USGS Methodologies Attachment.pdf

Measurement and Computation of Streamflow: Volume 1.

Meast1re111ent of Stage and Discharge

By S. E. RANTZ llnd others

GEOLOGlCAL SURVEY WATER-SUPPLY PAPER 2175

EUSGS

science for a changing world

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1982

http://www.usgs.gov

UNITED STATES DEPARTMENT OF THE INTERIOR

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY

Dallas L. Peck, Director

First printing 1982

Second printing 1983

Library of Congress Cataloging in Publication Data

Measurement and computation of streamflow.

(Geological Survey Water-Supply Paper 2175)

Includes bibliographies.

Contents: v. 1. Measurement of stage and discharge.-

v. 2. Computation of discharge. 1. Stream measurements.

I. Rantz, S. E. (Saul Edward), 1911-

TCl 75.M42 551.48'3'0287 . II. Series.

81-607309

AACR2

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402

PREFACE

The science and, in part, art of stream gaging has evolved through the years, largely from the collective experiences and innovations of its practitioners. The earliest truly comprehensive manual on stream-gaging procedures and equipment, based on techniques de veloped up to that time, was published in 1943 by the Geological Survey as Water-Supply Paper 888, "Stream-Gaging Procedures," by D. M. Corbett and others. That report was an instant classic; it was received enthusiastically by the hydraulic-engineering profession throughout the world and became a major training document for at least two generations of stream gagers, hydrologists, and hydraulic engineers, both in the United States and abroad.

The need for updating Water-Supply Paper 888 has been obvious for some time as a result of later developments in stream-gaging techniques and equipment. Furthermore, it has been felt for some time that the scope of that report should be expanded to cover not only the newer field techniques but also the office procedures required to produce a published annual record of stream discharge. In recognition of those needs, the Geological Survey has sporadically produced sup plementary reports that update the description of specific techniques and equipment or that describe specific field or office procedures not covered by Water-Supply Paper 888. These reports-some adminis trative, some open-file, and others in the published series titled "Techniques of Water-Resources Investigations" -are fragmentary in the sense that they deal only with selected aspects of the broad subject of stream gaging. Similar, but less detailed, reports on selected topics have also been produced by international agencies in the form of Technical Notes by the World Meteorological Organiza tion and in the form of Recommendations and Standards by the In ternational Standards Organization.

The present report evolved from that background. Its two volumes provide a comprehensive compilation of time-tested techniques pre sented as an up-to-date (1980) standardized manual of stream-gaging procedures.

Acknowledgments.-The material presented in the manual is based on the work of many hydraulic engineers and technicians, each of whom has contributed to the current state-of-the-art in the meas urement and computation of streamflow. Many of those who contrib uted directly to the manual are listed in the references appended to each chapter. However, the authors wish to acknowledge a special group of colleagues who have made major contributions to this man ual in the form of written (cited) methods and techniques, significant suggestions for correction and revision of the manuscript and illus-

III

IV PREFACE

trations, and all-out efforts to bring about development and publica-tion of the material. These colleagues include:

Harry H. Barnes, Jr. Thomas J. Buchanan Rolland W. Carter Frederick A. Kilpatrick George F. Smoot Ernest D. Cobb Howard F. Matthai Manual A. Benson Alvin F. Pendleton, Jr. Tate Dalrymple Harry Hulsing Carl E. Kindsvater G. Lawrence Bodhaine Hubert J. Tracy Jacob Davidian James F. Wilson The authors also wish to acknowledge with thanks the suggestions of their many other colleagues, who are too numerous to mention.

CONTENTS

[Art& headmgs are hsted in the table of contents only m the volume of the manual m which they occur, but all chapter titles for the two volumes are hsted ,n both volumes A complete Index covermg both volumes of the manual appears m each volume 1

VOLUME 1. MEASUREMENT OF STAGE AND DISCHARGE

Page

Preface-------------------------------------------------------------------- III Conversion factors _-----------____-___-------------------~----------------XIV

Chapter l.-Introduction Purposeofthemanual ____----------__________________________------------ Scopeofthemanual-------------------------------------------------------- Streamflow records ________-_-_----_-______________________---------------- General stream-gaging procedures _- ____________________________ ------------ Selectedreference----------------------------------------------------------

Chapter 2.-Selection of Gaging-Station Sites Introduction ------__________-_--____________________---------------------- Considerations in specific site selection __________________ ---------__-_-- ___-_ Selected references ________________--______________________----------------

Chapter 3.-Gaging-Station Controls Typesofcontrol----__------------------------------------------------------ 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....------ Summary__-_-__---------------------------------------------------

Design of an artificial control --- _________ -_-----------_- ______-________ Selected references _--_---__-_____-_-______________________----------------

Chapter 4.-Measurement of Stage General ___.__-__---------_-____________________-------------------------- Datum of gage -__-____________-_-_____________________-------------------- Nonrecording stream-gaging stations _- ______________ -----------__--_- _-____-

Staffgage __________________-_---------------------------------------- Wire-weightgage-_-_-------------------------------------------------- Float-tape gage-------------------------------------------------------- Electric-tapegage------------------------------------------------------ Chain gage------ ____ ------- ____ -_-___--_----------------- ____ -- _____ -_

Recording stream-gaging stations --_--__------_-_--------------------------

V

VI CONTENTS

Recording stream-gaging stations-continued Page Methods of sensing stage for automatic recording __-_-_-_________---_____ 32

Float sensor ----___---------___----------------~-----~~--~-------- 32 Bubble-gage sensor _------___-------___---------------------------- 32

Water-stagerecorders___----_____-------_____________-_______---------- 34 Digitalrecorder_____----_______________________-------------------- 36 Graphic recorder ----_-_-----_-____--____________________---------- 39

Stillingwells_----______----_________________________--------~-~------- 41 Instrumentshelters----------------------------__------------------------ 51 Reference and auxiliary gages at recording gaging stations _-_________-__ 53 Telemeteringsystems___-----_____------_____________-_______---~------ 54

Position-motor system -______-------__---------------------------- 55 Impulse system------------------------_-____-------~---~---------~~--- 55 Telemarksystem ___---_______-----______________________-~-------- 55 Resistancesystem___------____------------------~-~----------~----- 57 Satellite data-collection system __------ _____ ---- _-______ -- __-___ --- 57

Operation of a recording stream-gaging station -- -_____ --- ________ -- _--____ _- 59 Factors affecting the accuracy of the stage record __-__ -_--_ _-______ - ___-____ - 63

Nonrecordinggages-____------____------~-~--------------------~------- 64 Staffgage -----____------____--------~-------------------~--~----- 64 Wire-weight gage ___-- ________ --- ______ --------__---------_-------- 64 Float-tapegage_------_-_------___-____________________---~-------- 65 Electric-tapegage___-----_____-------____________-_______---------- 66 Chaingage-----____-------------------------------~--------------- 67

Accuracyoffloat-operated recorders _-___----_-_--_-_-__________________ 68 Accuracy ofbubble-gage recorders _------___---------~~------------~~--- 71

Special purpose gages --_____-----_____------~-~---------------------------- 74 ModelTrecorder -______---_______----~--~~~--------~------------------ 74 SRrecorder____-----_____________-_________---------------------------- 76 Crest-stage gage -_-_---_-_--___-________________________-----~-------- 77

Selectedreferences -----____------_-__--------------------~-----------~---- 78

Chapter L-Measurement of Discharge by Conventional Current-Meter Method

Introduction -----____-------__--____________________---------------------- 79 General description of a conventional current-meter measurement of discharge 80 Instruments and equipment -___-------___------ ____-_ ---- ______ --- _--____ -- 82

Current meters ---------__-_------_---------------------------~----~--- 84 Vertical-axiscurrentmeters-------------------------____------___ 85 Horizontal-axis current meters- ____ ----- ____ ------ -_-__ ----- _-____ -- 88 Comparison of performance of vertical-axis and horizontal-axis current’ meters __-----____-----________________________---------~-------- 89 Opticalcurrentmeter-------------------------------____-----------~-- 91 Care ofthe current meter -----_--------_-_------------------------- 93 Rating of current meters _---- __-_ ------ -_-___ -_- _-_____ --- -____ _-- 94

Sounding equipment --__----------_-------~-------------~------------- 97 Wadingrods _--------__------_------------------------------------ 97 Sounding weights and accessories _-----_____-------________________ 101 Soundingreels __--- _-__ -_---- -___ ----- __-___ ---- -_--_ __--- __-__ --- 102 Handlines --____---__-_-_----_------------------------------------ 104 Sonic sounder-_______--_-_----------------------------------------- 108

CONTENTS VII

Instruments and equipment-Continued Width-measuringequipment-------------------------------------------- Equipmentassemblies--------------------------------------------------

Cablewayequipment ----------------_-______________________------ Bridgeequipment---------------_-----------------------~---------- Boatequipment---------------------------------------------------- Iceequipment __-_-_---------------------------------------------- Velocity-azimuth-depth assembly------------------------------------

Miscellaneousequipment --------_--_--------____________________------ Measurementofvelocity----_--------------------------~--------------------

Vertical-velocity curve method ____-__-- - ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Two-pointmethod_-_______-________-_---------------------------------- Six-tenths.depthmethod------------------------------------------------ Three-point method ---------------------------------------------------- Two-tenths-depthmethod --------------------____________________------ Subsurface-velocity method __-_--_-------------____________________---- Surface-velocity method ------------------------------------------------ Integration method -------_-_-_-_--_-_-____________________~~~~~~~~~~~~ Five-pointmethod------------------------------------------------------ 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 ____-_--_----------------------- Networksofcurrentmeters --------------__----____________________----

Special problems in conventional current-meter measurements---------------- Measurement of deep, swift streams --------------------________________

Case A. Depthcanbesounded-------------------------------------- Case B. Depth cannot be sounded, but standard cross section is available Case C. Depth cannot be sounded and no standard cross section is avail-able _-___-____-_____________________________-------------------- Case I). Meter cannot be submerged -------_----------_-____________

Computation of mean gage height of a discharge measurement-____--_-___ Measurement procedures during rapidly changing stage _-_--_-_-_----_--_

Case A. Largestreams ----------------_-_-____________________---- Case B. Small streams -_-_----_-_--__--__- _-___ - ~~~~~~~~~_~~~~~~~~

Correction of discharge for storage during measurement ~~~~~~~~~__~~~____ Summary of factors affecting the accuracy of a discharge measurement -------- Accuracy of a clischarge measurement made under average conditions -------- Selected references ____________--------------------------------------------

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

Page i34

Introduction -------------_____-_------------------------------------------ 183 Theoryofthe moving-boat method ------_-_-____--________________________-- 184 Equipment--______-------_________----------------------~-------------------- 187

Vane and angle indicator ____________ -----------_-___-_-_-------------- 187

VIII CONTENTS

Equipment-Continued Page

Current meter -__-_-__________________________________---------------- 188 Rate indicator and counter _____________ -----------_- ______ _ ______ - ______ 190 Batterycharger_-----------------------------~-------------~---~-~--~-- 193 Sonicsounder-----------------------------~-~-----------------------~~- 193 Boat______-_--_____-___-____________________--------~~--~-~~~~-------- 195

Measurement procedures _-____-_--_-_-_--------------~~--~-~~--~~-~------- 197 Selection and preparation of the measurement site ______________________ 197 Preparationoftheequipment --_-__--____------------------------------ 198

Assembly of the equipment ______-_- ---_-_--__- _________ - _________- 199 Selection of the instrument settings __-_---------------------------- 200

Function of the crew members __-__-___ -----_------_--___ _______ - ____ ___ 201 Boatoperator------------------_-_-~~--~-------------------- 201 Angle observer -_-__-_-____-__-__-_____________________------------ 202 Notekeeper------------------------~~~----------------------------- 203

Computation of the discharge measurement---------------------------------- 204 Computation of unadjusted discharge___----------------- ____________-___ 204 Adjustment of total width and area-----_-_------------------------------ 207 Adjustment of mean velocity and total discharge __-_____________________ 208

Determination of vertical-velocity adjustment factor _ _________________ 210 Application of velocity adjustment to computed discharge ____________ 211

Selectedreferences --------------------____________________---------------- 211

Chapter 7.-Measurement of Discharge by Tracer Dilution

General _____-_-____-_-----------------~~~~~~~~~~~~---------------------~- 211 Theory of tracer-dilution methods -------_____________---------------------- 212

Theory of the constant-rate-injection method __________-_---------------- 213 Theory of the sudden-injection method -~-----------------------~-------- 214 Factors affecting the accuracy of tracer-dilution methods------------~~---- 215

Turbidity---------_____________-_-------~---~~~~~~~~~~-~~~~~~~~~~---------- 215 Lossoftracer-----_____________-_----------------------------------------- 216 Criteria for satisfactory mixing -----__________--------------------- 216

Calibration of measurement reach -------_____-_---------------------------- 220 Effect of inflow or outflow between injection and sampling sites ______--______ 222 Measurement of discharge by fluorescent-dye dilution ________~~-------------- 223

Fluorescent dyes --____________---_--____________________~------------- 223 Fluorometer ------__________________________________----~------------- 223

Description of fluorometer ________ ~_-~ __________________ ~~~~-~------ 224 Effectoftemperature on fluorometry -__________________~------------ 226 Calibration characteristics of the flurometer ~---------------~~~_____ 226 Preparation of standard dye solutions for flurometer calibration ______ 228 Operationofthe fluorometer--------____________________---------------------- 231

Dye-injectionapparatus ____________-_-_________________________--~----- 232 Mariotte vessel ---____________------~~~-~~~~~~~~~----------------~- 232 Floatingsiphon---_____________-___-------------------------------- 233 Pressuretank-----___________-------------------------------------- 234

Determination of quantities of fluorescent dye for measuring discharge __-_ 235 Quantity of dye needed for measurement by the constant-rate-injection method----------__________-_---_--------~~~~~~-~-~~~~~~~~~~~---------- 235 Quantity of dye needed for measurement by the sudden-injection method 236

CONTENTS IX

Measurement of discharge by fluorescent+lye dilution-Continued Page

Procedures for measuring discharge by the dye-dilution method --____---- 237 Field procedures ____--------______--------~~--------------~------- 237 Analysis and computations --_____-_-------___--------------------- 240 Sample computation-constant-rate-injection method ___-_____--_-__- 241

Simplified procedures for making numerous dye-dilution measurements of discharge_----------------------------------------------------------- 246

Measurement of discharge by sodium dichromate dilution ___--------___-_---- 249 General __--_________---________________________---------------------- 249 Principle of calorimetric analysis ______ - _________ --- _______ ------ ____ ---- 249 Method of analysis by calorimeter ----- _______ ----- _______ ------ ____ ---- 250

Measurement of discharge by salt dilution ______------______---------------- 250 General ----____--------________________________---------------------- 250 Preparation and injection of the concentrated salt solution---------------- 251 Measurement of relative conductance at the sampling site -____-_---____-_ 252 Computation ofdischarge ____________-___________________________------ 255

Measurement of discharge by dilution of radioactive tracers ___-_______ - __-___ 256 General ________________________________________---------------------- 256 Methodology ____--------___----------~---------~---------------------- 258

Selected references __------_____---------~--------------------------------- 259

Chapter 8.--Measurement of Discharge by Miscellaneous Methods

General ---_____----------______________________-------------------------- 260 Floats -----_______-------_____________________---------------------------- 261 Volumetric measurement --__----------__-_------~----------~-------------- 262 Portable weir plate _____--_________---------------------------------------- 263 Portable Parshall flume ---- ______ ------- ____ --------__------- ___-- ---_- __-_ 265 Measurement, of unstable flow-roll waves or slug flow ____------_-_-----__-- 268

Characteristics of unstable flow __________________________ ------__----___ 268 Determination of discharge ----------___-------____________________---- 269 Examples of discharge determination ____ ----- ______ ------ -_-_-______-___ 270 Proposed instrumentation __________-_____________________________------ 272

Selected references __-__---__________-_____________________---------------- 272

Chapter 9.-Indirect Determination of Peak Discharge

Introduction ____________-___________________________---------------------- 273 Collection of field data----- ___________ -_- __________ --- _________ ---- ____ ----- 274 Slope-areamethod ---____-----------______________________--~------------- 274 Contracted-opening method ____ --------- _______ ------ _____ -------___------- 277 Flow over dams and weirs- ___________ -_- ___________ - ___________ --- _____ -_-- 279 Flow through culverts----- _____ --------- ________ ----- ____ -------___------__ 279

General classification of flow--__-_------------------------------- ______- 281 Estimating discharge from superelevation in bends ----____-_------__-------- 281 Selected references -------___-----------~~~------------~----------~-------- 284

Index

VOLUME 2. COMPUTATION OF DISCHARGE

Chapter Page

10 Discharge ratings using simple stage-discharge relations --___--- 285

X CONTENTS

11 Discharge ratings using slope as a parameter ------------------ 390 12 Discharge ratings using a velocity index as a parameter -------- 429 13 Discharge ratings for tidal streams ---------------------------- 471 14 Discharge ratings for miscellaneous hydraulic facilities -------- 486 15 Computation of discharge records -- ______-________________ -_--- 544 16 Presentation and publication of stream-gaging data ------------ 601

ILLUSTRATIONS

FIGURE 1. Gage, concrete control, outside gage on bridge, and an engineer making a wading measurement, Kaskaskia River at Bondville, 111 ---------------------~------------------------~---------

2. Gage and natural control, Little Spokane River at Elk, Wash_---

3. Rectangular weir on Trifolium Drain 23 of Imperial Irrigation Dis-trict, near Westmorland, Calif -----_________________________

4. Four-foot Parshall flume discharging 62 ft”/s (1.76 n-&s) under free-flow conditions ----------_____----------------------~~~

5. Flow through a 3-ft trapezoidal supercritical-flow flume showing transition from subcritical to supercritical flow _________-_---

6. Concrete artificial control on Mill Creek near Coshocton, Ohio _-

7. Artificial control on Delaware River near Red Bluff, N. Mex., with shallow V notch in the broad-crested weir _______-------------

8. Cover of book and weekly report card for recording manual gage observations --___________-_-________________________----

9. Vertical staff gage------------____---------------------~~~~~~~

10. Type-A wire-weight gage-----________~_-----------------------

11. Float-tape gage _____--------___________________________-----~

12. Electric-tape gage ________ --- ________________ __-_-------------

13. Chaingage -_______---------_______________________-------~~~

14. Major units of the bubble gage ___________ ------------------~__

15. Installation of bubble orifice in unstable streambed ______------

16. Digitalrecorder___----------_-_________________________-~~~~~

17. Sample digitalrecordertape ~__________________---------------

18. Digital-recorder timer _______________-________________________

19. Continuous strip-chart recorder ___-___________ -----------------

20. Horizontal-drum recorder _--___-__________-------------------

21. Section of a typical strip chart ________--~----------------~-~~~

22. Reinforced-concrete well and shelter -------------------~~_____

23. Concrete well and wooden shelter with asphalt-shingle siding __

24. Corrugated-galvanized-steel-pipe well and shelter ___-----------

25. Concrete-pipe well and shelter ____-_______ -----------------___

26. Concrete-block shelter _------ ____________ ------------------___

27. Steel-pipe well and look-in shelter attached to bridge abutment--

28. Corrugated-steel-pipe well and wooden shelter attached to bridge pier ----_________--_-_______________________-------------- 49

29. Flushing system for intakes ~-----------___~_---------------~~ 50

30. Statictubeforintakes____--------------_-___________________ 50

31. Typical bubble-gage installation __------ ___________ -_--------- 52

32. Telemarkgage --_________------------------~-----------~-~~~ 56

33. Resistance system transmitter unit _____ _ _____________ -_------- 57

34. Resistance system indicator unit ______ -- ____-________ -_------- 58

CONTENTS XI

FIGURE 35. Sample log sheet for bubble gage ____________-_---------------- 62

36. Diagram for determining allowable length of bubble tubing for maximum friction error of 0.01 ft- ___________ -_-_------------ 72

37. Diagram for determining required bubble rate_______----------- 73

38. ModelT recorder -------------___________________________---- 75

39. ModelSRrecorder-__-_-_-_____-------------------------------- 76

40. Crest-stagegage---------------_------------------------------ 78

41. Definition sketch of midsection method of computing cross-section area for discharge measurements __------------------________ 81

42. Computation notes of a current-meter measurement by the midsec-tionmethod__-___---------------~~~------------------------ 83

43. Comparison of pulsations for two different mean velocities mea-sured in a laboratory flume, 12 ft wide ------------------_-__ 85

44. Price type AA meter, top; Price pygmy meter, bottom ___- ___-_- 86

45. Vane ice meter, top; vane meter with cable-suspension yoke, bot-torn------------______-------------------~~~~~~~-~----------- 87

46. Ottcurrentmeter ____---------___________________________--~- 88

47. Velocity components measured by Ott and Price current meters 88

48. Hoff current meter ----------- _________ ------------_-_- ____ -_ 89

49. Comparison of mean velocities measured simultaneously by var-ious current meters during 2-min periods, Stella Niagara section, Panel point5 __----------------______________________--~--- SO

50. Optical current meter ____ ----- _______________ -_-------------- 91

51. Current-meter rating table----- _____________ --------------_-_- 95

52. Top-setting wading rod with meter attached-------------------- 98

53. Round wading rod with meter attached --------------_-________ 99

54. Lower section of ice rod for use with vane ice meter ____________ 100

55. Lower section of ice rod for use with Price meter--------_-______ 101

56. Columbus 15, 30-, 50-, 75-, and loo-lb sounding weights---_---- 102

57. Sounding-weight hangers and hanger pins ------------‘--___-_- 103

58. Canfield reel _----------------___---------------- ____________ 104

59. E56 reel----____-_---_-------------------------------------- 105

60. Computing depth indicator ----- _______________ ------------_-__ 105

61. Handline ____-----------------~~~~~-------------------------- 106

62. Handline in use from a bridge -___-_---------------------~---- 107

63. Handlinereels ____-_---------_________________________------ 108

64. Sounding weight with compass and sonic transducer ready for as-sembly ________---------------~~~--------------~----------- 109

65. Sonic measuring assembly ---___-__------_-_- _________________ 109

66. Tag-line reels ________________ - _____________ -_-_-_------------ 111

67. Sitdo n cable car __----------- ___________ -----------------___ 112

68. Standup cable car -------------____--_------------------------ 112

69. Cable-car puller for follower-brake cable cars, left; for standard cars,right ----______----------____________________--~~-~-- 113

70. Power-operated cable cars ----- ____ -----------___- ____________ 114

71. Sitdown cable car with Canfield reel clamped to side of car ______ 115

72. Portable reel seat on sitdown-type cable car -__ __________-______ 116

73. Carrier (bank-operated) cableway __________ -_------------_- ____ 117

74. Type-A crane with three-wheel base __----------_- ____________ 118

75. Type-A crane with four-wheel base with boom in retracted position 119

76. Bridge board in use _________ - ________________ ---------------- 120

77. Truck-mounted crane used on the Mississippi River ____________ 121

78. Horizontal-axis boat tag-line reel without a brake ___.__________ 122

XII CONTENTS

FIGURE 79. Horizontal-axis boat tag-line reel with a brake --_____--_____-- 123

80. Vertical-axis boat tag-line reel - ____ ----___-_- _____ --- ____ --___ 124

81. Boom and crosspiece for use on boats __- ______ _ ________________ 125

82. Measuring equipment set up in a boat -_-----____----____-____ 126

83. Gasoline-powered ice drill _~---____---- -____ - __-____ - ________- 127

84. Collapsible reel support and ice-weight assembly _----_____-___ 128

85. Velocity-azimuth-depth assembly __-----__----____---__________ 129

86. Automatic counter (left) and headphone (right) ____---____---__ 130

87. Ice creepers for boots and waders ___-_-- -___ -- ______ -- -________ 131

88. Typical vertical-velocity curve -__------__----____------------- 133

89. Relation of surface-velocity coefficient to distance from vertical wall of a smooth rectangular channel - ____ -- ______ -- _________ 137

90. Measurement of horizontal angle with measurement-note sheet __ 143

91. Measurement of horizontal angle with folding foot-rule-------_-- 144

92. Wading measurement using top-setting rod ----___-----___---__ 145

93. Ice rod being used to support current meter for a discharge mea-surement, top; ice drill being used to cut holes, bottom __-___-_ 152

94. Method of computing meter settings for measurements under ice cover___----____---___----~-~-----~~----------------------- 153

95. Typical vertical-velocity curve under ice cover --_____--______-__ 154

96. Part of notes for discharge measurement under ice cover --____-- 156

97. Determining position in the cross section, stadia method _--__-__ 157

98. Determining position in the cross section, angular method ____-_ 157

99. Position of sounding weight and line in deep, swift water-------- 160

100. Sketch of geometry of relation of actual to measured vertical angle when flow direction is not normal to measurement section __-_ 166

101. Computation of discharge-weighted mean gage height __---___-- 172

102. Discharge-measurement notes with discharge adjusted for channel storage ---------------_-------~-------------------------~-- 178

103. Sketch of stream with markers -- ______ - _______-_______---_____ 185

104. Diagram of velocity vectors ----____--- ______ - ___-___________- 186

105. Sketch of boat showing equipment -----__----- _____ --_ ________ 188

106. Component propeller-type meter _~-----____--- _______________-

107. Control panel of rate indicator and counter ----_------____---__

108. Sample tables of meter rating, Lb, and sine o( _- ________________

109. Sonic sounder and control panel ___---- _____ -- _____ ___ ________

110. Boat with mounted vane assembly ------~------__~---_________

111. Detailed view of vane-mounting assembly ___~~- _______________-

112. Definition sketch of midsection method of computation superimposed on a facsimile of a sonic-sounder chart---------- 205

113. Sample computation notes of a moving-boat measurement _____- 206

114. Comparison of actual and computed values of incremental widths 209

115. Constant-rate-injection system ___----___------__--____________ 213

116. Concentration-time curve at downstream sampling site for constant-rate injection __--------------_---_________ _-_______ 214

117. Concentration-time curve at downstream sampling site for sudden injection _------__-----_-_---____________________-------~-- 215

118. Comparison of concentration-time curves obtained by SI and CR1 methods, observed at three points in sampling cross section, for sampling reaches of three different lengths --_ _-___ -- _______- 218

119. Concentration-distribution curve illustrating the graphical method of determining the percentage of mixing ___________________- 220

CONTENTS XIII

FIGURE 120. Schematic diagram of the fluorometer--------- _________________ 224

121. Mariotte vessel (constant-head device) --------------_-_---____ 232

122. Floating siphon (constant-head device) --------------_-________ 234

123. Pressurized constant-rate injection tanks for injection of dye into streams---------------------------------------------------- 235

124. Sample analysis sheet used for computing discharge by the constant-rate-injection method of dye dilution ----_--__-_-____ 244

125. Dye-injection rate of various stock dye concentrations related to estimated stream discharge ----------------_-______________ 248

126. Schematic diagram of conductance meter used in salt-dilution method of measuring discharge_-____------------------------ 253

127. Sample computation of discharge using salt dilution in the sudden-injection method ------- ___________ -_-_--------_---__ 256

128. Curve of relative conductance versus time for the ionic wave in the sample problem ----------------________________________---- 257

129. Portable weir-plate sizes - ______ -----------------_-_- _____ - ____ 264

130. Working drawing of a modified 3-in Parshall flume ____________ 267

131. Modified 3-in Parshall flume installed for measuring discharge -_ 268

132. Schematic sketch of longitudinal water-surface profile during pul-sating flow ________________________________________-------- 269

133. Discharge hydrograph at Santa Anita Wash above Sierra Madre

Wash, Calif., April 16, 1965, and plot of discharges computed fromobservationsofflow------_-____----------------------~- 271

134. Definition sketch of a slope-area reach ------------____________ 276

135. Definition sketch of an open-channel contraction-- ______________ 278

136. Graphical presentation of the Bernoulli equation in culvert flow 280

137. Classification of culvert flow ___----_- _________________________ 282

138. Idealized sketch of a bend (plan view) ----_-_- __________________ 283

TABLES

Page

TABLE 1. Range of velocities that can be measured with optical current meter----------______-------------------~-~----------------- 92

2. Coefficients for standard vertical-velocity curve --------------__ 133

3. Current-meter and velocity-measurement method for various depths (wading measurement) --____________---------------- 145

4. Velocity-measurement method for various meter suspensions and depths --------________________________________----------~- 148

5. Air-correction table, giving difference, in feet, between vertical length and slant length of sounding line above water surface for selected vertical angles -- ______ ------------ ________________ 161

6. Air-correction table, giving difference, m meters, between vertical length and slant length of soundmg line above water surface for selected vertical angles ____ ---- __________________ ---------- 162

7. Wet-lme table, giving difference, in feet, between wet-line length and vertical depth for selected vertical angles -- ______________ 164

8. Wet-line table, giving difference, in meters, between wet-line length and vertical depth for selected vertical angles---------- 165

9. Degrees to be added to observed vertical angles to obtain actual vertical angles when flow direction is not normal to measure-mentsection --____------------______________________------ 167

XIV CONTENTS

TABLE 10. Summary table for setting the meter at 0.8-depth position in deep, swift streams -------------_____---------------------~-~~~~~ 168

11. Registration errors, in percentage of stream velocity, caused by vertical motion of current meter __________~~_--------------- 181

12. Spacing of vertical-line markings, in inches, on the sonic-sounder chart for various combinations of chart speed and range distance 195

13. Temperature-correction coefficients for Rhodamine WT dye ___-_- 227

14. Rating table for 3-in modified Parshall flume __________-__-_-__ 266

15. Characteristics of types of culvert flow __________-__-_-________ 281

CONVERSION FACTORS

[Factors for convertmg Inch-pound to metnc “ruts are shown to four slgnlficant figures However, ,n the text the metrx equwalents, where shown, are carned only to the number of svgnficant figures consistent wth the values for the Enghsh umts.]

Inch-pound Multrply by-acres 4.047 x 103 acre-ft (acre-feet) 1.233x lo3 acre-ftiyr (acre feet per year) 1.233x lo” ft (feet) 3.048x 10-l ft/hr (feet per hour) 3.048x 10-l ft/s (feet per second) 3.048x 10-l ft”/s (cubic feet per second) 2.832 x lo-” in (inches) 2.540x 10 lb (pounds) 4.536x 10-l mi (miles) 1.609 mi’ (square miles) 2.590 02 (ounces) 2.835x 1O-y

M&lC m2 (square meters) n? (cubic meters) mVyr (cubic meters per year) m (meters) m/hr (meters per hour) m/s (meters per second) mYs (cubic meters per second) mm (millimeters) kg (kilograms) km (kilometers) km’ (square kilometers) kg (kilograms)

MEASUREMENT AND COMPUTATION

OF STREAMFLOW

VOLUME 1. MEASUREMENT OF STAGE AND

DISCHARGE

By S. E. RANTZ and others

CHAPTER I.-INTRODUCTION

PURPOSE OF THE MANUAL

The purpose of this manual is to provide a comprehensive descrip-tion of state-of-the-art standardized stream-gaging procedures, within the scope described below. The manual is intended for use as a training guide and reference text, primarily for hydraulic engineers and technicians in the U.S. Geological Survey, but the manual is also appropriate for use by other stream-gaging practitioners, both in the United States and elsewhere.

SCOPE OF THE MANUAL

The technical work involved in obtaining systematic records of streamflow is discussed, in two volumes, in accordance with the fol-lowing six major topics:

Volume 1. Measurement of stage and discharge

a. Selection of gaging-station sites

b. Measurement of stage

c. Measurement of discharge

Volume 2. Computation of discharge

d. Computation of the stage-discharge relation

e. Computation of daily-discharge records

f. Presentation and publication of stream-gaging data

In order to make the text as broadly usable as possible, discussions of instrumentation and measurement are aimed at the technician, and discussions of computational procedure are aimed at the junior engineer who has a background in basic hydraulics.

Many of the procedures for determining discharge that are dis-cussed in volume 2 require specialized instrumentation to obtain field data that supplement the observation of stage. The descriptions of such specialized equipment and associated observational techniques

2 MEASUREMENT OF STAGE AND DISCHARGE

are given in appropriate chapters in volume 2 so that the reader may have unified discussions of the methodologies applicable to each type of problem in determining discharge.

In general the authors have attempted to prepare a manual that will stand independently-references are given to supplementary published material, but the reader should find relatively few occa-sions when there is pressing need to consult those references. There are three notable exceptions to that statement.

1. The subject of indirect determination of peak discharge (v. 1, chap.

9) is treated here only in brief because of space limitations; the subject is treated fully in five reports in the Geological Survey report series, “Techniques of Water-Resources Investigations.” The five reports are named in the reference section of chapter 9.

2. Among the methods discussed in this manual for computing the discharge of tidal streams are four mathematical techniques for evaluating the differential equations of unsteady flow (v. 2, chap.

13). The four techniques are given only cursory treatment because a detailed description of the complex mathematical techniques is considered to be beyond the scope of the manual.

3. The processing of streamflow records by digital computer (v. 2, chap. 15) is a subject that is given only generalized treatment here.

It was not practicable to include a detailed description of each step in the sequence of operation of an automated computing system because of space limitations, and also because the particulars of each step are somewhat in a state of flux in response to continual improvement in storage and access procedures.

STREAMFLOW RECORDS

Streamflow serves man in many ways. It supplies water for domes-tic, commercial, and industrial use; irrigation water for crops; dilu-tion and transport for removal of wastes; energy for hydroelectric power generation; transport channels for commerce; and a medium for recreation. Records of streamflow are the basic data used in devel-oping reliable surface-water supplies because the records provide in-formation on the availability of streamflow and its variability in time and space. The records are therefore used in the planning and design of surface-water related projects, and they are also used in the man-agement or operation of such projects after the projects have been built or activated.

Streamflow, when it occurs in excess, can create a hazard-floods cause extensive damage and hardship. Records of flood events ob-tained at gaging stations serve as the basis for the design of bridges, culverts, dams, and flood-control reservoirs, and for flood-plain de-lineation and flood-warning systems.

1. INTRODUCTION 3

The streamflow records referred to above are primarily continuous records of discharge at stream-gaging stations, a gaging station being a stream-site installation so instrumented and operated that a con-tinuous record of stage and discharge can be obtained. Networks of stream-gaging stations are designed to meet the various demands for streamflow information, including inventory of the total water re-source. The networks of continuous-record stations, however, are often augmented by auxiliary networks of partial-record stations to fill a particular need for streamflow information at relatively low cost. For example, an auxiliary network of sites, instrumented and operated to provide only instantaneous peak-discharge data, is often established to obtain basic information for use in regional flood-frequency studies. An auxiliary network of uninstrumented sites for measuring low flow only is often established to provide basic data for use in regional studies of drought and of fish and wildlife mainte-nance or enhancement.

GENERAL STREAM-GAGING PROCEDURES

After the general location of a gaging station has been determined from a consideration of the need for streamflow data, its precise loca-tion is so selected as to take advantage of the best locally available conditions for stage and discharge measurement and for developing a stable stage-discharge relation.

A continuous record of stage is obtained by installing instruments that sense and record the water-surface elevation in the stream. Dis-charge measurements are initially made at various stages to define the relation between stage and discharge. Discharge measurements are then made at periodic intervals, usually monthly, to verify the stage-discharge relation or to define any change in the relation caused by changes in channel geometry and (or) channel roughness.

At many sites the discharge is not a unique function of stage; vari-ables other than stage must also be continuously measured to obtain a discharge record. For example, stream slope is measured by the installation of a downstream auxiliary stage gage at stations where variable backwater occurs. At other sites a continuous measure of stream velocity at a point in the cross section is obtained and used as an additional variable in the discharge rating. The rate of change of stage can be an important variable where flow is unsteady and chan-nel slopes are flat.

Artificial controls such as low weirs or flumes are constructed at some stations to stabilize the stage-discharge relations in the low-flow range. These control structures are calibrated by stage and dis-charge measurements in the field.

The data obtained at the gaging station are reviewed and analyzed

4 MEASUREMENT OF STAGE AND DISCHARGE

by engineering personnel at the end of the water year. Discharge ratings are established, and the gage-height record is reduced to mean values for selected time periods. The mean discharge for each day and extremes of discharge for the year are computed. The data are then prepared for publication.

SELECTED REFERENCE

Carter, R. W., and Davidian, Jacob, 1968, General procedure for gaging streams: U.S.

Geol. Survey Techniques Water-Resources Inv., book 3, chap. A6, p. 1-2.

CHAPTER 2.--SELECTION OF GAGING-STATION

SITES

INTRODUCTION

The general location of a gaging station is dependent on the specific purpose of the streamflow record. If the streamflow record is needed for the design or operation of a water project, such as a dam and reservoir, the general location of the gaging station obviously will be in the vicinity of the water project. The selection of a gaging-station site becomes complicated, however, when the station is to be one of a network of stations whose records are required for study of the gen-eral hydrology of a region. Such studies are used to inventory the regional water resource and formulate long-range water-development plans. In that situation, attention to hydrologic princi-ples is required in selecting the general locations of the individual stations in the network to ensure that optimum information is ob-tained for the money spent in data collection.

A discussion of the design of gaging-station networks is beyond the scope of this manual and for the purpose of this chapter we will assume that the general location of a proposed gaging station has been determined. The discussion that follows will be concerned with the hydraulic considerations that enter into the selection of the pre-cise location of the gage to obtain the best locally available conditions for the measurement of stage and discharge and for the development of a stable discharge rating.

CONSIDERATIONS IN SPECIFIC SITE SELECTION

After the general location of a gaging station has been determined, a specific site for its installation must be selected. For example, if the outflow from a reservoir is to be gaged to provide the streamflow data needed for managing reservoir releases, the general location of the gaging station will be along the stretch of stream channel between the dam and the first stream confluence of significant size

2. SELECTION OF GAGING-STATION SITES 5

downstream from the dam. From the standpoint of convenience alone, the station should be established close to the dam, but it should be far enough downstream from the outlet gates and spillway outlet to allow the flow to become uniformly established across the entire width of the stream. On the other hand the gage should not be located so far downstream that the stage of the gaged stream may be affected by the stage of the confluent stream. Between those upstream and downstream limits for locating the gage, the hydraulic features should be investigated to obtain a site that presents the best possible conditions for stage and discharge measurement and for developing a stable stage-discharge relation. If the proposed gaging station is to be established for purely hydrologic purposes, unconnected with the de-sign or operation of a project, the general location for the gage will be the stretch of channel between two large tributary or confluent streams. The same consideration will apply in the sense that the gage should be far enough downstream from the upper tributary so that flow is fairly uniformly established across the entire width of stream, and far enough upstream from the lower stream confluence to avoid variable backwater effect. Those limits often provide a reach of chan-nel of several miles whose hydraulic features must be considered in selecting a specific site for the gage installation.

The ideal gage site satisfies the following criteria:

1. The general course of the stream is straight for about 300 ft (ap-prox. 100 m) upstream and downstream from the gage site.

2. The total flow is confined to one channel at all stages, and no flow bypasses the site as subsurface flow.

3. The streambed is not subject to scour and fill and is free of aquatic growth.

4. Banks are permanent, high enough to contain floods, and are free of brush.

5. Unchanging natural controls are present in the form of a bedrock outcrop or other stable riffle for low flow and a channel constric-tion for high flow-or a falls or cascade that is unsubmerged at all stages (chap. 3).

6. A pool is present upstream from the control at extremely low stages to ensure a recording of stage at extremely low flow, and to avoid high velocities at the streamward end of gaging-station intakes during periods of high flow.

7. The gage site is far enough upstream from the confluence with another stream or from tidal effect to avoid any variable influ-ence the other stream or the tide may have on the stage at the gage site.

8. A satisfactory reach for measuring discharge at all stages is avail-able within reasonable proximity of the gage site. (It is not nec-

6 MEASUREMENT OF STAGE AND DISCHARGE

essary that low and high flows be measured at the same stream cross section.)

9. The site is readily accessible for ease in installation and operation of the gaging station.

Rarely will an ideal site be found for a gaging station and judgment must be exercised in choosing between adequate sites, each of which has some shortcomings. Often, too, adverse conditions exist at all possible sites for installing a needed gaging station, and a poor site must be accepted. For example, all streams in a given region may have unstable beds and banks, which result in continually changing stage-discharge relations.

The reconnaissance for a gaging site properly starts in the office where the general area for the gage site is examined on topographic, geologic, and other maps. Reaches having the following pertinent characteristics should be noted: straight alinement, exposed consoli-dated rock as opposed to alluvium, banks subject to overflow, steep banks for confined flow, divided channels, possible variable backwater effect from a tributary or confluent stream or from a reser-voir, and potential sites for discharge measurement by current meter.

The more favorable sites will be given critical field examination; they should be marked on the map, access roads should be noted, and an overall route for field reconnaissance should be selected.

In the field reconnaissance the features discussed earlier are inves-tigated. With regard to low flow, a stable well-defined low-water con-trol section is sought. In the absence of such a control, the feasibility of building an artificial low-water control is investigated. If a site on a stream with a movable bed must be accepted-for example, a sand-channel stream-it is best to locate the gage in as uniform a reach as possible, away from obstructions in the channel, such as bridges, which tend to intensify scour and fill. (See page 377.