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Project Summary Sheet

U.S Geological Survey, South Florida Ecosystem Program: Place-Based Studies

Project: Quantification of Ground-Water Seepage Beneath Levee 31N, Miami-Dade County, Florida

Web Site: http://sflwww.er.usgs.gov/projects/levee_31/; http://sflwww.er.usgs.gov/metadata/sflwww/solomet.html; http://www.eng.miami.edu/~hmsolo/L31/L31frames.html

Location: Southeast Coast; Miami-Dade County

Principal Investigators: Helena Solo-Gabriele, 305.284.3489; Barbara Howie, bhowie@usgs.gov, 305.717.5811

Project Personnel: Mark Nemeth, MNemeth@us.usbr.gov, Walter Wilcox, wwilcox@sfwmd.gov

Other Supporting Organizations: None

Associated Projects: Use of stable isotopes to trace the movement of water within the L-31N region (Helena Solo Gabriele)

Overview & Status: A coupled ground- and surface-water model (MODBRANCH) was developed to estimate ground-water flow beneath Levee 31N in Miami-Dade County, Florida, and to simulate the hydrologic conditions in the surrounding area. The study included compilation of data from monitoring stations, measurement of vertical seepage rates in wetlands, and analysis of the hydrogeologic properties of the ground-water aquifer within the study area. In addition, the MODBRANCH code was modified to calculate the exchange between surface-water channels and ground water using a relation based on the concept of reach transmissivity. Seepage meters were used to quantify vertical seepage rates in the Everglades wetlands area west of Levee 31N. A comparison between results from the seepage meters and from the computer model indicated substantial differences that seemed to be a result of local variations in the hydraulic properties in the topmost part of the Biscayne aquifer. The modified reach-transmissivity version of the MODBRANCH model was judged to have performed satisfactorily and offered considerable advantages over the use of the original formulation. This computer model was employed to simulate seepage of groundwater beneath Levee 31N. Modeled seepage rates were usually between 100 and 400 cubic feet per day per foot of levee, but extreme values ranged from about -200 to 500 cubic feet per day (positive values indicate eastward seepage beneath the levee). The modeled seepage results were used to develop an algorithm to estimate seepage based on head differential at selected monitoring stations. The algorithm was determined to adequately predict ground-water seepage.

Needs & Products: Subsurface flows beneath Levee 31N, a 7-mile portion of the Everglades perimeter system, is considered a major outflow component of the Everglades water budget as well as an important inflow component to the urban aquifer system. Levee 31N is the eastern border of northeastern Everglades National Park, a region that currently suffers from inadequate water deliveries. Restoration efforts in this area will focus on changing current water levels. This project has been approved for publication as USGS Water-Resources Investigations Report 00-4066. A manuscript from this project is currently in preparation and will be submitted shortly to a peer-reviewed journal.

Application to Everglades Restoration: The model developed through this study can be used to estimate the effect of water-level changes on subsurface seepage beneath L-31N, and water deliveries to the area can be adjusted based on estimates of seepage losses.

Study Milestones

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Design

 

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Field Work

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Data Analysis

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Initial Reporting

       

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Results Published

       

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Synthesis

           

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Note: "x" indicates task completed, and "o" indicates task planned, but not completed


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Last updated: 24 April, 2014 @ 12:00 PM (KP)