Fall Turnover?

[Matt Geiman]

Can anyone help me understand the Fall turnover? How can you indentify when it happens? Does it only happen in large lakes? Does the Tidal Potomac experience a turnover? Any predictions on when it will occur this Fall?
Thanks!

[Dan Dutton]

Matt,

basically cooler, denser water sinks to the bottom as night temps drop and forces warmer water that has been there all summer to the surface.  This can lower oxygen levels in shallow waters and generally makes the lake muddy.  It's seen more in lakes that stabilize; smaller, deeper waters with less current or wind are more likely to do this.  The potomac won't do it because it is a river and the water is moving enough to keep it from getting as stratified.  

Many ponds and lakes around will experience fall turnover.  I noticed several small ponds last week that showed characteristics of fall turnover with those cool nights we experienced so it's already happening.  Luckily timing and intensity vary between lakes, so if one pond does it, another is probably not turned over yet or is already recovered into fall patterns.  

Dan

[Matt Geiman]

Thanks Dan! So I would assume areas like the duck pond and tidal basin would not be affected due to the tide mixing the water?