Seiche observations were conducted on 20th April, 1996 at 6 sites (site AーF) on shore of Lake Koyama, Tottori Prefecture. This brackish lake has 7.0km area and 14.4km shore line length. Strong wind (more than 10m/s in 10min. average) blew just two days before the observational day. Water level fluctuations illustrate anti-phase between observational sits A & B on northern shore and D & E on southern shore, which means typical Seiches. Water level fluctuations occurred at c.a. 17 min. intervals, which can be estimated by T=2 L/√(gh) Where T : wave period(s), L : diameter of a lake(m), g : acceleration due to gravity(9.8m/s^2) and h : mean water depth of a lake(m). Fluctuation range varied from 4cm to 10cm from site to site
