ASTM D6764-02(2007)
(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
SCOPE
1.1 This guide describes procedures to collect cross-sectional means of temperature, dissolved oxygen, specific electrical conductance, 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, dissolved oxygen, specific electrical conductance, 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, dissolved oxygen, specific electrical conductance, and pH of water flowing in open channels.
1.4 This guide covers the cross-sectional means of temperature, dissolved oxygen, specific electrical conductance, and pH of fresh water flowing in open channels.
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 and health practices and determine the applicability of regulatory requirements prior to use.
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Designation:D6764 −02(Reapproved 2007)
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 D4411 Guide for Sampling Fluvial Sediment in Motion
D5464 Test Method for pH Measurement of Water of Low
1.1 This guide describes procedures to collect cross-
Conductivity
sectional means of temperature, dissolved oxygen, specific
electrical conductance, and pH of water flowing in open
3. Terminology
channels.
3.1 Definitions:
1.2 This guide provides guidelines for preparation and
3.1.1 For definitions of terms used in this guide, refer to
calibrationoftheequipmenttocollectcross-sectionalmeansof
Terminology D1129 and D4410.
temperature, dissolved oxygen, specific electrical conductance,
3.2 Definitions of Terms Specific to This Standard:
and pH of water flowing in open channels.
3.2.1 electronic temperature sensor—an electrical device
1.3 This guide describes what equipment should be used to
that converts changes in resistance to a readout calibrated in
collect cross-sectional means of temperature, dissolved
temperature units. Thermistors and resistance temperature
oxygen, specific electrical conductance, and pH of water
detectors are examples of electronic temperature sensors.
flowing in open channels.
3.2.2 thermometer—any device used to measure
1.4 This guide covers the cross-sectional means of
temperature, consisting of a temperature sensor and some type
temperature, dissolved oxygen, specific electrical conductance,
of calibrated scale or readout device.
and pH of fresh water flowing in open channels.
1.5 This standard does not purport to address all of the
4. Summary of Guide
safety concerns, if any, associated with its use. It is the
4.1 This guide establishes criteria and describes procedures
responsibility of the user of this standard to establish appro-
for the collection of cross-sectional means of temperature,
priate safety and health practices and determine the applica-
dissolved oxygen (DO), specific electrical conductance (SC),
bility of regulatory requirements prior to use.
and pH of water flowing in open channels.
2. Referenced Documents
4.2 This guide provides only generic guidelines for equip-
ment use and maintenance. Field personnel must be familiar
2.1 ASTM Standards:
with the instructions provided by equipment manufacturers.
D888 Test Methods for Dissolved Oxygen in Water
Therearealargevarietyofavailablefieldinstrumentsandfield
D1125 Test Methods for Electrical Conductivity and Resis-
instruments are being continuously updated or replaced using
tivity of Water
newer technology. Field personnel are encouraged to contact
D1129 Terminology Relating to Water
equipment manufacturers for answers to technical questions.
D1293 Test Methods for pH of Water
D4410 Terminology for Fluvial Sediment
5. Significance and Use
5.1 This guide describes stabilization criteria for recording
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
field measurements of Temperature, DO, SC, and pH.
the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology,
and Open-Channel Flow.
5.2 This guide describes the procedures used to calibrate
Current edition approved June 15, 2007. Published July 2007. Originally
and check meters to be used in the field to records these
approved in 2002. Last previous edition approved in 2002 as D6764 – 02. DOI:
measurements and the procedures to be use in the field to
10.1520/D6764-02R07.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or obtain these data.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.3 This guide describes quality assurance procedures to be
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. followedwhenobtainingcross-sectionalmeansoftemperature,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6764−02 (2007)
dissolved oxygen, specific electrical conductance, and pH of 6.1.2 Before making field measurements, sensors must be
water flowing in open channels. allowed to equilibrate to the temperature of the water being
monitored. Sensors have equilibrated adequately when instru-
5.4 Field measurement must accurately represent the water
ment readings have “stabilized,” that is, when the variability
flowing in the open channel being measured. Methods need to
among measurements does not exceed an established criterion.
be used that will result in an accurate representation of the
The criteria for stabilized field readings are defined operation-
meanoftheparameterofinterest.Proceduresmustbeusedthat
ally in Table 1, for a set of three or more sequential measure-
will take into consideration the variation in the parameter
ments. The natural variability inherent in surface water at the
across the sections and with depth.
time of sampling generally falls within these stability criteria
5.5 Temperature and DO must be measured directly in the
and reflects the accuracy that should be attainable with a
water in the open channel. SC and pH are often measured in
calibrated instrument.
situ, but also may be measured in a subsample of a composite
6.1.3 Allow at least 60 s (or follow the manufacturer’s
sample collected using discharge-weighted methods.
guidelines) for sensors to equilibrate with sample water. Take
instrumentreadingsuntilthestabilizationcriteriainTable1are
6. Procedure
met. Record the median of the final three or more readings as
the value to be reported for that measurement point.
General Comments
6.2 Locating Points of Measurement in Cross-Section:
6.1 Field measurements should represent, as closely as
possible, the natural condition of the surface-water system at
6.2.1 The location and the number of field measurements
the time of sampling. Field teams must determine if the
depend on study objectives. Generally, a single set of field-
instruments and method to be used will produce data of the
measurement data is used to represent an entire stream cross
type and quality required to fulfill study needs. Experience and
section at a sampling site and can be useful when calculating
knowledge of field conditions often are indispensable for
chemical loads.
determining the most accurate field-measurement value.
6.2.2 To obtain data representative of the section, the
6.1.1 To ensure the quality of the data collected (1) :
variability of discharge and field measurements across the
6.1.1.1 Calibration is required at the field site for most
stream must be known. This information is used to determine
instruments. Make field measurements only with calibrated
if the equal-discharge-increment (EDI) or equal-width-
instruments.
increment (EWI) method of locating field-measurement points
6.1.1.2 Each field instrument must have a permanent log-
should be used. See Terminology D4410 for definitions of
book for recording calibrations and repairs. Review the log-
these terms.
book before leaving for the field.
6.2.2.1 Check the cross-sectional profile data of the stream
6.1.1.3 Test each instrument (meters and sensors) before
site to determine the variability of discharge per unit width of
leaving for the field. Practice your measurement technique if
the stream and of field-measurement values across the section.
the instrument or measurement is new to you.
Make individual measurements at a number of equally-
6.1.1.4 Have backup instruments readily available and in
spaced verticals along the cross section and at multiple depths
good working condition.
within each vertical; or, consult previous records for the site.
Make in situ (see 6.2.3.3) field measurements for the
profile.
Field-measurement profiles of stream variability are
needed for low- and high-flow conditions and should be
The boldface numbers in parentheses refer to the list of references at the end of
this guide.
verified at least every 2 years or as study objectives dictate.
6.2.2.2 Select the EDI or EWI method to locate points of
TABLE 1 Stabilization Criteria for Recording Field
measurement (see reference (2) for information on EDI and
Measurements (1)
EWI methods) to select and execute the appropriate method.
NOTE 1—[±, plus or minus value shown; °C, degrees Celsius; ≤ less
If stream depth and velocities along the cross section are
than or equal to values shown; µS/cm microsiemens at 25°C, >, greater
relatively uniform, use the EWI method.
than value shown; unit, standard pH unit; mg/L milligram per liter].
If stream depth and velocities along the cross section are
Stabilization Criteria for
highly variable, use the EDI method.
Standard Direct Measurements
In a small and well-mixed stream, a single point at the
Field Measurement (Variability Should Be
Within the Value Shown)
centroidofflowmaybeusedtorepresentthecrosssection.The
Temperature:
centroid of flow is defined as the point in the increment at
Electronic Temperature Sensor ±0.2°C
which discharge in that increment is equal on both sides of the
Liquid-in-glass thermometer ±0.5°C
point.
Specific Electrical Conductance:
when# 100 mS/cm ±5 %
6.2.3 Use the following procedure when making a field
when > 100 mS/cm ±5 %
measurement using the EDI method.
pH:
Meter displays to 0.01 ±0.1 unit
6.2.3.1 Divide the cross section into equal increments of
Dissolved oxygen:
discharge (see reference (1) for details on how to properly do
Amperometric method ±0.3 mg/L
this.)
D6764−02 (2007)
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 incre-
at each increment or in a subsample taken from the composite
ment, emptying each sample into a compositing device. Use of
of all the increment samples.
the correct sampling equipment is critical to execute this
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)
timesminusone(10 ),(2)usingthesetransformedvaluesto
equilibrated with the stream or subsample water.
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 equal-
multiply the area of each increment by its corresponding field
discharge-increment 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)
measurement to its antilogarithm times minus one (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 reference (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 that usually are withdrawn from a composite sample determineaprofileofvariabilityacrossastreamsection.Insitu
TABLE 2 Example of Field Notes for a Discharge-Weighted Conductivity Measurement
2 3
NOTE 1—[ft/sec, feet per second; ft, feet; ft , square feet; ft /s, cub
...
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