Seasonal Variation of the Temperature of Water of the Rivers in Japan

Abstract

The seasonal variation of the water temperature of 12 rivers in this country observed in 1931 and 1932 was examined. From the difference between the temperatures of water-and air the following three river-types are recognized.
A. Lower type: The period in which the water-temperature is lower than the mean air temperature is limited only for 1 or 2 months of the summer and moreover the difference of both temperatures is below 2°C. (R. Kawadana at Nagasaki, R. Asahigawa at Okayama, R. Arakawa at Kumagaya and R. Kitakami at Isinomaki) B. Middle type: The period above mentioned is for 5 or 8 months of the warmer seasons and the difference is above 4°C. The minimum water-temperature occured in February. (R. Arakawa at Titibu, R. Kinugawa at Utunomiya, R. Tikumagawa and R. Saikawa at Nagano and R. Mogamigawa at Yamagata.) C. Upper type: The period is further widened to the almost all months of the year and the high period of water-temperature is only for 1 or 3 months of the winter. The difference of both temperatures is greater than that of the middle-type. (R. Hirosegawa at Maibasi and R. Susohanagawa at Nagano.)