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G. L. Barr

Publications and source records attributed to G. L. Barr.

At least 19 recordsLinked to original sources
USGS1996

Hydrogeology of the surficial and intermediate aquifer systems in Sarasota and adjacent counties, Florida

From 1991 to 1995, the hydrogeology of the surficial aquifer system and the major permeable zones and confining units of the intermediate aquifer system in southwest Florida was studied. The study area is a 1,400-square-mile area that includes Sarasota County and parts of Manatee, De Soto, Charlotte, and Lee Counties. Lithologic, geophysical, hydraulic property, and water-level data were used to correlate the hydrogeology and map the extent of the aquifer systems. Water chemistry was evaluated in southwest Sarasota County to determine salinity of the surficial and intermediate aquifer systems. The surficial aquifer is an unconfined aquifer system that overlies the intermediate aquifer system and ranges from a few feet to over 60 feet in thickness in the study area. Hydraulic properties of the surficial aquifer system determined from aquifer and laboratory tests, and model simulations vary considerably across the study area. The intermediate aquifer system, a confined aquifer system that lies between the surficial and the Upper Floridan aquifers, is composed of alternating confining units and permeable zones. The intermediate aquifer system has three major permeable zones that exhibit a wide range of hydraulic properties. Horizontal flow in the intermediate aquifer system is northeast to southwest. Most of the study area is in a discharge area of the intermediate aquifer system. Water ranges naturally from fresh in the surficial aquifer system and upper permeable zones of the intermediate aquifer system to moderately saline in the lower permeable zone. Water-quality data collected in coastal southwest Sarasota County indicate that ground-water withdrawals from major pumping centers have resulted in lateral seawater intrusion and upconing into the surficial and intermediate aquifer systems.

Florida↗
USGS1993

Application of ground-penetrating radar methods in determining hydrogeologic conditions in a karst area, west-central Florida

Ground-penetrating radar (GPR) is useful as a surface geophysical method for exploring geology and subsurface features in karst settings. Interpretation of GPR data was used to infer lithology and hydrogeologic conditions in west-central Florida. This study demonstrates how GPR methods can be used to investigate the hydrogeology of an area. GPR transmits radio- frequency electromagnetic waves into the ground and receives reflected energy waves from subsurface interfaces. Subsurface profiles showing sediment thickness, depth to water table and clay beds, karst development, buried objects, and lake-bottom structure were produced from GPR traverses obtained during December 1987 and March 1990 in Pinellas, Hillsborough, and Hardee Counties in west-central Florida. Performance of the GPR method is site specific, and data collected are principally affected by the sediment and pore fluids, conductances and dielectric constants. Effective exploration depths of the GPR surveys through predominately unsaturated and saturated sand and clay sediments at five study sites ranged from a few feet to greater than 50 feet below land surface. Exploration depths were limited when high conductivity clay was encountered, whereas greater exploration depths were possible in material composed of sand. Application of GPR is useful in profiling subsurface conditions, but proper interpretation depends upon the user's knowledge of the equipment and the local hydrogeological setting, as well as the ability to interpret the graphic profile.

Water-Resources Investigations Report↗
USGS1985

Potentiometric surface of the upper Floridan Aquifer, west-central Florida, May 1985

A May 1985 potentiometric surface map of the Upper Floridan aquifer in west-central Florida depicts the annual low water-level period. Most areas of west-central Florida were experiencing drought conditions and water levels were at or approaching near-record low levels. Water levels in most wells measured in May 1985 were lower than in September 1985. May levels averaged about 5 feet lower than September levels in areas north of latitude 28 degrees 07 ' and about 13 feet lower in southern areas. Generally, water levels in May 1985 averaged about 4 feet lower than May 1984 levels in the north and about 6 feet lower in the south. (USGS)

Open-File Report↗
USGS1984

Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, May 1984

A May 1984 potentiometric surface map of the Southwest Florida Water Management District depicts the annual low water-level period. Water levels in most wells measured in May 1984 were lower than in September 1983. May levels averaged about 1 foot lower than September levels in areas north of latitude 28 07'10' ' and about 9 feet lower in southern areas. Generally, water levels in May 1984 were lower when compared to May 1983. Water levels in most wells measured in May 1984 averaged less than 1 foot lower than May 1983 levels in the north and about 2 feet lower in the south. (USGS)

Open-File Report↗
USGS1984

Potentiometric surface of the upper Floridan aquifer, Southwest Florida Water Management District, September 1984

A September 1984 potentiometric surface map of the Southwest Florida Water Management District depicts the annual high water level period. Water levels in most wells measured in September 1984 were higher than in May 1984. September levels averaged less than 1 foot higher than May levels in areas north of latitude 28 degrees 7 feet and about 6 feet higher in southern areas. Generally, water levels in September 1984 were lower when compared to September 1983. Water levels in most wells measured in September 1984 averaged less than 1 foot lower than September 1983 levels in the north and about 2.6 feet lower in the south. (USGS)

Open-File Report↗
USGS1983

Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, September 1983

Maps of the potentiometric surface of the Floridan aquifer in west-central Florida are prepared semiannually by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District. Maps for May and September show the potentiometric surface that is close to the annual low or high water level condition that usually occurs in May or September, respectively. The surface is mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. This report shows the potentiometric surface of the Floridan aquifer for September 1983. Data for the map were collected during September 12-23. The map represents water level conditions near the end of the summer rainy season when groundwater withdrawals for agricultural use are low. Water levels in most wells measured in September 1983 were higher than those measured in May 1983. September water levels averaged about 0.6 ft higher than May levels in areas north of Hillsborough County and about 7 ft higher in southern areas. Water level increases in the north ranged from zero to about 2 ft along coastal regions and from zero to about 5 ft in inland areas. Water level declines in the north ranged from zero to about 7 ft and occurred in scattered parts of all northern counties. In the south, water level increases ranged from zero to about 3 ft along coastal and extreme southern regions and from about 5 to 34 ft in other southern areas. The greatest water level increases occurred in southern Hillsborough County where irrigation pumpage contributes to large seasonal fluctuations. There were a few areas in Hillsborough and Pinellas Counties where September water levels showed declines ranging from about 1 to 3 ft when compared with May levels. (Lantz-PTT)

Open-File Report↗
USGS1982

Ground-water levels in selected well fields and in west-central Florida, September 1981

The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,200-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 140.3 million gallons to municipalities on September 21, 1981. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal on ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. In September 1981, ground-water levels were significantly higher than those of May 1981 and were unchanged or within a few feet of those in September 1980. Seasonal recharge from summer rains and reduced pumpage are factors in the water-level recovery from record and near record low levels of May 1981. (USGS)

Open-File Report↗
USGS1982

Potentiometric surface of the Floridan aquifer, Southwest Florida Water Management District, May 1982

A May 1982 potentiometric surface map of the Southwest Florida Water Management District depicts the annual low water-level period. Water levels in most wells measured in May 1982 were lower than in September 1981. Levels averaged about 9 feet lower in the southern part of the area and 1.5 feet lower in the north. In agricultural areas of southern Hillsborough, Manatee, southwestern Polk, southern Hardee, northwestern De Soto, and northern Sarasota Counties, water-level declines ranged from 5 feet to 29 feet. From May 1981 to May 1982, water-level increases ranged from about 3 feet in the northern counties to about 20 feet in the middle and southern counties. Water-level increases were about 4 feet in the extreme southern part of the study area.

Florida↗
USGS1982

Ground-water levels in selected well fields and in west-central Florida, May 1982

The water table in the surficial aquifer and the potentiometric surface of the Floridan aquifer in a 1,700-square-mile area in west-central Florida are mapped semiannually by the U.S. Geological Survey. Maps are based on water levels measured in wells each May to coincide with the seasonal low levels and each September to coincide with seasonal high levels. The mapped area shows 14 well fields that supplied 181.1 million gallons to municipalities on May 10, 1982. The water is withdrawn from the Floridan aquifer, the major aquifer in Florida. The effect of localized withdrawal on ground water is shown on the maps as depressions in both the potentiometric and water-table surfaces. In May 1982, ground-water levels were lower than those of September 1981. Seasonal recharge from above-average rainfall and reduced pumpage aided in the water-level recovery from record to near record levels of May 1981. (USGS)

Open-File Report↗
USGS1981

Water-quality data from a landfill-leachate treatment and disposal site, Pinellas County, Florida, January 1979-August 1980

Water-quality data collected between January 1979 and August 1980 at the landfill leachate treatment site in Pinellas County, Fla., are presented. Data include field and laboratory measurements of physical properties, major chemical constituents , nitrogen and phosphorus species, chemical oxygen demand, trace metals, coliform bacteria, taxonomy of macroinvertebrates and phytoplankton, and chlorophyll analyses. Data were collected as part of a study to determine water-quality changes resulting from aeration and ponding of leachate pumped from landfill burial trenches and for use in determining the rate of movement and quality changes as the leachate migrates through the surficial aquifer. Samples were collected from 81 surficial-aquifer water-quality monitoring wells constructed in January 1975, February 1979, and March 1979, and 8 surface-water quality monitoring sites established in January 1975, February 1978, and November 1978.

Florida↗