The Influence of The Duncan Dam on the Mosquito
   Populations of the Lower Duncan Floodplain - Summer 2002

Slide Show Presentation         
Duncan Mosquito Final Report in PDF format


             A Study Undertaken on behalf of The Duncan
           Water Use Plan Consultative Committee

     The Objectives

  • To establish the potential causes behind the reported extension in the duration of the mosquito-hatching season in the Lower Duncan floodplain


  • To make recommendations for minimizing mosquito-breeding opportunities through appropriate control measures, such as operating alternatives for the Duncan Dam
Questions?

  • Which species of mosquito are present and where do they breed?
  • Are some species more troublesome than others?
  • Can mosquito breeding habitats be related to vegetation types?
  • Can hydrology be linked to vegetation types?
  • Could historical data be used to determine the cause of 'good'
    and 'bad' mosquito years?


Conclusions:

  • Low Bench associations form 85% of the potential mosquito breeding grounds
  • Different vegetation types form species- specific mosquito breeding habitat
  • Different vegetation types appeared to match particular flooding regimes, although more work needs to be undertaken to confirm this
  • The main problem to residents of the Lower Duncan Floodplain are the Aedes species
  • The Aedes species breed predominantly in Low Bench areas, particularly open grassland and riparian sandbars
  • The wetlands (marshes, swamps and fens) act as breeding grounds, but for other species that feed mainly on birds, amphibians and plants
  • Aedes hatch mainly during May and June when there is no influence from the Duncan Dam
  • Prolonged snowpack and the consequent delay in the Lardeau freshet, which thus occurs at warmer air temperatures, appears to be associated with above average first hatches
  • Kootenay Lake levels may also be critical to the initial Aedes hatch
  • Heavy precipitation in May and June may also create temporary pools favoured by Aedes species
  • High discharges from the Duncan Dam in July and August cause Meadow Creek to back up and can cause extensive flooding elsewhere in the floodplain
  • Reflooding causes a renewed hatch of Aedes, although this is unlikely to be as pronounced as the earlier hatch
  • Reflooding provides new opportunities for egg-laying
  • Climatic factors largely determine the extent of the Lardeau freshet in the Spring. The timing and amplitude of the Lardeau freshet, and air temperature and rainfall at the time may be crucial in determining mosquito breeding success
  • 'Bad' mosquito years may have partly resulted from prolonged above average flows in the River Lardeau below the Duncan Dam during July and August


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