Author(s): Yoshio Kajiyama; Hiroshi Oyamada; Makoto Yamazaki
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Abstract: The behavior of frazil slush accumulation was observed at a small reservoir of the Kami-Iwamatsu hydroelectric power station belonging to the Hokkaido Electric Power Co., Inc. Radiative cooling from the earth to the atmosphere on winter nights creates an extremely cold climate in the Tokachi region, and forms a large amount of frazil slush in the upper reaches of the Tokachi river. Ice jamming problems have occurred several times at the water intake section of the station. This paper reports on the relation between the observed frazil slush formation, under the solid ice cover of a small reservoir, and degree-days, as calculated using a mass curve method of summated effects of the daily minimum air temperatures during winter. The 12 years data, between 1967-1978, have been used. The results are summarized as follows: (1) A large amount of frazil slush was formed when the daily minimum air temperature was less than -15°C over an extended period of time. (2) The accumulation of frazil slush correlated closely with the gradient of the curve of degree-days, calculated using daily air temperatures. (3) The changes in degree days distribution are an indicator of long term weather pattern.
Year: 1988