Abstract >Introduction Study Area Aquifer Framework and Definitions Transmissivity, Hydraulic Conductivity and Storage Coefficient Hydrogeology Ground-Water Flow System Summary References Cited PDF Version

Southeast Florida (fig. 1) is underlain by materials of varying permeability from land surface to depths of 150 to 400 feet that provide most of the water used in the area. This body of materials is herein called the surficial aquifer system. In parts of Dade, Broward and Palm Beach Counties, a highly permeable part of that aquifer system has been named the Biscayne aquifer (Parker, 1951; Parker and others, 1955). Adjacent to or underlying the Biscayne aquifer are less permeable, relatively unknown, by potentially important water-bearing materials which also are part of the surficial aquifer system.

Most previous work in southeast Florida had been concentrated in the populated coastal area. Drilling and monitoring activities were commonly restricted to zones used for water supply or to overlying zones. Hence, information concerning the characteristics of the western or deeper parts of the Biscayne aquifer and of sediments below the Biscayne aquifer in the surficial aquifer system were insufficient for present needs. Because of persistent increases in were demand from the surficial aquifer system in the highly populated and growing coastal area of southeast Florida and because of attendant concerns for the protection and management of the water supply, the U.S. Geological Survey, in cooperation with the South Florida Water Management District, began an investigation to define the extent of the surficial aquifer system and its characteristics on a regional scale.

The overall objectives of the regional study are to determine the hydrogeologic framework, the extent and thickness of the surficial aquifer system and the aquifers within it, the areal and vertical water-quality distribution and factors that affect the water quality, the hydraulic characteristics of the components of the surficial aquifer system, and to describe ground-water flow in the aquifer system. Results of the investigation are planned for publication in a series of reports that provide information for each county or area as it becomes available. Broward County (fig. 1) is the first to be investigated in this regional study. Three reports were planned for Broward County, including a geologic framework report prepared by Causarás (1985), a water-quality report, and a hydrogeology ground-water report.

This report describes the hydrogeology of the surficial aquifer system and ground-water flow in the aquifer system in Broward County, Fla. The purpose is to provide fundamental background information that is basic for qualitative or quantitative evaluations of the ground-water resource and the hydraulic response of the system to natural or artificial stresses. Specifically, the objectives are to: (1) define the surficial aquifer system and aquifers within it; (2) characterize hydraulic properties of the surficial aquifer system; and (3) interpret ground-water flow in the surficial aquifer system.

The study is intended to provide a broad countywide characterization of the surficial aquifer system rather than detailed site-specific or local information. An extensive field program of hydrogeologic test drilling, water-quality sampling, and aquifer testing was conducted during 1981-84. Most test holes in west and central Broward County were drilled to a depth of about 200 to 230 feet, but those closer to the coast were drilled much deeper, reaching 476 feet at two sites. At most sites, drilling fully penetrated the surficial aquifer system, reaching into the upper part of the underlying confining unit. Other data selected from existing geologic logs, historic water-level records, and aquifer or production well tests were used to supplement the field data.

Although a comprehensive water-resources investigation has not been made heretofore for all of Broward County, many investigations of selected topics or areas – almost exclusively in the eastern part of the county – have been reported. Parker and others (1955) gave information on the geology of the county; the occurrence, movement, and quality of ground water and surface water; and saltwater intrusion. Schroeder and others (1958) improved knowledge of the Biscayne aquifer with many shallow test holes and geologic sections in west Broward and Dade Counties and a contour map of the base of the aquifer. Studies of ground-water resources of local areas (fig. 2) have been reported by Vorhis (1948) for Fort Lauderdale, by Sherwood (1959) for Oakland and Hardee (1970) for the lower Hillsboro Canal area, and by Bearden (1972; 1974) for Hallandale and Hollywood, respectively. Sherwood and others (1973) synthesized the available data and much new information to form a better understanding areally of east Broward County. Other pertinent reports include a discussion of the chemical quality of waters by Grantham and Sherwood (1968), "Water and the south Florida environment" by Klein and others (1975), and the most recent description of the Biscayne aquifer and its hydrologic characteristics by Klein and Hull (1978).

Hydrogeologic test drilling was conducted at sites arranged to form intersecting lines across the county (fig. 3, table 1). A reverse-air dual tube drilling method, which circulates air (no drilling mud was used) downward in the annulus between the tubes and back to the surface in the inner tube with entrained cuttings and water, was used. The method alleviated problems of collecting representative geologic samples that mud-rotary methods often encounter in this area. The problems include lost circulation in cavities with loss of samples and "running water sands" that cause collapse of test holes. Pieces of rock layers and clean (free of drilling mud) samples of clastic materials were obtained from which inferences of hydraulic properties were made. Some of the rock samples were used for laboratory tests for porosity and hydraulic conductivity. Additionally, the samples were assigned a relatively accurate depth, and hydrologic observations were made of flow variations during drilling and at 10-foot intervals after completing each drill pipe length.

Figure 3. Location of test drilling sites and hydrogeologic sections (from Causarás, 1985). Well numbers and site names are listed in table 1. [larger image]

After drilling each 10-foot length of drill pipe, air was circulated to obtain water from the aquifer. Circulation was continued, for several minutes if necessary, to obtain water as free from sediment as possible. Yields varied between 0 and 300 gal/min. Water samples were collected for analyses of specific conductance in the field and chloride concentration in the laboratory. Experience has shown that specific conductance and chloride concentration of water collected from circulation during drilling is similar, in most circumstances, to results from complete analyses of water collected by normal pumping and filtering techniques inside the drill rod and of water collected from finished wells at the test sites. The water produced by air circulation at a given depth is generally representative of the formation water at that depth. Profiles of specific conductance or chloride concentration with depth can then be constructed. These profiles have proven useful in revealing gross water-quality characteristics and making hydrologic or hydraulic inferences.

Previously available aquifer tests and specific capacities of production wells were compiled for estimating transmissivity and hydraulic conductivity in east Broward County. On the basis of the geologic sections prepared by Causarás (1985), inspection of geologic samples, and hydrologic observations made during drilling, a hydraulic testing program was designed to provide estimates of transmissivity or hydraulic conductivity of selected zones or materials at selected sites primarily in central and west Broward County. In some instances, multiple-well tests were made to determine storage coefficients.

Historic records of ground-water and surface-water levels were compiled from U.S. Geological Survey and South Florida Water Management District files to prepare water-level maps useful for interpreting ground-water flow.

Table 1. U.S. Geological Survey well numbers and informal site names for test sites. [see figure 3 for location of sites]
USGS well number	USGS site identification number			Informal site name (this report only)
	Latitude	Longitude	Sequence number
G-2311	260335	0802637	01	S-9 pump station
G-2312	261347	0802737	01	Twenty-Six Mile Bend
G-2313	261958	0804106	01	North Everglades central
G-2314	261952	0805002	01	North Everglades west
G-2315	261958	0803421	01	North Everglades east
G-2316	255732	0803256	01	South Everglades east
G-2317	255722	0802455	01	Snake Creek Canal west
G-2318	255724	0802036	01	Snake Creek Canal east
G-2319	260843	0802839	01	Alligator Alley east
G-2320	260846	0803542	01	Alligator Alley central
G-2321	260742	0802200	01	Markham Park
G-2322	260617	0801612	01	Plantation
PB-1428	262109	0801751	01	Hillsboro Canal west
G-2323	261938	0801215	01	Hillsboro Canal east
G-2325	261938	0800752	01	Hillsboro Locks
G-2327	255829	0801448	01	Miramar east
G-2328	255918	0800918	02	Hallandale well field
G-2329	261014	0805122	01	Alligator Alley Snake Road
G-2330	260844	0804159	01	Alligator Alley west
G-2338	260532	0805036	01	Southwest Everglades
G-2340	261458	0804947	01	Northwest Everglades
G-2341	261343	0801758	01	Cypress Creek Canal west
G-2342	261348	0801220	01	Cypress Creek Canal east
G-2344	261423	0800715	01	Pompano Beach well field
G-2345	260461	0801235	01	North Dixie well field
G-2346	255958	0805222	01	South Everglades west
G-2347	260507	0800856	01	Snyder Park

The author greatly appreciates the interest and support of the South Florida Water Management District in this cooperative program. Permission and access were given to locate most of the test sites on their right-of-way. In addition, they provided stage data for the water-conservation areas and for some of the canals and construction data for selected municipal supply wells. Also, Broward County, the cities of Fort Lauderdale, Hallandale, and Pompano Beach, and the Florida Department of Transportation gave site permission and access rights. Roy Reynolds of the Broward County Water Resources Management Division assisted in location of control structures and areas of controlled drainage in Broward County. Special thanks is given to the many municipal well-field operators for providing information on well construction and specific-capacity tests of production wells.