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A production well, called the south well, is located behind the white trailer in the middle of the photograph. This well and two other production wells pump groundwater from the sand and gravel aquifer to elevated storage tanks, such as the two shown in the background. In 1985, contaminants were detected in samples collected from the south well. To help understand groundwater flow in the underlying sand and gravel aquifer, the U.S. Geological Survey completed borehole geophysical logging at multiple locations, including the deepest monitoring well, WHF-05-OW-1D, shown here under the blue awning.

For more information on the USGS-the Federal source for science about the earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation:McBride, W.S., Bellino, J.C., and Swancar, Amy, 2011, Hydrology, water budget, and water chemistry of Lake Panasoffkee, west- Elevation, as used in this report, refers to distance above the vertical datum.Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C). AbstractA study of Lake Panasoffkee and the surrounding watershed was conducted between October 2005 and September 2009 to gain a better understanding of how this large lake fits within the regional hydrogeologic setting of west-central Florida. Lake Panasoffkee is part of the headwaters of the Withlacoochee River and has a major influence on the hydrology and ecology of that basin. The study defined the interaction between surface water and groundwater, and the magnitude of lake evaporation and groundwater inflow to the lake and how these relate to the Lake Panasoffkee water budget. Geochemical and isotopic analyses were used with water-budget results to describe water sources for the lake. Lake Panasoffkee, the underlying surficial aquifer, and the Floridan aquifer system are hydraulically connected. An area of focused groundwater-discharge potential, where groundwater levels are higher than surface-water levels, is present beneath Lake Panasoffkee and extends several miles northwest and southeast of the lake. Although the size and intensity of the discharge area varied with the seasons and with hydrologic conditions, discharging conditions remained constant throughout the study period.The sandy uplands farther northeast and southeast of Lake Panasoffkee showed the greatest potential for surfacewater to groundwater recharge within the study area. The Lake Panasoffkee watershed lacks a well-developed surface-water drainage system because rainfall rapidly infiltrates the sandy soils in the uplands and recharges the surficial aquifer. The intermediate confining unit is discontinuous in the study area, but even in areas where the confining unit is present, there is a well-developed internal drainage system that compromises the integrity of the unit. The internal drainage system consists of an interconnected network of karst features that includes sinkholes, fissures, and conduits. The discontinuous intermediate confining unit and internal drainage features allow the surficial aquifer to rapidly ...

To assess the vulnerability of ground water to contamination in the karstic Upper Floridan aquifer (UFA), age-dating tracers and selected anthropogenic and naturally occurring compounds were analyzed in multiple water samples from a public supply well (PSW) near Tampa, Florida. Samples also were collected from 28 monitoring wells in the UFA and the overlying surficial aquifer system (SAS) and intermediate confining unit located within the contributing recharge area to the PSW. Age tracer and geochemical data from the earlier stage of the study (2003 through 2005) were combined with new data (2006) on concentrations of sulfur hexafluoride (SF(6)), tritium ((3)H), and helium-3, which were consistent with binary mixtures of water for the PSW dominated by young water (less than 7 years). Water samples from the SAS also indicated mostly young water (less than 7 years); however, most water samples from monitoring wells in the UFA had lower SF(6) and (3)H concentrations than the PSW and SAS, indicating mixtures containing high proportions of older water (more than 60 years). Vulnerability of the PSW to contamination was indicated by predominantly young water and elevated nitrate-N and volatile organic compound concentrations that were similar to those in the SAS. Elevated arsenic (As) concentrations (3 to 19 microg/L) and higher As(V)/As(III) ratios in the PSW than in water from UFA monitoring wells indicate that oxic water from the SAS likely mobilizes As from pyrite in the UFA matrix. Young water found in the PSW also was present in UFA monitoring wells that tap a highly transmissive zone (43- to 53-m depth) in the UFA.

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Appendix 1. Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. Only the data collected in the open interval of the test well are displayed at 1 to 96 scale .............13 Appendix 2. Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. The full geophysical log is displayed at 1 to 12 scale .

Graph showing relation between the ratio of strontium-87 to strontium-86 and the inverse of the concentration of strontium in samples from the Withlacoochee River sites, springs, and groundwater reference wells ..