Selected Projects

Wekiva Aquifer Vulnerability Assessment (WAVA)

The hydrogeology of the Wekiva River study area is characterized by moderate to no confinement and a multitude of karst features. Groundwater recharges the Floridan Aquifer System (FAS) by infiltration through these sediments or directly through sinkholes. The Wekiva River Coordinating Committee Final Report identifies numerous studies by Florida’s water management districts and the United States Geological Survey (USGS) that clearly demonstrate contamination attributable to changes in land use. Therefore, the FGS was authorized under the Springs Initiative and the Wekiva River Coordinating Committee to identify zones of aquifer vulnerability, for the Floridan Aquifer System, within the Wekiva River study area.

The Wekiva Aquifer Vulnerability Assessment (WAVA) is a model that uses existing geographic information system data for the prediction of vulnerability zones and is based on the weights of evidence (WofE) modeling technique used in the statewide Florida Aquifer Vulnerability Assessment (FAVA). Use of WofE requires the combination of diverse spatial data which are used to describe and analyze interactions and generate predictive models. Additional information about the WofE technique can be found in FGS Bulletin 67, Florida Aquifer Vulnerability Assessment: Contamination potential of Florida’s principal aquifer systems (in preparation). 

In WAVA the spatial data is composed of a training point theme and evidential themes. The training point theme consists of locations of known occurrences. In WAVA these are wells that exceed a certain concentration of dissolved oxygen. Wells with high dissolved oxygen concentrations are indicative of areas where a good connection exists between the top of the aquifer and land surface. The evidential themes include soil permeability, buffered effective karst features, Intermediate Aquifer System (IAS) thickness and head difference between the Surficial Aquifer System and the Floridan Aquifer System. These themes act as evidence in the model by either protecting the aquifer from contamination or allowing contamination to move quickly from land surface to the top of the aquifer system (i.e., areas of thick IAS sediments versus areas of thin IAS sediments). The WofE technique quantifies relationships between these evidential themes and the training point theme in order the predict zones of vulnerability. These zones are classified into a primary protection zone, a secondary protection zone and a tertiary protection zone. These protection zones will be used in decision making, development of rules, or policies regarding environmental conservation, protection, growth management and planning.

A final report on the WAVA project was published as FGS Reort of Investigation 104, available at:  http://www.dep.state.fl.us/water/wastewater/dom/docs/RI_104a_FGS_Report.pdf