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FLORIDA PROJECTS

Warm Mineral Springs, Sarasota County, Florida

Project Chief: Patty Metz
Collaboration: Sarasota County and City of North Port
Period of Project: FY 2014-2015

Problem Statement

Click to enlarge - Figure 1.  Location of Warm Mineral Springs, Sarasota County, Florida.

A decline in Warm Mineral Springs discharge has occurred during recent years, and during the same period, hydrologic conditions have changed in the area surrounding the springs. As development has expanded in this region, the need for groundwater has increased, and in southeastern Sarasota County, the increase in groundwater withdrawals has coincided with about a 10 to 20 foot decline in the potentiometric surface of the Upper Florida aquifer. It is difficult to determine the effect of increased withdrawals on spring flow because the depth of the source water to Warm Mineral Springs is unknown

Background

Warm Mineral Springs, located in southern Sarasota County (fig. 1), is the only warm (87° F), highly-mineralized spring in Florida. This unique geothermal spring has hydrologic importance, ecological and archeological significance, and economic value for Sarasota County. Since 1946, a day spa has operated at the spring, attracting vacationers and health enthusiasts. In addition, the warm water from the spring attracts manatees to the adjoining spring run during the winter months, and provides vital habitat for these mammals as well as an opportunity for environmental education. Well-preserved human bones, artifacts, and Pleistocene age animal bones and plant remains have been found in and around the spring, indicating that the spring has long been an attraction for humans. Clearly, Warm Mineral Springs is a multi-use resource, with numerous stakeholders involved in its development, management and sustainable use.

Conditions that led to the formation of Warm Mineral Springs and the source(s) of the spring water are uncertain. The primary warm-water conduit of the spring is developed in a carbonate unit belonging to the Arcadia Formation of the Hawthorn Group which resides within the intermediate aquifer system. The spring water is highly mineralized with chloride and sulfate concentrations ranging from 9,200-10,000 mg/L and 1,600-1,700 mg/L, respectively. The temperature of the spring has long been of scientific interest. There are several conflicting theories about the origin of the water. One theory is that the source is deep geothermally heated seawater flowing at the base of the Floridan aquifer system at depths of 3,000 feet, which then rises to the surface through fractures in the overlying carbonates. Other data indicate that the source of the water from Warm Mineral Springs is from the Ocala-Avon Park permeable zone of the Upper Floridan aquifer.

Objectives

The objective of this study is to provide a review, compilation, and objective summary of existing published and publically available data pertinent to the hydrology of the area. The data review and summary will help define and focus the questions about the hydrology that remain unanswered by previous studies. This review and summary will facilitate the design of a comprehensive study needed to help local, regional, and state water resources managers better understand and sustainably manage Warm Mineral Springs.

The long-term objectives of a possible future comprehensive study of Warm Mineral Springs will be to: 1) identify the source(s) of water and the boundaries and/or the extent of the springshed for Warm Mineral Springs; 2) characterize water quality changes with depth and source; 3) characterize flow by measuring the change in water quantity with depth and source; 4) determine the daily discharge from Warm Mineral Springs; 5) assess the potential for water-quality degradation within the spring/aquifer complex; and 6) assess the potential for changes in spring hydrology resulting from human activities within the springshed area.

Click to enlarge - Aerial photo of Warm Mineral Springs

Aerial photo of Warm Mineral Springs

Approach

The principal activity of this study will be to summarize existing data pertinent to the hydrologic conditions and hydrogeology in the study and surrounding area, which is the first step in any subsequent comprehensive analysis of Warm Mineral Springs. A literature and file search will be conducted and all pertinent hydrologic data from the area will be reviewed, compiled, and summarized. An inventory of historical and current streamflow, groundwater levels, and water use will be completed. Data from driller’s completion reports, existing core data from wells in the area, and lithologic and geologic logs will be compiled. Water levels from existing wells will be evaluated and summarized. A water-quality inventory will be completed and data will be summarized.

A summary of recent monitoring data at an existing surface site will be completed. Sarasota County has been collecting hourly water-level and water temperature data since May 1, 2012 at a site 75 ft upstream of the Ortiz Road culvert. The County will continue to monitor water level and temperature at this existing site for the duration of the study. The County also has measured discharge monthly at a discharge station on the spring run, and these measurements also will continue for the duration of the study.

Results

[Results are not yet available].

Information Products

A USGS Open-File Report will be published that will provide a comprehensive summary of existing data pertinent to the hydrologic conditions and hydrogeology in the study area and surrounding areas. In addition, data gaps will be defined, and a design for a comprehensive study of Warm Mineral Springs that will address those data gaps will be developed in consultation with the cooperators and stakeholders.

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