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Relatively little is known about the processes controlling the fate and transport of the many toxic compounds associated with industrial wastes, and even less is known about how various inorganic and organic compounds interact once havi.ng entered the groundwater system. A more thorough understanding of the processes affecting contaminants in the subsurface is needed to assess future problems of contamination and to effectively contain and clean up contaminated ground waters. Analysis and selection of appropriate and cost-effective remedial measures to contain and restore contaminated ground water reJ.ies on a thorough understanding of the many •factors that affect the fate, transport, and transformation of contaminants once having entered an aquifer. To improve understanding of these factors, the U.S. Geological Survey, Office of Hazardous Waste Hydrology, is conducting three major research demonstration efforts addressing hazardous waste contamination of ground water. These national interdisciplinary field studies have developed important applied, developmental, and theoretical research findings which have expanded our knowledge of groundwater contamination transport processes. This series of technical papers presents the research conducted at a creosote works site in Pensacola, Florida. The papers were originally presented at a Toxic Waste-GroundWater Contamination Program symposium in Tucson, Arizona, in March 1984.

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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 ...

Groundwater exchanges with lakes resulting from cyclical wet and dry climate extremes maintain lake levels in the environment in ways that are not well understood, in part because they remain difficult to simulate. To better understand the atypical groundwater interactions with lakes caused by climatic extremes, an original conceptual approach is introduced using MODFLOW-2005 and a kinematic-wave approximation to variably saturated flow that allows lake size and position in the basin to change while accurately representing the daily lake volume and three-dimensional variably saturated groundwater flow responses in the basin. Daily groundwater interactions are simulated for a calibrated lake basin in Florida over a decade that included historic wet and dry departures from the average rainfall. The divergent climate extremes subjected nearly 70% of the maximum lakebed area and 75% of the maximum shoreline perimeter to both groundwater inflow and lake leakage. About half of the lakebed area subject to flow reversals also went dry. A flow-through pattern present for 73% of the decade caused net leakage from the lake 80% of the time. Runoff from the saturated lake margin offset the groundwater deficit only about half of that time. A centripetal flow pattern present for 6% of the decade was important for maintaining the lake stage and generated 30% of all net groundwater inflow. Pumping effects superimposed on dry climate extremes induced the least frequent but most cautionary flow pattern with leakage from over 90% of the actual lakebed area.