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geer > 2000 > poster > ground water and surface water interactions in the freshwater wetlands of taylor slough

Ground Water and Surface Water Interactions in the Freshwater Wetlands of Taylor Slough

Poster presented December 2000, at the Greater Everglades Ecosystem Restoration Conference

Judson W. Harvey1, Jungyill Choi1, and Robert H. Mooney2
1- USGS, 430 National Center, Reston, VA, 20192; 2-USGS, Miami, Fl

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Problem and Approach | Surface-Water Tracer of Groundwater Interactions |
Source and Quantity of Groundwater Discharge | Conclusion

Problem and Approach

Site Location Map
Illustrated Site Location Map
Key to Illustrated Site Location Map
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Site Description

Taylor Slough is one of two well-defined flow-ways for surface water in Everglades National Park. It is separated from Shark Slough by a series of low-lying coastal ridges referred to as Long Pine Key, and by an area of relatively high-elevation wetlands called the Rocky Glades. Historically, Taylor Slough received water from precipitation, surface overflow from Shark Slough, and possibly as ground-water discharge from the coastal ridge systems. Presently, Taylor Slough receives much of its water from the L31-W canal at the S332 pumping structure (at what is effectively the northern terminus of Taylor Slough), and from outflow at the southern end of the L31-W canal.

The organic wetland peat in Taylor Slough varies in depth (0.2 - 2 m) and in the content of calcitic mud. Under the peat is a highly permeable sand and limestone aquifer (Biscayne aquifer).


Area of Study
Aerial photograph of study area
SFWMD photo
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Aerial photograph of study area
SFWMD photo
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Illustrated map of study area
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Problem

Determining wetland and groundwater interactions in Taylor Slough is important because the balance of freshwater flow in the lower part of the Slough is uncertain. Flows through Taylor Slough are relatively small in comparison with Shark Slough, but they are especially important to the ecology of estuarine mangrove embayments of northeastern Florida Bay. Improved estimates of wetland and ground-water interactions are also needed to better understand biogeochemical processes that affect water quality in lower Taylor Slough and in northeastern Florida Bay.

Research Approach

Two approaches were used to investigate wetland and ground-water interactions in Taylor Slough. One method was to compute ground-water discharge using chloride as an environmental tracer. Estimates of precipitation, evapotranspiration, and surface-flow velocity were needed in addition to chloride measurements in surface water and in ground water. We also estimated ground-water discharge by combining estimates of hydraulic conductivity in the peat (determined by the piezometer slug test method) with measurements of vertical hydraulic gradient. Vertical discharge from the peat was computed from those data using Darcy's law.

The research was conducted during seven primary measurement periods between September 1997 and September 1999. Our results are discussed with reference to four segments (referred to as reaches) that comprise Taylor Slough the freshwater portion of Taylor Slough.

Analysis Equations
Illustration showing relationship between parameters

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Considering Precipitation and ET only
Q*2 = Q1 + PPT x TT - ET x TT
Cl*2 = Cl1 x Q1 + (PPT x TT) x ClP

Q*2
Considering Precipitation, ET, and GW inflow
Q*2 = Q1 + PPT x TT - ET x TT + GWin x TT
Cl*2 = Cl1 x Q1 + (PPT x ClP + GWin x ClGW) x TT

Q*2
Assumptions:
  • Steady-state hydrologic condition
  • Only inflow is groundwater discharge with
    substantially different chloride concentration



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Related information:

SOFIA Project: Groundwater-Surface Water Interactions and Relation to Water Quality in the Everglades


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