U.S. Department of the Interior

U.S. Geological Survey

FS 2004-3128

November 2004

Review of Aquifer Storage and Recovery in the Floridan 

Aquifer System of Southern Florida

Printed on recycled paper

Introduction

Interest and activity in aquifer storage and recovery (ASR) 

in southern Florida has greatly increased during the past 10 to 

15 years. ASR wells have been drilled to the carbonate Floridan 

aquifer system at 30 sites in southern Florida, mostly by local 

municipalities or counties in coastal areas (fig. 1). The Upper 

Floridan aquifer of the Floridan aquifer system, the aquifer of 

most interest, is either being used or planned for use at 29 of 

the sites. The strategy for use of ASR in southern Florida has 

been to store excess freshwater available during the wet season 

in an aquifer and recover this water during the dry season when 

needed for supplemental drinking water supply. Additionally, 

expanded use of ASR in southern Florida has been proposed 

under the Comprehensive Everglades Restoration Plan (CERP) on a large, unprecedented scale as a cost-effective water-supply alternative that can help meet the needs 

of agricultural, municipal, and recreational 

users and be used for Everglades ecosystem 

restoration (U.S. Army Corps of Engineers 

and the South Florida Water Management 

District, 1999). Under CERP, the construction of about 330 ASR wells is proposed 

in southern Florida, each with an assumed 

pumping capacity of 5 million gallons of 

water per day during recharge (injection) 

or recovery. Currently, test wells have been 

drilled at five sites as part of the CERP 

program (fig. 1); at four of these sites, large 

diameter ASR injection wells have been 

constructed and pilot testing is planned.

Several current or potential problems with ASR in southern 

Florida have been identified, including: (1) poor recovery due 

to mixing within the aquifer; (2) issues concerning the quality of water allowed for recharge into the aquifer; and (3) the 

release, or potential for release, of water-quality constituents 

of concern, such as arsenic and radionuclides, into the stored 

water, due to the interaction between injected freshwater and the 

aquifer matrix. This study focuses only on the recovery issue. 

The Upper Floridan aquifer is continuous throughout southern 

Florida; its overlying confinement is generally good; and the 

depth to its top ranges from 500 to 1,200 feet below land surface. However, the aquifer contains brackish to saline water in 

this area, which can greatly affect the recovery of the freshwater 

recharged and stored because of mixing within the aquifer.

MONROE COUNTY

COLLIER COUNTY

PALM BEACH COUNTY HENDRY COUNTY

MANATEE COUNTY

MIAMI-DADE

COUNTY

BROWARD

COUNTY

MARTIN

COUNTY

ST. LUCIE

COUNTY

OKEECHOBEE

COUNTY

HIGHLANDS

COUNTY

GLADES

COUNTY

HARDEE

COUNTY

SARASOTA

COUNTY

DE SOTO

COUNTY

CHARLOTTE

COUNTY

LEE

COUNTY GULF OF MEXICO

ATLANTIC

OCEAN

Lake

Okeechobee

27°30 ́

27°00 ́

26°30 ́

26°00 ́

25°30 ́

25°00 ́

24°30 ́

82°00 ́ 81°30 ́ 80°00 ́

0

0

30 MILES

30 KILOMETERS

10 20

10 20

STUD

AREA

EXPLANATION

CERP

CERP

CERP

CONSTRUCTION COMPLETE—For

at least one well at a site. Circles

indicate Central Everglades

Restoration Project (CERP) sites

OPERATIONAL TESTING OR

OPERATING

EXPERIMENTAL AND INA AL AND INACTIVE

STUDY AREA BOUND

.

Figure 1. Study area and location and status of aquifer storage and recovery sites in 

the Floridan aquifer system.
Scope and Methods

The U.S. Geological Survey is conducting this study to 

inventory and compile data for existing ASR sites in southern Florida and identify various hydrogeologic, design, and 

management factors that control the recovery of freshwater 

recharged into ASR wells. Data for all wells at the 30 Floridan 

aquifer system sites were compiled into four main categories: 

(1) well identification, location, and construction data; (2) 

hydraulic test data; (3) ambient formation water-quality data; 

and (4) cycle testing data. Each cycle during testing or operation 

includes periods of recharge of freshwater, storage, and recovery that each last days or months. Cycle testing data include 

calculations of recovery efficiency.

This study has been divided into two phases, the first of 

which involves preliminary data inventory, review, and analysis 

(Reese, 2001). The second phase involves compiling additional 

ASR data (as the data become available), expanding the hydrogeologic framework, and performing a more complete comparative analysis of ASR sites.

Factors Controlling Recovery Efficiency

Recovery efficiency in this study is defined as the percentage 

of potable recharged water that is recovered during each cycle. 

Potable water has a chloride concentration less than or equal to 

250 milligrams per liter. The recovered volume in this calculation only includes water recovered prior to reaching the potable 

limit as the salinity of water increases during recovery. Recovery can continue beyond this limit, depending on operational 

considerations.

The recovery of freshwater stored in brackish- to salinewater aquifers is controlled by a wide variety of factors involving hydrogeologic conditions, well or well-field design, and 

operational management. A number of hydrogeologic factors of 

a storage zone can affect recoverability, including: (1) ambient 

salinity (defined based on chloride concentration); (2) aquifer 

permeability and its distribution, which relates to dispersive 

mixing; (3) aquifer thickness; (4) aquifer confinement; (5) 

ambient hydraulic gradient; and (6) structural setting. Important design and management factors to consider are: (1) the 

thickness and location of the storage zone within the aquifer; 

(2) the volume of injected water for each cycle; (3) the duration and frequency of cycles and cycle storage periods; (4) well 

performance problems, such as wellbore plugging and pump 

failure; and (5) multiple recharge well configurations. Generally, recovery efficiency can increase for a cycle as the volume 

of water recharged increases. Also, recovery efficiency typically 

improves with repeated cycles because much of the recharged 

water from a previous cycle is left in the aquifer, and during the 

next cycle, recharged water mixes with water having a lower 

salinity. An idealized freshwater-flushed zone (often referred to 

as a bubble) and zone of mixing at an ASR well are shown in 

figure 2.

Boynton Beach – An Example of a Successful ASR 

Site

In late 1992, cycle testing began at the Boynton Beach East 

Water Treatment Plant site near the eastern coast of Florida in 

southeastern Palm Beach County. Sixteen recharge-recovery 

cycles had been conducted by early 2000, for an average of 

about two cycles per year. Potable recovery efficiency increased 

rapidly during the first three cycles to about 50 percent per 

cycle, and recovery efficiencies for cycles 10 to 14 averaged 75 

percent. Recovery for most cycles continued past the potable 

limit until a chloride concentration of about 300 milligrams per 

liter was reached. Hydrogeologic factors at this site are favorable; the thickness of the storage zone open interval is only 105 

feet, reported transmissivity for the storage zone is moderate 

(about 9,400 square feet per day), and ambient ground-water 

salinity is also moderate (chloride concentration of 1,900 milligrams per liter). Additionally, the storage zone is located at the 

top of the Upper Floridan aquifer (fig. 3).

Results of Cycle Testing

Cycle testing has been limited to 20 of the 30 existing ASR, 

with a total of 85 cycles completed thus far. Of the remaining 10 sites, 7 require additional wells or infrastructure to be 

constructed and 3 have had testing delayed by regulatory issues, 

mechanical problems, or for other reasons. Of the 20 sites that 

have initiated cycle testing, 3 or fewer cycles have been conducted at 10 sites, even though well construction was completed 

at 9 of these in the 1990s or earlier. Another reason for limited 

cycle testing at some sites has been the lack of source water during certain years.

Potable water recovery efficiencies for 18 of the 30 sites 

were calculated, and generally, recovery efficiency improved 

with the number of cycles completed. Of the 14 sites with 3 or 

more cycles completed, 10 have had a recovery efficiency of 30 

percent or more for at least one cycle. However, of all 18 sites 

with cycle test data, 5 (about 30 percent) have not exceeded 10 

percent recovery per cycle. Low recovery at some of these sites 

is probably explained by the low number of cycles, low recharge 

volume per cycle, higher recharge water salinity, or recovery 

well beyond the potable salinity limit, which can reduce recovery on subsequent cycles. Potable water recovery efficiencies 

CONFINING UNIT

CONFINING UNIT

AQUIFER

UNINVADED

ZONE

TRANSITION

ZONE

(ZONE OF

MIXING)

FLUSHED

ZONE

FLUSHED

ZONE

CASING

UNINVADED

ZONE

TRANSITION

ZONE

(ZONE OF

MIXING)

CASING

Figure 2. Aquifer storage and recovery well in a confined aquifer 

depicting idealized flushed and transition zones created by 

recharge. Flushed zone contains mostly recharged water.
for the last cycle with data available are 

shown for 17 sites in figure 4. Recharge 

volume per cycle averaged 112 million 

gallons and ranged from 0.6 to 714 million 

gallons. Except for three sites, all of the 

sites in figure 4 use a single recharge well; 

for the other three sites, three recharge 

wells were used simultaneously for the 

last cycle, and the recovery efficiency was 

calculated using the combined volumes. 

In general, ASR wells located on the east 

coast appear to achieve greater recovery 

efficiency than those located on the west 

coast; three east coast facilities had recovery efficiencies exceeding 60 percent during their most recent cycle. However, more 

cycles have been conducted at these three 

east coast sites (six cycles or more) than at 

most of the west coast sites. 

Factors that can affect freshwater recovery vary greatly among sites. The thickness 

of the open storage zone ranges from 45 to 

452 feet over all sites. For Upper Floridan 

aquifer sites, storage zone transmissivity 

ranges from 800 to 108,000 square feet 

400

500

600

700

800

900

1,000

1,100

1,200

NATURAL

GAMMA RAY

W HIGH L HIGH

DEPTH, IN FEET BELOW LAND SURFACE

FORMATION

RESISTIVITY

FROM DEEP

INDUCTION LOG

HAWTHORN GR WTHORN 

G

R HA OUP

INTERMEDIATE

CONFINING UNIT UPPER FLORIDAN AQUIFER

AVON PARK

FORMATION

GEOLOGIC

UNIT

HYDROGEOLOGIC

UNIT

BASAL

HAWTHORN

UNIT

CEMENT

STORAGE

ZONE

NOT DETERMINED

Sandy

phosphatic

limestone

Fossiliferous

limestone

FLOW

ZONES

CASING

WELL

DESIGN

Calcareous

clay

and

siltstone

? ?

LITHOLOGY

Figure 3. Location of storage 

zone in relation to geophysical 

logs, lithology, flow zones, and 

geologic and hydrogeologic units 

for the aquifer storage and recovery well at the Boynton Beach 

East Water Treatment Plant site 

in Palm Beach County. Flow 

zones determined by flowmeter, 

fluid resistivity, and caliper logs. 

The basal Hawthorn unit could 

include the Suwannee Limestone 

in its lower part. Question mark 

signifies that the base of a unit 

was not reached.

Figure 4. Potable water recovery efficiencies for the most recent cycle for aquifer 

storage and recovery sites in southern 

Florida. All sites use one recharge well, 

except three sites (indicated) that use 

three wells simultaneously.

MONROE COUNTY

COLLIER

COUNTY

PALM BEACH

COUNTY HENDRY COUNTY

MANATEE COUNTY

MIAMI-DADE

COUNTY

BROWARD

COUNTY

MARTIN

COUNTY

ST. LUCIE

COUNTY

OKEECHOBEE

COUNTY

HIGHLANDS

COUNTY

GLADES

COUNTY

HARDEE

COUNTY

SARASOTA

COUNTY

DE SOTO

COUNTY

CHARLOTTE

COUNTY

LEE

COUNTY GULF OF MEXICO

ATLANTIC

OCEAN

Lake

Okeechobee

82°30 ́

27°30 ́

27°00 ́

26°30 ́

26°00 ́

25°30 ́

25°00 ́

24°30 ́

82°00 ́ 81°30 ́ 81°00 ́ 80°30 ́ 80°00 ́

0

0

30 MILES

30 KILOMETERS

10 20

10 20

3/23/01

(3 wells)

39%/3

EXPLANATION

STUDY

AREA

OPERATIONAL TESTING OR

OPERATING

EXPERIMENTAL AND INA AL AND INACTIVE

Percent recovery for last cycle

/ last cycle number, for 250

milligrams per liter chloride

concentration limit during

recovery

Ending date for cycle

STUDY AREA BOUND Y AREA BOUNDARY

27%/4

3%/2

68%/9

41%/3

21%/6

62%/7

26%/3

78%/6

63%/19

3%/5

35%/4

7%/7 3%/1

35%/4

7/14/04

11/10/98

8/26/02

17%/3

7/14/04

(3 wells)

10/15/01

3/11/99

8/26/03

12/29/03

1/30/80

Oct 1976

39%/2

7/28/03

0.5%/1
per day, chloride concentration of ambient formation water 

ranges from 500 to 11,000 milligrams per liter, and aquifer test 

leakance values indicate that confinement separating the storage 

zone from lower permeable zones may be limited in some areas. 

High transmissivity (greater than 30,000 to 50,000 square feet 

per day) may adversely affect recovery because it may equate to 

high dispersive mixing. Additionally, assuming vertical hydraulic conductivity is not low and depending on the ambient salinity of the storage zone, the probability of buoyancy stratification 

increases as transmissivity increases. Buoyancy stratification, 

which results in more mixing during recovery, could begin to 

occur as chloride concentration increases above 3,000 milligrams per liter. At three sites with storage zone transmissivity 

of 70,000 square feet per day or greater, recovery efficiency has 

not exceeded 10 percent for any of the three to seven cycles at 

each site. Low transmissivity can also be problematic because 

pressure buildup may restrict the rate of injection, particularly 

if multiple wells are clustered in a small area. Lower transmissivity (less than 10,000 square feet per day) has been mapped 

in the Upper Floridan aquifer in the central part of southern 

Florida around Lake Okeechobee (Ward and others, 2003). The 

majority of wells planned for the CERP ASR program are proposed for an area around the lake, and their proposed recharge 

and recovery rate of 5 million gallons per day is two to five 

times higher than the normal rate for utility-based ASR wells in 

southern Florida.

Summary

Wells have been drilled to the Floridan aquifer system for the purpose of ASR at 30 sites in southern 

Florida, and data from these wells provide a basis for the review of their hydrogeologic characteristics and 

performance. Cycle testing has been limited at a number of sites, but potable water recovery efficiencies for 

85 cycles at 18 of the 30 sites were calculated. Based on these efficiency data, several hydrogeologic and 

design factors appear to most affect the performance of ASR in the Floridan aquifer system. Performance is 

maximized when the storage zone is thin and located at the top of the Upper Floridan aquifer, and transmissivity and ambient salinity of the storage zone are moderate (less than 30,000 to 50,000 square feet per day 

and 3,000 milligrams per liter of chloride concentration, respectively). Because of the location and large 

scale of the proposed CERP ASR program for southern Florida, hydrogeologic factors, such as transmissivity, could also affect performance. Transmissivity may be too low rather than too high in a part of the CERP 

program area where many of the wells are planned.

References

Reese, R.S., 2001, Inventory and review of aquifer storage 

and recovery in southern Florida: U.S. Geological Survey 

Water Resources Investigations Report 02-4036, 56 p. 

U.S. Army Corps of Engineers and South Florida Water 

Management District, 1999, Central and Southern Florida 

Project Comprehensive Review Study: Final Integrated 

Feasibility Report and Programmatic Environment Impact 

Statement, 27 p.

Ward, W.C., Cunningham, K.J., Renken, R.A., and others, 

2003, Sequence-stratigraphic analysis of the Regional 

Observation Monitoring Program (ROMP) 29A test core 

hole and its relation to carbonate porosity and regional 

transmissivity in the Floridan aquifer system, Highlands 

County, Florida: U.S. Geological Survey Open-File Report 

03-201, 32 p. and appendixes, accessed on 9/27/04 at: 

http://infotrek.er.usgs.gov/pubs/

For more information, please contact: 

Project team leader

Ronald S. Reese

email: rsreese@usgs.gov

U.S. Geological Survey, Florida Integrated Science Center - 

Water and Restoration Studies

9100 NW 36 Street, Suite 107

Miami Fla., 33178

Contributing Scientist

Carlos A. Alvarez Zarikian

Postdoctoral Associate, email: calvarez@rsmas.miami.edu

University of Miami RSMAS-MGG

4600 Rickenbacker Causeway

Miami Fla., 33149