UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. C. Mendenhall, Director. Water-Supply Paper 888 STREAM-GAGING PROCEDURE A MANUAL DESCRIBING METHODS AND PRACTICES OF THE GEOLOGICAL SURVEY BY DON M. COKBETT AND OTHERS UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1943 For sale by the Superintendent of Documents, U. S. Government Printing Office Washington, D. C. Price 65 cents (paper cover) CONTENTS Page Foreword, by Nathan C. Grover____--_-______-____________________ xin Introduction. __ ________-__-_-____________--____________::_____.____ 1 Administration, personnel, and acknowledgments._----_-_--___________ 2 Organization for water-resources investigations,__-_-_-____-___-__-__-- 3 Water Resources Branch._______________________________________ 3 Division of Surface Water ___________________________________ 3 Division of Ground Water.,___--_-_____-___-_---_-________ 4 Division of Quality of Water__-------___--________________ 4 Division of Power Resources._______________________________ 4 Division of Water Utilization.-_____________________________ 4 Administration and operation.__________________________________ 4 Personnel ___________________________________________________ 5 Recruiting of personnel___________________________________- 5 Training of personnel-_______________________--__------_--_ 6 General procedure.._______________________________________________ 7 Records of stage___________________-_______---_-__---_--_--____-_ 8 Methods of obtaining gage-height record.____________-_-_---_____ 9 Observed gage heights___________________ ________________ 9 Recorded gage heights.____________________________________ 10 Observers __ _________________________________________________ 10 Availability. ______________________*_______--_-_-_-_---_--__ 10 Trustworthiness,__________________________________________ 10 Duties ________*____-________________________________-_____ 10 Compensation. __ __________________________________________ 13 Measurement of discharge._____________-___-__.__-_____---_-_-_---- 13 Current-meter measurements....-_____-__________--_-_-_-------_ 13 Types of discharge measurements...____._.__ ________________ 14 Wading measurement- _ _____________________-_--_-J-_-_ 14 Cableway measurement________:___._____-_-_-___--__-- 16 Bridge measurement__________________-_-______'--___-- 19 Boat measurement------------------..----.-.---------- 21 Measurement through ice cover. ________________________ 24 General precautions._______________________________________ 28 Suspension of current meter and measurement of depth- _______ 28 Rod suspension______-__________-_--___-----_-----_-- 29 Hand-line suspension.-.,-______________________________ 30 Reel suspension..__-_._-______-_-_---_-_.---_--------- 31 Single-conductor system with hand-line or reel suspensions_ _ _ 31 Electrical hook-up with dry cell eliminated-______________ 33 Measurement of velocity.________-___---______---_--------- 34 Vertical velocity-curve method._____-______-______-_---- 35 Two-point method___-______.-_____-____--____-_---_-- 37 Six-tenths-depth method-__-_--__--_---____------------ 38 Two-tenths-depth method- ___._._-___.___._-___-_-----_ 39 in IV CONTENTS Measurement of discharge Continued. Current-meter measurements Continued. Measurement of velocity Continued. Pa£e Three-point method____________________---------_--- 41 Subsurface method______-_-_-----__------------------- 41 Integration method--.--.------- _____----_----__---_ 42 One-point continuous method____________-__-_------_-_- 42 Measurements of streams that are deep and swift __________ 43 Measurement of depth___________------_--------------- ,- 44 Placement of current meter._______________-__---------- 52 Procedure._____________-----_----------------------_- 54 Tag-line method__________________-______--__-__---_- 56 Stay-line equipment._______________-_-_-__-_---------- 57 Horizontal angles__________________-_-___-------__-__ 58 Recording of data.____________--_------__-__-----_--___-_- 59 Form 9-275_______________.__._______._..___ .__._ 59 Form 9-275a______________________--_--_----_----_-. 61 Form9-275b .____.__._____ --_-_ - 62 Form 9-275c____.._______.._...___..__....__._.-..._.. 62 Form 9-275d______._____. - _ 62 Factors affecting the accuracy of measurements______-_-___-__ 65 Use and care of equipment_________________--_-_-----_ 65 Selection of measuring section..__________________________ 66 Spacing of verticals_______--___-__--__-------_---_---_- 68 Measurement ojf depth.________________________________ 69 Ice in measuring section.___________-_____-___--___--__- 69 Freezing temperatures_______________________________ 70 Turbulent flow and turbulence._________________________ 70 Angle of current______________________-__-_-_--_--_-___ 71 Effects of piers, piling, and eddies____----_------------__ 73 Vertical and horizontal motion of meter__'________________ 75 Insufficient weight on current meter.____________________ 75 Wind________________________________________ 75 Drift and aquatic growth in channel.____________________ 76 Mean gage height for a discharge measurement ____________________ 76 Special methods.______________________________________________ 80 Weirs.______.___i _________________________________ 80 Slope area________________l_______________________________ 81 Floats_____________________________________ 84 Venturi meter___________________________________________ 85 Parshall measuring flume.__________________________________ 86 Submerged orifice_____________________________________ 87 Chemical methods.________________________________________ 88 Salt velocity..____._____________________________ 88 Salt dilution...___________________________________ 89 Contracted openings_____________-______.__________________ 90 Velocity-area method-_-______-_________-___--____--_______ 91 Computation of discharge over dams_______________________ 93 Calibration of water wheels and valves, gates, and sluices_____ 94 Volumetric method________________________________________ 96 Determination of discharge by adjustments for gain or loss in storage_______________________________________________ 97 Laboratory models______________________________________ 97 CONTENTS Measurement of discharge Continued. Determination of flood discharge..___-_----__----.-----------____ 98 Extension of rating curve__-______-___-___---_---_-_----____ 98 Extension on logarithmic paper______-___---___-_--______ 99 Extension by d-Q'_____________________________ 99 Extension by studies of areas and velocity-_______________ 99 Extension of discharge as a function of A-\d. _____________ 100 Slope-area method_________________________________________ 100 Selection of reach____________________________________ 100 Survey________________________________ 101 Oflice procedure_-_________-_-__-_-_____-_--_-----____- 101 Assumptions and computations.-..______________________ 102 Contracted-opening method_______________________________ 102 Selection of the contracted opening._____________________ 103 Survey.-...-----_------_--_________-_-_._-_---_- 103 Oflice procedure_______________________________________ 103 Assumptions and computations________________________ 104 Flow over dam______-______-_-________________-_---_-_____ 104 Selection of dam____________________________________ 104 Survey__-___-__-----__________-_____-------___--__--- 105 Oflice procedure.______________________________________ 106 Assumptions and computations____________-_--_--_____ 106 Other methods_________.._________________- 107 Critical-depth method_-___________-___________-__^i__ 107 Timing of flood drift--_______-__._-_________-__--__ 108 Flood formulas____._._____________________ 108 Flow characteristics in open channels._______________________________ 109 Stage-discharge relation._______________________________________ 109 Permanent controls__________________________--__-___--_-_- 111 Low-water controls_______-______________--_-___------_-___ 112 Sensitiveness of low-water controls.______________________ 115 Submergence of low-water controls_____________________ 115 Artificial controls__--____________________-__-_---_-_---_--_ 117 Design of artificial controls.____________-___--_-__-_--__ 117 High-water controls________________________--__-___------__ 118 Dams__---_--__-_--__-_-_-__---_----_-----_---------- 120 Contractions._________________________________________ 121 Bends in channel_____-_________-_-_-__-_----_----____- 122 Channel controls for high stages___________--______-_____ 122 Shifting controls_________________________________________ 125 Effect of scour_______________________ ____ . 126 Effect of fill__________-____________-_------------__--_ 126 Shifts in the channel above the control.__________________ 127 Overflow---_____________________-----____ 127 Effect of ice on the stage-discharge relation.______________ 128 Vegetal and aquatic growths.___________________________ 130 Slope-stage-discharge relations at gaging stations affected by variable slopes._________________-_- ____________-____-_--_-_---__--_ 130 Variable slopes caused by backwater.________________________ 132 Velocity-head increment to slope________________________ 135 Relation between discharge and fall______________________ 135 Curves of relation_______________________________-__._ . 137 Constant-fall stage-discharge relation ________________ 139 VI CONTENTS Flow characteristics in open channels Continued. Slope-stage-discharge relations Continued. Variable slopes caused by backwater Continued. Curves of relation Continued.