water quality program manager
Iowa State University Extension and Outreach
As fall temperatures arrive, pond owners have an opportunity to assess the quality and condition of their ponds before winter.
Many Iowa pond owners have reported issues with algae and sedimentation this summer, with some saying this is the first year they’ve had issues with their ponds.
Part of what is happening is that 2021 was a very dry year, which meant that many nutrients like nitrate didn't move out of the soil profile. Many areas of Iowa saw a 'flush' of nitrates this spring when the rains did come, which may have led to higher concentrations of nitrates compared to previous years.
Excessive amounts of algae and other aquatic vegetation grow because of an overabundance of nutrients like phosphorus and nitrogen. The best way to manage algae is to limit the amount of sediment and nutrients going into your pond by planting a buffer area directly around the pond.
Some algae and aquatic vegetation are good and necessary for a healthy waterbody. But if algae is excessive or if there are harmful algal blooms present, solutions include physically raking or removing the algae, stocking certain fish species, nontoxic dyes that limit light availability to plants, as well as herbicide control.
Pond owners with sedimentation issues can install buffers, discourage geese around the pond, build a settling basin upstream that intercepts soil particles, and plant a windbreak with trees or shrubs up wind of the pond.
If sediment is suspended in the water and does not settle to the bottom after 24 hours, the issue is likely a chemical imbalance. Pond owners should first measure the pH of the water and, based on the results, consider treating with the appropriate amount of gypsum, epsom salts, aluminum sulfate or limestone.
Both articles provide useful links and additional resources for preventing and treating pond issues.
Each pond is part of a watershed and that whatever Iowans do to safeguard the water quality of their ponds will also be beneficial for the watershed at large.