ASTM D6764-02(2019)
(Guide)Standard Guide for Collection of Water Temperature, Dissolved-Oxygen Concentrations, Specific Electrical Conductance, and pH Data from Open Channels
Standard Guide for Collection of Water Temperature, Dissolved-Oxygen Concentrations, Specific Electrical Conductance, and pH Data from Open Channels
SIGNIFICANCE AND USE
5.1 This guide describes stabilization criteria for recording field measurements of temperature, DO, SC, and pH.
5.2 This guide describes the procedures used to calibrate and check meters to be used in the field to records these measurements and the procedures to be use in the field to obtain these data.
5.3 This guide describes quality assurance procedures to be followed when obtaining cross-sectional means of temperature, DO, SC, and pH of water flowing in open channels.
5.4 Field measurement must accurately represent the water flowing in the open channel being measured. Methods need to be used that will result in an accurate representation of the mean of the parameter of interest. Procedures must be used that will take into consideration the variation in the parameter across the sections and with depth.
5.5 Temperature and DO must be measured directly in the water in the open channel. SC and pH are often measured in situ, but also may be measured in a subsample of a composite sample collected using discharge-weighted methods.
SCOPE
1.1 This guide describes procedures to collect cross-sectional means of temperature, dissolved oxygen (DO), specific electrical conductance (SC), and pH of water flowing in open channels.
1.2 This guide provides guidelines for preparation and calibration of the equipment to collect cross-sectional means of temperature, DO, SC, and pH of water flowing in open channels.
1.3 This guide describes what equipment should be used to collect cross-sectional means of temperature, DO, SC, and pH of water flowing in open channels.
1.4 This guide covers the cross-sectional means of temperature, DO, SC, and pH of fresh water flowing in open channels.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D6764 −02 (Reapproved 2019)
Standard Guide for
Collection of Water Temperature, Dissolved-Oxygen
Concentrations, Specific Electrical Conductance, and pH
Data from Open Channels
This standard is issued under the fixed designation D6764; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1125 Test Methods for Electrical Conductivity and Resis-
tivity of Water
1.1 This guide describes procedures to collect cross-
D1129 Terminology Relating to Water
sectional means of temperature, dissolved oxygen (DO), spe-
D1293 Test Methods for pH of Water
cific electrical conductance (SC), and pH of water flowing in
D4410 Terminology for Fluvial Sediment
open channels.
D4411 Guide for Sampling Fluvial Sediment in Motion
1.2 This guide provides guidelines for preparation and
D5464 Test Method for pH Measurement of Water of Low
calibrationoftheequipmenttocollectcross-sectionalmeansof
Conductivity
temperature, DO, SC, and pH of water flowing in open
3. Terminology
channels.
3.1 Definitions:
1.3 This guide describes what equipment should be used to
3.1.1 For definitions of terms used in this standard, refer to
collect cross-sectional means of temperature, DO, SC, and pH
Terminologies D1129 and D4410.
of water flowing in open channels.
3.2 Definitions of Terms Specific to This Standard:
1.4 This guide covers the cross-sectional means of
3.2.1 electronic temperature sensor, n—an electrical device
temperature, DO, SC, and pH of fresh water flowing in open
that converts changes in resistance to a readout calibrated in
channels.
temperature units. Thermistors and resistance temperature
1.5 This standard does not purport to address all of the
detectors are examples of electronic temperature sensors.
safety concerns, if any, associated with its use. It is the
3.2.2 thermometer, n—any device used to measure
responsibility of the user of this standard to establish appro-
temperature, consisting of a temperature sensor and some type
priate safety, health, and environmental practices and deter-
of calibrated scale or readout device.
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor-
4. Summary of Guide
dance with internationally recognized principles on standard-
4.1 This guide establishes criteria and describes procedures
ization established in the Decision on Principles for the
for the collection of cross-sectional means of temperature, DO,
Development of International Standards, Guides and Recom-
SC, and pH of water flowing in open channels.
mendations issued by the World Trade Organization Technical
4.2 This guide provides only generic guidelines for equip-
Barriers to Trade (TBT) Committee.
ment use and maintenance. Field personnel must be familiar
2. Referenced Documents with the instructions provided by equipment manufacturers.
2 Therearealargevarietyofavailablefieldinstrumentsandfield
2.1 ASTM Standards:
instruments are being continuously updated or replaced using
D888 Test Methods for Dissolved Oxygen in Water
newer technology. Field personnel are encouraged to contact
equipment manufacturers for answers to technical questions.
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
5. Significance and Use
the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology,
and Open-Channel Flow.
5.1 This guide describes stabilization criteria for recording
Current edition approved Nov. 1, 2019. Published December 2019. Originally
field measurements of temperature, DO, SC, and pH.
approved in 2002. Last previous edition approved in 2013 as D6764 – 02 (2013).
DOI: 10.1520/D6764-02R19.
5.2 This guide describes the procedures used to calibrate
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and check meters to be used in the field to records these
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
measurements and the procedures to be use in the field to
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. obtain these data.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6764−02 (2019)
5.3 This guide describes quality assurance procedures to be 6.1.1.4 Have backup instruments readily available and in
followedwhenobtainingcross-sectionalmeansoftemperature, good working condition.
DO, SC, and pH of water flowing in open channels.
6.1.2 Before making field measurements, sensors must be
allowed to equilibrate to the temperature of the water being
5.4 Field measurement must accurately represent the water
monitored. Sensors have equilibrated adequately when instru-
flowing in the open channel being measured. Methods need to
ment readings have “stabilized,” that is, when the variability
be used that will result in an accurate representation of the
among measurements does not exceed an established criterion.
meanoftheparameterofinterest.Proceduresmustbeusedthat
The criteria for stabilized field readings are defined operation-
will take into consideration the variation in the parameter
ally in Table 1, for a set of three or more sequential measure-
across the sections and with depth.
ments. The natural variability inherent in surface water at the
5.5 Temperature and DO must be measured directly in the
time of sampling generally falls within these stability criteria
water in the open channel. SC and pH are often measured in
and reflects the accuracy that should be attainable with a
situ, but also may be measured in a subsample of a composite
calibrated instrument.
sample collected using discharge-weighted methods.
6.1.3 Allow at least 60 s (or follow the manufacturer’s
guidelines) for sensors to equilibrate with sample water. Take
6. Procedure
instrumentreadingsuntilthestabilizationcriteriainTable1are
met. Record the median of the final three or more readings as
GENERAL COMMENTS
the value to be reported for that measurement point.
6.1 Field measurements should represent, as closely as
possible, the natural condition of the surface-water system at 6.2 Locating Points of Measurement in Cross-Section:
the time of sampling. Field teams must determine if the 6.2.1 The location and the number of field measurements
instruments and method to be used will produce data of the depend on study objectives. Generally, a single set of field-
type and quality required to fulfill study needs. Experience and measurement data is used to represent an entire stream cross
knowledge of field conditions often are indispensable for section at a sampling site and can be useful when calculating
determining the most accurate field-measurement value. chemical loads.
6.1.1 To ensure the quality of the data collected (1):
6.2.2 To obtain data representative of the section, the
6.1.1.1 Calibration is required at the field site for most variability of discharge and field measurements across the
instruments. Make field measurements only with calibrated
stream must be known. This information is used to determine
instruments. if the equal-discharge-increment (EDI) or equal-width-
6.1.1.2 Each field instrument must have a permanent log-
increment (EWI) method of locating field-measurement points
book for recording calibrations and repairs. Review the log- should be used. See Terminology D4410 for definitions of
book before leaving for the field.
these terms.
6.1.1.3 Test each instrument (meters and sensors) before
6.2.2.1 Check the cross-sectional profile data of the stream
leaving for the field. Practice your measurement technique if
site to determine the variability of discharge per unit width of
the instrument or measurement is new to you.
the stream and of field-measurement values across the section.
Make individual measurements at a number of equally-
spaced verticals along the cross section and at multiple depths
within each vertical; or, consult previous records for the site.
The boldface numbers in parentheses refer to a list of references at the end of
Make in situ (see 6.2.3.3) field measurements for the
this standard.
profile.
Field-measurement profiles of stream variability are
TABLE 1 Stabilization Criteria for Recording Field
needed for low- and high-flow conditions and should be
Measurements (1)
verified at least every 2 years or as study objectives dictate.
NOTE 1—[±, plus or minus value shown; °C, degrees Celsius; ≤ less
6.2.2.2 Select the EDI or EWI method to locate points of
than or equal to values shown; µS/cm microsiemens at 25°C, >, greater
measurement (see Ref (2) for information on EDI and EWI
than value shown; unit, standard pH unit; mg/L milligram per litre].
methods) to select and execute the appropriate method.
Stabilization Criteria for Mea-
Standard Direct surements
If stream depth and velocities along the cross section are
Field Measurement (Variability Should Be Within
relatively uniform, use the EWI method.
the Value Shown)
If stream depth and velocities along the cross section are
Temperature:
highly variable, use the EDI method.
Electronic temperature sensor ±0.2°C
Liquid-in-glass thermometer ±0.5°C
In a small and well-mixed stream, a single point at the
centroidofflowmaybeusedtorepresentthecrosssection.The
Specific Electrical Conductance:
centroid of flow is defined as the point in the increment at
when#100 mS/cm ±5 %
when >100 mS/cm ±5 %
which discharge in that increment is equal on both sides of the
point.
pH:
6.2.3 Use the following procedure when making a field
Meter displays to 0.01 ±0.1 unit
measurement using the EDI method.
Dissolved Oxygen:
6.2.3.1 Divide the cross section into equal increments of
Amperometric method ±0.3 mg/L
discharge (see Ref (1) for details on how to properly do this.)
D6764−02 (2019)
6.2.3.2 Select either the in situ or subsample method and collected using an isokinetic sample and isokinetic depth-
follow the instructions in 6.3 or 6.4. integrating method. The volume of the isokinetic sample must
6.2.3.3 In Situ Method—Go to the centroid of the first be proportional to the amount of discharge in each increment
equal-discharge increment. Using submersible sensors, mea- and measurements in subsamples taken from the compositing
sure at mid-depth (or multiple depths) in the vertical. Repeat at device result in discharge-weighted values.
eachvertical.Thevaluerecordedateachverticalrepresentsthe
6.2.4.4 Select either the in situ or subsample method and
median of values observed within approximately 60 s after
follow the instructions in 6.3 or 6.4.
sensor(s) have equilibrated with stream water.
6.2.4.5 In Situ Method—Measure at the midpoint of each
6.2.3.4 Subsample Method—Collect an isokinetic depth-
equal-width increment. Using submersible sensors, measure at
integrated sample at the centroid of each equal-discharge
mid-depth in the vertical.
increment, emptying the increment sample into a compositing
6.2.4.6 Subsample Method—Collect an isokinetic depth-
device. Measure field parameters either in the sample collected
integrated sample at the midpoint of each equal-width
at each increment or in a subsample taken from the composite
increment, emptying each sample into a compositing device.
of all the increment samples.
Useofthecorrectsamplingequipmentiscriticaltoexecutethis
6.2.3.5 The final field-measurement value is the mean of the
method successfully: standard samplers cannot meet isokinetic
in situ or individual increment-sample value for all the EDI
requirements when stream velocity is less than 1.5 ft/s.
verticals in the section (the composite subsample yields a
6.2.4.7 Record a value for each field measurement for each
single value). Note for pH it is necessary to calculate the mean
vertical. The value recorded represents the stabilized values
by (1) converting each pH measurement to its antilogarithm
observed within approximately 60 s after the sensor(s) have
–(pH)
times minus one (10 ), (2) using these transformed values
equilibrated with the stream or subsample water.
to calculate the mean, and (3) converting the mean value to a
6.2.4.8 Example—Table 3 provides an example of an area-
logarithm multiplied by minus one (refer to 6.8.4.5).
weighted median measurement for conductivity measured in
6.2.3.6 Enter data on a field form.
situ. In the example, the area-weighted median conductivity
6.2.3.7 Example—Table 2 is an example of how mean
equals 130 µS/cm. To calculate an area-weighted median,
conductivity measured in situ is calculated using the EDI
multiply the area of each increment by its corresponding field
method.
measurement, sum the products of all the increments, and
6.2.3.8 In the example, the correct value for the discharge-
divide by total cross-sectional area. Note that if the conductiv-
weightedmeanconductivityis163µS/cm,calculatedfrom815
ity reported was selected at mid-depth of the vertical of
dividedby5(thesumoftherecordedmedianvaluesdividedby
centroid of flow (Section 10), it would have been reported as
the number of median measurements). Note that at the mid-
125 µS/cm; if the conductivity reported was near the left edge
point of the center centroid of flow (increment 3) the median
of water, it would have been reported as 150 µS/cm.
conductivity would have been reported as 155 µS/cm; if
6.2.4.9 The final field-measurement value normally is cal-
conductivity had been measured near the left edge of the water
culated as the mean of the values recorded at all EWI
(Increment 1), the conductivity would have been reported as
increments, resulting in an area-weighted mean (for pH it is
185 µS/cm.
necessary to calculate the mean by (1) converting each pH
6.2.4 Use the following procedure when making a field
–(pH)
measurementtoitsantilogarithmtimesminusone(10 ),(2)
measurement using the EWI method.
using these transformed values to calculate the mean, and (3)
6.2.4.1 Divide the cross section into equal increments of
converting the mean value to a logarithm multiplied by minus
width (see Ref (1) for details on how to properly do this.)
one.)
6.2.4.2 Insitufieldmeasurementsaremadeatthemidpoints
6.3 In Situ Measurement Procedures:
of each increment. Area-weighted concentrations can be com-
puted from these measurements (Table 3). 6.3.1 In situ measurement (Fig. 1), made by immersing a
6.2.4.3 Subsample field measurements are made in discrete field-measurement sensor directly in the water body, is used to
samples th
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