ASTM D5674-22

Standard Guide for Operation of a Gaging Station

SIGNIFICANCE AND USE
5.1 This guide is useful when a systematic record of water surface elevation or discharge is required at a specific location. Some gaging stations may be operated for only a few months; however, many have been operated for a century.  
5.2 Gaging station records are used for many purposes:  
5.2.1 Resource appraisal of long-term records to determine the maximum, minimum, and variability of flows of a particular stream. These data can be used for the planning and design of a variety of surface water-related projects such as water supply, flood control, hydroelectric developments, irrigation, recreation, and waste assimilation.  
5.2.2 Management, where flow data are required for the operation of a surface-water structure or other management decision.
SCOPE
1.1 The guide covers procedures used commonly for the systematic collection of streamflow information. Continuous streamflow information is necessary for understanding the amount and variability of water for many uses, including water supply, waste dilution, irrigation, hydropower, and reservoir design.  
1.2 The procedures described in this guide are used widely by those responsible for the collection of streamflow data, for example, the U.S. Geological Survey, Bureau of Reclamation, U.S. Army Corps of Engineers, U.S. Department of Agriculture, Water Survey Canada, and many state and provincial agencies. The procedures are generally from internal documents of the preceding agencies, which have become the defacto standards used in North America.  
1.3 It is the responsibility of the user of the guide to determine the acceptability of a specific device or procedure to meet operational requirements. Compatibility between sensors, recorders, retrieval equipment, and operational systems is necessary, and data requirements and environmental operating conditions must be considered in equipment selection.  
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
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

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 17.120.20 - Flow in open channels
• Technical Committee: D19 - Water
• Drafting Committee: D19.07 - Sediments, Geomorphology, and Open-Channel Flow

Relations

• Refers: ASTM D5541-24 - Standard Practice for Developing a Stage-Discharge Relation for Open Channel Flow
• Effective Date: 01-Apr-2024
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D5243-92(2019) - Standard Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
• Effective Date: 01-Nov-2019
• Refers: ASTM D5389-93(2019) - Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
• Effective Date: 01-Nov-2019
• Refers: ASTM D5129-95(2014) - Standard Test Method for Open Channel Flow Measurement of Water Indirectly by Using Width Contractions
• Effective Date: 01-Jan-2014
• Refers: ASTM D5243-92(2013) - Standard Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
• Effective Date: 01-Jan-2013
• Refers: ASTM D5389-93(2013) - Standard Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
• Effective Date: 01-Jan-2013
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D5541-94(2008) - Standard Practice for Developing a Stage-Discharge Relation for Open Channel Flow
• Effective Date: 01-Oct-2008
• Refers: ASTM D3858-95(2008) - Standard Test Method for Open-Channel Flow Measurement of Water by Velocity-Area Method
• Effective Date: 01-Oct-2008
• Refers: ASTM D5130-95(2008) - Standard Test Method for Open-Channel Flow Measurement of Water Indirectly by Slope-Area Method
• Effective Date: 01-Oct-2008
• Refers: ASTM D5129-95(2008) - Standard Test Method for Open Channel Flow Measurement of Water Indirectly by Using Width Contractions
• Effective Date: 01-Oct-2008
• Refers: ASTM D5243-92(2007) - Standard Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
• Effective Date: 15-Jun-2007
• Refers: ASTM D5390-93(2007) - Standard Test Method for Open-Channel Flow Measurement of Water with Palmer-Bowlus Flumes
• Effective Date: 15-Jun-2007
• Refers: ASTM D5388-93(2007) - Standard Test Method for Indirect Measurements of Discharge by Step-Backwater Method
• Effective Date: 15-Jun-2007

Overview

ASTM D5674-22 – Standard Guide for Operation of a Gaging Station provides essential procedures and considerations for establishing, operating, and maintaining gaging stations that monitor water surface elevation or stream discharge. Developed by ASTM International, this standard supports the selection and implementation of equipment and methods for reliable streamflow monitoring. Gaging stations play a crucial role for governmental agencies, engineers, and water resource managers by enabling the collection of accurate data for water management, resource appraisal, and infrastructure operation.

Continuous records from gaging stations are vital for understanding streamflow variability, planning water supply, flood control, and the development of surface water-related projects. This guide is widely referenced by organizations such as the U.S. Geological Survey (USGS), Bureau of Reclamation, and various state, provincial, and federal agencies across North America.

Key Topics

• Site Selection: Describes ideal site characteristics for gaging stations, including channel stability, absence of hydraulic disturbances, straight river reach, suitable areas for discharge measurements, accessibility, and the presence of natural or artificial controls.

• Types of Gaging Stations: Covers non-recording (manual staff gages) and various recording stations (stilling well, bubbler-type, and acoustic velocity meter (AVM) gages), with guidance on installation, operation, and maintenance.

• Instrumentation: Outlines essential equipment such as water-level sensors, recorders, and data transmission systems, highlighting the need for sensor and recorder compatibility.

• Datum and Reference Marks: Explains establishing a permanent datum (e.g., national geodetic vertical datum) and reference marks for consistent and reliable data.

• Operation and Maintenance: Details periodic inspections, calibration, adjustments, discharge measurements, and record-keeping practices for high-quality data integrity.

• Computation and Calibration: Discusses converting stage measurements to discharge values using rating curves, correcting data for equipment drift or environmental influence, and ensuring computational quality.

• Precision and Bias: Provides guidelines for data accuracy assessments and the importance of record validation and quality assurance.

Applications

Gaging station operations, as guided by ASTM D5674-22, are essential to:

• Water Resource Appraisal: Long-term flow records enable analyses for peak, minimum, and average flow statistics used in water resource planning and environmental assessments.
• Infrastructure Design and Management: Essential data for the planning, design, and operational management of dams, reservoirs, flood control structures, hydroelectric facilities, irrigation systems, and wastewater assimilation.
• Environmental Monitoring: Supports assessment of aquatic habitat, floodplain management, stream restoration, and water quality management.
• Regulatory Compliance: Ensures that water management practices meet the requirements of local and federal agencies, supporting safe and sustainable use.
• Hydrologic Modeling: High-quality streamflow data is critical for developing and validating hydrologic and hydraulic models used in forecasting and scenario planning.

Related Standards

ASTM D5674-22 references and complements numerous ASTM and ISO standards, ensuring comprehensive guidance for open-channel flow measurement and gaging station operation:

• ASTM Standards:
  • D1129 (Terminology Relating to Water)
  • D1941, D3858, D5129, D5130, D5242, D5243, D5388, D5389, D5390, D5413, D5541 (Test Methods/Practices for Measurement and Stage-Discharge Relations)
• ISO Standards:
  • ISO 1100 (Establishment and Operation of a Gauging Station)
  • ISO 6416 (Measurement of Discharge by Ultrasonic/Acoustic Methods)

These standards collectively provide a robust framework for the accurate collection, processing, and application of streamflow data, supporting the sustainable management of water resources.

Keywords: gaging station operation, water discharge measurement, streamflow monitoring, open-channel flow, stage-discharge relation, ASTM D5674, water level, hydrometric data, water resource management.

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: D5674 − 22
Standard Guide for
Operation of a Gaging Station
This standard is issued under the fixed designation D5674; 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 2. Referenced Documents
1.1 The guide covers procedures used commonly for the 2.1 ASTM Standards:
systematic collection of streamflow information. Continuous D1129 Terminology Relating to Water
streamflow information is necessary for understanding the D1941 Test Method for Open Channel Flow Measurement
amount and variability of water for many uses, including water of Water with the Parshall Flume
supply, waste dilution, irrigation, hydropower, and reservoir D3858 Test Method for Open-Channel Flow Measurement
design. of Water by Velocity-Area Method
D5129 Test Method for Open Channel Flow Measurement
1.2 The procedures described in this guide are used widely
of Water Indirectly by Using Width Contractions
by those responsible for the collection of streamflow data, for
D5130 Test Method for Open-Channel Flow Measurement
example, the U.S. Geological Survey, Bureau of Reclamation,
of Water Indirectly by Slope-Area Method
U.S. Army Corps of Engineers, U.S. Department of
D5242 Test Method for Open-Channel Flow Measurement
Agriculture, Water Survey Canada, and many state and pro-
of Water with Thin-Plate Weirs
vincial agencies. The procedures are generally from internal
D5243 Test Method for Open-Channel Flow Measurement
documents of the preceding agencies, which have become the
of Water Indirectly at Culverts
defacto standards used in North America.
D5388 Test Method for Indirect Measurements of Discharge
1.3 It is the responsibility of the user of the guide to
by Step-Backwater Method
determine the acceptability of a specific device or procedure to
D5389 Test Method for Open-Channel Flow Measurement
meet operational requirements. Compatibility between sensors,
by Acoustic Velocity Meter Systems
recorders, retrieval equipment, and operational systems is
D5390 Test Method for Open-Channel Flow Measurement
necessary, and data requirements and environmental operating
of Water with Palmer-Bowlus Flumes
conditions must be considered in equipment selection.
D5413 Test Methods for Measurement of Water Levels in
Open-Water Bodies
1.4 The values stated in inch-pound units are to be regarded
as standard. The values given in parentheses are mathematical D5541 Practice for Developing a Stage-Discharge Relation
for Open Channel Flow
conversions to SI units that are provided for information only
and are not considered standard.
2.2 ISO Standards:
ISO 1100 Liquid Flow Measurement in Open Channels—
1.5 This standard does not purport to address all of the
Part I: Establishment and Operation of a Gauging Station
safety concerns, if any, associated with its use. It is the
ISO 6416 Measurement of Discharge by Ultrasonic (Acous-
responsibility of the user of this standard to establish appro-
tic) Method
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Terminology
1.6 This international standard was developed in accor-
3.1 Definitions:
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the 3.1.1 For definitions of terms used in this guide, refer to
Terminology D1129.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
3.2 Definitions of Terms Specific to This Standard:
Barriers to Trade (TBT) Committee.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This guide is under the jurisdiction ofASTM Committee D19 on Water and is contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology, Standards volume information, refer to the standard’s Document Summary page on
and Open-Channel Flow. the ASTM website.
Current edition approved May 1, 2022. Published June 2022. Originally Measurement of Liquid Flow in Open Channels, ISO Standards Handbook 16,
approved in 1995. Last previous edition approved in 2014 as D5674 – 95 (2014). 1983.AvailablefromAmericanNationalStandardsInstitute(ANSI),25W.43rdSt.,
DOI: 10.1520/D5674-22. 4th Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5674 − 22
3.2.1 control, n—thephysicalpropertiesofachannel,which 5.2.2 Management, where flow data are required for the
determine the relationship between the stage and discharge of operation of a surface-water structure or other management
a location in the channel. decision.
3.2.2 datum, n—a level plane that represents zero elevation.
6. Site Location
3.2.3 discharge, n—the volume of water flowing through a
6.1 The general location of the station will be dependent on
cross-section in a unit of time, including sediment or other
the purpose for which the station is established. Location
solidsthatmaybedissolvedinormixedwiththewater;usually
constraints for a resource appraisal-type station may be quite
cubic feet per second (f /s) or metres per second (m/s).
broad, for example, between major tributaries. Constraints for
3.2.4 elevation, n—the vertical distance from a datum to a a management-type station may require a location just below a
point; also termed stage or gage height.
dam, contaminant discharge point, or other point at which
discharge information is required specifically.
3.2.5 gage, n—a generic term that includes water level
measuring devices.
6.2 Site Requirements—Certain hydraulic characteristics of
the stream channel are desirable for collecting high-accuracy
3.2.6 gage datum, n—a datum whose surface is at the zero
data of minimal cost. Hydraulically difficult sites can still be
elevation of all of the gages at a gaging station. This datum is
gaged; however, accuracy and cost are affected adversely.
often at a known elevation referenced to the national geodetic
Desirable conditions include the following:
vertical datum (NGVD) of 1929.
6.2.1 The general course of the river should be straight for
3.2.7 gage height, n—theheightofawatersurfaceabovean
approximately 300 ft (100 m) above and below the gage.
established or arbitrary datum at a particular gaging station;
6.2.2 The flow is confined to one channel at all stages.
also termed stage.
6.2.3 The stream bed is stable, not subject to frequent scour
and fill, and is free of aquatic growth.
3.2.8 gaging station, n—a particular site on a stream, canal,
6.2.4 The banks are sufficiently high to contain flow at all
lake, or reservoir at which systematic observations of hydro-
stages.
logic data are obtained.
6.2.5 A natural feature such as ledge rock outcrop or stable
3.2.9 national geodetic vertical datum (NGVD) of 1929,
gravel riffle, known as a “control,” is present in the stream. It
n—prior to 1973 known as mean sea level datum, a spheroidal
is necessary and practical in some cases to install a low-head
datum in the conterminous United States and Canada that
dam or artificial control to provide this feature. Additional
approximates mean sea level but does not necessarily agree
information on man-made structures is given in Test Methods
with sea level at a specific location.
D1941, D5242, and D5390.
3.2.10 stilling well, n—a well connected to the stream with
6.2.6 Apool is present behind the control where water-level
intake pipes in such a manner that it permits the measurement
instrumentsorstillingwellintakescanbeinstalledatalocation
of stage in relatively still water.
below the lowest stream stage. The velocity of water passing
sensorsinadeeppoolalsoeliminatesorminimizesdraw-down
4. Summary of Guide
effects on stage sensors during high flow conditions.
6.2.7 The site is not affected by the hydraulic effects of a
4.1 Agaging station is usually installed where a continuous
bridge, tributary stream entering the gaged channel, down-
record of stage or discharge is required. A unique relationship
stream impoundment, or tidal conditions.
exists between water surface elevation and discharge (flow
6.2.8 A suitable site for making discharge measurements at
rate) in most freely flowing streams. Water-level recording
all stages is available near the gage site.
instruments continuously record the water surface elevation,
6.2.9 Thereisaccessibilityforconstructionandoperationof
usually termed stage or gage height. Discharge measurements
the gage.
are taken of the stream discharge to develop a stage-discharge
curve. The discharge data are computed from recorded stage
6.3 Site Selection—An ideal site is rarely available, and
data by a stage-discharge rating curve. judgement must be exercised when choosing between possible
sites to determine that meeting the best combination of
5. Significance and Use features.
6.3.1 Offıce Reconnaissance—The search for a gaging sta-
5.1 This guide is useful when a systematic record of water
tion begins with defining the limits along the stream at which
surface elevation or discharge is required at a specific location.
the gage must be located on topographic maps of the area. The
Some gaging stations may be operated for only a few months;
topographic information will indicate approximate bank
however, many have been operated for a century.
heights or overflow areas, general channel width, constrictions,
5.2 Gaging station records are used for many purposes:
slope, roads, land use, locations of buildings, and other useful
5.2.1 Resource appraisal of long-term records to determine information so that promising locations can be checked out in
the maximum, minimum, and variability of flows of a particu- the field.
lar stream. These data can be used for the planning and design 6.3.2 Field Reconnaissance—If the range of possible gage
of a variety of surface water-related projects such as water locations is large, flying over the stream at a low altitude in a
supply, flood control, hydroelectric developments, irrigation, small aircraft is an efficient way of checking for promising
recreation, and waste assimilation. sites.Theviewfromtheaironacleardayismuchmorehelpful
D5674 − 22
than peering off of a few highway bridges. Traversing the 7. Types of Gaging Stations
channel in a canoe or small boat is an alternative method. Field
7.1 Non-recording stations can be as simple as a permanent
reconnaissance is best performed during low flow conditions;
staff gage attached to a bridge, pier, or other structure, which is
however,additionalreconnaissanceathighflowconditionsand
readandrecordedmanuallyinanappropriatenotebookonceor
under ice-covered conditions for northern streams adds data
more each day. For details on non-recording gages, see Test
that result in improved site selection.
Methods D5413, ISO 1100, and Refs (1-4).
6.3.3 Logistical Reconnaissance—Once a site has been
7.2 Recording gages are usually nonattended installations
selected that meets hydraulic considerations, and before design
that require a sensor in direct contact with the water that is
or construction begins, the following should occur:
connected mechanically or electrically to a recording device.
6.3.3.1 Property ownership must be ascertained and legal
7.2.1 Stilling well-type gages use a vertical well installed in
permission secured to install and maintain the gage. This may
the stream bank with small-diameter intake pipes connecting
include multiple landowners, especially if a cableway is
the river to the well. In this type of installation, a float on the
required from which to make discharge measurements.
water surface in the well drives a recorder housed in a shelter
6.3.3.2 Necessary permits must be obtained from applicable
over the well by mechanical means (Fig. 1). Stilling well gages
governing agencies for, but not limited to, building and
tend to provide more reliable data because water-level sensing
excavation, stream bank permits, and FAA notification for
as well as recording components of the system are protected
cableways or other local requirements.
from direct installation in the stream. Disadvantages are
6.3.3.3 Where electrical or phone service is required for
locations with unstable stream channels that may move away
operation, the availability of this service should be verified.
from the intakes and higher initial cost. For details on stilling
6.3.3.4 Most gaging stations are intended to record over the
well gages, seeTest Methods D5413, ISO 1100, and Refs (1-3,
range of stream stages. It is therefore important to obtain any
5).
local information available on historical flood levels and to
7.2.2 Bubbler-type gages consist of a gas supply, usually
makeestimatesofstagefora100-yeareventusinglocallyused
nitrogen, which is fed through a controller and tube to an
flood-frequency equations.Across-section survey of the chan-
orifice attached near the bed of a stream. The gas pressure is
nel should be obtained during field reconnaissance to aid in
equal to the liquid head in the stream. A pressure transducer,
estimating high flow stage.
mercury, or balance-beam manometer senses this pressure and
6.4 More detailed information is available in Refs (1-3)
passes this information either mechanically or electronically to
and ISO-1100.
a compatible recorder (Fig. 2). The advantage to this system is
less expensive construction costs, which is especially desirable
for short-term gages or in locations in which stilling well
The boldface numbers in parentheses refer to the list of references at the end of
installations are difficult. Disadvantages are maintaining the
this standard.
FIG. 1 Stilling Well Gage
D5674 − 22
FIG. 2 Bubble Gage
orifice in a stable mounting on the river bed. Keeping the other suitable material. The well must have a sealed bottom to
orifice from being buried in silty streams is also a problem. For preclude the interchange of water from the stream and ground
details on bubble-gages, see Test Methods D5413, ISO 1100, water.
and Refs (1-3, 5, 6). 8.1.4 Stilling wells are usually installed in a stream bank for
7.2.3 AcousticVelocityMeter(AVM)stationsdirectlysense protection and to minimize freezing in northern climates. They
and record the velocity observed between two transducers at
may be attached to bridge piers or wing walls in some
fixed elevations in the channel cross section. The AVM gages applications but must be protected from damage by floating
are used in locations in which stage-discharge relations are
debris and must not interfere with flow patterns in the channel.
unreliable, usually in deep, slow-moving channels or where
8.1.5 Intake pipes are required to connect the stilling well to
tidal or bidirectional flow occurs. Additional information is
the stream when the well is buried in the stream bank. Holes in
given in Test Method D5389.
the well usually suffice when installed on a bridge pier or wing
wall.
8. Gaging Station Structures
8.1.5.1 Intakepipesmustbesizedtoallowthewatersurface
inthewelltobeatthesamelevelasthatinthestream,butthey
8.1 Stilling Well Functional Requirements—A stilling well
limit the effect of wind- or boat-generated waves or other
must provide a water surface at the same elevation as that of
transitory or artificial fluctuations of stream water levels.
thestreamatanypointintime,dampenouttheeffectofsurface
Intakepipesaretypically2to4in.(50to100mm)indiameter.
waves, and provide a sensor, usually a float and recording
Long or small-diameter intakes may cause a lag in response in
system.
the stilling well. The following relation can be used to predict
8.1.1 The stilling well must be sufficiently long to cover the
the intake pipe lag for a given rate of change of stage (1).
entire range of stages that might occur reasonably.
8.1.2 The stilling well can be any shape in plan view;
0.01 L A dh
w
2 2
∆h 5
S D S D
however,mostareeitherroundorsquare.Permanentlong-term
g D A dt
p
gages should have a large enough area to allow personnel to
where:
work inside them for servicing; the most common size is
∆h = lag, ft (m),
approximately 4 by 4 ft (1.2 by 1.2 m). Some semipermanent
g = acceleration of gravity, ft (m)/s/s,
stilling wells may be as small as 1 ft (0.3 m).
L = intake length, ft (m),
8.1.3 Stillingwellsmaybefabricatedfrompouredconcrete,
D = intake diameter, ft (m),
concrete blocks, galvanized steel, concrete culvert pipe, or
D5674 − 22
2 2
regulators, and associated tubing. More information is avail-
A = area of stilling well, ft (m ),
w
2 2
able in Refs (1, 6) and ISO 1100.
A = area of intake pipe, ft (m ), and
p
dh
⁄dt = rate of change of stage, ft (m)/s.
8.2.1 Instrument shelter characteristics are similar to those
described in 8.1.7.
8.1.5.2 Two or more intakes are usually installed, one
8.2.2 The orifice from which the compressed gas exits into
vertically above the other, in case an intake is damaged or
the stream must be mounted at least 6 in. (150 mm) below the
silted shut.
lowest expected water levels. In locations at which ice cover is
8.1.5.3 Theinvertelevationofthelowestintakeshouldbeat
present, placing the orifice lower in the water column will
least 6 in. (150 mm) below the lowest expected stream level.
minimize the damage caused by ice breakup or icing over of
The intake should be at least 1 ft (300 mm) above the floor of
the orifice.
the stilling wall to allow for the storage of silt that may enter
8.2.3 The orifice must be mounted in a stable structure that
the structure.
will not move in the channel. Suitable mountings include
8.1.5.4 Drawdown in the stilling well can occur where
poured blocks of concrete, attachments to bridge structures,
stream velocity past the intake is high. Drawdown can be
and pipes or pilings driven into the streambed.
reduced by installing a static tube to the streamward end of the
intake pipe. A typical static tube is a piece of perforated pipe 8.2.3.1 Orifice mountings must have a reference point that
with the capped end attached to the intake pipe with a 90°
can be checked periodically by differential leveling to discern
elbow so that it points downstream. whether movement has occurred.
8.1.6 Stilling wells located in cold climates require special
8.2.4 Orifice positioning in moving sand-channel streams
procedures to prevent the freeze-up of water in the well or
requires special techniques for obtaining satisfactory water-
intake pipes, or both.
level data. A number of techniques have been devised to
8.1.6.1 Stillingwellsincoldclimatesareusuallyinstalledin
overcome these problems, such as using water well drive
stream banks where much of the well is ground covered. Wells
points and multiple orifice installations (1, 5, 6).
should be constructed of nonconductive materials or insulated
8.2.5 A constant supply of gas is required. This is typically
with an insulating material on the well’s exterior. Intake pipes
supplied by commercially available compressed gas cylinders.
should be installed lower to prevent freezing.
8.2.6 A regulator mechanism is required to control and
8.1.6.2 Stilling wells with good ground cover can be kept
reduce the pressure between the gas source and orifice and
ice-free by installing insulated subfloors at ground level.
regulate the bubble discharge rate.
Subfloors must be above normal winter water levels to be
8.2.7 Suitable tubing is required to connect the gas source,
effective. Typical subfloors will be attached rigidly to the
regulators, and orifice. Neoprene tubing with an inside diam-
stilling well and have holes slightly larger than instrument
eter of ⁄8 in. (3 mm) is typically used. The tubing must be
floats to allow the floats to pass through at high water events.
protectedfromphysicald
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5674 − 95 (Reapproved 2014) D5674 − 22
Standard Guide for
Operation of a Gaging Station
This standard is issued under the fixed designation D5674; 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
1.1 The guide covers procedures used commonly for the systematic collection of streamflow information. Continuous streamflow
information is necessary for understanding the amount and variability of water for many uses, including water supply, waste
dilution, irrigation, hydropower, and reservoir design.
1.2 The procedures described in this guide are used widely by those responsible for the collection of streamflow data, for example,
the U.S. Geological Survey, Bureau of Reclamation, U.S. Army Corps of Engineers, U.S. Department of Agriculture, Water Survey
Canada, and many state and provincial agencies. The procedures are generally from internal documents of the preceding agencies,
which have become the defacto standards used in North America.
1.3 It is the responsibility of the user of the guide to determine the acceptability of a specific device or procedure to meet
operational requirements. Compatibility between sensors, recorders, retrieval equipment, and operational systems is necessary, and
data requirements and environmental operating conditions must be considered in equipment selection.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
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 safety, health, and healthenvironmental 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.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1941 Test Method for Open Channel Flow Measurement of Water with the Parshall Flume
D3858 Test Method for Open-Channel Flow Measurement of Water by Velocity-Area Method
D5129 Test Method for Open Channel Flow Measurement of Water Indirectly by Using Width Contractions
D5130 Test Method for Open-Channel Flow Measurement of Water Indirectly by Slope-Area Method
This guide is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.07 on Sediments, Geomorphology, and
Open-Channel Flow.
Current edition approved Jan. 1, 2014May 1, 2022. Published March 2014June 2022. Originally approved in 1995. Last previous edition approved in 20082014 as
D5674 – 95 (2014). (2008). DOI: 10.1520/D5674-95R14.10.1520/D5674-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5674 − 22
D5242 Test Method for Open-Channel Flow Measurement of Water with Thin-Plate Weirs
D5243 Test Method for Open-Channel Flow Measurement of Water Indirectly at Culverts
D5388 Test Method for Indirect Measurements of Discharge by Step-Backwater Method
D5389 Test Method for Open-Channel Flow Measurement by Acoustic Velocity Meter Systems
D5390 Test Method for Open-Channel Flow Measurement of Water with Palmer-Bowlus Flumes
D5413 Test Methods for Measurement of Water Levels in Open-Water Bodies
D5541 Practice for Developing a Stage-Discharge Relation for Open Channel Flow
2.2 ISO Standards:
ISO 1100 Liquid Flow Measurement in Open Channels—Part I: Establishment and Operation of a Gauging Station
ISO 6416 Measurement of Discharge by Ultrasonic (Acoustic) Method
3. Terminology
3.1 Definitions—Definitions:
3.1.1 For definitions of terms used in this guide, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 control—control, n—the physical properties of a channel, which determine the relationship between the stage and discharge
of a location in the channel.
3.2.2 datum—datum, n—a level plane that represents zero elevation.
3.2.3 discharge—discharge, n—the volume of water flowing through a cross-section in a unit of time, including sediment or other
solids that may be dissolved in or mixed with the water; usually cubic feet per second (f /s) or metres per second (m/s).
3.2.4 elevation—elevation, n—the vertical distance from a datum to a point; also termed stage or gage height.
3.2.5 gage—gage, n—a generic term that includes water level measuring devices.
3.2.6 gage datum—datum, n—a datum whose surface is at the zero elevation of all of the gages at a gaging station. This datum
is often at a known elevation referenced to the national geodetic vertical datum (NGVD) of 1929.
3.2.7 gage height—height, n—the height of a water surface above an established or arbitrary datum at a particular gaging station;
also termed stage.
3.2.8 gaging station—station, n—a particular site on a stream, canal, lake, or reservoir at which systematic observations of
hydrologic data are obtained.
3.2.9 national geodetic vertical datum (NGVD) of 1929—1929, n—prior to 1973 known as mean sea level datum, a spheroidal
datum in the conterminous United States and Canada that approximates mean sea level but does not necessarily agree with sea level
at a specific location.
3.2.10 stilling well—well, n—a well connected to the stream with intake pipes in such a manner that it permits the measurement
of stage in relatively still water.
4. Summary of Guide
4.1 A gaging station is usually installed where a continuous record of stage or discharge is required. A unique relationship exists
between water surface elevation and discharge (flow rate) in most freely flowing streams. Water-level recording instruments
continuously record the water surface elevation, usually termed stage or gage height. Discharge measurements are taken of the
stream discharge to develop a stage-discharge curve. The discharge data are computed from recorded stage data by a
stage-discharge rating curve.
Measurement of Liquid Flow in Open Channels, ISO Standards Handbook 16, 1983. Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th
Floor, New York, NY 10036.
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5. Significance and Use
5.1 This guide is useful when a systematic record of water surface elevation or discharge is required at a specific location. Some
gaging stations may be operated for only a few months; however, many have been operated for a century.
5.2 Gaging station records are used for many purposes:
5.2.1 Resource appraisal of long-term records to determine the maximum, minimum, and variability of flows of a particular
stream. These data can be used for the planning and design of a variety of surface water-related projects such as water supply, flood
control, hydroelectric developments, irrigation, recreation, and waste assimilation.
5.2.2 Management, where flow data are required for the operation of a surface-water structure or other management decision.
6. Site Location
6.1 The general location of the station will be dependent on the purpose for which the station is established. Location constraints
for a resource appraisal-type station may be quite broad, for example, between major tributaries. Constraints for a management-
type station may require a location just below a dam, contaminant discharge point, or other point at which discharge information
is required specifically.
6.2 Site Requirements—Certain hydraulic characteristics of the stream channel are desirable for collecting high-accuracy data of
minimal cost. Hydraulically difficult sites can still be gaged; however, accuracy and cost are affected adversely. Desirable
conditions include the following:
6.2.1 The general course of the river should be straight for approximately 300 ft (100 m) above and below the gage.
6.2.2 The flow is confined to one channel at all stages.
6.2.3 The stream bed is stable, not subject to frequent scour and fill, and is free of aquatic growth.
6.2.4 The banks are sufficiently high to contain flow at all stages.
6.2.5 A natural feature such as ledge rock outcrop or stable gravel riffle, known as a “control,” is present in the stream. It is
necessary and practical in some cases to install a low-head dam or artificial control to provide this feature. Additional information
on man-made structures is given in Test Methods D1941, D5242, and D5390.
6.2.6 A pool is present behind the control where water-level instruments or stilling well intakes can be installed at a location below
the lowest stream stage. The velocity of water passing sensors in a deep pool also eliminates or minimizes draw-down effects on
stage sensors during high flow conditions.
6.2.7 The site is not affected by the hydraulic effects of a bridge, tributary stream entering the gaged channel, downstream
impoundment, or tidal conditions.
6.2.8 A suitable site for making discharge measurements at all stages is available near the gage site.
6.2.9 There is accessibility for construction and operation of the gage.
6.3 Site Selection—An ideal site is rarely available, and judgement must be exercised when choosing between possible sites to
determine that meeting the best combination of features.
6.3.1 Offıce Reconnaissance—The search for a gaging station begins with defining the limits along the stream at which the gage
must be located on topographic maps of the area. The topographic information will indicate approximate bank heights or overflow
areas, general channel width, constrictions, slope, roads, land use, locations of buildings, and other useful information so that
promising locations can be checked out in the field.
6.3.2 Field Reconnaissance—If the range of possible gage locations is large, flying over the stream at a low altitude in a small
aircraft is an efficient way of checking for promising sites. The view from the air on a clear day is much more helpful than peering
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off of a few highway bridges. Traversing the channel in a canoe or small boat is an alternative method. Field reconnaissance is
best performed during low flow conditions; however, additional reconnaissance at high flow conditions and under ice-covered
conditions for northern streams adds data that result in improved site selection.
6.3.3 Logistical Reconnaissance—Once a site has been selected that meets hydraulic considerations, and before design or
construction begins, the following should occur:
6.3.3.1 Property ownership must be ascertained and legal permission secured to install and maintain the gage. This may include
multiple landowners, especially if a cableway is required from which to make discharge measurements.
6.3.3.2 Necessary permits must be obtained from applicable governing agencies for, but not limited to, building and excavation,
stream bank permits, and FAA notification for cableways or other local requirements.
6.3.3.3 Where electrical or phone service is required for operation, the availability of this service should be verified.
6.3.3.4 Most gaging stations are intended to record over the range of stream stages. It is therefore important to obtain any local
information available on historical flood levels and to make estimates of stage for a 100-year event using locally used
flood-frequency equations. A cross-section survey of the channel should be obtained during field reconnaissance to aid in
estimating high flow stage.
6.4 More detailed information is available in Refs (1-3) and ISO-1100.
7. Types of Gaging Stations
7.1 Non-recording stations can be as simple as a permanent staff gage attached to a bridge, pier, or other structure, which is read
and recorded manually in an appropriate notebook once or more each day. For details on non-recording gages, see Test Methods
D5413, ISO 1100, and Refs (1-4).
7.2 Recording gages are usually nonattended installations that require a sensor in direct contact with the water that is connected
mechanically or electrically to a recording device.
7.2.1 Stilling well-type gages use a vertical well installed in the stream bank with small-diameter intake pipes connecting the river
to the well. In this type of installation, a float on the water surface in the well drives a recorder housed in a shelter over the well
by mechanical means (Fig. 1). Stilling well gages tend to provide more reliable data because water-level sensing as well as
recording components of the system are protected from direct installation in the stream. Disadvantages are locations with unstable
stream channels that may move away from the intakes and higher initial cost. For details on stilling well gages, see Test Methods
D5413, ISO 1100, and Refs (1-3, 5).
7.2.2 Bubbler-type gages consist of a gas supply, usually nitrogen, which is fed through a controller and tube to an orifice attached
near the bed of a stream. The gas pressure is equal to the liquid head in the stream. A pressure transducer, mercury, or balance-beam
manometer senses this pressure and passes this information either mechanically or electronically to a compatible recorder (Fig. 2).
The advantage to this system is less expensive construction costs, which is especially desirable for short-term gages or in locations
in which stilling well installations are difficult. Disadvantages are maintaining the orifice in a stable mounting on the river bed.
Keeping the orifice from being buried in silty streams is also a problem. For details on bubble-gages, see Test Methods D5413,
ISO 1100, and Refs (1-3, 5, 6).
7.2.3 Acoustic Velocity Meter (AVM) stations directly sense and record the velocity observed between two transducers at fixed
elevations in the channel cross section. The AVM gages are used in locations in which stage-discharge relations are unreliable,
usually in deep, slow-moving channels or where tidal or bidirectional flow occurs. Additional information is given in Test Method
D5389.
8. Gaging Station Structures
8.1 Stilling Well Functional Requirements—A stilling well must provide a water surface at the same elevation as that of the stream
at any point in time, dampen out the effect of surface waves, and provide a sensor, usually a float and recording system.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
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FIG. 1 Stilling Well Gage
FIG. 2 Bubble Gage
8.1.1 The stilling well must be sufficiently long to cover the entire range of stages that might occur reasonably.
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8.1.2 The stilling well can be any shape in plan view; however, most are either round or square. Permanent long-term gages should
have a large enough area to allow personnel to work inside them for servicing; the most common size is approximately 4 by 4 ft
(1.2 by 1.2 m). Some semipermanent stilling wells may be as small as 1 ft (0.3 m).
8.1.3 Stilling wells may be fabricated from poured concrete, concrete blocks, galvanized steel, concrete culvert pipe, or other
suitable material. The well must have a sealed bottom to preclude the interchange of water from the stream and ground water.
8.1.4 Stilling wells are usually installed in a stream bank for protection and to minimize freezing in northern climates. They may
be attached to bridge piers or wing walls in some applications but must be protected from damage by floating debris and must not
interfere with flow patterns in the channel.
8.1.5 Intake pipes are required to connect the stilling well to the stream when the well is buried in the stream bank. Holes in the
well usually suffice when installed on a bridge pier or wing wall.
8.1.5.1 Intake pipes must be sized to allow the water surface in the well to be at the same level as that in the stream, but they limit
the effect of wind- or boat-generated waves or other transitory or artificial fluctuations of stream water levels. Intake pipes are
typically 2 to 4 in. (50 to 100 mm) in diameter. Long or small-diameter intakes may cause a lag in response in the stilling well.
The following relation can be used to predict the intake pipe lag for a given rate of change of stage (1).
0.01 L A dh
w
2 2
Δh 5
S D S D
g D A dt
p
where:
Δh = lag, ft (m),
g = acceleration of gravity, ft (m)/s/s,
L = intake length, ft (m),
D = intake diameter, ft (m),
2 2
A = area of stilling well, ft (m ),
w
2 2
A = area of intake pipe, ft (m ), and
p
dh
⁄dt = rate of change of stage, ft (m)/s.
8.1.5.2 Two or more intakes are usually installed, one vertically above the other, in case an intake is damaged or silted shut.
8.1.5.3 The invert elevation of the lowest intake should be at least 6 in. (150 mm) below the lowest expected stream level. The
intake should be at least 1 ft (300 mm) above the floor of the stilling wall to allow for the storage of silt that may enter the structure.
8.1.5.4 Drawdown in the stilling well can occur where stream velocity past the intake is high. Drawdown can be reduced by
installing a static tube to the streamward end of the intake pipe. A typical static tube is a piece of perforated pipe with the capped
end attached to the intake pipe with a 90° elbow so that it points downstream.
8.1.6 Stilling wells located in cold climates require special procedures to prevent the freeze-up of water in the well or intake pipes,
or both.
8.1.6.1 Stilling wells in cold climates are usually installed in stream banks where much of the well is ground covered. Wells should
be constructed of nonconductive materials or insulated with an insulating material on the well’s exterior. Intake pipes should be
installed lower to prevent freezing.
8.1.6.2 Stilling wells with good ground cover can be kept ice-free by installing insulated subfloors at ground level. Subfloors must
be above normal winter water levels to be effective. Typical subfloors will be attached rigidly to the stilling well and have holes
slightly larger than instrument floats to allow the floats to pass through at high water events. These holes can be covered with
light-weight insulating materials such as foam insulating board that will either float on top of instrument floats or float out of place
during high water events.
8.1.6.3 Electric or propane heaters can be used to prevent freezing. Electric heat bulbs hanging in the center of the well under an
instrument shelf can be quite effective for heating the air above the water surface. Submergible heaters can be placed in the well
to heat the water. Heat tape can be installed in intake pipes, if necessary.
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8.1.6.4 Bubbler systems, allowing a gas, usually nitrogen, to be bubbled from an open-ended tube placed on the well floor under
recorder floats, will circulate warmer water from the bottom and prevent surface ice formation.
8.1.7 Instrument shelters can vary from large walk-in shelters installed on large stilling wells to small weatherproof boxes attached
on small-diameter pipe wells. The shelter’s functional requirements depend on the type and quantity of instrumentation, climate,
and environmental and security conditions. Walk-in shelters with a 4 by 4-ft (1.2 by 1.2-m) minimum are desirable for installations
with complex equipment, which require lengthy servicing during inclement weather. Some shelters are equipped with electricity,
phones, telemetry, and other operational support systems.
8.2 Bubbler-type station-functional requirements basically require an instrument shelter to house pressure-sensi
...