Stormwater ponds need to care too!

Stormwater ponds are commonly seen throughout the state of Florida. Typically, each is built with the intention to prevent flooding by giving rainwater an area of low elevation to run to and filter stormwater prior to it entering larger watersheds sheds. Stormwater basins are great at diverting and catching rain to prevent flooding. However, more often than not, stormwater ponds themselves are being overloaded with nutrients. This overloading makes the ponds ineffective for treating the stormwater and results in green, algae covered bodies of water that can present human and wildlife health risks.

High nutrient loads are brought to the ponds from runoff water. Prevention is a simple and effective method of lowering nutrient loads. If there are less nutrients to runoff into the stormwater area, then there is less potential for the pond to be overloaded. One way to lower nutrient loads is through proper lawn fertilization, as over fertilization is one of the major causes of high concentrations of nutrients reaching water sources.

To understand proper fertilization, it is important to know what is already in the soil, what kind of grass is growing, and how large your lawn is. Soil testing can be done through the UF/IFAS Extension Soil Testing Laboratory to assist with understanding the nutrients and minerals present in your soil. More information on soil testing can be found here: UF/IFAS Analytical Services Laboratories(ANSERV Labs) (ufl.edu). Please note that soil testing cannot give information on the amount of nitrogen in the soil as nitrogen is rapidly changing in response to varying factors in the soil community. However, soil testing can give crucial information on phosphorus and potassium levels in the soil, as well as other nutrients. Additionally, the type grass growing will also impact what kind of fertilizer should be applied. For example, turfgrass usually doesn’t require the addition of phosphorus, so phosphorus should not be present in the fertilizer being added to the lawn unless the soil test reports that it is needed. Lastly, the size of your lawn along with the other factors will determine how much fertilizer should be applied. Additional questions about proper lawn fertilization can be resolved by reaching out to your local extension office.

In addition to preventing high nutrient loads from approaching the stormwater area, the stormwater basin should have some sort of vegetative buffer along the banks. Stormwater ponds should not be bare on the banks. Not only does the buffer intake nutrients from runoff, but it also prevents soil and grass clippings from being drawn down into the water. The buffer zone along the edge of stormwater area and within the pond’s shallow area can be broken down into four zones: offshore (in the water), water’s edge, bank slope, and the bank top (farthest from the water). When vegetation is planted, varying water levels and the slope of the bank should be taken into consideration. Additionally mowing should be done on the outside of the buffer, and not down to the water’s edge. Aquatic plants also assist with prevention of erosion, nutrient management, and provide habitat for predatory insects which can prevent additional invertebrate pests from becoming a problem. One common pest that loves impaired water bodies are midge species, see https://edis.ifas.ufl.edu/publication/IN825

Remember though, the presence of vegetated buffers does not mean that overfertilization is acceptable. The buffers can only prevent so many nutrients from entering the water space. The higher the concentration of nutrients, the less effective the buffers are at controlling the nutrient load. Together, these methods can improve stormwater ponds, which will help lead to healthier waterways.

References:

SL21/LH014: General Recommendations for Fertilization of Turfgrasses on Florida Soils (ufl.edu)

FOR347/FR416: A New Database on Trait-Based Selection of Stormwater Pond Plants (ufl.edu)

UF/IFAS ANSERV Labs- Extension Soil Testing Lab FAQs (ufl.edu)