Seiche, << saysh, >> is a long wave motion in a lake, a bay, or a similarly enclosed body of water. The usual cause of a seiche is a wind that blows over the surface of the water. Other causes include earthquakes and changes in atmospheric pressure.
Wind can start a seiche in a lake by piling up the water on one side of the lake—the left side, for example. If the wind suddenly dies down, this water will start to move toward the right side of the lake. Thus, the water level will begin to fall on the left side and—at the same time—begin to rise on the right side. As the water reaches its highest level on the right side, it will reverse direction, moving toward the left side. The water level will then fall on the right side and rise on the left.
The flow of water will reverse again and again. However, the friction of the water against the bottom of the lake will cause the flow to die down gradually and then to stop.
