Piezometric response in several hillslope hollows was compared for small and large storms at sites in coastal Alaska and Japan. During smaller storms with dry antecedent conditions there was evidence of a "wedge" of groundwater accumulating from the base of the slope. For wetter antecedent conditions and larger storms, piezometric response was less affected by slope position, possibly because of the contribution of preferential pathways in the soil to groundwater fluctuations. Piezometric response was more rapid and generally higher in more dissected hollows.

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Four water uptake models for calculating soil moisture movement in a soil-root system are described and compared. Two models by Gardner (1964) and Molz and Remson (1970) are mainly based on the hydraulic properties of unsaturated soil, the third model by Herkelrath et al. (1977) on the soil moisture, and the fourth model by Feddes et al. (1978) on the soil water matric potential. The models are incorporated into a finite difference numerical calculation of Richards' equation including the root water uptake term. It is shown that soil moisture profiles, which are calculated using each model, are in relatively good agreement with those in laboratory experiments which are carried out under the constant environmental conditions. Among the four models, the third model agrees best with the experimental results. It is also shown that the water uptake profile depends on not only the root density distribution but also the soil moisture profile in the root zone.

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The ovjective of the present study is to clarify the formation and deformation processes of hydrograph caused by the topografic configuration of basins and the various flood prevention works. Firstly we introduced the basic equation to express the behavior of flood wave in a river. We found that the equation has the same precision with the basic equations of unsteady open channel flow. Secondly we investigated the effects of Manning's coefficient and the degradate of river bed on the downstream defromation of hydrograph. Finally through numerical simulations, we evaluated the hydrological effects of the various flood preventions such as cut-off works of channels and dams.

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Precipitation Index, a formula to obtain estimates of precipitation on the ground as a function of infra-red radiation observations of a geostationary satellite was developed over the 111, 000km2 area of Chao Phraya river basin in Thailand. The satellite data used were 0.25° mesh basic histogram of GMS-IR observations and the rainfall data were the daily rainfall measured by the Royal Irrigation Department of Thailand. The various time and space scale correspondences between GMS-IR and precipitation were identified. For 10-day rainfall estimate over 2.5° mesh, a formula PI (mm)=12.1 FCND+3.3ND was derived where FC was a fractional coverage of clouds below 235K and ND is the number of days. The coefficient of determination was D=0.25. The estimates were found considerably smaller than that of GOES Precipitation Index (GPI) currently used at CAC/NOAA which was developed by Arkin (1979) based on GATE using GOES in 1974. They were also found smaller than those by Maruyama et al. (1986) and Eguchi (1988) obtained from GMS over Western Pacific. It was concluded that precipitation production over the land was prevailed by a different mechanism from that over the ocean, thus it was necessary to develop region by region estimation formulae for reliable global rainfall monitoring.

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