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• Aquifer Characterizations

• Availability of Water

• Climate Change and Hydrologic Extreme Events

• Ecosystems

• Hydrologic Modeling

• Surface Water

• Water Quality Conditions

• Wetlands
• Factors Affecting Hydrologic Recovery of Wetlands in Well Fields
• Flooded Area and Plant Zonation of Wetlands in Well Fields
• Hydrologic Changes in Well Fields of Northern Tampa Bay

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Factors that Influence the Hydrologic Recovery of Wetlands in the Northern Tampa Bay Area, Florida

Project Chief: Patricia A. Metz
Cooperator: Southwest Florida Water Management District (SWFWMD), Tampa Bay Water
Period of Project: October2008 – September 2010

Problem Statement

Long-term groundwater withdrawals in the Northern Tampa Bay area have lowered the potentiometric surface of the Upper Floridan aquifer, and also the water table in the overlying surficial aquifer. As a consequence, water levels in many wetlands have declined, and flood frequency has been altered or diminished. The SWFWMD in association with Tampa Bay Water devised a Recovery Plan to help achieve minimum levels in the Northern Tampa Bay area, which includes a combination of reductions in total groundwater withdrawals from the Upper Floridan aquifer and alternative management techniques such as augmentation with and management of surface water. The reductions in groundwater withdrawals were initiated in 2003, and continue through the present time. As a result, many wetlands in the Northern Tampa Bay area have shown signs of recovery. However, based on analyses of long-term historical data, SWFWMD and Tampa Bay Water have identified a number of other wetlands (referred to as impaired wetlands) whose water levels have not responded as expected. The majority of these impaired wetlands are located in the vicinity of well fields where large quantities of water continue to be withdrawn for public supply (fig. 1).

Objectives

The primary objective of this study was to determine the factors influencing the hydrologic recovery of impaired wetlands in the Northern Tampa Bay area following reduction in groundwater withdrawals.

Installation of a shallow wetland monitor well.

Approach

The study wetlands were examined based on four factors known to influence the hydrologic condition and recovery of wetlands in west-central Florida: 1) the topographic position of the wetland in the landscape; 2) permeability of the underlying sediments; 3) recent karst activity near and beneath the wetland; and 4) depth to the potentiometric surface of the Upper Floridan aquifer beneath the wetland. Depending on the availability of data, comparisons were made between all or subsets of nine study wetlands. Multiple lines of evidence were used to establish how each of these four factors has affected the ability of water levels in the study wetlands to recover.

Results

The combination of two factors – the presence of recent karst activity below or near a wetland and the depth to the potentiometric surface of the Upper Floridan aquifer had the most influence on hydrologic recovery of the study wetlands. Low-permeability sediments and the absence of karst features underlying the wetlands have a positive influence on wetland recovery following reductions in groundwater withdrawals. Although of less importance than the other three factors, a low-lying topographical position benefited the hydrologic condition of several study wetlands both before and after reductions in groundwater withdrawals.

Measuring water levels in a wetland monitor well.

Information Product

Metz, P.A., 2011, Factors that influence the hydrologic recovery of wetlands in the Northern Tampa Bay area, Florida, U.S. Geological Survey Scientific Investigations Report 2011-5127, 58 p.