An application of TDR (time domain reflectometry) method for measuring stem water storage is discussed in the present study. A laboratory experiments by using of stem samples of a Japanese red pine (Pinus densiflora Sieb. et Zucc.) and an oak (Quercus mongolica Fish) were carried out in order to determine the regression curve between the volumetric water content of the stem sample (θ) and the apparent dielectric permittivity (Ka). The results of the laboratory experiments showed that TDR method was the excellent one to measure θ if a relationship between θ and Ka for each tree species was obtained in advance.
A field observation was conducted on a test stand of Japanese red pine. The stem water storage and the amount of sap flow were measured by using the TDR method and the heat pulse method, respectively. The variations of the amount of stem water storage estimated by the TDR method were in good agreement with the water absorption deficit evaluated by the difference of the amount of transpiration from the test sand and that of water absorption from the root zone based on the heat pulse method. These results lead to the conclusion that the TDR method is the excellent one to measure the stem water storage.
Evaluations of the water budget were made for the test stand. It became clear that the contribution of the stem water storage to transpiration accounted for about 10 to 20% of the daily transpiration.

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A synthesized physically-based system for flood forecasting by a PC is proposed. The combination of the newly-developed model for runoff in mountainous basins and numerical calculation of one-dimensional unsteady flow in river channels has made possible a totally-physical-based analysis for runoff in large basins like the Tone River, of which catchment area is the largest in Japan. Runoff in a mountainous basin can be uniquely determined by a parameter composed of the following seven quantities, such as slope gradient, slope length, the thickness of surface soil layer, unsaturated hydraulic conductivity, effective porosity and two fixed number for field moisture capacity. A shape of simulated hydrograph is roughly determined by both a spatial distribution of sub (tributary) basins and a timing of a peak discharge from the tributary basins. With changing roughness coefficient of riverbed artificially, water table in the down stream varies more sensitively than discharge.

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Stream flow and stream water chemistry were monitored in four hilly headwater basins, where a fault divides the region into gravel area, and weathered granite area to evaluate the relationship between rainfall-runoff process and geology of the basin. Also, spatial distribution of specific discharge of streams and springs was observed in the surrounding area of the monitored basins, and tensiomentric observation was performed in gravel and weathered granite basins. The specific discharge of streams and springs was higher in gravel region than that in weathered granite region in high-flow season. The quick flow ratio. (defined by Hewlett and Hibbert, 1967) to the rainfall was higher in the gravel basins than that in the weathered granite basins, whereas the base flow rate during low-flow season was higher in the weathered granite basins than that in the gravel basins. The concentration of sodium, calcium, bicarbonate and silica in the stream water was higher in the weathered granite basins than that in gravel basins. Tensiometric and groundwater data shows that percolation rate in the unsaturated zone would be higher in the gravel basins than that in the weathered granite basins. The difference of percolation process in the gravel and weathered granite basins would result in the difference of runoff and stream water characteristics and the subsurface water movement between the gravel basins and the weathered basins.

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Using the Airborne Multi-spectrum Scanner in 1998, snow and vegetation indices, with which (1) drop of the radiance between visible and near infrared over snow cover and (2) immediately increase on a shorter near infrared wavelength over vegetation covers (forest etc.) were considered, were evaluated.
Compared with the two wavelength band indices (same as NDVI etc.), the index which reflected the effect of (1) and (2) was sensitive to the vegetation density (Plant Area Index; PAI) under the coexistence of both vegetation and snow, and could recognize the state of the vegetation cover independent on the snow cover on the floor.
Moreover, it was confirmed that the reflectivity spectrum in the shorter wavelength than 0.9μ m could catch the steep rise made by vegetation properties around the value of 0.7μ m.
In addition, the snow cover and the forest region were classified by using S3, with which PAI under coexistence of both vegetation and snow can be estimated, and how the reflectivity spectrum of several channels changed according to the observation angle was estimated. Fore scattering was strong over the snow cover and Lambert-like scattering was found in the forest region. Bi-directional reflectance distribution function (BRDF) characteristic appears strongly, though the variation of viewing angle is small (±35degrees). However, BRDF of each wavelength is similar, and its influence on the index is small.

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