projects > ground water flow and transport for the SICS and TIME models > work plan
Project Work Plan
Greater Everglades Science Program: Place-Based Studies
Project Work Plan FY 2003
A. GENERAL INFORMATION:
Project Title: Groundwater Flow and Transport for the SICS and TIME Models
Project Summary: The interaction between surface water and groundwater can be a potentially significant component of the hydrologic water budget in the Everglades. Recent research has shown that surface water and groundwater interactions also can affect salinities in coastal wetlands. As Everglades restoration is largely dependent upon "getting the water right", the U.S. Geological Survey is developing the TIME (Tides and Inflows in the Mangroves of the Everglades) and SICS (Southern Inland and Coastal Systems) models, hydrodynamic surface water models of the southern Everglades. The purpose of the TIME and SICS models is to accurately simulate flows and salinities in the coastal wetlands of the southern Everglades. Once calibrated, these models will be used to evaluate proposed restoration scenarios by feeding hydrologic information into the ATLSS biological models. These biological models are highly sensitive to hydrologic inputs such as flows, stages, and salinities; thus, the TIME and SICS models are expected to play an important role in linking the hydrologic component of the Everglades to the biologic component.
In recent years, this project focused on developing a groundwater component for the SICS model, an integrated model of Taylor Slough and northern Florida Bay. The SICS model is now calibrated, operational, and providing important insight into the flow and salinity patterns of the southern coastal Everglades. Hydrologic output from the SICS model is being used in development of ATLSS fish models. The next step with this groundwater project is to extend the methodologies developed as part of the SICS modeling effort to the much larger TIME model. In FY02, a preliminary groundwater model was developed for the TIME area and six groundwater monitoring wells were installed within Shark and Taylor sloughs. In FY03, this project will focus on collecting field data for the continued development of the TIME groundwater model. The field investigation will be similar to the one conducted by Jud Harvey in Taylor Slough, but will instead focus on Shark Slough. Further development of the TIME groundwater model will continue in FY04 when sufficient data have been collected. The groundwater model will eventually be coupled with the TIME surface water model so that simulations and predictions of flow and salinity include accurate representation of leakage between the wetland and underlying aquifer.
Project Objectives and Strategy: The objective of this project is to develop a numerical groundwater flow model that can be used with the TIME surface water model to quantify and predict flows and salinities in the coastal wetlands of the southern Everglades. Field data will be collected to help formulate the hydrogeologic conceptual model and for calibration of the model to flows, water levels, and salinities. Data collection will consist of monitoring well installation, seepage measurements, spatial characterization of peat thickness, and continuous monitoring of water levels and salinities at selected locations.
Potential Impacts and Major Products: All of the numerical models currently used for CERP (Comprehensive Everglades Restoration Plan) neglect salinity and the effects of salinity on surface water and groundwater flow. The existing CERP models also fail to represent the hydrodynamic conditions in the coastal wetlands thereby limiting their ability to accurately simulate coastal flows. When coupled with the groundwater model developed as part of this project, the TIME model will be the only model capable of accurately simulating flows and salinities in the southern Everglades. This new capability will lead to better and more accurate biological models and will provide decision makers with reliable tools for managing the hydrologic system and evaluating alternative management scenarios.
Clients: ATLSS model developers, Everglades National Park, Big Cypress National Preserver, U.S. Army Corps of Engineers, South Florida Water Management District, National Oceanic and Atmospheric Administration
B. WORK PLAN
Title of Task 1: Installation of a nested monitoring wells in southwestern Shark Slough
Task Summary and Objectives: Little is known about the geology and aquifer system in southwestern Shark Slough. There are some shallow groundwater monitoring wells in the area, but no wells have been drilled to depths greater than 30 feet. This lack of data causes numerous problems for the development and calibration of the groundwater flow model. The purpose of this task is to install shallow, intermediate, and deep groundwater monitoring wells at a single site in southwestern Shark Slough. The location and depths of the wells will be based on airborne electromagnetic data, proximity to other monitoring sites, and geological materials encountered during drilling. The objective of this task, therefore, is to install 3 groundwater monitoring wells at different depths at one location in southwestern Shark Slough. The instrumentation of these wells to collect continuous water level and salinity data is described in Task 3.
Work to be undertaken during the proposal year and a description of the methods and procedures: Installation of groundwater monitoring wells in remote settings is difficult and time consuming. In addition to installing the wells, a considerable amount of time is spent in the mobilization logistics. The plans for installing the wells are as follows. One month prior to mobilization, all equipment, tools, and accessories will be purchased or tested and repaired. Approximately one week will be required to construct drilling platforms at the selected site and transport drilling equipment by airboat. The drilling equipment consists of a hydraulic engine that turns the drill stem, a tripod, air compressor, water pump, and miscellaneous hardware and drilling supplies. The deep monitoring well will be installed first to determine geology and locate permeable zones for remaining wells. We will attempt to install the deep well at a depth of approximately 150 feet, which is approximately the depth of the base of the Gray Limestone aquifer (Fish and Stewart, 1990). The remaining two wells will be installed at approximate depths of 75 and 20 feet. We anticipate that the well installation will take 6 to 8 weeks to complete.
Planned Outreach: Numerous governmental agencies have expressed interest in obtaining geologic and hydrogeologic information for southwestern Shark Slough. Lithologic and hydrogeologic information obtained as part of this task and will be published in a U.S. Geological Survey Open-File Report. Prior to releasing the report, non-interpretive data, such as well descriptions, will be placed on the TIME website.
Title of Task 2: Measurement of Surface Water/Groundwater Interactions
Task Summary and Objectives: The purpose of this task is to quantify the interaction of surface water and groundwater by deploying seepage meters and mapping the thickness of peat and marl. Calibration of the SICS integrated model indicates that additional data are required to verify the simulated rates of leakage between surface water and groundwater. With the current version of the SICS model, there is no way to guarantee that the simulated interaction between surface water and groundwater, which can be significant during certain times, is accurate. Therefore, the objective of this study is to directly measure seepage and map the thickness of the units that restrict vertical flow.
Work to be undertaken during the proposal year and a description of the methods and procedures: Traditional seepage meters are notorious for providing ambiguous data in low-flow settings. As part of this task, we will use the latest technology, either heat-pulse, electromagnetic, or sonic methods, to develop a seepage meter for use in the Everglades. This new seepage meter will be deployed for a short time (approximately one week) at the nested groundwater monitoring wells constructed last year and at the new wells constructed as part of this work plan. This will allow us to "rate" the head differences measured in the wells to the flow measured by the meter. Once the rating is completed for each site, we are optimistic that the continuously measured heads in the wells will allow us to calculate continuous seepage rates. The meter will also be deployed for short times at other locations and at other times to determine the spatial and temporal variability in seepage rates. In addition to the seepage measurements, measurements of peat thickness will be made along airboat trails to develop a map of peat thickness. At several locations, closely spaced measurements also will be made to characterize the spatial variability in peat thickness. The peat thickness measurements will be used with the seepage information to characterize the hydraulic properties of the peat.
Planned Outreach: A description of the seepage work and map of the peat thickness will be posted on the TIME website. A complete presentation of the seepage and peat study will be presented in a final report of the TIME groundwater model.
Title of Task 3: Continuous monitoring and geophysical logging at selected groundwater wells
Task Summary and Objectives: The purpose of this task is to collect continuous water level and salinity data at the monitoring wells installed as part of this project. There are currently six groundwater monitoring wells at three locations, and Task 1 describes plans for the installation of three additional wells. Continuous monitoring of water levels and salinity at these nine wells is covered under this task.
Work to be undertaken during the proposal year and a description of the methods and procedures: Instruments for measuring and logging continuous water levels and salinities are rented from HIF. Monthly or bimonthly visits by motor boat, airboat, or helicopter are required to download data and ensure data integrity.
Planned Outreach: Data collected from these wells is entered into ADAPS and made available to other agencies and interested parties. The data will also be published with the monitoring well information (see Task 1) in a U.S. Geological Survey Open-File Report.
Title of Task 4: Development and calibration of a variable-density groundwater flow and solute-transport model
Task Summary and Objectives: The purpose of this task is to continue with the development and calibration of the variable-density groundwater flow and solute transport model. The development of this model began in FY03 and a preliminary version of the model is running with the SEAWAT program. The objective of this task is to update and calibrate the current version of the groundwater model with the data collected under Tasks 1, 2, and 3. Another objective of this task is to use output from the TIME surface water model to facilitate with the development and calibration of the groundwater model. This objective cannot be achieved in FY04 unless we receive reliable output from the TIME surface water model by April 2004.
Work to be undertaken during the proposal year and a description of the methods and procedures: The first step in the continued development of the groundwater model is to update the aquifer characterization with the data collected during the installation of the deep well (Task 1). This new information should significantly increase our ability to simulate groundwater flow in the southwestern part of Shark Slough. The next step is to update the representation of the peat layer in the model with the new data collected as part of Task 2. Once this data is incorporated into the model, traditional calibration procedures will be used to adjust model parameters until simulated values of water levels, salinities, and leakage match with observed values. The calibration procedure will focus on the accurate representation of leakage between surface water and groundwater. This will ensure that the TIME surface water model will contain an accurate groundwater component once the models are coupled.
Planned Outreach: Presentations on groundwater model development will be given at the GEERS conference, CERP meetings, and to interested parties. The coupled surface water and groundwater will not be completed until 2005. At that time, a WRI report will be published to document the model.