Metrological reports of significant El Nino related weather events for 2016 gave the District hope that underground storm drains, flood channels, ditches, gutters, and many other water conveyance systems would be flushed of debris. However, these rain events did not occur. Debris found in these systems impedes the flow of water and creates mosquito-breeding habitat. In addition to water conveyance systems lacking proper flushing, aerial surveillance photography conducted in April revealed thousands of previously unknown out-of-service residential swimming pools. Both of these factors contribute to higher mosquito populations, and the transmission of West Nile virus.
Recent heat waves shorten the amount of time it takes for mosquitoes to progress from egg to adult, and also encourage residents to spend more time outdoors during the early evening hours when mosquitoes are actively looking for a blood meal. As the temperature increases again, residents are reminded to apply mosquito repellent when outdoors, ensure window and door screens are in good repair, and dump and drain any standing water on their property.