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Research about Duval County, Florida

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

12 recordsLinked to original sources
USGS2002

Variations in water levels and chloride concentrations in the Floridan aquifer system in Duval County, Florida

The Floridan aquifer system is the principal source of water supply in northeastern Florida. Increasing demands for water from the Floridan aquifer system in Duval County (fig. 1) have resulted in a need to evaluate changes in water levels and chloride concentrations. Rapid population growth in Duval County is creating an increasing demand for freshwater. In 1960, the population of Duval County was about 455,000 (Brown and others, 1986), and in 2000 it was estimated to be about 779,000. As population continues to increase, additional water supplies will be needed. Increases in pumpage to meet these demands will lower the potentiometric surface and increase the potential for the upward movement of saline water from deeper zones of the aquifer system (Spechler, 1994; and Phelps and Spechler, 1997). The increased demand for water from the Floridan aquifer system requires that this valuable resource be adequately managed. Information on the trends in the potentiometric surface and chloride concentrations in the Floridan aquifer system is necessary for proper planning and management. This map report, prepared in cooperation with the City of Jacksonville, depicts the altitude of the potentiometric surface of the Upper Floridan aquifer in Duval County, and shows trends in the potentiometric surface and in chloride concentrations in the Floridan aquifer system at selected locations. The information presented in this report includes: (1) graphs showing water use for Duval and adjacent counties from 1965 to 1999; (2) maps showing the altitude of the potentiometric surface of the Upper Floridan aquifer in Duval County for January-February 1960, September 1998, and May 1999; (3) a map showing changes in the potentiometric surface of the Upper Floridan aquifer from January-February 1960 to May 1999; (4) hydrographs showing long-term water levels of selected wells in Duval County; and (5) graphs showing chloride concentrations in water at selected wells in Duval County.

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USGS1997

The relation between hydrogeology and water quality of the Lower Floridan Aquifer in Duval County, Florida, and implications for monitoring movement of saline water

The hydrogeology of the Upper zone of the Lower Floridan aquifer and its relation to water quality were evaluated during a 3-year (1993-96) study. The Floridan aquifer system, a carbonate aquifer system composed of the Upper Floridan aquifer, a middle semi-confining unit, and the Lower Floridan aquifer, is the major source of water supply in northeastern Florida. The Lower Floridan aquifer is further subdivided into the Upper zone, a semi-confining unit, and the Fernandina permeable zone. As a result of increased withdrawals, heads in the aquifer system have declined and at the same time chloride concentrations have increased in the water from many wells in Duval County. A better understanding of the sources of and pathways for movement of brackish water is needed so that water managers can monitor the movement of brackish water and plan future water development. Most of the wells in Duval County deeper than 900 feet penetrate the Upper Floridan aquifer and the Upper zone of the Lower Floridan aquifer. Transmissivity estimates for these zones range from 2,000 to 194,000 feet squared per day. Permeability in the Upper zone of the Lower Floridan aquifer is primarily related to secondary porosity developed along bedding planes, joints, and fractures as a result of paleokarst processes. The Upper zone is about 300 to 500 feet thick in Duval County, based on the geophysical logs of about 40 wells ranging in depth from about 1,000 to 2,200 feet. In some areas the Upper zone has a single flow zone, but in other areas, two distinct flow zones are apparent. Water samples collected during this study confirm the continued increase in chloride concentrations in both the Upper Floridan aquifer and the Upper zone of the Lower Floridan aquifer. Most of the observed increases are in the eastern part of the county, but a pattern in the locations of wells yielding water with chloride increases is not discernible. In some areas, zones bearing brackish water are underlain by zones of fresher water, but in other areas, fresher water was not found beneath the brackish water. A single fracture or solution feature was the source of brackish water in several wells. The most likely source of brackish water to the Upper zone of the Lower Floridan aquifer is the underlying Fernandina permeable zone, which contains freshwater in the western part of the county but saline water in the eastern part. The pathways for movement of saline water are interconnecting vertical and horizontal fracture or solution zones probably developed along paleokarst features that are not mappable from the land surface; therefore, a conventional monitor-well network probably would not provide early warning of saline-water intrusion. Continued monitoring of water-quality trends in water-supply wells, combined with collection of additional surface and borehole geophysical data, can provide an increased understanding of the movement of brackish water in the Floridan aquifer system.

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USGS1995

The distribution of bromide in water in the Floridan aquifer system, Duval County, northeastern Florida

Although Duval County, Florida, has ample ground-water resources for public supply, the potential exists for a problem with excessive disinfectant by-products. These disinfectant by-products result from the treatment of raw water containing low concentrations of bromide and naturally occurring organic compounds. Because of this potential problem, the relation of bromide concentrations to aquifer tapped, well location and depth, and chemical characteristics of water in the Floridan aquifer system underlying Duval County were studied to determine if these relations could be applied to delineate water with low-bromide concentrations for future supplies. In 1992, water samples from 106 wells that tap the Floridan aquifer system were analyzed for bromide and major dissolved constituents. A comparison of bromide concentrations from the 1992 sampling with data from earlier studies (1979-80) indicates that higher bromide concentrations were detected during the earlier studies. The difference between the old and new data is probably because of a change in analytical methodology in the analysis of samples. Bromide concentrations exceeded the detection limit (0.10 milligrams per liter) in water from 28 of the 106 wells (26 percent) sampled in 1992. The maximum concentration was 0.56 milligrams per liter. There were no relations between bromide and major dissolved constituents, well depth, or aquifer tapped that would be useful for determining bromide concentrations. Areal patterns of bromide occurrence are not clearly defined, but areas with relatively high bromide concentrations tend to be located in a triangular area near the community of Sunbeam, Florida, and along the St. Johns River throughout Duval County.

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USGS1994

Water resources of Duval County, Florida

The report describes the hydrology and water resources of Duval County, the development of its water supplies, and water use within the county. Also included are descriptions of various natural features of the county (such as topography and geology), an explanation of the hydrologic cycle, and an interpretation of the relationship between them. Ground-water and surface-water resources and principal water-quality features within the county are also discussed. The report is intended to provide the general public with an overview of the water resources Of Duval County, and to increase public awareness of water issues. Information is presented in nontechnical language to enable the general reader to understand facts about water as a part of nature, and the problems associated with its development and use.

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USGS1983

Appraisal of the interconnection between the St Johns River and the surficial aquifer, east-central Duval County, Florida

The proposed deepening of the navigation channel in the St. Johns River to about 46-48 feet below sea level (45 feet below mean low water) may breach up to 11 feet of limestone unit of the lower part of the surficial aquifer along a 25-mile channel. The limestone supplies water to numerous domestic wells along the river in the Jacksonville area. Recent channel improvements to about 39 feet below sea level have already breached the limestone at many locations. Where breaching has not yet occurred, less than 1 to 6 feet of undifferentiated sediments overlie the limestone. These sediments, consisting predominantly of sand, are generally too permeable to form an effective confining layer. Chloride concentrations determined from water in wells tapping the limestone unit range from 8 to 6,600 milligrams per liter. However, chloride concentrations in water from wells located more than 500 feet from the river, were generally less than 30 milligrams per liter. The proposed dredging operation is not expected to alter significantly the present hydrologic system. The current position of the interface most likely represents conditions that will be present after future channel improvements. (USGS)

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USGS1982

Chemical quality of water in the upper part of the Floridan aquifer, Duval County, Florida

The Floridan aquifer is the principle source of freshwater in Duval County (fig. 1). Most water-supply wells penetrate only the upper 600 feet of the aquifer because highly mineralized water is found in the deeper zone. Earlier investigations have shown that within the upper 600 feet of the aquifer, the water quality varies considerably. In most areas the water contains very low concentrations of inorganic constituents whereas in other areas the concentrations are much higher. In order to determine the areal distribution of the inorganic constituents in the upper part of the aquifer, water samples were collected from selected wells throughout Duval County and analyzed for common chemical constituents.

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USGS1982

Generalized configuration of the top of the limestone unit of the lower part of the surficial aquifer, Duval County, Florida

The top of the limestone unit ranges from about 25 feet above sea level in western Duval County to about 75 feet below sea level locally in the eastern part of the county. The limestone, which is part of the surficial aquifer, is the principal source of water to shallow wells in the county. The unit generally consists of a soft, friable, cavernous, sandy limestone, which ranges from about 5 to 40 feet in thickness. Along the coast and in the southern part of the county, the limestone becomes discontinuous.

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USGS1979

Estimated drawdowns in the Floridan aquifer due to increased withdrawals, Duval County, Florida

Hydrologic investigations of the Floridan aquifer in Duval County, Florida, have shown that an appropriate simplified model of the aquifer system consists of a series of sub aquifers separated by semipermeable beds. Data from more than 20 aquifer tests were reanalyzed by the Hantush modified method, which takes into account leakance from all confining units. Transmissivity values range from 20,000 to 240,000 square feet per day. Leakance was estimated to be 2.5x10 to the minus 6th power and 3.3x10 to the minus 5th power per day for the upper and lower confining units, respectively. Families of steady-state distance-drawdown curves were constructed for three representative transmissivity values based on hypothetical withdrawals from a point source ranging from 5 to 50 million gallons per day. Transient effects were not considered because the system reaches steady-state conditions within the time ranges considered. Drawdown at any point can be estimated by summing the effects of any hypothetical configuration of pumping centers. The accuracy of the parameters was checked by comparing calculated drawdowns in selected observation wells to measured water-level declines. (Woodard-USGS)

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USGS1978

Altitude and configuration of the top of the Floridan Aquifer, Duval County, Florida

Structural contours on the top of the Floridan aquifer in Duval County, Florida, show that the top of the aquifer ranges from less than 300 feet below sea level to more than 600 feet below sea level. Two inferred concealed faults occur in the aquifer; one trending northeast-southwest in the eastern part of the county. The maximum vertical displacement of the top of the aquifer of both faults is about 150 feet. A geologic section included on the map shows the geologic formations of Eocene age that comprise the Floridan aquifer. These are, in ascending order: the Lake City Limestone, the Avon Park Limestone, and the Ocala Limestone. (Woodard-USGS)

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USGS1978

Availability and quality of water from shallow aquifers in Duval County, Florida

The shallow-aquifer system in Duval County, Fla., overlies the Florida aquifer and is composed chiefly of sand, clay, sandy clay, and limestone. Thickness of the system ranges from about 300 to 600 feet. The upper 150 feet of deposits, consisting of the water-table and shallow-rock zones, are the most dependable and economical source of supplemental water supply. The principal shallow water-bearing zone is a limestone bed 40 to 100 feet below land surface. Aquifer tests conducted at 13 sites in Duval County show that yields from the shallow aquifer vary from place to place within the county owing chiefly to variations in lithology of the saturated rocks and sediments. The limestone of the shallow-rock zone will yield as much as 200 gallons per minute to wells; the maximum yield at most of the sites tested was between 30 and 100 gallons per minute. The water-table zone generally yields 10 gallons per minute or less but at one site, where a water-table well tapped a shell bed near land surface, the well yielded more than 40 gallons per minute. The quality of water in the shallow aquifer system in Duval County is generally acceptable for most domestic, commercial, and industrial uses. In some places, however, it has a high iron concentration and is hard. The iron concentration exceeds 0.3 milligrams per liter in water from the water-table or shallow-rock zones at 7 of the 13 aquifer test sites. The hardness of water from the aquifer ranges from about 60 to about 180 milligrams per liter. (Kosco-USGS)

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USGS1976

Flood-prone areas of Jacksonville, Duval County, Florida

Floods in the consolidated city of Jacksonville, Duval County, Florida, are caused directly by rainfall which, when combined with storm driven tides, causes rivers or other bodies of water to flood the low lying parts of the county. This map report supplies information on areas subject to floods of 100-year frequency; the information will permit evaluation of alternative uses of such areas. The extent of the 100-year flood is shown on the large-scale map accompanying the report. Also included is an index map showing sections of Duval County where more detailed information on the 100-year flood can be obtained. The major flood of record in the county occurred in 1964 when Hurricane Dora crossed the area. (Woodard-USGS)

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