Sweetwater Wetlands Mosquito Abatement

Tucson Water is a partner in local “Fight the Bite” efforts to protect residents from the West Nile and Zika viruses. Both can be transmitted to humans through bites of infected mosquitoes.

The best way to avoid contracting a virus is to prevent mosquitoes from breeding and biting. To avoid being bitten while at the Sweetwater Wetlands:

  • Limit your visit around dawn and around dusk. Mosquitoes are most active during these times.
  • Wear long sleeve shirts and pants when possible.
  • Use protection by applying mosquito repellents that contain DEET, Picaridin, or Oil of Lemon Eucalyptus.

In addition to the Mosquito Abatement Program at Sweetwater Wetlands, monthly monitoring of adult mosquito populations takes place at Tucson Water's CAVSARP and SAVSARP facilities in Avra Valley.

Additional Mosquito-Related Information:

Current Mosquito Abatement Efforts

The wetland ponds contain areas of deep, open water alternating with zones of shallow water planted with bulrush and cattail. Over the years, the shallow vegetated zones have been prone to produce mosquitoes, which are potential carriers of the West Nile and Zika viruses.

To avoid a potential public health risk, the City of Tucson has a mitigation program to control the mosquito population at the Sweetwater Wetlands and protect visitors from potential threats:

  • Staff applies bacterial larvicide to the ponds to stop mosquito larvae from growing into adults on a regular basis.
  • This larvicide is specific to mosquito larvae and does not harm any of the other wildlife or the habitat itself.
  • To kill adult mosquitoes, Tucson Water implements fogging, especially during the monsoon season (since mosquitoes thrive in higher humidity).
  • Every spring, Tucson Water and the Tucson Fire Department conduct a controlled burn that reduces mosquito habitat.
  • Every week, from March to October, a Tucson Water staff member sets six carbon dioxide traps around the Sweetwater Wetlands.
  • The trapped mosquitoes are then sent to University of Arizona entomologists for counts at the various locations and species identification.
  • Data indicates that total mosquito populations have been consistently declining since the beginning of the Mosquito Abatement Program.

History of Mosquito Abatement Efforts

Since construction of the Sweetwater Wetlands began in 1996, the City of Tucson has significantly reduced the mosquito population.

The site includes 17.5 acres of constructed wetlands, 14 acres of recharge basins, and a recurring mosquito problem. The Wetlands was initially constructed to treat filter backwash water from the City's Reclaimed Water Treatment Plant.

The treatment plant, built in 1984, used to produce reclaimed water by filtering secondary effluent from the Roger Road Water Reclamation Facility through granular silica/carbon filters. The filters plugged up periodically and plant operators had to backwash the filters to clean them.

The Wetlands was originally designed to receive and treat the backwash water produced during this process. The backwash water, high in suspended solids, drained by gravity into settling basins, wetland ponds, and eventually adjacent recharge basins.

Since 2014, the Wetlands no longer needs to treat backwash water because the tertiary effluent from the new Agua Nueva Water Reclamation Facility does not need to be filtered.