evaluation of methods to determine groundwater seepage beneath levee 30 >
Evaluation of Methods to Determine Groundwater Seepage Beneath Levee 30, Miami-Dade County, Florida
Project Proposal for 1999
(Barbara Howie, Project Officer)
Program(s): Intergrade Natural Sciences Program
Program element(s)/task(s): South Florida, Element 3: Modeling and Support Studies for Southern Inland Coastal Systems of Eastern Dade County and Biscayne Bay,
Task 3.5: Ground-water Seepage Beneath the Protective Levee.
Project summary: The accounting of all significant hydrologic inflows and outflows to the Everglades ecosystem of the south Florida mainland is a key element of the South Florida Ecosystem Program. The amount of water seeping under the protective levee system between the Everglades National Park and the urban and agricultural area to the east is poorly estimated. The objective of this project is to evaluate methods of determining ground-water seepage beneath Levee 30 and Levee 31N. Plans to restore historical hydrologic conditions in the northeast section of ENP include the raising of water levels in ENP and WCA 3B which overlie the Biscayne aquifer, an extremely permeable aquifer. The increase in water levels is likely to cause an increase in seepage losses to the east under Levee 30 and Levee 31N. Water supply for the urban areas to the east is dependent on well fields in these areas. Application of real time data to a model and development of empirical relationships between groundwater levels, stages in WCA 3B and ENP, canal stages, and seepage will improve management of water resources in the area, including pumping at the West Well Field near Levee 31N and the Northwest Well Field near Levee 30.
Project objectives and strategy: The objective of this project is to evaluate methods for quantifying ground-water seepage beneath the protective levee and analyze these methods with respect to data requirements and computational effort. The use of different ground-water models will be evaluated and empirical relationships between field data and ground-water seepage will be developed, where possible. The data needs to determine the empirical relationships will be evaluated. Accurate seepage data will enhance the accuracy of models of the Everglades and coastal systems.
The study area for this 5-year effort (FY95 to FY99) is limited to a 3-mile reach of Levee 30 in north-central Dade County and a 7-mile reach of Levee 31N in central Dade County. Hydrologic and geologic data will be collected and utilized in the development and calibration of ground-water flow models to determine seepage rates beneath Levee 30 and Levee 31N. Data collection will include ground-water levels, surface-water stages, canal discharges, vertical infiltration rates, and geologic cores. Oxygen isotope data will be used as a tracer at the Levee 31N study site. The models will include flow nets, and cross sectional and three dimensional numerical models that will be developed using the USGS MODELOW code. Empirical relationships will be developed using the results of the ground-water flow models to determine the data needs to provide real time seepage data to the regulatory and management agencies. The results for each study site will be published in a separate water resources investigation report.
Potential impacts and major products: Ecosystem Restoration involves delivering more water to the Everglades and Taylor Slough. One alternative under consideration is the use of buffer zones between the wetlands to the west and the urban areas to the east to step down water levels. Other alternatives include impoundment of water in surface impoundments. This project will help answer two relevant questions: If water levels are raised west of the protective levee how much water will make its way south to Everglades National Park and Taylor Slough and how much will be lost to seepage due to the increased groundwater gradient? What effect will the Lake Belt and Buffer Zones have on seepage? The project will provide estimates of seepage in the vicinity of a gaining canal (L-30 Canal) and a losing canal (L-31N Canal). It will also provide information on the source of water to the West Well Field: the Everglades, L31 Canal or local precipitation. For each site the products include a report (WRIR) describing the work and results, estimates of seepage, and numerical models.
Collaborators, clients: Clients include four regulatory/management
agencies, the U.S. Army Corps of Engineers (COE), the South Florida Water
Management District (SFWMD), Everglades National Park (ENP). and Miami-Dade
County Department of Environmental Resources Management (DERM), and one
utility, Miami-Dade Water and Sewer Department (MDWASD). Models developed
through this project are needed to estimate the effects of changing water
levels in Water Conservation Area 3B (WCA 3B) and of well field pumping
on ENP. The results of the study will be used by the South Florida Water
Management District as part of the Lake Belt study in Miami-Dade County.
The results of the study will also be used by DERM and MDWASD in the management
of two well fields, the Northwest Well Field. east of Levee 30, and the
West Well Field, east of Levee 31N.
Deliverables: Two Water Resources Investigation Reports are planned which will document the results of the study. The first report will be ready for colleague review by August, 1998 and will be available for distribution by the end of 1998. The second report will be ready for colleague review by April 1999 and will be available for distribution by the end of September 1999. Both reports will include descriptions of the data collection and the models developed.
FY 1999 deliverables/products: For each site the products include a report (WRIR) describing the work and results, estimates of seepage, and numerical models.
FY 1999 Outreach: Data will be made available to SFWMD, COE and
Dade County, when requested, for their modeling and management needs. Data
will be available in the USGS NWIS data base and via the internet. Committee
meetings will be attended and preliminary results will be discussed prior
to approval of the final reports. Other outreach activities include presentation
of research results at USGS sponsored conferences and at conferences and
seminars sponsored by other scientific organizations.
ACCOMPLISHMENTS, OUTCOMES, PRODUCTS, OUTREACH
Accomplishments and Outcomes, Including Outreach: A 3D model has been developed for the Levee 30 site using the USGS MODFLOW package. A draft of the WRIR is currently in review for this site. Initial results of work on Levee 31N support the hypothesis of a deep groundwater circulation pattern beneath Levee 31N which serves to transport water from the Everglades toward urban areas. This flow pattern may be facilitated by lithologic layering within the Biscayne aquifer. These preliminary results for the Levee 31N site were presented at a meeting of the Miami Geological Society in Miami, Florida on May 13, 1998. Interested parties were invited to attend. Results were also presented as a poster at the national conference of the American Geophysical Union in Boston. Massachusetts on May 27, 1998.
FY 1998 deliverables, Products completed: A presentation on the
work at L31N was delivered at the May 13, 1998 meeting of the Miami Geological
Society. A poster presentation was delivered May 27, 1998 at the national
conference of the American Geophysical Union in Boston. Massachusetts.
The abstract of the paper was published in the conference proceedings.
The citation is: Solo-Gabriele, H.M., Steinberg, L., Ibler, G., and Nemeth.
M., 1998. A Seepage Study of the East Everglades. Abstracts of the 1998
Spring Meeting of the American Geophysical Union, Boston, Massachusetts,
EOS Supplement, April 28, 1998. p. S93.
Products Completed: A poster was presented on the L-31N study at the American Geophysical Union Meeting in Boston (May 26-29) and an abstract published in the proceedings.
New Directions, Expansion of Continuing Project: None Planned
PROJECT SUPPORT REQUIREMENTS:
Names and expertise: Dr. Helena Solo-Gabriele, Senior Modeler
(Faculty Appointment) Mark Nemeth, Assistant Modeler, (University of Miami,