projects > geophysical studies of the southwest florida coast > 1999 proposal
Project Proposal for 1999
Project number: 7310-37300
Program(s) (list all programs to which this work plan is being submitted):
Program element(s)/task(s) (show percent distribution if more than one element/task). If submitting to more than one program, include element(s)/tasks from each program here:
Project objectives and strategy: Water quality in coastal areas of South Florida such as the Everglades National Park (ENP) and the discharge of fresh water into Florida Bay are closely tied to water use and water management policies. Determination and monitoring of water quality is essential to restoration of the South Florida ecosystem (SFE). The flow of fresh water through the Everglades into Florida Bay is critical to the well being of the SFE. Increased domestic use of water, drainage of land to allow farming, increased farming and subsequent nutrient loading of runoff, and changes in water management practices over the years have had a profound effect on the SFE. Monitoring of these effects is made difficult by the inaccessibility of much of this area. Airborne geophysical methods provide a means of rapidly and economically monitoring large areas where access is difficult.
This project relies upon the fact that changes in water salinity produce changes in specific conductance (SC) or water resistivity. Changes in SC produce changes in the bulk resistivity of geologic materials.
We utilize several electromagnetic geophysical techniques to map ground resistivity, each having different depths of exploration and preferred targets. Our primary tool is helicopter electromagnetic (HEM) surveying which allows rapid mapping of large tracts of otherwise inaccessible terrain. HEM
Potential impacts and major products: Describe expected outcomes, both
Collaborators, clients (Names, affiliation, and roles of internal and external users of information generated by project) :Within USGS there has been collaboration with WRD-Miami on mapping the FWSWI in the southern part Dade County. Roy Sonenshein and Clinton Hittle have provided equipment and field help, and I have provided geophysical expertise. Gene Shinn (GD-St. Petersburg) has drilled several monitoring wells, Bob Halley has been invaluable in discussing applications of our data to his studies of Florida Bay salinity. Collaboration with Eric Swain (WRD-Miami) will be increased as he develops his SICS hydrologic model.
There has been considerable extramural collaboration. I have worked closely with the members of the ENP hydrologic staff (Robert Fennema, Tom Van Lent, Freddy James, Bob Zepp). The Park has provided field support in the form of vehicles (truck, airboat, and helicopter) and personnel for logging operations. We have co-authored a paper on the results of helicopter electromagnetic mapping and a report on the influence of roadways on surface-water flow in ENP. ENP staff has provided information on and access to wells inside the ENP, as well as GIS information for incorporation into map products.
Aaron Higer has provided many valuable contacts with the SFWMD. Of greatest importance was the commitment of Keith Smith and Milt Switanek to drill seven monitoring wells for this project. Five of these wells are inside the ENP and two are on SFWMD right of ways. Robert Fennema obtained the necessary permits to drill inside ENP, and Switanek did the same for the other wells.
Richard Green and Ken Campbell (Florida Geological Survey) have provided geologic maps from the Homestead area for use by this project. I have provided them with HEM apparent resistivity maps which they have used to help locate push-core sites for their mapping in the western part of ENP.
Gwen Burzycki of DERM and Bob Kesler of Florida Power and Light have expressed interest in having an HEM survey flown in the area between U.S. 1 and Card Sound Road (immediately adjacent to the eastern border of our study area), but funding obstacles still remain.
I maintain contact with hydrologists from the U.S. Army Corps of Engineers who are formulating a hydrologic flow model for South Florida. This includes Jerry Linn of Vicksburg and Jim May from Jacksonville. I will be providing them with resistivity depth models this summer for incorporation into there hydrologic models.
FY 1999 activities: Statement of the work to be undertaken in FY 1999 and a description of the methods and procedures.
This fiscal year will devoted to completing data interpretation work and writing reports and summary papers synthesizing all of the work done to date on this project. As these results become available we will be spending time working with the hydrologic modelers who can directly benefit from these results.
FY 1999 deliverables/products: Describe in more detail the specific deliverables/products that will result from this work in FY 1999.
1. Open-file report describing the interpretation of the TEM data (publication FY-99). These data will also form the basis of a journal article.
FY 1999 outreach: Emphasizing FY 1999, describe plans to address client requirements, decisions, and deadlines.
Outreach activities will focus primarily on working with ground-water modelers with USGS/WRD, the U.S. Army Corps of Engineers, and Everglades National Park. Researchers in these groups are at the point where they can use the 3-D water salinity data from this project for their solute transport model studies.
New directions or major changes for FY 1999 (if applicable):
No new directions or major changes are anticipated for FY-99.
ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH
FY 1998 accomplishments and outcomes, including outreach:
During the course of the year, a question had arisen as to whether or not our geophysical measurements could be used to confirm or refute the "River of Sandä hypothesis. The proponents of this idea claim that there is a coarse grained, sand zone which transports water from near Lake Okeechobee to Florida Bay. Examination of our data suggest that no such feature exists, though it would be possible to bury, thin resistive zones, which simulate fresh-water saturated sands, into the preferred inversion models. Such models could not be distinguished from the optimal model, nor could the parameters of these resistive zones be resolved. This means that such models are allowable, but neither required nor well defined. Accordingly we have concluded that such a scenario is geophysically unlikely. If these thin, resistive zones are real, and produce by thin, fresh-water saturated sands, they pose some serious questions for the hydrologist to answer, such as 1) How is this zone hydrologically separated from the saline saturated aquifers above and below it?, 2) How would such a zone outcrop into Florida Bay?, and 3) Why have no fresh-water seeps been observed in Florida Bay?
It should be noted, however, that we have noticed a high resistivity zone to the southeast of Taylor Slough in the transient electromagnetic data. This is a very thick zone buried about 20 m deep. The exact cause of these zone is not yet certain, but it does correspond to the southward protrusion of the HEM resistivity contours to the south. However, the TEM resistive zone is much deeper than can be measured by the HEM data. This feature is intriguing, probably related to geologic controls on the location of Taylor Slough, and not completed understood at this time.
FY 1998 deliverables, products completed:
The following papers were written during FY-98
1. Fitterman, David V., 1997, Analysis of errors in HEM calibration data: U.S. Geological Survey Open-File-Report 97-742, 28 p.
The following abstracts were written during FY-98
1. Fitterman, D. V., and Deszcz-Pan, Maryla, 1997, Geophysical mapping of the freshwater/saltwater interface in Everglades National Park [abstract], in Gerould, S., ed., U.S. Geological Survey Program on the South Florida Ecosystem-Proceedings of the Technical Symposium in Ft. Lauderdale, Florida, August 25-28, 1997, U.S. Geological Survey Open-File Report 97-385, p. 13-14.
The following posters were presented during FY-98
1. Fitterman, D.V., and Deszcz-Pan, Maryla, 1997, Geophysical mapping of the freshwater/saltwater interface in Everglades National Park: U.S. Geological Survey Technical Symposium on the South Florida Ecosystem, Ft. Lauderdale, Florida, August 25-28, 1997
Work continues on the following products and should be completed in FY-98:
1. Open-file report describing the interpretation of the TEM data. These data will also form the basis of a journal article to be completed in FY-99.
PROJECT SUPPORT REQUIREMENTS
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Major equipment/facility needs (list by fiscal year for duration of project):