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Assessment of the Interconnection Between Tampa Bay and the Floridan Aquifer System: Historical Groundwater Data Compilation and Analysis, 1976–2022

Scientific Investigations Report 2024-5073
Prepared in cooperation with the U.S. Army Corps of Engineers
By:
https://doi.org/10.3133/sir20245073

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Abstract

The U.S. Geological Survey used existing data collected after the last major navigational channel modification in the mid-1980s to investigate groundwater levels and chloride concentrations in wells in the Floridan aquifer system and other aquifers beneath and near Tampa Bay. Tampa Bay is located on the west-central coast of Florida and provides access for commercial shipping. In 2021, the U.S. Army Corps of Engineers began to investigate alternatives to improve the efficiency of the deep-draft navigation channels within Tampa Bay, reduce costs, improve safety, and analyze the implications of modifying navigational channels. The Floridan aquifer system underlies Tampa Bay and is the primary source of public water supply in the region. Modifications to the channels have the potential to expose the Floridan aquifer system to the saltwater in Tampa Bay, with the potential to increase salinity in wells in the region. Other factors affecting the groundwater levels and the location of the freshwater/saltwater interface were also examined, including changes in sea level, groundwater extraction, and variations in climate.

Groundwater levels and well-construction reports were used to identify whether different aquifer units are well-connected. Twelve wells had available data before and after the last major channel modifications, which took place in the 1980s, with six datasets of chloride concentration available in areas along the northern and eastern coastline of Tampa Bay, which is nearest to historical dredging activities. Of these six, Kendall’s τ and p-values indicated increasing trends in chloride concentration for three datasets (TR 11-2, TR 10-2, 51), no trend in chloride concentration for two datasets (TR 9-3, 50), and a decreasing trend in chloride concentration for one dataset (TR 9-1). The upward trends in chloride concentration observed for TR 10-2 and 51 are likely the result of changes in local groundwater withdrawals. Well TR 11-2 had a gradual increasing trend in chloride concentration, fresh groundwater throughout the period of record, and a 3- to 4-foot increase in hydraulic head during the period of record, possibly caused by the construction and control of the Tampa Bypass Canal, resulting in changes to the regional potentiometric surface.

Suggested Citation

Decker, J.D., 2024, Assessment of the interconnection between Tampa Bay and the Floridan aquifer system—Historical groundwater data compilation and analysis, 1976–2022: U.S. Geological Survey Scientific Investigations Report 2024–5073, 95 p., https://doi.org/10.3133/sir20245073.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Geologic and Hydrogeologic Setting
  • Hydrologic Stressors and Groundwater Flow
  • Historical Potentiometric Surface Data
  • Historical Data From Groundwater and Chloride Concentration Monitoring Wells
  • Data Analysis Summary
  • Opportunities for Future Research
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of the interconnection between Tampa Bay and the Floridan aquifer system: Historical groundwater data compilation and analysis, 1976–2022
Series title Scientific Investigations Report
Series number 2024-5073
DOI 10.3133/sir20245073
Year Published 2024
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Caribbean-Florida Water Science Center
Description Report: x, 95 p.; Data Release
Country United States
State Florida
Other Geospatial Tampa Bay
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
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