Perth Laboratory – Public Seminar Series 2007

Nutrient Loads in Isolated Wetlands of the Lake Okeechobee Basin

Professor Michael D. Annable
Department of Environmental Engineering Sciences
University of Florida

Thursday 18 October 2007 at 3.30pm, CSIRO Auditorium

Abstract

Depressional wetland hydrologic dynamics in the Okeechobee Basin, Florida are not well understood. Management of these wetlands is related to landscape-scale reduction of nutrient loads to Lake Okeechobee, where efforts are being made to attenuate the rate of hyper-eutrophication. Part of the total nutrient load to the lake originates from cow-calf operations in the lake catchment, which are managed to promote surface water drainage, because of shallow water table conditions. Six depressional wetlands in the Lake Okeechobee catchment were instrumented and monitored for three years to estimate the components of the water budget. A component of the instrumentation included passive nutrient flux meters to quantify groundwater nutrient exchange with wetlands. A drainage ditch location was also monitored. During the three monitoring years, the majority of water exported from the wetlands was due to surface water drainage through ditch networks (62%), followed by recharge to groundwater (21%), and then evapotranspiration (17%). Thus these wetlands are hydrologically connected to the upland pastures, primarily through runoff, and might be used as natural nutrient filters in the landscape. The potential for wetlands to attenuate nutrient loads from pasture runoff is likely a function of the extent of ditching. By removing ditches or controlling surface water outflow from wetlands, surface water recharge to groundwater becomes a more significant pathway for nutrient transport and retention. The information on water and nutrient exchange in wetlands and ditches within the Okeechobee Basin was used to scale up mass loads to assess the viability of using changes in management practices for improving water quality in the Basin.

About the speaker

Mike Annable is a Professor in the Department of Environmental Engineering Sciences at the University of Florida. He received his PhD from Michigan State University. His current research interests are in physical-chemical processes related to field scale application of innovative technologies for subsurface remediation and site characterization. His work has included applications of tracers for characterizing fluid volumes and interfaces in multiphase systems. He is currently investigating innovative techniques for measuring groundwater flow and contaminant flux in aquifers. He has published more than 60 journal articles and currently serves as an Associate Editor for the Journal of Contaminant Hydrology.

Professor Annable will be a keynote speaker at the forthcoming Groundwater Quality 2007 conference in Fremantle in December.

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