discharge to biscayne bay >
Program: Fragile Environments
Program: Fragile Environments
Project Summary: Management agencies need to know the effect that 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 a model assessment of effects of management activities on discharge to bay. Needed for Everglades Ecosystem hydrologic assessment.
Project Justification: Changes in the operation of gages and control structures in canals will be required as part of the effort for the restoration of the Everglades Ecosystem. These changes will modify the water-level altitude in the water conservation areas (WCA's) and flow conditions in canals. The modification of water-level altitude in the WCA's and flow conditions in the canals can lead to changes in the rate of ground water flowing through the surficial aquifer system and discharging to Biscayne Bay. These operational changes lead to the following questions:
1. Is ground water flowing to Biscayne Bay a significant component of the water budget in southern Florida?
Project Objectives: The objectives of this study are to: 1) define the geohydrologic characteristics of the surficial aquifer system in parts of Biscayne Bay, 2) apply numerical modeling techniques to estimate ground-water discharges to the bay, and 3) assess the potential effects of some water management operations in canal and water conservation areas on the rates of ground-water discharges to the bay.
Overall Strategy, Study Design, and Planned Major Products: Define hydrogeologic characteristics of the surficial aquifer in the area along the shoreline. Use geochemical data to help with the definition of the flow characteristics. Ground-water flow sectional and areal models will be used to estimate discharge to the Bay and the effects of some water management practices on the amount of ground-water discharge. A final report (Water Resources Investigations Report) will include the numerical model analysis focusing on an evaluation of the effects of management activities on ground-water flow to the bay.
Overall: The work elements of this project include: (1) drilling and construction of nearshore and offshore wells, and analysis of core samples to define the hydrogeologic conditions along the west side of Biscayne Bay, (2) construction of three sectional ground-water flow models, (3) defining the saltwater-freshwater mixing zone, (4) estimating ground-water flow to Biscayne Bay, and (5) construction of an areal ground-water flow model to determine the effect of changes in water- management activities on ground-water discharge to Biscayne Bay. Data collected during this project will include core samples collected during drilling of nearshore and offshore wells, and water-level, geochemical, chloride, and specific conductance data from the finished nearshore and offshore wells. Geologic columns developed from the analysis of core data and other data collected will be stored in the Ground Water Site Inventory (GWSI) data base. The model will be archived in the USGS model archive in the Miami office computer.
Planned Deliverables/Products: A fact sheet is planned which will briefly describe the sectional models and provide a preliminary estimate of ground-water discharge to the Bay. A final water resources investigation report is planned which will describe the construction, calibration, and application of an areal model to estimate ground-water discharges to the Bay and the possible effect of management practices on the discharges to the Bay.
Planned Outreach Activities: Data will be available for the clients and cooperators when requested by them. All efforts are coordinated and reported to the U.S. Army Corps of Engineers, Dade County Department of Environmental Resources Management, and Biscayne National Park.
New Directions, Expansion of Continuing Project (if applicable): Three sectional models are now included as part of the approach. The sectional models will be useful in determining the hydraulic and mixing characteristics in the fresh/saltwater interface. These models will aid in the design of the areal model and will provide an estimate of ground-water discharges to the Bay early in the project. Oxygen-18 and deuterium stable isotopes will be used to investigate the source of ground water discharging to the canal.
Accomplishments and Outcomes, Including Outreach: Permits for drilling at two of the six nearshore drilling sites were obtained. Permits for the other four sites are being processed. Surface time domain electromagnetic (TDM) surveys were run along the onland part of the three transects. These TDM surveys were useful in defining the saltwater/freshwater mixing zone. Preliminary analysis of oxygen-18 and deuterium stable isotopes suggests that: ground water is discharging offshore along the Coconut Grove transect (north transect); water of canal origin represent a significant part of the ground water discharging along the Cutler transect (central transect); and an insignificant amount of ground water is discharging along the Mowry Canal transect (south transect). Nutrient data collected in collaboration with FIU faculty and graduate students seems to be useful in confirming the isotope analysis.
Deliverables, Products Completed: An abstract for the 1997 annual meeting is in review.
Names of Key Project Staff:
Major Equipment/Facility Needs: Hermit data loggers and pressure transducers.