HR: 1400h
AN: H53D-03    [Abstracts]
TI: Quantifying Hydrologic Pathways in Depressional Wetlands Through a Water Budget Approach: Implications for Determining Landscape-scale Nutrient Treatment Potential
AU: * Perkins, D B
EM: perkinsd@ufl.edu
AF: University of Florida - Soil and Water Science Dept., 2169 McCarty Hall A, Gainesville, FL 32611, United States
AU: Jawitz, J W
EM: jawitz@ufl.edu
AF: University of Florida - Soil and Water Science Dept., 2169 McCarty Hall A, Gainesville, FL 32611, United States
AU: Annable, M D
EM: annable@ufl.edu
AF: University of Florida - Environmental Engineering, 353 New Engineering Bldg, Gainesville, FL 32611, United States
AB: Depressional wetland hydrologic dynamics in the Okeechobee basin, FL 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. Four depressional wetlands in the Lake Okeechobee catchment were instrumented and monitored for three years to estimate the components of the water budget. The objectives of this study were 1) quantify wetland hydrologic inflows and outflows, 2) compare wetland inflows and outflows between four isolated wetlands, and 3) explore the potential role of these wetlands as a means to reduce nutrient export from agricultural settings. 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%). Rainfall on the wetland water surface and runoff (overland flow) were similar in magnitude and incorporated 96% of the total inflow to the wetlands, with the remaining 4% originating from groundwater discharge to the wetland. While recharge to groundwater from the wetland was only 21% of the total outflow, it occurred more frequently than surface export through ditches (67% and 25% respectively of total days with standing water). The relative amount of ditch flow across three wetlands was similar, however, the extent of ditching at the fourth wetland appeared to limit surface water outflow (84% reduction). These wetlands are hydrologically connected to the upland pastures, primarily through runoff, and might be used as natural nutrient filters in these landscapes. 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 an important pathway for nutrient transport.
DE: 1830 Groundwater/surface water interaction
DE: 1871 Surface water quality
DE: 1876 Water budgets
DE: 1879 Watershed
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: 2007 Joint Assembly