Prepared in cooperation with Miami-Dade County

Map of the Approximate Inland Extent of Saltwater at the 

Base of the Biscayne Aquifer in the Model Land Area of 

Miami-Dade County, Florida, 2016

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!

FKS 9

48

FKS 7

98 FKS 6

51

FKS 5

31

FKS 1

57

G–1180

22

G–3167

65

FKS 2

763

G–3976

36 G–3900

31

G–3166

150

G–1603

643

FKS 4

3,150

FKS 3

7,375

G–3342

2,390

G–1264

8,300

FKS 8

10,050

G–3855

7,960

G–3698

2,830

TPGW–9L

25.2

TPGW–8L

46.2

TPGW–7L

2,750

TPGW–6L

7,570

G–3966S

5,610

G–3946D

5,780

G–3699

10,700

TPGW–5L

12,300

TPGW–4L

15,200

TPGW–3L

28,500

TPGW–2L

31,200

TPGW–1L

29,100

SWIM well

130

TPGW–14L

27,800

TPGW–13L

36,800

TPGW–12L

27,100

TPGW–11L

25,300

TPGW–10L

26,400

ACI–MW–15

2,480

ACI–MW–09

30.8

ACI–MW–05

47.4

ACI–MW–04

48.5

ACI–MW–03

17.8

ACI–MW–16

36.9

Florida Keys 

Aqueduct 

Authority

Leisure 

City

Florida City

Wittkop Park

Newton

Redavo

Homestead 

Airforce 

Base

Naranja 

Park

Harris 

Park

Everglades 

Labor Camp

Sec34–MW–02–FS

FLORIDA

Miami-Dade

County

Study area

EXPLANATION

! Monitoring well name and chloride concentration, in milligrams per liter

Well field 

Approximate inland extent of saltwater in 2011 (Prinos and others, 2014)

Approximation

Dashed where data are insufficient

Approximate inland extent of saltwater in 2016

Approximation

Dashed where data are insufficient

G–3698

2,830

Model

Land

Area

lanaC 011–C

Card Sound

Barnes Sound

Little Card Sound

Biscayne Bay

Cooling 

canal 

system

ATLANTIC OCEAN

0 2 4 MILES

0 2 4 KILOMETERS

Scientific Investigations Map 3380

U.S. Department of the Interior

U.S. Geological Survey
Cover. Map showing the approximate extent of saltwater at the base of the Biscayne aquifer in the Model 

Land Area of Miami-Dade County, Florida, 2016. See https://doi.org/10.3133/sim3380 for map sheet.
Map of the Approximate Inland Extent 

of Saltwater at the Base of the Biscayne 

Aquifer in the Model Land Area of 

Miami-Dade County, Florida, 2016

By Scott T. Prinos 

Prepared in cooperation with Miami-Dade County

Scientific Investigations Map 3380

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

RYAN K. ZINKE, Secretary

U.S. Geological Survey

William H. Werkheiser, Acting Director

U.S. Geological Survey, Reston, Virginia: 2017

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Prinos, S.T., 2017, Map of the approximate inland extent of saltwater at the base of the Biscayne aquifer in the Model 

Land Area of Miami-Dade County, Florida, 2016: U.S. Geological Survey Scientific Investigations Map 3380, 

8-p. pamphlet, 1 sheet, https://doi.org/10.3133/sim3380.

ISSN 2329-132X (online)
iii

Acknowledgments 

The authors would like to acknowledge the organizations that provided data for the study area: 

EAS Engineering, Inc., Florida Keys Aqueduct Authority, Florida Power & Light Company, MiamiDade County, and South Florida Water Management District. Without the data provided by these 

organizations, the map in this report could not have been created.

v

Contents

Acknowledgments .......................................................................................................................................iii

Abstract ..........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Mapping the Approximate Inland Extent of the Saltwater Interface ...................................................2

Approximating the Rate of Movement of the Saltwater Interface .......................................................2

Monitoring Network Improvements ..........................................................................................................3

References Cited ...........................................................................................................................................4

Appendix 1. Estimation of Chloride Concentrations at Wells Where Conductivity Profiles 

Were Used for Monitoring..................................................................................................5

Sheet

[Available from https://doi.org/10.3133/sim3380]

1. Map of the approximate inland extent of saltwater at the base of the Biscayne

aquifer in the Model Land Area of Miami-Dade County, Florida, 2016

Conversion Factors 

SI to Inch/Pound

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2

) 247.1 acre

square kilometer (km2

) 0.3861 square mile (mi2)

Volume

liter (L) 0.2642 gallon (gal)

liter (L) 61.02 cubic inch (in3

) 

Flow rate

meter per year (m/yr) 3.281 foot per year (ft/yr) 

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

Electrical conductivity

siemens per meter (S/m) 10,000 microsiemens per centimeter 

(μS/cm)
vi

Electrical conductivity σ in microsiemens per centimeter [μS/cm] can be converted to electrical 

resistivity ρ in ohm-meters [ohm m] as follows: ρ = 10,000/σ.

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32

Datum

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C).

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L).

Abbreviations

bls below land surface

GIS geographic information system

TSEMIL time-series electromagnetic-induction log (dataset)

USGS U.S. Geological Survey 
Map of the Approximate Inland Extent of Saltwater at the 

Base of the Biscayne Aquifer in the Model Land Area of 

Miami-Dade County, Florida, 2016 

By Scott T. Prinos

Abstract 

The inland extent of saltwater at the base of the 

Biscayne aquifer in the Model Land Area of Miami-Dade 

County, Florida, was mapped in 2011. Since that time, 

the saltwater interface has continued to move inland. The 

interface is near several active well fields; therefore, an 

updated approximation of the inland extent of saltwater and 

an improved understanding of the rate of movement of the 

saltwater interface are necessary. A geographic information 

system was used to create a map using the data collected by 

the organizations that monitor water salinity in this area. An 

average rate of saltwater interface movement of 140 meters 

per year was estimated by dividing the distance between two 

monitoring wells (TPGW-7L and Sec34-MW-02-FS) by the 

travel time. The travel time was determined by estimating 

the dates of arrival of the saltwater interface at the wells and 

computing the difference. This estimate assumes that the 

interface is traveling east to west between the two monitoring 

wells. Although monitoring is spatially limited in this area 

and some of the wells are not ideally designed for salinity 

monitoring, the monitoring network in this area is improving 

in spatial distribution and most of the new wells are well 

designed for salinity monitoring. The approximation of the 

inland extent of the saltwater interface and the estimated rate 

of movement of the interface are dependent on existing data. 

Improved estimates could be obtained by installing uniformly 

designed monitoring wells in systematic transects extending 

landward of the advancing saltwater interface.

Introduction 

Seawater began intruding the Biscayne aquifer of MiamiDade County early in the 20th century because of a decline in 

the fresh groundwater level, estimated to have been 2.9 meters 

(m) below predrainage conditions near Miami (Prinos

and others, 2014). By 2011, approximately 1,200 square

kilometers (km2

) of the mainland part of the Biscayne aquifer 

were intruded by saltwater (Prinos and others, 2014). Intrusion 

of the Biscayne aquifer by saltwater is a concern because it 

can render the water unpotable in affected parts of the aquifer. 

The maximum concentration of chloride allowed in drinking 

water is 250 milligrams per liter (mg/L; U.S. Environmental 

Protection Agency, 2014), whereas saltwater-intruded parts of 

the aquifer commonly have water with chloride concentrations 

of 1,000 mg/L or greater. 

The inland extent of saltwater at the base of the Biscayne 

aquifer was last mapped by Prinos and others (2014) in 2011. 

Since that time, saltwater has continued to intrude beneath 

the Model Land Area. This area is a relatively flat and poorly 

drained wetland area in southeastern Miami-Dade County that 

is bordered on the east and south sides by Biscayne Bay, Card 

Sound, Little Card Sound, and Barnes Sound. A system of 

canals, water control structures, and levees regulate the flow 

of surface water in this area. There is an extensive system of 

cooling canals in the eastern part of this area that has been 

hypersaline at times (Hughes and others, 2010).

In the Model Land Area, the saltwater interface 

is near several active well fields; therefore, an updated 

approximation of the inland extent of saltwater and an 

improved understanding of the rate of movement of the 

saltwater interface are necessary. The U.S. Geological Survey 

(USGS), in cooperation with Miami-Dade County, mapped the 

approximate inland extent of saltwater in the Model Land Area 

in 2016 and approximated the average rate of movement of the 

saltwater interface in this area based on data collected between 

2007 and 2014. This study aligns directly with the strategic 

science direction for the Water discipline outlined in USGS 

Circular 1309 (U.S. Geological Survey, 2007) by quantifying, 

forecasting, and securing freshwater for America’s future. 

The purpose of this report is to provide a map of the saltwater 

interface (2016), an estimate of the rate of interface movement 

given the dates of arrival at two wells, and a description of the 

methodologies used to arrive at these results. The analyses and 

estimates are based on available data from existing monitoring 

wells in the Model Land Area. 
2 Map of the Approximate Inland Extent of Saltwater at the Base of the Biscayne Aquifer, Miami-Dade County, Florida, 2016

Mapping the Approximate Inland 

Extent of the Saltwater Interface

The approximate inland extent of saltwater in the 

Biscayne aquifer was determined by using (1) chloride 

concentration and specific conductance of water samples 

collected from monitoring wells, (2) water conductivity 

profiles collected in long open-interval wells, and (3) timeseries electromagnetic-induction log (TSEMIL) datasets 

collected in polyvinyl-chloride-cased monitoring wells. This 

information was provided by EAS Engineering, Inc., the 

Florida Keys Aqueduct Authority, the Florida Power & Light 

Company, the South Florida Water Management District 

(SFWMD), and the USGS. Almost all of the data provided 

by the SFWMD for this study area had been collected by the 

other four organizations, so they are mostly redundant. The 

information was entered into a geographic information system 

(GIS) for analysis and mapping. Data used to make the map 

are available as a data release (Prinos, 2017). 

Sampling, analysis, and quality assurance procedures of 

the organizations collecting salinity data in the study area vary. 

Procedures used by the Florida Power & Light Company for 

sampling and quality assurance are described in the Turkey 

Point Quality Assurance Project Plan (Florida Power & Light 

Company, 2011). These procedures are likely among the 

most stringent used by organizations collecting salinity data 

in the study area. This plan was drafted jointly by the Florida 

Department of Environmental Protection, the Florida Power 

& Light Company, and the SFWMD and was approved by 

the SFWMD. Procedures for sampling by the USGS are 

generally based on those described in the USGS field manual, 

but procedures have been modified for expediency and 

efficacy of routine, long-term saltwater intrusion monitoring 

(U.S. Geological Survey, variously dated; Lee Massey, U.S. 

Geological Survey, written commun., March 7, 2017). EAS 

Engineering, Inc., and the Florida Keys Aqueduct Authority 

base their sampling on the specifications of the Florida 

Department of Environmental Protection (Florida Department 

of Environmental Protection, 2008). To ensure the quality of 

analyzed samples, the USGS laboratory participates in the 

Branch of Quality Systems Standard Reference Sample SemiAnnual Proficiency Testing Project. EAS Engineering, Inc., 

and the Florida Power & Light Company use laboratories that 

are certified through the National Environmental Laboratory 

Accreditation Program. Participation in this accreditation 

program likely assures that sample analyses are accurate; 

however, the USGS cannot completely verify this accuracy 

without reviewing the results of the accreditation testing for 

each laboratory used. 

The approximate saltwater interface is represented by the 

1,000-mg/L isochlor at the base of the Biscayne aquifer. The 

word “approximate” is used because the spatial distribution 

of monitoring wells is generally insufficient to create a 

precise representation. The accuracy and precision of this 

approximation is best evaluated on a location-by-location 

basis, based on the available monitoring wells. The locations 

of the monitoring wells and the chloride concentration values 

are shown on the map (sheet 1, available at https://doi.

org/10.3133/sim3380). The line depicting the approximate 

inland extent of saltwater is dashed where the monitoring well 

distribution is insufficient to create a reasonably accurate and 

precise approximation. 

The TSEMIL-derived vertical profiles of bulk 

conductivity provide additional qualitative insights for 

mapping, such as detection of any influxes of conductive 

water that do not correspond to the open interval of the well 

and temporal changes in the depth of the top of the saltwater 

interface. Where water conductivity profiles were used 

for monitoring, chloride concentrations were estimated by 

using a relation based on a linear regression of the chloride 

concentration and specific conductance as described in 

appendix 1.

The majority of the monitoring wells used for this 

analysis have short open intervals (about 1.5 meters [m] or 

less), but 37 percent have open intervals of 8 to 40 m (Prinos, 

2017). The long open-interval wells are not ideal for salinity 

monitoring for the reasons summarized in Prinos (2013) and 

Prinos and Valderrama (2015), but they are the only wells 

available at some locations. 

Approximating the Rate of Movement

of the Saltwater Interface

The saltwater interface in the study area is advancing 

at an estimated average rate of 140 meters per year (m/yr). 

This estimate is based on limited data because there are few 

wells in this area where the date of arrival of the saltwater 

interface can be ascertained. Most wells were installed either 

after the saltwater interface had already passed the location 

or where the saltwater interface has not yet arrived. The 

estimate is based on data from monitoring wells Sec34-

MW-02-FS and TPGW-7L, monitored by EAS Engineering, 

Inc., and the Florida Power & Light Company, respectively. 

Data from well TPGW-7L and selected conductance profiles 

from well Sec34-MW-02-FS are available in Prinos (2017). 

Well TPGW-7L is open to the aquifer from 24 to 26 m 

below land surface (bls), which is near the depth of the base 

of the Biscayne aquifer at this location (Fish and Stewart, 

1991). The chloride concentration in water samples from 

well TPGW-7L increased from 180 to 825 mg/L between 

December 3, 2013, and March 11, 2014, and from 825 to 

1,300 mg/L between March 11, 2014, and June 9, 2014. 

Water conductance profiles were collected from well Sec34-

MW-02-FS. The maximum conductance of the profiles was 

found at a depth of about 25 m bls. Using equations 1 and 

2 (appendix 1), conductance values measured at this depth 

equate to chloride concentrations of about 190, 530, 930, and 

1,400 mg/L for November 12, 2007, January 15, 2008, April 4, 

2008, and May 15, 2008, respectively. 
Monitoring Network Improvements 3

The average rate of saltwater interface movement 

was estimated by dividing the distance between the wells 

(830 m) by the difference between the interpolated dates of 

arrival of chloride concentrations of 250 and 1,000 mg/L at 

each well. The interpolated dates of arrival at well Sec34-

MW-02-FS were November 22, 2007, and April 8, 2008, 

for concentrations of 250 and 1,000 mg/L, respectively. 

The interpolated dates of arrival at well TPGW-7L were 

December 13, 2013, and April 13, 2014, for concentrations of 

250 and 1,000 mg/L, respectively. Given these dates and the 

distance between these wells, the estimated rate of movement 

of the front is 137 m/yr based on a chloride concentration of 

250 mg/L, and the estimated rate based on a concentration of 

1,000 mg/L is 138 m/yr. These estimates can be rounded to an 

average estimate of 140 m/yr. This rate of movement was used 

to help interpolate the location of the 1,000-mg/L isochlor in 

the Model Land Area.

This estimate assumes that the direction of front 

movement is parallel to a line passing through these two well 

locations, and that the rate of front movement is constant. 

Use of this rate for interpolating the position of the saltwater 

interface elsewhere in the study area assumes that (1) effective 

porosity is uniform throughout this area, (2) direction of 

front movement is east to west, and (3) that the rate of front 

movement is the same throughout this area. Additional 

monitoring is needed to evaluate these assumptions (see 

Monitoring Network Improvements section of this report). 

Given the stated assumptions, the saltwater interface may 

move under the Newton well field by 2026. This estimate of 

future movement may be conservative because withdrawals 

from the well field may influence the rate and direction of 

travel.

Monitoring Network Improvements

Within the map, the line depicting the approximation 

of the inland extent of the saltwater interface is dashed 

near the Card Sound Road Canal and in the area around 

the C-110 Canal because there were insufficient data for 

an accurate delineation of the interface. These areas were 

previously mapped by using helicopter electromagnetic 

surveys (Fitterman and Prinos, 2012) and time-domain 

electromagnetic soundings (Fitterman and others, 2011). 

Monitoring in these areas currently consists of only a few 

wells that are too far from the expected current location of the 

interface to provide relevant information. Monitoring near the 

edge of the elongated extension of saltwater that had intruded 

along the Card Sound Road Canal (Prinos and others, 2014) is 

almost nonexistent. 

Given the rate of movement of the saltwater interface 

estimated in this investigation, the chloride concentrations 

of samples from some of the monitoring wells on the 

freshwater side of the interface may not exceed 1,000 mg/L for 

many years. Monitoring well FKS 9, for example, is 0.86 km 

from the estimated location of the saltwater interface. The 

1,000-mg/L isochlor may not arrive at this well until 2023, 

if the rate of movement of the saltwater interface proceeds at 

the average rate estimated in this study. Better estimates of 

the rates of movement are needed before 2023, particularly 

because the rate of movement may not be constant. 

Monitoring well FKS 5 is even farther from the approximated 

location of the saltwater interface than well FKS 9. The rate 

and direction of movement of the saltwater interface near well 

FKS 5 are unknown. If the rate of movement were the same 

as that between wells Sec34-MW-02-FS and TPGW-7L, the 

1,000-mg/L isochlor may not reach this well for 26 years if 

the interface moves northward, or 17 years if the interface 

moves westward. Water managers would most likely need to 

have a better understanding of the location of the saltwater 

interface, its rate of movement, and direction of movement 

than currently provided near FKS 5.

Differences in the design, placement, quality of chemical 

analyses, and type of monitoring can add uncertainty to this 

analysis. The analysis of the rate of movement of the saltwater 

interface between monitoring wells Sec34-MW-02-FS and 

TPGW-7L, for example, required a number of estimations, 

including the relation between specific conductance and 

chloride, the relation between pumped water samples and 

in situ measurements of conductance, and the conversion of 

conductance to specific conductance. These relations and 

conversions increase uncertainty. 

Some monitoring wells, such as well Sec34-MW02-FS and many of the wells monitored by the Florida Keys 

Aqueduct Authority, are designed to monitor the depth of the 

top of the saltwater interface through the collection of water 

conductivity profiles and water samples from multiple depths. 

Because these wells have long open intervals, the sample 

results may be influenced by flow within the well bore during 

sampling or under ambient conditions (Prinos, 2013; Prinos 

and Valderrama, 2015). Although several organizations base 

their sampling on the Standard Operating Procedures of the 

Florida Department of Environmental Protection, Prinos 

(2013) states that these procedures “call for sampling of long 

open-interval wells by pumping from near the top of the water 

column or top of the open interval, which could result in 

samples that are not representative of maximum salinity in the 

aquifer.” Uncertainty is also increased because some analyses 

are performed in the field as opposed to in a laboratory that 

participates in a quality assurance testing program (see the 

Mapping the Approximate Inland Extent of the Saltwater 

Interface section of this report). 

Estimates of the rate of movement of the interface could 

be improved by placing monitoring wells along a transect, 

spaced at distances that would allow timely detection of any 

variations in the rate of movement of the saltwater interface, 

and parallel to the direction of movement of the interface. If 

four or five such transects were installed in the county, the 

resulting data could be used to evaluate spatial differences in 

the rates of movement of the saltwater interface at locations 

where the interface is encroaching. Collecting TSEMIL 
4 Map of the Approximate Inland Extent of Saltwater at the Base of the Biscayne Aquifer, Miami-Dade County, Florida, 2016

datasets in wells in each transect could provide information on 

how the depth of the interface is changing. Using consistent 

monitoring methods at wells in each transect could reduce the 

uncertainty in the estimated rate of movement.

References Cited 

Fish, J.E., and Stewart, Mark, 1991, Hydrogeology of the 

surficial aquifer system, Dade County, Florida: U.S. 

Geological Survey Water-Resources Investigations Report 

90–4108, 50 p., 11 sheets.

Fitterman, D.V., Deszcz-Pan, Maria, and Prinos, S.T., 2012, 

Helicopter electromagnetic survey of the Model Land 

Area, southeastern Miami-Dade County, Florida: U.S. 

Geological Survey Open-File Report 2012–1176, 77 p., 

39 pls., accessed January 5, 2017, at https://pubs.usgs.gov/

of/2012/1176/.

Fitterman, D.V., and Prinos, S.T., 2011, Results of timedomain electromagnetic soundings in Miami-Dade and 

southern Broward Counties, Florida: U.S. Geological 

Survey Open File Report 2011–1299, 289 p., accessed 

January 5, 2017, at https://pubs.usgs.gov/of/2011/1299/.

Florida Department of Environmental Protection, 

2008, Groundwater sampling: Florida Department of 

Environmental Protection, Standard Operating Procedures, 

DEP-SOP-001/01 FS2200, 26 p., app., accessed 

February 10, 2017, at http://www.dep.state.fl.us/Water/sas/

sop/sops.htm.

Florida Power & Light Company, 2011, Quality Assurance 

Project Plan—Turkey Point Monitoring Project: Florida 

Power & Light Company, 170 p., 9 app., accessed 

February 22, 2017, at https://www.sfwmd.gov/documentsby-tag/fpltpsurvey?sort_by=title&sort_order=DESC.

Hughes, J.D., Langevin, C.D., and Brakefield-Goswami, 

Linzy, 2010, Effect of hypersaline cooling canals on aquifer 

salinization: Hydrogeology Journal, v. 18, p. 25–38.

Prinos, S.T., 2013, Saltwater intrusion in the surficial aquifer 

system of the Big Cypress Basin, southwest Florida, 

and a proposed plan for improved salinity monitoring: 

U.S. Geological Survey Open-File Report 2013–1088, 

58 p., accessed January 5, 2017, at https://pubs.usgs.gov/

of/2013/1088/.

Prinos, S.T., 2017, Data pertaining to mapping the 

approximate inland extent of saltwater in the Biscayne 

aquifer, in the Model Land Area of Miami-Dade County, 

Florida, 2016: U.S. Geological Survey data release, 

http://dx.doi.org/10.5066/F7R78CF8. 

Prinos, S.T., and Valderrama, Robert, 2015, Changes in 

the saltwater interface corresponding to the installation 

of a seepage barrier near Lake Okeechobee, Florida: 

U.S. Geological Survey Open-File Report 2014–1256, 

24 p., accessed January 5, 2017, at https://pubs.usgs.gov/

of/2014/1256/.

Prinos, S.T., Wacker, M.A., Cunningham, K.J., and Fitterman, 

D.V., 2014, Origins and delineation of saltwater intrusion 

in the Biscayne aquifer and changes in the distribution of 

saltwater in Miami-Dade County, Florida: U.S. Geological 

Survey Scientific Investigations Report 2014–5025, 101 p., 

accessed January 5, 2017, at http://dx.doi.org/10.3133/

sir20145025.

U.S. Environmental Protection Agency, 2014, Secondary 

drinking water standards: Guidance for nuisance chemicals: 

U.S. Environmental Protection Agency Report 816–f–10–

079, accessed January 26, 2011, at http://water.epa.gov/

drink/contaminants/secondarystandards.cfm.

U.S. Geological Survey, variously dated, National field manual 

for the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chaps. A1–A9, available online at http://pubs.water.

usgs.gov/twri9A.
Appendix 1 5

Appendix 1. Estimation of Chloride Concentrations at Wells Where 

Conductivity Profiles Were Used for Monitoring

At locations where water conductivity profiles were 

used for monitoring, chloride concentrations were estimated 

by using a relation based on a linear regression of the chloride 

concentration and specific conductance of 16,184 water 

samples collected between November 28, 1940, and 

September 26, 2016, from 178 monitoring sites sampled 

by the USGS in southern Florida (table 1–1). All of these 

sample results are available through the USGS National Water 

Information System website (U.S. Geological Survey, 2016). 

The relation is expressed as

cc = 0.3458sc − 176.32 (1)

where 

cc is the chloride concentration in milligrams per 

liter, and 

sc is the specific conductance in microsiemens 

per centimeter. 

Conductance was converted to specific conductance using the 

following relation (Carlson, [n.d.]).

sc = c/(1 + r(T − 25)) (2)

where 

c is the actual conductance measured in 

microsiemens per centimeter, 

T is the temperature of the sample in degrees 

Celsius, and 

r is the temperature correction coefficient for 

the sample. 

The TSEMIL-derived vertical profiles of bulk 

conductivity provide additional qualitative insights for 

mapping, such as detection of any influxes of conductive 

water that do not correspond to the open interval of the well 

and temporal changes in the depth of the top of the saltwater 

interface.

The majority of the monitoring wells used for this 

analysis have short open intervals (about 1.5 meters [m] or 

less), but 37 percent have open intervals of 8 to 40 m (Prinos, 

2017). The long open-interval wells are not ideal for salinity 

monitoring for the reasons summarized in Prinos (2013) and 

Prinos and Valderrama (2015), but they are the only wells 

available at some locations. 

References Cited 

Carlson, Glenn, [n.d.], Specific conductance as an output for 

conductivity readings: In-Situ Inc., Technical Note 9, 2 p., 

accessed March 6, 2017, at https://in-situ.com/wp-content/

uploads/2015/01/Specific-Conductance-as-an-Output-Unitfor-Conductivity-Readings-Tech-Note.pdf.

Prinos, S.T., 2013, Saltwater intrusion in the surficial aquifer 

system of the Big Cypress Basin, southwest Florida, 

and a proposed plan for improved salinity monitoring: 

U.S. Geological Survey Open-File Report 2013–1088, 

58 p., accessed January 5, 2017, at https://pubs.usgs.gov/

of/2013/1088/.

Prinos, S.T., 2017, Data pertaining to mapping the 

approximate inland extent of saltwater in the Biscayne 

aquifer, in the Model Land Area of Miami-Dade County, 

Florida, 2016: U.S. Geological Survey data release, 

http://dx.doi.org/10.5066/F7R78CF8. 

Prinos, S.T., and Valderrama, Robert, 2015, Changes in 

the saltwater interface corresponding to the installation 

of a seepage barrier near Lake Okeechobee, Florida: 

U.S. Geological Survey Open-File Report 2014–1256, 

24 p., accessed January 5, 2017, at https://pubs.usgs.gov/

of/2014/1256/.

U.S. Geological Survey, 2016, National Water Information 

System—Web interface, accessed September 28, 2016, at 

http://dx.doi.org/10.5066/F7P55KJN.

Appendix 1
6 Map of the Approximate Inland Extent of Saltwater at the Base of the Biscayne Aquifer, Miami-Dade County, Florida, 2016

Table 1–1. Listing of U.S. Geological Survey monitoring sites in southern Florida from which water samples were collected to evaluate 

specific conductance and chloride concentration.

[USGS, U.S. Geological Survey]

USGS station 

identifier Site name

262313080044401 PB -1457

262209080044702 PB -1669

261100080140401 G -1212

261122080083401 G -1232

260547080105801 G -2352

260920080092201 G -2898

260551080111901 G -2957

261740080054101 G -2893

255916080090401 G -1435

255910080085802 G -2294

255919080091202 G -2409

255919080091203 G -2410

255936080091701 G -2477

255936080091702 G -2478

255916080092001 G -2965

260037080100700 Hollywood Canal at Hollywood Blvd, 

Hollywood, FL

260104080101300 Hollywood Canal at Johnson St, Hollywood, 

FL

260225080095800 Hollywood Canal at N29 Ave, Hollywood, 

FL

260212080112500 Hollywood Canal at N46 Ave, Hollywood, 

FL

260132080094900 Hollywood Canal at Taft St, Hollywood, FL

260041080093101 G -2425

260041080093102 G -2426

260120080093401 G -2441

260155080092002 G -2612

260026080095801 G -2956

254943080121501 F - 45

254841080164401 G - 571

255350080105801 G - 894

254107080165201 G - 896

254201080173001 G - 901

254106080174601 G -1009B

252947080235301 G -1180

254813080161501 G -1351

254833080155801 G -1354

255222080123001 G -3224

254457080160301 G -3229

254946080172601 G -3250

252714080260901 G-3976

USGS station 

identifier Site name

255453080110801 G-3978

254601080150301 G-3977

254156080172101 G -3607

252814080244101 G -3698

252652080244301 G -3699

252650080252701 G -3855

253253080221201 G -3885

253527080195401 G -3886

253924080174601 G -3887A

253924080174602 G -3887B

254542080145901 G -3888A

254542080145902 G -3888B

254542080145903 G -3888C

253948080250701 G -3897

254152080282601 G -3898

253419080223701 G -3899

252718080264901 G -3900

252506080300601 G -3901

252431080261001 G -3946D

252431080261002 G -3946S

255011080124501 G -3947

255515080103601 G -3948D

255515080103602 G -3948S

255733080195601 G -3949D

255733080195602 G -3949I

255733080195603 G -3949S

254824080155301 G -3964

254500080162801 G -3965

252719080253601 G -3966D

252719080253602 G -3966S

253335080213501 G -3967

255315080111501 F - 279

254828080161501 G - 354

254335080170501 G - 432

254855080163701 G - 548

253652080183701 G - 939

253202080232601 G -3162

253831080180204 G -3313C

253831080180206 G -3313E

255358080114101 G -3601

255116080120601 G -3602
Appendix 1 7

Table 1–1. Listing of U.S. Geological Survey monitoring sites in southern Florida from which water samples were collected to evaluate 

specific conductance and chloride concentration.—Continued

[USGS, U.S. Geological Survey]

USGS station 

identifier Site name

254908080125201 G -3603

254722080152201 G -3604

254629080143101 G -3605

254341080174001 G -3606

254108080170601 G -3608

254005080171601 G -3609

253819080183201 G -3610

253710080184701 G -3611

253457080195501 G -3612

253024080231001 G -3615

253027080234701 G -3700

253214080224601 G -3701

253334080213601 G -3702

254822080125501 G -3704

255625080094901 G -3705

261302081473901 C - 489

261156081475801 C - 516

261002081483701 C - 525

261018081484101 C - 526

261200081483001 C - 528

260549081441901 C - 600

261802081354801 C - 688

261347081351201 C - 953

261620081464402 C -1004R

261604081480901 C -1059

261311081480101 C -1061

260137081375901 C -1063

262228081361902 C -1080

261403080070801 G -2149

260342080115902 G -2264

261446080062801 G -2445

261724080054603 G -2693

260242080101101 G -2697

261643080055901 G -2752

261740080054101 G -2893

261304080072501 G -2896

261030080083301 G -2897

260804080092701 G -2899

260325080113901 G -2900

260638080104801 G -2902

255843080090901 G -2903

USGS station 

identifier Site name

260534080110801 G -2904

262839081503100 L - 735

262022081464201 L - 738

263532081592202 L -1136

263813081552801 L -2640

263819081585801 L -2701

263955082083102 L -2820

263117082051002 L -2821

264053081572501 L -4820

262513081472002 L -5668R

261926081454702 L -5745R

264123080053801 PB - 809

263044080035102 PB -1195

262755080040101 PB -1707

262803080041101 PB -1714

263453080031501 PB -1717

263633080031401 PB -1723

265550080070701 PB -1732

265611080080201 PB -1733

265006081042502 GL - 334I

265006081042501 GL - 334S

265006081042503 GL - 334D

264912081024602 GL -332S

264912081024601 GL -332

264843080591502 GL - 333I

264843080591501 GL - 333S

264843080591503 GL - 333D

264532080545902 HE -1145S

264532080545901 HE -1145

264343080511601 PB -1843S

264343080511602 PB -1843I

264343080511603 PB -1843D

264154080480302 PB -1822S

264154080480301 PB -1822

264050080435502 PB -1842I

264050080435501 PB -1842S

264050080435503 PB -1842D

264814080414302 PB -1819S

264814080414301 PB -1819

264926080394503 PB -1848D

264930080394703 PB -1847D
8 Map of the Approximate Inland Extent of Saltwater at the Base of the Biscayne Aquifer, Miami-Dade County, Florida, 2016

Table 1–1. Listing of U.S. Geological Survey monitoring sites in southern Florida from which water samples were collected to evaluate 

specific conductance and chloride concentration.—Continued

[USGS, U.S. Geological Survey]

USGS station 

identifier Site name

265138080375802 PB -1818S

265138080375801 PB -1818

265142080374202 PB -1817S

265142080374201 PB -1817

265208080373902 PB -1845I

265208080373901 PB -1845S

265208080373903 PB -1845D

265200080373101 PB -1846S

265428080364502 PB -1816S

USGS station 

identifier Site name

265428080364501 PB -1816

265519080364902 PB -1815S

265519080364901 PB -1815

265701080363103 PB -1844D

265701080363102 PB -1844I

265701080363101 PB -1844S

265839080365202 M -1369I

265839080365201 M -1369D

For more information about this publication, contact:

Director, Caribbean-Florida Water Science Center

U.S. Geological Survey

4446 Pet Lane, Suite 108

Lutz, FL 33559

(813) 498-5000

Or visit the USGS Caribbean-Florida Water Science Center website at:

https://fl.water.usgs.gov

Publishing support provided by

Lafayette Publishing Service Center
 
Prinos—Map of the Approximate Inland Extent of Saltwater at the Base of the Biscayne Aquifer, Miami-Dade County, Florida, 2016—SIM 3380

ISSN 2329-132X (online)

https://doi.org/10.3133/sim3380