|Budget Amount *help
¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1991 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1990 : ¥1,100,000 (Direct Cost : ¥1,100,000)
1.Water Temperature of Nagase Dam Lake
Water Temperatures vary subjected to the depth from spring to fall, but in the winter, water temperature of the Dam Lake is constant at any depth.
On the floating gate in the Dam, temperatures at 0,1,2,2.5,3,3.5,5,10, ・・・・40 m at 5 m interval were investigated as well as surface air temperature, humidity and wind direction and speed.
From August 31 to September 5,1990, surface water temperature goes up according to the rise of air temperature during the daytime, and goes down during the night. At 1 m depth, amplitude of water temperature variation is larger than that of surface. Daily variation is smaller at deeper places than 5 m.
From October 17 to 26, daily variation becomes smaller and substantial temperature drop was observed at less than 2m's depth. From February 15 to 18, a remarkable rise of temperature which was thought to be an influence of flood was observed. Therise of the water temperature starts March, 7 for 5 m depth, March, 13 for 15 m depth, March 23, for 25 m depth, April 2 for 40 m depth.
Bowen ratio method was applied to calculate lake evaporation. The monthly mean of sensible heat transferring coefficient was 0.078, latent heat transferring coefficient was 0.117, evaporation was 3.7 mm/day for March, 1990. Those of April were 0.068,0.102,4.2 mm/day respectively.
3.Observation of convection cells by infrared thermography
Surface temperatures of the Nagase Dam Lake were photographed by thermo-tracer (NEC-Sanei) during November 1 and 2,12 and 13 from 19 p.m.to 9 a.m. Wave length of the temperature was between15 and 45 cm, average length was 30 cm, amplitude was between 0.4 and 1.4ﾟC,average was 1.0ﾟC.