projects > a coupled surface water and ground-water model to simulate hydrologic conditions in DOI managed lands > work plan
Project Work Plan
Department of Interior USGS GE PES and ENP CESI
Fiscal Year 2007 Study Work Plan
Study Title: A Coupled Surface Water and Ground-Water Model to Simulate Past, Present, and Future Hydrologic Conditions in DOI Managed Lands
Overview & Objectives: The Comprehensive Everglades Restoration Plan (CERP) aims to reestablish predevelopment natural flows in the Everglades system and surrounding areas including Biscayne Bay. The changes proposed within this plan may cause significant alterations to the hydrologic conditions that exist in both Everglades National Park (ENP) and Biscayne National Park (BNP). System-wide, there are water management, water supply, and environmental concerns regarding the impact of wetland restoration on groundwater flow between the ENP and BNP and along the L-31 and C-111 canals. For example, restoration of wetlands may lead to increases in coastal ground-water levels and cause offshore springs in Biscayne Bay to become reestablished as a significant site of freshwater discharge in BNP. Accordingly, the CERP restoration activities may increase the rate of coastal groundwater discharge and aid transport of anthropogenic contaminants into the offshore marine ecosystem. Under this scenario, there is significant potential for habitat deterioration of many different threatened or endangered species of plants and animals that reside along the coastline of Biscayne Bay, in the Bay, or on the coral reef tract. In contrast to a surface water system which has been extensively compartmentalized and channelized, the Biscayne aquifer which flows under both ENP and BNP is continuous and not as amenable to partial domain simulation. A comprehensive model is needed to reliably and credibly assess the effects of groundwater flow and transport on both parks. Hydrologic conditions should be evaluated prior to substantial water delivery changes in order to protect these sensitive ecosystems. A numerical model that can simulate salinity and surface and ground-water flow patterns under different hydrologic conditions is an essential part of this effort.
The USGS developed a coupled surface-water/ground-water numerical code known as the Flow and Transport in a Linked Overland/Aquifer Density-Dependent System (FTLOADDS) to represent the surface water and ground-water hydrologic conditions in south Florida, specifically in the Everglades. The FTLOADDS code combines the two-dimensional hydrodynamic surface-water model SWIFT2D to simulate variable density overland flow (Schaffranek, 2004; Swain, 2005), the three-dimensional ground-water model SEAWAT to simulate fully-saturated variable-density groundwater flow (Guo and Langevin, 2002), and accounts for leakage and salt flux between the surface water and ground water (Langevin and others, 2005). The code was then applied to two major testing regions: 1) the Southern Inland and Coastal Systems (SICS) model domain (Swain and others, 2004) and 2) the Tides and Inflows in the Mangroves of the Everglades (TIME) model domain. The first application used code versions 1.0 and 1.1 which only utilized the SWIFT2D surface-water code. Later applications in the SICS area used version 2.1 (Langevin and others, 2005) where SWIFT2D was coupled to the SEAWAT groundwater model code. The second domain, TIME (Wang and others, 2007), utilizes the enhanced version 2.2 code, which includes enhancements to the wetting and drying routines, changes to the frictional resistance terms applications, and calculations of evapotranspiration. In 2006, FTLOADDS was modified again to represent Biscayne Bay and surrounding areas. The first objective of this project is to update and reconfigure the FTLOADDS modeling code to include all version modifications and enhancements in order to provide an easier transition for the coupling of models.
The second and principal objective of this project is to develop a comprehensive model by utilizing the established USGS TIME model application of the southern Everglades and linking it to a coupled surface and ground water model application of Biscayne Bay that is currently in development. This will provide one large sub-regional model that will give an integrated comprehensive assessment of how different scenarios will affect water flows in both Everglades National Park and Biscayne National Park. Once calibrated, additional simulations will be performed to estimate predevelopment hydrologic conditions and to predict hydrologic conditions under one or more of the proposed restoration alternatives, using inputs from the Natural Systems Model (NSM) (SFWMD, 1997A) and the South Florida Water Management Model (SFWMM) (MacVicar and others, 1984, SFWMD, 1997B.
Specific Relevance to Major Unanswered Questions and Information Needs Identified: Currently the TIME model is providing needed hydrologic data to the Florida Bay Florida Keys Feasibility Study (FBFKFS). When TIME is linked with the new model of Biscayne Bay, it will provide more detailed information in the northeastern portion of Florida Bay as well as exchange to the eastern metropolitan area. The large model will also provide inputs of freshwater flows and salinities that can be used for the CSOP evaluation as well as providing a linkage to the SFWMM model to estimate effects of restoration efforts on the C-111 spreader canal area. The model also provides estimates of overland flows within ENP, which can be used to evaluate the affects of the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project. When the model is linked to the NSM it will provide an estimate of pre-drainage conditions in both Biscayne National Park and Everglades National Park and display how the two systems interact. This will give needed hydrologic conditions, both in the surface water and groundwater, and salinity data needed for the Biscayne Bay Coastal Wetlands project and the Landscape-Scale Science Needed to Support Multiple CERP Projects. It will also provide water supply estimates to each park to mimic pre-drainage conditions for the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study. Additionally the model will provide insight into the impact of the Lakebelt In-Ground Reservoir Technology Pilot Project on groundwater flows and help determine the effects on hydropatterns and water levels in Shark Slough for the L31N Seepage Management Project.
This study supports the Biscayne Bay Coastal Wetlands project (BBCW; p. 82) as it will provide a model that can better define the surface water and ground-water hydrologic patterns in BNP and the surrounding areas. Once the model is linked with the NSM it will also be able to provide a potential pre-drainage estimate of the hydrologic conditions in the area. Additionally, the model will provide baseline data on the current and pre-drainage salinity in Biscayne Bay and likely salinity effects due to the different CERP restoration scenarios.
This study supports the L-31N/L30 Seepage Management Pilot project and Everglades National Park Seepage Management project (L-31N/L-30N SMPP and ENP SM p. 54) as it will provide a model that can supply data on past, present and future hydropatterns in northeastern Shark Slough. It will also be able to provide estimates on the effects of the seepage control on ground-water flows in the surficial aquifer and how the modifications will affect the flows between ENP and BNP.
This study supports the Combined Structural and Operational Plan (CSOP), Including the C111 Spreader Canal Project (p. 80) as it will provide a calibrated model that can be used to predict salinities in the coastal mangrove fringe and northeastern Florida Bay. It will also be able to provide data on the amount of freshwater flow that reaches the coast under the different restoration scenarios, and potentially define pre-drainage hydrologic conditions in the area. When linked with the SFWMM model, it will provide an estimate of the effects of the restoration scenarios upon the C-111 spreader canal area.
This study supports the Additional Water for Everglades National Park and Biscayne Bay Feasibility Study (p. 84) as it provides a model that can supply a baseline estimate of ENP and BNP pre-drainage conditions, so water mangers can estimate the amount of water needed to successfully restore the system.
This study supports the Florida Bay and Florida Keys Feasibility Study (p. 87) as it provides a model that can produce estimated freshwater flows and salinities to the bay, in the past, present, and future under different CERP scenarios. The model can supply baseline information that can be used to determine the extent of the effects to the hydrology of the system due to the different restoration alternatives.
This study supports the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project (DECOMP; p. 76) as it will provide a model that can be utilized to identify areas that are affected by these changes and determine the potential extent of change in sheetflow into Everglades National Park. Additionally, it will provide needed hydrologic input for ecologic models that assess the effects of the modifications in sheetflow on the ecosystem.
This study supports the Lake Belt In-Ground Reservoir Technology project (p. 51) as it provides a model that can be used to determine the effectiveness of proposed seepage barriers associated with the construction of CERP Lake Belt reservoirs, under different restoration scenarios.
This study supports Landscape-Scale Science Needed to Support Multiple CERP Projects (p. 92) as it will provide a coupled surface water and ground-water model that can provide information on past, present, and future flows between Everglades National Park, Biscayne Bay and Florida Bay.
Status: New project starting in FY07
Recent Products: None.
Planned Products: The current planned products include; an updated version of the FTLOADDS modeling code, a calibrated model that can be used by managers to evaluate different restoration scenarios, presentations on the model results, and an USGS Scientific Investigations Report or journal article.
Guo, Weixing, and Langevin, C.D., 2002, User's guide to SEAWAT: A computer program for simulation of three-dimensional variable-density ground-water flow: U.S. Geological Survey Techniques of Water-Resources Investigations, book 6, chap. A7, 77 p.
Langevin, C.D., Swain, E.D., and Wolfert, M.A., 2005, Simulation of integrated surface-water/ground-water flow and salinity for a coastal wetland and adjacent estuary: Journal of Hydrology 314, 212-234.
MacVicar, T.K., VanLent, Thomas, and Castro, Alvin, 1984, South Florida Water Management Model documentation report: South Florida Water Management District Technical Publication 84-3, 123 p.
Schaffranek, R.W., 2004, Simulation of surface-water integrated flow and transport in two dimensions: SWIFT2D user's manual: U.S. Geological Survey Techniques and Methods, book 6, chap. B-1, 115 p.
South Florida Water Management District, 1997A, Natural System Model (NSM) Version 4.5, Online Documentation: Hydrologic Systems Modeling Department, Water Supply Division, SFWMD, West Palm Beach, Florida. http://www.sfwmd.gov/org/pld/hsm/models/nsm/nsm45doc/nsm45.htm
South Florida Water Management District, 1997B, DRAFT Documentation for the South Florida Water Management Model: Hydrologic Systems Modeling Department, Water Supply Division, South Florida Water Management District, West Palm Beach, Florida, accessed at http://www.sfwmd.gov/org/pld/hsm/models/sfwmm/v3.5/wmmpdf.htm
Swain, E.D., 2005, A model for simulation of Surface-Water Integrated Flow and Transport in Two Dimensions: User's guide for application to coastal wetlands: U.S. Geological Survey Open-File Report 2005-1033, 88 p.
Swain, E.D., Wolfert, M.A., Bales, J.D., and Goodwin, C.R., 2004, Two-dimensional hydrodynamic simulation of surface-water flow and transport to Florida Bay through the Southern Inland and Coastal Systems (SICS): U.S. Geological Survey Water-Resources Investigations Report 03-4287, 56 p., 6 pls.
Wang, J. D., Swain, E. D., Wolfert, M. A., Langevin, C. D., James, D. E., and Telis, P. A., 2007, Application of Flow and Transport in a Linked Overland/Aquifer Density-Dependent System (FTLOADDS) to Simulate Flow, Salinity, and Surface-Water Stage in the Southern Everglades, Florida: U.S. Geological Survey Scientific Investigations Report 2007-5010, 121 p.
Title of Task 1: Update FTLOADDS modeling code
Task Summary and Objectives: One of the major functions of the FTLOADDS shell is to handle the interactions between the surface water SWIFT2D code and the ground water SEAWAT code. Currently this code is being used in several modeling projects that had separate and unique issues. Accordingly, the code was modified to satisfy those specific problems. This had the collateral effect of producing divergent versions of the code and hard coded algorithms designed for site-specific applications. In order to link the TIME and Biscayne areas together, the code must be modified to handle the problems in a universal manner. The main objective of this task is to update the FTLOADDS modeling code into a version that is portable, can be readily applied in different areas, and allows site specific characteristics to be incorporated through input options as opposed to code modifications.
Work to be undertaken during the proposal year and a description of the methods and procedures: The first steps to be taken are to replace the application-specific coding in the code with user-input options and implement methods to allow the model to be more user-friendly and portable. The code needs to be updated to accept the latest version of the SEAWAT and MODFLOW codes. This will require substantial changes because of recent changes in how SEAWAT stores and accesses variables. The existing interface code, for example, to calculate the leakage across the soil surface will be transferred to the new model and new code added to take advantage of the enhanced capabilities contained in the latest version of SEAWAT. Benchmark testing will be performed to insure the updated code is operational and reliable.
Specific Task Products: Updated version of the FTLOADDS code.
Title of Task 2: Couple TIME and BISCAYNE BAY models
Task Summary and Objectives: In order to develop a comprehensive model of South Florida, the pre-existing USGS TIME model for the southern Everglades will be utilized and linked to a coupled surface and ground water model of Biscayne Bay. The L-31N/C-111 canal system delimits the boundary between these two systems and the linkage will account for flux that occurs across this boundary under various restoration scenarios. One large area model will offer an integrated comprehensive assessment of the manner in which different scenarios may affect surface and shallow ground-water flow in both Everglades National Park and Biscayne National Park. The main objective of this task is to combine the newly developed FTLOADDS model application to Biscayne Bay with the existing FTLOADDS TIME model application.
Work to be undertaken during the proposal year and a description of the methods and procedures: This task will merge the TIME and Biscayne Bay model discretizations and eliminate all interior boundary conditions, such as along the C-111 and L-31N Canals. Equations that can calculate leakage from the groundwater into the canals and from the canals to the groundwater will be added to the model. These equations will use simulated stage or the canal leakage that is provided by the SFWMM model simulations. This is necessary as the TIME model uses canals as hydrologic boundaries, but when the models are linked these canals will become interior features and a process to calculate their effects is needed. Currently, the TIME model uses 10 vertical layers; it needs to be modified to conform to the 20 layer-Biscayne Bay model. Extensive testing of the full model will be performed and calibrated using stage, flow, and salinity observations. Model performance will be evaluated by comparing simulations to those obtained with the two smaller models.
Specific Task Product(s): Coupled Biscayne and TIME model
Title of Task 3: Link coupled model with the South Florida Water Management Model (SFWMM).
Task Summary and Objectives: In order to evaluate the different effects that the CERP restoration efforts may have upon both Everglades and Biscayne Bay National Parks, the coupled TIME/Biscayne Bay model should be linked with the South Florida Water Management Model (SFWMM). The principal objective of this task is to link the coupled TIME/Biscayne Bay model with the SFWMM model and simulate present and predict future hydrologic conditions under selected CERP restoration scenarios.
Work to be undertaken during the proposal year and a description of the methods and procedures: An approach similar to methods used to link the SICS model to the SFWMM (Wolfert, 2004) will be applied to link the models. Boundary input locations in the TIME/Biscayne Bay model are correlated with the SFWMM cell values. Boundary data of the models will be acquired from the SFWMM model for the simulation period of 1990-2000. This period was chosen with the TIME application to represent a series of consecutive years of varied hydrologic conditions useful to evaluate ecosystem and biological performance measures in ENP. Since most of the input data have already been assembled for this period, it is more cost efficient to run Biscayne Bay and the full ENP/BNP model simulations for the same period.
Specific Task Products: Presentations on the results of the linked model.
Title of Task 4: Link coupled model with the South Florida Natural Systems Model (NSM).
Task Summary and Objectives: Understanding pre-development environmental conditions and their hydrologic behavior is important to assessing the impact of restoration efforts. All anthropogenic features will be removed from the model to hindcast flow conditions. This task will be accomplished by linking the TIME/Biscayne Bay model to the SFWMD's Natural Systems Model (NSM) and simulate predevelopment conditions.
Work to be undertaken during the proposal year and a description of the methods and procedures: Several modifications are required to link the TIME/Biscayne Bay model with the NSM model. Land use and land surface elevations will be modified to match predevelopment conditions. Man-made features, such as roads and canals, will be removed. Surface water model cells located within former wetland areas that are now represented as developed areas of the Biscayne model domain will be activated. Model boundary data will be acquired from the NSM and interfaced in a parallel approach to that used with SFWMM model. The coupled TIME/Biscayne Bay model will be used to simulate likely predevelopment scenarios.
Specific Task Products: Presentations on the results of the linked model.
Title of Task 5: Documentation of coupled model.
Task Summary and Objectives: A report will be prepared to document methods, processes, and datasets used in development of the model to facilitate the ability of others to update the model or incorporate new or more efficient techniques or data as it becomes available. A USGS Scientific Investigations Report or journal article will be prepared that describes model development and calibration processes.
Work to be undertaken during the proposal year and a description of the methods and procedures: Document results of modeling efforts in either a USGS Scientific Investigations Report or journal article.
Specific Task Products: A USGS Scientific Investigations Report or journal article.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:09 PM(KP)