UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Water-Supply Paper 868-B

INVESTIGATIONS OF METHODS

AND EQUIPMENT USED IN

STREAM GAGING

PART 2. INTAKES FOR GAGE WELLS

BY

C. H. PIERCE

Prepared in collaboration with the

HYDRAULIC LABORATORY COMMITTEE

OF THE GEOLOGICAL SURVEY

LASLEY LEE, C. H. PIERCE, and O. W. HARTWELL, members

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1941

For sale by the Superintendent of Documents, Washington, D. C. ....... Price 15 cents

CONTENTS

Abstract. _ _______________-_______--_-__-__--_----------------___-_ 37

Introduction.________________________-___-____-_____-_-------_---_ 37

Administration and personnel.__________-__-_-__-__-_--_--_---__-_-_ 38

Cooperation and acknowledgments...-.----...___________-_--_--_-___ 39

Purpose and scope of the investigation,-______--_-__-_--____---___-__ 39

Intake devices selected for laboratory tests_________._-_-_----_-______ 39

Standard pipe fittings attached to end of intake pipe______________ 40

Standard pipe without fittings__--______-__-_--_---_-_-_----_--_- 40

Other devices_________________________________________________ 41

Methods of tests._____________________________-__-__-_-___-----_-_ 42

Laboratory equipment for tests of }£-scale models _____________________ 43

The A models____________-__--___--_---_____----___-__--_---__-.-- 44,

Full-size models___________________________________________________ 54

Apparatus used in tests of the full-size models.____-_____-_--_-_-_ 54

Distribution of velocity in the 3.0-foot flume______________________ 55-

Models selected for tests_____________---__-____-_-_____------_-_ 56

Tests.___--_--_--_------__-------_------------_---------_---_ 58

Collection of debris on intake._____-_______-____________-___-___-_. 66

Removal of silt by flushing.________________________________________ 66

Flushing apparatus____________________________________________ 67

Tests.____-------_------_--------_----__--_---_-----_-----___ 67

Results of the investigation.________________________________________ 68

Recommendations for designs_--___--______________-____--________._ 69

Static tubes______-____-_-__----____-_-_______-____--______-___ 69

Baffles.___-__________--_-_---__--_-__-____-_-_--_-_____-_____ 73

Other devices____-_____-_--__.._--__-____-_.-_-__-_-_____-____- 75

ILLUSTRATIONS

Page

PLATE 28. A, Flume used in test of the A models; B, Model .gage well, 

mounting block, and support, with model A-39 in position 

for test-_-_--__---_--___--___-______-_________________ 44

29. A, Draw-down in manometer wells under the point gages in 

test of model A-39; B, Tests of model A-79 under a velocity 

of 2.8 feet per second-_________________________________ 45

30. A, Outlet of 3-foot flume; B, Piezometer gages and stilling

well for the 3-foot flume______________________________ 68

31. A, Eiseniohr intake box; B, Kinnison intake box_ ___________ 69

FIGURE 4. Distribution of velocity in the 3-foot flume for a velocity of 2.8

feet per second at the intake.____________________________ 56

5. Designs of static tubes for use with 2-inch, 2^-inch, 3-inch,

and 4-inch intake pipes.________________________________ 70

6. Static-tube connection to intake pipe of gage well at streamflow measurement station provided with artificial control. _ _ _ 72

7. Design of Ash baffles for intake pipes of various sizes. _______ 73

8. Design of Twitchell baffles for intake pipes of various sizes._. 73

9. Design of Eiseniohr intake box__ _ _________________________ 74

in
IV CONTENTS

TABLES

Page 

TABLE 1. Intake devices selected for laboratory tests______---___-____ 40

2. Dimensions of standard sizes of pipe..______-_---___--_-___ 45

3. Dimensions of A models. __-_-_-_._-_------_-__---_--_-__- 45

4. Results of tests of A models under a velocity of 2.8 feet per

second. ______________________________________________ 47

5. Tests of selected A models under various velocities._________ 50

6. Full-size models selected for tests-----__--_-_--_---_------- 56

7. Tests of full-size models of 3-inch intake devices.___________ 60

8. Comparison of tests of full-size models of devices for use with

various sizes of pipes at a velocity of 2.8 feet per second. __ 62

9. Tests of Twitchell and Ash baffles of various lengths with different sizes of pipes---__--_-_------_---_-_-_----------- 62

10. Effects of collection of debris on intake ____________________ 66

11. Flushing tests of intake devices for 3-inch pipe__________--_- 6?
INVESTIGATIONS OF METHODS AND EQUIPMENT 

USED IN STEEAM GAGING

PART 2. INTAKES FOR GAGE WELLS

By C. H. PIERCE

ABSTRACT

Various devices attached to the ends of intake pipes to gage wells have been 

used by engineers of the Geological Survey in attempts to eliminate the "drawdown," or difference in the heights of water in the well and in the river at stations 

for the measurement of stream flow. About 90 different devices and arrangements of intakes were tested at the National Hydraulic Laboratory in order to 

obtain definite information regarding the performance of the various devices 

and their effectiveness in eliminating draw-down.

Preliminary tests were made of }£-scale models, an intake pipe 3 inches in 

diameter being taken as the basic size, with water flowing at 2.8 feet per second 

at the intake. Models that gave good results in the prelininary tests were selected 

for additional tests at full size. The models were tested for different positions 

corresponding to angularity of flow of the water passing the intake as well as for 

the normal position of intake perpendicular to the vertical plane in the direction 

of flow. The results of the tests of the }£-sca)e models and the full-size models 

are given in the tables.

As a result of the tests, several different devices were selected by the laboratory 

committee of the Geological Survey for recommendation to the district engineers 

of the Survey as being effective in eliminating draw-down at stations for the measurement of stream flow. Designs for use in constructing the devices are shown 

in the illustrations.

INTRODUCTION

The general use of water-stage recorders in obtaining records of 

stream flow has tended to the development of certain types of structures specially adapted to the purpose of providing shelter for the 

recording instruments and furnishing the necessary facilities for their 

operation. The instruments are installed over stilling wells, which 

are designed to eliminate the dynamic disturbances, such as the effects 

of wave action and pulsations, commonly found in natural streams, and 

to maintain a height of water that will be the same as the static head 

of the water in the stream channel or have a direct relation to it. 

If the stilling well is constructed in the bank of the river for protection 

against damage by floods or by freezing, a connection between the

37
38 METHODS AND EQUIPMENT USED IN STREAM GAGING

water in the river and the water in the well is made by means of an 

intake pipe. These intake pipes may be from 2 to 4 inches in diameter 

and of various lengths depending upon the distance from the stilling 

well to the point in the river at which the height of the water surface 

is to be measured. Unless the stream end of the intake pipe is 

protected from the dynamic effects of the water flowing past it there 

may be a draw-down or a building up of the height of water in the 

well as compared with the height of water in the river channel at the 

end of the pipe. These differences in height have been found to be 

as much as 1 foot, and they vary not only for different stages but they 

may also vary for the same stage of the river. Stilling wells attached 

to bridge piers or abutments are generally provided with small openings whereby the water is admitted directly into the wells without the 

use of intake pipes. Under those circumstances the dynamic effects 

of the water may be even more pronounced than those experienced 

where the connection is made through intake pipes. Except in 

rivers where heavy silt loads make the use of intake pipes impracticable 

it is possible that intake connections to stilling wells on bridge piers 

and abutments might be made in a manner similar to that used with 

stilling wells in river banks.

Various devices attached to the ends of intake pipes have been used 

by engineers of the Geological Survey in attempts to eliminate the 

so-called "draw-down," or difference in the heights of the water in the 

well and in the river at stream-flow measurement stations, and in 

October 1936 a letter was sent to all the district engineers of the Survey 

requesting suggestions in regard to designs of intake devices to be 

used in a series of tests in order to obtain information as to the most 

satisfactory devices. A large number of suggestions were received 

in response to that letter, and arrangements were made with the 

National Bureau of Standards for the use of its laboratory facilities 

in making a series of comparative tests of the devices that had been 

suggested.

ADMINISTRATION AND PERSONNEL

The work in the laboratory and office incident to the preparation 

of this report was performed under the general administrative direction 

of N. C. Grover, chief hydraulic engineer, and C. G. Paulsen, acting 

chief hydraulic engineer after the retirement of Mr. Grover on 

January 31, 1939. Mr. Paulsen also administered the work as chief 

of the division of surface water.

The methods and procedures used in conducting the investigation 

were arranged by the hydraulic laboratory committee of the waterresources branch of the Geological Survey, consisting of Lasley Lee, 

C. H. Pierce, and O. W. Hartwell. H. C. Beckman and C. V. Youngquist became members of the committee after the death of Mr. Lee
INTAKES FOR GAGE WELLS 39

in November 1937. Laboratory tests of the ^-scale models were 

made by Messrs. Lee, Pierce, and Hartwell, assisted by W. S. Eisenlohr, Jr., and A. D. Ash. Tests of the full-size models were made by 

Mr. Eisenlohr. The analyses of the data and the recommendations 

based on the results of the tests were made by the laboratory committee assisted by Mr. Eisenlohr.

COOPERATION AND ACKNOWLEDGMENTS

The facilities of the National Hydraulic Laboratory were provided 

by the National Bureau of Standards. The laboratory staff under the 

direction of H. N. Eaton furnished advice and assistance in the conduct of the work, particularly in regard to details of laboratory 

procedure.

PURPOSE AND SCOPE OF THE INVESTIGATION

The investigation was arranged for the purpose of testing the various 

designs of intake devices that had been suggested by engineers of the 

Geological Survey as being helpful in eliminating the effects of drawdown in gage wells. Some forms of intakes were tested for the purpose of obtaining standards of comparison rather than because of 

the merits of the particular forms. Tests of the draw-down when 

using a straight pipe with the outer end square-cut and open to the 

action of the water were made for purposes of comparison. Most of 

the models tested were composed of standard pipe fittings or accessories that could readily be obtained or constructed in the field. 

A few models of more complicated design were constructed for purposes 

of tests.

The tests were made with water passing the intake at velocities of 

1.0, 2.0, 2.8, and 3.65 feet per second. The limitations of the water 

available for testing the full-size models in the large flume did not 

permit the use of higher velocities.

INTAKE DEVICES SELECTED FOR LABORATORY TESTS

The suggestions as to forms of intake devices received from the 

engineers of the Geological Survey were arranged for use in the series 

of tests, all the suggestions that were sufficiently specific and practicable for laboratory tests being included. Several other devices and 

arrangements of pipe fittings were selected by the laboratory committee, so that a total of about 90 different devices and arrangements 

were prepared for tests. The different devices and arrangements 

are listed below. 1 The dimensions given are those for use with an 

intake pipe 3 inches in diameter.

1 The serial numbers used in this list have been rearranged from those originally assigned to the various 

evices.
40 METHODS AND EQUIPMENT USED IN STREAM GAGING 

TABLE 1. Intake devices selected for laboratory tests

STANDARD PIPE FITTINGS ATTACHED TO END OP INTAKE PIPE

1. 90° elbow with open end pointing upstream.

2. Same as 1, except the open end pointing downstream.

3. Same as 1, except the open end pointing downward.

4. 45° elbow with open end pointing upstream.

5. Same as 4, except the open end pointing downstream.

6. Same as 4, except the open end pointing downward.

7. Tee, with run on intake pipe, the outlet pointing upstream.

8. Same as 7, except the outlet pointing downstream.

9. Same as 7, except the outlet pointing downward.

10. Same as 7, except the outer end of run plugged.

11. Same as 7, except the outer end of run plugged and the outlet pointing downstream.

12. Same as 7, except the outer end of run plugged and the outlet pointing downward.

13. Same as 7, except with a 12-inch nipple in outlet pointing upstream.

14. Same as 7, except with a 12-inch nipple in outlet pointing downstream.

15. Same as 7, except with a 12-inch nipple in outlet pointing downward.

16. Same as 7, except with a 12-inch capped nipple on the outer end of the run.

17. Same as 7, except with a 12-inch capped nipple on the outer end of the run 

and the outlet pointing downstream.

18. Same as 7, except with a 12-inch capped nipple on the outer end of the run 

and the outlet pointing downward.

19. A 4-inch to 3-inch reducing elbow with the 4-inch opening pointing downward.

20. A 3-inch to 2-inch reducing elbow with the 2-inch opening pointing downward.

21. A 4-inch to 3-inch reducing coupling with the 4-inch opening outward.

22. A 3-inch to 2-inch reducing coupling with the 2-inch opening outward.

23. A four-way cross in horizontal position.

24. Same as 23, except the downstream opening plugged.

25. Same as 23, except the upstream opening plugged.

26. Same as 23, except the streamward opening plugged.

27. Same as 23, except the downstream and streamward openings plugged.

28. Same as 23, except the upstream and streamward openings plugged.

29. Same as 23, except with a 12-inch nipple in the streamward opening.

30. Same as 23, except with a 12-inch capped nipple in the streamward opening.

31. Same as 23, except with a 12-inch open nipple in the streamward opening, the 

downstream outlet plugged.

32. Same as 23, except with a 12-inch open nipple in the streamward opening, the 

upstream outlet plugged.

33. Same as 23, except with a 12-inch capped nipple in the streamward opening, 

the downstream outlet plugged.

34. Same as 23, except with a 12-inch capped nipple in the streamward opening, 

the upstream outlet plugged.

STANDAED PIPE WITHOUT FITTINGS

35. 1-inch pipe with end cut square.

36. 1^-inch pipe with end cut square.

37. 2-inch pipe with end cut square.

38. 2^-ineh pipe with end cut square.

39. 3-inch pipe with end cut square.

40. 4-inch pipe with end cut square.

41. 6-inch pipe with end cut square.
INTAKES FOR GAGE WELLS 41

42. 3-inch pipe with end cut at an angle of 10°, and placed so that opening faced 

10° upstream.

43. Same as 42, except with angle of 20°.

44. Same as 42, except with angle of 30°.

45. Same as 42, except with angle of 45°.

OTHER DEVICES

46. Kinnison intake box. A short airplane wing section set at a 6° negative 

angle of attack with the intake on the under side at the point of zero pressure.

47. Circular plate, 6 inches in diameter, with a 3-inch opening in center of plate.

48. Same as 47, except 12 inches in diameter.

49. Same as 47, except 18 inches in diameter.

50. Rectangular plate, 12 by 24 inches, with longer dimension horizontal, 3-inch 

intake at center.

51. Same as 50, except intake 6 inches downstream from center of plate.

52. Same as 51, except intake 6 inches upstream from center of plate.

53. Eisenlohr intake box. A casting resembling a 3-inch pipe compressed to a 

stream line shape with a J^-inch by 15-inch intake slot on under side.

54. Palm funnel. A truncated right circular cone; large end 12 inches in diameter, 

pointing outward. Elements of cone form an angle of 45° with common 

axis of cone and pipe.

55. Sawyer sieve. A 3-inch pipe with end cut square; four rings of four holes 

% inch in diameter; rings spaced 3 inches apart; holes to be as far from the 

open end of the pipe as practicable.

56. Concrete pier, 12 inches high and 24 inches long; intake near top at center of 

pier.

57. Same as 56, except with the top of the pier beveled downward at the upstream 

and downstream ends.

58. Standard 3-inch tee with outlet on the pipe; flow through the run.

59. Same as 58, except with a 12-inch nipple in each run.

60. Same as 58, except with a 12-inch nipple in the downstream run.

61. Same as 58, except with a 12-inch nipple in the upstream run.

62. Same as 58, with threads removed from the run.

63. Handrail tee with outlet on the pipe; flow through the run; threads removed 

from the run.

64. Same as 58, except with the run in a vertical position.

65. Long static tube of 3-inch pipe with cap on upstream end and connected to 

intake pipe by elbow at downstream end. Two rows of %-inch holes 

arranged with 8 holes each on top and bottom, holes beginning 3 pipe 

diameters from upstream end and ending 3 pipe diameters above downstream end. Tube pointing upstream.

66. Hanlon funnel. A cylinder 9 inches in diameter and 5J^ inches long with a 

conical section on downstream end 4 inches long with downstream opening 

6 inches in diameter; made of sheet metal. Side of cylinder attached to 

the intake pipe.

67. Twitchell baffle. A horizontal and a vertical vane of J4-incb sheet metal 

inserted in end of pipe, protruding 6 inches. Replaced by No. 72.

68. Same as 67 except vanes turned 45° from the vertical.

69. Prior intake. Two intake pipes with the intake on one pipe turned upstream 

and the intake on the other pipe turned downstream.

70. Canfield baffle. A flat plate 8 inches square, normal to current, held in 

position 3 inches upstream from end of pipe.

309968 41 2
42 METHODS AND EQUIPMENT USED IN STREAM GAGING

71. Same as 70, except with the plate held in position on the downstream side of 

pipe.

72. Same as 67, except the vanes adjustable to protrude different distances from 

the end of the pipe.

73. Same as 65, except pointing downstream.

74. Ash baffle. Same as 72 without the horizontal vane.

75. Cast-iron strainer, Walworth catalog No. 88, figure 2270.

76. Same as 75, except pointing downstream.

77. Curtis sleeve. A 12-inch cylinder, 18 inches long and concentric with the 

intake pipe, with the end of the pipe at the center of the cylinder.

78. Twitchell sleeve. A sleeve 12 inches long concentric with the intake pipe, 

the end of the pipe at center of the sleeve. The sleeve 6 inches in diameter 

where it projects beyond the pipe, increasing to 7.4 inches in diameter 

at the end of the sleeve that encircles the pipe.

79. Short static tube of 3-inch pipe 14 inches long; end of tube closed by a plugged 

coupling; downstream end connected to pipe by an elbow. Two rows of 

eight holes, one row on top and one row on bottom of tube. Holes % inch 

in diameter and spaced 1}£ inches. Tube pointed upstream.

80. Same as 79, except normal to flow.

81. Same as 79, except elbow replaced by a standard tee with outlet on pipe and 

capped nipple in downstream run.

82. Same as 81, except nipple inserted between the static tube and the tee, with a 

vertical support to bed of stream at the downstream end of the static tube.

83. Same as 79, except tube pointing downstream.

84. Same as 81, except tube pointing downstream.

85. Rectangular plate 12 inches wide by 8 feet long; intake at center of plate.

86. Same as 85, except plate 6 feet long.

87. Same as 85, except plate 4 feet long.

88. Rectangular plate, 24 inches long, extending from 6 inches above the intake 

to the bed of the stream.

89. Static tube Q% inches long, with four rings of %-inch holes, rings spaced 1)$ 

inches apart, four holes in each ring. Holes staggered in alternate rings. 

Tube pointing downstream.

90. Static tube 18 inches long, with five rings of %-inch holes, rings spaced \% 

inches apart, two holes in each ring. Holes staggered in alternate rings. 

Tube pointing downstream.

91. Static tube, 18 inches long, with six rings of %6 -inch holes, rings spaced \% 

inches apart, six holes in each ring. Holes staggered in alternate rings. 

Tube pointing downstream.

METHODS OF TESTS

With the large number of devices to be tested in the laboratory it 

was desirable that some method be used that did not require too much 

time for the testing of each device. It was therefore decided to do 

as much preliminary work as possible with small-scale models, and so 

far as possible to use models for which the proper-size pipe fittings 

would be readily available. A 1:8 ratio was selected as being adapted 

for use in the small flume, 10 inches wide, in the laboratory. Prior 

to the selection of this ratio it had been decided to use a 3-inch intake 

pipe as the full-size prototype for the standard of comparison. The
INTAKES FOR GAGE WELLS 43

%-scale models, therefore, were made for intake pipes % inch in diameter. These models were mounted in a glass-sided flume 10 inches 

wide in such a manner that the effects of horizontal angles and vertical 

angles in the plane of the current could be studied. The intake devices were connected to a %-scale model well by the %-scale intake 

pipe. A standard static opening in the floor of the flume directly 

under the intake was connected to one of two glass manometer wells 

placed side by side. The other glass manometer was connected to 

the bottom of the model well. This arrangement was very effective 

in showing the amount of draw-down as indicated by the difference 

in the water levels in the two glass manometer wells. The heights 

of the water surfaces in the manometer wells were measured by a 

double-point gage having a point in each well. This was found to be 

more accurate than to make a direct reading of the height of the 

water surface in the flume with a point gage.

After the preliminary arrangements were completed and the %- 

scale A model in readiness for the tests, the members of the laboratory 

committee tested all the A models for a velocity of 2.8 feet per second 

passing the intake, the velocity being measured by a pygmy current 

meter. This method of procedure provided a ready means of comparing the performances of the various intake devices.

Suggestions for eliminating draw-down have generally fallen into 

one of three groups (1) reducing velocity and thereby reducing the 

draw-down; (2) using part of the velocity head to overcome the 

draw-down; and (3) straightening th& flow to eliminate the effect of 

velocity. Tests of the A models showed that most of the devices for 

which the draw-down was less than half the velocity head were in the 

group that straightens the flow, and few of the other devices appeared 

to eliminate the draw-down to that extent.

LABORATORY EQUIPMENT FOR TESTS OF i/8-SCALE

MODELS

The small glass-sided flume shown in plate 28, A, had been narrowed 

from a width of 20 inches to a width of 10 inches by a longitudinal 

partition. This small flume was 35 feet long, and the models were 

tested about 13 feet upstream from the lower end of the flume. As it 

was desired to have the arrangement correspond to field conditions as 

nearly as possible, and the models to be tested were %-scale, a model 

stilling well 1}( inches square was installed in the unused portion 

of the flume. This model of a stilling well 5 feet square was connected to the working half of the flume by a model of a 3-inch 

intake pipe consisting of %6 inch outside-diameter copper tubing. 

The outer end of this tubing was connected by a short length of rubber
44 METHODS AND EQUIPMENT USED IN STREAM GAGING

tubing and a nipple to the rear of a %-inch brass coupling supported 

by a mounting block so that its center was 2%6 inches above the floor 

of the flume and its front 3% inches out from the wall of the flume. 

The models were then screwed into the front of this coupling. The 

coupling was soldered to the lower end of a vertical %-inch brass pipe 

clamped in the mounting block. The mounting block itself was 

merely a device for supporting the models at various horizontal and 

vertical angles as well as in the normal position. These arrangements 

are shown in plate 28, B.

Glass manometers mounted side by side on the outside wall of the 

flume as shown in plate 29, A and B, were arranged for connection to 

models in various positions. The manometer wells 2 inches in diameter at the left of the series of manometers were used in obtaining 

comparative heights of water in the model well and in the flume at 

the intake. The left one of the manometers was connected to the 

bottom of the stilling well. The right-hand manometer could be 

connected to any one of several standard static openings in the floor 

along the center line of the working part of the flume, an opening in 

the same section as the coupling supported by the mounting block 

being used, except for those devices which by their form of construction interfered with the static water pressure at that point or conveyed the water into the stilling well from a different section of the 

flume. These openings were about 0.17 foot apart near the intake. 

The positions of the water surfaces in the two manometer wells were 

measured by a double-point gage having a point operating in each 

well. The heights of the water surface in the flume and in the stilling 

well could also be measured directly by a point gage mounted on a 

movable frame that spanned the sides of the flume. However, the 

fluctuations in the water surface in the flume made it difficult to 

obtain accurate readings by this method. The maximum capacity of 

the flume was about 1.75 second-feet. The flow was measured by e, 

rectangular weir in the return channel under the flume. This weir 

had been fully calibrated for previous projects in the flume and wa^ 

not recalibrated for this work. The velocity in the flume at the intake was measured with a pygmy current meter,

THE A MODELS

The series of /g-scale models to be tested in the small flume was 

designated the "A series." The dimensions of these models were not 

all exactly one-eighth the corresponding dimensions of the prototypes, 

but they were made as nearly to that scale as was practicable by the 

use of standard sizes of pipe, the dimensions of which were as shown 

in the following table:
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 868 PLATE

A. FLUME USED IN TESTS OF THE A MODELS.

B. MODEL GAGE WELL, MOUNTING BLOCK, AND SUPPORT, WITH MODEL A-39

POSITION FOR TEST.

Static openings in floor of flume.
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 868 PLATE 29

A. DRAW-DOWN IN MANOMETER WELLS UNDER THE POINT GAGES IN TEST OF

MODEL A-39.

..*-* \,

B. TESTS OF MODEL A-79 UNDER A VELOCITY OF 2.8 FEET PER SECOND. 

Manometer wells indicate practically no draw-down in this test.
INTAKES FOR GAGE WELLS 45

TABLE 2. Dimensions of standard sizes of pipe

Nominal di-

(inches)

X

M

H

tt

%l

2

25-i

3

4

Actual diameter (inches)

Inside

0.269

.364

.493

.622

.824

1.049

2.067

2.469

3.068

4.026

Outside

0.405

.540

.675

.840

1.050

1.315

2.375

2.875

3.500

4.500

NOTE. The 7/16-inch outside-diame.ter copper tubing that was used in some of the connections had and 

inside diameter of 0.354 inch.

An examination of the table of dimensions of standard sizes of pipe 

shows that the inside diameter of the %-inch pipe is very nearly 

one-eighth the inside diameter of the 3-inch pipe. Therefore ^-inch 

brass pipe was generally used for the models, although the outside 

diameter did not correspond to the scale ratio. Standard fittings 

were used where needed. These fittings did not have the correct 

outside diameter for the scale ratio, but their shape was made to 

correspond to that of the prototype.

Tests of /g-scale models were made for nearly all the devices that 

had been suggested by the district engineers. A few devices were of 

such shape that /g-scale models could not be made conveniently, and 

tests of those devices were made with full-size "P" models without 

the preliminary tests at %-scale. A list of the A models actually 

tested and their dimensions is given in the following table:

TABLE 3. Dimensions of A models 

Model No.

A-35 to A-41 _________ True to scale.

A-42 to A- 45_________ %-inch pipe.

A-l to A-6 ___________ J4-inch pipe fittings, outside shaped to form of prototype.

A-7 to A-14J All %-inch pipe fittings except that tee and nipple cap 

A-16 to A-18J -------- j^d outside shaped to form of prototype.

A-19 to A-22_ ________ ^-inch pipe fittings, outside shaped to form of prototype.

A-23 to A-34_________ All %-inch pipe fittings except that the cross and the

nipple cap had outside shaped to form of prototype. 

A-46 to A-51_________ True to scale, connected by }£-inch pipe.

A-54__.______________ True to scale, connected by %-inch pipe.

A-55__-______________ %-inch pipe 2}i inches long with four rings of %2-inch

holes, four holes in each ring. 

A-58 to A-64_________ %-inch tee, outside shaped to form of prototype.

A-65, A-73-__________ %-inch pipe and fittings, outside of cap shaped to form

of prototype. 

A-66 to A-67__---____ True to scale, on y±-inch pipe.

A-70--_-_____________ True to scale, on J4-inch pipe.

A 72, A-74, A-77_____ True to scale, on %-inch pipe.
46 METHODS AND EQUIPMENT USED IN STREAM GAGING

TABLE 3. Dimensions of A models Continued 

Model No.

A-78, A-83---________ i£-inch pipe and fittings. Pipe capped instead of having

plugged coupling, but cap is very close to scale model 

of coupling, as it is made of stamped metal instead 

of being cast.

A-85 to A-88-________ True to scale, }{-inch pipe connections.

All the models listed above were tested in the normal position and 

in addition they were usually tested at angles of 5° and 10° in both 

directions from the normal position in either a horizontal plane or a 

vertical plane or both in the direction of flow. Some models were also 

tested at horizontal angles of 15° and 20°.

All the models were tested under the same velocity of 2.8 feet per 

second. In table 4, which shows the results of the tests, the models 

are listed in the order of best performance in the normal position. 

Only the most favorable observation is shown where more than one 

^observation was made. The performance of some models in the 

normal position gives them a more favorable position in the list than 

is warranted by their performance under conditions of angularity. 

From a study of those tests 17 models were selected for further investigation at velocities of 1.0, 2.0, and 3.65 feet per second. Model 

A-39, a 3-inch pipe cut square, was also included for comparison. The 

results of the tests of the selected A models under the various velocities 

are given in table 5. The depth of water in the flume varied between 

0.55 and 0.65 foot.

The velocity at the intake for each setting of the flow in the flume 

was measured with a cup-type pygmy current meter that had previously been rated in the current-meter rating flume of the National 

Bureau of Standards. The meter could not be placed exactly at the 

intake, owing to the pipe connections, but was used 0.25 foot upstream 

from the center of the intake.

The static opening at the mounting block was used for all models 

except A-65, A-73, A-79, A-83, and A-88. For models A-65 and 

A-79 the opening 0.17 foot upstream was used, and for A-73 and A-83 

the opening 0.17 foot downstream was used. As model A-88 extended 

to the floor of the flume, no static opening in the immediate vicinity 

of the model could be accepted as giving a true indication of the height 

of water in the flume. Therefore a static opening about 8 inches 

upstream was used. As this model filled a large portion of the cross 

section when it was turned to the usual horizontal angles, the results 

obtained under those conditions may not have been truly representative of its performance in a natural channel.
TABLE 4. Results of tests of A models under a velocity of 2.8 feet per second 

1 Models listed in order of best performance in normal position. Where there was more than one observation the best observation is listed. There was a slight variation in the velocity]

Model

No.

A-65 

A-73 

A-81 

A-74 

A-72 

A -58 

A-79 

A-84 

A-87 

A -50 

A-85 

A-86 

A-49

A-51 

A-44 

A-52

A-48 

A-88 

A-59 

A-26 

A-46 

A-46 

A-13

A-B8 

A-ll

A-45 

A-24

Name '

Ash baffle (projecting 0.44 inch on the A model) 2 - _ _ - ....

3-inch tec with run on intake, 12-inch nipple in outlet pointing

3-inch tee with run on intake, outer end of run plugged, outlet

4-wav cross, horizontal, downstream outlet nlueaed^ _ ______ .__

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-10°

-0.011 

-. 003 

-.011 

-.013 

-.020 

-.052 

-.011

-.005 

-.024 

-.018 

-. 030 

-.027 

-.029 

-.030 

-.072 

-.059 

-.036 

-.079

-.065 

-.064

-.055

.016

-5°

-0.004 

.1) 

-.002 

-.008 

-.013 

-.028

.003 

-.012 

-.008 

-.019 

-.017 

-.023 

-.020 

-.047 

-.035 

-.023 

-.032

-.055

-.052

.037

0

0.0 

.0 

.002 

-.002 

-.002 

-.004 

.005

.006 

-.007 

-.008 

-.008 

-.009 

-.014 

-.014 

-.016 

-.018 

-.030 

-.032 

.033

-.036 

-.039

-.042

-.042

.050

+5°

0.002 

-.002 

.005 

.0 

.005 

.0

.004 

-.001 

-.005 

-.002 

-.005 

-.010 

-.009 

.009 

-.002 

-.011 

-.018

-.026

-.033

.065

+10°

-0. 001 

-.011 

.004 

.005 

.014 

.011 

.008

.0 

006 

.001 

.002 

.004 

.0 

-.003 

.041 

-.001 

-.002 

-.005

-.024 

-.030 

-.032

.085

Vertical angle

10°

0.0 

-.007 

.0 

-.005 

.010 

-.029

.003

-.014 

-.011

-.049 

-.043 

-.043

.039

-.094

.025

-5°

0.0 

-.001 

.002 

-.004 

-.004 

-.018

.004

-0.10 

-.010

-.047 

-.040 

-.043

.043

0.094

.066

0

0.0 

.0 

.002 

-.002 

-.002 

-.004

.006

-.008 

-.009

-.036 

-.039 

-.042

.042

-.048

.052

+5°

0.0 

-.003 

-.003 

-.004 

-.005 

-.032

.002

-.009 

-.013

-.048 

-.038 

-.040

.042

-.065

.068

+ 10°

0.0 

-.007 

-.001 

-.003 

-.004 

-.020

.001

-.010 

-.011

-.046 

-.040 

-.041

.040

-.080

.066

1 The descriptions are intended to refer to the full-size models for which the A models were constructed at a 1:8 ratio.

2 Baffle in end of model A-39.

s Model casting smoothed and polished.

4 Model as cast.
TABLE 4. Results of tests of A models under a velocity of 2.8 feet per second Continued

Model

No.

A-4 

A-7 

A-30 

A-28 

A-61 

A-34

A-2 

A-43 

A-71 

A-23 

A-60 

A-17 

A-29 

A-66 A-32

A-77 

A-14 

A-47 

A-25 A-31

A-70 

A-54 

A-8 

A-5 

A-55 

A-10 

A-21 

A-27 

A-18 

A-16 

A-42 

A-64 

A-33

Name

4-way cross, 12-inch capped nipple in streamward outlet, upstream

Canneld baffle, ___________ _______________________________________

4-way cross with 12-inch nipple in streamward outlet, upstream

Circular plate, 6 inches in diameter.. ______ __ ___ _ ____ __ ___

4-wav cross with 12-inch nipple in streamwaid outlet, downstream

Canneld baffle.. _..._._._-_.__...__..__......._._.___.___________.

Sawyer sieve _ _ . _

4-inch to 3-inch reducing coupling. __________________________ ___.

4-way cross with 12-inch capped nipple in streamward outlet, upstream outlet plugged.... __________________________ ___________

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-10°

-0. 124

-.094

.060

-.079

-.127

-. 157

-.161

 5°

-0. 100

-.088

.073

-.088

-.114

-.145

-.148

0

-0. 065

-.070 

-.072

-.075 

.078

.083

-.086

-.097

-.098

-.111

-.122

-.129

+5°

-0.043

-.073

.093

-.092

-.075

-.102

-.097

+10°

-0.011

-.055

.110

-.087

-.043

-.075

-.065

Vertical angle

10°

0.068 

.064

-.080

-.079

-.082

-.075

.085

-.107

-.096

-.124 

-.111

.138

-.116 

.140

-5°

0.069 

.072

-.080

-.073

-.081

-.074

.085

-.092

-.094

-.115 

-.108

.138

-.119 

.135

0

0. 059 

.062 

-.062

-.063

-.067

-.068

-.075

-.078 

-.079

.083 

-.084

-.086 

-.086

-.096 

.096

-. 100 

-.108

.115

.126 

-.126 

.126

.134

+5°

0.070 

.069

-.070

-.075

-.077

-.074

.084

-.088

-.089

-.102 

-.105

.139

.141 

-.129 

.135

+10°

0.068 

.060

-.078

-.078

-.082

-.076

.082

-.093

-.096

-.117 

-.106

.133

-.118 

.137

00
A-3

A-l

A-6

§ A-12

§ A-20

»

A-19

U.

A-9

A-40

d A-37

A-39

A-22

A-38

3-inoh to 2-inch reducing elbow, with 2-inch opening pointing

4-inch to 3-inch reducing elbow with 4-inch opening pointing

.112

-.153

-.128

-. 159

-.150

-.145

-. 150

-.166

-.161

-.161

-.157

-.157

-.164

-.164

-. 1G5

-.139

-.157

-.150

-.145

-.159

-.116

-.129

-.121

-.120

-. 129

-.157

.135

-.148

-.141

-.159

-.150

-.130

-.143

.135

-.138

-.144

-.147

-.146

-.136

-.135

.135

-.136

-.136

-.141

-.142

-.148

-.121

. 138

-.120

-. 130

-.128

-.114

-.138

-.106

.137

-.109

-.116

-.110

-.097

-. 135

CO
TABLE 5. Tests of selected A models under various velocities

STRAIGHT PIPE 1 

A-39. 3-inch pipe cut Square

Velocity at intake (feet 

per second)

10

2.0 _-_ _ -_-.--.

9 Si

3.65 .- -.-....

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-20° -15° -10°

-0. 128

-5°

-0.166

0

-0. 019

-.082

-.164 

-.'253

+5°

-6. 150

+10°

-0. 121

+15° +20°

Vertical angle

-10° 5° 0i go +10°

STATIC TUBES 

A-65. Long static tube pointing upstream

1.0 . 

2.8. -.-- 

0 CK

-0.002

-.Oil

-.026

0

-.004

-.010

0

.003

0

.002

.007

0

-.001

.003

6 0 0 0 0

A-73. Long static tube pointing downstream

1.0..--------..-- -- ---

2.8.-----.. .- ..---... -----

-0. 001

-.003

-.010

-0.001

0

-.007

-0.001

 0

-.013

-0. 002

-.002

-.013

-0.002

-.011

-.026

-0.007 -0.001 0 -0.003 -0.007

A-79. Short static tube pointing upstream

1.0 

2.0 -----------

2 8

2.82-__._- . 

3.65.- . . ._.

-0. 034

-.026

-0. 024

-.043

-0. 002

-.006

-.001

-.011

-.026

-0. 001

-.002

-.002

.007

0

.002

.005

.002

0

0.001

.004

.005

-.007

0.001

.004

.008

.004

0

-0. 005

-.003

-0.001

-.007

0

.003

0.002

-.007

6.002

0

-0.003

0

-0.001

-.010

Q

M 

£>

§

02

o
A-83. Short static tube pointing downstream

2.8'.....-- .- -----------

3.65 _.. .-- - _ 

-0. 002

-.007

-.005

-.026

-0.001

-.004

.003

-.013

-0. 001

-.004

.006

-.006

-0.001

-.005

.004

-.003

-0. 002

-.008

0

-.020

0.003 0.004 0.006 0.002 0.001

FLAT PLATES 

A-49. Ciicular plate 18 inches in diameter 4

2.0_-_- -- .--- - . --

2.8--- ... _-_ - 

3.65.--..-.-- .. - -__--_--_.-

-0.003

-.012

-.029

-.036

-0. 002

-.011

-.023

-.020

-0. 002

-.008

-.014

-.013

-0. 002

-.005

-.010

-.003

0

0

0

.023

0.001

.006

.011

.033

0.003

.011

.028

.052

A-50. Rectangular plate 1 by 2 feet

10.-- ... .... -- -.--_._-

2.0 .- -------- ---..- ....

2.8 _ -._. .. -.- 

3.65 ----- _.-- 

-0. 002 

-.008 

-.018 

-.023

-0.002 

-.008 

-.008 

-.013

-0. 002 

-.004 

-.008 

-.010

-0. 001 

-.002 

-.005 

0

-0. 001 

.001 

.001 

.013

0 

.004 

.009 

.033

0.002 

.011 

.021 

.043

A-87. Rectangular plate 1 by 4 feet 4

1.0 --------- -. _- ___ _

2.0 .--. .-__- __-- -- 

2.8 ... ------- ._.- ---__ -

3.65 - - -.- 

-0.003 

-.011 

-.024 

-.030

-0. 002 

-.006 

-.012 

-.016

-0. 001 

-.002 

-.007 

-.007

0 

.001 

-.001 

-.003

0.001 

.004 

.006 

.016

0.002 

.011 

.016 

.036

0.003 

.016 

.030 

.045

A-86. Rectangular plate 1 by 6 feet <

1.0-.-- . .- - -. --

2.0------ --.- ---------- -

2.8. ----- --.- --_.... _

3.65 _. .- .. ......

-0. 004 

-.014 

-.027 

-.046

-0.002 

-.007 

-.017 

-.026

-0. 001 

-.003 

-.009 

-.013

-0. 001 

-.001 

-.005 

0

0.001 

.003 

.004 

.010

0.001 

.009 

.013 

.023

0.004 

.015 

.024 

.046

-0. Oil -0. 010 -0.009 -0. 013 -0. Oil

QQ

1 For purposes of comparison.

2 Data for model A-81.

3 Model A-84 used at 2.8 feet per second.

4 Normal position parallel with direction of flow; intake at center of plate.
TABLE 5. Tests of selected A models under various velocities Continued

FLAT PLATES Continued 

A-85. Rectangular plate 1 by 8 feet 5

fcO

Velocity at intake (feet 

per second)

1.0.- -----.__. .........

2.0 - . , .. ...

2.8 -____- .. ...... ______ __

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-20° -15° -10°

-o.oot

-.015 

-.030 

-.043

-5°

-0. 002 

-.009 

-.019 

-.020

0

-0. 001 

-.003 

-.00? 

-.010

+5°

0 

0 

-.002 

.007

+10°

0.001 

.003 

.002 

.016

+15°

0. 002 

.010 

.010 

.036

+20°

0. 001 

.017 

.027 

.062

Vertical angle

-10°

-.014

 5°

-.010

0

-.008

+5°

-.009

+10°

-.010

---------- cj

I-H

TJ

A-51. Rectangular plate 1 by 2 feet, intake 6 inches downstream from center -g|

H

1.0 .-. ...

2.0. . .

3.65 

-0. 003 

-.014 

-.030 

-.036

-0. 003 

-.012 

-.020 

-.030

-0. 002 

-.008 

-.014 

-.020

-0.002 

-.006 

-.009 

-.010

-0.001 

-.002 

-.003 

.016

0 

.001 

.004 

.030

0.001 

.006 

.013 

.036

T1

.......... a

H

O 

A- 88. Rectangular plate 2 feet long, bottom on bed of stream, top 6 inches above intake

1.0 

2.8 

-0.011 

-.042 

-.079 

-.092

-0. 006 

-.021 

-.032 

-.049

-0. 004 

-.014 

-.032 

-.040

-0. 004 

-.010 

-.018 

-.030

-0. 002 

-.006 

-.005 

-.013

-0. 001 

-.002 

.012 

.003

-0. 001 

0 

.026 

.013

^

BAFFLES

O A-67. Twitchell baffle, original model >

1.0 .-.

2.0... _. ___.

2.8. 

0 

-.004 

.004 

-.003

0.001 

.001 

.012 

.013

0.001 

.007 

.012 

.026

0.001 

.005 

.018 

.036

0.002 

.006 

.019 

.026

t-i

- ---- Q
A-72. Twitchell baffle, 0.56 inch projecting from pipe

1.0--- ------------------

9 n

O o

3.65 

-0. 037 

-.046

-0. 032 

-.020

-0.004 

-.014 

-.020 

-.020

-0.003 

-.010 

-.013 

-.010

-0. 002 

-.004 

-.002 

.023

-0.001 

.001 

.005 

.016

-0.001 

.005 

.014 

.020

0.016 

.039

6.61s

.046

-0.010 

-.010

-0. 004 -0.002 

.023

-0.005 -0.004 

0

A-74a. Ash baffle, 0.38 inch projecting from pipe 5

1.0---.--- ---- ------

9 A

3.65 -- - -- --

-0.003 

-.007 

-.016

-0.003 

-.005 

-.007

-0.001 

-.001 

.003

0 

.003 

.013

0 

.005 

.020

A-74b. Ash baffle, 0.44 inch projecting from pipe

1.0- ------------------

9 0

9 Q

3.65 

-0.001 

-.007 

-.013 

-.016

-0. 001 

-.005 

-.008 

-.007

-0. 001 

-.001 

-.002 

-.003

0 

0 

0 

.010

0.001 

.003 

. .005 

.020

-0. 005 -0, 004 -0. 002 -0.004 -0. 003

MISCELLANEOUS 

A-46. Kinnison box

1.0. . 

9 A

9 S

3.65 

-0. 008 

-.027 

-.064

-.075

-0.007 

-.023

-.062

-0. 006 

-.023 

-.039

-.059

-0. 005 

-.022

-.052

-0. 004 

-.020 

-.030 

-.043

-0. 043 

-.072

-0.040 

-.062

-0. 039 

-.059

-0.038 

-.056

-0.040 

-.052

A-58. 3-inch tee, flow through run

1.0 

9 A

9 Q

-0. 006 

-.026 

-.052 

-.085

-0. 003 

-.013 

-.028 

-.033

-0.002 

.001 

-.004 

-. 003

-0.001 

.008 

0 

.016

-0. 001 

.009 

.011 

.016

-0.029 -0.018 -0.004 -0. 032 -0. 020

* Normal position parallel with direction of flow, intake at center of plate.

5 At 2.8 feet per second with projection of 0.38-inch but with total length of 1.07 inches the difference for zero angle was 0.010 on model A-69, which was slightly longer than A-62.

Oi 

CO
54 METHODS AND EQUIPMENT USED IN STREAM GAGING 

FULL-SIZE MODELS

The 47 full-size models that were selected for tests are listed on 

pages 56-58. The Eisenlohr box and the Walworth strainer were tested 

at full size without previous tests on 1:8 scale models, as their construction was such that they could not be accurately built at the 

1:8 scale. The full-size models of the devices for use with 3-inch 

intake pipes, sometimes called the "prototypes," were given the same 

serial numbers as the corresponding models at the 1:8 ratio but were 

distinguished from the small models by the use of the prefix P, the 

prefix A having been used with the same serial numbers for the small 

models.

Full-size models of devices for use with various sizes of intake pipes 

were given the following designations:

H, models for 1-inch pipe. 

K, models for 1%-inch pipe. 

L, models for 2-inch pipe. 

M, models for 2*4-inch pipe. 

P, models for 3-inch pipe. 

Q, models for 4-inch pipe.

APPARATUS USED IN TESTS OF THE FULL-SIZE MODELS

In order to make tests of the full-size models under velocities that 

would be comparable with those obtained in the 10-inch flume in the 

tests of the A models, a temporary timber flume 3 feet in width was 

constructed in the center of the 12-foot flume. (See pi. 30, A.) 

This 3-foot flume was 47 feet in length and was open at both ends. 

The sides at the upper end were curved outward to form a bell-shaped 

entrance, which extended 43 inches upstream beyond the straight 

part of the 3-foot flume. A 14-inch opening between the upper end 

of the bell-shaped entrance and the side wall of the 12-foot flume on 

each side admitted water to the 4.5-foot spaces on the two sides of the 

12-foot flume. These outer 4.5-foot spaces were closed by temporary 

bulkheads opposite the lower end of the 3-foot flume, as shown in plate 

30, A. Under this arrangement static water pressure was maintained 

on the outside of the 3-foot flume, although all the flow was carried by 

that flume. The height of water in the flume was controlled by needle 

gates 25 feet downstream. These needle gates were set so as to maintain a depth of 3 feet for all tests of the full-size models.

The exact height of water in the flume was measured by means of 

piezometer gages outside the flume wall connected to static openings in 

the floor of the flume. The static openings could also be separately 

connected to a stilling well equipped with a hook gage. The piezometers and the gage well are shown in plate 30, B. Static opening 

No. 1 was in the center of the flume 2 feet downstream from the intake connection, static opening No. 2 was in the center of the flume
INTAKES FOR GAGE WELLS 55

opposite the end of the intake pipe, and static opening No. 3 was in 

the center of the flume 2 feet upstream from the intake.

An intake pipe 3 inches in diameter passed through the side wall of 

the 3-foot flume and was placed so that the device under test when in a 

horizontal position would be in the center of the flume and 6 feet above 

its lower end. The outer end of the 3-inch intake pipe was connected 

to the outlet of a 3-inch tee, which in turn was screwed to the top of a 

3-inch riser pipe but was easily turned for obtaining horizontal angles 

by means of a %-inch pipe handle connected to the top run of the tee 

by means of reducers. The pipe handle was extended to an opening 

in the wall of the 12-foot flume so that the settings for the various 

horizontal angles could be made from outside the flume.

The device under test could be tilted to various vertical angles by 

turning the intake pipe in the tee connection, the angle of tilt being 

indicated by a pointer.

From the riser pipe at the outer end of the 3-inch intake pipe a 

1-inch pipe connection led to the same stilling well used for the connections to the static openings. Valves in each line permitted individual connections to be made to any one of the static openings and 

to the 3-inch intake pipe. Because of the pulsations in the water 

and the corresponding variations in the static head measured in 

the stilling well, the hook gage was replaced by a water-stage recorder 

(see pi. 30, B) having a height ratio of 5 : 12 (1 inch=0.2 foot) and 

a time scale of about 3.6 inches an hour. The continuous records 

of stages permitted average heights to be determined to the nearest 

0.001 or 0.002 foot.

As there was only one stilling well for use in obtaining comparative readings of stages indicated by the intake and by the static 

opening in the floor of the flume, the readings being taken individually 

by the use of valves on the connection pipes, it was essential that no 

change in flow should occur between the times of taking the two readings. The use of the water-stage recorder permitted any changes hi 

stage corresponding to changes in flow to be detected. Several 

observations were repeated because of slight changes in stage.

DISTRIBUTION OP VELOCITY IN THE 3.0-FOOT PLUME

The tests of the various intake devices were made with a depth of 

water of 3.0 feet in the 3.0-foot flume, the intake being placed so that 

the device was at the center of the flume. With a flow of 27 secondfeet in the flume and the needle gates set to maintain a depth of 3.0 

feet, the velocity at the end of the intake pipe was about 2.8 feet per 

second. The distribution of the velocity in the flume as determined 

from measurements made with a pygmy current meter is shown in 

figure 4.
56 METHODS AND EQUIPMENT USED IN STREAM GAGING

Water surface

0.5 1.0 1.5 2.0 2.5 3.0 

DISTANCE FROM LEFT SIDE WALL, IN FEET

FIGURE 4. Distribution of velocity in the 3-foot flume for a velocity of 2.8 feet per second at the intake.

MODELS SELECTED FOB TESTS

The models selected for the full-size tests corresponded to those 

which gave good results under the tests of %-scale A models in the 

10-inch flume. A few full-size models were tested without previous 

tests having been made at the }£-scale. Tests of intakes pipe with the 

ends cut square were made for purposes of comparison. The full-size 

models that were selected for tests are listed below.

TABLE 6. Full-size models selected for tests 

Model No. 

H-35________________ 1-inch pipe with end cut square.

K-36________________ l}£-inch pipe with end cut square.

L-37_________________ 2-iiich pipe with end cut square.

M-38___-_-______-___ 2^-inch pipe with end cut square.

P 39__-__-_____-____ 3-inch pipe with end cut square.

Q-40_________________ 4-inch pipe with end cut square.
INTAKES FOB GAGE WELLS 57

TABLE 6. Full-size models selected for tests Continued 

Model No.

P-46________________ Kinnison box with 6-inch nipple and cap at outer end.

M-49a______________ Circular plate, 16 inches in diameter, attached to 2}4-inch

intake.

P-49a_______________ Circular plate, 16 inches in diameter, attached to 3-inch

intake.

P-50________________ 12- by 24- by jKe-inch steel plate, long dimension horizontal, intake at center.

P-53___ _____________ Eisenlohr box, 6 by 20 inches, stream-lined, intake slot

half an inch by 15 inches.

L 58, M-58, P-58____ Stock tees, outlet on intake pipe, flow through run.

L 58a, M-58a, P-58a_ Stock tees, same as above except that threads were removed from run to make it of uniform diameter.

L-58b_______________ Handrail tee, threads removed from run.

L-72, M-72, P-72, Twitchell baffle, vertical and horizontal vanes one-eighth 

Q-72. of an inch thick held in position in models L-37, M-38, 

P-39, and Q-40, respectively, by set screws near outer 

end. Lengths as shown in table 8.

L 74, M-74, P-74, Ash baffle, vertical vane one-eighth of an inch thick held 

Q-74. in position in models L-37, M-38, P-39, and Q-40. 

Lengths as shown in table 8.

P-75________________ Walworth cast-iron strainer, catalog No. 88, pointing

straight out, normal to direction of flow.

P-76________________ Walworth cast-iron strainer, same as P-75 except pointing

downstream.

L-79__--_--__-______ Static tube, 2 inches in diameter, 14 inches long, eight

holes half an inch in diameter spaced 1J^ inches apart 

top and bottom. Tube pointing upstream.

M-79_ --___--_______ Static tube, 2}_ inches in diameter, 17% inches long, eight

holes five-eighths of an inch in diameter spaced \% 

inches apart top and bottom. Tube pointing upstream.

P-79________________ Static tube, 3 inches in diameter, 13% inches long, eight

holes three-quarters of an inch in diameter spaced 1}_ 

inches apart top and bottom. Tube pointing upstream.

P-80________________ Static tube, same as P-79 except pointing straight out;

normal to direction of flow.

L-83, M-83, P-83____ Static tubes, same as L-79, M-79, and P-79 except pointing downstream.

P-88__-__-_-_-______ Steel plate, same as P-50 except that another 12- by 24-

by Yi e-inch plate was attached below P-50 so that the 

total height was 24 inches. Intake in center of upper 

plate.

P-89________________ Static tube, 3 inches in diameter, 9>, inches long, four

rings of four holes three-quarters of an inch in diameter, 

rings spaced three-quarters of an inch apart.

P-90_ _______________ Static tube, 3 inches in diameter, 18% inches long, five

rings of two holes three-quarters of an inch in diameter, rings spaced 1}_ inches apart.

P-91._______________ Static tube, 3 inches in diameter, 18% inches long, six

rings of six holes nine-sixteenths of an inch in diameter, rings spaced 1}£ inches apart.
58 METHODS AND EQUIPMENT USED IN STREAM GAGING

TABLE 6. Full-size models selected for tests Continued 

Model No.

P-92________________ Static tube, 3 inches in diameter, 18% inches long, five

rings of six holes nine-sixteenths of an inch in diameter, rings spaced l}i inches apart.

P-93._____________ Static tube, 3 inches in diameter, 19 inches long, five

rings of four holes three-quarters of an inch in diameter, rings spaced \}'<i inches apart.

P-94________________ Static tube, 3 inches in diameter, 13 inches long, five

rings of four holes three-quarters of an inch in diameter, rings spaced 1 inch apart.

P-95________________ Static tube, 3 inches in diameter, 12]/£ inches long, outer

end closed by plug with hemispherical nose instead of 

standard coupling and plug; arrangement of holes 

same as in P-94.

P-96-_______________ Static tube, same as P-93 except that length of tube

between couplings was 18 inches.

P-97________________ Static tube, same as P-94 except that length of tube

between couplings was 12 inches.

P-98-_-__-__________ Static tube, same as P-95 except that length of tube was

12 inches.

L-99._______________ Static tube, 2 inches in diameter, 12 inches long, 5

rings of 4 holes % inch in diameter, rings spaced 1 

inch apart.

TESTS

In the tests of the full-size models each device that was to be tested 

was attached to the outer end of the intake pipe by means of a coupling, or a coupling and elbow, so that the intake opening would be in 

the center of the 3-foot flume, or as nearly in the center as it could be 

placed. The models were all tested in a level position, with the device 

pointing in the direction in which it was intended to be used. In 

addition to the tests of the models in the normal position, tests were 

also made with the models turned through horizontal angles of +5° 

+ 10°, 5°, and 10°; and for similar vertical angles. The horizontal angles were designated "plus" for a movement in the clockwise 

direction from the position in which the intake was intended to be 

used, and "minus" for a counterclockwise movement. Vertical 

angles were designated "plus" if the movement was upward from the 

normal position and "minus" if downward. The effects of angularity 

were studied in order to obtain information regarding the relative 

performance of the various devices if the direction of flow was at an 

angle with the intake.

All the models were tested for the same velocity of water in the 

flume, which was 2.8 feet per second immediately in front of the 

intake when the mean velocity in the flume was 3.0 feet per second. 

(See fig. 4.) The corresponding discharge was 27 second-feet, which
INTAKES FOR GAGE WELLS 59

was as much as could be obtained for continuous use from the pumps 

that were available.

Static opening No. 2, immediately under the intake, was generally 

used in the determination of the height of water in the flume, but for 

the static tubes pointing downstream the average of heights for 

openings Nos. 1 and 2 was used, and for static tubes pointing upstream the average for openings Nos. 2 and 3 was used, as for these 

positions of the static tubes the openings in the tubes were between 

the two static openings in the flume.

A considerable number of the models that gave favorable results 

under the tests at 2.8 feet per second were subsequently tested for a 

velocity of 2.0 feet per second. The results of the tests for both of 

these velocities are given in table 7.

A comparison of the results of the tests of full-size models of devices 

for use with different sizes of pipe, including the static tubes, the Ash 

and Twichell baffles, the circular plate, the tee connections, and the 

straight pipe with end cut square, are given in table 8. The tests 

shown in this table were all for the same velocity of 2.8 feet per second. 

The correct lengths of the Ash and Twichell baffles for use with different sizes of pipes were determined by experiment. The results of the 

experimental tests for determining the correct lengths are given in 

table 9.
TABLE 7. Tests of full-size models of 3-inch intake devices

Model

No.

P-79 

P-83 

P-89 

P-90 

P-91

P-92

P-93 

P-93 

P-94 

P-94 

P-95 

P-95 

P-96 

P-96 

P-97 

P-97 

P-98 

P-98 

L-99 

L-99

P-72 

P-74

Name

STATIC TUBES '

12^-inch static tube (round nose) pointing downstream.

12-inch static tube (round nose) pointing upstream____ 

12-inch static tube (round nose) pointing downstream,.

BAFFLES 

Twitchell, 6 inches long, projecting 3 inches from end of

Ash, 5}>£ inches long, projecting 2% inches from end of 

pIpe~~~- ~ -- __--- .- 

Velocity 

(feet per 

second)

/ 2.0 

\ 2.8 

/ 2.0 

I 2.8 

f 2.0 

{ 2.8 

/ 2.0 

\ 2.8 

f 2.0 

1 2.8 

/ 2.0 

\ 2.8 

2.8 

2.8

2.8 

2.8

2.8

2.8 

2.8 

2.8 

2.8

2.8 

2.8 

2.8 

2.8

f 2.0 

\ 2.8 

f 2.0 

1 2.8

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-10°

-0. 009 

-.020 

-.008 

-.013 

-.OOfi 

-.011 

-.005 

-.002 

-.004 

-.009 

-.003 

-.007 

-.007 

-.006

-.005 

-.009

-.007

-.010 

-.008 

-.004 

-.002 

-.003

-.008 

-.003 

-.006 

-.013

-.010 

-.020 

-.007 

-.017

 5°

-0. 006

-.008

-.004

-.007

-.006

-.005

-.005 

-.011 

-.005 

-.010

0

0.005

.004 

-.002

-.004 

-.003

-.002 

-.003

-.004 

-.002

-.004 

 .002

-.004 

-.003

.005

-.005

.002

-.004

.007

0

0 

.006

.001

.004

-.003

-.001 

0 

-.001 

0

+5°

0.006

-.006

-.003

-.005

-.005

-.003

.005 

.008 

.003 

.008

+10°

0.002

.008 

-.COS 

-.013 

-.002

-.005 

-.008 

-.002 

-.004 

-.006 

-.004 

-.005 

.007 

-.007 

.004 

-.010 

.003 

-.010 

.009 

-.006 

.009 

-.006 

.007 

-.007 

.012 

-.008

.013 

.022 

.009 

.015

Vertical angle

10°

0.003

.001 

-.004 

-.008 

-.006

-.011 

-.005 

-.009 

-.006 

-.003 

-.002 

-.003 

0 

-.007 

.002 

-.008 

0 

-.009 

.004 

-.005 

.002 

-.005 

.004 

-.005 

0 

-.011

-.005 

-.010 

-.001 

0

5°

0.003

-.008

-.006

-.C04

-.001

0

0

0.005

.004 

-.002

-.004 

-.003

-.002 

-.003

-.004 

-.002

-.004 

-.002

-.004

fine

nriK

-.004

nn?

0 

nn7

0

.001

-.003

-.001

0 

-.001

0

+5°

0.003

-.010

-.006

-.000

-.011

-.004

+10°

0 

.003 

-.004 

-.008 

-.008 

-.011 

-.006 

-.010 

-.008 

-.011 

-.006 

-.010 

0 

-.009 

-.004 

-.012 

-.005 

-.015 

0 

-.008 

.001 

-.009 

-.083 

-.009 

-.002 

-.019

-.006 

-.010 

-.003 

-.002

Oi 

O

§
P-46

P-53

P-49 P

en

P-88 P

QQ

P-58

P-62

P-75

P-76

STKEAM-LINE BOXES

FLAT PLATES

MISCELLANEOUS

/ 2.0

I £. O

/ 2.0

I Z. 8

2.8

f 2.0

\ 2.8 

f 2.0

1 no

f 2.8

\ 2.8 

2.8

2.8

2.8

2.8

2.8

-.012

-.019 

-.004

-.009 

-.014

-.010

-.078

-.011

-.007

 . uuo 

-.010

-.008

-.084

-.140

-.009

-.006

 . 006 

-.010

-.002

-.006 0

-.005

-.081

-.059

-.100

-.010

 . uio 

-.006

-.006 0

-.074

-.010

-.009

-.015 

-.002

 . UUl

.003

0

.005

-.062

-.116

-.008

-.011

-.005

 . uuy

-.005

-.009

-.149

-.011 

-.002

-.001

-.007

-.014 

-.006

-.006

-.002

-.006

-.146

 . uio 

-.011

-.011

-.008

-.011 

-.011

 . 016

-.006

-.010

-.146

1 See rp. 57-58 for statement regarding number and size of holes in each tube.

2 Could not be used in any other position.

3 End of pipe projecting 17)2 inches from wall.
TABLE 8. Comparison of tests of full-size models of devices for use with various sizes of pipes at a velocity of 2.8 feet per second OS 

bO

Model

No.

L-79 

M-79 

P-79 

L-83 

M-83 

P-83 

L-72 

M-72 

P-72 

Q-72 

L-74 

M-74 

P-74 

Q-74 

M-49 

P-49 

H-35 

K-30 

L-37 

M-38 

P-39 

Q-40 

L-58 

M-58 

P-58 L-62

M-62 

P-62 L-63

Size of 

pipe 

(inches)

2

%

3 

2 

2Ji 

3 

2 

21-6 

3 

4 

2

2M 

3 

4 

2H 

3 

1

1« 

2 

2^ 

3 

4 

2 

2^ 

3 

2

2^ 

3 

2

Description

do

_. ..do . . . 

 . do _.. 

_. do - -. ------ -... .....

. ..do... - . --.- -..- _. -_... 

Twichell baffle 5*4 inches long, projecting 25<6 inches___ 

Twichell baffle 5% inches long, projecting 2% inches _

. do ..... 

___. .do ...... ... ___ ....

 do . ._ __.. _ 

 --do ..-...-. . - -- .......

Standard tee with outlet on pipe, flow through run _.

 .do - .. 

Standard tee with outlet on pipe, threads removed

^____do_____._. ._ ...__.. _._... _ 

 .do . .................... .____________..._

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-10°

-0. 021 

-.014 

-.020 

-.010 

-.012 

-.013 

-.021 

-.018 

-.020 

-.014 

-.015 

-.012 

-.017 

-.016 

-.016 

-.014

-.122

-5°

-0.004 

-.008 

-.006 

-.004 

-.004 

-.008 

-.015 

-.010 

-.011 

-.011 

-.012 

-.008 

-.010 

-.008 

-.014 

-.010

-.140

0

0.007 

.004 

.004 

-.003 

-.002 

-.004 

-.003 

0 

0 

0 

-.001 

-.001 

0 

.001 

-.007 

-.010 

-.168

-.163

1-.161

-.152

-.146 2-. 133

-.040

-.051

-.059

-.062

-.078

-.100

-.033

+5°

0.006 

.004 

.006 

-.005 

0 

-.006 

.008 

.007 

.008 

.005 

.010 

.008 

.008 

.010 

-.004 

-.006

-.142

+10°

0.007 

.007 

.008 

-.010 

-.007 

-.013 

.014 

.018 

.022 

.016 

.014 

-.002 

.015 

.020 

.006 

.003

-.116

Vertical angle

-10°

0.004 

.001 

.001 

-.006 

-.003 

-.008 

-.012 

-.009 

-.010 

-.010 

0

0 

-.005

-.149

-5°

0.003 

.005 

.003 

-.005 

-.001 

-.008

0

0.007 

.004 

.004 

-.003 

-.002 

-.004

_ nno

0

0 

0 

-.001

-.001

0 

.001

-.146

+5°

0.004 

.002 

.003 

-.002 

-.007 

-.010

+10°

0.003 

0 

.003 

-.005 

-.006 

-.008 

-.015 

-.008 

-.010 

-.009 

0 

-.002 

-.002 

-.008

-.146

 0.082 foot at 2.0 feet per second. -0.069 foot at 2.0 feet per second.
TABLE Q.-^Tezts oj Twitchell and Ash baffles oj various lengths with different sizes of pipes

TWITCHELL BAFFLES f 

A models

Model No.

A-67 - . - -- - - , --- -

A 79

A-72 - - . -- ---- 

A 79

A-72

Size of 

pipe 

(inches)

%

H

8

Length of baffle

Total 

length 

(inches)

1.42 

1.03 

1.03 

1.03 

1.03 

1.03 

1.03

Projection 

from pipe 

(inches)

0.75 

.00 

.12 

.25 

.38 

.56 

.62

Velocity 

at intake 

(feet per 

second)

2

0 

. o

2.8 

2.8

2

0 

. O

2

0 

. o

2.8 

2.8

D iff erence, in feet , in elevat ion of water surface in well from that in flume

Horizontal angle

-10°

0.004

-.020 

-.020

-5°

0.012

-.013 

-.009

0°

a 012

-.152

-.094

-.032

-.019

-.002 

.001

+5°

0.018

.006 

.011

+10°

0.019

.014 

:018

Vertical angle

-10°

-0. 010

+10°

-0. 004

Full-size models

L-72- - - - .. - --- -

Lr-72.-. .-. _---- -. -- .-- ---..----__

M-72- - -.--- _ -.. --_ -

M-72- - - __ - _

P-72 _- .- _- . _.._ _ 

P-72-- ........... ...................................

P-72 . - - 

P-72 

P-72. _ - _ - - -------

Q-72 _ __ 

Q-72

Q-72 . -

Q-72 .- . .-....--.....-.-..- .-. ..-.-..

2

2

VA21/4

3

3

3

3

3

4

4

5.00

5.25

5.50

5.75

5.00

5.50

6.00

7 ftft

8.00

7 nn

7.25

7.75

8.00

2.50

2.62

2.75

2.88

2.50

2.75

3.00

4.00

3

CA

3.62

3.88

4 ftft

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

2.8

-0.021

-.018

-.020

-0.015

-.010

-.011

-.011

-0. 007

-.003

000

-.008

-.003

nr\A

006

AAA

.002

.004

f)f\K

0.008

.007

.008

0.014

.018

.022

-0. 012

-.009

-.010

-.010

-0. 015

-.008

-.010

AflQ

O5 

CO
TABLE 9. Tests of Twiichell and Ash baffles of carious lengths with different sizes of pipes Continued

ASH BAFFLES 

A models

Model No.

A 74

A-74

A-74 

A 74

A 74

A -74

A-74 

A 74.

A 74.

A-74 

A-74... . 

A-74. - .

A-74 

A-74- - --. - - - - ----

A-74

A-74 

A-74 ... ._

A-74 _ ... --

A-74

A-74

A-74 . 

A-74.

A-74- 

A-74 - -. . -. .- -. -. .

A-74 -_ .. .

A-74 

A-74____. ... ... _ .... 

A-74-. _ - . . _ ... ... ... .........

A-74. ............... .......... ........ ..... . 

A-74--. ........... .. - .. 

A-74.......... 

A-74 ... .... ......... ........ A-74

A-74.----.-....---..-..--.-.--.-.. .----... -.-.-.

Size of 

pipe

(inches)

V± 

Yt 

X 

H 

M

y±s

x

Yt k

v± y± y±Y* y*y± y±

8

u

X

A %1

1A

&Y±

Y±

%U

%y± y±

Length of baffle

Total 

length 

(inches)

0.60 

.69 

.75 

1.00 

.72 

.75 

.94 

1.00 

1.25 

1.38 

1.38 

1.44 

1.07 

.94 

.56 

.88 

1.12 

.75

.88

1.00 

1.50 

.75 

.88 

1.00 

1.12 

.88 

1.00 

1.12 

1.19 

1.25

2.00

Projection 

from pipe 

(inches)

0.30 

.34 

.38 

.50 

.36 

.38 

.47 

.50 

.62 

.50 

.75 

.75 

.38 

.25 

.31 

.31 

.31 

.38

_ .44

.50 

.75 

.38 

.44 

.50 

.56 

.59

.62 

1.00

Velocity 

at intake 

(feet per 

second)

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

3.65 

3.65 

3.05 

3.65 

1.0 

1.0 

LO 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8 

2.8

Difference, in feet, in elevation of water surface in well from that in flume

Horizontal angle

-10°

0.015

-.039 

-.013

-.016 

-.003 

-.003 

-.001 

-.013

-.024 

-.021 

-.015 

-. 016 

-.015 

-.017 

-.014 

-. 016 

-.015 

-.013

-5°

0.030

-.030 

-.007

-.007 

-.003 

-.003 

-. 001 

-.008

0°

-0. 009

-.004

.000

.014

-.011

-.015

-.004

.002

.011

.003

.008

.023 

.010

-.009

-.026 

.007 

.010

.003 

-.001 -:oo2

-.001 

-.002 

.003

.022

-.012

-.007

-.004

-.001

. .000

-.005

.001

.002

-.001

.003

.024

+5°

0.039

-.020 

.023

.013 

.000 

-.002 

.000 

.000

+ 10°

0.045

-.013 

.026

.020 

.000 

-.002 

.001 

.005

-.002

.002

.008

.009

.009

.006

.013

.016

.014

.018

Vertical angle

-10°

0.033

-.005

+10°

0.032

-.003

o:

 o 

a
Full-size models

L-74 - 

L-74 

L-74 .. -------------------------- -~

M-74 - - -.

M-74 ... ... 

M-74__ 

P-74 ______ __ __. _ _

P-74 .. 

Q-74........ . . - . -- §

-74 . . . . ...... ...- --

-74 - . . ... , .

Q-74 _.-____ 

222

2X2

2te

2te 334444

3.5

4.5

5.5

4.0

5.0

6.0

5.0

5.5

6.0

6.0

6.25

6.5

7.0

1.75

2.25

2.75

2.0

2.5

3.0

2.5

2.75

3.0

3.0

3. 12

3.25

3.5

2.8

2.8

2.8

2.8

2.8 3 0

2.8

2.8

2.8

2.8

2.8

2.8

2.8

-6. 015

-.012

-.017

-.016

-0. 012

-.008

-.010

-.008

-0. 008

-.001

.006

-.006

-.001

.008

-.006

.000

.006

-.002

.001

.006

6.010

.008

.008

.010

0.014

.018

.015

.020

0.000

-.002

0.000

-.005

0.666

-.002

-.002

-.008
66 METHODS AND EQUIPMENT USED IN STREAM GAGING

COLLECTION OF DEBRIS ON INTAKE

The relation ordinarily existing between the heights of water in the 

river channel and in the stilling well where the records of stages are 

obtained may be changed if debris becomes lodged or collects at the 

end of the intake pipe in such a manner as to interfere with the free 

movement of the water into and out of the gage well. In order to 

obtain some information regarding the effects of debris on the performance of intake devices, the collection of debris in the 3-foot flume 

was simulated by means of an ordinary cement sack which was placed 

in the flume and allowed to drift dowTn with the current until it came 

into contact with the end of the intake pipe and partly covered the 

intake device. The results obtained are shown in table 10 and should 

be considered as being qualitative rather than quantitative, as the 

conditions of the experiments could not be exactly duplicated for the 

various intake devices.

TABLE 10. Effects of collection of debris on intake

Intake

No.

P-74

P-89 

P-79 

P-83 P-53

P-50

P-76 

P--19 

P-46

Description

Ash Baffle:

Eisenlohr box:

Flat plate 12 by 24 inches: 

Sack caught on upstream end with ends over top and bottom of

Sack hooked en upstream end with part on back and rest covering

Difference in elevation, 

in feet, of water surface in well from that 

in flume

With sack

-0. 090 

-.110 

-.OS'S 

-.055 

-.036 

-.065

-.073 

-.057 

-.045

-.016

-.040 

-.053 

-.044 

-.069

Without 

sack

0 

0 

0 

-.002 

.004 

-.004

-.006 

-.006 

-.006

-.006

-.006 

-.010 

-.010 

-.014

REMOVAL OF SILT BY FLUSHING

The ease and completeness with which the devices attached to intake 

pipes may be cleaned and accumulations of silt removed from the 

intakes by the flushing apparatus usually installed in gage structures 

is an important consideration in the selection of the design. Intakes 

having large openings might be expected to flush more readily than 

those having small openings, even though the number of the small 

openings was large enough to give the same total area. In order to
INTAKES FOR GAGE WELLS 67

obtain some information with respect to the ease of flushing of various 

intake devices, particularly the different designs of static tubes, provision was made for experimental tests under conditions similar to 

those existing at gaging stations equipped with facilities for flushing

intake pipes.

FLUSHING APPARATUS

A cylindrical steel tank about 6 feet in diameter was available as 

a source of water for the flushing tests. This tank was provided with 

a glass manometer and had been calibrated so that the amount of 

water discharged from it could be determined from the manometer 

readings. The average head used in flushing was about 21 feet, the 

reduction in head during a test because of the drop of the water level 

in the tank being only about 0.2 foot. The area of the cross section of 

the tank was such that a difference of 0.2 foot in the height of water 

corresponded to a release of 43.6 gallons.

A 4-inch pipe line, which was reduced from an 8-inch pipe line 12 

feet above the outlet, was connected to a quick-acting valve. A 

4-inch to 3-inch reducing bushing on the outlet of the valve was connected to a 6-foot length of 3-inch pipe to which the various static 

tubes and other intake devices were attached by means of a 90° 

elbow. In making the flushing tests, the intake devices were filled 

with soft mud or silt and then attached to the elbow of the 3-inch 

pipe. By observing the time between the opening and closing of the 

quick-acting valve and the corresponding drop of the water in the tank, 

the discharge through the intake device, in gallons per second, was 

determined. Observations of the amounts of water discharged 

through the devices in equal intervals of time without the use of silt 

were also made for purposes of comparison.

TESTS

The static tubes and other devices were flushed with clean water and 

then filled with mud and flushed again. The mud was a soft clay 

that would just start to flow out of the holes in the static tubes under 

a head of about 1 foot. Each tube was completely filled with mud back 

to the elbow connection. In flushing out the mud, the quick-acting 

valve was opened for 15 seconds and then closed, the amount of water 

discharged during that period being considered a measure of the efficiency of the device under the flushing test. No mud remained in the 

tubes after flushing, except for a few small pieces between the last 

holes and the plugged end of the tube in some of the longer models. 

The 3-inch pipe, corresponding to model No. P-39, was flushed with 

clear water as a basis of comparison. The results of the tests are 

shown in the following table:
68 METHODS AND EQUIPMENT USED IN STREAM GAGING 

TABLE 11. Flushing tests of intake devices for 8-inch pipe

Model

No.

P-39

P-791

P-83J P-89

P-90

P-96

P-92

P-53

P-93

P-94

P-95

Number and size of holes

8 holes % inch in diameter top and

bottom. __ -__ _

4 rings of 4 holes, % inch in diameter -

5 rings of 2 holes, H inch in diameter. .

6 rings of 6 holes, -He inch in diameter^

5 rings of 6 holes, 9ie inch in diameter __

do

Total area 

of openings 

(square 

inches)

7.4

7.1

7.1

4.4

8.9

7.5

7.5

8.8

8.8

8.8

Tube clean

Time 

(seconds) 

for discharge 

of 43.6

gallons of

water under

21 feet

average

bead

4.6

7.5

7.9

9.8

6.6

7.4

6.7

7.0

7.0

Discharge 

(gallons

per

second)

9.5

5.8

5.5

4.4

6.6

5.9

6.6

6.3

6.3

Tube filled with mud;

valve open for 15

seconds, then closed

Discharge 

during

15 seconds

(gallons)

85.0

80.7

62.6

91.6

85.0

80.7

Discharge 

(gallons

per

second)

5.7

5.4

4.2

6.1

5.7

5.4

_._.____..

For the condition of "tube filled with mud" the intake device was completely filled with a soft clay mud. 

Mud would just start to flow out of holes under about a 1-foot head. At the end of the 15-second run tbe 

mud was all removed except for a few lumps between the holes and the closed end in models P-77, P-78, 

and P-79.

RESULTS OF THE INVESTIGATION

The results of the tests of the full-size models that were selected for 

study in the large flume after the eliminatioD of a large number of 

designs by tests of small models in the 10-inch flume indicated that 

the static tubes were the most effective devices for eliminating drawdown, consideration being given to the results obtained when the 

models were tested in the most favorable position with respect to 

direction of flow past the intake and also to the results obtained when 

there was angularity of flow. The performance of the Ash baffles 

and the Twitchell baffles was practically as good as that of the static 

tubes if the direction of flow was at right angles to the intake, but the 

baffles were not as effective as the static tubes if the direction of flow 

was at an angle greater or less than 90°. The Eisenlohr box did not 

differ greatly from the static tubes in its effectiveness if there was 

angularity of flow and was nearly as good for all conditions. The 

Eisenlohr box (see pi. 31, A) is further considered on page 75. The 

Walworth strainer pointing downstream was not as satisfactory as 

the above-mentioned devices when the flow was at right angles to the 

intake but was not materially affected by angularity of flow, its 

effectiveness with respect to elimination of draw-down remaining 

about the same for a considerable amount of angularity in the direction 

of flow at the intake. The rectangular plate, the circular plate, and 

the Kinnison box (see pi. 31, B) came next in the order of satisfactory 

performance. The square plate extending to the bottom of the flume 

was used to simulate a model of a concrete pier. Because of its size
GEOLOGICAL SURVEY WATER-SUPPLY PAPER 86S PLATE 30

A. OUTLET OF 3-FOOT FLUME.

B. PIEZOMETER GAGES AND STILLING WELL FOR THE 3-FOOT FLUME.
GEOLOGICAL SURVEY WATEK-SUPPLY PAPER 868 PLATE 31

A. EISENLOHR INTAKE BOX.

B. KINNISON INTAKE BOX.
INTAKES FOR GAGE WELLS 69

it could be tested only in the one position, but the results were very 

satisfactory in that position with the flow parallel to the plate.

RECOMMENDATIONS FOR DESIGNS

Simple designs that are readily obtainable without the necessity of 

special castings or complicated machine work are generally desirable 

unless the performance of special designs appears to be more satisfactory. In the selection of the type of intake device to be used at a 

gaging station the effectiveness of the device should receive primary 

consideration. The ease and completeness with which it may be 

cleaned by the flushing arrangement ordinarily used in flushing the 

intake pipe and the manner in which it may be affected by floating 

debris are important factors in the operation of the station. In 

rivers where the water is deep and swift the installation or removal of 

an intake device may be expensive, and under these conditions the 

initial cost of the device may not be the controlling factor in its 

selection.

STATIC TUBES

The static tube appears to be the most satisfactory device for eliminating draw-down at intakes to gage wells, so far as could be determined 

from the laboratory tests.

The static-tube device may be made in various designs and in any 

size corresponding to the size of the intake pipe with which it is to be 

used. Designs of static tubes showing dimensions and arrangements 

of openings are illustrated in figure 5. The total area of the holes 

should be about 20 to 25 percent greater than the cross-section area of 

the pipe, in order that deposits of mud and silt may be effectively 

removed by flushing of the intake. The laboratory tests indicated 

that a suitable arrangement of openings to provide the required area 

for the 2-inch, 2K-inch, and 3-inch pipes may be obtained by using 

five rings of holes with four holes in each ring, the rings 1 inch apart 

and the holes staggered in alternate rings. For the 4-inch pipe, six 

rings with six holes each are suggested.

For pipe diameters of 3 inches or less the net length of tube between 

shoulders of couplings should be not less than 12 inches, and the outer 

rings of holes should be not less than 4 inches from the shoulders of the 

couplings. These dimensions correspond to those of static tubes 

tested in the laboratory. For pipes larger than 3 inches in diameter it 

is probable that the minimum length of the tube should be about four 

times the diameter of the pipe. The outer end of the tube may be 

threaded for a standard pipe coupling and closed by means of a 

standard plug, or it may be closed by a plug specially fitted to the 

inside of the pipe. If preferred, a cap may be used instead of the 

coupling and plug. The use of a special round-nose plug did not give
70 METHODS AND EQUIPMENT USED IN STREAM GAGING

2" Intake pipe

Four Ji-inch holes per ring

Use 2-inch pipe and fittings.

" !" + I""f '"+ ! 'S

Four 5/e-inch holes per ring

Use 2>j-inch pipe and fittings.

Flow

F=\

s

r->

LJ

©

O 

©

 sW 4.i"-J»

© ©

r+i'+i

Four3/-4--inch holes per ring

Use 3-inch pipe and fittings.

3' Intake pipe

!

i

 '

p

 '

[ © 

O (

o

©_ 

 6%. «|»l'**l'i

"8 &" 

© O

Flow

Six 3A-inch holes per ring

*" Use 4-inch pipe and fittings.

4 Intake pipe

Note.- Edges of holes to be free of burrs but not rounded. 

Tube to be fixed in a horizontal position.

FIGURE 5. Designs of static tubes for use with 2-inch, 2}^-inch, 3-inch, and 4-inch intake pipes.
INTAKES FOR GAGE WELLS 71

results materially different from those obtained with the standard 

coupling and plug. The hydraulic performance of static tubes made 

in the lengths specified above was the same when the tubes were 

pointing upstream or downstream, but less difficulty because of submerged drift and debris may be expected if the tube is used pointing 

downstream.

The static tube may be connected to the intake pipe by means of a 

90° elbow or by a standard tee. If the intake pipe points upstream 

from an artificial control, the connection may be made as shown in 

figure 6. The tube should be fixed securely in a horizontal position, 

and provision made so that it will not tilt downward by turning of the 

coupling under its own weight or any additional weight that may be 

placed upon it. In using a standard tee connection the static tube 

should be attached to the leg of the tee, the run of the tee opposite the 

well being closed with a plug.

The static tube devices tested at the National Hydraulic Laboratory 

were constructed of so-called "wrought iron" pipe with threaded ends 

for connection to standard pipe fittings. One end of the tube was 

connected to a standard pipe elbow. At the other end there was a 

sleeve coupling into which a standard plug was screwed for closing the 

end of the tube. The "length" of the tube was considered to be the 

distance along the tube between the protuberances of the coupling 

and the elbow; the gross length of the tube, including the threaded 

ends, consists of the so-called "tube length" plus the distances to 

which the coupling and the elbow are screwed on the pipe. It was the 

intention to test such designs as could readily be constructed by pipe 

fitters, using materials that could be obtained at stores and shops 

dealing in ordinary pipe fittings. The holes were drilled straight 

through the tubes, any roughness or "burr" being smoothed off, but 

with no bevel or rounding of the edges. The tubes were made long 

enough to extend beyond the disturbance caused by the elbow and 

the intake to the well.

The static tubes may be made of ordinary wrought-iron pipe and 

pipe fittings, or of galvanized wrought-iron pipe. Other materials, 

such as brass, bronze, cobper, or stainless steel, may be used if desired. 

The first cost of tubes made of ordinary wrought-iron pipe, either 

plain or galvanized, is comparatively small, whereas the first cost of 

tubes made of other materials would be somewhat larger, and their 

performance probably would be no better than that of the less expensive tubes if the latter were not affected by corrosion. However, if 

the effectiveness of the tubes made of so-called "wrought iron" pipe 

became impaired by accumulations due to corrosion, the cost of their 

replacement in deep, swift water might be much greater than the first 

cost of tubes made of noncorrosive material.
fcO

Coupling and plu Control

Pile, rock, or 

concrete base

FIGURE 6. Static-tube connection to intake pipe of gage well at stream-flow measurement station provided with artificial control.
INTAKES FOR GAGE WELLS 73

BAFFLES

The Ash baffle and the Twitchell baffle appear to give practically 

as good results as the static tube where the direction of flow is at an 

angle of 90° to the intake, but are not as effective if the direction of 

flow is at an angle considerably greater or less than 90°.

f

( !~

 

A Intake pipe j

I ' L

/Steel p

/

i_

z

date

-End of pipe ^-Fillet weld

cut square "to pipe 

DIMENSIONS

Baffle to be of such width that it will fit snugly 

inside pipe. Length to be as shown in table.

Nominal diameter Length of baffle

of pipe L Baffle to be fixed in

2" 4>| vertical position

2^z 5" 

4" elf

normal to current.

FIGURE ". Design of Ash baffles for intake pipes of various sizes.

End of pipe 

'cut square Fillet weld to pipe

r

\ \ Intake pipe }. - L

\ | t

JJ L- 2

L

2

VQ Steel plates joined 

 by slotting each plate

DIMENSIONS for half its length. 

Baffle plates to be of such width -that they will fit 

snugly inside pipe. Length to be as shown in table.

Nominal diameter Length of baffle

of pipe L

2 6^2" Baffle to be fixed in

2^" 5 3/+ position with plates

3" 6" horizontal and vertical. 4" 1"

FIGURE 8. Design of Twitchell baffles for intake pipes of various sizes.

All the baffles were made of %-iiich metal and projected out of the 

pipe a distance equal to half their length. The proper length of these 

baffles as determined by tests for the various sizes of intake pipes (see 

table 9) are shown in figures 7 and 8.

INTAKES FOR GAGE WELLS 75 

OTHER DEVICES

Several of the other devices gave satisfoctory results and deserve 

mention because of certain desirable features in the individual designs. 

In the Eisenlohr intake box (see pi. 31, A, and fig. 9) the center of 

gravity of the device is in line with the axis of the intake pipe, and 

therefore there is no tendency for the device to turn from the position 

in which it is intended to be used. This device might be expected 

to receive considerable use except for the fact that it must be made 

from a special casting and requires machine-shop work in finishing. 

The Walworth strainer pointing downstream gave good results in the 

laboratory tests and, of course, can be readily purchased as a commercial product. The tests of the A models of flat plates that were 

intended to simulate the effects of a concrete pier flush with the end 

of the intake pipe and the tests of the circular plate attached to the 

end of the pipe indicated that the use of a vertical pier or plate at a 

clockwise angle of 5° with the direction of flow was effective in materially reducing the amount of draw-down. The merits of various other 

devices can be judged by reference to the tables showing their performance.

o