Project Summary Sheet

Project Title: Groundwater-Surface Water Interactions and Relation to Water Quality in the Everglades

Project Start Date: FY96 Project End Date: FY05

Web Sites: http://sofia.usgs.gov/projects/wtr_flux/; http://sofia.usgs.gov/sfrsf/entdisplays/waterlevels/; http://sofia.usgs.gov/exchange/harvey/harveyDATA.html

Location (Subregions, Counties, Park or Refuge): Central Everglades (Water Conservation Areas and Stormwater Treatment Areas) and Everglades National Park; Palm Beach, Broward and Dade Counties

Funding Source: Approximately half from USGS's Greater Everglades Science Initiative (PBS) and half from SFWMD

Principal Investigator(s): Judson Harvey (jwharvey@usgs.gov)

Project Personnel: James Krest (jmkrest@usgs.gov), Jessica Newlin (jnewlin@usgs.gov), Eric Lerch (eplerch@usgs.gov)

Supporting Organizations: South Florida Water Management District (Steve Krupa, skrupa@sfwmd.gov)

Associated / Linked Projects: Integrated Geochemical Studies in the Everglades http://sofia.usgs.gov/projects/wetland_seds/; http://sofia.usgs.gov/projects/evergl_merc/; Tides and Inflows at the Mangrove Ecotone (TIME) http://time.er.usgs.gov/

Overview: The objective of this project is to quantify transport and fate of dissolved contaminants such as nutrients, sulfate and mercury in the Everglades system, with particular concern for the effects of water and solute exchange between surface water, peat porewater, and ground water in the underlying limestone/sand aquifer system. The principal research sites are the "nutrient threshold" transects in Water Conservation Area 2A (WCA-2A), and Taylor Slough and Shark Slough in Everglades National Park.

Status: A key measure of success in the Everglades restoration is protecting water quality under changing hydrologic conditions. Two fundamental questions are being addressed: 1) at what rate will the contaminants (nutrients, sulfur, and mercury) that are already stored in peat and the underlying aquifer of the Everglades be returned to surface water as a result of surface water and groundwater interactions, and 2) how will the restoration's hydrologic modifications further modify these processes and how will Everglades water quality be affected? Our research has produced some of the first estimates of key parameters that are needed for reliable water-quality modeling that considers surface water and groundwater interactions. Products include journal publications, USGS data reports, reports for the SFWMD, meeting and workshop presentations, and online accessible versions of data and reports on SOFIA.

Recent and Planned Products: We recently reported on occurrence and fate of mercury in ground water (Harvey et al, 2002), a new method to quantify recharge and discharge in the Everglades using natural distributions of radium isotopes (Krest and Harvey, 2003), and a comprehensive treatment of recharge and discharge in WCA-2A (Harvey et al., 2003; Harvey and others, 2003). In the fall of 2002 we successfully tested a new method of solute tracer experimentation in the Everglades that was well received at the 2003 GEER conference. Our reports and data are providing key information for hydrologic and ecological models that are being used to guide the restoration in the central and southern Everglades.

Relevance to Greater Everglades Restoration Information Needs: Successful restoration of the Everglades requires comprehensive knowledge of surface-subsurface hydrologic exchange and its effects on water quality. Our research has helped reduce uncertainty in the water budget in certain areas, such as Taylor Slough where the contribution from groundwater discharge was previously unknown. Our research also is establishing linkages with water-quality processes, through a scientific assessment of the “legacy” effect of contamination in the peat and aquifer, and likely effects of the upcoming hydrologic modifications on the fate of those stored contaminants. Our data and interpretations are providing principal inputs to the key hydrologic and water-quality models, including TIME (USGS-Schaffranek), SFWMM (SFWMD-Obeysekera), STA Design Assessment (SFWMD-Kadlec, Walker, and Chimney), and ELM (SFWMD-Fitz).

Key Findings:

• First independently verified estimates of recharge and discharge in the vast interior wetlands of the Everglades.
• Published definitive estimates of recharge and discharge in the SFWMD's ENR project (a prototype treatment wetland), which revealed role of groundwater in water budgets and nutrient removal in Stormwater Treatment Areas (STAs).
• Provided crucial field measurements that constrained ungaged estimates of discharge of fresh groundwater into Taylor Slough, Everglades National Park.
• Demonstrated that water management has had the unintentional effect of increasing recharge and discharge in the central Everglades, concomitantly increasing recharge of dissolved contaminants (e.g. mercury, sulfate, and nutrients) into the aquifer. This "legacy" of stored subsurface contamination could affect future water quality in the Everglades.