Development and Implementation of a Bayesian-based Aquifer Vulnerability Assessment in Florida |
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| Authors: | Jonathan D Arthur H Alex R Wood Alan E Baker James R Cichon Gary L Raines |
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| Institution: | (1) Florida Department of Environmental Protection–Florida Geological Survey, 903 W. Tennessee St., Tallahassee, FL 32312, USA;(2) Advanced Geospatial, Inc., 2441 Monticello Dr., Suite 600, Tallahassee, FL 32303, USA;(3) US Geological Survey, Western Mineral Resources Team, MS 176, c/o Mackay School of Mines University of Nevada at Reno, Reno, NV 89557, USA |
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| Abstract: | The Florida Aquifer Vulnerability Assessment (FAVA) was designed to provide a tool for environmental, regulatory, resource
management, and planning professionals to facilitate protection of groundwater resources from surface sources of contamination.
The FAVA project implements weights-of-evidence (WofE), a data-driven, Bayesian-probabilistic model to generate a series of
maps reflecting relative aquifer vulnerability of Florida’s principal aquifer systems. The vulnerability assessment process,
from project design to map implementation is described herein in reference to the Floridan aquifer system (FAS). The WofE
model calculates weighted relationships between hydrogeologic data layers that influence aquifer vulnerability and ambient
groundwater parameters in wells that reflect relative degrees of vulnerability. Statewide model input data layers (evidential
themes) include soil hydraulic conductivity, density of karst features, thickness of aquifer confinement, and hydraulic head
difference between the FAS and the watertable. Wells with median dissolved nitrogen concentrations exceeding statistically
established thresholds serve as training points in the WofE model. The resulting vulnerability map (response theme) reflects
classified posterior probabilities based on spatial relationships between the evidential themes and training points. The response
theme is subjected to extensive sensitivity and validation testing. Among the model validation techniques is calculation of
a response theme based on a different water-quality indicator of relative recharge or vulnerability: dissolved oxygen. Successful
implementation of the FAVA maps was facilitated by the overall project design, which included a needs assessment and iterative
technical advisory committee input and review. Ongoing programs to protect Florida’s springsheds have led to development of
larger-scale WofE-based vulnerability assessments. Additional applications of the maps include land-use planning amendments
and prioritization of land purchases to protect groundwater resources. |
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| Keywords: | Floridan aquifer vulnerability Florida Bayesian weights-of-evidence (WofE) |
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