2nd UF Water Institute Symposium Abstract

Submitter's Name Jennifer Mitchell
Session Name Poster Session: Hydrologic, Biogeochemical and Ecological Processes 1
Category Hydrologic, biogeochemical and ecological processes
Poster Number 227
Author(s) Jennifer Mitchell,  University of Florida Soil and Water Science
  James Jawitz,  University of Florida Soil and Water Science
  Phosphorus loading of two isolated wetlands in the Okeechobee Basin
  The phosphorus load to Lake Okeechobee consistently exceeds the mandated total maximum daily load (TMDL) of 140 Mtons annually. Excess P loading to the lake is a concern because of algal blooms and a shift in trophic status from eutrophic toward hypereutrophic. One proposed practice for reducing P loading is restoration of isolated wetlands that historically have been ditched and now drain directly to Lake Okeechobee. This study examines hydrologic restoration of an approximately 1.1ha ditched wetland in the Okeechobee basin. The ditch draining the wetland was blocked with a 30-cm dam and the water and nutrient budget of the wetland was monitored and compared to a similar, ditched wetland in the same cow-calf pasture that was not dammed. It is hypothesized that the load exported from the restored wetland will be less than that of the ditched wetland. Ditch discharge was measured every 30 minutes with an acoustic Doppler velocimeter (ADV) allowing both backflow into the wetlands and discharge from the wetlands to be determined. Two automatic water samplers were installed in each wetland, one in the center of the wetland and the other in the ditch. Samplers were programmed to sample when the attached pressure transducers detected a proscribed change in water level and/or every 24 hours both to measure P export and to detect changes in P concentration as a response to rewetting or drawdown in the wetland. Backflow from the ditches into the non-dammed wetland does contribute to a rise in wetland water level. Results of this study will help to determine P sequestration rates that can be expected with restoring isolated wetlands and the effectiveness of this practice to reduce loading to Lake Okeechobee.