U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3126

October 2006

The U.S. Geological Survey Greater Everglades Priority Ecosystems Science Initiative

Review of Aquifer Storage and Recovery Performance in the 

Upper Floridan Aquifer in Southern Florida

Printed on recycled paper

Introduction

Interest and activity in aquifer 

storage and recovery (ASR) in southern 

Florida has increased greatly 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 located in coastal areas (fig. 1). The 

primary storage zone at these sites is 

contained within the brackish to saline 

Upper Floridan aquifer of the Floridan 

aquifer system. The strategy for use of 

ASR in southern Florida is to store excess 

freshwater available during the wet season in an aquifer and recover it during the 

dry season when needed for supplemental 

water supply. Each ASR cycle is defined 

by three periods: recharge, storage, and 

recovery.

This fact sheet summarizes some of 

the findings of a second phase retrospective assessment of existing ASR facilities 

and sites (Reese and Alvarez-Zarikian, 

2006, in press) and updates information 

and data from the first phase (Reese, 

2002). The purpose of this investigation 

is to compile and synthesize data from 

existing ASR sites in southern Florida 

and identify specific hydrogeologic, 

design, and management factors that control the recovery of freshwater recharged 

into ASR wells. Reese and AlvarezZarikian (2006, in press) provide a full 

evaluation of performance at each site 

and an updated (2004 ASR cycle data) 

comparative analysis of all ASR sites in 

the Upper Floridan aquifer.

Results of Cycle Testing and 

Performance

The primary measure used to evaluate ASR site performance in southern 

Florida is the potable water per-cycle 

recovery efficiency. This measure, 

calculated for 18 sites, is defined as the 

percentage of the volume of freshwater recharged that is recovered prior to 

recovered water chloride concentration 

exceeding 250 mg/L. 

By the end of 2004, many utilityoperated ASR facilities with constructed 

wells have experienced cycle testing or 

operational delays caused by unresolved 

regulatory issues, mechanical problems, such as pump failure, inadequate 

source-water supply, or other reasons. 

Although construction began at 21 sites 

in the 1990s or earlier, only 6 sites had 

conducted more than 6 cycles by the end 

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

Floridan aquifer system.
of 2004. Five of ten sites with wells constructed in the 1990s have conducted only 

three cycles or less, and two others have 

not conducted any cycle testing. 

Per-cycle potable water recovery 

efficiencies vary widely, from 0 to 

94 percent. High potable efficiency on 

a per cycle basis can be associated with 

water banking—an operational approach 

in which a large volume of water is 

recharged during an initial cycle. This 

process flushes out the aquifer around 

the well and can build up a temporary 

buffer zone that may increase recovery 

efficiency substantially during subsequent cycles conducted with much lower 

recharge volumes.

A comparison of cumulative 

recharge volume and elapsed time since 

the beginning of cycle testing for all sites 

illustrates there are large differences in 

the overall rate of recharge (fig. 2A). 

Elapsed time was calculated at the end 

of each cycle. A high overall recharge 

rate (greater than 300 million gallons per 

year) can improve recovery efficiency 

because of the water-banking effect. 

Cumulative potable recovery efficiencies 

display substantially less variability than 

per-cycle recovery efficiencies (fig. 2B). 

Using cumulative potable recovery 

efficiencies, the relative performance for 

15 of the 30 sites was determined by arbitrarily grouping performance into “low” 

(0 to 20 percent cumulative recovery), 

“medium” (20 to 40 percent ) and “high” 

(greater than 40 percent) categories 

(fig. 2B); 3 sites were rated high, 6 were 

rated medium, and 6 were rated low. 

Fifteen sites could not be categorized due 

to limited data and/or no cycle testing. 

The performance of all sites rated 

was compared with hydrogeologic and 

well design factors: storage zone thickness, transmissivity, ambient chloride 

concentration (correlated with salinity), 

and the aquifer thickness extending above 

the storage zone. Respective threshold 

values of 150 ft, 30,000 ft2/d, 2,500 mg/L, 

and 50 ft, respectively, were chosen for 

these factors to represent the approximate 

values above which recovery efficiency 

could be adversely affected.

Correlation of the performance ratings with the number of factors exceeding their respective threshold value is 

evident. As the ratings decrease from 

high to low, the number of sites with two 

or more factors that exceed threshold 

values increases. The best correlation is 

found with the transmissivity and ambient chloride concentration factors, but 

some correlation also is indicated with 

the thickness of the storage zone.

Long intercycle or storage periods also may adversely affect recovery 

efficiency, particularly among southeastern Florida sites. Here, the Upper 

Floridan aquifer has higher ambient salinity, higher apparent vertical hydraulic 

conductivity, and more sites with storage 

zones that lie 50 ft or more below the top 

of the aquifer. Because of the potential 

for enhanced vertical hydraulic conductivity in the upper part of the Upper Floridan aquifer in the southeastern coastal 

area, upward migration of fresh recharge 

water during long storage or intercycle 

periods could occur, resulting in diminished recovery efficiency.

References

Reese, R.S., 2002, Inventory and review 

of aquifer storage and recovery in 

southern Florida: U.S. Geological 

Survey Water-Resources Investigations 

Report 02-4036, 56 p. 

Reese, R.S. and Alvarez-Zarikian, C.A., 

2006 (in press), Hydrogeology and 

aquifer storage and recovery performance in the Upper Floridan aquifer, 

southern Florida, U.S. Geological Survey, Scientific Investigations Report 

06-5239, 73 p., 2 app.

Author—Ronald S. Reese, USGS Florida 

Integrated Science Center—Ft. Lauderdale 

rsreese@usgs.gov

Figure 2. Comparisons of (A) cumulative recharge volume and time since the beginnng 

of cycle testing, and (B) cumulative potable water recovery efficiencies for sites with at 

least three cycles (including test cycles). 

A

B