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

Project Proposal for 2001

CONTINUING PROJECT WORK PLAN - FY 2001

IDENTIFYING INFORMATION

Project chief: Judson W. Harvey
Region/Division/Team/Section: Eastern/WRD/Branch of Regional Research
Email: jwharvey@usgs.gov
Phone: 703-648-5876
Fax: 703-648-5484
Mail address: USGS, 430 National Center, Reston, VA 20192

Project title: Groundwater-Surface Water Interactions and Relation to Water Quality in the Everglades (4384-17800)
Ecosystem: South Florida (Activity 5.3.4)
Project start date: FY 1996
Project end date: FY 2002
South Florida Program(s)/element(s)/task(s):

Sub Activity 5.3.4.2 - Modeling and Support Studies for SICS (Southern Inland Coastal Systems). 60%.

Sub Activity 5.3.4.4 - South Florida Mercury, Geochemistry, and Water Quality Assessment. 40%.

PROJECT PURPOSE AND SCOPE:

At present there are few reliable estimates of hydrologic fluxes between groundwater and surface water in the Everglades. This gap in hydrological investigations not only leaves the water budget of the Everglades uncertain, it also hampers progress in understanding the processes that determine mobility and transformation of contaminants, such as mercury, sulfate and nutrients. The objective of this project is to quantify hydrologic exchange fluxes between groundwater and surface water and its effects on transport of contaminants in the Everglades. The research furthermore relates surface water and ground water interactions to past, present, and proposed management of surface-water levels and flows in the Everglades. The principal research sites are the Everglades Nutrient Removal Project (ENR), Water Conservation Area 2A (WCA-2A), and the freshwater wetlands of Everglades National Park. Results are being used to quantify ground-water exchange with surface flow, and to quantify the enhancement of chemical transformations of contaminants during transport across the interface between surface water and ground water.

PROJECT SIGNIFICANCE TO RESTORATION OF THE EVERGLADES:

For restoration of the Everglades to succeed there must be comprehensive knowledge about physical, chemical, and biological processes throughout the system. A key measure of success in the Everglades is the improvement or protection of water quality under changing hydrologic conditions. Although there is a basic understanding of how interactions between groundwater and surface water will affect water budgets under restoration, there is only a rudimentary understanding of how interactions between groundwater and surface water will affect water quality. Only field-oriented research and modeling can determine whether interactions between groundwater and surface water are currently storing pollutants in groundwater, how long those pollutants are likely to be stored in the aquifer, and under what changing management conditions associated with restoration will those pollutants be returned into the surface water system.

PROJECT ACCOMPLISHMENTS, OUTCOMES, AND PRODUCTS:

FY 2000 scientific accomplishments:

1. We determined that recharge from the Everglades Nutrient Removal area (ENR) to ground water accounted for 30% of the water pumped into ENR for treatment during the years 1994 - 1998. Recharge varied by about a factor of two over time and was positively correlated with ENR water level and rate of pumping surface water into the ENR. In contrast discharge from WCA-1 into ENR was a much smaller flux, according to our mass-balance and seepage-meter estimates. Our estimates of discharge were a factor of four smaller than estimates developed by the South Florida Water Management District. Our water balance results at ENR have important implications for managing the Stormwater Treatment Areas (STA’s) and the Water Conservation Areas (WCA’s). Early this year a manuscript describing our results (copy enclosed with this workplan) was submitted and we just learned that it is provisionally accepted for publication in the journal Wetlands.

2. We determined that recharging water in ENR is transporting dissolved mercury downward through peat and into storage in the Surficial aquifer. The process of recharge of total dissolved mercury accounts for 10% of the input of total dissolved mercury to the ENR by pumping and atmospheric deposition. In contrast, only 2.8% of mercury input to ENR discharges to the adjacent seepage canal, a perimeter canal that captures much of the water that is recharged in ENR. We conclude that dissolved mercury is being retained in the Surficial aquifer as a result of biogeochemical reactions with aquifer surfaces. The possible long-term effects of storage of contaminants in ground water in the northern Everglades has important implications for managing the Stormwater Treatment Areas (STA’s) and the Water Conservation Areas (WCA’s). The data and interpretations are described as part of a comprehensive USGS open-file report and an interpretive report (final draft copy of the approved open file report is enclosed with workplan). This work will also be presented at the Spring Meeting of the American Geophysical Union in Washington D.C., and will be written up for a journal publication this summer.

3. Our efforts using major ions and radium isotopes have identified a significant flux of groundwater into Taylor Slough from the west-side of the Slough, but quantification of that flux has been slowed due to the lack of a documented analysis of the surface-water velocity data in Taylor Slough. There is also uncertainty about the effect of particle-reactivity of the radium isotopes that will be addressed in upcoming work. Finally there was the difficulty of identifying actual flow paths of Taylor Slough water south of Taylor Slough Bridge. Significant progress was made on that front in FY2000 by teaming up with Clint Hittle and Mark Zucker to coordinate wetland and coastal sample collections. Sampling from July, 1999 through November, 1999 identified the pathway of movement of large pulses of freshwater that resulted from Tropical Storm Harvey and Hurricane Irene from source areas that began in upper Taylor Slough, in lower L31-W canal, and in the C-111 canal.

4. We also made progress in completing QA and QC of all of our measurements to date in Taylor Slough, including surface water staff measurements and ground water-level measurements, water depths, peat depths, estimates of peat hydraulic conductivity, and major-ion chemistry in surface and ground water. Our data set is the only type of its kind representing broad spatial patterns during time periods when intensive velocity gaging was being conducted in the Slough (September and November 1997, July 1998, and September 1999). A data report is presently being prepared after which all data will be made available on the SOFIA web site. In addition to defining flow pathways and locations of ground water inflow using chemical tracers, our data improve knowledge of the thickness and hydraulic properties of the peat. One interesting finding that was unexpected was our ability to improve the mapping of a trough in the top of the bedrock in Taylor Slough (as much as 5 feet deep), which undoubtedly has important effects on groundwater flow beneath Taylor Slough.

5. Work in Shark Slough only began in this fiscal year. Initial data show sharp contrasts in geochemical water type between the central slough and areas to the west, as well as provide initial measurements of peat depth and hydraulic conductivity. Those data will be useful for the TIME modeling project which to be successful must accurately characterize surface water flow pathways and interactions with ground water in Everglades National Park.

FY 2000 Outcomes:

Key results have been posted on the USGS SOFIA web site, and published (or are in preparation for publication) in a variety of outlets (USGS reports, fact sheets, peer-reviewed literature, and synthesis documents). Our results have implications for several key management programs in South Florida, including the following ones,

+ SFWMD ENR analysis group (main contacts Mike Chimney and Martha Nungasser) and Stormwater Treatment Area (STA) Functional Assessment Group. Those groups have shared responsibility to monitor hydrologic transport and water quality in ENR and some of the STAs that are now under construction. Our results indicate that all STA’s are likely to recharge groundwater and that the rate of recharge will be in part a function of the pumping rate into the STA. Our results also suggest that recharge may put nutrients and mercury into storage in groundwater. Those contaminants could potentially be released at a later time by discharge back to surface water.

+ SFWMD Hydrologic Modeling Systems Division, responsible for modeling for the Army Corps Surface-Water Storage and Conveyance Restudy (usually referred to as the Restudy, SFWMD Team Leader - Jayantha Obesekera). The South Florida Water Management Model is the key model for the Restudy, but it lacks detailed data sets to test the validity of some of the predictions, such as the magnitude and direction of hydrologic fluxes between ground water and surface water in particular areas of the Everglades. Our data provides the information necessary to test and validate that important SFWMD model.

+ SFMSP (South Florida Mercury Science Program with representation by SFWMD (Larry Fink), USGS (Dave Krabbenhoft), and State of Florida DEQ (Tom Atkinson). Downward mobilization of mercury by advective fluxes through peat and storage of mercury in the aquifer was an unexpected finding that affects the conclusions of the SFMSP.

+ USGS South Florida Mercury and Biogeochemistry Synthesis Project (Bill Orem and Dave Krabbenhoft). Our results provide an important capability toward developing mercury and sulfur mass balances in the Everglades.

+ USGS Southern Inland Coastal System Synthesis Project (Ray Schaffranek, Tom Smith, and Chuck Holmes). Prior to this work there was no reliable information about discharge of fresh groundwater to surface water in Taylor Slough. Our results indicate that discharge of groundwater augments freshwater flows to Florida Bay. Understanding the role of groundwater discharge in water and chemical mass balances in Taylor Slough will follow and be based in part on our results.

FY 2000 Products Completed or Nearly Completed:

Bates, A.L., Orem, W.H., Harvey, J.W., and Spiker, E.C., 1999, Sulfate contamination in the Everglades: Sources and relation to methylmercury production. Submitted to Environmental Pollution.

Choi, J. and Harvey, J.W., 2000, Quantifying time-varying groundwater discharge and recharge in wetlands: a comparison of methods in the Florida Everglades. Submitted January 7, 2000 for publication in Wetlands. Revised April 21, 2000 and provisionally accepted.

Harvey, J.W., Krupa, S.L., Gefvert, C.G., Choi, J., Mooney, R.H., and Giddings, J.B., 2000, Interaction between ground water and surface water in the northern Everglades and relation to water budgets and mercury cycling: Appendices. U.S. Geological Survey Open File Report 00-168. 364 pages.

Harvey, J.W., Krupa, S.L., Gefvert, C.G., Choi, J., Mooney, R.H., and Giddings, J.B., 2000, Interaction between ground water and surface water in the northern Everglades and relation to water budgets and mercury cycling. U.S. Geological Survey Water Resources Investigations Report 00-xxxx. ~ 80 pages. Estimated completion date June 15, 2000.

FY 2000 Stakeholder Meetings or Other Outreach Activities:

Presentations at national meetings in FY00:

Harvey, J.W., King, S.A., Fink, L.E., Krabbenhoft, D.P., Krupa, S.L., and Reddy, M.M., 2000, Role of interactions between groundwater and surface water in recharging and storing mercury within the Surficial aquifer system of the northern Everglades, EOS, Transactions of the American Geophysical Union, Spring Meeting of the American Geophysical Union, May 30-June3, 2000, Washington, D.C.

Harvey, J.W., and Krupa, S.L., 2000, Wetland and ground water interactions affected by water management in the Florida Everglades, Annual Meeting of the Society of Wetland Scientists, August 6-12, 2000, Quebec City, Canada. INVITED

Bibliography:

Bates, A.L., Orem, W.H., Harvey, J.W., and Spiker, E.C., 1999, Sulfate contamination in the Everglades: Sources and relation to methylmercury production. Submitted to Environmental Pollution.

Bates, A.L., Orem. W.H., and Harvey, J.W., 1998, Tracing sources of sulfate in the northern Everglades using sulfur isotopic compositions, EOS, Transactions of the American Geophysical Union, 79(17): S93.

Choi, J. and Harvey, J.W., 2000, Quantifying time-varying groundwater discharge and recharge in wetlandsof the northern Florida Everglades. submitted January 7, 2000 for publication in Wetlands, revides April 21, 2000 and provisionally accepted.

Harvey, J.W., Krupa, S.L., Choi, J., Gefvert, C., Mooney, R.H., Schuster, P.F., Bates, A.L., King, S.A., Reddy, M.M., Orem, W.H., Krabbenhoft, D.P., and Fink, L.E., 1999, Hydrologic exchange of surface water and ground water and its relation to surface water budgets and water quality in the Everglades in Gerould, S. and Higer, A. (eds.) U.S. Geological Survey Program on the South Florida Ecosystem: Proceedings of South Florida Restoration Science Forum, May 17-19, 1999, Boca Raton, Florida. U.S. Geological Survey Open-File Report 99-181, p. 36 – 37.

Harvey, J.W., Krupa, S., and Mooney, R., 1997, Spatial and seasonal variation in surface-groundwater exchange in the northern Everglades, presentation for 2nd Annual Meeting of USGS Investigators in the South Florida Ecosystems Program, August 25-28, 1997, Fort Lauderdale.

Harvey, J.W., Krupa, S.L., Mooney, S.L., and Gefvert, C., 1998, Interactions between ground water and surface water in the Everglades Nutrient Removal Area that affect mercury transport and transformation, Annual Meeting of South Florida Mercury Science Program Investigators, West Palm Beach, FL, May 18 - 20, 1998.

Harvey, J.W., Krupa, S.L., Mooney, R.H., Schuster, P., 1998, Are groundwater and surface water connected by vertical hydrologic fluxes through peat?, EOS, Transactions of the American Geophysical Union, 79(17): S87.

King, S.A., Harvey, J.W., Krabbenhoft, D.P., Hunt, R.J. Armstrong, D.E., DeWild, J.F., and Olson, M.L.. Distribution and transport mechanisms of mercury and methylmercury in peat of the Everglades Nutrient Removal Area. in in Gerould, S. and Higer, A. (eds.) U.S. Geological Survey Program on the South Florida Ecosystem: Proceedings of South Florida Restoration Science Forum, May 17-19, 1999, Boca Raton, Florida. U.S. Geological Survey Open-File Report 99-181, p. 50-51.

Krupa. S.L., Harvey, J.W., Gefvert, C., and Giddings, J., 1998, Geologic and anthropogenic influences on groundwater-surface water interactions in the northern Everglades, EOS, Transactions of the American Geophysical Union, 79(17): S176.

Orem, W.H., Bates, A.L., Lerch, H.E., and Harvey, J.W., 1998, Sulfur geochemistry of the Everglades: sources, sinks, and biogeochemical cycling, Annual Meeting of South Florida Mercury Science Program Investigators, West Palm Beach, FL, May 18 - 20, 1998. Abstract published with meeting program.

FY 2001 WORK PLAN:

FY 2001 activities:

Evaluating the success of ongoing restoration efforts in the Everglades depends on reliable hydrologic and water–quality information, including a thorough understanding of the role of interactions between surface water and ground water. The goals of the present project are;

(1) to quantify hydrologic fluxes between surface water and ground water,

(2) to determine relative importance of geologic factors and human influences that control interactions between ground water and surface water, and

(3) to employ improved estimates of surface-and ground-water exchange fluxes to increase the accuracy of hydrologic and water-quality modeling in the Everglades.

Sub Activity 5.3.4.2 - Modeling and Support Studies for SICS (Southern Inland Coastal Systems) and TIME (Tides and Inflows in the Mangroves of the Everglades).

Methodology:

Extensive use of traditional hydrogeologic methods to parameterize groundwater-surface water interaction models is impractical in many areas of the Everglades due to constraints on well construction. We propose to develop and test methods that are based on measurements in peat and in surface water to quantify groundwater-surface water interactions. The first approach involves estimating peat hydraulic conductivity, peat depth, and vertical hydraulic gradients in peat for input to the TIME model (i.e. the model that will couple surface and subsurface flow in Everglades National Park). Measuring the spatial distribution of hydraulic conductivity and vertical hydraulic gradients may prove quite useful, but it is possible that those measurements will be subject to small inaccuracies, that when upscaled, lead to large uncertainties in flux estimates in the Park wetlands as a whole. We therefore propose to develop an independent means to corroborate our results based on innovative use of geochemical tracing methods.

The advantage of using environmental geochemical tracers is flux estimates are obtained at larger spatial scales that are more similar to the scales of interest for practical problems of restoring flows and protecting water quality. The problem with using many of the existing methods in the Everglades is that the source waters to Everglades National Park have already interacted with groundwater, and therefore already have a ‘groundwater’ chemical signature. The ground water signature in Everglades source waters therefore interferes with the use of commonly used tracers to delineate groundwater interactions that occur within the Park. Our approach is to use Uranium series isotopes to quantify surface water and ground water interactions that occur within the confines of Everglades National Park.

Progress in FY00:

Taylor Slough: Much of the fieldwork has been completed in Taylor Slough. Chemical measurements were obtained trips in September 97, November 97, July 98, and July, September, and October 99. On many of those trips velocity gaging data and coastal-station chemical samples were also obtained by our collaborators. Efforts thus far in FY2000 have been expended on data analysis, data QA/QC, and initial steps of preparing a comprehensive data report. In the summer of FY200 we must also contend with the QA and QC of the velocity gaging data. In the latter part of FY2000 and extending into FY2001 we will return to Taylor Slough for some detailed tracer experiments to test the behavior of radium isotopes in surface water and peat sediments. That work will be conducted by a new NRC postdoctoral investigator (Dr. Jim Krest) for which there is a partial cost share by the USGS National Research Program. Other activities in FY 2001 will be modeling analysis and production of an interpretive report or journal publication.

Shark Slough: Work in upper and lower Shark Slough began in FY2000 by cooperating with Ray Shaffranek (WRD) and Tom Smith (BRD) to obtain access for measuring distributions of peat depth, hydraulic conductivity of peat, vertical hydraulic gradients in peat, and to determine surface-water flow pathways using geochemical tracers. For the coming wet season we will cooperate with Victor Leveque’s ‘Freshwater Discharge to the West Coast’ project to help determine flow pathways to the coast. Also in FY2001 we will use what we have learned about uranium isotopes in Taylor Slough to quantify groundwater discharge in Shark Slough. Eventually more wells may be needed in Shark Slough to determine regional hydraulic gradients and ground-water flow velocities in order to support accurate ground water modeling. Drilling of new wells in Shark Slough could be accomplished by USGS, but only with the involvement of Gene Shinn’s (GD-USGS) project.

Sub Activity 5.3.4.4 - South Florida Mercury, Geochemistry, and Water Quality Assessment.

Methodology:

Essentially the same as for Sub Activity 5.3.4.2 except that we were able to make greater use of seepage meters and pore water chemical profiles in peat, which provided additional independent estimates of vertical fluxes of water and dissolved constituents through the peat.

Progress in FY’00:

Like the work in Everglades National Park, our work in the north Everglades work involves developing and testing new methods to quantify groundwater-surface water interactions. Unlike the ENP work, our north Everglades work began earlier (in FY’96) and is now reaching maturity. Having completed the task of quantifying surface and ground water exchange fluxes, we are now emphasizing chemical reactions that occur at the interface between surface water and ground water. We are interested in those biogeochemical reactions that affect the fate of contaminants such as mercury, sulfate, and nutrients in the Everglades. At this stage our fieldwork is largely complete (except for continuation fieldwork that has been funded by SFWMD). In large part our activities at this point involve additional data analysis and modeling that are needed to reliably determine water fluxes and chemical reaction rates in flow paths connecting surface and ground water. We are also developing model analyses that are compatable with our data sets to quantify the role of groundwater and peat in storing contaminants and releasing them slowly over time to surface water. These model calculations are the basis for collaborative publications with S. King, Dave Krabbenhoft, and B. Orem. Funds are requested from the USGS program to complete data analysis, modeling, and publication of results. In FY’01 results will be published in journal articles, and as contributions to synthesis products such as fact sheets or circulars being developed by W. Orem and D. Krabbenhoft.

FY 2001 deliverables/products:

+ USGS Data Report: Interaction between ground water and surface water in Water Conservation Area-2A, northern Everglades. U.S. Geological Survey Open File Report 00-xxxx.

+ King, S.A., Harvey, J.W., Krabbenhoft, D.P., Hunt, R.J. Armstrong, D.E., DeWild, J.F., and Olson, M.L.. Distribution and transport mechanisms of mercury and methylmercury in a constructed wetland in the northern Florida Everglades. To be prepared for the journal Environmental Science and Technology.

+ USGS Data Report: Data Pertaining to Interaction between Surface Water and Ground Water in Taylor Slough, Everglades National Park. U.S. Geological Survey Open File Report 00-483.

+ Harvey, Wetland and ground water interactions increased by water management in the Florida Everglades: implications for freshwater storage and water quality. To be prepared for EOS, Transactions of the American Geophysical Union (weekly newsletter).

+ Fact Sheet: 4 pages. ‘Interaction of Ground Water and Surface Water in the Freshwater Wetlands of the Everglades’. Many of my synthesis contributions will be through contributions to the SICS and ‘Geochemistry and Water Quality’ synthesis efforts. However, I see the need for a concise ground water synthesis that will put in perspective results from ground-water research in different locations (e.g. northern Everglades and Everglades National Park) as well as work by different investigators (I hope that Dave Fitterman, GD-USGS and Rene Price, U. Miami will contribute to this fact sheet).

FY 2001 outreach:

+ Presentations tentatively planned at South Florida Water Management District and National Park Service Research Center.

+ Meeting of USGS South Florida Ground Water Investigators. The USGS South Florida PBS program has funded several investigations about groundwater flow beneath the Everglades, from the constructed wetlands in the north Everglades to the freshwater wetlands and saltwater Bays in Everglades National Park. The need for rapid progression into new study areas has left too little time for collaboration and cross-fertilization between ground water projects. I am proposing that an ‘Everglades Ground Water ’ Summit be held as part of a larger meeting in Florida, perhaps as early as the South Florida Science Conference in September 2000. The goal is to increase communication between USGS ground-water investigators in South Florida on topics such as conceptual models, tests of new and innovative methods, and improved information sharing and greater integration of results between studies.

New directions or major changes for FY 2001:

Not applicable, except that, at the request of Ray Shaffranek, my project will move to undertake new work in Shark Slough in support of the expansion of the boundaries for hydrological flow modeling in Everglades National Park.

PROJECT SUPPORT REQUIREMENTS:

Explanation: This is a field intensive investigation that requires methods development, numerous field days, data reduction, modeling analysis, and publication. The primary manpower need is for two postdoctoral investigators who will work between half and full time on the project. Dr.s Krest and Choi will work under the close supervision of the PI, who will be actively involved in project planning, fieldwork, and project reporting.

NAME YEAR/PAY PERIODS
Krest, James, NRC Postdoc, geochemist/hydrologist, WRD-USGS-Reston 2001/26pp 2002/26pp
Choi, Jungyill IPA, hydrologist/modeler, WRD-USGS-Reston 2001/13pp 2002/13pp
Harvey, Judson, hydrologist, WRD-USGS-Reston 2001/5pp 2002/5pp
Bohlke, J.K., geochemist, WRD-USGS-Reston 2001/1pp 2002/1pp

Major equipment/facility needs:

None.

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