Are storm water ponds mosquito habitat?

The in basket: This is the time of year we are reminded to eliminate mosquito breeding grounds, to minimize the possibility of a West Nile Virus illness, among other reasons. Health officials recommend dumping out old tires, rain barrels and anything else where water would be undisturbed.

I think of that as I pass many of the storm water detention ponds that have become a standard part of any road project or housing development. I asked Kitsap County Public Works, which manages those outside the cities and on county roads,  if there is anything the county does or advises nearby home owners to do to keep mosquitos from breeding in ponds that aren’t dried up yet.

The out basket: The county’s Surface and Stormwater Management Program gave me this answer:

“Storm water ponds and other water quality treatment facilities are designed to filter pollution from storm water runoff and reduce flooding. Most facilities built into residential and commercial developments are designed to drain in a few days. This prevents mosquito larvae from completing their development.

“Some storm water ponds and water quality facilities are designed to hold water most of the year or may retain small pools of water. In addition to treating storm water, these facilities are generally designed to provide habitat for many species of frogs, birds, fish and aquatic insects that feed on mosquitoes and their larvae.  The wetland vegetation planted around the perimeter of these ‘wet ponds’ also serves to inhibit mosquito larvae development while providing habitat for mosquito predators.

“A small field survey conducted by Kitsap County Public Works and the Kitsap County Health District in 2003 confirmed that when these facilities are properly maintained they do not appear to create large populations of mosquitoes. This is also demonstrated by research in other parts of the country. Kitsap County Public Works has a rigorous operations and maintenance program to ensure our storm water treatment facilities function properly.

“Residents should not attempt to control mosquito populations in storm water ponds.  The use of larvicides or other chemicals in storm water facilities is regulated by the State Department of Ecology and requires state licensing and permits. These pesticides can be harmful to native biota such as salmon and trout. Storm water ponds often have a connection to natural streams or other water bodies. Because of that relationship chemicals used to control mosquitoes could end up harming fish and wildlife downstream.

“If residents suspect that storm water ponds are not being properly maintained, contact Kitsap 1 by email at or by phone at 360-337-5777. For information about West Nile Virus visit the Kitsap County Health District’s website at or call 360-337-5285.”

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