A long-term monitoring waterproof camera was set up in the bottom of Lake Nakaumi at a depth of 6.5m, over 2.5 weeks of Nov. 9- Nov.26, 2004. There were several times to record a wind speed of over 10m/s. However, no bottom water turbulence occurred in such a wind speed within a one hour wind blowing. Winnowing of bottom sediments occurred in the condition of the wind speeds > 10m/s and >5..6 hours blowing, in November 12 and 26. The bottom water turbulence was not only controlled by the wind speed, but also a period of duration. The quality of water is also influenced by a wind stress. A mixing of upper and middle waters occurred after 6..8 hours on both days. Bottom water, however, was very stable without the mixing of upper water.
The water dynamics and lake floor condition that responded to a wind stress were compared with those of 2006. The response of the water and bottom sediment to wind stress was not always the same; there were different responses of the upper and middle waters and different water clarity. A subtle change of lake environments makes it difficult to reconfirm the influence of wind stress.