U.S. Geological Survey, Water Supply Paper 2175

By S. E. Rantz and others





Conversion factors

Chapter l.—Introduction

Purpose of the manual

Scope of the manual

Streamflow records

General stream-gaging procedures

Selected reference

Chapter 2.—Selection of Gaging-Station Sites


Considerations in specific site selection

Selected references

Chapter 3.—Gaging-Station Controls

Types of control

Attributes of a satisfactory control

Artificial controls

Choice of an artificial control

Choice between weir and flume

Choice between critical-flow flume and supercritical-flow flume


Design of an artificial control

Selected references

Chapter 4.—Measurement of Stage


Datum of gage

Nonrecording stream-gaging stations

Staff gage

Wire-weight gage

Float-tape gage

Electric-tape gage

Chain gage

Recording stream-gaging stations

Methods of sensing stage for automatic recording

Float sensor

Bubble-gage sensor

Water-stage recorders

Digital recorder

Graphic recorder

Stilling wells

Instrument shelters

Reference and auxiliary gages at recording gaging stations

Telemetering systems

Position-motor system

Impulse system

Telemark system

Resistance system

Satellite data-collection system

Operation of a recording stream-gaging station

Factors affecting the accuracy of the stage record

Nonrecording gages

Staff gage

Wire-weight gage

Float-tape gage

Electric-tape gage

Chain gage

Accuracy of float-operated recorders

Accuracy of bubble-gage recorders

Special purpose gages

Model T recorder

SR recorder

Crest-stage gage

Selected references

Chapter 5—Measurement of Discharge by Conventional Current-Meter Method


General description of a conventional current-meter measurement of discharge

Instruments and equipment

Current meters

Vertical-axis current meters

Horizontal-axis current meters

Comparison of performance of vertical-axis and horizontal-axis current meters

Optical current meter

Care o fthe current meter

Rating of current meters

Sounding equipment

Wading rods

Sounding weights and accessories

Sounding reels


Sonic sounder

Width-measuring equipment

Equipment assemblies

Cableway equipment

Bridge equipment

Boat equipment

Ice equipment

Velocity-azimuth-depth assembly

Miscellaneous equipment

Measurement of velocity

Vertical-velocity curve method

Two-point method

Six-tenths depth method

Three-point method

Two-tenths-depth method

Subsurface-velocity method

Surface-velocity method
Integration method

Five-point method

Six-point method

Procedure for conventional current-meter measurement of discharge

Current-meter measurements by wading

Current-meter measurements from cableways

Current-meter measurements from bridges

Current-meter measurements from ice cover

Current-meter measurements from boats

Networks of current meters

Special problems in conventional current-meter measurements

Measurement of deep, swift streams

Case A. Depth can be sounded

Case B. Depth cannot be sounded, but standard cross section is available

Case C. Depth cannot be sounded and no standard cross section is available
Case D. Meter cannot be submerged

Computation of mean gage height of a discharge measurement

Measurement procedures during rapidly changing stage

Case A. Large streams

Case B. Small streams

Correction of discharge for storage during measurement

Summary of factors affecting the accuracy of a discharge measurement

Accuracy of a discharge measurement made under average conditions

Selected references

Chapter 6.—Measurement of Discharge by the Moving-Boat Method


Theory of the moving-boat method


Vane and angle indicator

Current meter

Rate indicator and counter

Battery charger

Sonic sounder


Measurement procedures

Selection and preparation of the measurement site

Preparation of the equipment

Assembly of the equipment

Selection of the instrument settings

Function of the crew members

Boat operator

Angle observe


Computation of the discharge measurement

Computation of unadjusted discharge

Adjustment of total width and area

Adjustment of mean velocity and total discharge

Determination of vertical-velocity adjustment factor

Application of velocity adjustment to computed discharge

Selected references

Chapter 7.—Measurement of Discharge by Tracer Dilution


Theory of tracer-dilution methods

Theory of the constant-rate-injection method

Theory of the sudden-injection method

Factors affecting the accuracy of tracer-dilution methods


Loss of tracer

Criteria for satisfactory mixing

Calibration of measurement reach

Effect of inflow or outflow between injection and sampling sites

Measurement of discharge by fluorescent-dye dilution

Fluorescent dyes


Description of fluorometer

Effect of temperature on fluorometry

Calibration characteristics of the flurometer

Preparation of standard dye solutions for flurometer calibration

Operation of the fluorometer

Dye-injection apparatus

Mariotte vessel

Floating siphon

Pressure tank

Determination of quantities of fluorescent dye for measuring discharge

Quantity of dye needed for measurement by the constant-rate-injection method

Quantity of dye needed for measurement by the sudden-injection method

Procedures for measuring discharge by the dye-dilution method

Field procedures

Analysis and computations

Sample computation-constant-rate-injection method

Simplified procedures for making numerous dye-dilution measurements of discharge

Measurement of discharge by sodium dichromate dilution


Principle of colorimetric analysis

Method of analysis by colorimeter

Measurement of discharge by salt dilution


Preparation and injection of the concentrated salt solution

Measurement of relative conductance at the sampling site

Computation ofdischarge

Measurement of discharge by dilution of radioactive tracers



Selected references

Chapter 8.—Measurement of Discharge by Miscellaneous Methods



Volumetric measurement

Portable weir plate

Portable Parshall flume

Measurement, of unstable flow-roll waves or slug flow

Characteristics of unstable flow

Determination of discharge

Examples of discharge determination

Proposed instrumentation

Selected references

Chapter 9.-Indirect Determination of Peak Discharge


Collection of field data

Slope-area method

Contracted-opening method

Flow over dams and weirs

Flow through culverts

General classification of flow

Estimating discharge from superelevation in bends

Selected references




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