variations of the global radiation on the forest floors. The cause was the high albedo of snow surface and the reverse correlation of the spatial variation between the global radiation and the downward long-wave radiation on the forest floors. The standard deviations of the spatial distributions of the downward radiation and the snowmelt rates on the forest floors depended on that of the foliage density. Moreover the representativeness of the hourly downward long-wave radiation measured at anywhere on the forest floors were discussed under the more wide meteorological conditions. The hourly value represented the spatial average except on the leaved sparse forest floor. The value on the leaved sparse forest floor had the representativeness when the apparent air emissivity was over 0.7.

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With the increase of the completed dams in recent years, we have become getting enough data of sedimentation in reservoirs to analyze hydrological and hydraulic features of the sedimentation variously. Through the investigation of sedimentation in reservoirs for water power generation, the authors discuss the annual variations of sedimentation and the sedimentation rates, relating to various factors of drainage basins and reservoirs . There are several different types in sediment accumulation changes, which seem relating to backsand upstream of reservoirs. Thus we select the factors of drainage basins and reservoirs relating to the types, considering the analogy from delta and fan on the formation of backsand. Moreover we indicate the specific sediment accumulation have to be estimated according to the type. As the result of the analysis for the relating factors, it is indicated that consideration of the multivariables are required in this analysis. We discuss the results of the analyses using quantification of qualitative data.

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This study compares transpiration results using surface temperature method (ST method) and heat pulse velocity. ST method calculates transpiration using image data of surface temperature and energy budget data. Heat pulse velocity by heat pulse method correlates with transpiration of a tree. Surface temperature was low and estimated transpiration using ST method was high at trees where heat pulse velocity is high. The variations of difference of transpiration by ST method are found to be similar to those of heat pulse velocity at Sugi and Hinoki forests. Mapping of transpiration using ST method at forests are ascertained by such results.

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A preliminary observation for the GEWEX Asian Monsoon Experiment (GAME) was carried out at one of the observation sites of GAME near Sukhothai, Thailand in the summer of 1996, in order to assess the performance of prototype stations for measuring surface fluxes and soil moisture as well as to evaluate relative merits of the methods of determining fluxes. The data sets from three observation systems yielded turbulence statistics and the surface flux values by applying the eddy correlation method, the bandpass covariance method, the Bowen ratio method, the profile method and the bulk method. Intercomparisons of the resulting values indicate that the turbulence statistics are of high quality but the algorithm for evaluating bandpass covariance needs further improvement. It was also found that an accurate evaluation of energy storage in water body is essential in the application of energy balance approaches at paddy field. Overall, all stations performed satisfactory during the experiment in a hot, humid environment. However, a better protection against a strong rainfall appears to be needed for long term observations in this area.

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The field experiments were conducted by using two columns in order to estimate the effects of tillage on the temperature and water in an unsaturated soil zone. The effects were shown by being compared with values obtained in the no-till column. The results were as follows: an increase in soil temperature in tilled zone; an increase of pressure head below the tilled zone; a reduction of cumulative evaporation by tillage; and increased air temperature near the soil surface.

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