Loch Earn

Lochearnhead sits at the western end of Loch Earn with St. Fillans at the eastern end. Loch Earn is a great venue for watersports and other leisure activities and is unusual in having its own 'tidal system'. In fact these are not true tides but is seiching. (A true tide is driven by the sun and moon). As a result of the persistent prevailing wind blowing along the Loch there is stress applied to the water surface. This causes a slight slope on the Loch! As with all damped mechanical systems, applied pressure can result in an oscillation called a seiche. In the case of Loch Earn this has a period of 16 hours. The water moves back and forth along the Loch - not in a raging torrent, of course - but the effect can be observed and measured. The currents can result in complex turbulence as an upper warmer layer of water mixes with the lower cooler water near the Loch bottom.

Other fresh water bodies which experience this effect ( seiches ) are Lake Geneva, Lake Garda, Lake Erie and Lake Baikal.