What is turnover?

Posted: January 14th, 2015 by Bill Dance

Someone asked me the other day about the term “turnover.” I, of course, told them I prefer apple turnovers, but peach turnovers, are also…well…pretty peachy.

They didn’t think that was nearly as funny as I did, so I told them to go on YouTube and be sure to check out a blooper/mishap, or two…or three that by now, thanks to living much of my life on camera,…millions have seen. Everyone likes to laugh at my expense, but that too, is all in fun, and on a more serious note, I know well how the term turnover applies to fishing.

In fact, if it weren’t for a complete turnover twice a year, most lakes and ponds would become stagnant because of a continued buildup of oxygen-depleted water. As water temperatures drop, water becomes heavier and denser. Maximum density is reached when the water is 39.2 degrees F. Colder than that, water becomes lighter. That’s why ice floats on the surface. If water didn’t become less dense as it freezes, the ice would settle to the bottom of northern lakes and destroy aquatic life.

To trace the cycle: In the fall of each year, water temperatures drop and the heavier water falls to the bottom. This forces the bottom waters to the top, where they once again become re-oxygenated; when this happens, the lake is said to “turn over.” During this brief period, all levels of the lake have enough oxygen to support life, and bass could be scattered throughout any of the levels.

If the lake is far enough north for the water to reach 39.2 degrees or colder, the 39.2 degree-water will remain on the bottom and ice might coat the lake. The water in the intermediate levels will range between 39.2 degrees and 32 degrees.