In some ways, ORCA owes its existence to the mosquito. The ORCA landscape is dominated by impoundments built to influence mosquito breeding. While helping to keep the mosquito population low, the impoundments are a valuable living space for a whole host of other animals and plants.
A mosquito control impoundment is a coastal wetland with an earthen dike around all or part of its periphery. This allows flooding the marsh during the mosquito producing season (approximately May to October). The salt marsh mosquitoes, Aedes taeniorhynchus and Aedes sollicitans, will not lay their eggs upon standing water, so flooding the marsh prevents mosquito production without having to use pesticides. A variety of water control structures, such as pumps, culverts and spillways, are used to manage water levels. In addition to mosquito control, impoundments can be managed for a variety of purposes, such as waterfowl habitat, fisheries, storm water treatment and many others.

The two ORCA Impoundments (133 acres and 53 acres) were constructed between 1958 and 1963. For approximately 30 years, there was no connection between these impoundments and the Indian River Lagoon (IRL). In the early 1990s, through cooperation between the St. Johns River Water Management District's (SJRWMD) Surface Water Improvement and Management (SWIM) Program and the Indian River Mosquito Control District (IRMCD), a Rotational Impoundment Management (RIM) plan was instituted in one of the impoundments. Impoundment #18 now contains nine - 30 inch diameter culverts with water control structures that allow for a seasonal connection of the impounded marsh and the IRL. The culverts are closed in the late spring, when estuarine water is pumped into the impoundment with an electric 6000 gpm pump. This flooding continues at minimal levels until early fall when the culverts are opened allowing free exchange of water and organisms between the marsh and lagoon. The southeast impoundment is managed to maintain water levels conducive to waterfowl habitat enhancement during the fall and winter.

Today the ORCA Impoundments are managed by the Indian River Mosquito Control District.
       
Learn more about the life cycle of the mosquito by visiting LIFE IN THE PITS!
 
 
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