Specific Conductance

Chapter 6.3 of

Section A, National Field Manual for the Collection of Water-Quality Data

Book 9, Handbooks for Water-Resources Investigations 

Techniques and Methods 9–A6.3

Supersedes USGS Techniques of Water-Resources Investigations,

Book 9, Chapter A6.3, Version 1.2

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photograph of researcher measuring specific conductance, pH, and temperature by using a 

flow-through cell to isolate the water from the atmosphere and preserve measurement integrity, Red 

River Basin, New Mexico. Photograph by James Ball, U.S. Geological Survey.
Specific Conductance

By U.S. Geological Survey

Chapter 6.3 of

Section A, National Field Manual for the Collection of Water-Quality Data

Book 9, Handbooks for Water-Resources Investigations

Techniques and Methods 9–A6.3

Supersedes USGS Techniques of Water-Resources Investigations, 

Book 9, Chapter A6.3, Version 1.2

U.S. Department of the Interior

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

DAVID BERNHARDT, Acting Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia 

First release: April 1998, online as Techniques of Water-Resources Investigations 

(TWRI), book 9, chapter A6.3, version 1.0 

Revised: August 2005, online as TWRI, book 9, chapter A6.3, version 1.2 

Revised: February 2019, online as Techniques and Methods, book 9, 

chapter A6.3

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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:

U.S. Geological Survey, 2019, Specific conductance: U.S. Geological Survey Techniques and Methods, book 9, chap. 

A6.3, 15 p., https://doi.org/10.3133/tm9A6.3. [Supersedes USGS Techniques of Water-Resources Investigations, book 

9, chap. A6.3, version 1.2.]

ISSN 2328-7055 (online)
iii

Contents

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

1.0 Introduction .............................................................................................................................................1

1.1 Overview of Specific Conductance............................................................................................2

2.0 Equipment and Supplies........................................................................................................................3

2.1 Electrical Conductivity Cells and Specific Conductance Meters..........................................3

2.2 Equipment Maintenance ..............................................................................................................4

2.2.1 Conductivity Probe Cleaning, Storage, and Maintenance .........................................4

3.0 Calibration................................................................................................................................................5

3.1 One-Point Calibration—Determination of the Cell Constant..................................................5

3.2 Multipoint Calibration ...................................................................................................................6

3.3 Meter Calibration Procedure.......................................................................................................6

4.0 Measurement of Specific Conductance.............................................................................................8

4.1 Measurement of Specific Conductance in Surface Water....................................................8

4.1.1 In Situ Measurement of Specific Conductance in Surface Water............................8

4.1.2 Measurement of Specific Conductance on a Subsample from Surface 

Water................................................................................................................................9

4.2 Measurement of Specific Conductance in Groundwater.....................................................10

4.2.1 Measurement of Specific Conductance in a Well .....................................................10

4.2.2 Measurement of Specific Conductance on a Subsample from a Well ..................11

4.3 Measurement of Specific Conductance of a Water Sample with Low or High pH .........12

4.3.1 Measurement of Specific Conductance of a Water Sample 

with Low pH (<4)...........................................................................................................12

4.3.2 Measurement of Specific Conductance of a Water Sample 

with High pH (>11) ........................................................................................................12

5.0 Troubleshooting ....................................................................................................................................12

6.0 Reporting Specific Conductance in Natural Waters ......................................................................12

6.1 Uncertainty in Measurements of Specific Conductance .....................................................12

7.0 Applications of Specific Conductance in Surface Water and Groundwater .............................13

Acknowledgments.......................................................................................................................................14

References Cited..........................................................................................................................................14

Figure

6.3–1. Diagram showing general guidelines for selecting an electrical conductivity

probe with the optimum cell constant ...............................................................................4

Tables

6.3–1. Equipment and supplies used to measure specific conductance in the field ............3

6.3–2. Electrical conductivity of molality-based primary KCl standards .................................6

6.3–3. Troubleshooting guide for measurements of specific conductance..........................13
iv

Conversion Factors

International System of Units to U.S. customary units

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

Volume

cubic centimeter (cm3

) 0.06102 cubic inch (in3)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound, avoirdupois (lb)

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

°F=(1.8×°C)+32

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

at 25 °C). Siemens per centimeter are the equivalent of mhos per centimeter.

Molality of a solution is the number of moles (mol) of a constituent per kilogram (kg) of solution. 

Units of molality are reported in mol/kg.

Abbreviations and Symbols

ABS acrylonitrile butadiene styrene

ASR Analytical Services Request

cm centimeter

DIW quality-assured deionized water with resistance greater than or equal to 18 

megaohms (MΩ)

EDI equal-discharge increment, isokinetic sampling method

EWI equal-width increment, isokinetic sampling method

G electrical conductance 

HIF Hydrologic Instrumentation Facility at Stennis Space Center, Mississippi (USGS)

L liter

m molality

μS/cm microsiemen per centimeter

mol/kg mole per kilogram

NFM National Field Manual for the Collection of Water-Quality Data (USGS)

NFSS National Field Supply Service, also referred to as “One Stop” (USGS)

NIST National Institute of Standards and Technology

NWIS National Water Information System (USGS)

NWQL National Water Quality Laboratory (USGS)
v

PCFF personal computing field form

PVDF polyvinylidene fluoride

QSB Quality Systems Branch (USGS) R electrical resistance

SOP standard operating procedure

SRS standard reference sample

TDS total dissolved solids

USGS U.S. Geological Survey

WMAWater Mission Area (USGS)

κ electrical conductivity > greater than < less than ≤ less than or equal to MΩ megaohm Ω ohm α temperature-compensation factor

Chemical Formulas 

CO

2

 carbon dioxide

H

2

O water

HCl hydrochloric acid 

HNO

3

 nitric acid 

KCl potassium chloride

NaCl sodium chloride
vi

Requirements and Recommendations

As used in the U.S. Geological Survey (USGS) “National Field Manual for the Collection 

of Water-Quality Data” (NFM), the terms “required” and “recommended” have the USGSspecific meanings described below:

• The terms “require,” “required,” and “requirements” in reference to USGS protocols 

indicate that USGS Water Mission Area (WMA) policy has been established on the 

basis of research or consensus of the technical staff, and has been reviewed by waterquality specialists and other professionals having the appropriate expertise. Technical 

memorandums and other documents that define USGS WMA policy are cited in the 

NFM. USGS field personnel are instructed to use required equipment and procedures 

as described in the NFM. Departure from or modifications to stipulated requirements, 

if necessary for accomplishing specific data-quality requirements or study objectives, 

must be independently quality assured and documented (Office of Water Quality 

Technical Memorandum 2002.13—U.S. Geological Survey, 2002). 

• The terms “recommend,” “recommended,” and “recommendation” indicate that, on 

the basis of research or consensus, there are several acceptable alternatives to a given 

procedure or equipment selection in the NFM. Relevant technical memorandums and 

publications pertinent to such recommendations are cited in the NFM to the extent 

that such documents are available. Specific requirements, data-quality objectives, or 

other constraints of a project may affect the choice of recommended equipment or 

procedures. Selection from among the recommended alternatives should be based on 

referenced research and sound field judgment, and reasons for the selection must be 

documented. Departures from or modifications to the recommended procedures must 

be independently quality assured and documented (Office of Water Quality Technical 

Memorandum 2002.13—U.S. Geological Survey, 2002).
Chapter 6.3. Specific Conductance

By U.S. Geological Survey

Abstract

The “National Field Manual for the Collection of WaterQuality Data” (NFM) provides guidelines and procedures for 

U.S. Geological Survey (USGS) personnel who collect data 

used to assess the quality of the Nation’s surface-water and 

groundwater resources. This chapter, NFM A6.3, provides 

guidance and protocols for the measurement of specific conductance of a water sample, which include the scientific basis 

of the measurement, selection and maintenance of equipment, 

calibration, troubleshooting, and procedures for measurement 

and reporting. It updates and supersedes USGS Techniques 

of Water-Resources Investigations, book 9, chapter A6.3, 

version 1.2, by D.B. Radtke, J.V. Davis, and F.D. Wilde.

 Specific conductance is routinely measured when water 

samples are collected, is often measured continually at USGS 

streamgages, and is a parameter regularly measured during 

laboratory and field experiments. The field method for measuring specific conductance described in this chapter is applicable 

to most natural waters.

Before 2017, the NFM chapters were released in the 

USGS Techniques of Water-Resources Investigations series. 

Effective in 2018, new and revised NFM chapters are being 

released in the USGS Techniques and Methods series; this 

series change does not affect the content and format of the 

NFM. More information is in the general introduction to 

the NFM (USGS Techniques and Methods, book 9, chapter A0) at https://doi.org/10.3133/tm9A0. The authoritative current versions of NFM chapters are available in the 

USGS Publications Warehouse at https://pubs.er.usgs.gov. 

Comments, questions, and suggestions related to the NFM can 

be addressed to nfm@usgs.gov. 

1.0 Introduction

The “National Field Manual for the Collection of WaterQuality Data” (NFM) is the official and citable protocol for 

the collection of water-quality data by the Water Mission Area 

(WMA) of the U.S. Geological Survey (USGS). The NFM 

provides guidelines and procedures for USGS personnel who 

collect data for water quality in surface water and groundwater, with detailed, comprehensive, and citable procedures. 

National USGS program and project personnel who 

collect water-quality data, as well as those in USGS Water 

Science Centers and including those conducting projects supported by the USGS Cooperative program, are mandated to 

use protocols provided in the NFM (USGS Office of WaterQuality Technical Memorandum 2002.13—U.S. Geological 

Survey, 2002). Formal training, as provided in the USGS class 

“Field Water-Quality Methods for Groundwater and Surface 

Water,” and field apprenticeships supplement the information 

provided in the NFM and are needed to collect unbiased, highquality data.

The USGS National Field Manual provides detailed, 

comprehensive, and citable procedures for monitoring the 

quality of surface water and groundwater. Formal training 

and field apprenticeships supplement the information 

provided in the NFM.

Chapter A6.3 of the NFM provides guidance and protocols for the measurement of specific conductance of a water 

sample, which may be applied in both laboratory and field 

settings. Specific conductance, also called electrical conductivity, is a water-quality property whose value is proportional 

to the collective concentration of ions in solution. The specific 

conductance measurement depends on the concentration of 

ions and the temperature of the solution. The measurement is 

straightforward and precise with many environmental applications. Specific conductance is routinely measured when water 

samples are collected, is often measured continually at USGS 

streamgages, and is regularly measured during laboratory and 

field experiments. 

This chapter updates and supersedes USGS Techniques of Water-Resources Investigations, book 9, chapter 

A6.3, version 1.2 (Radtke and others, 2005). It covers the 

physical basis for measurement of specific conductance in 

aqueous solutions, as well as factors that affect the measurement, terminology, method protocols, and applications. The 

field method described in this chapter is applicable to most 

natural waters.
2 Chapter A6.3. Specific Conductance

Before 2017, the USGS NFM chapters were released 

in the USGS Techniques of Water-Resources Investigations 

series. Effective in 2018, new and revised NFM chapters 

are being released in the USGS Techniques and Methods 

series; this series change does not affect the content and 

format of the NFM. More information is in the general 

introduction to the NFM (USGS Techniques and Methods, 

book 9, chapter A0—U.S. Geological Survey, 2018) at 

https://doi.org/10.3133/tm9A0. The authoritative current 

versions of NFM chapters are available in the USGS 

Publications Warehouse at https://pubs.er.usgs.gov. 

Comments, questions, and suggestions related to the NFM can 

be addressed to nfm@usgs.gov.

1.1 Overview of Specific Conductance

Specific conductance is an indirect measure of the collective concentration of dissolved ions in solution, and is defined 

as the electrical conductance of 1 cubic centimeter (cm3) of a 

solution at 25 degrees Celsius (°C) (Hem, 1982). The terms 

“specific conductance,” “specific electrical conductance,” and 

“electrical conductivity” have been used interchangeably in 

the literature to report the same measurement. Because the 

term “electrical conductivity” is not always referenced to a 

standard temperature, the measurement or reference temperature must be reported with this parameter. The USGS National 

Water Information System (NWIS) reports the measurement 

of electrical conductance as specific conductance at 25 °C, 

meaning that at any temperature for which the measurement 

is made, the value is corrected to what it would be at 25 oC. 

The term “specific conductance” is correctly defined as the 

electrical conductance of 1 cm3 of a solution at 25 °C. If the 

electrical conductance is measured at another temperature, the 

value is corrected to what it would be at 25 °C and reported as 

specific conductance at 25 °C. Most modern specific conductance meters are temperature compensated and report the 

corrected value automatically.

The term “specific conductance” is correctly defined as the 

electrical conductance of 1 cubic centimeter of a solution at 

25 °C. If the electrical conductance is measured at another 

temperature, the value is corrected to what it would be at 

25 °C and reported as specific conductance at 25 °C.

In aqueous solutions, electrical conductance (G, measured 

in siemens [S]) is the inverse of electrical resistance (R, 

measured in ohms [Ω]), and is the capacity of water to conduct 

an electric current as a result of the movement of ions through 

the solution. Electrical conductivity (κ) is a measure of the 

electrical conductance (G) of a substance normalized to a unit 

length and cross-sectional area.

The electrical conductivity of a solution can be determined by using the following equation:

 = K G cell (1)

where Kcell is the cell constant (in units of cm-1). The cell constant is the ratio of the distance between two electrode plates 

(d) and their area (A). The units of electrical conductivity are 

siemens per centimeter (S/cm), which is the equivalent of 

mhos per centimeter (mhos/cm). Most values reported prior to 

1971 were in units of mhos per centimeter.

Electrical conductivity increases by 0.5 to 3 percent per 

degree Celsius and varies depending on the ionic species 

present (Robinson and Stokes, 1970; McCleskey, 2013). For 

natural waters, conductometric measurements are typically 

used to estimate the concentrations of total dissolved solids 

(TDS); therefore, the electrical conductivity is reported at 

25 °C (κ25 °C, which is equivalent to specific conductance), to 

facilitate this estimation of TDS by removing the effects of 

temperature. The value of κ25 °C is typically calculated by using 

the following equation:

κ

κ

α 25 1 25 ° = + − ° C ( ) t C (2)

where α is the temperature-compensation factor and t is the 

measured temperature in degrees Celsius. Modern specific 

conductance field meters typically have preprogrammed 

temperature-compensation factors (α) and report specific 

conductance (or electrical conductivity) at 25 °C (κ25 °C). 

Most specific conductance meters utilize either linear 

(0.019–0.020 per °C) or nonlinear (International Organization for Standardization, 1985) temperature-compensation 

algorithms that are applicable for most natural waters. The 

temperature compensation used is likely described in the 

meter’s manual or can be determined by using standard 

solutions and the method described by McCleskey (2013). 

Conductance and temperature can be measured accurately 

with modern instrumentation, and temperature compensation 

is typically accurate to ±5 percent for water in the range from 

5 to 35 oC and whose pH is between 4 and 11. For low-pH 

(pH <4) waters, using the standard temperature-compensation 

factors can result in κ25 °C errors as large as 50 percent, because 

the transport properties of the hydrogen ion are different from 

those of most other ions, and the hydrogen ion contributes substantially to the electrical conductance at low pH (McCleskey, 

2013). For low-pH waters, temperature corrections may 

represent the largest source of error. A temperature-compensation method applicable to low-pH waters is described in 

section 4.3 below and by McCleskey (2013). No temperaturecompensation method is available for waters with pH greater 

than 11; therefore, the specific conductance in high-pH waters 

should be checked by measuring at ambient temperature and 
2.0 Equipment and Supplies 3

then again at 25 °C. Additional sources of uncertainty when 

measuring specific conductance include calibration, preparation of standard solutions, fouling or contamination of the 

conductivity cell, and improper maintenance of the specific 

conductance meter and probe. The method described here is 

intended to produce accurate and precise specific conductance 

measurements over a wide range of solution composition, 

pH, and temperature. The USGS typically reports the electrical conductivity of water as specific conductance in units of 

microsiemens per centimeter (μS/cm) at 25 °C.

The USGS typically reports the electrical conductivity of 

water as specific conductance in units of microsiemens per 

centimeter (μS/cm) at 25 °C.

2.0 Equipment and Supplies

High-quality specific conductance meters, including 

multiparameter sondes, are available commercially. Most 

modern specific conductance meters have built-in temperature 

compensation and are accurate (typically within ±5 percent) 

for waters with a pH between 4 and 11 and in the temperature 

range from 5 to 35 °C.

This section provides detailed information on the measurement of specific conductance that is applicable to most 

meters. Users must be familiar with the instructions provided 

by the manufacturer to develop a standard operating procedure (SOP) for calibration and measurement for each meter. 

The SOP should combine the requirements of this chapter of 

the NFM with the recommendations of the manufacturer to 

standardize instrument operations for users. Every specific 

conductance meter should be accompanied by a log for recording calibrations, cell constants, and repairs. Typical supplies 

used for field measurement of specific conductance are listed 

in table 6.3–1.

Most modern specific conductance meters have built-in 

temperature compensation and are accurate (typically 

within ±5 percent) for waters with a pH between 4 and 11 

and in the temperature range from 5 to 35 °C.

2.1 Electrical Conductivity Cells and Specific

Conductance Meters

There are several types of conductivity cells. A dipstyle conductivity cell is integrated into a probe, is adaptable 

to many measurement situations, and is commonly used in 

modern field specific conductance meters and multiparameter 

Table 6.3–1. Equipment and supplies used to measure specific 

conductance in the field.

[Modify this list to meet the specific needs of the field effort]

Equipment and supplies

• Specific conductance meter with probe, thermistor, and builtin temperature compensation

• Instruction manual

• Log book (physical or electronic) for recording cell constant, 

calibrations, maintenance, and repairs

• Specific conductance standards

• Deionized water for rinsing

• Flow-through cell

• Paper tissue for cleaning and drying

• Disposable laboratory gloves and glasses

• Flasks or beakers

• Waste-disposal container

• Multiparameter sonde sensor guard and calibration cup

• Spare electrical conductivity probe

• Spare batteries

sondes. Probes containing dip conductivity cells are straightforward to use as they are immersed in the water during 

measurement, can be used in flowing or static waters, and are 

relatively easy to clean and maintain. Other less commonly 

used conductivity cells include a cup with built-in electrodes 

that hold the sample during measurement and a flow-through 

conductivity cell that is connected to a fluid line that maintains 

a closed system during measurement. In addition to the cell 

type, the material used in the cell body (epoxy or plastic—for 

example, acrylonitrile butadiene styrene (ABS) or polyvinylidene fluoride [PVDF]), stainless steel, or Pyrex glass) and 

electrodes (graphite, platinum, or platinum-iridium) should 

be considered when selecting equipment. Probes constructed 

of epoxy, plastic, or stainless steel with graphite electrodes 

are well suited for field use, whereas Pyrex glass probes with 

platinum-iridium electrodes are more fragile and better suited 

for laboratory use. Modern conductivity cells generally contain thermistors used for automatic temperature compensation. 

Thermistors should be checked on a regular basis to assure 

optimum performance; malfunctioning thermistors will produce erroneous specific conductance values. Because probes 

are used more commonly for field measurements, this chapter 

focuses on their use; however, similar procedures and criteria 

should be used when using conductivity cups or flow-through 

conductivity cells.

Specific conductance meters have an optimal range for 

measurement of conductance; for modern meters, this range 

can be large because of built-in auto-ranging capabilities. 

Manufacturer’s recommendations for the appropriate range 
4 Chapter A6.3. Specific Conductance

of each meter should be followed, although most field meters 

in use today have auto-ranging capability. Also, a conductivity probe with a suitable cell constant for the types of waters 

being measured should be used. The approximate ranges of 

specific conductance for a variety of water types with the corresponding cell constants that would most likely produce accurate results are shown in figure 6.3–1. The user should check 

the meter specifications to verify that the meter and probe 

can be used to measure the entire range of expected specific 

conductance in the field.

2.2 Equipment Maintenance

Maintenance of specific conductance equipment includes 

periodic inspections of meters and probes and checks on 

instrument operation and performance.

• To maintain the specific conductance meter in good 

operating condition—

• Protect the meter and probe from excessive heat 

and cold. Keep the equipment free from dust and 

transport it in a designated case for protection during 

transport.

• Keep all cable connectors dry and free from dirt and 

salts.

• Ensure the batteries are adequately charged and corrosion free.

• Keep the probes clean. Probes may build up dirt and 

corrosion that can affect measurements; therefore, 

regular cleaning is required.

2.2.1 Conductivity Probe Cleaning, Storage, and 

Maintenance

Accurate and precise measurement of specific conductance requires a well-maintained and clean conductivity probe. 

A probe that is dirty or wet with solution other than the sample 

may contaminate the measured solution and bias the measurement of specific conductance. Conductivity probes must 

be clean and the electrodes free from scratches to produce 

accurate results. Refer to the manufacturer’s instructions for 

storage and additional maintenance information.

• To clean conductivity probes—

• Clean the probe thoroughly by rinsing with copious 

amounts of deionized water (DIW) before and after

making a measurement. This is sufficient cleaning in 

most cases.

• Epoxy and graphite conductivity probes can be 

gently wiped with a clean laboratory tissue to 

remove any residues.

• Never wipe or scour platinum-coated electrodes.

• Remove oily residues or other chemical residues 

with a detergent solution and then rinse thoroughly 

with DIW. Probes can soak in detergents for many 

hours without damage.

Figure 6.3–1. Diagram 

showing general guidelines 

for selecting an electrical 

conductivity probe with 

the optimum cell constant. 

Modified from chart in the 

YSI Model 3200 Operations 

Manual (YSI Incorporated, 

1999, p. 43). Definitions: cm-1, 

per centimeter; CO2, carbon 

dioxide; μS/cm at 25 °C, 

microsiemens per centimeter 

at 25 degrees Celsius.
3.0 Calibration 5

• When additional cleaning is required, soak the probe 

in 5-percent volume per volume (v/v) hydrochloric 

acid for as long as 2 hours and then rinse thoroughly 

with DIW. Check the manufacturer’s recommendations before using acid.

• Caution: Platinum and platinum-iridium electrodes 

should not be cleaned in nitric acid (HNO3), aqua 

regia, or any other solution that is known to etch 

platinum or gold. 

Consult your instruction manual for specific storage 

instructions. Most conductivity probes, including probes with 

graphite electrodes, can be stored clean and dry; however, 

probes on multiparameter sondes are required to be stored 

in water (typically tap water) to prevent drying out of other 

sensors. Storage in water is acceptable while the probe is 

in use. 

3.0 Calibration

Specific conductance measurements are only as good 

as the calibration itself. Several factors must be considered 

when calibrating the meter. Thermal expansion of the conductivity cell can affect the cell constant; however, the cell 

constants (Kcell) of modern field probes are generally stable 

from 0 to 100 °C. Most conductivity standards are potassium 

chloride (KCl) solutions, and the linear (0.019–0.020) and 

nonlinear (International Organization for Standardization, 

1985) temperature-compensation factors (α) will produce 

reliable calibrations from 5 to 35 °C. Caution should be 

used when calibrating at temperatures greater than 35 °C, 

however, because the commonly used nonlinear (International 

Organization for Standardization, 1985) temperature compensation deviates substantially when applied to KCl solutions. 

Therefore, if a modern conductivity probe that expands 

minimally with temperature is used and the temperature of the 

water to be measured is between 5 and 35 °C, the temperature 

of the calibration solutions (either laboratory or in situ) is not 

expected to significantly affect the measurement of specific 

conductance of samples in the field.

Conductivity standards are susceptible to contamination 

or dilution from residual solutions, including rinse water, and 

each calibration should be done with care. Low-conductivity 

standards (<200 μS/cm) are especially susceptible to contamination. Calibration in the laboratory prior to field 

measurement, for both specific conductance meters and 

multiparameter sondes, is recommended because the temperature is regulated and the standard solutions are less susceptible 

to contamination. 

Specific conductance meters must be checked or calibrated 

before every field trip to ensure that the meter and probe 

are working properly. The accuracy of specific conductance 

measurements should be checked in the laboratory and in the 

field by conducting measurements on standards whose specific 

conductance is near the expected specific conductance of the 

sample. Measurements of specific conductance standards that 

are within ±5 μS/cm of the certified values for measurements 

≤100 μS/cm or ±3 percent of the certified values for measurements >100 μS/cm are considered accurate and do not warrant 

recalibration. Because specific conductance meters typically 

maintain their calibration, frequent recalibration is generally 

unnecessary and may not improve data accuracy. If calibration 

in the field is required, make certain the temperature of the 

standards is stable and between 5 and 35 °C.

Specific conductance meters utilize either a one- or a 

multipoint calibration procedure. Both calibration procedures work well and the instruction manual accompanying 

the specific conductance meter as well as the NFM should be 

followed closely. Record and track the cell constant (one-point 

calibration) or slope (multipoint calibration), as deviations can 

be used to identify inaccurate calibrations or faulty equipment. 

To verify that the specific conductance meter is responding 

properly at low values of specific conductance, check the zero 

response of the dry conductivity cell in air or DIW. The measured specific conductance of DIW should be <3 μS/cm.

Specific conductance meters are typically calibrated 

with KCl solutions of known concentration that are traceable 

to National Institute of Standards and Technology (NIST). 

Specific conductance standards with certificates of analyses 

(NIST traceable) with values between 50 and 50,000 μS/cm 

are available from USGS One Stop.1

 Electrical conductivities of highly accurate KCl standards (0.01, 0.1, and 1.0 mole 

per kilogram [mol/kg]) were determined by Pratt and others 

(2001) and are shown in table 6.3–2. Extreme care should be 

used when calibrating with dilute (<200-μS/cm) solutions, 

as small amounts of contaminants or minor dilution can 

substantially affect the calibration. Triple rinsing with DIW 

and calibration standards is required. In addition to conductivity standards, the USGS Quality Systems Branch (QSB) 

provides a variety of standard reference samples (SRSs), 

prepared from natural waters, for quality-assurance testing and 

measurements of specific conductance.

3.1 One-Point Calibration—Determination of

the Cell Constant

Many specific conductance meters and multiparameter 

sondes utilize a one-point calibration for measurement of 

specific conductance. Calibration of specific conductance 

meters using a one-point calibration involves determination 

of the cell constant (Kcell) by measuring the conductance (G) 

of a standard solution with a known conductivity (κ) (see 

equation 1, where the value of κ is known). Meters utilizing one-point calibrations typically require calibration with 

1

Equipment and supplies that are tested and quality assured are available 

to USGS field studies from the National Field Supply Service (NFSS) 

and the Hydrologic Instrumentation Facility (HIF), and are sold through 

the USGS One Stop ordering system (accessed September 11, 2017, at 

https://1stop.usgs.gov/, internal USGS access only).
6 Chapter A6.3. Specific Conductance

Table 6.3–2. Electrical conductivity of molality-based primary KCl 

standards.

[μS/cm, microsiemens per centimeter; m, molality in mol/kg of solution; 

mol/kg, mole per kilogram; KCl, potassium chloride; °C, degrees Celsius; 

CO2, carbon dioxide; H2O, water; —, not available]

Electrical conductivity, in μS/cm1

Temperature, 

in oC

Molality (m) of KCl solutions, in mol/kg

0.01 0.1 1.0

0 773.50 7117.4 63489

5 891.64 8184.4 72031

10 1014.7 9292.5 80845

15 1142.3 10438 89901

18 1220.9 11142 —

20 1274.0 11617 99171

25 1409.3 12826 108620

30 1547.8 14060 118240

35 1689.1 15317 127970

40 1832.7 16592 137810

45 1978.1 17882 147720

50 2125.0 19183 157670

1

Data from Pratt and others (2001). Values represent CO2-saturated H2O.

standard solutions having specific conductance values of 500, 

1,413, or 12,900 μS/cm. Select the standard with a specific 

conductance that is closest to the expected specific conductance of the samples. Once the cell constant is determined, 

the conductivity of the environmental water sample is determined by using equation 1 and the specific conductance is 

determined by using equation 2. The cell constant of many 

modern specific conductance probes is nearly constant (±2 

percent) over a wide range of concentration and temperature 

because the physical dimension of the cell does not change 

appreciably. Record and track the cell constant with each calibration, as changes in the cell constant that exceed 2 percent 

may be the result of a contaminated standard or dirty probe. 

After the meter is calibrated, check the accuracy of the calibration by measuring at least one additional specific conductance 

standard that brackets the expected range of environmental 

values to be measured. Measurements of specific conductance 

standards that are within ±5 μS/cm of the certified values for 

measurements ≤100 μS/cm or ±3 percent of the certified values for measurements >100 μS/cm are considered accurate and 

do not warrant recalibration.

3.2 Multipoint Calibration

Some specific conductance meters utilize a multipoint 

calibration method. For a multipoint calibration, the conductance is determined for standards, and the conductivity of the 

sample is determined by interpolation to a standard curve. 

If the meter allows the user to select conductivity standards, 

choose standards that bracket the expected specific conductance of the samples. Record and track the slope and intercept 

with each calibration, as substantial changes may be the result 

of contaminated standards or a dirty probe. Bias can occur 

as a result of contamination as well as dilution from rinse 

water. DIW and calibration standards with values less than 

200 μS/cm are susceptible to bias from dilution or contamination and are difficult to measure accurately. Therefore, it is 

recommended to calibrate specific conductance with standards with values that are greater than 200 μS/cm. After the 

meter is calibrated, check the accuracy of the calibration by 

measuring the specific conductance of at least one additional 

standard near the expected range of environmental values to 

be measured. Measurements of specific conductance standards 

that are within ±5 μS/cm of the certified values for measurements ≤100 μS/cm or ±3 percent of the certified values for 

measurements >100 μS/cm are considered accurate and do not 

warrant recalibration.

Deionized water and calibration standards with specific 

conductance less than 200 μS/cm are susceptible to 

bias from dilution or contamination and are difficult to 

measure accurately. It is recommended to calibrate specific 

conductance with standards with values that are greater 

than 200 μS/cm. After the meter is calibrated, check the 

accuracy of the calibration by measuring the specific 

conductance of standards near the expected range of 

environmental values to be measured.

3.3 Meter Calibration Procedure

The calibration procedure described in this section 

applies to most field specific conductance meters equipped 

with a probe containing a dip-style conductivity cell and builtin temperature compensation. Refer to the meter’s manual 

for specific instructions. Calibration in the laboratory prior to 

field measurement is recommended because the temperature 

is regulated and the standard solutions are less susceptible to 

contamination. If calibration in the field is required, the same 

procedure should be followed. Make certain the temperature 

of the standards is stable and between 5 and 35 °C.

Calibration in the laboratory prior to field measurement 

is recommended because the temperature is regulated 

and the standard solutions are less susceptible to 

contamination.

• Meter calibration steps—

1. If possible, select a probe with a conductivity cell 

that will most accurately measure the expected 

specific conductance (fig. 6.3–1). However, many 

modern specific conductance meters and multipa-
3.0 Calibration 7

rameter sondes have one all-purpose conductivity 

cell designed to measure a wide range of specific 

conductance values in natural waters.

2. Inspect the meter and conductivity cell for 

damage. Check the batteries and change or 

charge the batteries if needed. Make sure the 

cables are clean and properly connected.

3. Select calibration standards. If possible, use 

specific conductance standards that bracket 

(multipoint calibration) or are near (one-point 

calibration) the expected specific conductance 

of the samples. Some meters utilize an automatic calibration procedure and can only be 

calibrated with standards having certain specific 

conductance (for example, 100, 500, 1,413, or 

12,900 μS/cm). For a multipoint calibration, 

begin the calibration with the standard that has 

the lowest specific conductance and continue 

the calibration by using standards in ascending 

order. Use fresh standards and verify that the 

date on the standards has not expired. Do not use 

expired standards.

4. Fill the calibration cup or beaker to about one 

third full with DIW. Place the probe in the beaker 

or calibration cup and thoroughly rinse the probe 

(note that some probes on multiparameter sondes 

require an aggressive rinse procedure). Rinse the 

probe with the DIW from the cup or beaker and 

shake off the excess liquid. Dispose of the solution. Repeat this procedure for a total of three 

times. Do not calibrate using DIW; however, the 

measured specific conductance of DIW should be 

<3 μS/cm.

5. Fill the calibration cup or beaker to about onethird full with the specific conductance standard. 

For a one-point calibration, this will be a 

standard chosen that is near the expected specific 

conductance of the sample. For a multipoint 

calibration, this will be the specific conductance 

standard with the lowest value of the standards 

that have been chosen for the calibration. Place 

the probe in the calibration cup or beaker and 

swirl the probe to thoroughly rinse. Ensure that 

the conductivity cell (all electrodes on the probe) 

is completely submerged. Rinse the probe with 

a small amount of the standard and shake off 

excess liquid. Dispose of the solution. Repeat this 

procedure for a total of three times.

6. Fill the calibration cup or beaker with the specific 

conductance standard, place the probe in the 

solution, gently swirl the solution to ensure all 

air bubbles are removed from the cell, and allow 

the solution and probe to equilibrate. Monitor the 

temperature and conductance, and when both are 

stable, begin the calibration following the meter’s 

calibration procedure. 

7. For one-point calibration, the cell constant can 

now be determined. For multipoint calibration, 

the calibration of the first point can now be determined. For a multipoint calibration, repeat steps 

4 through 6 for each standard, beginning with the 

lowest conductivity standard and continuing the 

calibration in ascending order.

8. Record the following in the instrument log 

book, field sheets, or personal computing field 

forms (PCFFs):

a. The concentrations and lot numbers of the 

conductivity standards and their known and 

measured specific conductance,

b. The temperature of the standard solution,

c. The water-temperature compensation 

utilized (unless the user changes the settings 

or uses a low-pH conductivity method, the 

temperature compensation may only need to 

be recorded once in the log book),

d. The cell constant (one-point calibration) 

or the slope and intercept (multipoint 

calibration), and

e. The meter type, meter serial number, and 

probe serial number.

9. Verify that the new calibration parameters are 

consistent with previous calibrations and are 

within the limits established by the manufacturer.

10. Discard the standard solution into a waste 

container, thoroughly rinse the cell with DIW, 

and dry.

11. Check the accuracy of the calibration by 

measuring at least one additional standard. For 

a one-point calibration, the additional standard 

should be one that brackets the expected specific 

conductance value of the sample. For a multipoint calibration, the additional standard should 

have a value near the expected range of environmental values to be measured. The specific 

conductance of USGS SRSs also can be measured to check accuracy. The specific conductance of check standards should be within ±5 μS/

cm for measurements ≤100 μS/cm or ±3 percent 

for measurements >100 μS/cm. Recalibrate the 

specific conductance meter if the measured specific conductance of the check standards does not 

meet the calibration criteria. 
8 Chapter A6.3. Specific Conductance

4.0 Measurement of Specific 

Conductance

In situ measurements generally are preferred for determining the specific conductance of surface water, and downhole or flow-through cell measurements are preferred for 

groundwater. Specific conductance is typically determined on 

an unfiltered sample.

• The following precautions should be taken when 

measuring specific conductance—

• It is best to measure the specific conductance of the 

sample in situ because the specific conductance of 

water can change over time as a result of chemical and physical processes such as precipitation, 

adsorption, degassing, and oxidation.

• If a measurement cannot be made in situ and the 

water is highly susceptible to substantial gain or 

loss of dissolved gases, make the measurement 

from a composited or discrete subsample within a 

triple-rinsed, gas-impermeable container fitted with 

a stopper. Measure the specific conductance as soon 

as possible and try to maintain the sample at the 

temperature at which it was collected. Gas-bubble 

formation on the probe surface or gases flowing over 

the surface will result in an inaccurate reading.

• When using multiparameter sondes, avoid 

contamination from the pH electrode-filling solution and calibration buffers. The pH buffers and 

filling solutions have high ionic strengths and are a 

potential source of contamination. When calibrating 

multiparameter sondes, calibrate specific conductance before pH.

• When measuring the specific conductance of flowing 

water, make sure that the conductivity cell has no 

cavitation or air bubbles. If the water velocity is too 

high to measure the specific conductance accurately, 

relocate the probe to an area with lower velocity or 

measure the specific conductance of a representative 

subsample as soon as possible. 

• The stability criterion for recording a specific 

conductance measurement in the field is ±5 μS/cm 

for measurements ≤100 μS/cm or ±3 percent for 

measurements >100 μS/cm. A measurement outside 

the criterion is likely the result of air or cavitation 

within the conductivity cell, a faulty meter, or poor 

mixing of the measured water, causing its composition to change rapidly. 

• Standard temperature-compensation factors 

(either linear [0.019–0.020 per °C] or nonlinear 

[International Organization for Standardization, 

1985]) should be utilized for samples with pH 

between 4 and 11 and temperature between 

5 and 35 °C. 

4.1 Measurement of Specific Conductance in 

Surface Water

Specific conductance of surface water should be 

measured in situ if practical; otherwise, measure specific conductance in discrete samples collected from a sample splitter 

or compositing device. 

4.1.1 In Situ Measurement of Specific 

Conductance in Surface Water

Measurements of specific conductance in flowing surface 

water should represent the cross-sectional mean or median 

specific conductance at the time of observation. Any deviation 

from this convention must be documented in the database and 

with the published data. This requirement is especially important for poorly mixed streams at points downstream from a 

convergence or source of drainage.

• Before making a measurement of specific conductance—

• If you are unfamiliar with the sample site, measure 

a depth and cross-sectional specific conductance 

profile to determine the degree of system variability. 

A dip-style conductivity probe works best for this 

purpose.

• Refer to NFM A6.0 for information on which sampling method to use.

• To measure specific conductance in surface water—

1. Check the accuracy of the specific conductance 

measurement at the field site by measuring the 

specific conductance of a check standard. Select 

a check standard with a specific conductance 

similar to that of the sample. The specific conductance of check standards should be within 

±5 μS/cm for measurements ≤100 μS/cm or ±3 

percent for measurements >100 μS/cm. Recalibrate if necessary.

2. Determine the variation of specific conductance 

along a cross-sectional profile using an appropriate measurement method (see NFM A6.0; use 

equal-width increment [EWI] or equal-discharge 

increment [EDI] method if required):

a. If the stream is flowing and wadable, wade 

to the location(s) where specific conductance 

is to be measured.
4.0 Measurement of Specific Conductance 9

b. If the stream is too deep or swift to wade, 

lower a conductivity probe from a bridge, 

cableway, or boat.

c. For still-water conditions in streams, measure specific conductance at multiple depths 

at several points in the cross section.

d. For large still-water bodies such as lakes, 

reservoirs, and estuaries, measure specific 

conductance at multiple depths and locations 

depending on the study objectives.

3. Immerse the specific conductance probe in the 

water to the appropriate depth and hold (not less 

than 60 seconds) until the probe equilibrates 

to water conditions. Determine equilibration 

by observing stability of the reading. Always 

keep probes above the streambed so as not to 

immerse the sensor into bed sediments, which 

can bias readings.

4. Record the measurements of specific conductance and temperature without removing the 

probes from the water.

a. Consecutive measurements should meet 

the stability criterion (±5 μS/cm for measurements ≤100 μS/cm or ±3 percent for 

measurements >100 μS/cm).

b. Record the stabilized value on field forms.

c. If the readings do not meet the stability 

criterion after extending the measurement 

period, record this difficulty in the field 

notes along with the fluctuation range and 

the median value of the last five or more 

readings. Consider troubleshooting the 

measurement (see section 5.0) or using a different specific conductance meter.

5. For measurements made using EWI or EDI 

methods, proceed to the next station in the cross 

section and repeat steps 3 and 4. Record on 

field forms the stable value for each subsection 

measured.

6. When the measurements are completed, remove 

the probe from the water, rinse it with DIW, and 

store the meter and probe in a protective case.

7. Record specific conductance and temperature on 

the field sheet following the procedures described 

in NFM A6.0 for still-water, EDI, or EWI measurement methods. Refer to section 6.0 below for 

reporting of specific conductance values.

4.1.2 Measurement of Specific Conductance on 

a Subsample from Surface Water

Representative samples for analysis of water quality are 

collected and split or composited according to approved USGS 

methods (NFM A4). Measure the specific conductance of 

these composited subsamples as soon as possible after collection. If the sample cannot be analyzed immediately, fill a clean 

and triple-rinsed bottle completely to the top, cap it tightly, 

and attempt to maintain the sample at stream temperature until 

measurement. Reported values of specific conductance typically are determined on an unfiltered sample.

• High concentrations of suspended sediment can be a 

source of measurement error—record such conditions in the field notes.

• If there appears to be a lot of suspended sediment in 

the water sample, measure the specific conductance 

of both unfiltered and filtered subsamples and record 

both values on the field form. High concentrations of 

suspended sediments may interfere with the measurement of specific conductance, and the inference 

may vary from site to site depending on the type, 

size, and concentration of suspended sediments. 

• If the values of specific conductance for the filtered 

and unfiltered samples differ by more than ±5 μS/

cm for measurements ≤100 μS/cm or ±3 percent 

for measurements >100 μS/cm, report the filtered 

value and identify it as having been measured on a 

“filtered sample.”

• Steps to measure specific conductance on a 

subsample of surface water—

1. Check the accuracy of the specific conductance 

measurement at the field site by measuring 

the specific conductance of a check standard. 

Select a check standard with a specific conductance similar to that of the sample. The specific 

conductance of check standards should be 

within ±5 μS/cm for measurements ≤100 μS/cm 

or ±3 percent for measurements >100 μS/cm. 

Recalibrate if necessary.

2. Select the sampling method (see NFM A6.0) and 

collect a representative sample.

3. Withdraw a homogenized subsample from a 

sample splitter or compositing device. Rinse a 

clean sample bottle three times with the sample. 

For filtered samples, rinse with sample filtrate.

4. Prepare the specific conductance probe for 

sample measurement:
10 Chapter A6.3. Specific Conductance

a. First, rinse the specific conductance probe 

and the container three times with DIW.

b. Next, rinse the specific conductance probe 

and the container three times with sample 

water.

5. Allow the probe to equilibrate to sample temperature, then discard the sample water. Pour fresh 

sample water into a container holding the probe, 

as described by the manufacturer to avoid fringe 

field interferences. 

6. Allow the probe to thermally equilibrate to the 

water temperature by monitoring the temperature.

7. Measure specific conductance.

a. Remove any air trapped in the sensor by 

gently swirling the probe up and down under 

the water surface.

b. Read the meter display.

c. Gently swirl the sensor up and down under 

the water surface, and read the display again.

d. Repeat the procedure until consecutive 

readings are the same. Consecutive measurements should meet the stability criterion 

(±5 μS/cm for measurements ≤100 μS/cm or 

±3 percent for measurements >100 μS/cm).

8. Record specific conductance and temperature 

on the field sheet. Refer to section 6.0 below for 

reporting of specific conductance values.

9. Collect replicates for quality control.

a. Repeat steps 4b through 8 with at least two 

fresh subsamples, rinsing the probes only 

once with sample water.

b. Subsample values should be within 

±5 μS/cm for specific conductance 

≤100 μS/cm or ±3 percent for specific conductance >100 μS/cm.

c. If criteria cannot be met, filter the samples, 

report the value of specific conductance 

of three or more samples, and record this 

difficulty in the field notes. 

10. Rinse the probe and the container with DIW and 

store the meter and probe as directed by the manufacturer in a protective case.

4.2 Measurement of Specific Conductance in 

Groundwater

Measurements of specific conductance in groundwater 

must be representative of aquifer conditions. Temperature and 

redox changes resulting from transporting a sample from the 

aquifer to land surface can affect measurements of specific 

conductance.

• To minimize environmental effects on measurements 

of specific conductance in wells—

• Measure specific conductance as close to the source 

as possible, using either a downhole or flow-through 

chamber sampling system (refer to NFM A6.0 for 

details).

• Bailing or other methods for collecting discrete samples isolated from the source are not recommended 

as standard practice for the measurement of specific 

conductance, although such methods are sometimes 

called for owing to site characteristics or other study 

requirements.

• The well should be purged or in the process of purging before sample specific conductance is measured 

and recorded. During purging, confirm that readings 

of temperature and specific conductance have stabilized before proceeding with specific conductance 

measurements.

4.2.1 Measurement of Specific Conductance in 

a Well

• For measurements of specific conductance downhole 

or in a flow-through chamber with water pumped 

from a well—

1. Check the accuracy of the specific conductance 

measurement at the field site by measuring 

the specific conductance of a check standard. 

Select a check standard with a specific conductance similar to that of the sample. The specific 

conductance of check standards should be 

within ±5 μS/cm for measurements ≤100 μS/cm 

or ±3 percent for measurements >100 μS/cm. 

Recalibrate if necessary.

2. Install the specific conductance probe.

a. For measurement in a downhole system—

i. Lower the probe to the sampling point.

ii. Remove air trapped in the conductivity cell by gently moving the probe up 

and down under the water; read the 

meter display.
4.0 Measurement of Specific Conductance 11

iii. Repeat this procedure until the 

specific conductance measurement 

is stable. Consecutive measurements should meet the stability 

criterion (±5 μS/cm for measurements 

≤100 μS/cm or ±3 percent for measurements >100 μS/cm).

b. For measurement with a pumped flow-cell 

system—

i. Install the flow-cell system as close 

to the well as possible and shield the 

system from direct sunlight.

ii. Depending on the flow-cell design, 

position the specific conductance probe 

upstream from the pH electrode.

iii. Direct water flow to the flow cell after 

an initial discharge of waste to clear 

sediment and other contaminants from 

the sample line.

iv. Release air trapped in the chamber and 

ensure air is not trapped in the conductivity cell.

v. Consecutive measurements 

should meet the stability criterion 

(±5 μS/cm for measurements 

≤100 μS/cm or ±3 percent for measurements >100 μS/cm). If the readings are 

not consistent, air may be trapped in 

the cell.

3. While purging the well, maintain a constant flow 

rate.

4. Allow the probe to thermally equilibrate with 

groundwater temperature for 5 minutes or more 

at the flow rate to be used for collecting all other 

samples.

5. Measure specific conductance and temperature at 

regular intervals throughout purging; record the 

values of specific conductance and the associated 

temperatures on field forms.

6. Check the variability of the measured specific 

conductance toward the end of purging.

a. The specific conductance stability criterion 

is met when five measurements made at 

regularly spaced intervals of 3 to 5 minutes 

or more are within ±5 μS/cm for specific 

conductance ≤100 μS/cm or ±3 percent for 

specific conductance >100 μS/cm.

b. When readings fluctuate rapidly, record the 

median of three or more readings within 

approximately 60 seconds as the value for a 

specific time interval.

c. If the stability criterion is not met, extend 

the purge period in accordance with study 

objectives and continue to record measurements at regularly spaced time intervals. 

Record this difficulty on the field forms.

7. Report the specific conductance and temperature.

a. Record the final five values on the field 

sheet.

b. Report the median value of the final five 

specific conductance values. Refer to section 

6.0 below for reporting of specific conductance values.

c. If the stability criterion is not met, report 

the range of values observed for the time 

interval on the field sheet, along with the 

median of the final five or more values. 

Consider troubleshooting the measurement 

(see section 5.0) or using a different specific 

conductance meter.

4.2.2 Measurement of Specific Conductance on 

a Subsample from a Well

Specific conductance measurements reported from bailed 

or other discrete samples need to be identified in the database, 

indicating the sampling method used. Refer to NFM A6.0 for 

use of bailers and the subsample method.

• To measure specific conductance on a bailed or 

discrete groundwater sample—

1. Check the accuracy of the specific conductance 

measurement at the field site by measuring 

the specific conductance of a check standard. 

Select a check standard with a specific conductance similar to that of the sample. The specific 

conductance of check standards should be 

within ±5 μS/cm for measurements ≤100 μS/cm 

or ±3 percent for measurements >100 μS/cm. 

Recalibrate if necessary.

2. Draw off subsamples for measurement.

3. If samples need to be stored for a short time, 

or if measurements will be made on several 

subsamples, collect sample aliquots in separate 

field-rinsed bottles—fill completely with no 

headspace, cap tightly, and maintain at ambient 

groundwater temperature. Measure specific conductance as soon as possible.
12 Chapter A6.3. Specific Conductance

TECHNICAL NOTES:

• If the measurement is made on a sample in an open 

 container and readings do not stabilize within several 

 minutes, the cause may be CO2 degassing. Use a closed 

 system to make the measurement.

• Filter a sample to measure specific conductance if clay 

 or other suspended particles interfere with the stability 

 of the readings.

4.3 Measurement of Specific Conductance of a 

Water Sample with Low or High pH 

Specific conductance (and electrical conductivity) data 

are reported at 25 °C. Most modern specific conductance 

meters have the capability to compensate for temperature automatically. Equation 2 is used most commonly to determine the 

specific conductance at 25 °C and commercially available field 

specific conductance meters typically use either a constant α 

(typically 0.019–0.020 per °C) or a nonlinear α (International 

Organization for Standardization, 1985). Whereas these commonly used temperature-compensation factors work well for 

waters having a pH between 4 and 11, they can be the source 

of errors as large as 50 percent for low-pH samples.

4.3.1 Measurement of Specific Conductance of 

a Water Sample with Low pH (<4)

The specific conductance measurement error for low-pH 

(<4) waters can be large if the commonly used temperaturecompensation factors are used. To determine whether an alternative temperature-compensation method should be used for 

samples with pH <4, the in situ specific conductance should 

be compared to the specific conductance of a sample equilibrated to 25 °C. If the measurements are comparable (within 

±5 μS/cm for specific conductance ≤100 μS/cm or ±3 percent 

for specific conductance >100 μS/cm), then the temperature 

algorithm used is likely sufficient. If a temperature-compensation factor is required for a water sample with pH <4, the 

method described by McCleskey (2013) is recommended. 

4.3.2 Measurement of Specific Conductance of 

a Water Sample with High pH (>11)

No temperature-compensation method is available for 

waters with high pH (>11); therefore, the specific conductance should be checked by making a measurement at ambient 

temperature and at 25 °C for waters with pH >11. At high pH, 

hydroxide becomes a major ion in the solution and its mobility 

is different than that of most other ions. However, the hydroxide-equivalent conductivity is much lower than the hydrogenequivalent conductivity and, unlike in low-pH waters, the standard temperature-compensation approaches may be adequate. 

Furthermore, relatively few natural waters have a pH >11, so 

this situation is fairly rare.

5.0 Troubleshooting

Contact the instrument manufacturer if the actions suggested in table 6.3–3 fail to resolve the problem. One of the 

first things to check is the battery voltage. Always have fresh 

batteries in meters and carry spares when taking meters out 

into the field.

Check the voltage of batteries. Always have fresh batteries 

in field meters and carry spares.

6.0 Reporting Specific Conductance in 

Natural Waters

• Follow USGS standard protocols for reporting specific conductance in the National Water Information 

System (NWIS) database—

• Report the value on the field forms to three significant figures for specific conductance ≥100 μS/cm or 

two significant figures for specific conductance <100 

μS/cm. 

• Enter field-determined specific conductance measurements on the USGS National Water Quality 

Laboratory (NWQL) Analytical Services Request 

(ASR) form using the correct parameter code.

• Report the temperature-compensation factor in the 

comment field if a nonstandard temperature compensation is utilized (for example, if the low-pH 

temperature-compensation method is used).

6.1 Uncertainty in Measurements of Specific 

Conductance

The primary sources of uncertainty for specific conductance measurements are quality of calibration standards, 

temperature compensation, quality of the specific conductance 

meter and probe, and contamination of the sample during 

measurement. The uncertainty for most routine specific 

conductance measurements is estimated to be <5 μS/cm for 

specific conductance ≤100 μS/cm or <3 percent of the most 

probable value for specific conductance >100 μS/cm. This 

uncertainty was estimated by using results from multiple interlaboratory comparison studies performed by the USGS QSB. 

Comparison studies of specific conductance were conducted 

over 19 years, and included 74 SRSs whose specific conductance ranged from 5 to 1,100 μS/cm; 16 to 93 laboratories 

participated in each SRS study. The QSB provides SRSs for 

specific conductance quality-assurance testing. Additionally, 

all USGS WMA personnel who measure specific conductance 
7.0 Applications of Specific Conductance in Surface Water and Groundwater 13

Table 6.3–3. Troubleshooting guide for measurements of specific conductance.

[>, Greater than; ≤, less than or equal to; HCl, hydrochloric acid; μS/cm, microsiemens per centimeter; °C, degrees Celsius]

Symptom Possible cause and corrective action

Meter will not calibrate to standards 

or will not accurately read 

standards

• Standards may be old or contaminated—use fresh standards.

• Electrodes dirty—first clean with a detergent solution, then if necessary with 5-percent HCl. 

Before using any acid solution to remove resistant residues, check manufacturer’s guidelines.

• Air trapped in conductivity sensor—gently move sensor up and down to expel trapped air.

• Weak or corroded batteries—replace.

• Temperature compensation incorrect—ensure that thermistor is operating properly.

• Multiparameter sonde inadequately rinsed—repeat rinsing.

Erratic readings • Loose or defective connections—tighten or replace.

• Broken cables—repair or replace.

• Air trapped in conductivity probes—gently move sensor up and down to expel trapped air.

• Rapid changes in water temperature of subsample—measure in situ.

• Degassing of groundwater sample—measure the specific conductance downhole, or use a 

sealed flow-cell chamber.

• Broken conductivity probe—replace.

Specific conductance meter requires 

frequent recalibration

• Temperature compensation may not be working—measure specific conductance of a solution. 

Place solution in a water bath and raise solution temperature to about 25 oC. Measure specific 

conductance again, allowing sufficient time for the probe to equilibrate to temperature of solution. If the two values differ by ±5 μS/cm for specific conductance ≤100 μS/cm or ±3 percent 

for specific conductance >100 μS/cm, check the temperature-compensation settings on the 

meter, check the thermistor, and consider replacing the conductivity probe.

Specific conductance reading is 

drifting or variable

• Insufficient equilibration—allow conductivity cell to thermally equilibrate with water samples 

and repeat measurements.

• Probe dirty or malfunctioning—clean or replace conductivity probe.

are required to participate in the National Field Quality 

Assurance project (NFQA), whereby samples of known values 

of specific conductance are distributed annually to test the 

proficiency of the analysts and accuracy of the equipment.

The primary sources of uncertainty for specific 

conductance measurements are quality of calibration 

standards, temperature compensation, quality of the 

specific conductance meter and probe, and contamination 

of the sample during measurement.

7.0 Applications of Specific 

Conductance in Surface Water and 

Groundwater

Measurements of specific conductance have been used to 

estimate the salinity of (Lewis, 1980), ionic strength of (Lind, 

1970), and concentrations of major solutes (McCleskey and 

others, 2012a) and TDS (Hem, 1985) in natural waters. In 

addition, the specific conductance and the relative contribution of a given ion to the overall specific conductance (known 

as the transport number) can be calculated from chemical 

analyses (McCleskey and others, 2012b). The USGS geochemical speciation codes WATEQ4F (Ball and Nordstrom, 

1991) and PHREEQC (Parkhurst and Appelo, 1999) have 

the capability to estimate the specific conductance of natural 

waters by using the concentrations of dissolved species. The 

relative percent difference between measured and calculated 

specific conductance can be used together with charge balance 

as a quality-control check for water analyses (McCleskey and 

others, 2012b). It is also possible to compare the concentration 

of TDS in milligrams per liter (mg/L) to specific conductance 
14 Chapter A6.3. Specific Conductance

in microsiemens per centimeter (μS/cm) where the ratio is 

expected to be between 0.5 and 0.9 (Hem, 1985).

TD mg/L

specific conductance in μS/cm

S in  0.5 to 0.9 (3)

Measurements of specific conductance are commonly used 

to estimate the salinity of water.

Acknowledgments

The information included in the U.S. Geological Survey 

(USGS) National Field Manual (NFM) is based on existing 

manuals, various reference documents, and a broad spectrum 

of expertise provided by USGS colleagues. Authors of previous versions of NFM chapter A6.3 were D.B. Radtke, J.V. 

Davis, and F.D. Wilde, whose expertise and integrity provided 

the groundwork for this and future versions of this chapter. 

The persistence and spirit that all of our USGS colleagues 

brought to the development of a national field manual were 

invaluable.

The following USGS colleagues provided detailed technical content and reviews that improved the quality of this report: 

R. Blaine McCleskey, Gerolamo Casile, Joseph Domagalski, 

Michael Manning, Cherie Miller, Michael Rosen, Stanley 

Skrobialowski, and Teri Snazell. Editorial and production 

assistance from Marilyn Billone, Sandy Cooper, Elizabeth 

Good, Cathy Knutson, Katharine Schindler, and Dale Simmons 

is greatly appreciated. These individuals contributed to the 

accuracy, quality, and usability of the NFM, and demonstrated 

much patience as we traversed the difficult task of developing 

the new format.

Special thanks are extended to Franceska Wilde (USGS), 

who led the effort for the NFM from its inception until her 

retirement in 2014; the USGS NFM Steering Committee 

(Gerolamo Casile, Michael Manning, Cherie Miller, Callie 

Oblinger (retired), Timothy Oden, Lisa Olsen, Michael Rosen, 

and Stanley Skrobialowski); Cherie Miller, who led the effort 

from 2016 to 2018; and Gerolamo Casile, who assumed 

responsibility for the NFM in 2018.

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U.S. Geological Survey—Specific Conductance—Techniques and Methods 9–A6.3

ISSN 2328-7055 (online)

https://doi.org/10.3133/tm9A6.3