Area of remaining snow is observed by NOAA-AVHRR during snowmelt season from 1988 to 1990 in the Tadami River catchment. The hydrological data are also utilized at the dam site of Taki. It is confirmed that a set of NOAA-AVHRR data is useful to evaluate the remaining snow area. The relationship between the change of remaining snow area and the snowmelt runoff is discussed.

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As in the past, water temperature in rivers that showed difference between water and atmospheric temperatures is used in the snow-melting ditches for snow management.Recently, for the purpose of providing air and hot-conditioning system and hot water supply system, the use of water temperature in rivers has been given much attention. To utilize water temperature, understanding its fluctuation is necessary. As such, water temperatures at six points in the Uono River are measured by recorders, their fluctuations are investigated, and water and atmospheric temperature relationships are studied.
The water temperature fluctuation repeats every one year period and every one day period. However, both periodic phases in water temperature fluctuation start a little later than that of the atmospheric temperature. Likewise, both amplitudes are less than that of the latter. Regression analyses between the daily mean water and atmospheric temperature fluctuations are examined. Principally, atmospheric temperature influences water temperature. Thus, for the daily mean water and atmospheric temperatures, a high correlation is obtained. However, residuals due to snowfall, melting snow and yearly phase differences between water and atmospheric temperatures are observed. As such, multiple regression analyses are conducted where three predictor variables are used, namely, the daily mean atmospheric temperature, the moving mean atmospheric temperature and the depth of snowfall during the preceding day. Results showed a higher correlation than that obtained from simple regression analyses. Hence, it is possible to predict the daily mean water temperature by using these multiple regression equations.

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[in Japanese]

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