Pond Turnover: What Causes It?
What causes a pond to turnover in the middle of the summer?
Nashville, Ark. – Turnover is the gentle, natural mixing of pond and lake waters. It is caused by changing temperatures in surface waters brought on by the progression of the seasons. In Arkansas’ continental-temperature climate, most ponds and lakes turn over in both the fall and spring. Turnover occurs in the fall when surface waters cool, and in the spring when they warm-up again.
The density and weight of water change with temperature. Like most other liquids and gasses, cold water is both heavier and denser than warm water. Water has one unique property, however. It is most dense and heavier at 39°F. As water cools and approaches 32° F, its molecules actually expand and form the crystalline structure of ice. Ice floats because it is both lighter and less dense than the warmer 39° F water beneath it. It is this unique property, which makes it possible for aquatic life, including fish to over-winter in streams and rivers, ponds and lakes. If water’s weight and density were greatest at 32°F ponds, lakes, streams, and rivers would become solid ice!
Your pond has four stages in its annual cycle. As you might expect, these stages parallel the four seasons of the year. They are:
- Summer Stratification
- Fall Turnover
- Winter Stratification
- Spring Turnover
Obviously, no two ponds are exactly alike. Some ponds stratify strongly during the summer and some remain well mixed from top to bottom. Others never, or seldom, have an ice cover and do not experience winter stratification. Some of the factors that modify your pond’s annual cycle are climate, depth, topography, and pond size.
So what causes a pond to turnover in the middle of the summer? It is usually tied back to a quick cool down from a rain event and is typically a smaller pond that will turnover. Most people do not realize their pond has turned over, unless there is a fish kill. Small, shallow ponds will be more apt to turn over in the summer months and have greater fish kill than larger, deep ponds.
For more information on pond management contact the Howard County Extension office at 870-845-7517 or you may contact me via email at sbeaty@uada.edu .
By Sherry Beaty-Sullivan
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture
Media Contact: Sherry Beaty-Sullivan
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
421 N. Main Nashville AR 71852
(870) 845-7517
sbeaty@uada.edu
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