projects > groundwater-surface water interactions and relation to water quality in the everglades > work plan
U.S. Geological Survey Greater Everglades Science Initiative (Place-Based Studies)
Fiscal Year 2004 Project Work Plan
A. GENERAL INFORMATION:
Project Title: Groundwater-Surface Water Interactions and Relation to Water Quality in the Everglades
Phone: 703-648-5876 Fax: 703-648-5484
Project Summary: Successful restoration of the Everglades requires comprehensive knowledge of ground-water recharge and discharge, but few reliable estimates are currently available. These gaps not only leave the water budgets uncertain in some areas, but also hamper progress towards understanding the mobility and fate of waterborne contaminants. A critical concern for the restoration is the response of water quality to the planned modifications of the hydrology. What will be the effect of increasing the flow in the Everglades using water that may be of relatively poor quality? What will be the effect of the return to surface water of contaminants already stored in the subsurface water in peat and in the limestone and sand aquifer? Almost certainly contaminant levels of sulfate, mercury, and phosphorus will move farther into the system than ever before observed, but the rate of movement of contaminants is uncertain because there are essentially no investigations of the fundamental processes of solute transport in the Everglades. Even if water-quality targets for source waters to the Everglades are met, the stored contaminants in the wetland peat and subsurface will create a "legacy" of contamination as those contaminants are slowly returned to surface water. Again there is too little information about solute transport and surface-subsurface interactions to predict the rate of release of contaminants from the subsurface.
Our project addresses these needs by quantifying solute fate and transport in the Everglades, including fluxes between surface water, peat pore water, and the underlying aquifer. The goal is a better understanding of processes controlling the movement, storage, and biogeochemical transformations of mercury, phosphorus and sulfur in the Everglades. Also to be determined is the relative importance of the controlling factors (including water-resources management) in driving surface-subsurface exchange and enhancing transformation of solutes. Because contaminants stored in subsurface zones will be released only slowly back to surface water, greater knowledge of the storage of contaminants in subsurface zones is needed to predict future effects on water quality in the Everglades. Our data and interpretations are currently (or soon will be) used to parameterize important hydrology and water-quality models guiding the restoration, including SICS and TIME (USGS-Langevin, Swain, and Schaffranek), ENR Nutrient Balance (SFWMD-Chimney), and STA Design Reassessment (Kadlec and Walker - consultants), SFWMM (SFWMD-Obeysekera), ELM (SFWMD-Carl Fitz), and modeling by the FIU/SERC phosphorus-dosing flume research group (Evelyn Gaiser, FIU, P.I.).
Project Objectives and Strategy: Our objectives for FY04 are twofold, 1) continue conducting fundamental solute tracer experiments in the Everglades at the 10-m scale to quantify the fundamental physical transport processes, including surface-subsurface exchange, and its effects on solute transport in the Everglades, and 2) attempt to scale up results to the 10-km scale using an extension of our recently published radium isotope tracer approach, with the purpose of developing the parameter sets that are directly applicable in water-quality models. Objective 1 follows from a highly successful initial solute-tracer experiment at an FIU flume facility in Shark Slough (November 18-22, 2002). Plans to advance Objective 2 were proposed but not funded in FY03. Funding for both Objective 1 and 2 are essential in FY04 to allow us to scale our detailed results to spatial scales of tens of kilometers in Taylor Slough and Shark Slough. Our overall objective of improving water quality models depends on the scale comparisons between detailed (10-m) solute tracer experiments at selected sites with the larger scale (10-km) modeling of natural distributions of radium isotopes in surface and subsurface water. What we will gain by this dual-scale approach is the physical basis for water-quality models that are "process-specific" while also being applicable at the "watershed-scale". The ultimate goal is acquisition of the needed estimates of transport parameters for valid water-quality models. By that we mean hydrologic transport models and water-quality models and ecosystem models (such as SICS, TIME, and ELM) that should be more explicitly considering the effects of interactions between surface water and subsurface water on transport of environmentally important substances such as phosphorus, sulfate, and mercury. Also important is a more fundamental understanding of physical transport processes in surface water that affect transport and transformation of dissolved constituents. Physical transport processes that will be more extensively investigated by our experiments include interactions between surface water flow depths, flow velocities, vegetation type and vertical stratification, and microtopographic distributions, and how these affect solute transport and transformation in the Everglades.
Potential Impacts and Major Products for FY04/FY05:
Potential Impacts: An increasing group of researchers have identified water-quality issues as key issues that will affect success of the Everglades restoration. A foundation of the restoration is increasing the flow through the Everglades to restore pre-drainage hydropatterns. In our opinion not enough scientific attention has been given to how increased flow will affect the movement of solute contaminants that are introduced at the northern end of the system. Many scientists anticipate a movement of poor quality water farther into the Everglades than ever before. What will be the fate of those contaminants? How slowly or quickly will they move through the central and southern Everglades? How will the natural processes of surface-subsurface water exchange, and resulting biogeochemical transformations, affect water quality? Currently most water-quality models in the Everglades have relatively rudimentary representations of the solute transport mechanisms due to the lack of fundamental field studies. Knowledge of the processes that affect solute and fine-particle movement, such as advection, dispersion, and hydrologic retention caused by surface-subsurface exchange, are integral to understanding how the distribution of contaminated water in the Everglades will change over time. We believe that a field approach rooted both in fundamental solute transport experiments, as well as larger-scale extrapolations using the radium tracer, has the greatest chance for success for extrapolation to larger scales. To that end we expect all ongoing and future water-quality investigations to be informed by our work. Our detailed solute-tracer experiments and extrapolation to larger scale using radium will guide the development and parameterization of solute transport and water-quality models such as SWFT2D as implemented in the SICS and Time models (Eric Swain, USGS), and ELM (Carl Fitz, SFWMD). At the same time, our collaborators in process investigations (Greg Noe, WRD; Bill Orem, GD; Jim Saiers, Yale U.; Evelyn Gaiser, FIU-SERC; etc.) will provide the ecological and geochemical process measurements that will determine the rates of biogeochemical transformation that affect contaminants such as sulfate and nutrients.
Major Products in FY04/05: Our philosophy is to publish comprehensive USGS reports and open file data reports as quickly as possible for the South Florida community, but also to publish extended results and interpretations in the peer-reviewed literature of professional journals. We consider publication in international journals to be a critical step for USGS hydrologists working in the Everglades, both as a means to gain useful feedback (in the form of comments and reviews), as well as a means to eventually gain some agreement and acceptance of our new methods and ideas from the international scientific community.
We are still active in publishing results from on-going (but nearly completed) investigations in Water Conservation Area 2A, and will add to the production line new products from FY03 activities in Shark Slough. In FY04/05 we plan to continue reporting our results, again using the model of publishing in a variety of outlets including USGS interpretive reports, open-file data reports, and journal articles that will make the detailed data sets and the process interpretations available to the widest possible scientific community.
The first product in mid FY04 will document results from the bromide tracer test at an FIU flume facility in Shark Slough. The second product in mid to late FY04 will feature a watershed-scale modeling application in Taylor Slough that uses environmental radium measurements as well as detailed results from the bromide tracer test. The third product in mid to late FY05 will combine bromide results with a watershed-scale assessment of surface-subsurface interactions in Shark Slough. All fieldwork will be completed by early FY05 and all analysis and writing will be completed in FY05. The publication outlets are USGS reports and journal articles in Water Resources Research and Limnology and Oceanography.
Selected Accomplishments in Past Fiscal Years: Our partnership with SFWMD produced the most reliable and widely used estimates of recharge and discharge in the Everglades Nutrient Removal (ENR) project (Choi and Harvey, 2000), serving the SFWMD as the basis for their calculations of nutrient removal efficiency, and providing critical understanding of the likely role of groundwater in performance of the newly-completed Stormwater Treatment Areas. In the summer of 2002 we published a major interpretive report on occurrence and fate of mercury in ground water (Harvey et al, 2002). In early 2003 we published in the journal Limnology and Oceanography a new method to quantify recharge and discharge in the Everglades that takes advantage of natural distributions of radium isotopes (Krest and Harvey, 2003). Recently, a broader treatment of our data on recharge and discharge in Water Conservation Area 2A was accepted for publication in the journal Ground Water (Harvey et al., 2003). In the fall of 2002 we undertook a highly successful solute tracer experiment in one of the FIU flume facilities in Shark Slough. These accomplishments and associated data are providing the crucial information needed by modelers to validate their hydrologic and ecological models in ENR, and in WCA-2A, and Taylor and Shark Sloughs, Everglades National Park.
Major Products, 2002 - 2003:
Collaborators: Greg Noe (USGS, Reston), Jim Saiers (Yale University, New Haven), Evelyn Gaiser, (FIU, Miami)
Clients: Current users include TIME model developers (USGS-Langevin, Swain, and Schaffranek), South Florida Water Management Model Developers (SFWMD-Obeysekera), ENR Nutrient Balance Analyists (SFWMD-Chimney), and STA Design Reassessment Group (SFWMD-Kadlec and Walker). In the near future we expect our new work on tracer experimentation in the wetlands to be of tremendous value to water flow, water-quality, and biogeochemistry modelers and experimentalists, such as Sherry Mitchell-Bruker (NPS, Homestead), Dan Childers, (FIU, Miami), Carl Fitz (SFWMD, West Palm Beach), who operates the ELM water quality model, and Evelyn Gaiser and others at FIU who operate the FIU flume phosphorus dosing study.
B. WORK PLAN
Title of Task 1: Hydrologic Transport Processes Affecting Movement and Retention of Dissolved Constituents and Contaminants in the Everglades
Task Summary and Objectives:
Work to be undertaken during the proposal year and a description of the methods and procedures:
The principal work to be conducted in FY04 include both 1) detailed experimental studies and modeling of solute transport at relatively small scales (10-m), combined with 2) synoptic investigations of natural distributions of radium isotopes and modeling of solute transport at larger scales (10- km) in Taylor and Shark Sloughs.
Objective 1: First we discuss the detailed solute-tracer experiments. Last fall an initial tracer experiment proved that our basic design for detailed solute-tracer experiments is sound, and that results offer original and high-quality parameterizations of detailed transport processes that will be useful in larger-scale transport models in Taylor and Shark Sloughs. The general plan for detailed experimentation involves releasing a bromide salt solution (NaBr) by steady injection (for a period ranging between 4 and 24 hours) into surface water in Everglades National Park. We track both the downstream movement and vertical and longitudinal spreading of the tracer in surface water, as well as the exchange between surface water and peat porewater. As outlined above, we have particular interest in quantifying the rate and extent to which surface water and subsurface porewater are exchanged. This information is embedded within the surface-water tracer measurements but will be verified independently through measurements of concentrations of the bromide tracer in porewater of the peat. Our modeling will account for advection and vertical and longitudinal dispersion of solute in surface water, as well as the effects of exchange with peat porewater. We should note that a recently submitted pre-proposal with Greg Noe of USGS and Jim Saiers from Yale University relies on our solute tracer experimentation as the basis for fine-particle tracer experiments. The two projects therefore hope to be making simultaneous measurements of solute and fine- particle concentrations in the water column.
We have already proven that the experiments can be done in the Florida International University 100-m experimental phosphorus dosing flumes located in Shark Slough. The motivation was to not only take advantage of existing and appropriate infrastructure for our experiments, but also to support and collaborate with FIU and other USGS and university scientists toward an understanding of the dynamics of fine particle and phosphorus transport and cycling in the Everglades. We have been encouraged by the FIU project chief on the dosing study (Evelyn Gaiser - FIU) to continue work in the flumes. At the same time we have been encouraged by other interested scientists (primarily Mitchell-Bruker at NPS and Childers at FIU) to move our experiments outside the FIU flumes in some cases, both to get away from nutrient enrichment effects and also to gather results in other types of vegetated environments. One immediate challenge is to devise a portable physical structure that will allow us to conduct tracer experiments outside the flumes without disturbance of the natural flow environment. Also, in general we need to make more and better measurements of vegetation density as a function of depth compared with our initial tracer experiment.
Objective 2: Now we discuss the measurements and modeling necessary to scale up our information about solute transport to the watershed scale. Our strategy is to modify the site-specific radium isotopic tracer technique that we previously developed to quantify ground water and surface water interactions at a watershed scale. (Note that the first product of our work with radium isotopes was recently published in Limnology and Oceanography). To accomplish our goal of scaling up, we will need to extend our site-specific method using the radium tracer in a way that will allow us to quantify interactions between surface and subsurface water along a surface-water "flowpath" in the main flow-ways in Shark Slough and Taylor Slough. Some kilometer-scale sampling of the radium tracer and other physical and biogeochemical parameters have already been completed in Taylor Slough. Similar work will be conducted in Shark Slough beginning either in the 1st or 2nd quarter of FY04. Modeling solute transport and dispersion at the 10- km scale will require not only the radium measurements, but also information from the detailed tracer studies and meterologic and hydrologic information from existing hydrology data sets and sources in the Park.
Planned Outreach in FY04:
We anticipate continued interaction with SFWMD concerning our now largely completed investigations of interactions between ground water and surface water in the north-central Everglades. Interactions continue with the environmental engineering group analyzing nutrient uptake and storage in constructed wetlands (Mike Chimney - SFWMD), the design reanalysis group for Stormwater Treatment Areas (Robert Kadlec and William Walker), the Hydrologic Systems Group (Jayantha Obeysekera - SFWMD), and Evelyn Gaiser and others at FIU who are modeling the results of the phosphorus dosing study in Shark Slough. All of these groups are now more than ever concerned with detailed verification of the phosphorus cycling models in the STAs and the South Florida Water Management Model in specific areas of the Everglades where restoration projects will have appreciable effects on hydrology. We also expect to begin more frequent dialogues with water-quality and biogeochemistry modelers and experimentalists, such as Carl Fitz (SFWMD), who operates the ELM water quality model and hopes to apply it to the NSF-LTER study in Taylor and Shark Sloughs (Dan Childers, FIU, P.I.).
C. BRIEF DESCRIPTION ON HOW PROJECT TASKS SUPPORT THE DOI AND USGS EVERGLADES RESTORATION SCIENCE PLANS
In general, our proposed research supports the DOI and USGS Everglades Restoration Science Plans by:
In addition, our research would support many of the specific science objectives listed in the DOI and USGS Science Plans. These include:
DOI SCIENCE GOALS
Specific water projects:
Water quality projects:
Landscape scale modeling:
USGS SCIENCE GOALS
Get the hydrology right:
Built and natural system compatibility:
D. Related Work Funded By Other Agencies During Lifetime of Project:1996 - 1998 Cooperative Agreement C-6661 with the South Florida Water Management District, Groundwater-Surface Water Exchange Fluxes in the ENR Project.
1999 - 2003 Cooperative Agreement C-10719 with the South Florida Water Management District, Geochemical Mass-Balance Modeling in WCA-2A to Quantify Interactions Between Groundwater and Surface Water.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:08 PM(HSH)