ASTM D6764-02
(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.
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 and health practices and determine the applicability of regulatory requirements prior to use.
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Designation: D 6764 – 02
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 D 6764; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 5464 TestMethodforpHMeasurementsofWaterofLow
Conductivity
1.1 This guide describes procedures to collect cross-
sectional means of temperature, dissolved oxygen, specific
3. Terminology
electrical conductance, and pH of water flowing in open
3.1 Definitions:
channels.
3.1.1 For definitions of terms used in this guide, refer to
1.2 This guide provides guidelines for preparation and
Terminology D 1129 and D 4410.
calibrationoftheequipmenttocollectcross-sectionalmeansof
3.2 Definitions of Terms Specific to This Standard:
temperature, dissolved oxygen, specific electrical conductance,
3.2.1 electronic temperature sensor—an electrical device
and pH of water flowing in open channels.
that converts changes in resistance to a readout calibrated in
1.3 This guide describes what equipment should be used to
temperature units. Thermistors and resistance temperature
collect cross-sectional means of temperature, dissolved oxy-
detectors are examples of electronic temperature sensors.
gen,specificelectricalconductance,andpHofwaterflowingin
3.2.2 thermometer—any device used to measure tempera-
open channels.
ture, consisting of a temperature sensor and some type of
1.4 This guide covers the cross-sectional means of tempera-
calibrated scale or readout device.
ture, dissolved oxygen, specific electrical conductance, and pH
of fresh water flowing in open channels.
4. Summary of Guide
1.5 This standard does not purport to address all of the
4.1 This guide establishes criteria and describes procedures
safety concerns, if any, associated with its use. It is the
for the collection of cross-sectional means of temperature,
responsibility of the user of this standard to establish appro-
dissolved oxygen (DO), specific electrical conductance (SC),
priate safety and health practices and determine the applica-
and pH of water flowing in open channels.
bility of regulatory requirements prior to use.
4.2 This guide provides only generic guidelines for equip-
ment use and maintenance. Field personnel must be familiar
2. Referenced Documents
2 with the instructions provided by equipment manufacturers.
2.1 ASTM Standards:
Therearealargevarietyofavailablefieldinstrumentsandfield
D 888 Test Method for Dissolved Oxygen in Water
instruments are being continuously updated or replaced using
D 1125 Test Method for Electrical Conductivity and Resis-
newer technology. Field personnel are encouraged to contact
tivity of Water
equipment manufacturers for answers to technical questions.
D 1129 Terminology Relating to Water
D 1293 Test Method for pH of Water
5. Significance and Use
D 4410 Terminology for Fluvial Sediment
5.1 This guide describes stabilization criteria for recording
D 4411 Guide for Sampling Fluvial Sediment in Motion
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
This guide is under the jurisdiction ofASTM Committee D19 on Water and is
measurements and the procedures to be use in the field to
the direct responsibility of Subcommittee D19.07 on Sediment, Geomorphology,
obtain these data.
and Open Channel Flow.
Current edition approved March 10, 2002. Published May 2002.
5.3 This guide describes quality assurance procedures to be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
followedwhenobtainingcross-sectionalmeansoftemperature,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
dissolved oxygen, specific electrical conductance, and pH of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. water flowing in open channels.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6764–02
TABLE 1 Stabilization Criteria for Recording Field
ally in Table 1, for a set of three or more sequential measure-
Measurements (1)
ments. The natural variability inherent in surface water at the
time of sampling generally falls within these stability criteria
NOTE—[6,plusorminusvalueshown;°C,degreesCelsius;#lessthan
or equal to values shown; µS/cm microsiemens at 25°C, >, greater than
and reflects the accuracy that should be attainable with a
value shown; unit, standard pH unit; mg/L milligram per liter].
calibrated instrument.
Standard Direct Stabilization Criteria for Measurements
6.1.3 Allow at least 60 s (or follow the manufacturer’s
Field Measurement (Variability Should Be Within the Value Shown)
guidelines) for sensors to equilibrate with sample water. Take
Temperature:
instrumentreadingsuntilthestabilizationcriteriainTable1are
Electronic Temperature Sensor 60.2°C
met. Record the median of the final three or more readings as
Liquid-in-glass thermometer 60.5°C
Specific Electrical Conductance:
the value to be reported for that measurement point.
when# 100 mS/cm 65%
6.2 Locating Points of Measurement in Cross-Section:
when > 100 mS/cm 65%
pH: 6.2.1 The location and the number of field measurements
Meter displays to 0.01 60.1 unit
depend on study objectives. Generally, a single set of field-
Dissolved oxygen:
measurement data is used to represent an entire stream cross
Amperometric method 60.3 mg/L
section at a sampling site and can be useful when calculating
chemical loads.
6.2.2 To obtain data representative of the section, the
5.4 Field measurement must accurately represent the water
variability of discharge and field measurements across the
flowing in the open channel being measured. Methods need to
stream must be known. This information is used to determine
be used that will result in an accurate representation of the
if the equal-discharge-increment (EDI) or equal-width-
meanoftheparameterofinterest.Proceduresmustbeusedthat
increment (EWI) method of locating field-measurement points
will take into consideration the variation in the parameter
should be used. See Terminology D 4410 for definitions of
across the sections and with depth.
these terms.
5.5 Temperature and DO must be measured directly in the
6.2.2.1 Check the cross-sectional profile data of the stream
water in the open channel. SC and pH are often measured in
site to determine the variability of discharge per unit width of
situ, but also may be measured in a subsample of a composite
the stream and of field-measurement values across the section.
sample collected using discharge-weighted methods.
Make individual measurements at a number of equally-
6. Procedure
spaced verticals along the cross section and at multiple depths
within each vertical; or, consult previous records for the site.
General Comments
Make in situ (see 6.2.3.3) field measurements for the
6.1 Field measurements should represent, as closely as
profile.
possible, the natural condition of the surface-water system at
Field-measurement profiles of stream variability are
the time of sampling. Field teams must determine if the
needed for low- and high-flow conditions and should be
instruments and method to be used will produce data of the
verified at least every 2 years or as study objectives dictate.
type and quality required to fulfill study needs. Experience and
6.2.2.2 Select the EDI or EWI method to locate points of
knowledge of field conditions often are indispensable for
measurement (see reference (2) for information on EDI and
determining the most accurate field-measurement value.
EWI methods) to select and execute the appropriate method.
6.1.1 To ensure the quality of the data collected (1) :
6.1.1.1 Calibration is required at the field site for most If stream depth and velocities along the cross section are
instruments. Make field measurements only with calibrated relatively uniform, use the EWI method.
instruments.
If stream depth and velocities along the cross section are
6.1.1.2 Each field instrument must have a permanent log-
highly variable, use the EDI method.
book for recording calibrations and repairs. Review the log-
In a small and well-mixed stream, a single point at the
book before leaving for the field.
centroidofflowmaybeusedtorepresentthecrosssection.The
6.1.1.3 Test each instrument (meters and sensors) before
centroid of flow is defined as the point in the increment at
leaving for the field. Practice your measurement technique if
which discharge in that increment is equal on both sides of the
the instrument or measurement is new to you.
point.
6.1.1.4 Have backup instruments readily available and in
6.2.3 Use the following procedure when making a field
good working condition.
measurement using the EDI method.
6.1.2 Before making field measurements, sensors must be
6.2.3.1 Divide the cross section into equal increments of
allowed to equilibrate to the temperature of the water being
discharge (see reference (1) for details on how to properly do
monitored. Sensors have equilibrated adequately when instru-
this.)
ment readings have “stabilized,” that is, when the variability
6.2.3.2 Select either the in situ or subsample method and
among measurements does not exceed an established criterion.
follow the instructions in 6.3 or 6.4.
The criteria for stabilized field readings are defined operation-
6.2.3.3 In Situ Method—Go to the centroid of the first
equal-discharge increment. Using submersible sensors, mea-
sure at mid-depth (or multiple depths) in the vertical. Repeat at
The boldface numbers in parentheses refer to the list of references at the end of
this guide. eachvertical.Thevaluerecordedateachverticalrepresentsthe
D6764–02
median of values observed within approximately 60 s after 6.2.4.5 In Situ Method—Measure at the midpoint of each
sensor(s) have equilibrated with stream water. equal-width increment. Using submersible sensors, measure at
6.2.3.4 Subsample Method—Collect an isokinetic depth- mid-depth in the vertical.
integrated sample at the centroid of each equal-discharge 6.2.4.6 Subsample Method—Collect an isokinetic depth-
increment, emptying the increment sample into a compositing integrated sample at the midpoint of each equal-width incre-
device. Measure field parameters either in the sample collected ment, emptying each sample into a compositing device. Use of
at each increment or in a subsample taken from the composite the correct sampling equipment is critical to execute this
of all the increment samples. method successfully: standard samplers cannot meet isokinetic
6.2.3.5 The final field-measurement value is the mean of the requirements when stream velocity is less than 1.5 ft/s.
in situ or individual increment-sample value for all the EDI 6.2.4.7 Record a value for each field measurement for each
verticals in the section (the composite subsample yields a vertical. The value recorded represents the stabilized values
single value). Note for pH it is necessary to calculate the mean observed within approximately 60 s after the sensor(s) have
by (1) converting each pH measurement to its antilogarithm equilibrated with the stream or subsample water.
-(pH)
timesminusone(10 ),(2)usingthesetransformedvaluesto 6.2.4.8 Example—Table 3 provides an example of an area-
calculate the mean, and (3) converting the mean value to a weighted median measurement for conductivity measured in
logarithm multiplied by minus one (refer to 6.8.4.5). situ. In the example, the area-weighted median conductivity
6.2.3.6 Enter data on a field form. equals 130 µS/cm. To calculate an area-weighted median,
6.2.3.7 Example—Table 2 is an example of how mean multiply the area of each increment by its corresponding field
conductivity measured in situ is calculated using the equal- measurement, sum the products of all the increments, and
discharge-increment method. divide by total cross-sectional area. Note that if the conductiv-
6.2.3.8 In the example, the correct value for the discharge- ity reported was selected at mid-depth of the vertical of
weightedmeanconductivityis163µS/cm,calculatedfrom815 centroid of flow (Section 10), it would have been reported as
dividedby5(thesumoftherecordedmedianvaluesdividedby 125 µS/cm; if the conductivity reported was near the left edge
the number of median measurements). Note that at the mid- of water, it would have been reported as 150 µS/cm.
point of the center centroid of flow (increment 3) the median 6.2.4.9 The final field-measurement value normally is cal-
conductivity would have been reported as 155 µS/cm; if culated as the mean of the values recorded at all EWI
conductivity had been measured near the left edge of the water increments, resulting in an area-weighted mean (for pH it is
(increment 1), the conductivity would have been reported as necessary to calculate the mean by (1) converting each pH
-(pH)
185 µS/cm. measurement to its antilogarithm times minus one (10 ), (2)
6.2.4 Use the following procedure when making a field using these transformed values to calculate the mean, and (3)
measurement using the EWI method. converting the mean value to a logarithm multiplied by minus
6.2.4.1 Divide the cross section into equal increments of one.)
width (see reference (1) for details on how to properly do this.) 6.3 In Situ Measurement Procedures:
6.2.4.2 Insitufieldmeasurementsaremadeatthemidpoints 6.3.1 In situ measurement (Fig. 1), made by immersing a
of each increment. Area-weighted concentrations can be com- field-measurement sensor directly in the water body, is used to
puted from these measurements (Table 3). determineaprofileofvariabilityacrossastreamsection.Insitu
6.2.4.3 Subsample field measurements are made in discrete measurement can be repeated if stream discharge is highly
samples that usually are withdrawn from a composite sample variable and measurement points need to be located at incre-
collected using an isokinetic sample and isokinetic depth- ments of equal discharge. However, in situ measurements are
integrating method. The volume of the isokinetic sample must point samples, and, thus, are not depth integrated.
be proportional to the amount of discharge in each increment 6.3.2 Measurements made directly (in situ) in the surface-
and measurements in subsamples taken from the compositing water body are preferable in order to avoid changes that result
device result in discharge-weighted values. from removing a water sample from its source. In situ
...
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