HR: 0800h
AN: H41F-0349    [Abstracts]
TI: Phosphorus Treatment in Spatially Distributed Isolated Wetland Systems of the Okeechobee Basin, FL
AU: * Perkins, D B
EM: dbperkins@ifas.ufl.edu
AF: University of Florida Soil and Water Science Dept, 2169 McCarty Hall Soil and Water Science Dept University of Florida, Gainesville, FL 32611-0290 United States
AU: Jawitz, J W
EM: jawitz@ufl.edu
AF: University of Florida Soil and Water Science Dept, 2169 McCarty Hall Soil and Water Science Dept University of Florida, Gainesville, FL 32611-0290 United States
AU: Olsen, A E
EM: aeolsen@ifas.ufl.edu
AF: University of Florida Soil and Water Science Dept, 2169 McCarty Hall Soil and Water Science Dept University of Florida, Gainesville, FL 32611-0290 United States
AB: A first-order degradation, one-dimensional steady state water flow model was developed to simulate phosphorus (P) treatment efficiency of spatially distributed isolated wetlands (IWs) typical of those in the Lake Okeechobee Basin, FL. Field measurements of groundwater gradients, coupled with surface water hydro- and P chemographs from ditched IWs, added insight to the dynamics and mechanisms involved in P treatment and transport in the landscape as well as the soundness of some model assumptions. This region is of interest because it is currently the largest non-point exporter of P to Lake Okeechobee, which supports wildlife, recreation, and contributes to deep-aquifer recharge. Isolated wetlands may exhibit sporadic hydraulic connectivity with nearby surface water bodies; however, groundwater connectivity may often play a leading role in water and contaminant transport pathways. Three parameters were evaluated in the watershed-scale treatment of P: 1) spatial distribution of wetlands in the landscape, 2) areal coverage of water in the landscape, and 3) wetland P degradation coefficient. A system of two wetlands was evaluated for five different spatial arrangements. The areal coverage of wetlands in the landscape was varied from 0 to 16 percent of the entire landscape. The P decay coefficient for the wetland was varied between 0.01 and 10 [yr-1]. Maximum treatment of groundwater P at the watershed outflow boundary ranged between 20 and 28 percent, based on the independent treatment contribution of each wetland across the water flow field. Measured groundwater gradients revealed that, during rainfall events, groundwater entered the IWs from nearly all directions and comprised a significant portion of the surface water outflow from the IWs. Phosphorus chemographs showed a relatively high initial mass flux out of the wetland at the beginning of the wet season. Simulations show that under steady state non-ditched water flow conditions in the Lake Okeechobee Basin, spatially distributed IWs may promote P reduction from agriculturally impacted waters. Field data demonstrated that ditched IWs are less likely to reduce P loading because event-driven surface water outflows decrease water retention in the wetlands.
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1836 Hydrologic budget (1655)
DE: 1871 Surface water quality
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting