USGS Water Division
Continuing Project Work Plan - FY 1999

IDENTIFYING INFORMATION
Project title: Ground-Water Discharge to Biscayne Bay
Geographic area: South Florida (Miami-Dade County)
Project start date: April 1996
Project end date: FY 1999 1

Project chief: John A. Passehl
Region/Division/Team/Section: Southeast Region/WRD/Miami/Investigations
Email: jpassehl@usgs.gov
Phone: (305) 526-2895
Fax: (305) 526-2881
Mail address: 9100 NW 36^th Street, #107, Miami, FL 33178

Program(s): Integrated Natural Resource Science (INATURES)

Program element(s)/task(s): South Florida, Element 3: Hydrologic Modeling and Support Studies, Task 3.2: Ground-Water Discharge to Biscayne Bay

BACKGROUND NARRATIVES
Project summary:
Everglades restoration involves both operational and structural changes to water management in south Florida. Management agencies need to know the effect that these changes in operation of gages and control structures in canals will have on the rate of ground-water discharge to Biscayne Bay. The goal is to determine current ground-water discharge and then access effects of management activities on discharge to the bay.

The U.S. Army Corps of Engineers (USACE) and the South Florida Water Management District (SFWMD) will use the information resulting from this study to make management decisions on the operation of gates and control structures. The information will also be useful to the USAGE and Miami-Dade County Environmental Resources Management (DERM) for their evaluation of the ecological conditions of Biscayne Bay. Other ECO studies that include sheetflow, ground-water flow, and estuarine flow modeling can benefit from the results of this study by using model output for initial and boundary conditions.

Project objectives and strategy:
The objectives of this project are to: (1) define the hydrogeologic characteristics of the surficial aquifer system adjacent to and beneath Biscayne Bay, (2) estimate ground-water flow and the saltwater interface location using the USGS three-dimensional finite-difference heat and solute transport model (HST3D) (Kipp, 1987,1996). and (3) assess the potential effects of some of the changes in water management being proposed for Everglades restoration.

The strategy to achieve these objectives is to analyze existing data, collect new data, and use a ground-water model to access existing and future effects of water management operations.

Potential impacts and major products:
A final report (Water Resources Investigations Report) will include the numerical model output focusing on an evaluation of the effects of water management activities on ground-water flow to the bay. A synoptic synthesis report (fact sheet) will be produced to help educate the public and clients regarding the relationship between man-made fluctuations in surface water and the discharge of ground-water to Biscayne Bay.

This project will answer the following questions: (1) Is ground-water that is flowing to Biscayne Bay a significant component of the water budget in southern Florida? (2) Would the quantity of ground-water flowing to Biscayne Bay be affected by changes in the operation of gates and control structures in canals? and (3) How much change in ground-water discharge to Biscayne Bay has occurred due to present modifications to the hydrologic system? An additional benefit would be to see how the saltwater interface reacts to fluctuations in canal stages.

Collaborators, clients:
Clients include the USAGE, SFWMD, DERM, and other ecosystem research project chiefs. The clients need estimates of ground-water discharge to Biscayne Bay and an assessment of the effects of water management activities on ground-water discharges to the bay.

WORK PLAN
Time line (FY 1999 to project end):
 

Task	Time line	Who
Data Collection	October ó December	David Schmerge, John Passehl
Data Analysis	Ongoing	David Schmerge
Computer Model Runs	Ongoing	John Passehl, Vicente Quinones
Model Calibration	November ó January	John Passehl
Model Sensitivity	January	John Passehl
First Draft of Final Report	February	John Passehl, Kim Swidarski
Revisions of Report	March ó July	John Passehl. Kim Swidarski

 

FY 1999 activities:
Continue collection and interpretation of hydrogeologic data to be used in the model. Continue operation and data processing of three pressure transducers (three offshore wells and three onshore wells). Compilation of data for model (using GIS). Complete construction and calibration of variable-density ground-water flow model. Provide estimates of ground-water discharge to the bay using the model and access the effects of different water management scenarios on ground-water discharge to the bay. Finish writing final report.

FY 1999 deliverables/products:
A synthesis fact sheet will be produced to serve as an outreach tool to the clients and public. A final report (Water Resources Investigations Report) will include the numerical model analysis focusing on the water balance and an evaluation of the effects of management activities on ground-water flow to the bay.

FY 1999 outreach:
A public meeting will be held with the clients explaining the findings to date of the project. These findings may be reported at other meetings as deemed appropriate. New posters will be produced to help educate the public and clients regarding the relationship between man-made fluctuations in surface water and the discharge of ground-water to Biscayne Bay.

New directions or major changes for FY 1999:
At the request of several clients, the model domain was extended north from the C-6 canal to the C-9 canal and was extended south from the C-103 canal to the C-111 canal. The extended model domain will require more model setup and computing time and possibly more data collection.

ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH
FY 1998 accomplishments and outcomes, including outreach:
Permits were obtained for onshore monitor well drilling. Twelve onshore wells were drilled (Between June 1 and December 1), by the Florida Geological Survey for water level/quality sampling. The wells continue the 3 offshore transects with three wells per transect and are within 0.5 kilometers of the bay. Each site consists of three wells, one shallow (30 to 40 feet into the limestone), one intermediate (50 to 60 feet into the limestone), and one deep (90 to 100 feet into the limestone).

Water samples are being collected once monthly (onshore and offshore wells) for major water quality parameters such as conductance, salinity, and chlorides as well as temperature.

Three onshore pressure transducers (one at each transect) were installed and are continuously recording water levels and temperatures. At the north transect, three offshore pressure transducers were installed and are continuously recording pressures at the wellheads. At the south transect, four submersible temperature recorders were installed and are continuously recording aquifer and bay temperatures.

Variable density 2D cross-sectional models were completed for the central and south transects for the purposes of optimizing grid arrays for the 3D model and obtaining crude estimates of ground-water flux to the bay.

A meeting was held to present the results to date of the project to the USACE, SFWMD, DERM, and Biscayne National Park.

FY 1998 deliverables, products completed:
Two posters that describe the hydrology, offshore well drilling techniques, and conceptual model of the model area were presented at the annual USGS-SFWMD conference, the project meeting, and at other meetings and outreach presentations.

PROJECT SUPPORT REQUIREMENTS
Names and expertise of key project staff:
 

John Passehl	Hydrologist	Data collection, analysis, model development
Vicente Quinones	Hydrologist	Consultation on model development and calibration
David Schmerge	Hydrologist	Data collection and analysis
Kim Swidarski	Scient. Ill.	Report graphics

Other required expertise for which no individual has been identified:
None

Major equipment/facility needs:
None

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