OFR 2004-1097

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Langevin, Christian D., Swain, Eric D., and Wolfert, Melinda A., 2004, Simulation of Integrated Surface-Water/Ground-Water Flow and Salinity for a Coastal Wetland and Adjacent Estuary, U.S. Geological Survey Open-File Report 2004-1097, 30 p.


The SWIFT2D surface-water flow and transport code, which solves the St. Venant equations in two dimensions, was coupled with the SEAWAT variable-density ground-water code to represent hydrologic processes in coastal wetlands and adjacent estuaries. The integrated code was applied to the southern Everglades of Florida to quantify flow and salinity patterns and to evaluate effects of hydrologic processes. Results indicate that most surface water within Taylor Slough flows through Joe Bay and into Florida Bay through Trout Creek. Overtopping of the Buttonwood Embankment, a narrow but continuous ridge that separates the coastal wetlands from Florida Bay, does occur in response to tropical storms, but the net overflow is only 1.5 percent of creek discharge. The net leakage rate for the coastal wetland is about zero with nearly equal upward (17.1 cm/yr) and downward (17.4 cm/yr) rates. During the dry season, the coastal wetland increases in salinity to 30-35 practical salinity units but is flushed each year with the onset of the wet season. Model results demonstrate that surface-water/ground-water interactions, density-dependent flow, and wind affect flow and salinity patterns.


1. Introduction
2. Governing Equations

2.1 Surface-Water Flow and Solute Transport
2.2 Ground-Water Flow and Solute Transport
2.3 Surface-Water/Ground-Water Interactions
3. Numerical Implementation
3.1 Coupling Procedure
3.2 Leakage Calculation
3.3 Surface/Subsurface Solute Exchange
3.4 Spatially Distributed Rainfall and Evapotranspiration
3.5 Rewetting
4. Application of Integrated Model to the Southern Florida Everglades
4.1 Description of Study Area
4.2 Model Design
4.3 Model Calibration and Analysis of Simulation Results
4.3.1 Surface-Water Flow Patterns
4.3.2 Discharge to Florida Bay and Surface-Water/Ground-Water Interactions
4.3.3 Coastal Salinities
4.4 Effects of Selected Hydrologic Processes
5. Discussion
6. Summary and Conclusions
References Cited

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