Utah State University

DigitalCommons@USU

Reports Utah Water Research Laboratory

January 1955

Measurement of Irrigation Water

Eldon M. Stock

Follow this and additional works at: https://digitalcommons.usu.edu/water_rep

Part of the Civil and Environmental Engineering Commons, and the Water Resource Management
Commons

Recommended Citation
Stock, Eldon M., "Measurement of Irrigation Water" (1955). Reports. Paper 66.
https://digitalcommons.usu.edu/water_rep/66

This Report is brought to you for free and open access by

the Utah Water Research Laboratory at
DigitalCommons@USU. It has been accepted for
inclusion in Reports by an authorized administrator of
DigitalCommons@USU. For more information, please
contact digitalcommons@usu.edu.
Bulletin No. 5 June, 1955

MEASUREMENT
,,/
IRRIGATION WATER
IIj
ELDON M. STOCK

--/--
Published Jointly by
Utah State Engineering Experiment Station and
Utah Cooperative Extension Service
Bulletin No.5 June, 1955

Measurement
d/
Irrigation Water
bfj
ELDON M. STOCK
Professor of Civil Engineering and Collaborator,
Utah Cooperative Extension Service

Published Jointly by
Utah State Engineering Experiment Station and
Utah Cooperative Extension Service
 TABLE OF CONTENTS
Page
Foreword ... 6
AcknO\vledgements 7
List of Tables .. 3
List of Figures _ ___ 4-5
Introduction .. 8
Definition of Terms Used in ,Vater l'-lcasuremenL __ _ 9
Some Convenient Itelations __ . 10
Methods of "Tater l'-leaSllremcnts 13
Current jVleters . _______ _ 1,5
Float Measurements 17
-Weirs .... ______ _ 17
Limitations in Usc of \Veirs 20
The Weir Structure . __ .. ______ _ 20
Making a Discharge Measurement with a \Veir... 22
Hectangular \Vcir ._ ... __ . _____________________ ... __ .... ____ .. __________________ . 22
Trapezoidal or Cipolletti Weir ___ . _______ . __ 27
Ninety-Degree Triangular Notch \Veir _______ _ _. _____ . _____ 32
Hectangular Suppressed \Veir . _______________ _ 36
Hating Flumes . 41
Submerged Orifices __ _ 41
Submerged Orifice with Fixed Dimensions _______ .___ 41
Determination of Discharge . _____ .. _____ . ________ . __ ___ 43
Combination I-lead Gate and Measuring Device. 47
Commercial Gates ______ . ___________ ._ . _____________________ . 50
Pnrshall Measuring Flume ____________________________________________ . ________ . ____________ .. ______ ._ 51
Plans _.. _. _____ .. _._. _______ . __ . __ _____ . ___________________________________ . ___ 64
Forms ________________ . __ . _________________ . ____________ .. _______ . ___________________ .. ______ . ______ . _____ . 69
Dividers .. _________ . ______________________________ ._ ... ____ . ________ .. _________________________ . _____ . ___ ... ____ ____ 71
Measuring Discharge from Pipes __ . ______________________________________ ._. _________ ._. _____ .. __ ... 73
Vertical Pipes _... _____________ .____ _____ .. __ . ___ ... _________________________ . _____ ... __ .. ____ 75
Horizontal Pipes . __ . _______ .. ___ _______ . _______________ .. _______ ._ .. ______ . __ ._. _____ .. 75
Purdue Method for Horizontal Pipes ___________________ . ______ ._. ______ . __________ . ______ . 78

-2-
 LIST OF TABLES
Number Title Page
1 Conversion table of flow units ___________________________________________________ 10
2 Hecommended sizes of rectangular weirs ________________________________ 22
3 Flow over rectangular contracted weirs in cubic feet
per second ____________________________________________________________________________ 24
4 Flow over Cipolletti vVeir in cubic feet per second ____________________ 29
5 Recoll11uended sizes of CipoJletti \veirs ___________ ...... _____________________ 32
6 Flow over 90-degree triangular notch weir in cubic
feet per second and gallons per minute ______________________________ 34
7 Flow over rectangular suppressed weirs in cubic feet
per second ___________________________________________________________________________ 38

8 Flow through rectangular submcrged orifice in cubic

feet per second ___________________________________________________________________ " 45

9 Discharge tables for the constant-head orifice turnout

(Capacity 20 c.f.s.) __ "__________________ "______________________ "______________ 47

10 Discharge tables for the constant-head orifice turnout

(Capacity 10 c.f.s.) ----"-"----""------""------------------"""""""""""" """""""." 48
11 Standard dimensions and capacities of the Parshall
measuring flume """" ___ "" _________ """"" __ "_" __ """""" ___ """"_"" ___ "" _______ ""_""""" 53
12 Free flow through Parshall measuring flumes __ """"""""""""""""""""""" __ " 58
13 Bills of material for 3-inch to I-foot wooden Parshall flumes_"""_ 65

-3-
 LIST OF FIGURES
Nllmher Title Page
1 Conversion diagram for finding equivalent rates of flow .......... 11
2 Time application diagram .................... . . .......................... 14
3 Stream cross-section divided for making current
meter measurement .................... . .............................. 15
4 A sample set of stream gauging notes prepared to illustrate
form of recording measurements ..... ............ . 16
.5 Angle iron crest in rectangubr weir .... ............................ 18
6 vVeir notch and bulkheael in weir pond 20
7 Hectangular weir with end contractions 21
8 Discharge curves for rectangular weirs
9 Trapezoidal or Cipolletti weir .................... 27
10 Discharge curves for Cipolletti weirs ............. 28
11 Ninety-degree triangular notch weir .. 32
12 Discharge curves for ninety-degree notch weir .. :3.'3
13 Discharge curves for suppressed rectangular weirs :37
14 Diagrammatic sketch showing flow through a
submerged orifice .... ...................................................... 42
15 Perspective of wooden Sll bmerged orifice structure ... 43
16 Discharge curves for submerged orifices having
fixed dimensions .......................... .. .. ....... 44
17 Constant head orifice 48
18 Calibratecl commercial gate installed in eanal bank .................. 50
19 Eight-foot Parshall measuring flume located in
the Logan Northern Canal Ilear Logan, Utah... 51
20 Plan and longitudinal section of Parshall measuring flume 52
21 Six-inch Parshall measuring flume installed near
Smithfield, Utah ................. .............. .. .... 54
22 Diagram for detennining the loss of head through the
Parshall measuring flume . .. .................... .... ......... 55

-4-
 LIST OF FIGURES (Continued)
Numher Title Page
23 Discharge curves for free How ill Parshall Hume..... .56
24 Discharge curves for free flow in Parshall Hull1e..... .57
2.5 Phms for three-inch Parshall flume ... ........... 64
26 Plans for six-inch Parshall flume 66
27 Plans for nine-inch Parshall flume 67
28 Plans for one-foot Parshall flume ..................... . 68
29 Forms for six-inch concrete Parshall Hume .... .............. 69-70
30 Typical divider llsed on streams carrying considerable
sand and gravel... .................. 71
31 Divider below h·apezoiclal weir . . ....... 72
32 (a) Dimensions necessary ill making a measurement of
the flow from vertical pipes ........ .
33 Discharge curves for How from vertical pipes ...................... . 74
34 Dimensions necessary ill making a mcasurement of
the flow from horizontal pipes ..... . .............. . ....... 76
3.5 Discharge curves .for flow from horizontal pipes. 77
36 Purdue method of measuring pipc How. 78
37 Flow from horizontal pipes hy Pm·cluc co-orclinate methocl .... 79-80

-.5-
 FOREWORD
Although irrigation has been practiced in Utah for more than one hundred
years, irrigation water still is being dish'ibutecl to farmers with little or no
thought about its measurement. A farmer would not think of buying or
selling other farm commodities, such as hay, grain, beef cattle, or dairy prod-
ucts, without weighing or accurately measuring them, but at the same time
he is often content to accept and pay for the irrigation water received with
little or no knowledge as to the actual amount received, or whether or not
he is receiving the amount he is entitled to.
Measurement of irrigation and drainage waters in Utah by irrigation
companies, irrigation and ch'ainage districts, and by cities and towns having
iITigation systems is of paramount importance to conservation of the state's
water and soil resources. Systematic water measurements properly recorded,
interpreted, and used constitute the foundations upon which increasing effi-
ciencies of water conveyance, application and use must be constructed. Higher
efficiencies in the various phases of irrigation will conserve water and decrease
the need for and the cost of land drainage,
The purpose of this bulletin is to present, in a brief and simple form, a
discussion of the more common methods of watcr measurement together with
descriptions of the devices used and useful tables or graphs.
Water measurement is based on fundamental principles of hydraulics,
but the practical application of these principles necessary to the actual meas-
urement of stream flow requires no special knowledge of hydraulics or mathe-
matics beyond simple algebra. The technique of using these devices and the
graphs or tables accompanying them can be mastered Teadily by farmers or
those responsible for regulation and distribution of water to the farmers,
It is hoped that this simplified presentation of information on water
measurement will encourage more irrigation companics and farmers to measure
their irrigation water and to strive to increase efficiencie~ in the use of existing
water supplies. This bulletin should be useful not only to irrigation farmers,
water masters and ditch riders, but also to county agricultural agents, agricul-
tural research workers, attorneys and engineers,

T- E. CUHlSTIANSEN, Director
Engineering Experiment Station

CAl'L FnrscHKNECHT, Director

Utah Cooperative Extension Service

-6-
 ACKNOWLEDGEMENTS
This bulletin is a rev:ision of Bulletin No. 2 of the Utah State Engineering
Experiment Station, and is a compilation of infol1l1ation gathered from pub-
lished sources, together with that gathered from the author's practical ex-
perience. The author is especially indebted to the Utah State Engineering
Experiment Station for material from Bulletin No. 2 by Wayne D. Criddle
and Eldon M. Stock; to the Utah State Agricultural Experiment Station for
material from Circular 77 by George D. Clyde; to the University of California
Agricultural Experiment Station for material from Bulletin No. 588 by J. E.
Christiansen; to the Colorado Experiment Station for material from Bulletins
423 and 426-a by Ralph L. Parshall; and to the U. S. Department of Interior,
Eureau of Reclamation, for information on constant head orifice turnouts.
The present bulletin incorporates most of the tables contained in Exten-
sion Bulletin No. 166, "Measurement of Irrigation IVater-A Handbook of
Discharge Tables for Ditch Riders and Irrigators" by James R. Earker, which
was prepared for use with Engineering Experiment Station Bulletin No.2.
The use of this material is acknowledged.
The Division of Irrigation, S. C. S., has, alone and in cooperation with
the various state experiment stations, gathered considerable information on
methods and devices used in measuring irrigation water. For the use of some
of this infomlation, the author is indeed grateful.
The author is especially grateful to Wendell M. Keck for editing the
manuscript, and to A. A. Bishop, C. H. Milligan, and James H. Earker for
rev:iewing the manuscript and for many helpful suggestions; and to Director
J. E. Christiansen, under whose direction the bulletin was written.

-7-
MEASUREMENT OF IRRIGATION WATER
by

Eldon M. Stock l

INTRODUCTION
vVater is the limiting factor in Utah's agricultural development. In spite
of the admitted value of water, the farmer knows less about its measurement
than about any of the other commodities he handles. He knows how to meas-
ure his land, weigh his crops and count his cattle, but he has little conception
of how to measure his most valuable assct, irrigation water. The importance
of water measurement is not appreciated until the water supply becomes
over-appropriated and users begin interfering with each other's rights. Ex-
pensive litigation, which nearly always follows controversies ovcr water, is
gradually convincing the farmer that water should be measured as carefully
as beets, grain, sugar, coal, flour or any other commodity he buys or sells.
The building of storage reservoirs for utilizing flood water and winter
How has brought into use new irrigation conditions that depend for their
success on the measurement of water. The storage reservoir may be considerecl
a bank in which the farmer depOSits, instead of gold, silver or currency, a
certain volume of water that he will use later for irrigation. He draws this
water from storage as he needs it, just as he draws his money from the bank.
To protect the various rights in the reservoir, the water must be measured
in and ont.
Even if grown on the same soil, different crops recluire different amounts
of water. Also, different soils require different amounts of water for the same
crop. To utilize water economically, the farmer must know how much water
to apply and how to measure the amount of each application.
The farmer is more and more recognizing the need for and value of
water measurement as is evidenced by the many inquiries that come to the
college for information concerning this subject. The demand for information
will increase as f8rmers become more conscious of the need for measuring
irrigation water in order to use it effieiently and also to defend their water
rights.
The purpose of this bulletin is to present in simple terms thc essential
elements of water measurement to irrigation farmers, c1itch riders, water masters
and others who wish to measure irrigation water. Frequent references are
mac1e to more technical publications; thus, anyone wishing to c10 so may

IProfessor of Civil Engineering.

-8-
determine the basis of the simplified principles of water measurement. Tabular
and graphical presentation of the solution of the various flow formulas is used
throughout this bulletin because these solutions are simple and have a wide
application.

TERMS USED IN WATER MEASUREMENT

Water is measured under two conditions-at rest and in motion.
Water at rest-that is, in reservoirs, ponds, soil and tanks-is measured
in units of volume such as the gallon, cubic foot, acre-foot and acre-inch.
Measurement of water in motion-that is, flowing in rivers, canals, pipe
lines, ditches and flumes-is expressed in rate of flow: gallons per minute
(g. p.m.) , cubic feet per second (c.f.s.), acre-feet per day, acre-inches per
hour, and miner's inches.
It is important that the distinction between a unit of volume and a unit
rate of flow be kept in mind. For instance, a cubic foot is a definite volume
of water such as would be held in a container 1 foot wide, 1 foot broad and
1 foot deep, whereas a cubic foot per second is a flow which would fill the
cubic-foot container once every second as long as the flow continued.
Acre-foot-An acre-foot is a volume of water sufficient to cover an acre
1 foot deep. It is equal to 43,560 cubic feet.
Acre-inch-An acre-inch is a volume sufficient to cover an acre 1 inch
deep. It is equal to one-twelfth of an acre-foot or 3630 cubic feet.
Cubic foot per second (c.f.s.) - This is a rate unit and represents an exact
and definite quantity of water per second. It is the equivalent of a stream
1 foot wide and 1 foot deep flowing at an average rate of 1 foot per second.
Gallon per minute (g.p.m.) - This is a rate unit and represents a definite
quantity of water per minute. It is the equivalent of a stream that would fill a
gallon measure once each minute.
Miner'sinch-Miner's inch is a rate of flow It is a variable unit having
different meanings in different states. (See Table 1.) The Utah miner's inch
is a quantity of water flowing freely through an opening 1 inch square, the
center of which is 4 inches below the surface of the water standing above
the opening. It is equivalent to a flow of 9 gallons per minute or one-fiftieth
of a cubic foot per second. The miner's inch is not a stream of water 1 inch
deep and one inch wide, regardless of the height of water swjace behind the
opening. The miner's inch is a convenient unit for measuring small streams,
but where the flow is 1 cubic foot per second or greater, the most common
unit is the cubic foot per second.
The cubic foot per second (c.f.s.) is generally accepted as the standard
unit of measurement expressing the rate of flow. Pump manufacturers have
always expressed their pump capacities in gallons per minute; therefore, this

-9-
unit is still used in discussing flow from wells or pumps. Several other units
are used to express the rate of flow, but they differ from those defined above
only in the time interval. For quick conversion from one unit to another,
without calculation, Table 1 and Figure 1 are included. The top scale on
Figure 1 is cubic feet per second. To change from cubic feet per second to
any other unit, follow the vertical line downward until it intersects the scale
of the unit desired. Thus, 5 c.f.s. equals: 2250 g.p.m., 300 cubic feet per
minute, 10 acre-feet per day, or 5 acre-inches per hour.

SOME CONVENIENT RELATIONS

Some convenient relations between the units of How are:
1. 1 cubic foot per second (c.f.s.) = 450 gallons per minute
(g.p.m.) (approximate)
1 cubic foot = 7.5 gallons (approximate)
60 seconds = 1 minute
7.5 x 60 = 450 gallons per minute (g. p.m.)

2. 1 cubic foot per second = 1 acre-inch per hour (approximate)

3600 seconds = 1 hour
1 c.f.s. = 3600 cubic feet per hour
1 acre-foot = 43,560 cubic feet
1 acre-inch = 1/12 x 43,560 = 3630 cubic feet
Since 3600 = 3630 (approximately)
Therefore, 1 c.f.s. = 1 acre-inch per hour (approximate)

TABLE 1
Conversion Table of Flow Units

Miner's Inchcs
Idaho Acre Acre
Cubic Gallons 1'-linion Arizona Kansas
feet Calif. Nebraska inches feet
per gallons per per day
per minute per clay "fontana New Ivlex. Colorado
second hour (24 Hrs.)
Nevada No. Dak.
Oregon So. Dak.
I Utah
(usc 450) I
1
0.00223
448.8
1
0.646
0.001440
40
0.0891
50
0.1114
38.4
0.0856
0.992
0.0022 11.983
0.00442
1.547 694.4 1 61.89 77.36 59.44 1.535 3.07
0.025 11.25 0.0162 1 1.25 0.960 0.0248 . 0.0496
0.020 9.00 0.0129 0.89 1 0.768 0.0198 0.0397
0.026 11.69 0.0168 1.042 1.302 1 0.0258 0.0516
1.01 452.42 0.651 40.32 50.40 38.71 1 2.00
.504 226.3 0.3258 20.17 25.21 I 19.36 0.5 I
1. Example: From Table 1. Utah miner's inch equals 0.02 cubic feet per second,
equals 9.00 gallons per minute, equals 0.0198 acre inches per hour, and equals
0.0397 acre feet per day (24 hours).

-10-
 CONVERSION DlACRAM

1 2 3 4- 5 6 7 8 1
S.cond teet------------- .JJ

Callon. per ~ay---------

Gallons per hour--------

00
Gallons per minuie------

Cubic teet per day------ 1m~,JIrmltln>f~ .11IIITm~M:11lrll~ilt~ll:

,.~ Il III:~fJ.J
11111T ! kU.l,l,U'I' j U,ld
·riM IiItI ,r.r:J1hu. m.~·I~
I l
f-'
f-'
C~ic feet per ho~r----- I! i I,
I
'11I11,lllr{;[i!blllLill I~ [IIJTl
i 15' b~ , '1'll"~9Id1ifTTI
,I
hh~ ·IJ I'I'.ir~lt711
!Lilllli ~'I ~ j:iJ1IIId51~~i
.!rami:
I

Cubic feet pBr minuie---

Acre-feet per day-------

mm~~mm~~~~~~~~~~~ru
Acre-teet per hour------ '
Acre-inches per d~----- II
Ac:r&-lncites per hour---- III!.1 IIlll I! I i~'III i I~
ul U .~.I, "d,!,I,!.iL"I,1 ,,.I, ,Ii,
11 j. ~ I: 111111' :

Miners Inches---------- '1111 fI i 1111 Hi11111 Iri~ 111111·Prfj I ffl ~

(or 1-50 second-foot)

Fig, 1. Conversion diagram for finding equivalent rates of flow.

 3. 1 cubic foot per second = 2 acre-feet in 24 hours (approximate)
1 c.f.s. = 3600 cubic feet per hour
24 x 3600 = 86,400 cubic feet per 24-hour day
1 acre-foot = 43,560 cubic feet; 86,400 -;- 43,560 = 1.9834
Therefore, 1 c.f.s. = 2 acre feet in 24 hours (approximate)

The following approximate formulas are useful to compute the depth of

water to be applied to an area of ground:

1. cubic feet per second (c.f.s.) X time (hours) = acre inches per acre
Area (acres) or average depth
in inches.

2. Gallons per minute (g.p.m.) X time (hours) = acre inches per acre
450 X Area (acres) or average depth
in inches.

3. Miner's inches (Utah) X time (hours) acre inches per acre

50 X Area (acres) or average depth
in inches.

4. Miner's inches (Calif. statute) X time (hours) = acre inches per acre
40 X Area (acres) or average depth
in inches.

Examples In the Use of Convenient Relations

Examples of how to use the relations given (See Figure 1) are:

1. Jones has a pump which discharges 450 g.p.m. If he spends 60 hours

in irrigating a 10-acre orchard, what average depth in inches does
he apply? (Note that the size of the stream, the length of time it is
to be applied, and the area are given.)
450 g.p.m. = 1 c.f.s.
1 c.f.s. for 1 hour = 1 acre-inch
1 c.f.s. for 60 hours = 60 acre-inches
Therefore 60 acre-inches are spread uniformly over 10 acres.

The average depth is 6 inches. (answer)

Applying general formula 2, g.p.m. X time (in hI'S.) Depth in inches

450 X Area (acres)
450 X 60
6 inches' depth of application (answer).
450 X 10

-12-
Or to solve the same problem graphically by using Figure 2: from table of
equivalents, Table 1, 450 g.p.m. = 1 c.f.s. Enter diagram base line time in
days at 2~ days (60 hours) following line vertically up to intersection of
diagonal line labelled 1.0 c.f.s.; move horizontally _to right to intersection of
vertical line through area (10 acres); read depth of application from inter-
cepted diagonal line (6 inches).

2. How long will it take to apply a 6-inch irrigation to a 15-acre tract

if the size of the irrigation stream is 3 c.f.s?
15 X 6 = 90 acre-inches to be applied.
3 c.f.s = 3 acre-inches per hour
90/3 = 30 hours (answer)
3. How much land will a continuous flow of 15 c.f.s. cover in 4 months
if each acre must have an average depth of 3 feet?
1 c.f.s. = 2 acre-feet per day
15 c.f.s. = 30 acre-feet per day
120 X 30 = 3600 acre-feet
Each acre requires 3 acre-feet. Total area = 3600 = 1200 acres. (answer)
3
4. A flow of 5 c.f.s. is equal to how many acre-inches per day? (See
Figure 1.) Look vertically under 5 c.f.s.· and read on the scale of
acre-inches per day 120 acre-inches. (answer)
Sample problem drawn on Figure 2:
Example: Given: Irrigation stream (Q) = 1 c.f.s.
Turn, Time in days (T) = 1 day (24 hr5.)
Area to be irrigated in acres (A) = 4 Ac.

Required: Depth of application in inches = 6 inche~

Solution, follow dotted line

METHODS OF WATER MEASUREMENT

Several devices are commonly used for measuring irrigation water. Those
devices most commonly used in Utah and other parts of the West by engineers,
farmers and ditch riders are: weirs, orifices, Parshall flumes, calibrated gates
and rating flumes. In addition to the foregoing devices, current meters,
Clausen-Pierce Weir gauges, and "Slope area" methods are used by engineers
and others who are technically trained. Various mechanical devices for meas-
uring flow have been designed, some of which not only measure rate of flow
but also register the total volume of water passing during any period of time.

-13-
~ ~\ / 7 2J_
I

\ \ 9 /

\)~ 1\ \~~ / ~_
I~ \. ~~~~~ 7~~C L
~ ~i ~ ~ '% \~"~
/

1,\ \\I~ ~..

j 7 // v6"

I" . ~. '- ; 7 / /'

' /
o •

~ ~ \ \1\' ~ /Y.L/7 v ~
~ 0..,
.
I~ \1\\\; ~~V' ::--:-- ___
~I\\\ ~/v:.~~~
h

/7 )'

~!~~~---
2

:
;; 4 3 2 1 0 1 2 3 4 :5 6 7 8 9 10
Time in Days (T) Area in Acres (A)
Figure 2. TIME APPLICATION DIAGRAM
 CURRENT METERS
The discharge of a stream can be determined directly by measuring the
velocity and the cross-sectional area of the water. The most reliable method
of determining the velocity of the water is by the use of a current meter, of
which several types are available.
Most current meters consist of a wheel fitted with cupped vanes; it is
mounted on an axis about which it is free to turn under the action of the
stream. This wheel is on the upsh-eam end of a horizontal shaft that has its
other end fitted with directional vanes that steady the meter and keep it
headed into the current. The meter may be used in shallow water where
wading is possible by being supported by a vcrtical rod held in the hands
of the observer. In deeper water the rod is removed and a cable attached to
the meter which is suspended from a boat or bridge. To the lower side of
the meter is attached a streamlined lead weight which steadies the meter
and holds it in position. The wheel revolves at a rate proportional to the
velocity of the current in which it is placed. With the meter immersed the
revolutions of the wheel are counted by means of an electric circuit which is
broken at each revolution by means of a commutator attached to the wheel
shaft. The wires of the circuit pass from the meter to the surface where a
small buzzer or earphone records the "make" and "break" of the circuit. Cur-
rent is furnished by a small dry cell battery.
The discharge of a stream is the product of its cross-sectional area and
the mean velocity of the water passing a given section. A meter measurement
consists of detcrmining with all possible accuracy the value of these two
factors. The area for any stage of Row may be easily determined by soundings
made across the selected section, the distance of each point of sounding
being measured from a permanent point on the bank and in the line of the
cross-section. Best results are ohtained from gaugings if the area is sub-
divided into a series of vertical strips, preferably of equal width, and the
discharge Q past the entire section is computed on the basis that the symbols
aI' a 2, <la, etc. being the areas of the respective strips; and VI' V2, V3, etc.
the mean velocity for each strip; then, the
Total Q = a 1 VI -+ a2 V2 + aa v:~ + a4 V4 + etc. (See Figure 3.)

Where dept.h of wat.er

exceec1,5 1.5 I make meter meas.
'Urement.5 at 2/10 &nd 8/10 ot'
CtJi!l!OO KETIJ! depth. Irrnel'" les.5 than 1.5'
GAUGING Sf ATION in depth, take one mea.5ur-ement
Qr 6/10 ot depth from water
,urface a3 ,hOWTl.

Fig. 3. Stream cross-section divided for making current meter measurement.

-15-
 UNITED STATES
9-275 DEPARTMENT OF THE INTERIOR NaMe R 9. (!" ..
September 1~3 GEOLOGICAL SURVEY Ght. I 5'.< (<!I t?:~
WATER RESOURCES BRANCH Ght.,I !lip (~10:1>'o' 4 ~
Mn. Ght. I. ~ -i""&'"
Date , /" II C I/} • lo.£i DISCHARGE MEASUREMENT NOm,.,ve. below _ _ __

lied lie,.. ~,~1;!at [j/toc;teY' n Meter

.tt
' Di
st. "• '"~ Rev-
't" i VELOCITY
lc
rl
from D p 1
lponit~tl e th.2 -go t70':;s
T me
in
1---..,---,,------;,.----1
f;;~~~- ~~n
Area Mean
depth Width Diacharge .'z
r 0:;:;
osendc-
s At
point tical scction
.tt
/) o o o

.M
8·9'
'"
.tT
.tIl
.P.:;)/

ID.5 «'1 ~ 111' _60_1+-0_,,,_3-+--°--=,"_B-+·- - + - - - + - - 1 - - - - 1 - - - - .14

_-+-_--+-_:1 r !'}.57 I . .!>- 0.15 I.£) ().gil _9%
11.5 II> ~.~ /1 /,:; ~ .51 v.51

o o
.8Ii

---r--r-r--r-~-1---~--rlI --~--4_~~---
I
I ! .&0

I 15.1'1
No, _ _ _ 01 _ _ _ Sheet!!. Camp. hy __ _ Chk.by
u. S. GOVERNMENT PRINTING O"ltE 16-2007~
.75

Fig. 4. A sample set of stream gauging notes prepared to illustrate

form of recording measurements.
 A typical set of discharge notes and computations of discharge is shown
in Figure 4.
To obtain the value of v it is commonly assumed that the sum of the
mean velocities in the vertical, at each end of the strip, divided by 2 may be
taken as the mean velocity for the entire strip. Various methods are used
for obtaining the mean velocity in the vertical but the most common methods
used for relatively small streams are the two-tenths and eight-tenths method
and the six-tenths method.
The two-tenths and eight-tenths method consists of detelmining the
velocities at 2/10 and 8/10 the depth and assuming that the mean velocity
in the vertical is equal to their arithmetical mean.
The six-tenths method consists of making one measurement in each
vertical at 6/10 the depth measured from surface down and assuming the
velocity as found at that point to be the true mean.

FLOAT MEASUREMENTS
For a rough estimate of the water flowing in a straight uniform channel,
some object such as a piece of wood or an apple may be thrown into the
stream and the time required by the object to go a known distance down-
stream noted. The average cross-sectional area of the water in this length in
square feet multiplied by the surface velocity in feet per second, as detelmined
by timing the float, gives a figure which, if multiplied by a coefficient to
correct for the fact that the surface velocity of the water is greater than the
average velocity, will give the approximate discharge for the stream. Al-
though it varies widely, depending upon the shape of the cross-section and
the condition of the banks and bottom of the channel, the average coefficient
is about 0.85. The discharge therefore equals approximately 85 per cent of
the product of the cross-sectional area times the surface velocity.
The float method of measuring the flow is not recommended except in
rare cases where other more reliable means are not available.

WEIRS
When conditions are favorable the weir is one of the simplest, cheapest,
and most reliable devices for measuring the flow of water.
Terms U sed- The following terms are used in connection with weirs:
Weir-A bulkhead placed across a ditch or stream with an opening cut
in the top through which the water is allowed to pass. The opening is called
the weir notch.

-17-
 Weir Pona- The portion of the ditch immediately upstream from the weir.
WeiT Crest-The bottom of the weir notch.
Head-on-Cl'est- The depth of water flowing over the weir crest measured
at some point in the weir pond.
Sharp-crested-Weir-A weir having thin-edged crest and sides such that
the overflowing water touches the crest at only one point.
End Contraction-The horizontal distance from the end of the weir crest
to the side of weir ponel.
Bottom Contraction-The vertical distance from the weir crest to the
bottom of the weir pond.
Weir Scale 01' Gauge-The scale fastened on side of weir or on stake in
weir pond to measure head-an-crest.
Weirs may be divided into two general classes; (1) sharp-crested and
(2) broad-crested. The sharp-crested may again be divided into weirs with
end contractions and weirs without end conh'actions, Only the sharp-crested-
weir is discussed in this bulletin.
Weirs may be built as stationary structures or they may be made portable.
The portable weirs are usually made of wood or sheet steel and are placed
in the ditch where a measurement is desired. The stationary sh1.lctures may
be built of wood, steel, or concrete. In the wood and concrete structures the
notch is usually faced with a metal strip which constitutes the sharp crest.
Figure 5 shows the use of angle
iron for the crest of a concrete
CROSS SECTION 'f. 15 weir.
\.. to. The discharge through a
1tJOIN~~ weir notch is proportional to the
<,GI ~ head on the crest and is affected
\..O'~ -
by the condition of the crest,
the conh'action, the velocity of
approach, and the elevation of
the water surface down stream
from the weir. Each type of
weir has its own discharge for-
PICTORIAL VI r.w
mula, tables or curves, There-
Fig. 5. Angle iron crest in rectangular weir. fore, in order to properly meas-
ure water with a weir, it should
be constructed and installed in a manner similar to that for which the formula,
tables and curves were developed. The following are some general require-
ments for the proper setting and operation of weirs;

-18-
(1) The weir should be set at the lower end of a pool sufficiently long,
wide and deep to give an even, smooth current with a velocity of
approach of not over 0.5 ft. per second, which means practically
still water.

(2) The Longitudinal Axis of the weir should be perpendicular to the

direction of the flow. If a weir box is used, the centerline of the
weir box should be parallel with the direction of flow.

(3) The face of the weir should be vertical, leaning neither upstream
nor downstream and at right angles to the direction of flow.

(4) The crest of the weir should be horizontal so that the water passing
over it will be the same depth at all points along the crest and sharp-
crested so that the overfalling water touches the crest at only one
point.

(5) The distance of the crest above the bottom of the pool should be
about three times the depth of water flowing over the weir crest.
The sides of the pool should be at a distance from the sides of the
crest not less than twice the depth of the water passing over the crest.

(6) The gauge or weir scale may be placed on a stake at any pOint in
the weir pond or box provided it is sufficiently above or to one side
of the weir to be free from the downward curve of the water surface
as it passes over the weir crest (Figure 6); or the weir scale may be
placed on the upsh·eam face of the weir structure and far enough
to one side so that it will be in comparatively still water, as shown
in Figure 7. The zero of the weir scale or gauge must be placed
at the same elevation as the weir crest. This may be done with an
ordinary carpenter's level or, where greater refinement is desired,
with an engineer's level.

(7) The measurement of the head or depth of water on the crest may
also be made by placing a carpenter's rule or scale on a lug to the
side of the weir notch or on a stake placed in the weir pond 4 or 5
feet above the weir. The lug or stake must be placed level with the
weir crest.
(8) The crest should be placed high enough so that the water will fall
freely below the weir, leaving an air space under the overfalling
sheet of water. If the water below the weir rises above the crest
elevation, free fall is not possible and the weir is then said to be
submerged. Unless complicated corrections are made, measurements
on submerged weirs are unreliable.

-19-
 (g) For more reliable measurements the depth of water flowing over the
a.·est should be no more than one-third the length of the crest.
(10) The depth of water over the crest should not be less than 2 inches.
With smaller depths the over-falling sheet of water tends to cling
to the downstream side of the crest and the relationship between
the depth of water on the crest and the discharge no longer holds h·ue.
(11) To prevent erosion below the weir, the ditch downstream should
be protected by loose rock or by other material.
Limitations in Use of Weirs-Although weirs are easy to construct and
convenient to use, they are not suitable for measuring water under all condi-
tions. One of the major disadvantages in the use of weirs is that they require
a considerable loss of head which may not be available on ditches with a
flat grade. Also, reducing the velocity of the water in the weir pond causes
deposition of silt from those streams carrying a heavy silt load and these
deposits in the channel of approach destroy the proper conditions for weir
measurements. Weirs should not be combined with head gate shuctures.
\Veil' Structure-The weir structure may be either portable or stationary.
Because of having less bulk, metal weirs are more satisfactory than wooden
weirs for portable use. A very substantial metal weir can be made of )~ inch
(12 gauge) galvanized iron stiffened by means of heavy angles welded
together and riveted to the downstream side of the plate. It can then be

Fig. 6. Weir notch and bulkhead in weir pond.

-20-
driven into position in a flowing sh'eam with a heavy wooden block or mallet
without shutting the water out of the ditch.
For stationary purposes the type of soil will largely determine whether
a simple weir bulkhead and weir pond may be used or a weir box should be
built. In the heavy clay soils, where little washing occurs, a simple bulkhead
can be used to an advantage, but in light soils, subject to erosion, a weir box
with wing walls and cut off walls should be used to prevent the ~tructure
from being washed out.
Figure 6 is a drawing of a simple weir bulkhead which can be con-
structed easily on the farm. With this type of weir the head is usually meas-
ured from a stake in the weir pond set at the same elevation a~ the crest.

Don'ts in Regard to Weirs-For further emphasis on proper use of weirs,

the following "don'ts" are included:

1. Don't set weir immediately below a curve in the ditch a~ the curve
will cause the water to flow to the side of the crest.

2. Don't set it immediately below or too close to a headgate, where the

water has a high velocity, as too high a velocity of approach will result.
3. Don't allow the water below the weir to back up to the elevation of
the crest as it will not allow complete contraction and it will cut
down the discharge.

4. Don't set the weir any other way than vertical (plumb) and at right
angles to the flow of the stream.

WAT!l! SUR1 ACE

JII
SCALE OR
GAUGE

11ID
CONTRACTJ:OII
OOTTOK
CONTRACT!OII

Fig. 7. Rectangular weir with end contractions.

-21-
 5. Don't attempt to use too small a weir. Put in a larger weir where
the water to be measured exceeds a depth on the crest of one-third
the crest length.
6. Don't allow the pool above the weir to fill up with sediment as the
the resulting decrease in the cross-section will increase the velocity
of approach.
Making a Discharge Measurement With a Weir-When the weir is prop-
erly installed and the flow through the notch has become steady, measuring
the depth of water over the crest of the weir is made by placing a carpenter's
rule on the stake or lug which has been fixed at the elevation of the crest or
by reading the weir scale. With the head determined, consult the proper
discharge curve or table for the weir being used. The curves are so con-
sh'ucted that the head may be measured either in feet or in inches and with
the crest lengths varying from 6 inches to 4 feet. For example, suppose that
the head on the crest of a 2-foot rectangular weir measured 8.5 inches. From
Figure 8, it is seen by following horizontally across the line for a head of 0.7
feet to where it intersects the curve for the 2-foot weir and dropping vertically
down that the discharge is 3.7 c.f.s.
To solve the same example using Table 3, enter table with value of head
0.70 feet in left column, "Head, in feet," follow line horizontally to the right
and read result under column "Crest length 2.0 feet," 3.71 c.f.s.
Rectangular Weir-The rectangular weir, Figure 7, is named from the
shape of its notch. It is the oldest form of weir used. Its simplicity, easy
construction and accuracy, when properly installed and used, make it still
the most popular weir. Table 2 gives the recommended size of rectangular
weirs to use with various size streams of water. The maximum and minimum
discharge for the various sizes of weirs overlap considerably or indicate that
a weir having a crest length of 3 feet measures a 9-second foot sh'eam with
the same accuracy as a 4-foot weir.
By using Figure 8 (p. 23), the discharge for weirs having crest lengths
from 6 inches to 4 feet can be detennined quickly. To clarify the relationship
between head and discharge, and for those who prefer tables in determining
discharge, Table 3 is included (pp. 24-26). This table can verify the results
obtained from curves and shows the discharge for weir crests of 1.0, 1.5, 2.0,
3.0, and 4.0 feet for heads from 0.1 feet to 1.5 feet.

TABLE 2-Recommended sizes of rectangular weirs.

Flow Maximum Head Crest length
e. f. s. Feet Feet
0.30 to 2.00 0.75 1.0
2.00 to 2.00 0.75 1.5
2.50 to 6.00 1.00 2.0
5.00 to 13.00 1.25 3.0
8.00 to 20.00 1.40 4.0

-22-
 FIG. 8

--~lll J7l
19

I
't'
"_DISCHARGE CURVESl - -I
--i 1 I
VI'

itt1
FOR
1·4
17
--RECTANGULAR WEIRS - /" ..L..J
"rI 1·3
I.
t.. -+-r--L. . V 1-I

t" ~---t I ~ ±!- :-=--1-~;f-Iv yY

qq' f----.

__ _
CREST LENGTHS 6 IN.- 4 FT.
Q =3.33_ l L- O H ) Hh i I
L . .

: I I
?" 1·2
14

Q U ,3
I 7
'"
t")
:r'

~
10 12
~
Ii :/
I' -kJl~
C/Q iI ! i:
!! ,~I
1
<!> 1-/1 I / i) . /' I I I
p-i/ i /1 / l Vi '
t") 0.9
e'1
fO ~f-~~-~;~i' 1/ i:/'~./' ~$1J
,----r-"

+TIT4~-
L~ <:
0~ <!> 0·8 9
'"...,
I 0
'1

~
I- 0.7

~
W r "A-0'
,--".:...I-"
, - 2n-.0
\--
jl
/
r./
~. I jS
./
('-(0~I"
<'.
j< \/ ~
I'
I
'" I I
'"
I /
/ -
I

"'~~~
-- o~
1--r::::~si
(,<?-~
I
i J-r
-+--+-
Rffi
I ----

rgr-tJJ~~'ol -(,,~ -?~(,/ _I.--;;~I'I' ~

t")

S- 0·6 7
t;1'-tr-;: !r~"
I ,.",'" ",...;1' I'€.<?- 1 I ~ 1
O 0 !=j (;J '" Q:;~ -( '"~ '" '" G€. .-r I .
~ < I L-L_ I I I I
~I "-/I_~fJ(j ~I'r ~~~O\f vr
I I
~ 0·5 6
S' I '" I T T -I 1-
~(,I'~€.~G~
'1 0' ,
::;
7/!I"- ','"
/./' Y!: I I :I."d}"'L
/ 1/L_L LlJ 1 I I I 1 I

HI
0·4
<!>
~. 0' !,;12. ~~~-f--(I-r- EXAMPLES 10 FIND' DISCHARGE: HEAD=0.7'1_ -
,,~ .,' ~
1
4
FOLLOW BR:)K£N LINE I-ORIZONTALLY TO
I / 111 / / i I I 01 v-l ._ I I NTERSECTION OF CURVE FOR 2' CREST e- f-
3
'/ II Y/ I,... --I-- --'--1--- THEN DR:)P VERTICALLY AND READ I---f--
2
Yffi
V I
I . I

I
1

IF
VV
' / I /V
/ I

I
DISCHARGE OF 3.64
LIKEWISE
1.0' CREST
FOR A
DISCHARGE
HEAD
C. F.S.
OF 0'.3' ON
0.51 C.F.S.
I--f-
1---
1---

I I {I' ().5 I ~3TL I 1 t I 1J J 2.5 r I 3

2 3 4 5 6 8 10 12 13 14 13 16 17 IS 19
DISCHARGE IN C.F·S.
 TABLE 3
Flow Over Rectangular Contracted Weirs in Cubic Feet Per Second*
Crest length I For each addi-
tional foot of
Head, crest in excess
Head, in feet in inches
(approx.)
1.0 foot 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet of 4 ft.
(approx.)
Flow in cubic feet per second

0.10 13/16 0.105 0.158 0.212 0.319 0.427 0.108

0.11 15/16 0.121 0.182 0.244 0.367 0.491 0.124
0.12 17/16 0.137 0.207 0.277 0.418 0.559 0.141
0.13 19/16 0.155 0.233 0.312 0.470 0.629 0.159
0.14 1 11/16 0.172 0.260 0.348 0.524 0.701 0.177
0.15 1 13/16 0.191 0.288 0.385 0.581 0.776 0.196
0.16 1 15/16 0.210 0.316 0.423 0.638 0.854 0.216
0.17 21/16 0.229 0.346 0.463 0.698 0.934 0.236
0.18 23/16 0.249 0.376 0.504 0.760 1.02 0.257
0.19 21f4 0.270 0.407 0.546 0.823 1.10 0.278
I
0.20 2% 0.291 0.439 0.588 0.887 1.19 0.303
0.21 2lh 0.312 0.472 0.632 0.954 1.28 0.326
0.22 2% 0.335 0.505 0.677 1.02 1.37 0.35
0.23 2% 0.358 0.539 0.723 1.09 1.46 0.37
0.24 2% 0.380 0.574 0.769 1.16 1.55 0.39
0.25 3 0.404 0. 609 1
0.817 1.23 1.65 0.42
0.26 3% 0.428 0.646 0.865 1.31 1.75 0.44
0.27 3% 0.452 0.682 0.914 1.38 1.85 0.47
0.28 3% 0.477 0.720 0.965 1.46 1.95 0.49
0.29 31f2 0.502 0.758 1.02 1.53 2.05 0.52
0.30 3% 0.527 0.796 1.07 1.61 2.16 0.55
0.31 3% 0.553 0.836 1.12 1.69 2.26 0.57
0.32 3 13/16 0.580 0.876 1.18 1.77 2.37 0.60
0.33 3 15/16 0.606 0.916 1.23 1.86 2.48 0.62
0.34 41/16 0.634 0.957 1.28 1.94 2.60 0.66
0.35 43/16 0.661 0.999 1.34 2.02 2.71 0.69
0.36 45/16 0.688 1.04 1.40 2.11 2.82 0.71
0.37 47/16 0.717 1.08 1.45 2.20 2.94 0.74
0.38 49/16 0.745 1.13 1.51 2.28 3.06 0.78
0.39 411/16 0.774 1.17 1.57 2.37 3.18 0.81
0.40 413/16 0.804 1.21 1.63 2.46 3.30 0.84
0.41 4 15/16 0.833 1.26 1.69 2.55 3.42 0.87
0.42 51/16 0.863 1.30 1.75 2.65 3.54 0.89
0.43 53/16 0.893 1.35 1.81 2.74 3.67 0.93
0.44 51f4 0.924 1.40 1.88 2.83 3.80 0.97
0.45 5% 0.955 1.44 1.94 2.93 3.93 1.00
0.46 5lh 0.986 1.49 2.00 3.03 4.05 1.02
0.47 5% 1.02 1.54 2.07 3.12 4.18 1.06
0.48 5% 1.05 1.59 2.13 3.22 4.32 1.10
0.49 5% 1.08 1.64 2.20 3.32 4.45 1.13
0.50 6 1.11 1.68 2.26 3.42 4.58 1.16
0.51 6% 1.15 1.73 2.33 3.52 4.72 1.20
0.52 6% 1.18 1.78 2.40 3.62 4.86 1.24
0.53 6% 1.21 1.84 2.46 3.73 4.99 1.26
0.54 6lh 1.25 1.89 2.53 3.83 5.13 1.30

·Computed from Cone's formula: Q = .:1.247 L HUt- _ 0.5661...'''''' Hl.u

1 + 2 L"
-24-
 TABLE 3-(Conti n ued)
Crest length I For each addi-
tional foot of
Head, crest in excess
Head, in feet in inches 1.0 foot 1.5 feet 2.0 feet 3.0 feet 4.0 feet of 4 ft.
(approx.) I I I (approx.)
Flow in cubic feet per second

0.55 6% 1.28 1.94 2.60 .3.94 .5.27 l..3.3

0.56 6% l..31 1.99 2.67 4.04 5.42 l..38
0.57 6 1.3/16 1..35 2.04 2.74 4.15 5.56 1.41
5_58 6 15/16 l..38 2.09 2.81 4.26 5.70 1.44
0.59 71/16 1.42 2.15 2.88 4 ..36 5.85 1.49
0.60 7.3/16 1.45 2.20 2.96 4.47 6.00 1.5.3
0.61 75/16 1.49 2.2.5 .3.03 4.59 6.14 1.55
0.62 77/16 1.52 2.31 3.10 4.69 6.29 1.60
0.63 79/16 1.56 2.36 3.17 4.81 6.44 1.63
0.64 711/16 1.60 2.42 3.25 4.92 6.59 1.67
0.65 713/16 1.63 2.47 3 ..32 5.03 6.75 1.72
0.66 7 105/16 1.67 2.053 3.40 5_15 6.90 1.705
0.67 81/16 1.71 2 ..59 3.47 .5.26 7.0.5 1.79
0.68 83/16 1.74 2.64 3.,56 05.38 7.21 1.83
0.69 8% 1.78 2.70 3.63 05.49 7.36 1.87
0.70 8% 1.82 2.76 3.71 5.61 7.052 1.91
0.71 81/2 1.86 2.81 .3.78 05.73 7.68 1.95
0.72 8~s 1.90 2.87 3.86 5.85 7.84 1.99
0.73 8% 1.93 2.93 3.94 .5.97 8.00 2.03
0.74 81f8 1.97 2.99 4.02 6.09 8.17 2.08
0.75 9 2.01 3.05 4.10 6.21 8 ..33 2.12
0.76 9 '/8 2.0.5 3.11 4.18 6.3:3 8.49 2.16
0.77 9% 2.09 3.17 4.26 6.405 8.66 2.21
0.78 9% 2.13 3.2.3 4.34 6.58 8.82 2.24
0.79 9'12 2.17 3.29 4.42 6.70 8.99 2.29
0.80 9% 2.21 .3.305 4 ..51 6.8.3 9.16 2.3.3
0.81 9% 2.25 3.41 4.059 6.9.5 9.33 2.38
0.82 9 13/16 2.29 3.47 4.67 7.08 9.50 2.42
0.83 915/16 2.33 3 ..54 4.7.'5 7.21 9.67 2.46
0.84 10 1/16 2 ..37 3.60 4.84 7.33 9.84 2.51
0.8.5 103/16 2.41 3.66 4.92 7.46 10.01 2.55
0.86 105/16 2.46 3.72 .5.01 7 ..59 10.19 2.60
0.87 107/16 2.50 3.79 5.10 7.72 10.36 2.64
0.88 109/16 2.54 3.805 5.18 7.8,5 10 ..54 2.69
0.89 1011/16 2.,58 3.92 5.27 7.99 10.71 2.72
0.90 10 1.3/16 2.62 3.98 5.305 8.12 10.89 2.77
0.91 10 15/16 2.67 4.005 .5.44 8.25 11.07 2.82
0.92 11 1/16 2.71 4.11 .5.53 8 ..38 11.2.5 2.87
0.9.3 11 3/16 2.75 4.18 5.62 8 ..52 11.43 2.91
0.94 11'14 2.79 4.24 5.71 8.6,5 11.61 2.96
0.95 11'/s 2.84 4.31 05.80 8.79 11.79 3.00
0.96 11'12 2.88 4.37 5.89 8.9.3 11.98 3.0.5
0.97 11% 2.93 4.44 .5.98 9.06 12.16 3.10
0.98 11% 2.97 4 ..51 6.07 9.20 12.34 3.14
0.99 1F/s 3.01 4 ..57 6.15 9.34 12.53 3.19
1.00 12 3.06 4.64 6.205 9.48 12.72 3.24
1.01 12'/s 4.71 6 ..34 9.62 12.91 .3.29
1.02 12% 4.78 6.4.3 9.76 13.10 3.34
1.03 12% 4.8.5 6 ..52 9.90 13.28 3.38
1.04 12'1z 4.92 6.62 10.04 13.47 3.43
 TABLE 3-(Continued)
Crest length ~?~n~~cfo;t ai-
Head, i====r=====;====r====;====i crest in excess
Head, In feet in inches 1.0 foot I 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet of 4 ft.
(approx.)
(approx.)
Flow in cubic feet per second

I
1.05 12% 4_98 6_71 18 13.66 3.48
1.06 12% 5.05 6.80 10.
10.32 1
13.85 3.53
1.07 12 13/16 5.12 6.90 10.46 14.04 3.58
1.08
1.09
12 15/16
131/16
5.20
5.26
6.99
7.09
10.61
10.75
I 14.24
14.43
3.63
3.68
1.10 133/16 5.34 7.19 10.90 14.64 3.74
1.11 135/16 5.41 7.28 11.04 14.83 3.79
1.12 137/16 5.48 7.38 11.19 15.03 3.84
1.13 139/16 .----- 5.55 7.47 11.34 15.22 3.88
1.14 1311/16 ------ 5.62 7.57 11.48 15.42 3.94
I
1.15 1313/16 .. ---- 5.69 7.66 11.64 15.62 3.98
1.16 1315/16 _.---- 5.77 7.76 11.79 15.82 4.03
1.17 14 1/16 ... _.- 5.84 7.86 11.94 16.02 4.08
1.18 143/16 _.... - 5.91 7.96 12.09 16.23 4.14
1.19 14% ------ 5.98 8.06 12.24 16.43 4.19
1.20 14% ------ 6.06 8.16 12.39 16.63 4.24
1.21 Wh ------ 6.13 8.26 12.54 16.83 4.29
1.22 14% ------ 6.20 8.35 12.69 17.03 4.34
1.23 14% ------ 6.28 8.46 12.85 17.25 4.40
1.24 I 14% ------ 6.35 8.56 12.99 17.45 4.46
1.25 15 .----. 6.43 8.66 13.14 17.65 4.51
1.26 15¥s .. --.- ------ ------ 13.30 17.87 4.57
1.27 15¥4 .----- ------ ----.- 13.45 18.07 4.62
1.28 15% ------ --_.-. ------ 13.61 18.28 4.67
1.29 15lh ------ ------ ------ 13.77 18.50 4.73
1.30 15% ------ ------ .----- 13.93 18.71 4.78
1.31 15% ------ ------ ------ 14.09 18.92 4.82
1.32 1513/16 ... _-- ._.--. ------ 14.24 19.12 4.88
1.33 1515/16 ------ _.---- ------ 14.40 19.34 4.94
1.34 161/16 ------ ------ ------ 14.56 19.55 4.99
I
1.35 163/16 _.---- ------ ------ 14.72 I 19.77 5.05
1.36 165/16 ------ ------ ------ 14.88 19.98 5.10
1.37 167/16 .-.--. ------ ------ 15.04 20.20 5.16
1.38 169/16 ------ ------ ._---- 15.20 20.42 5.22
1.39 1611/16 ------
____ e.
---"-- 15.36 20.64 5.28
1.40 1613/16 ------ ------ .----. 15.53 20.86 5.33
1.41 1615/16 ------
____ e.
.----- 15.69 21.08 5.39
1.42 171/16 ------ .----- ------ 15.85 21.29 5.44
1.43 173/16 . ----- ------ ____ e •
16.02 21.52 5.50
1.44 17¥4 ------ ------ ------ 16.19 21.74 5.55
1.45 17% ____ e. 16.34 21.96 5.62
1.46
1.47
17%
17%
I ------
._----
\ ------
.-----
------
-.----
------
------
16.51
16.68
22.18
22.41
5.67
5.73
1.48 17% ------ ------ ------ 16.85 22.64 5.79
1.49 17% --.--- ------ ------ 17.01 22.85 5.84
1.50 18 ------
I ------ I
I
------ 17.17 23.08 5.91

-26-
 Trapezoidal or Cipolletti W eir- The trapezoidal or the Cipolletti weir,
named for the Italian engineer who designed it, is used extensively in irriga-
tion work in the Western United States. It gives equally accurate measure-
ments but is more difficult to construct than the rectangular weir. As the
name indicates, the notch is of h'apezoidal form as shown in Figure 9. The

o 0 0 0

Fig. 9. Trapezoidal or Cipolletti Weir.

side slopes are alike and have an inclination of 1 horizontal to 4 vertical. The
discharge may be considered in two parts, one through the rectangular area
of the length equal to the crest length, and the other through a triangular
area equal to the sum of the area of the two triangles formed at the ends
of the rectangle. The total discharge is therefore greater than from a rectangu-
lar contracted weir having an equal crest length. Cipolletti proposed giving
the sides such a slope that this increase would be just equal to the decrease
in discharge through a contracted weir caused by end contractions. Under
this condition the discharge is directly proportional to the length of crest;
i.e., a Cipolletti weir having a crest length of 4 feet discharges twice as
much as one having a crest length of 2 feet. The -recommended size of
trapezoidal weir to use with various size sh'eams of water is given in Table 5.

It should be noted that the property of equal discharge per unit length
of weir crest makes the Cipolletti weir an excellent device for use in division
of quantities of water in addition to being a measuring device. See page 71,
Dividers.

-27-
 FIG. 10 CREST LENGTHS 0" - 4 F1
Q=3367 LH~
v / V /' V
1.9

18-
23
22 / / /' : V V ----
1.7
21
I / V /'
V-
.-- V ----
20. V / V ./j EXAMPLE: TO. FIND DISCHARGE
16- 19 I
V
15- 18 / / V
.--
.--V FCR .' CREST LENGTH AND HEAD

1.4 17 L / / V V
I
CF 125 FT DI SCHARGE ; 18.8 CF S.

/ V· I I
/ / /' .....-- I
1.3
18
15 - r- - ---L--~. y- f- V ~V i ----I
Ie

~
to
w
~ 1.1
14
,4"'" V V .
~ h~~~~
13
A. ~ ¥ V ,i I l
~ 10. 12 z I
II
~ 0.9

:-l~lY'~~
0
f- '"/ ,
\oJ 10. ..
1: 0..8 w f-
9 I

l7 ~ g
0..7 f-
0..11
8
7
/
/ //
/ V V y
,;.'¢,C;X
"'(W-
"'
'FlGJ?r-
0..5 8
Ii, V V ~~." ~;r.2- ~ ~'"
/, V 'i
5
0..4

0.3
4 "
V \ 3:
.,
R
CRE:.. l'
NG1'''
I
DISCHARGE CURVES
3
/" [ij -'i'" FOR
0..2-

0..1
2
I
~#
IA~
ALl',' 0' CIPOLLETTI WEIRS
" "*' I 2 ,3 41 I I I I I I I 151 I I I I I I I 1 6 1 I I I I I I 17
0. 2 3 .. 5 1\ 8 g '0. II 12 13 14 ,5 18 17 18 19 20. 21 22 23 24 25 26 27 28 29 30. 31 32 33 34 35 38 37 38 39 40

QI5CHARGf IN C.F 5.

Fig. 10. Discharge curves for Cipolletti weirs.

l
 TABLE 4
Flow Over Cipolletti Weirs in Cubic Feet Per Second*

Head,
Crest length I For each addi-
tional foot of
crest in excess
Head, in feet in inches
(approx.)
I 1.0 foot I 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet of 4 ft.
(approx.)
Flow in cubic feet per second
I
0.10
0.11
1 3/16
15/16
0.107
0.123
0.160
0.185
I
0.214
0.246
0.321
0.370
0.429
0.494
0.108
0.124
0.12
0.13
17/16
19/16
0.140
0.158
0.210
0.237
I
0.280
0.316
0.421
0.474
0.562
0.632
0.141
0.159
0.14 I 1 11/16 0.177 0.264 I 0.352 0.528 I 0.706 0.177
0.15
0.16
I
I
113/16
1 15/16
0.195
0.216
0.293
0.322
0.390
0.430
0.586
0.644
0.782
0.860
0.196
0.216
0.17 21/16 0.237 0.353 I 0.470 0.705 0.941 0.236
0.18 23/16 0.258 0.384 I 0.512 0.768 1.024 0.257
0.19 2V4 0.280 0.417 I 0.555 0.832 1.110 0.278
0.20 2% 0.302 0.450 I 0.599 0.898 1.20 0.302
0.21 21,2 0.324 0.484 I 0.644 0.966 1.29 0.324
0.22 2% 0.349 519 0.691 1.04 1.38 0.35
0.23 2% 0.374 0.
0.555 1 0.739 I 1.11 1.47 0.37
I
0.24 2Ys 0.397 0.591 0.786 1.18 1.57 0.39
0.25 3 0.423 0.628 I 0.836 1.25 1.67 0.42
0.26 31fs 0.449 0.667 I 0.886 1.33 1.77 0.44
0.27 3% 0.475 0.705 I 0.937 1.40 1.87 0.47
0.28 3% 0.502 0.745 I 0.990 1.48 I 1.97 0.49
0.29 31,2 0.529 0.785 ! 1.04 1.56 2.08 0.52
0.30 3% 0.557 0.827 1.10 1.64 2.19 0.55
0.31 3% 0.586 0.869 1.15 1.73 2.30 0.57
0.32 313/16 0.615 0.911 1.21 1.81 2.41 0.60
0.33 315/16 0.644 0.954 1.27 1.89 2.52 0.62
0.34
0.35
I 41/16
43/16
0.675
0.705
1.00
1.04
1.32
1.38
1.98
2.07
2.64
2.75
0.66
0.69
0.36 45/16 0.735 1.09 1.44 2.16 2.87 0.71
0.37 47/16 0.767 1.13 1.50 2.25 2.99 0.74
0.38 49/16 0.799 1.18 1.57 2.34 3.11 0.78
0.39 411/16 0.832 1.23 1.63 2.43 3.24 I 0.81
, I
0.40 413/16 0.866 1.28 1.69 2.53 3.36 0.84
0.41 415/16 0.899 1.32 1.76 2.62 3.49 0.87
0.42 51/16 0.932 1.37 1.82 2.72 3.61 0.89
0.43 53/16 0.967 I 1.42 I 1.89 2.81 3.74 0.93
0.44 5% 1.00 1.47 I 1.95 2.91 3.87 0.97
0.45 5% 1.04 I 1.53 I 2.02 3.01 4.01 1.00
0.46 51,2 1.07 1.58 I 2.09 3.11 4.14 1.02
0.47 5% 1.11 1.63 2.16 3.21 4.28 1.06
0.48 5% 1.15 1.68 I 2.23 3.32 4.41 1.10
0.49 5% 1.18 1.74 I 2.30 3.42 4.55 1.13
0.50 6 1.22 1.79 2.37 3.53 4.69 1.16
0.51 6% 1.26 1.85 2.44 3.64 4.83 1.20
0.52 6% 1.30 1.90 2.51 3.74 4.97 1.24
0.53 6% 1.34 1.96 2.59 3.85 5.12 1.26
0.54 61,2 1.38 2.02 2.66 3.96 5.26 1.30

·Computed [rom Cone's formula: (J = 3.2>17 L lI u " -. ~ ..~62L~';~ . . flU' + 0.609 H~·:;
-29-
 TABLE 4-(Continued)

Head,
Crest length I
,"c ~""foot
tional . .".
of
crest in excess
Head, In feet in inches 1.5 feet I I 3.0 feet I 4.0 feet of 4 ft.
(approx.)
I '''""' 1
2.0 feet

Flow in cubic feet per second

(approx.)

I
0.55 6% 1.42 2.07 2.74 4.07 5.41 1.33
0.56 6% 1.46 I 2.13 2.81 4.18 5.56 1.38
0.57 613/16 1.50 2.19 . 2.89 4.30 5.71 1.41
0.58 615/16 1.54 2.25 2.97 4.41 5.86 1.44
0.59 I 71/16 1.58 I
I
2.31 3.05 4.53
I
6.01 1.49
0.60 73/16 1.62 I 2.37 3.13 4.64 6.17 1.53
0.61 75/16 1.67 2.43 3.20 4,76 6.32 1.55
0.62 77/16 1.71 2.49 I 3.28 4.88 6.47 1.60
0.63
0.64
79/16 1.75
1.80
I 2.55
2.62
3.37
3.45
5.00
5.12
6.63
6.79
1.63
711/16 1.67
0.65
0.66
I
713/16
715/16
1.84
1.89
I 2.68
2.75
3.53
3.61
5.24
5.36
6.95
7.11
1.72
1.75
0.67 81/16 1.93 I 2.81 3.70 5.48 7.28 1.79
0.68 83/16 1.98 I 2.87 I 3.79 5.61 7.44 1.83
0.69 8% 2.02 2.94 3.87 5.73 7.61 1.87
0.70 I, 8% 2.07 I 3.01 3.95 5.86 7.77 1.91
0.71
0.72
8Y2
8%
2.12
2.16
I 3.07
3.14
4.04
4.13
5.99
6.12
7.94
8.11
1.95
1.99
0.73 8% 2.21 3.21 4.22 6.24 8.28 2.03
0.74 8% 2.26 3.28 4.31 6.38 8.45 2.08
0.75 9
I 2.31 3.35 4.40 6.51 8.62 2.12
0.76 9% 2.36 3.42 4.49 6.64 8.80 2.16
0.77 9Y4 2.41 3.49 4.58 6.77 8.97 2.21
0.78 9% 2.46 3.56 4.67 6.90 9.15 2.24
0.79 9% 2.51 I 3.63 4.76 7.04 9.33 2.29
0.80 9% 2.56 3.70 I 4.85 7.18 9.51 2.33
0.81 9% 2.61 3.77 4.95 7.31 9.69 2.38
0.82 913/16 2.66 3.84 5.04 7.45 9.87 2.42
0.83 9 15/16 2.71 3.92 5.14 7.59 10.05 2.46
0.84 10 1/16 2.77 3.99 5.23 7.73 10.23 2.51
I, I
0.85 103/16 2.82 4.07 5.33 7.87 10.42 2.55
0.86 105/16 2.87 4.14 5.43 8.01 10.60 2.60
0.87 10 7/16 2.93 4.22 5.52 8.15 10.79 2.64
0.88 109/16 2.98 4.29 5.62 8.30 10.98 8.69
0.89 10 11/16 3.04 4.37 5.72 8.44 11.17 2.72
I
0.90 1013/16 3.09 4.45 5.82 8.59 11.36 2.77
0.91 10 15/16 3.15 4.53 5.92 8.73 11.55 2.82
0.92 111/16 3.20 4.60 6.02 8.88 11.74 2.87
0.93 11 3/16 3.26 4.68 6.13 9.03 11.94 2.91
0.94 11% 3.32 4.76 6.23 9.17 12.13 2.96
0.95 11% 3.37 4.84 6.33 I 9.32 12.33 3.00
0.96 11% 3.43 4.92 6.44 9.48 12.53 3.05
0.97 11% 3.49 5.00 6.55 9.62 12.72 3.10
0.98 11% 3.55 5.09 6.64 9.78 12.92 3.14
0.99 11% 3.61 5.17 6.75 9.93 13.12 3.19
1.00 12 3.67 5.25 6.86 10.08 13.32 3.24
1.01 12% ------ 5.33 6.96 10.24 13.53 3.29
1.02 12Y4 ------ 5.42 7.07 10.40 13.73 3.34
1.03 12% ---_.- 5.50 7.18 10.55 13.94 3.38
1.04 12% ._---. 5.59 7.29 10.71 14.15 3.43
I I I I
 TABLE 4-(Continued)
Crest length 1 Forea~
tional foot of
Head, crest in excess

I 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet

Head, In feet in inches 1.0 foot of 4 fl.
(approx.) (approx.)
Flow in cubic feet per second

I
1.05 12% ------ 5.67 \ 7.40 10.87 14.35 3.48
1.06 12% ---._. 5.76 7.51 1l.03 14.56 3.53
1.07 1213/16 --"--- 5.84 7.62 1Ll8 14.76 3.58
1.08 1215/16 .--._- 5.93 7.73 11.35 14.98 3.63
6.02 7.84 11.51 15.19 3.68
1.09
1.10
II 13 1/16
133/16
---.--

--"--- 6.11 7.96 11.68 15.41 3.74

1.11 I 135/16 ------ 6.20 8.07 11.84 15.62 3.79
1.12 137/16 ---.-- 6.29 8.18 12.00 15.84 3.84
1.13 139/16 .-- .. - 6.37 8.29 12.16 16.04 3.88
1.14 1311/16 .--.-- 6.46 8.41 12.33 16.26 3.94
1
1.15 I 1313/16 ---_ .. 6.56 8.53 12.50 16.48 3.98
Ll6 1315/16 I ._--_. 6.65 8.65 12.67 16.70 4.03
Ll7 I 141/16 .. ---- 6.74 8.76 12.84 16.93 4.08
Ll8 143/16 .. ---- 6.83 8.88 13.01 17.15 4.14
Ll9 I
I
14¥4 I .- .. _- II 6.93 9.00 13.18 I 17.37 4.19
1.20 I 14% I .... -- i 7.02 9.12 13.35 I 17.59 4.24
1.21 I 14% I 7.11 9.24 13.52 I 17.81 4.29
1.22
1.23
I
I
14%
14%
II .-----
.. - ...
.. ----
I 7.20
I 7.30
9.36
9.48
13.69 I
13.87 I
18.03
18.27
4.34
4.40
I 7.40 9.60 14. 04 1 18.49 4.46
1.24
1.25
,I
I
14%
15
II .--._.
I
---_ .. I 7.49 9.72 14.21 18.71 4.51
1.26 15¥8 I _.-._. I ------ ------ 14.39 I 18.95 4.57
1.27 I 15% I .. _--- I .--_.- .- __ .. 14.56 19.17 4.62
1.28 I 15% I .--.-. I .-_.-- -_.".- 14.74/ 19.41 4.67
14.92 19.65 4.73
1.29
1.30
I
I
I
15112
15%
I ·--0-'

------
II ... ---

---_ ..
----.-

.. -- .. 15.11 19.88 4.78

1.31 I 15% I _.---- I .. ---- .. --.- 15.29 I
20.12 4.82
1.32 I 1513/16 I .--._- I ------ .- .... 15.46 I 20.34 4.88
1.33 1515/16 I .-"._- .----- ---- .. 1.5.64 I 20.58 4.94
1.34 I
I
161/16 I .-_ .. - II ------ ._--.-
15.
82
1
20.82 4.99
1.35 I 163/16 I 16.01 21.06 5.05
1.36
1.37
I
I
165/16
167/16 I
I ......
._._.-
.---_.
I
1
_.0·--
... _.-
. - __ -0
------
_.- ...
_.- ...
16.19 21.29
16.37 1 21.53
5.10
5.16
1.38 1 169/16 I '-".- I ... --- ...... 16.57 I 21.78 5.22
1.39 1 16 11/161 .. -.-. 1 ------ - __ ._- 16.75 I 22.02 5.28
I I
1.40 1613/16 ... -_- I _.-_ .. _."-- 94 22.27 5.33
1
16. 1
1.41 I 1615/16 I -- .... 1 ..---- _.-._- 17.13 22.51 5.39
1.42 171/16 1 _..... 1 ------ .-- .. - 17.31 22.75 5.44
1.43 I 173/16 1 ... --- I _.. --- I .... -. 17.51 1 23.01 5.50
1.44 I
I
17% 1 --_._. 1
I
.. ----
I . __ ._-
17.70 I 23.26 5.55
1.45 1 173/8 11
--._-- 1 .. - . . - II • __ 0 • • 17.89
08
23.50
23.75
5.62
5.67
1.46 17Yz -'0.0- .----- .... --
18.
1.47 I 17% 18.28 1
24.01 5.73
1.48 17% I
---_.-
._----
\
I
.... '-
-.---- II --_ .. -
..... - 18.47
I
24.26 5.79
1.49
I 17% -"-" I
I
.----- --- ... 18.66
I
24..50 5.84
1.50
I 18
\
---.--
I ------
I .--_.- 18.85 24.75
I
5.91

-31-
 TABLE 5-Recommended sizes of Cipo/letti weirs.

Flow lvlaxillllllll I-lead Crest length

(c. f. s.) (Ft.) (Ft.)

0.30 to 2.30 0.75 l.0

2.00 to 4.00 0.85 1..5
3.00 to 7.00 1.02 2.0
5.00 to 14.00 1.24 3.0
8.00 to 22.00 lAO 4.0

Discharge curves for Cipolletti weirs having crest lengths from 6 inches
to 4 feet are shown in Figure 10. Discharge tables for Cipolletti weirs are
included in Table 4.

Ninety-Degree Triangular Notch Weir-The triangular notch weir, Figure

11, is especially adapted to the measurement of small quantities of water
varying from a very small fraction of a second-foot to about 2.5 second feet.
Its shape makes it easy to construct and install. The 90-degree weir should
be so placed that each side makes an angle of 45 degrees or half pitch with

Fig. 11. Ninety-Degree Triangular Notch weir.

the vertical. For a maximum discharge of 2.5 second-feet, the head H is ap-
proximately 1 foot. The total necessary difference in elevation of the water
surface upstream and downsh'eam from the weir therefore approaches Bf feet.
(See requirement No.8, page 19).

-32-
 Discharge curves for the triangular weir are shown in Figure 12. For
example, if the depth of water over the vertex or lowest point in the notch
is 9 inches, the discharge is 1.22 second feet.

1.3 -
15
.. ~

14

1.1
13
I ;
,
.... .,..
I
I

I I ,
, ,
, ;~/" -~ --
I
II
0.9 I
I
• ',.e
'<$f--t-- - .--. ---
" '""
I
j -
I I L - -
~/
,
I +- - -I -
10 'r.,/
, I

-~.a
w
.... 9
C/) _
? '7 111I I
EXAMPLES TO FIND DISCHARGE
FOR A HEAD OF 3t INCHES, "
u...
0 07 I
W
~L FOLLOW HORIZONTALLY ALONG DOTTED
au j.1 II NE TO INTERSECTION OF DISCHARGE
Z
-
J"Z
w
I-
7-
a
~

l.'
CURVE THEN
AND READ A
lIKEWI SE
DROP VERTICALLY DOWN
DISCHARGE OF 0.115 C.F.S.
FOR A HEAD OF 13 IN.
«
~ 0.5 6 w J:
DiScHARGE = 3,04 C. F. S.
"f ~;-
a t-
« .... . . '"f""!' I
6 IN

~" 5 I (

~
V'~
f-4 --V ~ I
0.3- ~
3 DIS ,...-FtARGl
~ --
" " CORVE! s:--
"' ... fOB
I
z .., ,0
il,
Ng:r~H \.~JR
••
I
Q=2.52H 2 .47'
0.1 '. I
1

010
o 1.0 2,0 3.0 4.0

DISCHARGE IN C.F.S.

Fig. 12. Dicharge curves for 90° notch weir.

-33-

-
 TABLE 6
Flow Over 90-Degree Triangular-Notch Weir in Cubic Feet Per Second
and Gallons Per Minute

Flow in cubic feet Flow in gallons

Head in feet Heat!, in inches (approx.) per second per minute

0.10 13/16 0.008 3.6

0.11 15/16 0.010 4.6
0.12 17/16 0.012 5.7
0.13 19/16 0.016 6.8
0.14 111/16 0.019 8.1
0.15 113/16 0.022 9.5
0.16 115/16 0.026 11.2
0.17 21/16 0.031 13.1
0.18 23/16 0.035 15.2
0.19 2% 0.040 17.5
0.20 2% 0.046 19.9
0.21 21h 0.052 22.5
0.22 2% 0.058 25.3
0.23 2% 0.065 28.3
0.24 2% 0.072 31.6
0.25 3 0.080 35.1
0.26 3% 0.088 38.8
0.27 3% 0.096 42.8
0.28 3% 0.106 47.0
0.29 31h 0.115 51.4
0.30 3% 0.125 56.0
0.31 3% 0.136 60.8
0.32 313/16 0.147 65.8
0.33 315/16 0.159 71.1
0.34 41/16 0.171 76.7

0.35 43/16 0.184 82.6

0.36 4 '5/16 0.197 88.8
0.37 47/16 0.211 95.0
0.38 49/16 0.226 101.0
0.39 411/16 0.240 108.0
0.40 413/16 0.256 115
0.41 415/16 0.272 122
0.42 51/16 0.289 130
0.43 53/16 0.306 137
0.44 51J4 0.324 145
0.45 5% 0.343 154
0.46 51h 0.362 162
0.47 5% 0.382 171
0.48 5% 0.403 181
0.49 5% . 0.424 190
0.50 6 0.445 200
0.51 6% 0.468 210
0.52 6% 0.491 220
0.53 6% 0.515 231
0.54 61h 0.539 242

-34-
 TABLE 6-(Continued)

Flow in cubic feet Flow in gallons

Head in feet Head, in inches (approx.) per second per minute

0.55 6% 0.564 253

0.56 6% 0.590 265
0.57 613/16 0.617 277
0.58 615/16 0.644 289
0.59 71/16 0.672 302

0.60 73/16 0.700 315

0.61 75/16 0.730 328
0.62 77/16 0.760 341
0.63 79/16 0.790 355
0.64 711/16 0.822 369

0.65 713/16 0.854 383

0.66 715/16 0.887 398
0.67 81/16 0.921 413
0.68 83/16 0.955 429
0.69 81;'4 0.991 445

0.70 83k 1.03 461

0.71 81;'2 1.06 477
0.72 8% 1.10 494
0.73 8% 1.14 512
0.74 8% 1.18 530

0.75 9 1.22 548

0.76 91;'8 1.26 566
0.77 91;'4 1.30 585
0.78 9% 1.34 604
0.79 91;'2 1.39 624

0.80 9% 1.43 644

0.81 9% 1,48 664
0.82 913/16 1.52 684
0.83 915/16 1.57 704
0.84 10 1/16 1.61 725
0.85 103/16 1.66 746
0.86 105/16 1.71 768
0.87 107/16 1.76 790
0.88 109/16 1.81 812
9.89 1011/16 1.86 835
0.90 1013/16 1.92 858
0.91 1015/16 1.97 882
0.92 111/16 2.02 906
0.93 11 3/16 2.08 931
0.94 111;'4 2.13 956
0.95 11% 2.19 983
0.96 1m 2.25 1,010
0.97 11% 2.31 1.040
0.98 11% 2.37 1,060
0.99 11% 2.43 1,090

-35-
 TABLE 6-(Continued)

Flow in cubic feet Flow in gallons

Head in feet I Head, in inches (approx.) per second per minute

1.00 12 2.49 1,120

1.01 12'1s 2.55 1,140
1.02 12% 2.61 I 1,170
1.03 12% 2.68 1,200
1.04 12% 2.74 1,230

1.05 12% 2.81 1,260

1.06 12% 2.87 1,290
1.07 1213/16 2.94 1,320
1.08 1215/16 3.01 1,350
1.09 131/16 3.08 1,380

1.10 133/16 3.15 1,410

1.11 155/16 3.22 1,440
1.12 137/16 3.30 1,480
1.13 139/16 3.37 1,510
1.14 1311/16 3.44 1,540

1.15 1313/16 3.52 1,580

1.16 1315/16 3.59 1,610
1.17 141/16 3.67 1,650
1.18 143/16 3.75 1,680
1.19 14% 3.83 1,720

1.20 14% 3.91 1,760

RECTANGULAR SUPPRESSED WEIR

The rectangular suppressed weir or weir without end conh'actions consists
of a bulkhead in a rectangular flume section. The bulkhead should be suffi-
ciently high from the bottom of the flume that the distance from the weir

-36-
crest to the bottom of the flume is at least twice and preferably three times the
head of the water expected to flow over the weir. The flume section should
be unifOlm in cross-section, having a horizontal base and vertical side at any
cross-section. The bulkhead should be set in a vertical plane, and the up-
stream face should be smooth with a crest width not in excess of W' in thick-
ness. The crest of the weir must be horizontal. The head is determined in
the same manner as for other weirs. For more accurate results, a stilling well
(measuring well) and a hook gauge with vernier are recommended.

The water surface as it falls over the crest of a suppressed weir com-
pletely fills the flume, and cuts off the free circulation of air under the over-
falling sheet. For the weir to fu;]ction properly, artificial ventilation should
be provided by drilling a small hole in each sidc wall near the downstream
edge and a little below the weir crest.

Discharge curves for the rectangular suppressed weir arc shown in

Figure 13. For example, if the depth of water Rowing over the crest of a
I-foot-high weir (length of weir I foot) is 0.75 feet, the discharge from curves
is 2.32 c.f.s. This result may be checked by reference to Table 7.

[11;."'1'\.[", TO FIND OtSCHAR~E, H[I;I).0.7,.' FOR W[IR /i[/Cili" 0' l

FOLLOW BAOItEN LIHE rIOF'tlZONTA.LLT TO Li'ITi!:ftS[(iT'ON$ WITH CoJl'IVES
FOR !' W[IR HEIGHT AltO " W[IR HEIGHT, 1ll0l0ROP VERTICALLY AM
R[AD 2..18 AMP :l.ll C". RE,P(CTIV[LY ON THE LOWER SGAll THEN,
Ill' PllltCT INT[I!:PO\,ATIOH, [)IHU:[HC£ IS 2.32- 2.18.0.1' 50
0.2:.18'0.07.2:.2' c."" .. VIl\.U[ '1\0111 "4.II\'[ te. 2.22 C.F.5.

DISCHARGE CURVES
'00
2
SUPPRESSED RECTANGULAR WEIRS
O·tIllL~
..
J I

"
20 .., •0 7 ••
OI5CKARGE IN c."'.,. Pt:R fOOT Of W[I'I ",,-[,T

Fig. 13. Discharge curves for suppressed rectangular weirs.

-37 -
 TABLE 7
Flow Over Rectangular Suppressed Weirs in Cubic Feet Per Second*

Weir height

Head,
in feet
inHead,
inches II
0.5 foot I 0.75 foot I 1.0 foot I 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet
(approx.)
Flow in cubic feet per second per foot of weir crest

0.10 13/16 0.111 0.110 0.109 0.109 I 0.108 I 0.108 0.108

0.11 15/16 0.127 0.126 0.126 0.125 125 0.125 0.124
0.12 17/16 0.145 0.144 0.143 0.142 0.
0.142 0.141 1 0.141
0.13 19/16 0.163 0.162 0.161 0.160 0.159 0.159 0.159
0.14 1 11/16 0.182 0.180 0.179 0.178 0.178 0.177 0.177
0.15 113/16 0.202 0.200 0.199 0.197 0.197 0.196 0.196
0.16 115/16 0.223 0.220 0.219 0.217 0.216 0.216 0.215
0.17 21/16 0.244 0.241 0.239 0.238 0.237 0.236 0.235
0.18 23/16 0.266 0.263 0.261 0.259 0.257 0.257 0.256
0.19 2'14 0.289 0.285 0.283 0.280 0.279 0.277 0.277
0.20 2% 0.312 0.307 0.305 0.302 0.300 I 0.299 0.299
0.21 21h 0.336 0.331 0.328 0.325 0.324 0.322 0.322
0.22 2% 0.361 0.355 0.352 0.349 0.347 0.345 0.344
0.23 2% 0.387 0.386 0.376 0.372 0.370 0.369 0.368
0.24 2% 0.413 0.406 0.401 0.397 0.395 0.393 0.392
0.25 3 0.440 0.431 0.427 0.422 0.420 0.418 0.416
0.26 31fs 0.467 0.458 0.452 0.447 0.445. 0.442 0.442
0.27 3'14 0.495 0.485 0.479 0.473 0.471 0.468 0.467
0.28 3% 0.524 0.513 0.506 0.500 0.498 0.495 I 0.493
0.29 3'12 0.554 0.541 0.535 0.527 0.524 0.521 0.520 I
0.30 3% 0.583 0.569 0.562 0.555 0.552 0.548 0.545
0.31 311/16 0.614 0.559 0.591 0.583 0.580 0.576 0.574
0.32 313/16 0.645 0.629 0.620 0.612 0.608 0.604 I 0.602
0.33 515/16 0.677 0.659 0.650 0.641 0.637 0.633 I 0.631
0.34 41/16 0.709 0.690 0.681 0.670 0.666 662 0.660
0. 1
0.35 43/16 0.742 0.722 0.711 0.701 0.696 I 0.691 0.688
0.36 45/16 0.775 0.754 0.743 0.731 0.725 0.721 0.717
0.37 47/16 0.810 0.787 0.774 0.762 0.757 0.748
0.844 0.819 0.807 0.793 0.788 0.751
0.782 0.778
0.38 49/16
I'

0.39 411/16 0.881 0.853 0.840 0.826 0.819 0.813 0.809

0.40 413/16 0.916 0.888 0.873 0.858 0.851 0.840
415/16 0.952 0.922 0.907 I 0.890 0.883 0.844
0.876 '1
0.872
0.41
0.42 51/16 I 0.990 0.958 0.942 0.924 0.917 0.908 0.904
0.43 5% 1.03 0.994 0.976 0.958 0.950 0.941 0.937
0.44 5'14 1.07 1.03 1.01 0.993 0.983 0.974/ 0.969
0.45 5% 1.10 1.07 1.05 1.03 1.02 1.01 1.00
0.46 5'12 1.14 1.10 1.08 1.06 1.05 1.04 I 1.04
0.47 5% 1.18 1.14 1.12 1.10 1.09 1.08 1.07
0.48 5% 1.22 1.18 1.16 1.13 1.12 1.11 I
1.10
0.48 I 5% 1.27 1.22 1.19 1.17 1.16 1.15 1.14
I
0.50 6 1.31 1.26 1.23 1.21 1.20 1.18 I 1.18
0.51 6'1s 1.35 1.30 1.27 1.24 1.23 1.22 I 1.21
0.52 6'14 1.39 1.34 1.31 1.28 1.27 1.25 1.25
0.53
0.54
6%
61f2
1.44
1.48
1.38
1.42
1.35
1.39 I
1.32
1.36
1.30
1.34
1.29
1.33
I 1.28
1.32
II I
I

"C1mputed from the simplified form of Hehbo('k's ~()rmlila Q = 2/;3 111 L V2"ji,h:I/'.!, where 111 = 0.605 + O.OO~l28
+ -j;
0.08 <md P = height of weir crest above bottom ol ehimIld of approach. h-
 TABLE 7-(Continued)

Weir height

Head,
Head,
I 0.5 foot I 0.75 foot I 1.0 foot
in feet
in inches
(approx.) I I 1.5 feet
I 2.0 feet
I 3.0 feet I 4.0 feet
Flow in cubic feet per. second per foot of weir crest
I
I

~511/16
0.55 1.52 1.46 1.43 1.40 1.38 1.36 1.36
0.56 I 1.57 1.50 1.47 1.44 1.42 1.40 1.39
1
0.57 613/ 16 1
1.61 1.54 1.51 1.48 1.46 1.44 I 1.43
0.58 6 15/16 1.66 1.59 1.55 1.52 1.50 1.48 I 1.47
0.59 71/16 1.71 1.63 1.60 1.56 1.54 1.52 I 1.51
0.60 73/16 1.76 1.68 1.64 1.60 1.58 1.56 I 1.55
0.61 75/16 1.80 1.72 1.68 1.64 1.62 1.59 I 1.58
0.62 77/16 1.85 1.77 1.72 1.68 1.66 1.63 I 1.62
0.63 I 79/16 1.90 1.81 1.77 1.72 1.70 1.68 1.67
0.64 711/ 16 1 1.95 1.86 1.81 1.76 1.74 1.72 1.71
0.65 7 13/16 2.00
I
1.90 1.86 1.81 1.78 1.76
I 1.75
0.66 715/16 I 2.05 I 1.95 1.90 1.85 1.82 1.80 I 1.79
0.67 81/16 2.10 2.00 1.95 1.90 1.87 1.84 I 1.83
0.68 8% I 2.15 I 2.05 1.99 1.94 , 1.91 1.88 1.87
0.6~ 8% I
2.21 2.09 2.04 I 1.98 1.95 1.93 I 1.91
I I
0.70 8% \ 2.26 I 2.14 II 2.08 I 2.03 I 2.00 1.97 I 1.95
0.71 8% I 2.31 2.19 2.13 I 2.07 2.04 2.01 I 2.00
0.72 8% I 2.37 2.24 I 2.18 2.12 2.08 2.05 ! 2.04
0.73 8% I 2.42 2.29 I 2.23 I 2.16 2.13 2.10 I 2.08
0.74 8% 2.48 2.34 I 2.28 I 2.21 2.18 2.14 I 2.12
I I !
0.75 9 2.53 2.39 2.32 2.25 2.22 2.18 I 2.17
0.76 9% 2.59 2.45 I 2.37
I
I 2.30 2.27 2.23 I 2.21
0.77 9'14 2.65 2.50 I 2.43 2.35 2.31 2.27 I 2.26
0.78 9% 2.70 2.55 I 2.48 I 2.40 2.36 2.32 I 2.30
0.79 9% 2.76 2.60 I 2.52 I 2.45 2.41 2.37 I 2.35
I
0.80 9~8 2.82 2.66 I 2.58 i 2.49 2.45 2.41 ( 2.39
0.81 I 911/16 2.88 2.71 I 2.63 2.54 2.50 2.46 2.44
0.82 I 913/16 2.94 2.76 2.68 2.59 2.55 2.51 I 2.48
0.83 I 915/16 3.00 2.82 I
2.73 I 2.64 2.60 2.55 I 2.53
0.84 I 10 1/16 3.06 2.87 I 2.78 I 2.69 2.64 2.60 I 2.58
I I I
0.85 \ 103/16 . I 3.12 2.93 I 2.84 2.74 2.69 2.65 i 2.62
0.86 I 105/16 I 3.18 2.99 I 2.89 I 2.79 i 2.74 2.69 I 2.67
0.87 I 10 7/16 I 3.25 3.04 I 2.94 2.84 I 2.80 2.80 I 2.72
I
0.88 10 9/16 I 3.31 I' 3.10 I 3.00 I 2.90 I 2.84 2.79 I 2.76
0.89 I 10 11/16 I 3.37 II .3.16 I 3.0.5 I 2.95 I 2.89 2.84 I 2.81
I
0.90 I 10 13/16 i 3.43 I, 3.22 3.11 3.00 2.95 2.89 2.86
0.91 I 10 15/16 I 3.50 I 3.27 3.16 3.05 2.99 2.94 2.91
0.92 I 11 1/16 I 3.57 ,I
3.34 3.22 3.11 3.04 2.99 2.96
0.93 11 3/16 I 3.63 3.40 3.28 3.16 3.10 3.04 3.01
0.94 I 11% I 3.70 I 3.46 3.33 3.21 3.15 3.09 3.06
I I
0.95 I 11% I 3.76 I 3.52
. 3 ..58
3.39
3.45
3.26
3.32
3.20 3.14 3.11
0.96 I 11% 3.83 I 3.26 3.19 3.16
0.97 11% I .3.90 I 3.64 3.51 3.37 3.31 3.24 3.21
0.98 11% I I 3.97 I 3.70
I 3.76
3.57
3.62
3.42
3.48
3.36 3.29 3.26
0.99 IF/8 I 4.04 3.41 3.35 3.31
I I
1.00 I 12 I 4.11 I 3.82 3.68 3.54 3.47 3.40 3.36
1.01 I 12% I 3.89 3.74 3.59 3.52 3.45 3.41
1.02 I 12% I 3.95 3.80 3.65 3.58 3.50 3.47
1.03 I 12% 4.01 3.86 3.71 3.63 3.56 3.52
II
1.04 I 12% I 4.08 3.93 3.77 3.69 3.61 3.57
I I I
 TABLE 7 -(Conti n ued)

Weir height
Head,
Head,
in feet
in inches 0.5 foot I 0.75 foot I 1.0 foot I 1.5 feet I 2.0 feet I 3.0 feet I 4.0 feet
(approx.) I
Flow in cubic feet per second per foot of weir crest
I I
3.98 3.82 3.74 3.66 3.62
1.05 I 12rys ---,"" 4.14
3.71 3.67
1.06 12% 4.21 I 4.04 3.88 3.80
I
1.07 1213/16
------
---.-- 4.27
434
4.11
4.17
3.94
4.00
3.85
3.91
3.77
3.82
I 3.73
I 3.78
1.08 1215/16 ------ I I
1.09 131/16 .. _--- 4.41 4.24 4.05 3.97 3.88 3.83
I
1.10
1.11
133/16
135/16
.... --
.-.. _-
4.48
4.54
4.30
II 4.36
4.12
4.17
4.02
4.09
I 3.93
I 3.99
II 3.89
3.94
1.12 137/16 --- ... 4.61 4.42 4.23 II 4.14 4.04 3.99
1.13 139/16 .. _--- 4.68 I 4.49 4.29 I 4.19 I 4.10 I 4.05
1.14 13 11/16 -_ .... 4.75 4.55 4.36 4.26 4.15 4.11
I 4.41
I
4.31 4.21 I 4.16
1.15 13 13/16 .. -... 4.82 I 4.62
1.16 1315/16 --- .. - 4.89 4.68 4.47 4.37 4.27 4.22
1.17 14 1/16 ._-_.- 4.96 4.75 4.54 4.44 4.33 4.27
1.18 143/16 ---._. 5.03 I 4.82 4.60 4.49 4.38 4.33
1.19 14% _.---. 5.10 I 4.88 4.67 4.55 4.44 4.39
1.20 14% .--.-. 5.17
5.25
I 4.95
5.02
4.72
4.79
4.61
4.67
4.50
4.56
4.44
4.50
1.21 14% _.----
1.22 14% I .. "--- 5.32 5.09 4.85 4.73 4.61 I 4.56
I
5.39 . 5.16 4.92 4.79 4.68 I 4.61
1.23 14% I ---.--
4.73 4.67
1.24 14Ys I .,---- 5.47 5.22 I 4.98 4.88
1.25 15 I ------ 5.54 5.29 I 5.05 4.92 4.79 I 4.73
1.26
1.27
15%
15V4
I
I
------
------
.. _---
------
I 5.36
I
5.43
5.51
5.10
I 5.17
5.24
4.98
5.04
5.10
4.85
4.91
4.97
II 4.79
4.84
4.90
1.28 15% I .----- ."._--
1.29 15% I 5.57 5.30 5.16 5.03 I 4.96
------ -'.--.

I
I 5.23 5.09
I
5.02
1.30 15% _._--- . __ .-- 5.64 I 5.36
I I 5.72 5.44 5.29 5.16 5.08
1.31
1.32
1.33
15%
1513/16
15 15/16
I
-.-.--
_.-.--
.-"._-
."._--
------
.-._.-
I 5.79
I 5.86
5.50
I 5.57
5.36
5.42
5.22
5.28
I 5.14
I 5.20
1.34 16 1/16 I ------ --.--- 5.93 I 5.63 5.48 5.33 I 5.26
I
I
\

1.35 163/16 ---.-- I ------ 6.01 I 5.71 5.56 5.40 I 5.32

1.36 165/16 I
------ ---_.- II 6.08 I 5.77. I 5.62 5.46
5.52
5.38
I 5.45
1.37 167/16 I ------ ------ 6.15 I 5.84 I 5.68
1.38 169/16 I ---.-- --.--- 6.22
6.30
I 5.90 5.75
I 5.98 I 5.81
I 5.58
5.65
I 5.51
5.57
1.39 I 1611/ 16 1
_.---- .-. __ .
I
I
I
1.40 I 1613/16 6.38 I 6.04 5.87 5.71 5.62
1.41 1615/16 I
------
--- .. I
------
------ 6.46 6.12
I
I 5.95 5.78 II5.69
I
"

1.42 171/16 .. -0-- I ------ I 6.52 . 6.18 6.01 5.84 5.75

1.43 173/16 I ------ I ------ I 6.60 6.26 I 6.08 5.91 I 5.82
1.44 17% 6.68 6.32 6.15 5.97 I 5.88
------ ."----
I I I
I I
I

1.45 17% -.---- ._--_. I 6.76 I 6.40 6.21 6.03 I 5.94

1.46 171J2 ._---- -'._-- 6.84 I 6.46 6.28 6.09 I 6.00
1.47 17% --'--- ,"---- 6.91 I 6.53 I 6.35 6.17 I 6.06
1.48 17% 1 --_.-- I ------ 1 6.99 I 6.60 6.41 6.23
6.29
I .6.12
I 6.20
1.49 177/s I ------ I ------ I 7.07 I 6.68 6.49
I
1.50 18 ------ .-----
I
7.15 6.75 I 6.56 6.36 I 6.26

-40-
 RATING FLUMES
On many streams the steep slopes, gravel and debris makc the use of
weirs or orifices impracticable. The flow of such streams may be measured
by constructing a rating flume and calibrating it by determining the relation-
ship between the discharge and depth of water in the flume. The rating can
be done by measuring the water at various gauge hcights with a current
meter. The services of a competent engineer should be sought to rate the
flume. Once the device is calibrated the discharge can be determined by
reading the gauge placed in the flume; but if deposits of silt, growth of
weeds, or other obstacles change the conditions under which the flume was
rated, it must be re-rated.
The flume should be so located that the water enters parallel to the axis
of the flume and in such a position that the depth of water in the flume is not
affected by backwater or diversions immediately above or below the structure.
The Parshall flume is an excellent permanent rating flume.

SUBMERGED ORI'FICES
For sections in which the slope of the ditch or channel is so flat that it
is difficult to get the required head for flow over a weir and where the waters
carry considerable silt, a submerged orifice is sometimes used.
An orifice is a hole or opening cut in a bulkhead through which water
flows. If the opening is below the water surface on both sides of the bulk-
head, it is said to be submerged. 'Alhen the water surface on the downstream
side is below the opening, it is said to have a free discharge. Partial sub-
mergence occurs when the downstream water surface is between the elevations
of the top and bottom of the orifice. This condition should be avoided. Thc
submerged orifice is considered here as it is more adaptable for general use
under the heads available.
Submerged orifices may be divided into two types: (1) those having
orifices of fixed dimensions and (2) those built so the height of opcning m,)y
be varied. A standard submerged orifice has fixed dimensions. The opening
is sharp-edged and usually rectangular, with the width being from two to
six times thc height. ~ The adjustable submerged orifice is one in which the
height of opening and head may be varied to fit the conditions. It is usually
built with suppressed side contractions. The ordinary form is the simple head-
gate. The standard submerged orifice is the more reliable of these two types.
Submerged Orifice 'With Fixed Dimensions-The Amount of water that
passes through a submerged orifice of fixed dimensions is determined by
the difference in elevation of water surface upstream and downstream from

-41-
the bulkhead. Figure 14 shows diagrammatically the Row through a sub-
merged orifice. As the head H increases the discharge increases.
The depth of water or head may be measured by using carpenters' rules
or by s p e cia 11 y constructed
scales like those already sug-
gested for weirs. One scale
should be placed on the up-
stream side of the orifice and
one on the downstream side
with the zero end of each scale
at the same level near the top
of the structure. The head on
the orifice is equal to the dif-
ference in the scale readings.
For a ditch having Rat
grades, the allowable difference
in water level upstream and
downstream from the orifice is
limited. Therefore, the size
Fig. 14. Diagrammatic sketch showing How opening should be adapted to
through a submerged orifice.
the head available and the size
of stream.

Rules for installing submerged orifices, as set forth by the U. S. Reclama-

tion Service,3 are as follows:
"(a) The upstream edges of the orifice should be sharp and smooth and
the distance of each from the bounding surfaces of the channel
both on the upstream and on the downstream side should prefer-
ably be not less than twice the least dimension of the orifice.
" (b) The upstream face of the orifice wall should be vertical.
" (c) The top and bottom edges should be level from end to end.
"( d) The sides should be truly vertical.
"( e) The head on the orifice that should be measured is the actual dif-
ference in elevation between the water surface on the upstream
side of the orifice and the water surface on the downstream side
thereof.
" (f) The cross-sectional area of the water prism for 20 to 30 feet from
the orifice, on the upstream and on the downstream side thereof,
should be at least six times the cross-sectional area of the orifice.
"(g) Correction should be made for velOcity of approach where appre-
ciable errors are caused by neglecting the head due to it."

3"ManuaI for Measurement of Irrigation Water." U. S. Department of Interior,

Bureau of Reclamation. April, 1947.

-42-
 The main advantage of the submerged orifice is that it Can be used on
relatively level canals where it is not possible to obtain sufficient fall for weir
measurements. The submerged orifice is subject to the same disadvantages
as the weir-collecting floating debris, sand, and sediment. If the pond in
front of the orifice is allowed to silt up, the accuracy of the device is destroyed.
Figure 15 shows a perspective Df a wooden submerged orifice as seen from
upstream.

Fig. 15. Perspective of wooden submerged orifice structure.

Determination of Discharge-Discharges for submerged orifices of fixed

dimensions are given by the curves in Figure 16. These curvcs can be used
directly only in connection with an orifice having one of the eight cross-
sectional areas given-0.25, 0.5, 0.75 of a square foot, and so on up to 2 square
feet. For convenience in making measurements, an orifice should be so
designed that its cross-sectional area is equal to one of those given in Figure
16. Discharges through orifices having cross-sectional areas other than those
given by the curve may be computed by proportion. For the example indi-
cated on the figure the discharge equals 3.78 c.f.s. for an orifice area of 1.0
sq. ft. and a head of 0.6 ft. If the orifice area were 0.6 of a square foot, the
discharge would be 0.6 x 3.78 = 2.27 c.f.s. under the same head.

-43-
 w
u
u...
0:: '"
(/)
o
w
>
0::
.,

~~
::>
u
:G < ...
OlD
< O·
w II
a:O
<
..

, N
.~

..
S)H'j"1 NI O"3H
., ...
..o
N

o
'"o
<0
o
'" t-
O
"'0 .
0 '"o o
.l33J NI OY3H

Fig. 16. Discharge curves for submerged orifices with fixed dimensions.

- 44-
 TABLE 8
Flow Through Rectangular Submerged Orifices in Cubic Feet Per Second*

Cross-sectional area of orifice, A

Head, Head,
H, in inches 0.25 sq. ft.10.333 sq. ft.1 0.50 sq. ft.1 0.75 sq. ft.I1.00 sq. ft.I1.50 sq. ft.[2.00 sq. ft.
in feet (approx.)

I Flow in cubic feet per second

I
i
I I

0.489 I 0.73
0.01
0.02
0.03
VB
%
%
I 0.1221
0.173 ,
0.212 I
0.
163
0.230
0.282
1
0.245
0.346
0.424
0.367
0.518
0.635
0.691
0.847
I
1.04
0.98
1.38
1.69
0.04 % I 0. 245 1 0.326 \ 0.489 0.734 0.978 I 1.27
1.47 11\
1.96
0.05 % I 0.273 0.364 0.547 0.820 1.09 I 1.64 2.19
I I I
0.06 I % I 0.300 I 0.399 599 0.899 1.20 I 1.80 2.40
0.07 13/16 0.324 0.431 0.
0.647 1
0.971 1.29 I 1.94 I 2.59
0.08 15/16 0.346 0.461 0.691 1.04 1.38 I 2.07 I 2.77
0.09 11/16 0.367 0.489 0.734 1.10 2.20 2.94
1.47
0.10 13/16 0.387 0.518 I 0.773 1.16 1.56 II
2.32 3.09
0.11 15/16 0.406 0.540 \ 0.811 1.22 2.43 3.24
0.12 17/16 0.424 0.564 0.847 1.27 1.62 1
2.54 3.39
0.13 19/16 0.441 0.587 I 0.882 1.32 1.69
1.76 I 2.65 3.53
0.14 111/16 0.458 0.609 I 0.915 I 1.37 1.83 2.75 I 3.66
0.15 113/16 0.474 0.631 I 0.947 I 1.42 1.90 2.84 I 3.79
0.16
0.17
115/16
21/16
0.489
0.504
0.651
0.671
0.978
1.01
\1 \1
1.47
1.51
1.96
2.02
I\ 3.02
2.93
I
I 3.91
4.03
0.18 23/16 II
0.519 I 0.691 1.04 1.56 2.08 3.11 I 4.15
0.19 21/4 0.533 I 0.710 I 1.07 I 1.60 2.13 I
3.20 I 4.26
0.20 2% 0.547 0.729 1.09 1.64 2.19 3.28 4.38
1 1

0.21 2% 0.561 746 1.12 1.68 2.24 3.36 4.48

0.22 2% 0.574
1
0.
0.765 1 1.15 1.72 2.30 3.46 4.59
0.23 2% 0.587 0.781 1.17 1.76 2.35 3.52 4.69
0.24 2% 0.6QO I 0.798 I 1.20 1.80 2.40 3.60 4.79
0.25 3 0.612 I 0.815 I 1.22 1.83 2.45 3.67 4.89
I
0.26 3% 0.624 0.831 I 1.25 1.87 2.49 3.74 4.99
0.27 3% 0.636 0.846 I 1.27 1.91 2.54 3.81 5.08
0.28 3% 0.646 0.862 I 1.29 1.94 2.59 3.88 5.18
0.29 3% 0.659 0.878 I 1.32 1.98 2.64 3.96 .5.28
0.30 3% 0.670 0.892 I 1.34 2.01 2.68 4.02 5.36
I
0.31 3% 0.681 0.908 I 1.36 2.05 2.73 4.09 5.45
0.32 313/16 0.692 0.920 i 1.38 2.07 2.76 4.15 .5.53
0.33 315/16 0.703 0.936 I 1.41 2.11 2.81 4.22 .5.62
0.34 41/16 0.713 0.950 I 1.43 2.14 2.85 4.28 5.70
0.35 43/16 0.724 0.963 I 1.45 2.17 2.89 4.34 5.78
0.36 45/16 0.734 I 0.976 I 1.47 2.20 2.93 4.40 5.87
0.37 47/16 0.745 I 0.991 I 1.49 2.23 2.98 4.46 5.95
0.38 49/16 0.754 I 1.00 I 1.51 2.26 3.02 4.52 6.03
0.39 411/16 . 0.764 I 1.02 I 1.53 2.29 3.05 4.58 6.11
0.40 413/16 0.774 I 1.03 I 1.55 2.32 3.09 4.64 6.19
I I I
"Computed from the formula Q = 0.61 A y2gH.

-45-
 TABLE 8-(Continued)

Cross·sectional area of orifice, A

Head, Head,
H, in inches 0.25 sq. ft./O.33J sq. fl./O.50 sq. ft./ 0.75 sq. fl./1.00 sq. fl./1.50 sq. ft./2.00 sq. ft.
in feet (approx.)

Flow in cubic feet per second

I I I
0.41 I 4 15/161 0.783 I 1.04 1.57 2.35 3.13 4.70 6.27
0.42 51/16 0.792 1.06 1.59 2.38 3.17 4.75 6.34
0.43 I 53/16 0.802 I 1.07 1.60 2.41 3.21 4.81 6.42
0.44 I 5% I 0.811 I 1.08 1.62 2.43 3.24 4.87 6.49
0.45 5% I 0.820 I 1.09 1.64 2.46 3.28 4.92 6.56
I I I
0.46 I 5% I 0.829 I 1.10 1.66 2.49 3.32 4.98 6.64
0.47 5% I 0.839 I 1.12 1.68 2.52 3.36 5.04 6.71
0.48 5% 0.847) 1.13 1.70 2.54 3.39 5.08 6.78
0.49 5% 0.856 1.14 1.71 2.57 3.42 5.14 6.85
0.50 6 I 0.865 1.15 1.73 2.59 3.46 5.19 6.92
I I
0.51 6Va I 0.873 I 1.16 1.75 2.62 3.49 5.24 6.99
0.52 6% I 0.882 I 1.17 1.76 2.65 3.53 5.29 7.05
0.53 6% 0.890 1.19 1.78 2.67 3.56 5.34 7.12
0.54 6% 0.898 I 1.20 1.80 2.70 3.59 5.39 7.19
0.55 6% I 0.907 I 1.21 1.81 2.72 3.63 5.44 7.25
I I
0.56 6% I 0.915 I 1.22 1.83 2.75 3.66 5.49 7.32
0.57 613/161 0.923 I 1.23 1.85 2.77 3.69 5.54 7.38
0.58 615/16 I 0.931 I 1.24 1.86 2.79 3.73 5.59 7.45
0.59 71/16 I 0.939 I 1.25 1.88 2.82 3.76 5.64 7.51
0.60 73/16 I 0.947 I 1.26 1.90 2.84 3.79 5.68 7.58
I I
0.61 75/16 I 0.955 I 1.27 1.91 2.87 3.82 5.73 7.64
0.62 77/16 I 0.963 I 1.28 1.93 2.89 3.85 5.78 7.70
0.63 79/16 I 0.971 I 1.29 1.94 2.91 3.88 5.82 7.76
0.64 711/16 I 0.978 I 1.30 1.96 2.93 3.91 5.87 7.82
0.65 713/16 I 0.986 I 1.31 1.97 2.96 3.94 5.92 7.89
I I
0.66 715/16 I 0.993 1.32 1.99 2.98 3.97 5.96 7.95
0.67 81/16 I 1.00 1.33 2.00 3.00 4.00 6.01 8.01
0.68 83/16 I 1.01 1.34 2.02 3.02 4.03 6.05 8.06
0.69 8% I 1.02 1.35 2.03 3.05 4.06 6.10 8.13
0.70 8% I 1.02 1.36 2.05 3.07 4.09 6.14 8.18
I
0.71 8% I 1.03 1.37 2.06 3.09 4.12 6.19 8.25
0.72 8% I 1.04 1.38 2.08 3.11 4.15 6.23 8.30
0.73 8% I 1.05 1.39 2.09 3.14 4.18 6.27 8.36
0.74 8% I 1.05 1.40 2.10 3.16 4.21 6.31 8.42
0.75 9 1.06 1.41 2.12 3.18 4.24 6.36 8.48
I
0.76 9Va I 1.07 1.42 2.13 3.20 4.26 6.40 8.53
0.77 9% I 1.07 1.43 2.15 3.22 4.29 6.43 8.58
0.78 9% . I 1.08 1.44 2.16 3.24 4.32 6.48 8.64
0.79 9% 1.09 1.45 2.17 3.26 4.35 6.52 8.70
0.80 9% 1.09 1.46 2.19 3.28 4.38 6.56 8.75
I I

-46-
 If no curves or tables of discharge are available, this orifice can still be
used as the discharge can be determined by use of the formula:
Q=4.89A-yR
Where Q = discharge in cubic feet per second (c.f.s)
A = area of opening in square feet
H = difference in head in feet.
Example: Area of opening = 2 square feet
Measured difference in head = 0.5 foot.
Discharge Q = 4.89 x 2 x -Y0.5 = 6.92 c.f.s.

4
COMBINATION HEADGATE AND MEASURING DEVICES
The Bureau of Reclamation has developed what is known as a constant-
head, adjustable orifice turnout; it replaces the common turnout-gate-weir
combination. This device was designed to control and accurately measure
irrigation water without the excessive amount of adjustment and walking
usually required for the gate weir combination.

TABLE 9-Discharge tables for the constant-head orifice turnout. Capacity

20 second-feet. Gate size 24 inches by 30 inches. Constant-
head = 0.2 foot.
Gate opening Gate opening
Discharge in feet Discharge in feet
(second-feet) (second-feet)
2 gates 1 gate 2 gates 1 gate
I I
0.5 0.04 0.08 10.5 0.83
1.0 .08 .16 11.0 .87
1.5 .12 .24 11.5 .91
2.0 .16 .32 12.0 .95
2.5 .20 .40 12.5 .99
3.0 .24 .48 13.0 1.03
3.5 .28 .56 13.5 1.07
4.0 .32 .64 14.0 1.10
4.5 .36 .72 14.5 1.14
5.0 .40 .79 15.0 1.18
5.5 .44 .87 15.5 1.22
6.0 .48 .95 16.0 1.26
6.5 .52 1.03 16.5 1.30
7.0 .56 1.10 17.0 1.34
7.5 .60 1.18 17.5 1.37
8.0 .64 1.26 18.0 1.41
8.5 .68 1.34 18.5 1.45
9.0 .72 1.41 19.0 1.49
9.5 .76 1.49 19.5 1.53
10.0 .79 1.56 20.0 . 1.56

4"Manual for Measurement of Irrigation Water." U. S. Department of Interior,

Bureau of Reclamation. 1946.

-47-
 WEIR GAGES-
·....
...~
=-'=== #.:
....
":,:
,:. :.:.
:..4. ______ .:':•

. ...1-:1.."':""'.:~""'
.. :"':',7,~7 . ..",~:~
.• :!J.,.

I
SECTION A-A
I... A TURNOUT GATE
ORIFICE GAT~
ELEVATION
,I,
I-
-- --
FLOW ( ~~ ( ~/
-
,
I
I
I
I PLAN
I --
Fig. 17. Constant-Head Orifice.

TABLE 1 O-Discharge tables for the constant-head orifice turnout. Capac-

ity 10 second feet. Gate size 18 inches by 24 inches. Constant-
head = 0.2 foot.

Gate opening Gate opening

I in feet Discharge in feet
Discharge
(second-feet) (second-feet)
2 gates 1 gate 2 gates 1 gate
I I I
0.5 0.05 0.10 5.5 0.55
1.0 .10 .20 6.0 .60
1.5 .15 .30 6.5 .65
2.0 .20 .40 7.0 .70
2.5 .25 .50 7.5 .74
3.0 .30 .60 8.0 .79
3.5 .35 .70 8.5 .84
4.0 .40 .79 9.0 .89
4.5 .45 .89 9.5 .94
5.0 .50 .99 10.0 .99

-48-
 The structure consists essentially of two gates, the adjustable orifice gate
and the turnout gate. These are placed on the upstream and downstream
sides, respectively, of a stilling pool which is part of the turnout.
The 18 x 24-inch and 24 x 30-inch gates are used as orifices. These
gates are used in single-barrel and double-barrel turnouts. Figure 17 illush'ates
a single-barrel turnout.
The orifice is designed to operate at 0.2 foot effective head, which is
adjusted by the turnout (downstream) gate after the orifice gate is opened
to a height determined from tables compiled for various discharges and gate
openings. Details of this device are shown on Bureau drawings 40-D-3672
and 40-D-3673k which may be obtained from the Bureau of Reclamation,
Denver, Colorado.
The computed discharge tables included on the drawings are based on
;m assumed coefficient of approximately 0.66 in the following equation:

where
Q = discharge in cubic feet per second
H = differential head on orifice gate = 0.2 foot
A = area of the orifice gate opening in square feet
C = the coefficient of discharge (approximately 0.66).
G = acceleration of gravity = 32.2 feet per second per second
Calibration tests on a model of the constant head orifice turnout with a
scale ratio of 1 in the model to 2 in the prototype, were conducted in the
Bureau's hydraulic laboratory in the customhouse at Denver, Colorado. Tests
were made using the following conditions:
1. Two different gate sizes corresponding to 18 x 24 inches and 24 x 30
inches in the prototype.
2. Four different approach floors corresponding to those shown on the
plain drawings.
3. Single-barrel type.
4. Double-barrel type with both gates open equal amounts, and double-
barrel type with one gate open and one gate closed.
Tests 5 on plan 1 (See Bureau drawing 40-D-3672, double-barrel design
with uniform gate openings) showed that the discharge coefficient was essen-
tially constant for a given gate opening for various canal water surface eleva-
tions, but increased slightly with increased gate openings up to a prototype
gate opening of 1.5 feet. For larger gate openings, the coefficient increased
appreciably with an increase in the gate opening; also, the coefficient varied
inconsistently with a variation of canal water surface elevations. The same
results were obtained in plans 2, 3, and 4.

GTests by U.S.B.R.

-49-
 Operation with only one of the two gates open gave satisfactory co-
efficients for small gate openings, but for larger gate openings it was difficult
to obtain correct differential head because of rough and tilted water surface
between the orifice gate and the turnout gate.
The single-barrel type gave similar operation to that of the double-barrel
type with both gates opened equal amounts, and the same discharge co-
efficients were obtained.
Table 30 and 31 give discharge with increases of 0.5 second foot for
various gate openings of both of the double-barrel and single-barrel types of
constant-head orifice-turnout sh'uctures. The constant-head differential is
0.2 foot.
The tests showed that the coefficient of discharge C in the formula
Q = CVA 2gH varied from 0.685 to 0.713.

COMMERCIAL GATES
Another combination headgate and measuring device that has proved
successful is a commercial gate sold under the name of Calco Metergate. 6
This gate is available in sizes from 8 inches to 48 inches in diameter.
The principle of operation of these gates is similar to that of the sub-
merged orifice or to the double orifice gate just described. They are especially
adapted for use at lateral outlets for they serve as headgates and also as water
measuring devices. Figure 18 illustrates the installation of the gate for a
lateral outlet through a canal bank. In installing, care must be taken to see

AMOUNT Of GATE
CP[NINC IS SHOWN
BY DISTANCE &Tw[EN
NOTCH ON ROO AND
Ta' Of Ko\NDYIH[EL
Hue r=
THE TOP OF THE PIPE
MUS T NOT BE LESS
THAN 6" BELOW BOTTOM
OF OUTLET DITCH

BOTTOM OF
SUPPLY DITCH
/

Fig. 18. Calibrated commercial gate installed in canal bank.

6Handbook of Water Control, by the Hardesty Division, Armco Drainage & Metal
Products Company. 1943.

-50-
that the outlet pipe is low enough to insure the proper submergence of the
outlet, which should not be less than 6 inches under lowest conditions.

Two measurements are necessary for finding the discharge: the amount
of gate opening as found by measuring the length of rod coming through the
handwheel and the difference in the elevations of the upstream and down-
stream water surfaces. Knowing these two measurements, one may enter
tables or curves supplied by the manufacturer of the gate and find the dis-
charge.

For a loss of head ranging from 1 inch to 18 inches, discharges from

approximately one quarter second foot to 78 second feet may be measured
through Standard Calco Metergates.

PARSHALL MEASURING FLUME

The Parshall Measuring Flume' is a device having a converging inlet
section, a throat section with straight parallel sides, and an outlet se~tion
which diverges (See Figure 19). The Parshall Measuring Flume is a water
measuring device by which the water flowing in an open channel can be
measured satisfactorily with a minimum loss of head. The loss of head for

Fig. 19. Eight-foot Parshall Measuring Flume located in the Logan Northern Canal
near Logan, Utah.
7Colorado Experiment Station Bulletin 423, "The Parshall Measuring Flume." 1936

- 51-
the free flow limit is only about 25 per cent of that for the overpour weir.
The accuracy of discharge measurements with this flume, under normal operat-
ing conditions, is probably within 2 to 5 per cent.

The Parshall flume may be operated as a free flow single head device
or under submerged flow conditions where two heads are involved. In this
bulletin, only the free flow single head device will be considered. Figure 20
shows a plan and longitudinal section of the Parshall flume together with a
letter on each dimension line. Table 11 gives the value of the dimensions
for various size flumes having a capacity varying from 0.35 c.f.s. to 176 c.f.s.
Flumes of 50-foot throat width with a capacity of 3000 second feet are possi-
ble. s The Parshall flume consists of a box of wood, concrete, or metal with a
level floor, a coverging section and vertical side walls. At the end of the
converging section the floor slopes downward 9 inches to 2 feet. The outlet
section is 3 feet long and diverges. The floor of the outlet section rises 6 inches
in 3 feet. The lower end of the outlet is 3 inches lower than the crest. These
dimensions are for flumes having a throat width of 1 foot or more .

. For free flow conditions, the submergence must not exceed 70 per cent
for Parshall flumes having a throat width of 1 foot or more; for smaller flumes,
such as a 3-inch flume, the submergence should not exceed 50 per cent.

( D ) +- E ~~ F ---+1
-r----:-
t

I
-1
-1'

PLAN

llEAS URE READ !!ERE

--r
B

:.-/
t 1~2/3 C~
I
G
~
--~--~--~~---------H~t~-----r---------T~K

-l<~__ ----=:_-
SECTION

Fig. 20. Plan and longitudinal section of Parshall measuring Burne.

8Colorado Experiment Station Bulletin 386, "Parshall Flumes of Large Size." 1932

- 52-
r
I

TABLE ll-A Table of Dimensions and Capacities for Parshall Flumes

Throat Free Flow

Width A Dimensions in Feet and Inches Capacities

ft. in. ABC Y3_ C_ _ I _ _·_D_-_I--E·

_ _2_ -I I.-~J H 1_ _K
__ I_M_~n._~~_~m_1 M~~I~~m
0' 3" 0'103/16" 0' 7" l' 6~8" l' 0%" l' 6" 0' 6" l' 0" l' 3" 0' 2%" 0' 1" .03 .6

0' 6" l' 31fz" l' 31fz" 2' 0 7/16" l' 4,5/16" 2' 0" l' 0" 2' A" l' 6" 0' 41h" 0' 3" .05 - 2.9

0' 9" 1'10%" l' 3" 2/10~B" 1'11%" 2' 10" l' 0" l' 6" 2' all 0' 4%" 0' 3" .1 1 5.1

l' 0" 2' 9%" 2' 011 4' 6" 3' 0" 4' 4%" 2' A" 3' 0" 3' 0" 0' 9" 0' 3" .4 16.0
CJ1 3' 0" 3' 0" 0' 9" 0' 3" .7 33.0
Go 2' 0" 3'11%" 3' 0" .5' 0" 3' 4" 4'10%" 2' 0"

.3' 0" 5' 1%" 4' 0" ,5' 6" 3' 8" 5' 4%" 2' OJI 3' 0" 3' 0" 0' 9" 0' 3" 1.0 50.0

4' 0" 6' 4%" 5' 0" 6' 0" 4' 0" 5' 10%" 2' 0" 3' 0" 3' 0" 0' 9" 0' 3" 1.3 68.0

5' 0" 7' 6i}~" 6' 0" 6' 6" 4' 4" 6' 4%" 2' A" 3' 0" 3' 0" 0' 9" 0' 3" 2.2 86.0

6' 0" 8' 9" 7' 0" 7' 0" 4' 8" 6'10%" 2' A" 3' 0" 3' 0" 0' 9" 0' 3" 2.6 104.0

7' 0" 9'11%" 8' 0" 7' 6" ,5' 0" 7' 4%" 2' ai' 3' 0" 3' 0" 0' 9" 0' 3" 4.1 121.0

8' 0" 11' 1%" 9' 0" 8' 0" 5' 4" 7'10%" 2' 011 3' 0" 3' 0" 0' 9" 0' 3" 4.6 140.0

10' 0"· 1,5' 7%" 12' 0" 9' 0" 6' 0" 14' 0" 3' 0" 6' 0" 3' 0" l' 1.5" I 0' 6" 6.0 200.0
I

"For Flumes of 10'-00" and larger dimensions see "Parshall Flumes of Larger Sizes," Bulletin 426-A, Colorado A. & M. Experiment
Station.
 Fig. 21. One-foot Parshall measuring flume installed near Smithfield, Utah.

Per cent submergence means the percentage that the downstream head is of
the upsh'eam head. Figure 21 shows one of a large number of small flumes
installed in Cache County, Utah.

The Parshall flume, like any other water-measuring structure, must be

properly installed and maintained to give best results. This requires that the
proper size flume for the conditions present be chosen. The maximum quan-
tity of water to be measured must first be determined, then the amount of
head available for use through the flume. To assist in the selection of the
proper size of flume for certain requirements, the diagram shown in Figure
22 has been prepared. Use of this diagram may best be illustrated by an
example: Let it be required to find the smallest size flume necessary to
measure a discharge of 5 second-feet with 62 per cent submergence and with
a loss of head not exceeding one-half foot. Enter the diagram at the lower
left and follow vertically on the line 62 until the curved discharge line 5 is
reached. At this point move horizontally to the right until the vertical line
0.50 is intersected. Note that this point is just a little to the right of the
diagonal line marked 1 foot throat width. This indicates that a flume width
of just a little less than 1 foot would be necessary but a 1 foot width would
be used. Discharge curves for Parshall flumes having throat widths from 6
inches to 10 feet are given in Figures 23 and 24.

-54-
 V
c.c.1 ' / r:;..-
.~ ::?
.1-C.'ct!)7
~~o /': V '/
~ eO '/ V 1/
~ 'g [7 7' / V
- - Q~
17// ' /
v • ~:
•
/' /" '/
'/
'/
h'/ ~o /' //
Jw. '7 ;- ./
,,0 / <J~ '/ /
'7 7
711. '/
,~
/' /' " ~~,,~
;..-
./
- 0"" '/
7
2- ,0 / ./
[.,.L 1-, ~~~.~ /
/ ,:'>

If / ~ ;f ' 7 ~ t/77
'/
•
~
7 A 1// / /

/
• ./
/i
./, V/
..
~

r7
7
7 r7 1.
/ " /
r7 '7 / 1/
0 ~ IL V
,/
r7
TTr7
/
/
-
'/ ~~ ". /
lL::: J.. - ,+
, 7' 7/ '/
•
77 1/ ./ '/ '7
rTf 7 '7 0"" / f r7/ / /
/ /
1/
'7 01' It:: / 1/
/ V /~
c;> /
1/ 1/
'/ ~ 'I' /
/ J- /'
/ 0> 7'
1/ 1 '/
/
as, eo .,
P'tACUl'TAQ[
.0 n
(N
70 15
IUIM[ROtNC[
eo ", '0 .Q4 M DI.a7 M.QIJO
,-OU or
J,HrAO.20IN .2$..lO
rttT
....u AO .$0 #J 2O.eo.to

Fig. 22. Diagram for determining the loss of head through the Parshall measuring
flume.

Directions f(J1' Placing Flumes, anil Example to Determine Correct Setting

of Crest Elevation:
(1) Locate the high water line on ditch bank where the flume is to be
installed.
(2) Select from capacity or discharge curves, Figure 23, the proper
depth of water or head HA that corresponds with the maximum
capacity of ditch. (Assume that a I-foot flume is to be used and
that the maximum discharge is 4.0 second-feet; therefore, the depth
of water on the crest HA is 1.0 feet.)
(3) Place the floor of the flume at a depth not more than 70 per cent
of HA below the high water line. In general the floor of the flume
should be placed as high in the ditch as the grade and other con-
ditions permit. For example, allow 70 per cent submergence, then
0.7 x 1.0 = 0.7 feet. Therefore, set flume crest no more than 0.7
feet below high water mark. The loss of head will be 1.0 feet - 0.7
feet = 0.3 feet.)

-55-
 >'!j FIG ~8
~' ,
I
211
L'"
24 I
~ 28 I I I I I
23 : I
27 I I
2.<!
9. 26 I
,
I
,
,
.,"'"::r'
21
25
I,
21J >T. , I I
'"'
(j'q
23
EXAMPLE TO ~rND DISCHARGE
11
'e" 19
FOR THROAT WIDTH OF I' AND HEAD
"<: 1.8 22
OF lA' DISCHARGE = 11.118 e.F.S.
I

'"' 21
1.7 ~
'"'" I.e
I
C' III I I
'"'
::r ....
1.5 18 III Y
I I

'::t>'"" ~1..4 17 ~ pf4 .l I

I
I
"- Ie ~ 1 I

~
z 13
CJ1 IS z
Vl
I 5'
:'12 14
-+ ........L~
: I
'" a I

U·
.,
"d ~I.I 13 ~
FT.>::
.<..<: i I

'"'::r'
"' 1.0 I ,
'0"
:- ~'",~ 4
,-

."~~
I
~ OIl II
10 et°?:.<.. 'I
i I
, ,
, ..

I
DISCHARGE CURVES
::t> 08
e I I fOR fREE fLOW IN
aro 0.7
9
8
- <0
Q'
.<.. <1: ..
;-q ~
~-+ .- ·t PARSHALL FLUME
D.&- 7 .; _nr>,~ I ~"+-- I
>-3

ffi·Tlt:
I i
6" TO 2' THROAT WIDTH
~ 0.5 II
0
;':l. 0.4 5 ;-1 .. " ,I'
p- -~- = 2.0& H~·!>8
4
....
,.- - i··· - - --- - FOR 6~ WIDTH Q
::; 0.3 , I I FOR 9- WIO'TH Q= 3.07 H .. I.!>J
3
5.: - .._- -
+
OOll
;. 0.2 1- -1-[+
I

-Fi-H
i :1 FOR 1'-2' WIDTH Q= 4 WH...'-!>22.W .

~
•
0.1
2
I
H-J-- I
+-iT H....=HEAD W= THROAT WIDTH

~ o 2 3 4 s II II 10 II 12 13 14 J5 If
 "fj rIc 24
qQ' I
~
.c.4 29 1 .,/
28
~ 2.3-
27 ,
22-
9. 2tI
I
I--f
1
,;
'"::r'
(') 2.1 25-

... ..,..
I I
~
(1Q
2.0 FT 1+
I
tz .-,~

7' .-1 .
Ig 2.3
r- - - - -Z -- - ,
'"
(') 22
1
-
=
...<: 1.8-
21
,
./
I
t.7
'"'.....
" lO
1.6- 19 , ./ - 1.;_. _.
...0..... I
... I~ 18 ,

c~
on ;
''"" l- 14
w
17 w
I: ,
::tl 16 ~
en
0
::; ...w 1.3
15
I
I.d"
--l I
! tc
I s· 14 -
Z

"d ~U 13 ~ DISCHARGE CURVES

...
~ ....
r 10 Fl. ~ ,
'" •
.<..~ ...~ I I

'"
::r'
09- II
, FOR FRIO!: FLOW IN
~ 10
y<' ,-<.
::tl 0.8- \ I PARSHALL FLUME
=
3 01
II
IS
1-'--
~ ;:!'-IO' THROAT WIDTH
0.8 7
>-l Q:: 4 WH 1.~22w·)(lJl~

~ 0.5 II
EXAMPLE TO F I NO DISCHARGE: HEAD = 2'
0
5
....
~

::;
Q4
03
4 , roLLOW BROKEN LINE KlRIZONTALLY TO
INTERSECTION OF CURVE FOR 5' THroAT
s.:
;. 0.2-
3 THEN ~p VERTICALLY AND
DISCHARGE OF 60 C.F.S.
READ
l
0.1
~
, I
....
~ o 10 20 30 50 50 70 110 gO 100 110 120 130 140 110
 TABLE 12
Free Flow Through Parshall Measuring Flumes*t

Upper head, Throat width

Ha

Inches
Feet (ap-
prox.)
Flow in cubic feet per second

/ I I0 I I I I I 1 I
0.10 /
0.11
1 3/16
15/16
0.
028
0.033
1
0.05
0.06
0.09 '
0.10 1
I -····1 ... 1

.. I 'j'::/
I ····· .. ·1 ·1
~:i~1
0.12 17/16 037 0.07
o 1311 9/16 0.
0.042 1 0.08 I .. ::::/ ./ . 1
0:14 1 11/16 0.047 0. 09 1 0.15 -I 1 · 1 - ....
1 I I I I I I
0.15 I 1 13/16'1 053 0.10 17
0. 1 ··1 I
0.16 1 15/16 0.
0.058 1 0.11 0.19 ·1 I .\
0.17 1 21/16 0.064 0.12 0. 20 1 ····11 ·1
0.18 I 2 3/16 0.14 ... [ i
I I
0.070/ 0.221
:::::1·:::/ :::::::1 I
0.19 21/4

0.20 I 2 3/s
0.076 0.15/ 0.24

0.26'
I I I
0.97
1 "I 1
I
·1· .. 1
1

0.21 2112
0.22 1 2 5/s
0.082
0.089
0.095
0. 16 1
0.
18
0.19
1
0.28
0.30
0.35/
0.37
0.401
0.66/
0.711
0.771
1.04
1.12
i:;:1
1.47 .....
I
1
.. ···1 .... i
I .. ·1
0.23 I 23/4 0. 82 1 1.20 1. 58 1 ...... ···1 ..·1
~:;~I
0.102 0.32 0.431 1

0.24 I
27/s 0.109/ 0.35 0.461 0.881 1.28/ 1.69 ... I .. I ... 1

,i I I 1 ! 1

0.25 I 3 0.117 0.23 37 0.491

0. 1
0.931 1. 37 1 1.801 2.221 2. 63 1 I ·1
0.26 3 1/8 0.124 0.25 0.39 0.51 \ 0.991 1.461 1.91 2.361 2. 80 1 I
0.131 0.26 0.54 1.051 1.5 5 1 2.031 2.50 297 1 1 . :
0.27 I' 31/4 0.411

~:~~I i:i!1
0.28 3 3/8 0.l38 0.28 0.44 1. 64 1 2.15\ 2.65 3. 15 1 ...... I 1
0.29 I 3 112 0. 146 1 0.29 0.46 1.731 2.27 2.80
3.33/1"'1
i I I i I
;:;;1 ~:i~
0.30 \ 3 /s 5 0.154 0.31 0.491 0.64/ 1.24/ 1.821 3.521 4.081 4.621
0.31 3 3/4 0.162 0.32 0.51 0.68 1.30 1. 92 1 3.71 4.301 4.88'1
0321 3 l3/16 0.170 0.34 0. 54 1 0.711 1.3 7 1 2. 02 1 2.65 3.281 3.901 4.52 5.l31
2. 12 1 2 78) 5. 39 1
~"~~I
0:33 3 15/16 0.179 0.36 0.74\ 1.441 3.441 4.101 4.751
0.34 41/16 0.187 0.38'1 0.77 1.501 2.221 2:92 3.611 4.30, 4.98/ 5.661
/ I I I I I
;:~~I 4.13
;:~:I
2. 32 4.50 5.221 5.931
~:!~I
0.35 1
43/16 0.196 0. 62 1
00801 1.57/ 1'

0.36 45/16 0.205 0.64 0.84 1.64 2.42 4.71 5.461 6. 20 1

53 3.34 4.92 5.701 6.481
~::~I i:~~1
0.37 47/16 0.213 0.43 0. 67 1
I 2. 1

0.38 49/16 0.222 0.45 0. 70 1 2.64 3.481 431 5.13 5.95\ 6.761
0.39/ 411/ 16 1 0.231 0.471 0.
73
1
0.95 1. 86 1 2. 75 1 3.621 4:49'1 5.351 6.201 7. 05 1
1 I 1
I 86 5.571 6.461 7.341 9.1

Ii~1
0.40 4 13/161 0.241 0.76) 0.991 1.93/ 3.77/ 4.68\1
2. 1
0.41 I 4 15/16 0.250 0.78 1.03/ 2.01 2.97 3.92 4.86 5.80, 6.721 7.64\ 9.5
0.42 I 5 1/16\
0.260 0.81 1.07 2.09 3.08 4.07 5.051 6.02 6.931 7.94\ 9.8
53/16 0.269 0.84 1.111 2.16 3.20 4.22 5.24 6.25 7.251 8.24 10.2
0.43 I 0.54\
0.44 51/4 0.279 0.56 0.87 1.15 2.24 3.32 4.38 5.43 6.48 7.521 8.55 1 10.6
I I 1
7.80/ 8.87 ! 11.0
0.45 I 5 3/8 0.289 0.58\ 0.90 1.19 2.32\' 3.441 4.54 5.63 ' 6.72
0.46 I 51/2 0.299 0.61 94
0. 1
1.23 2.40 3.56 4.70 5.83 1 6.96 8.081 9.19 1 11.4
0.471
5
5 /8 0.309 6.63 0.97 1.27 2.48 4.86 6.03 7.20 8.361 9. 51 1 11 .8
3.68)
0.48 53/4 0.319 0.65 1.31 2.57 3.80 5.03 6.24 7.44 8.651 9.8, 12.2
1.00/ 12 .6
0.49 5 7/8 0.329 0.67 1.03 1.35 2.65 3.92 5.20 6.45 7. 69 1 8.94110.2 1

i I 1 I
'Parshall, R. l. The improved Venturi flume. Colorado Agr. Exp. sta. SuI. 336:19-23. 1928.
tParshaJl, R. l. Measuring water in irrigation channels. U. S. Dept. of Agr. Farmer's SuI. 1683:10-11.1932.

- 58-
 TABLE 12-(Continued)

Upper head, Throat width

Ha

Inches
(ap-
inc~es Iinc~es Iinc~es I 1
foot f;et I fe3et I fe~t I fe5et I feet
6
I ,let I f~et I feet
10

Feet
prox.)
Flow in cubic feet per second

I I I I I I I I
0.50 6 0. 339 1
0.69 1.06 39
1. 1 2. 73 1 4.051 5.36 6.661 7. 94 1 23
9. 1 10.5 I 13.1
0.51 6 1/a 0.350 1.71 1.10 1.44 2.82 4.18 5.53 87 8.20 9.53 10.9 I 13.5
0.52 6V, 361 0.73 1.13 48 2.90 4.31 5.70 6. 1
7.09 8.46 9. 83 1 11.2 1 13.9
0.53 6'/a
0.
0.371
1
0.76 1.16 1.
1.52 1 2.99 4.44 5.88 7.30 8.72 10.1 . 11.5 i
14.3
0.54 6'12 0.382 0. 78 1 1.20 57 3.08 4.57 6.05 52 8.98 10.5 1 11.9 I 14.8
7. 1
0.80
1. 1 I
0.55 6 5/a 0.393 1. 23 1 1.62 17 4.701 6.231 7.74 9.25 10.8 12.2 \ 15.2
0.56 6'4 0.404 0.82 1.2 6 1 1. 66 1 3.
3.26 1 4. 84 1 6.41 7.97 9. 52 1 1J.! 12.6 15.7
0.57 6 13/16 0.415 0.85 1.30 0 3.35 4.98 6.59 8.20 9.791 1!.4 13.0 1 16.1
0.58 6 15/16 0.427 0.87 1.33 1.75 1
1.7 3.441
5.1! 6.77 8.43
10.1 1
11.7 13.3 I
16.6
0.59 71/16 0.438 0.89 1.37 1.80 3.53 5.25 6.96 8.66 10.4 12.0 13.7 , 17.1
I I
0.60 73/16 0. 450 1 0. 92 1 40 1.84 3.62 5.39 7.15 8.89 10.6 12.4 14.1 17.5
0.61
0.62
75/16
7 7/16
II 62
0.4 1
0.474
0. 94 1 1.44
97
1. 1
1.48
1.88
1.93
3.72
3.81
53
5. 1
5.68
7.34
7.53
9.13
9.37
10.9
11.2
12.7
13.0
14.5
14.8
18.0
18.5
0. 1
0.63 7 9/161 0.4 85 1 0.99 51 1. 98 1 3.91 5.82 1 7.72 6.61 11.5 13.4 15.2 19.0
0.64 7 11/16
0.
497
1 1. 02 1 1.
1.55 1 03
2. 1 4. 01 1 5.97, 7.91 9.85 11.8 13.7 15.6 19.5
I , I I
0.65 7 13/161 0. 509 1 1. 04 1 1. 59 1 2. 08 1 4.111 6. 12 1 8.111 10.1 12.1 I 14.1 16.0 19.9
0.66 7 15/161 0. 522 1 1. 07 1 1. 63 1 2. 13 1 4. 20 1 6. 26 1 8.311 10.3 12.4 I 14.4 16.4 20.4
6.411 8.51110.6 I 12.7
0.67 81116 0.534' 1.10 1. 66 1 18 4.30 14.8 16.8 20.9
2. 1
0.68 83/16 0. 546 1 1.12 70 2.23 4.40 6.56 8.71 10.9 ' 13.0 15.1 17.2 21.5
1.
1.74 1
0.69 8'1, 0.
558
1
1.15 2. 28 1 4.50 6.71 8.91 11.1 13.3 15.5 17.6 22.0

8 3/8 571
I I i 1
1.171 1. 78 1 6. 86 1 13.6
'."1
0.70 2.331 4.60 15.8 18.0 22.5
0.71 8 1/2 0.
0.584 1 1.20 1.82 2. 38 1 4.70 7. 02 1 9.32 "A
11.6 13.9 16.2 18.5 23.0
0.72 8V8 0.597 1.23 1. 86 1 2. 43 1 81 17 9.53 11.9 14.2 16.6 18.9 23.5
4. 7. 1
0.73 8 3/, 0. 610 1 26 1. 90 1 2. 48 1 4.91 1 7.33 9.74 12.1 14.5 16.9 19.3 24.1
1.
1.28 1 94
0.74 I 8 7/a 0. 623 1 1. 1
2. 53 1 5.02 7. 49 1 9.95112.4 14.9 17.3 19.7 24.6
I I
0.75
0.76 91/a
· .. ···1 131 1
1341
1.981
2. 02 1
2. 58 1 5.121
2. 63 1 5.231
7. 65 1
7. 81 1
10.2
10.4
I 12.7
12.9
15.2
15.5
17.7
18.0
20.1
20.6
25.1
...
1.36i
I 25.7
2. 06 1 34 7.97 10.6 I 26.2
' 'I
0.77 91J4 13.2 15.8 18.4 21.0
5. 1
0.78 9 3/8 " ...
1
,
39 2.10 2.74 5.44 8.13 10.8 13.5 16.2 18.8 21.5 I 26.8
0.79 91f2 .. ·· .. 1 1.42
1. 1 14
2. 1
2.80 5.551 8.30 11.0 13.8 16.5 19.2 21.9 I 27.3
, I
0.80 9 5/8 I
1.45 2. 18 1 85
2. 1 5.661 46
8. 1
11.3 I 14.0 16.8 , 19.6 22.4 I 27.9
0.81 9'14 1.48 2.22 2.90 5.77 8.63 11.5 I 14.3 17.2 20.0 22.8 I
28.5
0.82 913/16 ... 1 1.50 2.27 2. 96 1 5.88 8.791 11.7 14.6 17.5 20.4 23.3 29.0
0.83 1.53 2.31 3.021 6.00 8. 96 1 11.9 14.9 17.8 20.8 23.7 1 29.6
915/16)
0.84 10 1/16 I 1.56 2.35 3.07, 6.11 13
9. 1
12.2 15.2 18.2 21.2 24.2 I 30.2
I I i
0.85
0.86
110 3/16
10 5/16
0.87 10 7/16
0.88 I 10 9/16
j 1. 59 1
1.
62
1.65 1
68
2. 39 1
2.44
2.48
2.52
3. 12 1 6.221 9. 30 1

3.18\
6.331 9.481
3.24 6.441 6.65
3.29 6.56 82
12.4
12.6
12.8
13.1
15.5
15.8
16.0
16.3
18.5
18.9
19.2
19.6
I 21.6 24.6 i 30.8
I 22.0 i 25.1 I 31.4
I 22.4 125.6 . 31.9
22.8 26.1 1 32.5
0.89 I 10 11/16 ... 1.71
1. 1 2.57 35
3. 1
9. 1
6.68, 10.0 13.3 I 16.6 19.9 23.2 126.5 ! 33.1
I I I I 1

- .59-
 TABLE 12-(Continued)

Upper head. Throat width

lIa

Inches
Feet (ap-
prox.)
Flow in cubic feet per second

I 1 I 1 1 I
0.90 1 10 13/ 16 1 1.741 2. 61 1 3.41 6.80110.2 113.6116.9120.3 I 23.71 27.0 I 33.7
0.91 10 15/16 1.77 24.1 27.5 1 34.4
2.661 3.46 6.92110.4113.8 17.2120.7
0.92 11 1/16 1.81 2.70 3.52 7.03 10.5 14.0 17.5 21.0 24.5 I 28.0 35.0
0.93 11 3/16 1.84 2.75 3.58 7.151 10.7 14.3)17.8 21.4 24.9 28.5 35.6
0.94 111/4 1.87 2.791 3.64 7.27/10.9 I 14.5 18.1 21.8 I I
25.4 29.0 36.2
I 1

18.4 22.1 25.8

1
29.5 36.8
0.95 110/18 -+------ 1.90 2. 84 1 3.70 7.39 11.1 14.8
0.96 111;2 --.------ 1.93 2.88 3.76 7.51 11.3 15.0 18.8 22.5 26.2 30.0 37.5
0.97 11 5A8 -------- 1.97 2.93 3.82 7.63 11.4 15.3 19.1 22.9 26.7 30.5 38.1
0.98 1P;'~ ---+---- 2.00 2.98 3.88 7.75 11.6 15.5 19.4 23.2 27.1 31.0 38.7
0.99 117!8 -------- 2.03 3.02 3.94 7.88 11.8 15.8 19.7 23.6 26.6 31.5 39.4
,

1.00 12 -------- 2.06 3.07 4.00 8.00\12.0 16.0 20.0 24.0 28.0 32 0 40.0
1.01 121A8 -------- 2.09 3.12 4.06 8.12 12.2 16.3 20.3 24.4 .
28.4 1 32.5 40.7
20.6 24.8 28.9 33.0 41.3
1.02 121;'4 -------- 2.12 3.17 4.12 8. 25 1 12 .4 16.5
1.03 12 3A8 -------- 2.16 3.21 4.18 8.38 12.6 16.8 21.0 25.2 29.4 33.6 42.0
1.04 12,!:2 -------- 2.19 3.26 4.25 8.50/ 12.8 17.0 21.3 25.6 29.8 34.1 42.6
1 1 I 25.9 34.6 43.3
1.05 12 5A8 -------" 2.22 31 4.31 8.63 13.0 17.3 21.6 30.3
1.06 12 3;'4 -------- 2.26 3. 1 4.37
3.36 8.76 13.2 17.5 21.9 26.3 30.7 35.1 44.0
1.07 12 13/16 -------- 2.29 3.40 4.43 8.88 13.3 17.8 22.3 26.7 31.2 35.7 44.6
1.08 12 15/16 -------- 2.32 4.50 9.01 13.5 18.1 22.6 27.1 31.7 36.2 45.3
3.451 4.56
3.50 9.14 13.7 18.3 22.9 27.5 32.1 36.8 46.0
1.09 13 1/16 ----- .. - 2.36
I
1.10 133 16 .++----- 3.551 62 9. 27 1 13.9 18.6 23.3 27.9 32.6 37.3 46.7
2.401 3.60 4. 1 9.40 14.1 18.9 23.6 28.4 33.1 37.8 47.4
1.11 135 /16
/ 1 -------- 2.43 4.68
1.12 137 /16 ~.. ----- 2.46 3.65 4.75 9.54 14.3 19.1 23.9 28.8 33.6 38.4 48.0
1

1.13 139 16 ~-------

50 3.70 82 9.67 14.5 19.4 24.3 29.2 34.1 38.9 48.7
1.14 13 1/1/16 1 .------- 2.
2.53 1 3.75 4. 1
4.88 9.80 14.7 19.7 24.6 29.6 34.5 39.5 49.4
I 25.0
1
30.0 ' 35.0 40.1 50.1
1.15 13 13/16 ------~-
2.57 3.80 4.94\ 9.94/14.9 19.9
1.16 13 15/16 ____ w ___
2.60 3.85 5.01 10.1 15.1 20.2 25.3 30.4 35.5 40.6 50.8
1.17 141 /16 -------- 2.64 3.90 5.08 10.2 15.3 20.5 25.7 30.8 36.0 41.2 51.6
1.18 143 /16 -------- 2.68 3.95 5.15/10.3 115.6 20.8 26.0 31.3 36.5 41.8 52.3
1.19 141;'4 -------- 2.71 4.01 5.21 10.5 15.8 21.1 26.4 31.7 37.0 42.3 53.0
1
1.20 14 3Al -------- 2.75 4.06 5.28110.6 116.0 I 21.3 26.7 32.1 37.5 42.9 53.7
1.21 141h ------.- 2.78 4.11 5.34 10.8 16.2 21.6 27.1 32.5 38.0 43.5 54.4
1.22 14'i-18 -------- 2.82 4.16 5.41 10.9 I 16.4 21.9 27.4 33.0 38.5 44.1 55.2
1.23 14 3;'~ ---"'--- 2.86 4.22 5.48 11.0 116.6 22.2 27.8 33.4 39.0 44.6 55.9
1.24 14~8 _... _--- 2.89 4.27 5.55 11.2 16.8 22.5 28.1 33.8 39.5 45.2 56.6
1 1
-------- -------- 4.32 5.62 11.3 17.0 22.8 28.5 34.3 40.0 45.8 57.4
1.25 115
1.26 ISlA8 -------- .. ------ 4.37 5.69 11.5 17.2 23.0 28.9 34.7 40.5 46.4 58.1
4.43 5.76 11.6 17.4 23.3 29.2 35.1 41.1 47.0 58.9
~:;~ I ~;~
4 -------- --------
4.48 5.82 11.7 17.7 23.6 29.6 35.6 41.6 47.6 \59.6
1.29 1St;2
--------
.-------
--------
----_.-- 4.53 5.89 11.9 I 17.9 1

I
23.9 30.0 I 36.0 42.1
I
48.2 60.4
I
1

-60-
 TABLE 12-(Continued)

Upper head, Throat width

Ha

Inches inc~es inc~es inc~es f~ot

1 1 1
10
feet
Feet (ap-
prox_)
Flow in cubic feet per second

I I I I
I
I I
1.30 II 15'12 4.50 5.96\ 12.0 18 1 24 2 30.3 36.5 42.6 148.8161.1
12.2 1 18.3
. 1 24.5
.
1

1.31 15 3/4 4.64 6_03 30.7 36.9 43.1 49.4 61.9

1.32 1513/16 4.69 6.10 12.3 18.5 24.8 31.1 37-4 43.7150.0 62.7
1.33 15 15/16 4.75 6.18 12.4 18.8 25.1 31.4 37.8 44.2 50.6163-4
1.34 161/16 --------1 4.80 6.25 12.6 19.0 25.4 31.8 38.3 44.7 51.2 64.2
1 I I
1.35 163/16 I -------- 4.86 6.32 12.7 19.2 25.7 32.2 38.7 45.3 51.8 I 65.0
--------1
1.36
1.37
165/16
167/16
-------- -------- 4.92
4.97
6.39
6-46
12.9
13.0
1 19.4
19.6
26.0
26.3
32.6
33.0
39.2
39.7
45.8
46-4
I 52.5 65.7
53.1 66.5
-------- -------- I
1.38 169/16 -------. -------- 5.03 6.53 13.2 19.9 26.6 33.3 40.1 46.9 I 53.7 1 67.3
1.39 16 11/16 -------- -------- 5.08 60 13.3 20.1 26.9 33.7 40.6 47-4 54.3 68.1
6. 1
I 34.1 48.0
I I
1-40 1613/ 16 1 -------- -------- -------- 6.68 13.5 20.3 27.2 41.1
48.5
I 55.0 68.9
1.41 1615/16 -------- .------- -------- 6.75 13.6 20.6 27.5 34.5 41.5
49.1
I 55.6 69.7
1.42 17 1/16 -------- -------- -------. 6.82 13.8 20.8 27.8 34.9 42.0 I 56.2 70.5
1.43 17 3/16 I -------- -------- -------- 6.89 13_9 21.0 28.1 35.3 42.5 49.6 I 56.9 71.3
1.44 171/4 -------- -------- -------- 6.97 14.1 21.2 28.5 35.7 42.9 50.2 I 57.5 72.1
I I I
1-45 17 3/8 -------- -------- 7.04 14.2 21.3 28.8 36.1 43.4 50.8 58.1 72.9
1-46 17'12 ---~--- --------
-------1
-------- 7.12 14.4 21.7 29_1 36.5 43.9 51.3 58.8 73.7
1.47 170/8 .------- -------- 7.19 14.5 21.9 29.4 36.9 44-4 51.9 59.4 74.6
-------1 7.26 14.7 22.2 29.7 37.3 44_9 52.4 60.1 75-4
1.48 173/4 .----- -------- --------
1.49 17 7/8 34 14.9 22.4 30.0 37.7 45.3 53.0 60.7 76.2
I -------- -------- --------1
1.50 18 -------- -------- --------
I
7. 1
7.41 15.0
I 22.6 I
30.3
I 38_1 45.8 53.6
I
I 61.4 77.0
1.51 181/8 -------- -------- -------- 7-49 15.2 22.9 30.7 38.5 46.3 54.2 62.1 77.9
1.52 181/4 -------- -------- -------- 7_57 15.3 23.1 31.0 38.9 46.8 54.7 62.7 78.7
1.53 18"18 -------- -------- .-.----- 7.64 15.5 23.4 31.3 39.3 47.3 55.3 63.4 79_5
1.54 18'12 -------- -------- ------- 7.72 15.6 23.6 31.6 39.7 47.8 55.9 64.0 80.4
I I I 7.80 15.8 23.8 32.0 40_1 48.3 56.5 64.7 81.2
1.55 180/8 .------- -----.-- --------
1.56 18 3/4 -------. ----- -------- 7.87 15.9 24.1 32.3 40_5 48.8 57.1 65.4 82_1
1.57 1813/16 .------- -------- -------- 7.95 16.1 24.3 32.6 40.9 49.3 57.7 66.1 82.9
1.58 1815/16 -------- -------- -------- 8.02 16.3 24.6 32.9 41.4 49.8 58.2 66.7 83.8
1.59 19 1/16 -------- ___ A _ A .
-------- 8.10 16.4 24.8 33.3 41.8 50.3 58.8 67.4 84.6

1.60 19 3/16 ------- .------ --.----- 8.18 16.6 25.1 33.6 42.2 50_8 59.4 68.1 85.5
1.61 195/16 -------- ------- -------- 8.26 16.7 25.3 33.9 42_6 51.3 60.0 68.8 86.4
1.62 197/16 ------ -------- -------- 8.34 16.9 25.5 34.3 43.0 \ 51.8 60.6 69.5 87_2
1.63 19 9/16 -------- -------- -------- 8.42 17.1 25.8 34.6 43.4 52_3 61.2 70.2 88_1
1.64 19 11/16 -------- -------- -------- 8.49 17.2 26.0 34.9 43.9 52.8 61.8 70.9 89.0
1 I
1.65 19 13/16 -------- -------- -------- 8.57 17.4 26.3 35.3 44.3 53.3 62.4 71.6 I 89.9
1.66 1915/16 -------- .------- -------- 8.65 17.6 26_5 35_6 44.7 53.9 63.0 72.3 90.7
1.67 201/16 .----- -------- -------- 8.73 17.7 26.8 35.9 45.1 54.4 63.6 73_0 91.6
1.68 203/16 -------- .------ ____ A_A.
8.81 17.9 27.0 36.3 45_6 54.9 64.3 73.7 1 92.5
1.69 20'14 ______ " 8.89 18.0 27.3 36_6 46.0 55.4 64.9 74.4 I 93.4
____ A_A.
--------
I I I I

-61-
 TABLE 12-(Continued)

Upper head, Throat width

Ha

Inches
feet (ap-
prox.)
flow in cubic feet per second

I i I
1.70 20:Va 8.97 18.2 27.6 37.0 46.4 I 56.0 65.5 75.1 94.3
1.71 20'12 9.05 18.4 27.8 37.3 46.9 I 56.5 66.1 75.8 95.2
1.72 20% 9.13 18.5 28.1 37.7 47.3 157.0 66.7 76.5\96.1
1.73 20:V4 9.21 18.7 28.3 38.0 47.7 57.5 I 67.3 77.2 97.0
1.74 1207/a ········1 ....... \ 9.29\ 18.9 \ 28.6 138.3 48.2 \ 58.1 \ 68.0 I 77.9 I 97.9

1.75
1.76
21
211/a
9.38
9.46
19.0
19.2
28.8
29.1
38.7
39.0
48.61 58 .6
49.1 59.1
68.6
69.2
I
78. 7 98.8
79.4 99.7
1.77 211/4 9.54 19.4 29.3 39.4 49.5159.7 69.9 80.1 1100.6
1.78 213/a 9.62 19.6 29.6 39.7 49.9 60.2 70.5 80.8 101.5
1.79 211/2 9.70 19.7 29.9 40.1 50.4 60.7 71.1 81.6 102.4

1.80 21 5k
I
9.79119.9 30.1 40.5
i I
50.8161.3 71.8 82.3 1103.4
1.81 213,!, ········1
-------- 9.87 20.1 30.4 40.8 51.3 61.8 72.4 83.0 104.4
1.82 2113/16 9.95 20.2 30.7 41.2 51.7 62.4 73.0 83.8 1105.3
1.83 21 15/16 10.0 20.4 30.9 41.5 52.2 62.9 73.7 84.5 1106.2
1.84 22 1/16 ........ \ 10.1 20.6 31.2 41.9 52.6 \ 63.5 74.3 85.3 1107.1

1.85 \ 22 3/16 ------- 10.2 ! 20.8 I 31.5 42.2 53.1 64.0 75.0 86.0 1108.1
1.86 I 22 5/16 I ·······1 ········1 _.. _.·.1 10.3 I 29.9 I 31.7 I 42.6 53.6 I 64.6 I 75.6 86.8 1109.0
1.87 227/16 -------- 10.4 21.1 32.0 43.0 54.0 I 65.1 76.3 87.5 110 0
1.88 22 9/16 --------
........ \
-------- ....···1
--".---- 10.5 21.3 32.3 43.3 54.5 65.7 76.9 88.3
1 .
110.9
1.89 22 11/16 -------- 10.5 21.5 32.5 43.7 54.9 66.3 77.6 89.0 111.9
1
1.90 I
22 13/16 -------- .------- -------- 10.6 21.6 I 32.8 44.1 55.4 66.8 78.2 89.8 112.9
1.91 22 15/16 _____ "
-------- -------- 10.7 21.8 33.1 44.4 55.9 67.4 78.9 90.5 113.8
1.92 23 1/16 -------- -------- -------- 10.8 22.0 33.3 44.8 56.3 67.9 79.6 91.3 114.8
1.93 233/16 -------- "------- -------- 10.9 22.2 33.6 45.2 56.8 68.5 80.2 92.1 115.8
1.94 23 1/4 ------- -------- -------- 11.0 22.4 33.9 45.5 57.3 69.1 80.9 92.8 116.7
I I I I
1.95 23:Va -------- -------- -------- 11.1 22.5 34.1 45.9 57.7 69.6 81.6 I 93.6 117 7
1.96 23'12 -------- -------- __ -.0.-- 11.1 22.7 34.4 46.3 58.2 70.2 82.2 94.4 1118.7
.
82.9 I 95.1 119.7
1.97
1.98
23 5/a
23 3/4
--------
--".----
--------
--------
---.---- 11.2
-------- 11.3
22.9
23.1
34.7
35.0
46.6
47.0 I 58.7
59.1
70.8
71.4 83.6 95.9 120 6
1.99 23?1a -------- -------- .------- 11.4 23.2 35.3 47.4 59.6 71.9 84.3 96.7 1121.6
.
I
2.00 24 -------- -------- -------- 11.5 23.4 35.5 47.8 60.1 72.5 84.9 97.5 122 6
2.01 1 .
241fa -------- -------- -------- 11.6 23.6 35.8 48.1 60.6 73.1 85.6 98.3 123.6
2.02 241/4 .------- ____ yow.
-------- 11.7 23.8 36.1 48.5 61.0 73.7 86.3 99.1 124.6
2.03 24'% -------- -------. -------- 11.8 24.0 36.4 48.9 61.5 74.2 87.0 99.8 125.6
2.04 24'12 -------- -------- -------- 11.8 24.2 36.7 49.3 62.0 74.8 1 87.7 100.6 126.6

2.05 240/a -------- ------- -------- 11.9 24.3 36.9 49.7 62.5 75.4 88.4 10 127.6
2.06 24 3/4 -------- -------- ------- 12.0 24.5 37.2 50.1 63.0 76.0 89.1 1 1.4
102.2 128.6
2.07 2413/16 -------- -------- ------- 12.1 24.7 37.5 50.4 63.5 76.6 89.8 103.0 129.6
2.08 24 15/16 ____ woo.
-------- -------- 12.2 24.9 37.8 50.8 63.9 77.2 90.4 1
103 .8 130.6
2.09 25 1/16 -------- -------- -------- 12.3 25.1 38.1 51.2 64.4 71.8 91.1 104 6 131.6
I I I 1
1 .

-62-
 TABLE 12-(Continued)

Upper head, Throat width

Ha

Inches
Feet (ap·
prox.)
Flow in cubic feet per second

I 1 I 1 1

2.10 253/16 -------. -------- ········1 12.4 25.3 38.4 6 64.9 78.4 91.8 105.4 1132 .7
2.11 255/16 -------. -------- 12.5 25.5 38.6 /51.
52.0 1
65.4 79.0 92.5 106.2 133 7
1 .
2.12 25 7/16 -------. ----.--- -------- 12.6 25.6 38.9 52 4 65.9 79.6 93.3 107.0 134.7
2.13 25 9/16 ------- -------" 12.6 25.8 39.2 52.8
1 . 1
66.4 80.2 94.0 107 9
1108.7
.
i135 .7
2.14 I 25 11/16 -------- ---.---- -------- 12.7 26.0 39.5 53.2 66.9 80.8 94.7 1136.8

2.15 12.8 26.2

I 39.8 I
53.5 67.4 81.4 95.4
I I
1109 .5 1137 .8
25 13/161 ..··.... 1 -------- -------"
2.16 25 15/16 -------- -------- -------- 12.9 26.4 40.1 53.9 67.9 82.0 96.1 1110 . 3 1138 .8
2.17 26 1/16 -------- -------- 13.0 26.6 40.4 54.3 68.4 82.6 96.8 1111.1 139.9
....··1 68.9 83.2 97.5 111.9 140 9
2.18 263/16 -------- -------- ------." 13.1 26.8 40.7 54.7
1 .
2.19 261/4 1
-------- ------.- 13.2 27.0 41.0 55.1 69.4 83.8 98.2 1112 . 8 142.0
I 26 3/8 I I I
2.20 -------- -------- -------- 13.3 27.2 41.3 55.5 69.9 84.4 98.9 1113.61143.0
2.21 261f2 -------- -------- ------_. 13.4 27.3 41.5 55.9 70.4 85.0 99.7 114.4 1144.1
2.22 26 5/8 -.------ -------- -------- 13.5 27.5 41.8 56.3 70.9 85.6 100.0 1115 .3 1145 .1
2.23 26 3/. -------- ------.. --._---- 13.6 27.7 42.1 56.7 71.4 86.3 101.1 116 1 1 146 .2
2.24 261'8 -------- -------. -------- 13.7 27.9 42.4 57.1 71.9 . 1147 . 3
86.9 101.8 1116.9

2.25
2.26
27
271/8
....·..·1 -------- ------.- 13.7
-------- 13.8
28.1
28.3
42.7
43.0
57.5
57.9
72.4
72.9
87.5
88.1
102 6
1103.3
.
1,,,.,1,...,
118.6 1149.4
......·1 ---.----
2.27 271/. -.------ ---.---- -------- 13.9 28.5 43.3 58.3 73.5 88.7 104.0 119.5 1150.5
2.28 27 3/8 -------- -------- -------- 14.0 28.7 43.6 58.7 74.0 89.4 104.8 1120.3 151.5
2.29 271f2 -.------ ------- -------- 14.1 28.9 43.9 59.2 74.5 90.0 105.5 121.2 1152.6

14.2 29.1 44.2 59.6 75.0 90.6 106.2

I122 0 I
2.30 27 5/8 ,,-'--- -------- -------- 1 . 1153.7
2.31 27 3/. -------- -------- --~-----
14.3 29.3 44.5 60.0 75.5 91.2 107.0 122.9 1154.8
2.32 27 13/16 -------- ------- -------- 14.4 29.5 44.8 60.4 76.0 91.9 107.7 123.7 1155 . 8
2.33 27 15/16 -------- -------- -------- 14.5 29.7 45.1 60.8 76.6 92.5 108.5 124.6 156 9
29.9 45.4 61.2 77.1 93.1 109.2 125.4 1 .
158.0
2.34 281/16 -----~-- -------- ---'---- 14.6

30.1
1
45.7 61.6 77.6 93.8 110.0
I126.3 I159.1
2.35 283/16 -------- ---.---- -------- 14.7
2.36 285/16 ------_. ---_._-- -------- 14.8 30.3 46.0 62.0 78.1 94.4 110.7 127.2 160.2
2.37 28 7/16 -------- -------- ------'- 14.9 30.5 46.4 62.4 78.7 95.1 111.5 128.0 161.3
2.38 28 9/16 -------- -------- -------- 15.0 30.7 46.7 62.9 79.2 95.7 112.2 128.9 162.4
2.39 28 11/16 -------- -------- -------- 15.1 30.9 47.0 63.3 79.7 96.3 113.0 129.8 163 5
1 .
15.2 31.1 47.3
I
63.7 80.3 97.0 113.7
I130.7 164.6
2.40 28 13/16 --~----- ------- --------
2.41 28 15/16 -------- -------~ -------- 15.3 31.3 47.6 64.1 80.8 97.6 114.5 131.5 165.7
2.42 29 1/16 -------- ------- ---~----
15.4 31.5 47.9 64.5 81.3 98.3 115.3 132.4 166.8
2.43 293/16 -------- ----- .. - -------- 15.5 31.7 48.2 65.0 81.8 98.9 116.0 133.3 167.9
2.44 29 '/. -------- -------- 15.6 9 48.5 65.4 82.4 99.6 116.8 134.2 169.1
-~------
31. 1
I
2.45 29 3", ------_. -------- -------- 15.6 32.1 48.8 65.8 82.9 '100.2 117.6 135.1 1170.2
2.46 291f2 .------- -------- -------- 15.7 32.3 49.1 66.2 83.5 100.9 118.3 135.9 17
2.47 295/8 .------- -------- -------- 15.9 32.5 49.5 66.7 84.0 101.5 119.1 136.8 1172.4
1.3
2.48 29 3/. ------- -------- -------- 15.9 32.7 49.8 67.1 84.5 102.2 119.9 137.7 173.6
2.49 29 7/8 .------- -------- -------- 16.0 32.9 50.1 67.5 85.1 102.8 120.6 138.6 174 7
1 .
2.50 30 16.1 33.1
I
50.4 67.9
I
85.6 103.5 121.4 1139.5 /175.8
-------- ------ .. --------
I I I I I I

-63-
 3-INCH PARSHALL FLUME
DISCHARGE F"ORMULA; Q = 0.992 H~547

rI "1 _________ _ .,1

[
5!
-'o

1 ..
.'

.sCT ZERO or GAG["

L(v(L WITH CA(~T <

or rI..u .. t L ~:§~2Z::2,;~

, SECTION C-C
!-----'----
PLAN

------- ----,---

- 1
- ..r-:::-----_, :.
I

SIDE ELEVATION SEC1'ION B-B

HI .A.T" ~. ~ITC.'" ."'''11\.

NOT WON THAN to 1. Of' "H~
~C=~~~~::::==~-~l,LNf....~1I" _·LT'!.'J.~ s.-~. ~
! ';;r I
UPP[R n.oOR I THROAT i LOWER FLOOR I
1-1
.-. - - - i
1'- 6" - - -...If-O'_ S " - 4 - , ' - 0 · - ' - ;

Fig, 25. Plans for 3-inch Parshall flume,

Plans-Detail drawings showing all dimensions are given in figures 25

to 28, inclusive, for flumes of throat widths from 3 inches to 1 foot, These
drawings are for wooden flumes, but the same inside dimensions hold whether

-64-
 TABLE 13-Bills of material for 3-inch to l-foot wooden Parshall flumes.
No. No. No. No.
Item of 3-ineh of 6-ineh of 9-ineh of I-foot
Pes. Pes. Pes. Pes.
Upper side walls 2 1"xlOxl'6%" 4 1"xl0"x2'7/16" 2 2"xlO"x2'10%" 2 2"xl0"x4'6"
2 l"x 8xl'6%" 4 2"x 8"x2'10%" 4 2"x 8"x4'6"
Throat side walls 4 l"x 8"xO'6" 1 l"x 6"xl'0" 6 2"x 8"xl'0" 4 2"x 8"x2'O"
1 l"x 4"xO'6" 4 l"xlO"xl'O" 1 2"x 8J1 x l'OI1 3 2"xlO"x2'0"
Lower side walls 2 l"x 8"xl'01h" 2 1"xl0"x2'0l/2" 2 2"xl0"xl'61f2" 4 2"xlO"x3'0l/z"
4 l"x 6"xl'0%" 4 l"x 8"x2'0%" 4 2"x 8"xl'6%" 3 2"x 8"x3'Olh"
1 2"x 6"xl'6%"
Wall posts 6 2"x 4"x2'2" 2 2"x 4"x2'9" 4 2"x 4"xx3'0" 6 2"x 4"x3'0"
2 2IJ x 4"x2'4" 4 2"X 4"x2'4" 2 4"x 4'~x3'6" 2 4"x 4"x4'0"
2 2"x 411x2'7/1 2 4"x 4"x3'0 2 4"x 4"x3'0"
Cross ties 4 2"x 4"xl'1" 4 2"x 4"x2'2" 2 2"x 4"x3'0" 2 2"x 4"x4'0"
2 2"x 4"xl'6" 4 2"x 4"xl'4" 2 2"x 4"x2'3" 4 211X 4"x3'O"
en 2 2"x 4"xl'9" 4 2"x 4"xl'9" 4 2"x 4"x2'OIl
C.Il
I Stilling box
Sides 4 I n x 8"xl'9" 4 l"x 8"x2'3" 4 l"x 8"x3'0" 4 l"x 8"x3'0"
End 1 1"xl0"x2'0" 1 1"xlO"x2'4" 1 l"xlO"x3'1" 1 1"xl0"x3'1"
Bottom 1 2"xl0"xl'2" 1 2"xl0"xl'2" 1 2"xlO"xl'2" 1 2"xl0"xl'2"
Lid 1 1"xI2"xl'6" 1 1"x12"xl'6" 1 1"x12"xl'6" 1 l"xI2"xl'6"
Nailing stri 12 2 2"x 4"x2'0" 2 2f1x 4"x2'O" 2 2"x 4"x2'O" 2 2"x 4 x2'O"
11

Upper filoor 2 2"x 4"xl'6" 2 2"x 6"x2'7/ 16" 1 2"x 8"x2'10" 2 2"xI2"x4'5"
1 2"xl0"x2'10"
Throat floor 1 2"x 4I1XO'6 11 1 2"x 6"xl'0" 1 2"xl0"xl'0" 1 2"x12"x2'O"
Lower floor 2 2"x 4"xl'0" 2 211X 7"x2'O" 1 211X 4"xl'6" 1 2"x 6"x3'0"
1 2"xl0"xl'6" 1 2"x12I1x3'O"
Bolts 20 1f4"x3" 20 1f4"x3" 20 %"x4" 20 3/S" X4"
Cut washer 20 20 20 20
Nails 3 Ibs.-16d 4 Ibs.-16d 7 Ibs.-16d 8 Ibs.-16d
3 Ibs.-lOd 4 Ibs.-lOd 2 Ibs.-l0d 2 Ibs.-lOd
Total board feet of lumber 44 65 117 189
the flume is made from lumber, concrete, or metal. Table 13 gives detailed
bills of material for 3-inch, 6-inch, 9-inch, and I-foot wooden Parshall flumes,
respectively, together with the total number of board feet required for each.

6-INCH PARSHALL FLUME

J-'"
-:2 H+------2

SECTION C-C
t<---------~'-o"---------_.j
PLAN

1 r B~ n r .-
~I+II----I
,, '

- .. - .-- ....... t--~it_-__+ f------41

- .. - .- ... --- .. - :+1----1

:'f
.!-
,
:'
-ty==- .:' :F·-::::··'- ...... t--:: _ -.- ,,+6"- --
LB~_" • ____ • __ ~
LI
..s.....;:,"'"'flt.:_1L:,.::..:~:.:.:.=.:.:---Tt

SIDE ELEVATION SECTION B-B

Fig. 26. Plans for 6-inch Parshall flume.

Forms-Frequently irrigation companies wish to install a number of con-

crete Parshall flumes of a particular size. If the number to be installed is
large, it is desirable to have one or more portable forms for placing the con-
crete rather than consh'ucting forms in place each time. Many soil conserva-
tion districts have such forms that can be borrowed or rented by individuals

-66-
 9-INCH PARSHALL FLUME

~I·
- - 2'-10 ----1-1"-1--
Q

SECTION C-C

PLAN

1_..j.,LI_~I--fl----~nf.L._-.l../fT
j..Lnl.-U-
, ,
-I-- - H-----I-; j + - - .;.I----~-
, ' 1
, :
-1-- - t~--__I·,, I, I - - - -,.f---~
,
'L
-l;rtr,1'+------ ~91
0-.1. 1

:tf:l~ _--'C_

SIDE ELEVATION SECTION B-B

Fig, 27. Plans for 9-inch Parshall flume.

-67-

~-
 l-FOOT PARSHALL FLUME

~1"FlI~ "'I'o~

l
r
~
.1 -3'-0· I
-gf+t---
-.:, ~ ~
I
I

I
~
SECTION C-C
I·
PLAN

n r~jo-:_ _-t_j.l-n____~I
--

SIDE ELEVATION SECTION B-B

d'lIGINAL. ,",IGoH ""'Ar(1; 1..1~( ON OileH '"N,.,

. .. ............--... .- --,-
- r LOW __ WOT YORt T"AN 10 PICA C[NT 0"*101"'·
~J:::.==:::::::::====:::::::::::~~"'~""-::- J.wt.l.Ct'=1:J11.Il1.. [J..Q.Pa .cF"..cU-lIdc.J: _ .....L.

UPPER rLOOR
'00 LOWER
o---=l
~~RI
~_ _ _ ':4j'_ _~-+-___
0 I --+--3 C

Fig. 28. Plans for I-foot Parshall flume.

or companies. The plans and specifications for the forms of a 6-inch concrete
Parshall flume are shown in Figure 29. These forms are made from 12-gauge
galvanized iron and reinforced with angles. There are a total of seven
separate pieces: two templates for placing the floor, two pieces for the out-
side walls, and three separate pieces for the inside walls. No provision is
made for the stilling well, which may be poured separately.

-68-
 PORTABLE STEEL FORM FOR 6-INCH
CONCRETE PARSHALL FLUME
TEMPLATES FOR FLOOR
RIGHT AND LEFT SIDES

r~~:'.
.
,;. '1~
---- -. -,
L ____~ ____
~ I~-O"--l
-
PLAN <LEFT TEMPLATE SHOWN ON...YJ

rr-
__ .. _-_-_-.-
-_-_~·_~ __-_-_-_-_-._-
__-_-_- __----r=--... -- ...----.- - - - - - - - - - - . - - . - - :T
__-.-_-
- -:.. -~ , S"~K.1NG EDGE fOft ..,

...... CQNCJ\£1L "-OOR L~~ _ __ _ J.

.,
1 2'-0''-.
---- f SI.OT5 12' ON CENTERS FOR EXTENSION Of"
z'-o"
REINFORCE~NT--------

ELEVATION

OUTSIDE FORMS FOR WALLS

TWO SECTIONS RIGHT AND LEFT SIDES

PlAN (RIGHT SIDE SHOWN O!'-LY)

1. --t----
0

i-o"-- I~O" ---t----- 2'-0"

~
,

~ fx fxf A~S
:1....

;~
•.!.

1 ___ y
'.t
i .
f-l- _________ _ _::----. - r
I f HOI.E FOR STlLUNC WELL ----
----_ '
l' C.Ol'<r~--
f\.QQ,,_I.I....I;---··-
-
. I
i
• \t
--- . .d=-- - ...1

ELEVATION Sheet 1 of 2 Sheets

Fig. 29. Forms for 6-inch concrete Parshall flume.

-69-
 PARSHALL FLUME FORMS-(Continued)

INSIDE FORM FOR INSIDE FORM FOR

UPPER CONVERGING SECTION MIDDLE SECTION

~-.- ,'. 0'-- >1

PLAN I r;--- -,
~:. . . . - -.
, -
',I ,I
, I
I , "

~! ::

EL,EVATION FRONT

INSIDE FORM FOR

LOWER DIVERGING SECTION

-. --. -' ,-. ,._ . ):" 1

~------~ -- ----1, USE:
SPECIFICATIONS

ft;;; - -,;-
·:~"··
'
'2 GAGE GALVANIZED IRON PLATE
,---------------- - ---- , lfx I!"X f
ANGLES ON ALL
,, " EDGE!; WHERE BOLTING TOGETHER
,
I
,'"
C

OF FORM IS NECESSARY
f X f)( r FOR ALL OTHERS

.:
"
',)1',!, ,r RIVETS
~ ..:::~~-:.::-·-·;:-·::····l , r BOLTS FOR JOINING fORMS

I _~. . ·I~
FRONT

PLAN SHEET 2 OF 2 SHEETS

Fig. 29. Forms for 6-inch concrete Parshall flume. (Cont.)

-70-
 The two templates for the floor are placed to elevation with the reinforc-
ing bars in place for the floor and protruding through the slots of the tem-
plates on either side. The floor is then poured, using the templates as a
guide to strike off the concrete to the proper shape. \Vhile the concrete is
still partially green the templates are removed and the reinforcing bars bent
up through the concrete for reinforcing the walls. The remaining parts of
the form are then put in place and securely bolted together. A pipe is placed
in to lead to the stilling well and the walls poured.

DiVIDERS
Many irrigation companies in Utah divide their streams according to the
number of shares of stock owned by individuals or groups of individuals. On
the smaller streams either a single company owns the entire flow or it is
divided among two or three companies, each company owning a share of
the total stream. The users are not so much interested in the measurement
of the water as they are in the division of the stream. For example, one com-
pany may be entitled to 5/12 of the stream and another company to 7/12
of the stream. The two companies own all the water in the stream. They
are not particularly interested in the quantity, but they are interested in the
division. Sometimes a divsion must be made where it is impractical to make
a measurement.
If even an approximate division is made, a few principles must be ob-
served. The water must approach the divider in parallel paths; there must

f------L

PLAN

~~~==~==~~=£<=C=r,~/O~W~A~L~D~W.~U~C~H,~~~N.=W.=~=L==~~====~
Fig. 30. Typical divider used on streams carrying considerable sand and gravel.

-71-
be no cross currents. To secme this condition, the divider box must be placed
at the lower end of a long flume or of a sh·aight open channel. The floor of
the channel immediately above the divider should be level transversely. If
the water is reasonably free from silt it is desirable to have the water ap-
proach the divider at a low velocity. For streams carrying considerable silt
and gravel there should be no obstruction in the channel in the form of bulk-
head, and the velocity with which the water enters should be maintained
through the structure. Figure 30 shows a form of divider used on mountain
streams which carry considerable sand and gravel. It is very important that
these structures have a long straight channel of approach and that the floor
be level transversely. Any gravel or debris allowed to collect in the channel
of approach causes cross currents and interferes with proper division.
The How over a weir can be easily divided by placing a sharp-edged
partition below the weir to divide the stream as it falls over the crest. The
crest of this partition should be placed a sufficient distance below the weir
crest to permit a free circulation of air between the divider and the sheet of
water falling over the weir.
The discharge over a weir is not exactly proportional to the length of the
crest; however, the error in considering it so is slight. The trapezoidal weir
is the most desirable form if it is to be used as a divider. The How over this
weir is very nearly proportional to length of the crest. If it is desired to
divide the stream into two parts, one taking five-sixths and the other one-
sixth of the How, the divider should be placed one-sixth of the distance from
the end of the weir. Figure 31 shows a trapezoidal weir divider fixed to
divide a stream into three parts.
An appropriate measuring device should be installed in all streams below
a divider to insure proper division.

Fig. 31. Divider below trapezoidal weir.

-72-
 MEASURING DISCHARGE FROM PIPES
Frequently the discharge from an artesian well or from a pumping plant
is desired when there are no facilities for making a measurement by methods
in common use. For such measurements coordinate methods D of me~suring
pipe flow have been suggested. However, these methods have limited ac-
curacy and should not be used where accuracy is essential or where somc
other method can be conveniently used.
These methods consist of measuring the coordinates of a point in the
jet issuing from the end of the pipe; the chief difficulty is in accurately meas-
uring the coordinates. The flow from pipes may be measured whether the
pipe is discharging vertically upward, horizontally, or at some angle with the
horizontal. Usually discharge pipes from artesian wells or pumping plants are

Fig. 32. (a) Drawing showing dimensions nec9ssary in making a measurement of

the Row from vertical pipes.

DChristiansen, J. K, "Coordinate Methods of Measuring Pipe Flow." Mimeographecl

report of Division of Irrigation Investigations and Practice, University of California.

-73-
 80
l"'\

80
""
0
0
V\
.....

0
0
0
.....
0
0
co

0
Q3
c $
{f,
0
",:
..-'
0 E1
~
....
Q)
P-
o
0
l"'\ c:"
.....0
.....
C
0
'"
bD

"" .,
I

0 0
~
V\
.....

0
c
.....
c
co

Q3
0
V\

0
~

L-~~~~__~~__~____~~~~~~~~~~~~-L~g
o
l"'\
V\
""
0
N
""
~
.....

Fig. 33. Discharge curves for measurement of How from vertical pipes. Based on
data from experiments of Lawrence and Braunworth. Am. Soc., C. E.
Trans. (57) 1906.

-74-
 either vertical or horizontal and therefore only these two cases will be dis-
cussed here.
Vertical Pipes. Lawrence and Braunworth lO conducted an extensive set
of experiments to determine the flow from vertical pipes. They found that
when the height of the jet exceeds 1.4 D, as determined by sighting over the
jet to obtain the maximum rise, the flow can be expressed by the empirical
equation:
G.P.M. = 5.01 D1.99 HD.53
When the height of the jet is less than 0.37 D, the flow is similar to that
over a weir and can be expressed by the equation:
G.P.M. = 6.17 D1.25 H1.35

in which G.P.M. is flow in gallons per minute; D is the diameter of the pipe
in inches; and H is the height of the' jet in inches.
For jet heights between 0.37 D and 1.4 D the flow is somewhat less
than that given by either of these equations.
Figure 33 shows the flow in gallons per minute for pipe and casing
2 to 12 inches in diameter, for jet heights, H, from IJf to 60 inches. This
diagram was prepared from Lawrence and Braunworth's data, using the
actual inside diameter of standard pipe and casing as given in pipe hand-
books.
Horizontal Pipes. For pipes discharging horizontally, it is necessary to
measure both a horizontal and a vertical distance from some point on the
end of the pipe to a similar point in the jet. These horizontal and vertical
distances are called the X and Y ordinates, respectively. In the method
described by Slichter, the ordinates are measured from the center of the
end of the pipe to the center of the jet, as shown in Figure 34. The expression
for the flow from completely filled pipes is derived in the following manner:
The distance Y that a particle falls in time, t, after issuing from the end of
a horizontal pipe is
Y = g t2
2
and the horizontal distance X it travels is
X = V t where V is the
initial horizontal velocity. Combining these equations by eliminating t and
solving for V, we obtain:
V = Xv g
V2 Y
from which we obtain the expression for the flow in cubic feet per second,
all dimensions being in feet:
lOLawrence, F. E., and P. L. Braunworth. "Fountain Flow of Water in Vertical
Pipes." American Society of Civil Engineers, Trans. No. 57, p. 265-306. 1906.

-7.5-

b
 Q C A X yg
y2Y
It is interesting to note that this expression also holds for pipes discharging
at an angle with the horizontal when the X ordinate is measured pamllel with
the axis of the pipe and the Y ordinate is meas1lred vertically.
For Row in gallons per minute, with the ordinates and pipe diameter
in inches, the expression is:

G 2.84 C D~ X
yY
For any given pipe diameter and given value of Y, thc flow is directly pro-
portional to the Y ordinate.
The flow from pipes ranging from 2 to 8 inches in diameter and values
of Y of 12 and 24 inches, respectively, is given in Figure 35. Since experi-
mental data are lacking, a value of C = 1.0 was used in computations for
these diagrams.
The Row from partially filled horizontal pipes can be estimated by mul-
tiplying the flow obtained from the diagram by the percentage of the area
of the pipe that is filled at the end of the pipe. The coordinates should be
measured from the approximate center of the jet at the end of the pipe instead
of from the center of the end of the pipe. The Purdue method described

--
below is generally more accurate, especially for partially filled pipes.

-- -
1- t--

________ 1____
D
-
-----
-----
-----....
y

x-------+i
Fig. 34. Drawing showing dimensions necessary in making a measurement of the
flow from horizontal pipes.

-76-
 FIG 35

7 10 15 20 30 40 50 70 100 150 200 300 400 500 700 1000 1500

DISCHARGE IN GALLONS PER MINUTE

Fig. 35. Discharge curves for How from horizontal pipes.

 Purdue Method for Horizontal Pipes. Another coordinate method of
measuring pipe flow has been developed at Purdue University.H It consists
of measuring the coordinates of the upper surface of the jet as shown in
Figure 36. For pipes flowing less than 0.8 full at the end, the vertical dis-
tance Y can be measured at the end of the pipe where X = O. The flow
from pipes ranging from 2 to 6 inches in diameter is given in Figure 37.
These diagrams were prepared from data taken from Purdue. Engineering
Experiment Station Bulletin No. 32, and are based on tests on standard pipe
sizes only. The curves for the casing have been drawn in by interpolation.

For accurate results, the pipe must be level and of sufficient length so
that the water is flawing fairly smoothly when it issues from the pipe. If
the pipe slopes upward, the measurements will be too high and if it slopes
downward, they will be too low. The top of the jet is not sharply defined and
it is difficult to make an exact measurement of the distance Y.

x
iy

Fig. 36. Purdue method of measuring pipe flow.

llGreve, F. W. Measurement of pipe flow by the coordinate method. Purdue En-

gineering Exp. Sta. Bul. 32. 1928.

-78-
 8
N

V
vv ... 1-"
...... """ ..... f..-'
vv ~
1-- .........
80 v ~ 'v ,; V §
..... I..... -:7 ri ....... ~' /v ; ' ri
...... I ~~ V /" V V 1/
V ....~
8 ~
v ......... ;
/
a::>
V VfJ' I--"
..... . / ........ ;:;;;-:
V
V
...... f-'" 1--'" § V
""" ...... ~'<lY §
V V .r:.:~ V ~f..- b.6~ ~~ ~l
~.

....... _sc f'/ ... ..... 8

_," U\
" -:,...... fJI~
8
U\

....- ...... :"'. ~ '-,# ~-;;;; 0

0
v ~~ 8
..... ;'t ...... •i'.'
"""
.:1
.s ...-:~ ~ ......... .::13
.........
...... ~ ,<;;0
~:;;;;-
...... 0 ...."ec ~' I-- ....... V "c
g ~fI
...... --: ...... c~
/ .............

'"
OJ
0-
v ... 1--'
:,...
'"
8-
./ ;"1---
V ~ """
........... i-""V
S(\Irig
Ol
...... ...... 8 c L """
....... 0
..........
'~

'" ri
..... .. v ri
.......
.........
"
co V V ~
0
U\
.....
""I .........
-li?-.
V ...... V I--"
V •
ri
V
V i< '}.' vi-'
VV
0

VV
0

V ~ t;:!
~" 0
0 V 0
0
ri ri

./
0
g
V ..... a::>

.......... f-'"
.55 .55
-
~
0
U\ Q>
-Ii?-
g 0
g 0
.:1 .::t
ri
.
..:
0
""
ri
g
..:

o
N

Fig. 37. Flow from horizontal pipes by Purdue coordinate method.

-79-
 - ..
--- -.......
4 -I-- r-
....
-- - - - 4' I- r-- . . . ........... ~
3
CEl,
' Ih -..;:. -'''''
~q ....... "'-
11 n·· ..........
"~
-- ---- --
II>
>'.!j .<: f- ~~ ~ ...... "-

'" "
cr.' oM "c 2
..... ~ cj, I'-... " 6',
W
:-t ><
I

- .............
.......... '" ""'t "-
'\
s,\
\
\. \
\
>'.!j

~
0' II>
u
C
r-- r--
-......
........
' ..... .J "
.....
........

, "- ", \
\.
\ -'\ 1'
\
\
..,.,
..,
0
~
....'" 1 ~ \ \ \~ \ ~ ' \
0
:3
:0"
p

X =o i c ~s \
, \
\
~
\ \
\
\
\
\
\

'"'
N' 3/4
0
;;. \ 1\ \
e.. 5 6 7 8 9 10 15 ZO 30 40 50 60 80 100 150 200 300 I~oo 500
't:I
CfJ
0 >5' Flow - gallons per minute
[ '"
on
cr'
5
\. I'\. '\."', \
'<: \. \.'" I\. 1\ \
"

4 I\. [,
>-tI
r:: \ ~ \ ... \ \ \
'r::"'
::>..

'" .<:
OJ
II>
3
1\
I',

,
1'\
I\,
~~\ ,0
~. ~c'"
1\, :\
\.
" 1\
"
0
0 ....c" "', \. ;S-~ '~9- \
'"'
::>.. I \ 'S ~ \"', \ \
S· >< 2 \. Po; \ 9- ~. \ a:.
~
'"
S II>
\
'. \
\ \
''- I'\<t.\
\<;
\
\
\
\ \
'...:0"" "c
0
j
.,
....
X 6 in ~h B \ 1\ ~\ \ l\
p..
\ \l \ ,
" \ \
~
\
1
20 )0 LO 50 60 80 100 150 200 300' Loo 500 600 500 1000 2000
Flow - gallons per minute
 PUBLICATIONS OF THE ENGINEERING EXPERIMENT
STATION
UTAH STATE AGRICULTURAL COLLEGE

1. Design of Drainage Wells

By Willard Gardner and Orson W. Israelsen.
December, 1940.

2. Water Measurement
By Wayne D. Criddle and Eldon M. Stock
June, 1941. (Out of print-Superseded by Bulletin No.5)

3. Safety and Regulation of Electric Fence Controllers for Utah

By Arthur C. Jacquot
June, 1942.

4. Automobile Speed Economy

By Harold S. Carter
June, 1942.

5. Measurement of Irrigation Water

By Eldon M. Stock
June, 1955.

Utah State Agricultural College Extension Service, Carl Frishknecht, Director Co-
operative Extension 'work in Agriculture and Horne Economics, Utah State Agricul-
tural College and the U. S. Department of Agriculture Cooperating. Distributed in
furtherance of the Acts of Congress of May 8 and June 30, 1914.
6-55-5M-ES