LITTLE ROCK, Ark. (KTHV) - We recently received a video of a Judsonia pond turnover. It was obvious because of the abundant dead fish and the murky water. How is Arkansas’s weather to blame?
A pond turnover happens because of changes in the pond’s water properties such as temperature, density and oxygen levels.
In the Spring, ponds are uniform (or close to it) in temperature from the surface to the bottom and as a result, oxygen levels are too. The spring sun warms the surface of the pond and the windy spring weather works to mix the warm surface with the cooler water underneath.
During the summer months, surface water temperatures warm quickly. Warm water is less dense and stays at the surface while cold water is denser and sinks to the bottom. The cold layer of water at the bottom typically has less oxygen while the oxygen-rich, warm layer stays at the surface.
Depending on pond depth, the temperature contrast from bottom to top can be around 20 degrees!
A light summer breeze is not typically sufficient to mix the ponds. During this time, fish are more likely to stay close to the surface where the oxygen is highest. As summer goes on, oxygen levels at the bottom of the pond can decrease significantly.
Suddenly, a strong summer thunderstorm rolls through with heavy rain and fierce winds quickly mixing the oxygen-depleted cold water with the surface. This causes the whole pond to be oxygen depleted, resulting in dead fish.
This is what happened to the pond in Judsonia. The area is under a moderate drought. The last significant rainfall happened on May 17 with nearly four inches of rain that week. As the summer months progressed, White County got by with a few bursts of summer rain. July 7 rolled around and a storm dropped almost an inch and a half of rain.
While the rain was beneficial to the land, it was deadly to some of the pond’s fish.