Caribbean-Florida Water Science Center
Integration of Seismic-Reflection and Well Data to Assess Potential Impacts of Structural Anomalies and Stratigraphic Features on Alternative Floridan Aquifer System Water Supply, Broward County
Project Chiefs: Kevin J. Cunningham
Figure 1. Lithostratigraphic units in study area, generalized geology, and correlation to hydrogeologic units. Subdivisions of Arcadia Formation and Avon Park Formation are informal.
The South Florida Water Management Districtís Regional Water Availability Rule, adopted in 2007, restricts urban withdrawals from the Biscayne aquifer to pre-April 2006 levels throughout southeastern Florida. The Rule requires that supply demands in excess of these levels must be met with alternative water sources. Another major policy decision influencing water-supply development in Broward County is legislation adopted by the State of Florida requiring elimination of ocean outfalls by 2025. Environmental stakeholders are pressing resource managers to fulfill these state obligations and increase use of the more deeply buried karst Floridan aquifer system (FAS) (Fig. 1) as a water resource to meet projected water-supply shortfalls, and as a reservoir for the disposal of wastewater via Class I deep injection wells and injection of reclaimed water. Water-supply options that make use of the FAS include (1) the utilization of the brackish upper FAS as source water, (2) aquifer storage and recovery (ASR), and (3) reverse osmosis (RO) desalination. Some water providers in Broward County have expressed reservations in developing the FAS as an alternative water supply based on a general lack of technical data and information regarding the sustainability of the FAS as a source of water. Furthermore, the limited development of the FAS in Broward County has resulted in a shortage of quality hydrogeologic data on which to base models that can simulate anticipated changes that will result from future water-supply projects. Intensified economic development of the FAS as a sustainable water resource in Broward County will depend on reliable knowledge of the hydrogeology of the FAS for use by water managers and planners. Improving the dependability of the current hydrogeologic framework of the FAS is essential to future modeling of the FASís long-term capacity to support water-supply development. Two critical geologic elements that impact the efficacy of FAS water-supply withdrawal and wastewater injection are the structural and stratigraphic components of the FAS hydrogeologic framework.
The objective of the proposed study is to better define the regional structural and stratigraphic setting of the middle and upper parts of the FAS in Broward County (Fig. 1). Because of the risk posed by structural geologic anomalies (faults, vertical fractures, karst collapse structures) and much less advanced stratigraphic knowledge of physical system, FAS system sustainability remains uncertain. Seismic sequence stratigraphic techniques coupled to existing borehole data offers an opportunity to improve existing groundwater flow models, as well as assess system sensitivity to well field interference, predict upconing of more saline fluids, improve water resource management, and aid in site selection of future FAS projects.
Figure 2. Water-based seismic-reflection profile program to be acquired for this project in early 2013, and existing seismic-reflection profiles on the Hillsboro Canal and in northeastern Miami-Dade County, which will be included in this study.
Acquisition, processing, and interpretation of water-based seismic-reflection profiles (Fig. 2) will be used to image deeply buried faults and karst-collapse structures (Cunningham and Walker, 2009; Cunningham and others, 2012), and more fully delineate hydrostratigraphy, lithostratigraphy, and sequence stratigraphy (Reese and Cunningham, 2013) for the FAS in eastern Broward County. Five previously acquired seismic-reflection profiles (Figure 2) will be used to enhance the seismic data base being acquired for this project. The new water-based profiles will be focused on a lithostratigraphic section that includes the FAS. Nearby FAS utility wells will provide sufficient data to make a reasonable correlation between hydrostratigraphy and lithostratigraphy in the wells, and seismic stratigraphy on the profiles.
Not yet available
Cunningham, K.J., 2014, Integration of seismic-reflection and well data to assess the potential impact of stratigraphic and structural features on sustainable water supply from the Floridan aquifer system, Broward County, Florida: U.S. Geological Survey Open-File Report 2014-1136, 5 p. https://pubs.usgs.gov/of/2014/1136/
Cunningham, K.J., 2013, Integrating Seismic-Reflection and Sequence-Stratigraphic Methods to Characterize the Hydrogeology of the Floridan Aquifer System in Southeast Florida: U.S. Geological Survey Open-File Report 2014-1136, 8 p. https://pubs.usgs.gov/of/2013/1181/
Cunningham, K.J., and Walker, C., 2009, Seismic-sag structures in Tertiary carbonate rocks beneath southeastern Florida, USA: evidence for hypogenic speleogenesis?: In Klimchouk, A.B., and Ford, D.C., eds., Hypogene Speleogenesis and Karst Hydrogeology of Artesian Basins. Ukrainian Institute of Speleology and Karstology, Special Paper No. 1, Simferopol, Ukraine, p. 151-158.
Cunningham, K.J., Walker, C., and Westcott, R.L., 2012, Near-surface, marine seismic-reflection data define potential hydrogeologic confinement bypass in the carbonate Floridan aquifer system, southeastern Florida: Society of Economic Geophysicists 2012 Annual Meeting, Las Vegas, NV, 6 p. https://library.seg.org/doi/abs/10.1190/segam2012-0638.1
Reese, R.S., and Cunningham, K.J., 2013, Preliminary stratigraphic and hydrogeologic cross sections and seismic profile of the Floridan aquifer system of Broward County, Florida: U.S. Geological Survey Open-File Report 2013-1141, 10 p. https://pubs.usgs.gov/of/2013/1141/