Water Circulation & Dilution Projects

Water Circulation 01

As water circulates in surface water bodies, it can transport waterborne contaminants and dilute initial concentrations of released materials. As part of a large investigation at Key West Harbor, Water & Air personnel used drogues to measure current speed and direction over a one-month period to determine typical transport pathways for turbidity plumes that might be generated by ship traffic or dredging activities. At a bayou in Pensacola, Florida, drogues were used over three days to determine the potential for stagnation in the inner waterfront portion of a former shipyard that was being considered for conversion into a marina and boat storage facility. A Water & Air field team used drogues before and during a dilution investigation in Lake Harris near Eustis, Florida, where dye was released to simulate dilution of a released contaminant. Development permit requirements specified that any contaminant spills, e.g., sewage, must become diluted to 10% of the initial concentrations within 96 hours.

Task Summary

  • Deployed drogues or environmentally-appropriate dye to collect speed and direction data for water masses in an ocean-harbor area, a lake, and a bayou.
  • Released dye and monitored its dispersion for 96 hours.
  • Downloaded antecedent and concurrent weather data from nearby airports to assist in data interpretation and support project findings.
  • Reported all data to clients in graphical and tabular formats with appropriate text and figures.


Current data from the area in and around Key West Harbor showed that water movement was predominantly tidally driven, although wind is a force that can strongly influence both speed and direction. The Key West data were used to formulate a monitoring program for turbidity plumes that may originate from planned dredging activities. Circular flow patterns similar to gyres were documented in Key West Harbor and at the bayou site. For Lake Harris, graphics of circulation patterns during calm conditions and figures of dye concentration isopleths documented that dilution of released constituents was achieved within a few hours of dye release.

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