Stormwater Facilities and Mosquitoes: Get the Facts
Stormwater management facilities help remove pollutants from water and prevent flooding in our community. In order to do so, some of these facilities must temporarily or permanently retain water. If stormwater facilities are designed and maintained correctly, mosquito populations should not be a concern.
Facilities that hold water temporarily:
Examples include: Bioretentions, dry ponds, swales, and rain gardens.
If designed and maintained properly, all of these facilities should drain within one to three days. This is too little time to allow mosquitos to develop to maturity.
A residential rain garden in Columbia, Maryland
Facilities that hold water permanently:
Examples: Wet ponds and stormwater wetlands.
Our community has many wet ponds, including Centennial Lake and Lake Elkhorn. These facilities come in a variety of sizes, but all contain ecosystems with natural predators that feed on mosquitoes, such as frogs and dragonflies, which should keep mosquito populations in check.
Centennial Lake, a stormwater wet pond.
If you are concerned that the standing water in your rain barrel is allowing mosquitoes to lay eggs, you can: empty the barrel regularly (at least every 2-3 days), ensure that the screen between the downspout and entry to the barrel is a fine mesh with spaces smaller than an adult mosquito so they are unable to lay eggs on the surface of the water, or purchase mosquito prevention products such as mosquito dunks to treat water stored in the barrel.