Geology topics

Research about Pasco County, Florida

Source-linked reports with geographic coverage including Pasco County, Florida.

3 recordsLinked to original sources

USGS1988

Water resources and effects of ground-water development in Pasco County, Florida

Ninety-nine percent of the 79.72 million gal/d of water used in Pasco County, Florida is groundwater from the Upper Floridan aquifer. In addition, 53.5 million gal/d is exported for use in Pinellas County. Chemical quality of the water generally falls within recommended limits for drinking water except near the coast. A groundwater flow model was used to predict drawdowns in water levels under five different development plans for west Pasco County. One of these plans was incorporated in an estimated groundwater development plan for 2035 for Pasco, Pinellas, and part of Hillsborough County. Reduction in evapotranspiration accounts for nearly all the water required for each development plan. Two plans showed less effect in drawdown and potential of saltwater intrusion than the other three. For the overall groundwater development plan for Pasco, Pinellas, and parts of Hillsborough Counties, the average potentiometric surface in 2035 would be from 8 ft higher to 20 ft lower than the average 1976-77 potentiometric surface. Reductions in head would increase the potential for infiltration of contaminants in areas where surficial materials are thin, sinkhole development in sinkhole prone areas, and upconing and lateral intrusion of saltwater. The potential for dewatering the surficial aquifer is great in the Cross Bar Ranch and Cypress Creek well-field areas. Evapotranspiration of groundwater would be reduced by 19% between 1976-77 and 2035. Exchange of water between the rivers and the aquifers will be reduced by 13%. Springflow will be reduced by 6%, and three springs will cease to flow. Model boundary inflow and outflow also will be reduced.

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USGS1985

Hydrogeology of the Cross Bar Ranch well-field area and projected impact of pumping, Pasco County, Florida

The hydrogeology and development of a groundwater flow model are described for a 121-square-mile area in Pasco County, Florida. The hydrogeologic framework consists of the surficial aquifer--a thin blanket of sand--and the underlying carbonates of the upper Floridian aquifer. The aquifers are separated by a leaky sand and clay confining unit. The Cross Bar Ranch well field occupies 13 square miles and contains 17 production wells averaging about 700 feet deep and tapping the upper Florida aquifer. Procedures to calibrate, test sensitivity to input parameters, and validate the model 's accuracy are described. Pumping at 30 million gallons per day should result in 5 feet of decline in the water table of the surficial aquifer over an 8-square-mile area and in the potentiometric surface of the Upper Florida aquifer over a 15-square-mile area. Under the 45-million-per-day maximum permitted rate, drawdown should be 5 feet or more in the water table and potentiometric surface over areas of 16 and 28 square miles, respectively. At the center of pumping, water levels could decline 15 to 25 feet. The surficial aquifer could possibly be completely dewatered in a small area of the well field when pumping is at the maximum rate.

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USGS1980

Ground-water hydrology of the Dade City area, Pasco County, Florida, with emphasis on the hydrologic effects of pumping from the Floridan aquifer

The Dade City area, northeast Pasco County, Florida, is an area of about 260 square miles. Of the approximately 32 million gallons per day pumped from the Floridan aquifer in the area in 1975, about 16 million gallons per day were pumped from an area of about 0.25 square miles by a citrus processing plant. There are essentially two producing zones in the Floridan aquifer in the Dade City area. The upper zone is from about 10 feet above to about 150 feet below National Geodetic Vertical Datum of 1929 , and the lower zone from about 300 to about 500 feet below NGVD of 1929. There is evidence of hydraulic interconnection of the upper and lower zones of the Floridan aquifer. This appears to be highly significant in terms of the geohydrology of the Floridan aquifer in the area, particularly with regard to its ground-water flow pattern, water quality, and aquifer hydraulic characteristics. In the immediate vicinity of the citrus processing plant, aquifer transmissivity may range from 200,000 to as much as 400,000 feet squared per day. It is probable the Floridan is only semiconfined in the immediate vicinity of the citrus processing plant. High aquifer transmissivity in the area is the reason why there are only a few feet of drawdown of the Floridan 's potentiometric level even near the center of the well field.

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