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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Initiative (Place-Based Studies)

Fiscal Year 2003 Project Summary Report

Project Title: Impact of 20th Century Water-Management and Land-Use Practices on the Coastal Hydrology of Southeast Florida

Project Start Date: 1999 Project End Date: 2003

Web Sites: http://sofia.usgs.gov/projects/impact_auc/

Location (Subregions, Counties, Park or Refuge): Greater Everglades Subregion 4 (Southeast Coast); Palm Beach, Broward, and Miami-Dade Counties

Funding Source: USGS's Greater Everglades Science Initiative (PBS)

Principal Investigator(s): Robert A. Renken rarenken@usgs.gov

Project Personnel: John Koehmstedt, jkoehmst@usgs.gov 703.648.4619; Scott Ishman, sishman@geo.siu.edu 618.453.3351; Joann Dixon, jdixon@usgs.gov 305.717.5800

Supporting Organizations: none

Associated / Linked Projects: none

Overview & Objective(s): Saltwater intrusion into the surficial aquifer is a direct consequence of water-management practices, concurrent agricultural and urban development, and natural drought conditions. This synthesis: (1) provides a temporal (predevelopment to present-day conditions) and spatial overview of coastal saltwater intrusion in south Florida; (2) identifies the principal factors that control the extent of saltwater intrusion; (3) evaluates long-term trends in ground-water withdrawal rates, ground-water level change, rainfall, and increases in chloride concentration; (4) illustrates causal relations between the position of the saltwater interface, water-management practices, and the expansion of agricultural and urban areas; and (5) discuss Everglades restoration scenarios and their anticipated effect on saltwater intrusion. A wide variety of maps and other analyses were conducted to examine anthropogenic changes and possible causal relations between movement of the interface. This synthesis successfully links water-management practices (canal-discharge), consumptive water use, water levels within the surficial aquifer system, chloride concentrations, ground-water discharge, and Holocene paleohistory of the Florida Bay and Biscayne Bay. For example, a series of water table maps for specific selected 5-year increments have been developed to spatially identify the areal extent where long-term water levels within the surficial aquifer has declined and to compare these changes with movement of the interface. Such changes are also being compared with changes in coastal outflows from major canals to distinquish between long-term declines caused by regional drainage and a large number of municipal pumping centers. Paleontologic data are being used to prepare maps illustrate temporal changes in salinity within the Biscayne Bay over the last 150 years. Salinity changes within the bay are largely attributed to a decrease in ground-water and surface water discharge.

Status: Completed--- Final report completed and being processed by Publications Unit. Draft report is 70 pages in length and includes over 120 separate illustrations, the majority of which represent new interpretive information. Published report will include GIS data layers (CD in pocket).

Recent & Planned Products:

Robert A. Renken, Joann Dixon, Scott Ishman, John Koehmstedt, A.C. Lietz, Richard Marella, Pamela Telis, Jeff Rogers, and Steven Memberg, in review, Impact of 20th Century Water-Management and Land-Use Practices on the Coastal Hydrology of Southeastern Florida: U.S. Geological Survey Circular XXX. (Note: This Circular was eventually published under the title "Impact of Anthropogenic Development on Coastal Ground-Water Hydrology in Southeastern Florida, 1900-2000", USGS Circular 1275).)

Robert A. Renken, Joann Dixon, A. C. Lietz, Telis, Pamela, Dausman, Alyssa, Rogers, Jeff, Memberg, Steven, Koehmstedt, John, Ishman, Scott, and Marella, Richard, 2003, Anthropogenic Impact of Water Management on Coastal Hydrology in Southeastern Florida in Arturo E. Torres, Aaron L. Higer, Heather S. Henkel, Patsy R. Mixson, Jane R. Eggleston, Teresa L. Embry, and Gail Clement, compilers, U.S. Geological Survey Greater Everglades Science Program: 2002 Biennial Report including Including USGS abstracts of presentations made at the Joint Science Conference on Florida Bay and Greater Everglades Ecosystem Restoration (GEER) - "From Kissimmee to the Keys", held April 13-18, 2003 Palm Harbor, Florida: U.S. Geological Survey Open File Report 03-54, p. 62-63.

Renken, Robert A., Ishman, Scott, Koehmstedt, John, Dixon, J.F., Lietz, A.C., Rogers, Jeffrey, Telis, P.A., Memberg, Steven, and Dausman, Alyssa, 2000, Synthesis on the impact of 20th century water-management and land-use practices on the coastal hydrology of southeastern Florida, in Higer, A.L., Eggleston, J.R., Embry, T.L., Mooney, R.L., Wedderburn, Leslie, Goodwin, C.R., Henkel, H.S., Pegram, K.M.H., and Enright, T.J., U.S. Geological Survey Program on the South Florida Ecosystem: 2000 Proceedings, U.S. Geological Survey Open-File Report 00-449, p. 43-44 (http://sofia.usgs.gov/geer/posters/use_impact/)

Relevance to Greater Everglades Restoration Information Needs:

Issues of relevance in this project include:
DOI science plan:

  1. Identify areas where the NSM model is not compatible with historical information. Ongoing need to make sure the NSM reflects current knowledge of the historical Everglades.
  2. Assessments of ecological responses to hydrologic change.

USGS Science Plan:

  1. How have manmade conveyances (canals) and barriers (such as highways) altered historical water levels and flows?
  2. What are the predicted impacts and benefits of restoration projects on the Greater Everglades ecosystem?
  3. What are the predicted effects of changes in water management?
  4. What factors concerning saltwater intrusion need to be considered before restoration projects are implemented? As restoration proceeds and built systems are added, removed, or altered, what responses are seen in the natural system?

Key Findings:

  1. This report graphically illustrates the effects of anthropogenic development during the last 100 years including spatial and temporal changes in land use, conveyance systems, agricultural and municipal water use on the coastal hydrology of southeast Florida.
  2. A complex infrastructure for water management has maintained lower ground-water levels inland to manage urban and agricultural flooding, and has been used to increase ground-water levels near the coast and to impede saltwater intrusion. However, coastal discharge in some areas appears to have declined in response to induced recharge to the surficial aquifer system as a result of large municipal and spatially extensive withdrawals.
  3. The natural balance between freshwater and saltwater was altered considerably following emplacement of conveyance and drainage canals and municipal supply wells. Canal drainage appears to have had the most widespread impact on intrusion, lowering water levels within the surficial aquifer system and contributing to landward movement of the interface.

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