When a pond experiences rapid turnover, it can cause lead to the death of aquatic life, and an unpleasant fish kill clean-up. Preventing turnover from happening takes a multifaceted approach that begins with construction, if the pond is human-made, and can be aided by aeration, controlling aquatic weeds, and reducing the nutrient load.
Proper Construction
One way to prevent pond turnover is by making sure it is constructed to discourage stratification. Ponds built with the proper ratio of surface water to deep water are less likely to turn over, and when they do, the severity will likely be less. Ponds with more surface area and shallower bottoms tend to turn over less because the lack of cool deep water deters stratification. In contrast, deep ponds with little surface area are more prone to turnover because there is more low oxygen cold water than warm surface water, which can lead to stratification. Thus, a primary risk factor for pond turnover is stratification.
Water Mixing
It can be helpful to have aeration systems in ponds, but these are usually different than decorative fountains. Rather than having a purpose of beautifying the pond, these systems keep the water mixed to prevent stratification and turnover.
Weed Control
Ponds with surface weeds, floating and submersed weeds can impede oxygen diffusion and water circulation. In addition, they take oxygen from the water after they die, making the control of aquatic weeds an important step in preventing turnover.
Nutrient Reduction
Many human activities can impact pond conditions that could lead to turnover. Ponds that receive runoff from yards containing pet waste and fertilizers and those collecting sediment, trash, and debris from the feeding of ducks and geese are prone to an overgrowth of algae. The algae need oxygen to survive and pull it from the pond causing an oxygen depletion scenario that can lead to stratification and turnover. Reducing the amount of nutrients in the runoff water entering the pond can also help reduce the amount of algae, improve water turbidity, deter the growth of aquatic weeds, noxious odors and other unpleasant outcomes for pond health,
Turnover can be a natural event when the seasons change or after a particularly stormy, windy, or cold rainy day. However, unnatural turnover happens rapidly due to human activities and their impact on the pond ecosystem.