Kamitani basin, located in the source area of Yura River, central Japan, is a snowfall region under temperate humid climate. The basin (4.9km2) is covered by natural forests of Cryptomeria japonica. Fagus crenata and Quercus mongolica var, grosseserrata. The observation duration of meteorological and hydrological data used in this study was from June 1993 to December 1994. During the observation period, the summer season climate between the two years had rather different, namely, rainy with cold in 1993, and rainless with hot in 1994. An application of a simple SVAT model based on heat balance was carried out. Three formulas based on the Jarvis (1976) model were adopted to estimate the value of surface resistance, which is one of the required parameters in the SVAT model. A runoff model was combined into the SVAT model to determine the water budget of the basin. An optimal value of minimum surface resistance could be derived after considering the water balance of the basin. From the results, the agreement of hydrograph between the calculated and observed was derived. It is clear that the value of minimum surface resistance is a changeable value with the change of climate condition even in the same basin. This phenomenon is possible to be explained using a conception of radiative dryness index. That is to say, the value of minimum surface resistance is a function of the mean soil moisture condition of a basin

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Subalpine regions have a long snowmelt season that begins in late spring and lasts until early summer because of the great amount of snow. The energy for snowmelt in the early summer may become dominated by the sensible and latent heat fluxes. Therefore, to evaluate the spatial distribution of snowmelt in subalpine regions, it is necessary to estimate the distribution of wind speeds that dominates those fluxes. In this study, a simple model that calculates the distribution of wind speed over the surface of mountain regions was developed and its ability to estimate the distribution was examined. In this model, the atmos-phere is divided into 4 layers: 1) the highest layer that is not affected by any surface conditions, 2) a layer that consists of po-tential flow, 3) a layer in which the roughness length consisting primarily of the topographical undulation dominates the vertical wind profile, and 4) the lowest layer, whose vertical wind profile is formed by the surface roughness length. The merit of this model is that the distribution can be estimated using only data on topography, surface roughness, and wind speed and wind di-rection in the top layer. This model provides good estimates of wind distribution on the surface of mountains as demonstrated by field observations. A relatively good estimation is produced for points located in the middle of mountain regions.

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This paper describes the process and characteristics of the great floods occurred in the Changjiang River, the Nenjiang River and the Songhua River during 1998. The flood of the Changjiang River is compared with that of 1954, and the reason of higher water level under same discharge is analyzed in detail. Some considerations on countermeasures are discussed. A lot of data calculated in this paper are very useful for scientific research and practice on flood control.

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The effect of temporal variation in rainfall intensity on flood concentration time, which is the flood propagation time when the discharge at the downstream end reaches a peak, was discussed using kinematic runoff model. This effect was theoretically shown to be expressed using the ratio of runoff depth (qB) to mean effective rainfall ( ). R=qB/ during the flood concentra-tion time, and R was shown to be only affected by temporal variation in rainfall. Moreover, the temporal variation in R was ex-amined by numerical experiments using the rainfall data observed in 80 heavy storms. The result shows that the flood propaga-tion time does not become minimum simultaneously with the peak discharge but a little after the peak, and that temporal pat-terns of rainfall vary flood concentration time from 0.7 to 1.5 times as long as the time estimated by the flood concentration time formula.

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Micro-meteorological observations and measurements of heat and moisture transfer in sandy soil were carried out to obtain basic data for conserving irrigation water in the United Arab Emirates (U.A.E.) from 1996 to 1998. This paper shows monthly averaged diurnal changes of air temperature and relative humidity, wind velocity, downward long-wave radiation, downward short-wave radiation and soil temperature. In addition, the drying of the soil surface layer was monitored during three water-ing-evaporation trials. Time variations and vertical profiles of the soil temperature, soil pore relative humidity and water vapor density were obtained by a “soil thermo-hygrometer” method and the volumetric water content was determined by a “heat probe” method. The depth of drying estimated by the two methods agreed closely and it is concluded that the “soil thermo-hy-grometer” method is a valid means for monitoring post-irrigation drying phenomena.

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