Selected Techniques 

in Water Resources 

Investigations, 1966-67

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1892
Selected Techniques 

in Water Resources 

Investigations, 1966-67

Compiled by EDITH BECKER CHASE and FAITH N. PAYNE

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1892

Papers on new techniques ,by C. F. 

Berkstresser, Jr., T. J. Buchanan, E. E. 

Cerny, E. D. Cobb, M. R. Collings, R. E. 

Cook, J. R. Crippen, L. C. Davis, Jr., 

B. Dunn, R. U. Grozier, L,. S. Hughes, 

A. I. Johnson, B. F. Joyner, T. E. Kelly, 

J. L. Kunkler, 0. J. Loeltz, S. E. Rantz, 

J. Rawson, IF. D. Robbins, V. B. Sauer, 

J. V. Skinner, K. V. Slack, G. F. Smoot, 

R. E. Sommer, Jr., H. H. Stevens, Jr., 

R. L. Stew art, J. D. Stoner, C. T. 

IFelborn, /. F. Wilson, Jr., IF. L. 

Yonts, Jr.

 JNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. GS 68-282

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price $1 (paper cover)
CONTENTS

Page 

Introduction..___.._._.____.-.____-_____-_-_-__-__-_----__-_-__-__ 1

Dye-tracing techniques general description._________________________ 2

Improved dyes for water tracing, by James F. Wilson, Jr_______________ 5

Nomographs for determining amount of rhodamine B dye for time-oftravel studies, by Bernard Dunn_ ___-__-_____--___-_---_---_-_-_-_ 9 

Constant-rate-injection equipment for dye-dilution discharge measurements, by Ernest D. Cobb__-_____-_-_-----_-_-_---_-_-_-_---_-_-_ 15 

Selection of dye-injection and measuring sites for time-of-travel studies,

by M. R. ColUngs...-------------------------------------------- 23

Comparison of results using three sampling techniques for a fluorometric

dye study in a stream, by J. D. Stoner_____________________________ 30

Comparison of flood-wave and water-particle traveltimes, by Thomas J.

Buchanan_ ____________-_________--__----_-_______-__--___-___-_ 34

Dye-cloud photography, by James F. Wilson, Jr_______________________ 37

A microkit for dissolved oxygen determination, by Keith V. Slack. _____ 44

Field kit for determining alkalinity, by J. L. Kunkler-_________________ 52

Rapid field filtration of water samples, by Charles F. Berkstresser, Jr____ 55

Field monitoring of the quality of water during the drilling of wells, by

Jack Rawson.______-_-____----__--__-___-___--____-______---__-_ 60

Sampling apparatus to minimize aeration of water collected at shallow

depths for the determination of dissolved gases, by B. F. Joyner_______ 67

Use of carbon dioxide in bubble gages to prevent precipitation of calcium

carbonate, by Wallace D. Robbins and Leon S. Hughes._-_-_-_______ 69

Polyethylene oil tubes for stilling wells, by Robert L. Stewart___________ 72

Water-manometer-air-line assembly for determining depth to water in

wells, by O. J. Loeltz____-_____-____-__-___-_-__-____-___-_______ 75

Miminum and maximum water-level recording devices, by T. E. Kelly_-_ 83 

Servopsychrometer, by Woodrow L. Yonts, Jr____________-__-_-_______ 87

Raft for evaporation-measurement equipment, by Richard U. Grozier_.__ 91 

Water-stage and rainfall dual recorder, by George F. Smoot and Thomas

J. Buchanan____________________________________________________ 94

Polar coordinate chart reader for stage-rainfall recorder, by V. B. Sauer__ 102 

Correcting river velocities measured from an unanchored ship, by Luther

C. Davis, Jr_-_----_-----_---_-----_-_-------------_---_---_---_ 109

Patterns of backwater and discharge on small ice-affected streams, by R.

Elton Cook and Edwin E. Cerny.___-_-_--___----_-_---_-_-___-___ 114 

Variable-speed power equipment for depth-integration sediment sampling,

by Clarence T. Welborn and John V. Skinner._-__-_-___-____---____ 126 

Electric control system for dual operation of current meter and suspendedsediment sampler, by Herbert H. Stevens, Jr., and Robert E. Sommer, Jr_________________________________________________________ 138

Characteristics of logarithmic rating curves, by S. E. Rantz_____________ 142

Interpretation of flood-frequency data, by J. R. Crippen and S. E. Rantz_ 153 

An outline of geophysical logging methods and their uses in hydrologic

studies, by A. I. Johnson.___--______----___-_________-_-_-_______ 158

in
SELECTED TECHNIQUES IN WATER RESOURCEf 

INVESTIGATIONS, 1966-67

COMPILED by EDITH BEOKER CHASE and FAITH N. PAYNE

INTRODUCTION

Increasing world activity in water-resources development has created an interest in techniques for conducting investigations in the field. 

In the United States, the Geological Survey has the responsibility for 

extensive and intensive hydrologic studies, and the Survey places 

considerable emphasis on discovering better ways to carry out its 

responsibility. For many years, the dominant interest in field techniques has been "in house," but the emerging world interest has led 

to a need for published accounts of this progress. In 1963 the Geological 

Survey published "Selected Techniques in Water Eesources Investigations" (Water-Supply Paper 1669-Z) as a chapter of the series "Contributions to the Hydrology of the United States." The report was 

so favorably received that successive volumes were planned. The first 

volume was "Selected Techniques in Water Resources Investigation, 

1965" (Water-Supply Paper 1822).

This, the second volume, contains 28 papers that represent new ideas 

being tested or applied in the hydrologic field program of the Geological Survey. These ideas, which cover a diversity of subjects, either contribute to the accuracy and ease of field operations or add to the basic 

knowledge of water resources. The original papers have been revised 

and edited by the compilers, but the ideas presented are those of the 

authors.

The general description of dye-tracing techniques on pages 2-4 has 

been given by the compilers as supplementary information to the 

several papers that follow.
DYE-TRACING TECHNIQUES GENERAL DESCRIPTION

For many years scientists have used natural or introduced materials 

as tracers to study mixing patterns and rates of movements within 

water bodies. Within the past decade soluble fluorescent dyes have 

proven to be excellent tracers and generally have replaced previous 

favorites such as chemical salts and radioisotopes. The dyes are economical, are easy to handle, and may be detected quantitatively in extremely low concentrations in water samples tested in P, special instrument called a fluorometer. Most of the dye-tracing work by the U.S. 

Geological Survey has had to do with time-of-travel measurements and 

and with discharge measurements by the dye-dilution methods. Other 

special applications by Survey scientists have served to demonstrate 

the versatility of dye tracing as a tool in hydrology. Eramples include 

studies of reservoir circulation and flushing, estuary flushing, welldrilling fluid-circulation time, ground-water time of travel, irrigationwater uptake by plants, and the fate of dye-tagged herbicides applied 

to water courses.

The object of a time-of-travel measurement is twofold: (1) to find 

out how long it takes a mass of water tagged with dye to travel downstream from one location to another, and (2) to determine how the 

stream dilutes and disperses the dye in the process. ThQ, dye generally 

is injected almost instantaneously as a slug; at downstream sites water 

samples are collected periodically or continuously and tested in a fluorometer for the presence of dye. Time-of-travel and dispersion information are then extracted from plots of concentration versus time (fig. 

1) for each sampling point. These data are used by water-management 

agencies to help solve problems involving undesirable contamination 

of streams, such as thermal loading from powerplsnts, accidental 

spills of chemicals, and sewage flushing and dilution. To date, the 

Geological Survey has measured time of travel on approximately 75 

streams, including the Mississippi and Missouri Eivers, in 30 States.

The dye-dilution methods of measuring discharge are useful primarily where it is difficult or impossible to obtain accurate measurements by conventional means. One method involves the downstream 

"total recovery" of a known quantity of dye injected as a slug; discharge is equal to the amount of dye injected divided by the average 

area under a set of time-concentration curves, like the one in figure 1, 

for the measuring cross section. Any loss of dye between the injection 

2
DYE-TRACING TECHNIQUES 3

and measuring sites decreases the accuracy of the measurement proportionally. A second method utilizes more sophisticated dye-injection 

apparatus to achieve a constant-rate injection over a continuous timespan ; at the measuring site the peak concentration is really a steady 

plateau of uniform concentration. In the constant-rate-injection 

method, discharge is simply equal to the rate of injection times the 

ratio of the injected concentration to the corresponding plateau concentration at the measuring site. Depending upon conditions in the 

stream, moderate dye loss with the constant-rate-injection method is 

less critical to measurement accuracy than with the total recovery 

method. In contrast to discharge measurements, dye loss usually does 

not seriously affect the results of time-of-travel measurements.

Although time-of-travel measurements usually involve reaches- that 

are many miles long and discharge measurements involve very short 

reaches, many of the field and laboratory procedures used for the two 

applications are similar. Seven articles, which cover a wide range of 

topics on the subject of dye tracing, are given in the present report.

Dye 

concentration

Time of 

injection

FIGUKE 1. Time-concentration curve for a specific sampling point in a channel cross section, illustrating some of the information which can be extracted : A, traveltirne of leading edge; B, traveltime of peak concentration; C, traveltime of centroid (considered to be the average travelfme 

of the dye to the sampling point) ; D, passage time at the sampling point; 

E, peak dye concentration, parts of dye per billion parts of water (prb). 

Similar information from curves for several sampling points is used to 

determine average values for the cross section.
4 TECHNIQUES, WATER RESOURCE® INVESTIGATIONS, 19'6'6-67

Some of the topics have general application in dye-tracing work, 

whereas a few apply to a specific type of study. The topics are presented in their natural sequence: dye selection (Wilson, p. 5), dose 

computations (Dunn, p. 9), dye-injection apparatus (Cobb, p. 15), 

field-site selection (Collings, p. 23), sampling systems (Stoner, p. 30), 

results of a special study (Buchanan, p. 34), and use of photography 

as an auxiliary tool (Wilson, p. 37).
IMPROVED DYES FOR WATER TRACING

By JAMES F. WILSON, JR.

ABSTRACT

Dye manufacturers are beginning to tailor the properties of certain fluorescent 

dyes for water-tracing purposes. Various solutions of rhodamine B are no^ available with specific gravities in the range 1.00 to 1.03. Rhodamine WT, a rew dye, 

exhibits low sorptive tendency and is proving to be an excellent tracer, especially 

for discharge measurements. Selection of fiuorometer filters appropriate to the 

particular dye used is a critical factor in instrument sensitivity.

INTRODUCTION

Hundreds of commercial dyes are available in a variety of colors. 

A great number of these are strongly fluorescent, but only a few are 

known to exhibit the combination of properties essential for water 

tracing. Generally speaking, tracer dyes must be (1) water soluble, 

(2) highly detectible by their fluorescence, (3) harmless in low concentrations, (4) inexpensive, and (5) reasonably stable in a normal 

surface-water environment.

Fluorescein, rhodamine B, and Pontacyl Brilliant Pink B1 are dyes 

that were available for other uses when modern dye-tracing techniques 

were first developed. Kecently several dye manufacturers have begun 

to improve some of these dyes such as rhodamine B and to envelop 

new dyes such as Ehodamine WT tailored to the tracing needs of 

oceanographers and hydrologists.

This paper describes the improved and new dyes, outlines the advantages and disadvantages of the four most commonly used dyes, 

and discusses the importance of using proper fluorometer filters.

RHODAMINE B

A simple, but basic improvement in the common solutions of rhodamine B (usually 30 or 40 percent by weight) has been the adjustment

1 Pontacyl Brilliant Pink B is a brand name of E. I. du Pont de Nemours & Co.; the same 

dye is also available from other manufacturers under different names. The use of brand 

names in this article for identification purposes does not imply official endorsemert of any 

product.

5
6 TECHNIQUES, WATER RESOURCE® INVESTIGATIONS, 19'66-67

of the specific gravity. Previous solutions were heavy and required 

premixing with methanol or similar liquid before injection of the 

dye, to prevent undesirable settling or stratification in the receiving 

water. For oceanographic tracing, solutions are now available at the 

specific gravity of sea water, approximately 1.03 du Pont Rhodamine 

BA, for example. For most fresh-water tracing 1.03 is low enough; 

rhodamine B solutions with gravities of 1.00 to 1.03 are available 

from a number of manufacturers. The reduction in specific gravity 

does not seem to have affected the cost of the dyes, nor to have changed 

the fluorescence properties of the dyes.

RHODAMINE WT

Rhodamine WT is a new dye, developed by du Pont especially for 

water tracing. As of this writing (1966) no equivalent dye is known 

to be available from other manufacturers. The principal advantage 

of Rhodamine WT is that it is far less susceptible tc sorption than 

rhodamine B. Because the fluorescence properties of the dye are similar 

(but not identical) to those of rhodamine B, the same fluorometer 

filters may be used. On the basis of detectibility with the 546 nut (millimicron) and 590 niju filters in the fluorometer, Rhodamine WT costs 

about twice as much as rhodamine B, but only about, one-fourth as 

much as Pontacyl Brilliant Pink B.

A disadvantage of Rhodamine WT is that it is available only in 

a 20 percent solution that has a specific gravity of 1.19; it is best to 

dilute it before injection into a stream or other water body. This dye 

has 'been used in the field extensively in recent months and has proven 

to be an excellent tracer.

COMPARISON OF DYES

The most important properties to be considered when selecting a dye 

are compared in table 1. An excellent general reference on the properties of the rhodamine family of dyes is Feuerstein and Selleck (1963) 

although it was written before the development of Rhodamine WT.

Rhodamine WT is recommended for discharge measurements or 

for any other application requiring a higji percentage recovery of 

dye. Pontacyl Brilliant Pink B (or equivalent) is a high-recovery 

dye but is not economical for large-scale use. Rhodamine B solutions 

with specific gravities of 1.00 to 1.03 are recommended for most stream 

time-of-travel measurements and estuarine dispersion studies, primarily because of the cost factor; lower recovery rates generally can 

be tolerated. Fluorescein is not recommended for surface-water tracing because it is quickly decomposed by sunlight. Fluorescein has the 

additional disadvantage of being difficult to isolate fluorometrically
IMPROVED DYES FOR WATER TRACING 7

in high-background waters. All the dyes in table 1, except rhodamine 

B, are recommended for ground-water tracing.

TABLE 1. Comparison of properties of four tracer dyes

[Rhodamine B and fluorescein are common industrial names; Rhodamine WT and Pontacyl Brilliant 

Pink B are E. I. du Pont de Nemours & Co. names]

Property Rhodamine B Rhodamine WT Pontacyl Brilliant Fluorescein

PinkB

Color index generic Basic Violet 10...... ..._---. ---...__..__. Acid Red 52....... Acid Yellow 73.

name.

Formula...-...--.-....- CssH^iNsOsCL---.-- ..................... CKHwNjOiSjNa.. CzoHizOs.

Common forms......... Powder; 30 and 40 20 percent solution.. Powder........... Powder.

percent solution.

Unit cost, ratio to 1--.-......---....... 2.................... 3......-------.-- . }$.

rhodamine B.

Cost ratio based on l.................... 2-...-....----------. 7..---.-....-...... ft.

detectibility.

Peak excitation wave 554-.--------------.. 558.--.-------------. 566..-------------- 480.

length, in millimicrons.

Peak emission wave 578.-...-........---. 582....----..-.--.- . 590-.-.-..-........ 510.

length, in millimicrons.

Detectibility 1 -...-...-. High.._-__.__.____.- High...--------.-... Moderately high.. High.

Tendency to be sorbed2 . ....do.............. Low ................ Low..-.....-..--. Low.

Sensitivity to tempera- ....do. .....----.... High..-..--.-.-.. --High--....--...... Do

ture. 3

Photochemical decay Moderately low..... Moderately low Low _..-----._...- Very h:.gh. 

rate. 4 (assumed).

1 Based on the use of the same set of fluorometer filters for all dyes except fluorescein. In add'fion it is 

more difficult to isolate the fluorescence of fluorescein from interfering background fluorescence.

2 Adsorption and (or) absorption by floating, suspended, and boundary materials in the receiving water 

body.

3 Fluorescence activity is decreased by higher temperatures and increased by lower temperatures.

4 The dyes decompose when exposed to sunlight.

NOTE. The fluorescence of all four dyes is stable over the pH range 5-10 and tends to decrease significantly 

outside these limits. Also, certain chemicals such as chlorine, if present in the receiving water, may destroy 

the dyes or cause significant reduction in fluorescence.

FLUOROMETER FILTERS

Rhodamine B, Rhodamine WT, and Pontacyl Pink (or equivalent) 

have nearly the same spectral properties, making them all highly 

detectible with the 546 nut and 590mju, fluorometer filters. Fluorescein, 

on the other hand, is spectrally different from the other three and requires different filters. Feuerstein and Selleck (1963, p. 3) used a Corning 7-83 filter for the primary and combination of Corning 3-70 and 

4-97 filter for the secondary (see Corning Glass Works, 1962); these 

filters were the basis for the detectibility comparison in table 1. G. K. 

Turner Associates (written commun., 1963) recommend a combination of Wratten 2A and 47B for the primary and a combination of 

Wratten 2A and 12 for the secondary (see Eastman Kodak Company, 

1965).

Because other dyes available now or in the future may be tried as 

tracers, attention to selection of proper filters is important. Filter 

selection should be based upon (1) the excitation and emission spectra 

of the particular dye tested, (2) the useful output spectrum of the 

exciting lamp, (3) potential interference from fluorescence of back-
8 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1^66-67

ground materials, and (4) potential interference from light scattered 

in the water sample. A particular new dye may require an entirely 

different set of filters from that used for rhodamine B. Failure to 

determine this in advance may result in false conclusions about the 

deteotibility, or even the presence, of the dye.

REFERENCES CITED

Corning Glass Works, 1962, Glass color filters: Corning, N.Y., Corning Glass

Works, catalog, 25 p. 

Eastman Kodak Company, 1965, Kodak Wratten filters for scientific and

technical use: Rochester, N.Y., Kodak Publication No. B-3, 77 p. 

Feuerstein, D. L., and Selleck, R. E., 1963, Fluorescent tracers for dispersion

measurements: Am. Soc. Civil Engineers Proc. Paper 358f, Sanitary Eng.

Div. Jour., v. 89, no. SA4, p. 1-21.
NOMOGRAPHS FOR DETERMINING AMOUNT OF RHODAMINE B DYE FOR TIME-OF-TRAVEL STUDIES

By BERNARD DUNN

ABSTRACT

Concentrations of dye are measured at a known distance below the point 

of injection to calculate the time of travel of a stream. The amount of dye 

required for injection into a stream needs to be computed in order to hold the 

level of concentration within desired limits and to minimize the cost of dye. 

Nomographs that permit rapid determination of the amount of dye required 

have been prepared for two of the formulas commonly used in dye studies.

INTRODUCTION

Three methods for determining the amount of dye to be injected 

into a stream are used by the U.S. Geological Survey in time-of-travel 

studies. They are a rule-of-thumb method as reported by Bu°,hanan 

(1964), an empirical formula by E. D. Cobb and J. F. Bailey (U.S. 

Geol. Survey, written commun., 1965), and a refinement of that 

formula by J. F. Wilson (U.S. Geol. Survey, written commun., 1966). 

In computing the amount of dye to be injected into a stream tr. e principal factor to be considered is dispersion. Because stream conditions 

contributing to dispersion are extremely variable, the formulas used 

are not exact.

The Geological Survey has adopted the policy that, at any point 

on a stream where water is removed for human consumption, the 

maximum concentration of rhodamine B dye shall not exceed 10 

ppb (parts per billion) by weight. Fluorometers are used to measure 

concentrations and, with available attachments and accessores, are 

sensitive enough to measure concentrations well below 1 ppb. The 

peak concentrations at the lower end of a reach, or at water intakes, 

can be computed for 1-2 ppb by weight and, even if the time of travel 

were underestimated, the prescribed limit of 10 ppb would unlikely be 

exceeded.

The field determination of the amount of dye needed to be injected 

into a stream can be time consuming and subject to computational 

errors. Use of the formulas has been simplified by constructing nomo9
10 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'6'6-67

graphs for the Cobb-Bailey and Wilson formulas. In both formulas 

the dye is rhodamine B, 40 percent by weight, specific gravity 1.03.

RULE-OF-THUMB METHOD

The rule-of-thumb method was used in early surface-water dye 

tracing experiments carried out by the Geological Survey (Buchanan, 

1964, p. 6). The amount of dye required was based en an estimate 

of the volume of water in the reach between the injection point and 

the sampling point. Experience has shown that an amount of dye 

required to produce a certain average concentration in tl is volume will 

produce a peak concentration at the sampling point of about double 

the average concentration. The Cobb-Bailey and Wilson formulas 

described in the next sections are based on much additional experience 

and are preferred in use.

COBB-BAILEY FORMULA

The amount of dye required for tune of travel in a reach by the 

Cobb-Bailey formula can be estimated from the empirical equation

where -¥d= volume of dye solution, in milliliters, to be injected

into the stream, 

(7j,=peak dye concentration, in parts per billion, desired

at the terminal site, 

Cd concentration, in parts per billion, of the dye

solution injected into the stream, 

Q= average discharge of stream, in cubic feet per

second, 

tp estimated tune in hours, for the dye peak to travel

from the injection point to the terminal site, 

and 3 X 10 7= combination of conversion factors.
NOMOGRAPHS, RHODAMINE B, TIME-OF-TRAVEL STUDIES 11 

WILSON FORMULA

The Wilson formula is a refinement of the Cobb-Bailey fcrmula 

and was based on time-of- travel data for a wide variety of stream 

conditions. The amount of dye required by the Wilson formula is 

expressed by

where -Fd = volume of dye solution, in milliliters, to be irjected

into the stream, 

j= coefficient equal to 0.06 divided by the dye solution

strength in ratio form (0.4 for 40 percent), 

Q.= average discharge of stream, in cubic feet per second, 

L= length of reach, in miles,

V= estimated average velocity of stream, in feet per second, 

and (7p=peak dye concentration, in parts per billion, desired

at the terminal site.

Wilson recommends that the amount of dye determined by his 

formula be doubled in the low-flow range (that flow which is equaled 

or exceeded more than 90 percent of the time) and quadrupled if 

there are small dams or long natural pools in the reach.

NOMOGRAPHS

Nomographs for the Cobb-Bailey formula (fig. 1) and for th<^ Wilson formula (fig. 2) were prepared for a rhodamine B dye concentration of 2 ppb at the terminal end of a reach. The nomograph for the 

Cobb-Bailey formula shows the relation of the dye solution and 

stream discharge, and the Wilson formula shows the relation of the 

ratio of the length of the reach to the velocity, stream discharge, and 

dye solution.

To determine the amount of dye solution from the nomograph for 

the Cobb-Bailey formula, the user must first determine the discharge 

and traveltime of the stream. For example, a stream lias a discharge
12 TECHNIQUES, WATEK RESOURCES INVESTIGATIONS, 19'6'6~67

of 10 cfs (cubic feet per second) and an estimated tn.veltime of 5 

hours. To determine the amount of dye from the nomograph, enter 

the abscissa of figure 1 at a discharge of 10 cfs and, v^here it meets 

the 5-hour line, read the ordinate as 7.5 ml. When either or both 

the discharge and time exceed that shown on the nomograph, reduce

20

10

O 

P 0.5

Q

LaCD

^ 0.2

0.1 I___I

10

AVERAGE DISCHARGE OF STREAM 

(Q), IN CUBIC FEET PER SECOND

FIGURE 1. Nomograph for Cobb-Bailey 

formula for determining amount of 40- 

percent rhodamine B dye solution for 

peak terminal dye concentration of 2 parts 

per billion, based on stream discharge and 

estimated traveltime of peak concentration.
L V

 ,100

NOMOGRAPHS, RHODAMIN1E B, TIME-OF-TRAVEL STUDIE? 13

Q

-nlOOO

10

^10,000

EXAMPLE:

1. L = 5 miles 

F = 0.2fps

L~ = -5 =25

V 0.2

2. Q = 50cfs

3. Place straightedge 

between known 

values of -4- and Q 

line

4. Answer: determine 

point of intersection 

with V, line

2 inches

 'o.i

1000

100

10

2 inches

0.1

 '1

100

10

FIGURE 2. Nomograph for the Wilson formula determining amount of 40-percent rhodamine B dye solution for a peak terminal dye concentration of 2 

parts per billion. L, length of reach, in miles; V, estimated average velocity 

of streams, in feet per second; ¥<i, volume of dye solution, in milliliters, to be 

injected into the stream; Q, average discharge of stream, in cubic feet per 

second.

312-670 O 68-
14 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'66-67

the values to fit the logarithmic cycle on the graph, and then obtain 

the volume of dye solution and multiply it by the same factors used 

to reduce the discharge and time values. For example, if the discharge 

is 100 cfs and the time 50 hours (the values of 10 cfs and 5 hours are 

each changed by a multiple of 10), it is necessary to multiply the 

7.5 ml by 100 (10X10) to get the actual volume (750 ml) of dye 

solution.

To determine the amount of dye solution from the nomograph for 

the Wilson formula involves three steps. First, the value for the L/V 

scale is determined by dividing known values of the length of reach 

and the velocity of the stream; second, the known value of stream 

discharge is indicated on the Q scale; and third, a straightedge is 

placed between the values on the L/V and Q scales. The point at which 

the straightedge intersects the ¥$ scale is the amount of dye solution 

needed. (See fig. 2.)

The use of nomographs in determining the amount of dye to be 

injected into a stream for time-of-travel studies has proven very helpful in the elimination of computational errors. If it is necessary to 

increase or decrease the peak concentration at the lower end of the 

reach, the volume of dye obtained from the nomographs can be 

adjusted readily.

REFERENCE CITED

Buchanan, T. J., 1964, Time of travel of soluble contaminants in streams: Am. 

Soc. Civil Engineers Proc. Paper 3932, Sanitary Eng. Div. Jour., v. 90, 

no. SA3, p. 1-12.
CONSTANT-RATE-INJECTION EQUIPMENT FOR DYEDILUTION DISCHARGE MEASUREMENTS

By ERNEST D. COBB

ABSTRACT

The measurement of stream discharge by the constant-rate-injection dyedilution method requires accurate injection equipment. Several units that use 

different principles and have different advantages have been developed. Constant flow rates of dye solution can be maintained by (1) a mariotte unit that 

maintains a constant head on the discharge orifice, (2) a spring-diaphragm unit 

that has an automatically adjusted spring-diaphragm-valve mechanism, (3) 

a floating siphon that maintains a fixed head on the orifice, (4) a constant-level 

reservoir that stores any solution above a given elevation, and (5) a constantrate pump that uses a uniform power supply. The mariotte tank is easily and 

cheaply made and is very reliable; the spring-diaphragm unit is more versatile 

but also more expensive; and the floating siphon, the constant-level reservoir, 

and the constant-rate pump all have the advantage that additional solution can 

be added to the supply reservoir without disrupting the flow rate.

INTRODUCTION

The accuracy of a stream discharge measurement using the constant-rate dye-injection method is directly dependent on the accuracy 

of the injection equipment used, as seen by examination of the discharge formula

where Q= stream discharge rate,

Ci= concentration of the injected dye solution,

C2 = concentration of the dye in the sampled stream water,

under equilibrium conditions, 

and g=discharge rate of the injected dye solution.

Injection rates that fluctuate slightly '(about ±2 percent) can be 

tolerated. However, an injection that changes rate in only one direction 

can yield serious errors in the measurement of discharge, which 

depend on the magn'tude of the change.

The purpose of this report is to describe several methods of obtaining constant-rate injections. No attempt is made to point out all 

the difficulties that might be experienced in the use of these various 

systems.

15
16 TECHNIQUES, WATER RESOURCES INVElSTIGATIOTTS, 19'6'6~-67

MARIOTTE UNIT

A mariotte unit is equipment that provides for a constant flow rate 

of dye solution into a stream by maintaining a constant head on the 

discharge orifice. (See fig. 1.)

The unit operates as follows: When the discharge orifice is opened, 

the level of the dye solution in the tank drops and causes a partial 

vacuum above the liquid. As the level of the liquid continues to drop, 

the vacuum increases and causes the level of the liquid in the air 

vent (which is open to the atmosphere) to drop until it reaches the 

bottom of the vent. As the solution continues to be dischr rged through 

the orifice, air enters the tank through the vent and causes an equilibrium between the partial vacuum formed above the liquid surface and 

the weight of the liquid above the bottom of the air vent. When this 

equilibrium has been reached, a constant discharge will have been 

attained and will continue until the liquid in the tank drops to the 

bottom of the air vent. In practice it has been found that as much as 3 

minutes may be required for complete equilibrium to be obtained. 

During this initial period, higher flow rates will exist as a result of a 

greater head acting on the orifice.

The flow rate can be controlled by the orifice size, the position of the 

lower end of the air vent (if the air vent is raised, the head is increased; 

however, the usable volume of solution is then decreased), the position 

of the discharge point of the orifice, valves in the orifice, or clamps

Hollow air-vent tubex

Airtight filler cap,

Airtight cork with 

hole in center for 

^air-vent tube

\

Head on 

orifice T ^

r L

Dye-solution

Reservoir 

for dye 

solution

 Orifice

r 

surface

* Tapered 

end

FIGURE 1. Sketch of the mariotte unit.
INJECTION EQUIPMENT FOR DYE-DILUTION MEASUREMENTS 17

on flexible tubes leading from the tank orifice. The latter two are the 

least desirable as they tend to trap sediment or cause bubbles to form 

in the discharge line. Once a flow rate is established, all parts of the 

unit should be left unmoved during the measurement.

Flow rates are usually determined by measuring the time required 

for the flow to yield a specific volume. Usually a graduated laboratory 

cylinder and a stopwatch are adequate for this purpose. If the unit 

has a graduated readout tube, the tank can be volumetrically calibrated 

and discharges determined by timing the period for the liquid to drop 

a specific distance in the tube. The unit can also be hung on a scale 

which in turn is hung from a tripod or a tree, and the discharge can 

be determined by taking scale readings and the time interval between 

readings.

Experience has shown that air in some water will cause bubbles to 

build up in the orifice or discharge line and disrupt the steady flow 

of solution from the tank. Small amounts of laboratory detergent (1 

part of liquid Liquinox detergent, or equivalent, in 100,000 parts of 

solution) in the dye solution have been found to reduce or eliminate 

this problem. Sediment or impurities in the dye or water used in the 

solution have been found at times to clog the orifice. The size of orifice 

being used and the purity of the water and dye determine the necessity 

of filtering the dye solution before pouring it into the mariotte tank. 

The dye solution should be thoroughly mixed before it is poured into 

the tank.

The dye-solution tanks have been clear plastic containers, 5-gallon 

water cans, 50-gallon drums, small pieces of clear plastic pipe, and 

containers of specially prepared material. Clear plastic has the advantages of allowing the operator to see how the unit is functioning 

and what the level of the solution is in the tank. Materials used should 

be rigid enough to withstand the air-pressure differential that results 

in the unit; they also should be rust resistant and easily cleaned.

The lower tip of the air-vent tube should be tapered to prevent the 

tip from being placed directly on the bottom of the tank and thus 

obstructing the air flow.

Discharge at more than one point or at different rates may be facilitated by installing more than one orifice in the tank.

Many modifications can be made to the manufacture of the unit as 

long as there is adherence to the operating principles.

SPRING-DIAPHRAGM UNIT

The spring-diaphragm unit maintains a constant flow rate by means 

of an automatically adjusted spring-diaphragm-valve mechanism. A
18 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 19-66-67

unit that meets the requirements for measuring streamflow is manufactured by Aerofeed, Inc., Chalfont, Pa. (See fig. 2.)

The features of the unit are shown in figure 3. Power to operate the 

unit is derived from compressed air in the storage tank. A foot pump 

can be used to pressurize the tank. The pressure forces the solution 

out of the tank, through the flow meter, through the flow-control assembly, and into the stream.

The flow-control or regular assembly on the unit will regulate the 

flow within ±2 percent of the set discharge as long as a pressure difference of about 5 pounds per square inch or greater is maintained 

between the inflow to and the discharge from the regulator. Basically, 

the regulator functions to maintain a constant differential pressure 

across an externally adjusted orifice regardless of the manner in which 

the absolute pressures, either upstream or downstream from the orifice, 

may change. Because the size of the orifice is fixed for any given 

position of the adjustable needle valve (fig. 4), maintenance of the 

constant differential pressure across it assures maintenance of a 

constant flow rate through it.

A sketch of the flow-control assembly is shown in figure 4. The flow 

enters from the bottom of the unit. A passage from the flow entrance 

to the lower pressure chamber allows the tank pressure (less pressure 

losses) to exert a force upward on the underside of the diaphragm. 

The solution flows through the adjustable needle valve into the upper 

pressure chamber above the diaphragm where it exerts a force downFIGTJBE 2. Aerofeed constant-rate-injection unit.
INJECTION EQUIPMENT FOR DYE-DILUTIO'N MEASUREMENTS' 19

A

Filling cap

Air-pressure 

gage

Air valvePump connection

Storage tankv^^

Plastic base

Flow regulator

Lugs for carrying 

handle

Discharge tubing

Flow meter Filter flow-back 

connection

V- filter (inside tank)

FIGURE 3. Sketch of the Aerofeed unit. A, Tank and its components; 

B, cross section of flow meter.

ward on the diaphragm. This latter force is less than that unc'erneath 

the diaphragm because of a reduced effective diaphragm area, friction 

losses, and pressure losses due to bends, contractions, and expansions, 

but primarily because of the loss of pressure resulting from the solution flowing through the control orifice. A spring also pushes down on 

the diaphragm exerting an additional constant force. It is this constant 

force, exerted by the spring, which determines the pressure maintained 

across the needle valve.

When liquid starts to flow through the regulator, an equilibrium 

condition is rapidly established between the forces acting upward on
20 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

Spring 

Valve stem

Diaphragm 

Lower pressure 

chamber

Adjustable needle 

valve

Upper pressure 

chatiber

Inflow

FIGURE 4. Cross section of the Aerofeed flow regulator

the diaphragm (pressure only) and those acting downward (pressure 

plus spring). At this equilibrium condition the internal valve will have 

been driven to some particular position with respect to the control orifice by the action of the spring and the flexible diaphragm. The higher 

the tank pressure (all other things being equal), the further the valve 

will enter the control orifice.

When the tank pressure decreases, two events occur simultaneously: 

(1) the pressure underneath the diaphragm decreases, reducing the 

upward acting force, and (2) the flow through the needle valve decreases, owing to the decreasing upstream pressure. At this momentarily decreased flow rate through the needle valve, the pressure drop 

across the valve is reduced, thereby increasing the pressure above the 

diaphragm and, accordingly, increasing the downward acting force. 

This combination causes a momentary loss of the original pressure differential between the two chambers and causes the diaphragm to 

deflect downward a short distance. As the diaphragm iroves down, it 

causes the valve to withdraw slightly from the control orifice, which 

thereby permits flow through the regulator to increase. As the flow 

increases, the pressure drop across the needle valve also increases, 

which thus decreases the force acting downward and slows the downward deflection of the diaphragm until an equilibrium position is once 

more obtained.

Because tank pressure slowly but steadily drops during normal 

operation of the injection unit, the positions of the valve and diaphragm are also constantly changing, always drawing the valve 

further and further out of the control orifice, but always maintaining 

a nearly constant difference in pressures above and below the diaphragm. If tank pressure were to increase, the directior of the valve
INJECTION EQUIPMENT FOR DYE-DILUTION MEASUREMENTT 21

and diaphragm movement would be reversed but the unit would still 

seek equilibrium and maintain the flow rate.

The rate of flow is set by turning the needle-valve control liiob to 

the desired position. The regulator will maintain constant flow rates 

for discharges of about 25 to 230 inilliliters per minute.

The material used in the diaphragm does not allow the regulator 

to regulate properly for about the first 3 minutes of operation. Volumetric calibrations of the flow rate should not be made during this time.

The flow meter is used to determine approximate flow rates- and is 

used for initially setting the discharge rate. Actual flow rates must 

be determined by volumetric measurements of the discharge. The meter 

has a linear scale from 0 to 100 and must be rated by volumetric 

measurements at various needle-valve settings. This meter rating 

should be nearly linear. The meter is read by determining the position 

of a ball in the meter tube. As the flow rate increases, the ball rises in 

the tube.

The advantages of the unit are (1) flow rates can be regulated over 

a wide range, (2) low flow rates can be obtained, (3) the unit is portable 

(it is about 17 inches in height and when empty weighs only about 11 

pounds), (4) it has adequate storage (3.14-gallon total-tank volume) 

for solution to allow measurement of most streams than can be efficiently measured by this method, and (5) no special provisions have 

to be made for setting it up at the measurement site.

The primary disadvantage of the unit is that it is more expensive 

than most of the other units.

FLOATING SIPHON

The floating siphon maintains a constant flow rate by mair taining 

a fixed head on the orifice. Figure 5 is a sketch of the equipment.

The float and orifice drop together as the solution flows out of the 

storage tank. Because the orifice is then kept at the same elevation 

relative to the solution surface, the flow is maintained -at a constant 

rate. A counterweight and pulley wheel are used to keep the float in 

place near the side of the tank.

Sharp bends, sharp or rough entrance conditions, and constrictions 

in the siphon might cause air to come out of solution and form r, bubble 

at the top of the siphon. These conditions should be avoided if possible 

because a bubble will reduce the area and the flow rate. The use of 

water that has been allowed to stand at atmospheric pressure and 

temperature will help prevent this bubble formation. A clear plastic 

siphon will enable the user to see if a bubble forms.

The use of a tube which can be attached to the end of the orifice will 

enable the user to draw the solution through the siphon, at which time
22 TECHNIQUES, WATEK RESOURCES INVESTIGATIONS, 19'6'6-67

Constant 

head

Counterweight

. Siphon tube

Pulley wheel

Float

Dye-solution

surface

vRounded entrance

Dye-solution reservoir

FIGURE 5. Sketch of the floating siphon.

the tube can be detached and the solution will continue to siphon out 

of the tank.

A primary advantage of the floating siphon is that dye solution can 

be added to the storage tank without disrupting the flow rate; hence, 

the dye solution can be injected into the stream for long periods of time. 

A disadvantage is the lack of portability of the system.

OTHER CONSTANT-RATE FLOW UNITS

Several other methods may be used to obtain constant flow rates. 

The constant-level reservoir is one such method. This unit requires 

three tanks: the first tank drains dye solution into a second tank, which 

is the constant-level reservoir and is constructed so that any solution 

above a given elevation discharges over a wide weir into a third tank 

for storage. The weir should be wide enough and the orifice in the 

constant-level reservoir at such a depth that a slight variation in inflow 

to this tank will cause negligible changes in the head anc1 thus in the 

flow rate.

Another device is a constant-rate pump. A uniform poAver supply is 

necessary to assure constant flow rates. Other more sophisticated units 

are available but are not described herein.
SELECTION OF DYE-INJECTION AND MEASURING SITES 

FOR TIME-OF-TRAVEL STUDIES

By M. R. COLLINGS

ABSTRACT

Studies using fluorescent dyes for estimating time of travel in stream^ may be 

made by either a single-injection method for the entire study reach or a multipleinjection method whereby the study reach is divided into subreaches. The 

method used is governed by the specific prerequisites of the study, time and 

personnel limitations, and other factors.

The optimum success of a study depends upon proper selection of dye-injection 

and measuring sites. Site selection should be made after a comprehensive inventory of the study reach. Factors to be evaluated include channel characteristics 

of the stream, potential loss of dye, municipal demands, tributary inflow, and 

stream discharge.

INTRODUCTION

The importance of examining the study reach prior to inauguration 

of a fluorescent dye time-of-travel study cannot be overemphasized. 

Every stream has features that must be evaluated properly if the 

traveltime study is to be completely successful.

This article compares two methods of dye injection and presents 

factors to be considered in selecting dye-injection and measuring sites 

for time-of-travel studies. The dye injected by these methods may be 

affected to some extent by channel characteristics of the stream, potential loss of dye, municipal demands, tributary inflow, and stream discharge. Factors are discussed for selecting injection points that will 

minimize dye loss and thus maximize dye recovery.

DYE-INJECTION METHODS

Fluorescent dye time-of-travel studies on a stream can be efficiently accomplished by either a single-injection method or a multipleinjection method. The single-injection method is accomplished by 

injecting the dye at the upper end of the study reach and sampling 

for fluorescence at selected measuring sites downstream. The multipleinjection method consists of dividing the total reach into subreaches 

and injecting dye at the head of each subreach either at the sr,me time 

or in upstream order.

23
24 TECHNIQUES, WATEK RESOURCES INVESTIGATIONS, 196'6-67

SINGLE-INJECTION METHOD

Some of the features of the single-inject!on method are:

1. Continuity of data. Simulation of pollutant behavior over the 

entire study reach makes the method ideal for reconnaissance 

investigations.

2. Simplicity of planning. The method requires selection of only one 

injection point at the upper end of the reach and of dye-sampling 

sites downstream.

3. Number of personnel needed. To define time-concentration curves 

adequately, several sites may require sampling 'at the same time. 

The frequency of sampling sites, the length of subreach dosed, 

and the stream discharge determine whether the single-injection 

method will or will not require fewer personnel thai, the multipleinjection method.

4. Off-scale fluorescence. A large amount of dye is required in a large 

stream, in a stream at high flow, or in long study reaches. Under 

these conditions, a dye-sampling point near the injection site 

may have greater fluorescence than can be recorded by the fluorometer used to detect fluorescence. This problem may be rectified 

by removing the high-sensitivity kit from the fluorometer, diluting the sample, or placing a neutral density (range-extension) 

filter over the secondary filters in the fluorometer. 

Usually the use of the less sensitive filter combination in the fluorometer is the simplest way to obtain a reading, although a calibration 

of the instrument with the neutral density filter in place is necessary 

to evaluate the reading in terms of concentration (parte per billion). 

When using either the single- or multiple-injection method, the 

circumstances govern whether off-soale fluorescence will result. However, usually the first measuring site in the reach can be placed far 

enough downstream (in relation to discharge) from the injection site 

so that the dye will be sufficiently diluted.

MULTIPLE-INJECTION METHOD

The multiple-injection method may be accomplished in either of two 

ways: The simultaneous injection of all subreaches or th°> injection of 

each subreach in upstream order. Some features of the simultaneous 

injection are:

1. Reduction in time required to complete the traveltime study. The 

time required for completion would be only as long as the time 

required for the longest (timewise) subreach.

2. Personnel and communication problems become manifold. All subreaches require simultaneous sampling, often at more than one 

site in each.
SELECTION OF SITES FOR TIME-OF-TRAVEL STUDIES 25

3. Dye slugs may overlap. The sampling point at the end of a subreach, by necessity, is also the injection point of the next lower 

subreach and there is a possibility of dye slugs overlapping. 

However, this seems to be the exception rather than th<^ rule. 

Some features of injection of each subreach in upstream order are:

1. The natural fluorescence of each subreach is insured (also the 

case with single-injection), and there is no possibility of d^e slug 

overlap.

2. Fewer sites require sampling at the same time; therefore- fewer 

personnel are needed.

3. The time required to complete a particular study is increased.

Several advantages common to both variations of the multipleinjection method are:

1. Dye concentrations can be minimized at water intakes and other 

sites where there is a definite need to do so. The U.S. Geological 

Survey's Water Resources Division has a policy whiclx states 

that the maximum dye concentration at such sites must be less 

than 10 parts per billion by weight.

2. Effects of changes in river stage during the study are minimized 

or at least identified.

3. A more thorough understanding of contaminant inflow at points 

located within the total reach is obtained. The stream may be 

dosed at the sites of contamination and the dye may be sampled 

at critical points downstream.

4. The dye cloud is less likely to become so dispersed that d°*tection 

is difficult and (or) peaks, centroids, or time of dye passage are 

difficult to determine. This is especially true if storage, such as 

lakes or reservoirs, exists in the study reach.

FACTORS TO CONSIDER IN SITE SELECTION

Many factors enter into selection of dye-measuring sites for the 

single-injection method or dye-injection and measuring sites for the 

multiple-injection method. Every study reach is unique in sone way; 

however, the following description of the effects of some of these 

factors channel characteristics of the stream, potential loss of dye, 

municipal demands, tributary inflow, and stream discharge will aid 

in the selection of injection and measuring sites.

CHANNEL CHARACTERISTICS OF THE STREAM

Generally, the steeper the stream gradient, the faster the velocity 

and the shorter the time of travel through the reach. Therefore, dyemeasuring sites may be spaced farther apart on streams with steep 

gradients.
26 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

The channel lithology should be considered when selecting measuring sites. Fluorescent dyes may be partly or almost totally lost through 

channel sorption. When dye studies are conducted on streams with sorbent channel materials, such as clay, silt, and sand, the measuring 

sites should be spaced more closely and the progress and concentration 

of the dye checked as often as feasible. Additional motion points 

may be selected if the dye is lost. Cobble, boulder, or bee1 rock channel 

materials generally do not pose this problem.

During periods of sustained low flows, aquatic vegetation may become well established in stream channels. Parts of an nrected slug of 

dye are delayed by eddies caused by aquatic vegetation. At dyemeasuring sites downstream, delays caused by passage of the dye slug 

through these vegetated and swampy areas may cause multiple peaks 

or, at least, broad peaks of low concentration.

Reservoirs, lakes, and ponds in a study reach warrant special consideration for time-of-travel studies. A storage area mar cause broad 

low-concentration dye peaks downstream or even multiple peaks 

similar to those shown in figure 1. The peaks depend on the size and 

regulation of the reservoir. The time of travel through a waterstorage area, whether natural or manmade, is as important as the time 

of travel in any part of a river reach, and every effort should be made 

to obtain data through these sections of the river. However, the passage of dye through a very large storage area may be so complex that 

the area should be bypassed and studied separately at a later date.

Hockanum River, Conn., 

Main St.Bridge, East Hartford

0.8

1700 2200 0300 0800 1300 1800 2300

TIME, IN HOURS

0400 0900

FIGURE 1. Time-concentration curve at a dye-measuring point below a dam.
SELECTION OF SITES FOR TIME-OF-TRAVEL STUDIES' 27

POTENTIAL LOSS OF DYE

In addition to natural dilution, which ultimately renders the dye 

undetectable, the dye is subject to a number of physical and chemical 

processes which tend to diminish the amount detected at a measuring 

site. The most important of these processes are sorption, chemical 

action, and photochemical decay.

The percentage of dye loss in most cases is not great enough to 

cause serious measuring problems in time-of-travel studies. However, 

adequate dye should be injected to provide a measurable reading at 

the most remote sampling site, despite losses. For example, in a 

measurement of traveltime on the Mississippi Eiver by the Water 

Eesources Division of the Geological Survey (Stewart, 1967), 72 percent of a 4,100-pound dose of rhodamine B dye, 40-percent solution, 

was recovered 21 miles downstream 14 hours after injection, and 52 

percent was recovered at 126 miles after 93 hours. The discharge was 

240,000 cubic feet per second. If the river had been dosed to obtain a 

minimum measurable dye concentration at the 126-mile site without 

regard to losses, a 52-percent loss at that point may well have rendered 

the dye undetectable.

High concentrations of sediment or organic material may reduce the 

peak dye concentration before it reaches the sampling site. Laboratory 

tests on 40-percent solutions of rhodamine B dye have shown as much as 

12-percent dye loss after 4-hour contact with sand and as much as 28- 

percent dye loss after 2-hour contact with an organic material (Wright 

and Collings, 1964). In north-central Massachusetts, a sample of river 

water contaminated by papermill wastes was taken 3 miles below a gaging station (Otter Eiver at Otter Eiver) and tested for dye recovery. 

Almost instantaneously, 13 percent of the dye was not detectable, 

after 24 hours 25 percent was lost, but after 48 hours the contaminant 

in the sample had decomposed and the concentration returned to the 

initial prepared concentration.

The dyes also are susceptible to destruction or reduced fluorescence 

due to reaction with other chemicals present in the stream. Chlorine, 

for example, is very destructive. Where materials of this nature are 

known to be present, injection and measuring sites should b located 

accordingly.

The loss of dye by sorption and (or) chemical reaction may be 

partly or wholly remedied by selecting a fluorescent dye Ehodamine 

WT, for example that is less sorbed than other dyes, by increasing 

the amount of dye injected, or by selecting the injection sites at shorter 

intervals along the reach. If large dye losses are expected, stream 

samples may be collected prior to dosing and known dye concentra-
28 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'66-67

tions may be prepared and tested with the fluorometer to obtain an 

estimate of the magnitude of the lose.

Some types of extraneous matter such as algae or detergents may 

also cause a variable background fluorescence (fluorescence of the 

water in the stream before dosing) and may mask peaks or even cause 

multiple peaks. It is always recommended that a good definition of 

background be obtained at a measuring site before the stream is dosed 

or at least before the dye slug has reached that site.

Photochemical decay is caused by the reaction of the dye to sunlight 

and is a function of time exposed. The reaction results in a reduction 

of dye fluorescence and, if necessary, may be minimized by shortening 

the length of the subreach. The loss by photochemical decay is probably 

a minor problem for most traveltime studies when compared with the 

other causes of dye loss. However, samples should be stored in a dark 

place and tested as soon as possible.

MUNICIPAL DEMANDS

Domestic or industrial facilities may be concerned w; th the time it 

takes a pollutant from an upstream source to reach their intakes and 

they in turn also may be the source of contaminants to the stream. 

Therefore, municipalities should be inventoried for possible injection 

or measuring sites to help determine the time of travel to their water 

intakes from upstream pollution sources and (or) the dilution 

characteristics of the river on material from their outf all?

TRIBUTARY INFLOW

Dye-measuring points directly below tributaries should be selected 

with care because these tributaries may be contributing pollutant to 

the main stream and mixing of the main stream and the tributary 

may not occur immediately. Because of poor selection of a cross-sectional sampling position on the river, dye samples may indicate inconsistent 

fluorescence, or the peak may not be sampled at all. Several locations 

in the cross section should be sampled whether immediately below a 

tributary or not.

STREAM DISCHARGE

For a comprehensive time-of-travel evaluation, dye studies should 

be made at a high, medium, and low stage of the stream. Enough 

information should be obtained to formulate the relation between 

discharge and traveltime. During an individual time-of-travel 

measurement, the discharge should remain relatively constant at the 

downstream end of the reach. If the flow changes significantly during 

a study, the characteristic time of travel for that particular flow 

will not be obtained; therefore the investigation of a stream reach
SELECTION OF SITES FOR TIME-OF-TRAVEL STUDIES 29

should be completed as quickly as possible. The longer it takes to 

make a particular study, the greater the probability that a change in 

flow will occur.

Even if discharge is steady, conditions may dictate the number 

and location of injection and sampling sites. Under extreme low-flow 

conditions, stream velocities may be so slow that the study reach has 

to be subdivided in order to complete the study in a reasonable time. 

This has often been the case. On the other hand, under high-flow conditions, high stream velocities may force the use of a single-injection 

site and widely spaced measuring sites.

SUMMAEY

Before a time-of-travel study is started, the stream under investigation should be thoroughly inventoried. The number and location 

of injection and measuring points should be chosen with care. Consideration of channel characteristics, potential loss of dye, municipal 

demands, confluence of tributary streams, and stream discharge is 

essential for any fluorescent-dye study. Estimates should be made of 

the effects of sorption, chemical reaction, and photochemical de^ay in 

order to determine the size of the most efficient dose of dye to inject 

at a particular site. Ideally, both one-dye injection for the total reach 

and several injections on selected subreaches would be desirable. However, for economic reasons, usually either one dose or several doses 

are made; rarely are both methods used on one river study reach. The 

number of injection and measuring sites selected for a study reach depends on how comprehensive a study is needed; for example, much 

less data would be needed for a reconnaissance type study than for the 

solution of a particular pollution problem.

EEFEEENCES CITED

Stewart, M. R., 1967, Time of travel of solutes in Mississippi River from Baton 

Rouge to New Orleans, La.: U.S. Geol. Survey Hydro'1. Inv. Atlas FA-260.

Wright, R. R., and Collings, M. R., 1964, Application of fluorescent tracirg techniques to hydrologic studies: Am. Water Works Assoe. Jour., v. 56, no. 

6, p. 74S-754.

312-670 O 68-
COMPARISON OF RESULTS USING THREF SAMPLING 

TECHNIQUES FOR A FLUOROMETRIC DYE STUDY IN A 

STREAM

By J. D. STONEB

ABSTRACT

Three sampling techniques grab samples and two different pumping systems were tested concurrently at a single point in a streair. The means and 

variances computed for the three sampling methods are shifted from the true 

means and variances by various time increments. Generally, sampling points 

along a stream in a time-of-travel or dispersion study are far enough apart to 

make the error shift insignificant, <so that results from different sampling 

methods are directly comparable. However, some studies require that correction factors be applied to the means and variances.

The use of fluorescent dyes as tracers in dispersion and time-oftravel studies is becoming more prevalent. In any dye rtudy, the water 

in the stream must be sampled in some manner, and the use of more 

than one sampling method in a single time-of-travel or dispersion 

study may be desirable. At a given sampling point the mean of the 

distribution of dye concentration versus time is used to determine time 

of travel, and the variance, to evaluate dispersion. The tests discussed 

below were made to compare the means and variances computed from 

the data obtained by three different sampling techniques. The work 

was performed on the Green-Duwamish River, Wash., in cooperation 

with the municipality of Metropolitan Seattle.

The techniques used in this study were (1) a portable pumping system, (2) a permanent pumping system, and (3) grab sampling. The 

three techniques were used concurrently at a single test site. The grabsample site and pump intakes were located as near to each other as 

practical, thus minimizing differences in dye concentration due to 

horizontal and vertical velocity variations in the stream. For this 

study, the length of hose used in the portable pumping system was 

made equal to that of the pipe installed in the permanent pumping 

system.

Each continuous pumping system had a Turner Model 111 fluorometer equipped with a flow-through door and a recorder. The 

recorder produced a continuous trace of fluorometer urits versus time. 

30
THREE SAMPLING TECHNIQUES, FLUOROMETRIC DYE STUDY 31

Just prior to starting the study, the fluorometers were calibrated with 

appropriate dye standards. These standards were prepared immediately before use by diluting measured quantities of dye with measured quantities of stream water. After calibration, background fluorescence was measured on each of the four sensitivity ranges or each 

fluorometer. The dye, rhodamine B, was injected into the stream about 

2 miles upstream from the study site.

The main components of the portable pumping system were a Jabsco 

Model 11810 pump and plastic garden hose (^-inch inside diameter). 

A valving system to control the flow through the fluorometer was 

used in the pumping systems.

Multiparameter water-quality monitors equipped with permanent 

pumping systems had been installed at four points along the study 

reach. One of these permanent installations was used for the second 

sampling technique, which consisted of a submersible pump suspended 

from a float in the stream and a 11,4-inch inside diameter polyvinyl 

chloride pipe that led to the monitor.

The third technique was grab sampling from a highway bridge at 

the test site. The samples were collected in 16-ounce bottles, er.ch of 

which contained 1 milliliter of a detergent solution to minimize adsorption of the dye on the glass. The grab samples were analyzed in a 

fluorometer immediately after the pumping systems were shut down.

Eeadings obtained from the fluorometers were converted to concentrations of rhodamine B, expressed in parts per billion, in order 

to compare the three sampling techniques. A common time base was 

used for the three methods, and smooth concentration-versus-time 

curves were drawn (fig. 1).

Two problems were experienced during construction of the concentration-versus-time curves. First, the curve based on grab samples 

peaked at a slightly lower concentration than the curves constructed 

from the continuous-trace measurements. The actual peak concentration was apparently missed, although the grab samples were tal'en at 

frequent intervals. The difference in maximum concentrations (3 percent) and the periods between grab samples (2 minutes) were so small 

that the mean time is virtually equal to the value that would have 

been obtained had the actual peak been observed. Second, the f Morometric chart trace of the portable pumping system was driven off scale 

during a short part of the dye passage. An estimation of the missing 

segment was made, based on characteristics of this type of curve and 

previous data obtained at this station.

Curves developed from time-of-travel and dispersion data commonly 

exhibit very long "tails" after passage of the main body of the tracer. 

The significance of these tails with respect to time of travel or disper-
32 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

401 i i i I i 

30

| 20

3

o

I

01

10

Permanent pump

Portable pu mp 

(dashed where 

estimated)

10 20 30 40 50 

TIME, IN MINUTES AFTER ARBITRARY ZERO TIME

60

FIGURE 1. Comparison of concentration-versus-time curve? for three

sampling techniques.

sion is not completely understood. Long tails have a noticeable effect 

upon the computation of the means and, especially, the variances of 

the curves. For this study, only the first YO minutes of data after time 

zero (fig. 1) was used in the calculations of the means and variances. 

Beyond this time the curves are believed to be dependent upon such 

things as dye sorption by sediments and slow dye release from areas 

of slack water, rather than dispersion due to stream velocities.

Means for the grab samples, the portable pumping system, and 

the permanent pumping system were 26.Y, 28.1, and 30.4 minutes from 

time zero, respectively. Thus, the use of various sampling methods 

yields various means for the same time of travel. A rough laboratory 

study using the portable pumping system indicated that the required 

pump-through time was comparable to the time shift from the grabsample mean.

In most time-of-travel studies, sampling sites are far enough apart 

to require several hours or even days for travel of the dye cloud
THREE SAMPLING TECHNIQUES, FLUOROMETRIC DYE STUDY 33

from station to station. Under such circumstances, even a 10-minute 

error would not be significant in determining the time of travel. 

However, where stations are close together, or traveltime is short, 

errors of 2 to 5 minutes may be significant. In such a situation, the 

data from the various sampling methods should be corrected for 

displacement of the mean.

Unless the sampling system used provides in situ measurements of 

concentration, it will bias the true mean to some degree. However, if 

one sampling method is chosen arbitrarily as a standard, as grab sampling was in this report, reduction of the time shift of other systems 

to that of the standard systems should be relatively simple. Time of 

travel is normally computed as the difference of means between stations. If all time shifts are corrected to standard values, and time of 

travel is computed by difference, then the resultant computation should 

be the true time of travel.

Variances for the grab samples and the portable pumping and 

permanent pumping systems were 54.93, 63.89, and 63.69, respectively. 

A statistical analysis showed that the variances for the three sampling 

techniques were equal at the 10-percent level of significance. In dispersion studies where the variance is needed to compute the dispersion 

coefficient, the various techniques of sampling that can be utilized 

must produce equal variances if used concurrently at the sane test 

point. For most longitudinal dispersion studies, equality at the 10- 

percent level of significance should be adequate. In lateral or vortical 

dispersion studies, in contrast, equality of variances at the 10-p3rcent 

level of significance may not be adequate. The use of only one sampling 

system would perhaps be necessary in these studies.
COMPARISON OF FLOOD-WAVE AND WATER-PARTICLE

TRAVELTIMES

By THOMAS J. BUCHANAN

ABSTRACT

By applying the Manning and Chezy formulas, the ratio of the velocity of a 

flood wave to the mean velocity of water particles is shown to be between 1.3 

and 1.7. The results of an actual study with a fluorescent dye in an open channel 

to determine the ratio show good agreement with the expected ratios in channel 

reaches without dams, but reaches with dams give ratios greater than 2.0.

Hydrologists have long been interested in the relation between the 

velocity of a flood wave in an open channel and the mean velocity of 

water particles in the same reach of the stream. In the past, valid data 

for these comparisons were almost unobtainable because of the difficulty of denning the mean velocity of the water particles in nonunif orm 

reaches. The time-of-travel techniques discussed previously have made 

it possible to determine the traveltime of the water particles in such 

reaches and, thereby, to determine the mean velocity of the stream, in 

the study reach.

The application of the Manning and Chezy formulas (Rouse, 1950) 

for different types of stream channels allows the determination of the 

expected ratios between the velocity of a flood wave (vw) and the 

mean velocity of the stream ( V) . Ratios of velocity of flood wave to 

mean velocity of stream for three types of channels are:

Ratio e*lV

Channel type 

Triangular _ __. __ _ ____ _ __ ______

Wide rectangular ____ __ _ ______

Wide parabolic. _____ ____

Manning 

formula

________ 1.33

--__.___ 1.67

________ 1.44

Chezy 

formula

1.25

1.50

1. 33

By these methods, the velocity of a flood wave is calculated to be

between 1.3 and 1.7 times as great as the corresponding mean velocity.

One practical application of this relation is in the field of water

supply. Consider the release from a reservoir of good-quality water

which will be used at a downstream point for water supply. The time

of travel of the flood wave will tell the water purveyor when to expect

34
FLOOD-W1AVE AND WATER-PARTICLE TRAVELTTMES 35

an increase in flow, and the time of travel of the water particles will tell 

him when to expect the good-quality water from the reservoir.

An opportunity recently was afforded in the Raritan River baHn in 

central New Jersey to conduct a study of the relation between the 

traveltimes of a flood wave and water particles. The State of New 

Jersey had completed the construction of Spruce Run Reservoir in the 

basin in 1963. The reservoir is used to supply water in the northern part 

of the State. Some water is sold to a private water company 32 miles 

downstream from the reservoir, with delivery through the regular 

river channel. Both State and company officials were interested in 

determining the length of time for both the flood wave and the water 

particles released from the reservoir to reach the water company's 

intake.

The traveltime of the flood wave was determined by increasir^ the 

reservoir release by 135 cfs (cubic feet per second) and by observing 

changes in water stage at selected points downstream. Discharge in the 

study reach, about 34 miles in length, was about 300 cfs after the increase in flow from the reservoir.

The traveltime of the water particles was determined by injecting a 

fluorescent dye in the reservoir outfall. This was done after the increased flow for the flood-wave tracking had stabilized in the reach 

immediately below the reservoir. The dye content was then detected at 

downstream sampling points with a fluorometer. Sampling points used 

are listed in table 1.

TABLE 1. Sampling points and results of time-of-travel study in New Jersey

I 

Drainage doi 

Location area 

(sq mi') Spi 

R 

i

Hamden.___.-

Flagtown..... 

Manville 

Bound Brook.

140 

142 

260 

490 

779

Velocity, in miles per hour, of Ratio of velocity of 

ynstream Leading edge Fu'l effect 

from Leading Full Leading Peak of flood of flood 

ruce Run edge of effect of edge of concen- wave to wave to peak 

eservoir flood flood dye tration velocity of con.entra- 

(miles) wave wave of dye leading edge tior of dye 

of dye

3.9 

7.8 

21.4 

31.3 

33.7

2.6 1.1 1.9 1.0 

2.6 1.4 1.6 1.1 

2.0 1.3 .9 .8 

1.9 1.3 .8 .6 

1.9 1.2 .7 .6

1.4 

1.6

2.2 

2.4 

2.7

1.1 

1.3 

1.6

2.2 

2.0

The results of the study are summarized in table 1. The ratios for 

reaches to Hamden and Stanton shown in the last two columns are 

in the range that might be expected in open-channel flow. However, 

ratios computed for locations downstream from Stanton are larger 

than might be expected.

In the reach from Stanton to Bound Brook, there are two dams 

between each sampling point or a total of six dams. The ponded water
36 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 19'6'6-67

above these dams slows down the time of travel of the water particles 

as compared with the traveltime if the dams were net there. Thus, 

the mean velocity of the water particles traveling through the pools 

behind these dams will be much slower than those expected in the 

natural channel.

The reverse effect takes place with regard to the velocity of the flood 

wave. The velocity of a flood wave is directly proportional to the 

square root of the mean depth of the cross section. That is, the velocity 

of the flood wave will increase as the depth increases. Thus, the pools 

behind the dams tend to increase the velocity of the flood wave.

The unusually high ratios at Flagtown, Manville, and Bound Brook 

are probably due to the effects of the dams in these reaches.

The study completed in the Raritan River basin is another application of dye-tracing techniques. It offers hydrologists tr°, opportunity 

to determine the mean velocity of a stream in a natural channel, which 

can, in turn, be used as an aid in the study of wave characteristics 

in open-channel flow.

This work was done in cooperation with the New Jersey Department of Conservation and Economic Development, Division of Water 

Policy and Supply and Division of Fish and Game-.

REFERENCE CITED

Rouse, Hunter, 1950, Engineering hydraulics: New York, John Wiley & Sons, 

Inc., p. 644-647.
DYE-CLOUD PHOTOGRAPHY

By JAMES F. WILSON, Jr.

ABSTRACT

For some time after a fluorescent dye is injected into a water body, the dye 

cloud is visible and may be photographed to supplement surface sampling qualitatively and quantitatively. Both vertical and oblique aerial photographs provide synoptic views of the surface distribution of the dye, which facilitates 

monitoring the spatial distribution of the dye over 'periods of time. Color photographs are useful for exhibition purposes; black-and-white photographs taken 

with appropriate filters cost less to publish in reports and are best for quantitative analysis by such techniques as photodensitometry.

INTRODUCTION

The spectacular part of a dye study is the dye injection. The colorful rhodamine dyes stain the receiving water and immediately respond 

to dispersion and transport mechanisms. Often the dye cloud takes surprising shapes and moves in unsuspected directions. Generally the dye 

is visible, and hence photographable, for a period of several hours or 

even days, depending upon the amount of dye used and the size and 

nature of the water body. This article describes the means of obtaining 

dye-cloud photographs.

Dye concentrations are determined fluorometrically from a time 

series of water samples collected at fixed points or from spatially 

distributed samples collected by traversing the dye cloud rapidly in 

a boat. Often 35-millimeter color photographs are taken from ground 

levels (streambanks, bridges, and boats) to record the visible dye, 

primarily for use later in illustrating talks. However, for some time 

oceanographers have been using aerial photographs, both in color 

and in black and white, to supplement surface sampling in the ocean 

quantitatively, even though the period of dye visibility is relatively 

short (Reinert, 1965; Ichiye and Plutchak, 1966). Recently hydrologists have recognized the usefulness of aerial photographs cf dyes 

in lakes, streams, and estuaries. (See Fischer, 1966.)

The Phoenix, Ariz., Research Unit, Water Resources Division, U.S. 

Geological Survey, furnished the aerial photograph shown in figure

37
38 TECHNIQUES, WATE'R RESOURCES INVElSTIGATICNIS, 19'66-67

3. Robert M. Moxham, Branch of Theoretical Geophysics, Geologic 

Division, U.S. Geological Survey, furnished the isodensitracer data 

used in figure 4.

AERIAL PHOTOGRAPHS

Aerial photographs are most useful in tracing dye applications 

where monitoring the spatial distribution of the dye cloud is the 

principal objective in estuaries or reservoirs, for exanple. However, 

even in time-of-travel measurements, where the temporal distribution 

of dye concentration is monitored as the dye cloud passes fixed locations, aerial photographs can provide valuable information. Because 

the first sampling site often is many miles below the injection site, 

photographs can reveal the initial surface dispersion pattern of the 

dye cloud and the cloud's configuration as it passes through channel 

bends, tributaries, and similar features.

The advantages of aerial photographs include the following:

1. Synoptic views of the entire dye cloud or a large part of it are 

possible.

2. Details of the shape of the cloud may be seeen which are not revealed by surface sampling data.

3. Repetitive coverage at short time intervals is possible.

4. In wide water bodies such as estuaries and lakes, the exact position of the dye cloud may be located in relation to identifiable 

fixed objects or terrain features.

5. Interference by light glare may be avoided or minimized.

Both fixed-wing aircraft and helicopters have been rsed for taking 

aerial photographs. In an early manned Apollo flight a large dye 

patch in the Gulf of Mexico may be photographed from space. Cameras 

used range from hand-held 35-mm cameras to large aerial reconnaissance cameras in permanently installed camera mounts.

Low-angle oblique pictures have some value, although vertical 

photographs are generally best to work with. For example, in a 

recent study in the Potomac estuary at Washington, D.C., low-angle 

color movies of the dye immediately after injection proved useful in 

studying subsequent dispersion patterns.

The altitude at which the aircraft is flown depend? upon the size 

of the water body. Generally the aircraft should fly as low as possible, 

consistent with safety, but high enough for the photographs to include 

banks or shorelines and other terrain features needed for location 

purposes. Strip-film photography would be valuable where the dye is 

spread out a great distance along a stream. In this method of photography the film rolls past a continuously open slit in the camera at 

a speed coordinated with the speed of the aircraft. The result would 

be a continuous picture of the entire dye cloud on a single strip of film.
DYErCLOTJD PHOTOGRAPHY 39 

COLOR PHOTOGRAPHY

Color photographs are useful because the dye can easily be distinguished from similar features such as clouds of sediment. They 

are good for illustrating talks and for exhibit purposes, but generally 

are not published because of costs.

Standard color films such as Kodachrome, Aerial Ektachrome, or 

Aerial Anscochrome may be used. Generally, haze filters and colorenhancement filters should not be used. The rhodamine dyes appear 

red in reflected light. The dyes also are strongly fluorescent; absorbed 

light is re-emitted as yellow-orange light. Both reflected and fluorescent light probably contribute to the photographic image. Infrared 

color film may be useful for color enhancement, but has not yet been 

used.

BLACK-AND-WHITE PHOTOGRAPHY

Black-and-white photographs are suitable for publication in all 

kinds of reports. Figures 1 and 2 are good examples. Any panchromatic film may be used but a sharp-cut orange, red, or deep-red filter 

is recommended. The resulting image will show a white dye cloud 

against much darker water.

Filters that have been used include Wratten 15, 23A, and 25, and 

Corning 3-66 (the orange half of commonly used fluorometer filter 

590). The relation of the emission (fluorescence) spectrum of the dyes 

to the transmission spectrum of the Wratten 23A and Corning 3-66 

filters is shown in figure 3. Filters may be mounted on the camera or 

held by hand.

Supplementary color photographs are helpful in distinguishing the 

dye cloud from clouds of other materials. For example, comparison 

of figure 2 with a color photograph taken simultaneously confirmed 

that the muddy cloud in the mouth of the inlet, near the top of the 

photograph, was not dye. Later color photographs revealed dye in 

the mouth of the inlet after considerable dispersion.

Besides being suitable for publication in reports, black-and-white 

photographs are useful for photodensitometric analysis. A densitometer is a device for measuring the magnitude of light transmitted 

through an exposed and developed film negative. Ichiye and Plutchak 

(1966) have shown that excellent correlation can be obtained between 

photodensitometric traces on photographs of dye clouds and the results of surface sampling. An isodensitracer, a more complicated type 

of densitometer, actually contours the variation in intensity of light 

passing through a film negative (fig. 4). These tools should prove to 

be of value in dye studies in lakes and estuaries.
40 TECHNIQUES, WATER RESOURCES INVElSTJGATIONS, 19'66-67

FIGURE 1. Dye-cloud photographs taken from a low bridge, Grand River at Lansing, Mich., looking downstream. A, Injection of dye. B, Dye cloud about 5 

minutes after injection, same scale as A. Dark patches are very high concentrations of dye, deep purple in color, and nearly opaque. (35-mm camera, 

Kodak Plus X panchromatic film, Wratten 25 filter.)
DYEi-CLOUD PHOTOGRAPHY 41

FIGURE 2. Vertical aerial photograph of dye cloud in the Potomac estuary at 

Washington, D.C. (Altitude, 3,000 feet; aerial reconnaissance camera; Kodak 

Aerecon Safety film; Wratten 23A filter.)
42 TECHNIQUES, WATE'R RE SOURCES INVESTIGATIONS. 196fi-fi7

FUTURE POSSIBILITIES

Photographs, of course, are limited to periods of daylight and to dye 

concentrations that are visible usually above 25 parts per billion. 

The possibility of overcoming these two limitations by means of airborne electronic sensors is currently under study by the Geological 

Survey in cooperation with the National Aeronautics and Space 

Administration.

_j

*

100

km

« a, £

0 3 £

> m e>

1 1

o

>-

r

Q)

no

S X)

O K

l' '

I7T"~ *- ""||

IE 

P-R <

rr1 a:

t E 

< o

2%

50

ULTRAVIOLEt

INFRARED^ I

300 400 500 600 700 800

WAVELENGTH(A), IN MILLIMICRONS

FIGURE 3. Comparison of dye fluorescence with filter transmission for blackand-white photography. A, Generalized emission curve for the rhodamine 

family of dyes. Ordinates represent amounts of fiuoresced light expressed 

in percent of the peak; absolute values depend on dye concentration and 

intensity of exciting light. B, Generalized transmittance curve for Wratten 

23A or Corning 3-66 filters. Ordinates represent percent of incident light 

transmitted by the filter.
DYEi-CLOUD PHOTOGRAPHY 43

0

I i i i

100 200 300 FEET

FIGUBE 4. Isolines of relative film density traced directly from an isodensitracer plot for the dye-cloud image in figure 2. Film density is believed to 

be proportional to dye concentration. (See discussion by Ichiye and Plutchak, 1966, p. 366.) The 0.20 line represents the visible edge of the dye 

cloud, approximately 0 to 20 parts per billion; the 0.52 line represents 

approximately 500 parts per billion, based on fluorometric analysis of 

water samples collected when the photograph was taken.

REFERENCES

Corning Glass Works, 1962, Glass color filters: Corning, N.Y., catalog, 25 p. 

Eastman Kodak Company, 1965, Kodak Wratten filters for scientific and technical

use: Rochester, N.Y., Kodak Publication B-3, 77 p. 

Fischer, H.B., 1966, Longitudinal dispersion in laboratory and natural streams:

California Inst. Technology, W. M. Keck Lab. of Hydraulics and Water

Resources, Rept. KH-R-12, p. 151-159. 

Ichiye, T., and Plutchak, N. B., 1966, Photodensitometric measurement of dye

concentration in the ocean: Limnolgy and Oceanography, v. 11, no. 2, p.

364-370. 

Lohman, S. W., and Robinove, C. J., 1964, Photographic description and appraisal

of water resources: Photogrammetria, v. 19, no. 3, p. 83-103. 

Reinert, R. L., 1965, Near-surface oceanic diffusion from a continuing source:

Lamont Geol. Observatory Symposium on Diffusion in Oceans and Fresh

Waters, Palisades, N.Y., 1964, Proc., p. 19-27.
A MICROKIT FOR DISSOLVED OXYGEN 

DETERMINATION

By KEITH V. SLACK

ABSTRACT

Methods are described for determining dissolved oxygen in a water sample 

contained in a 10-milliliter hypodermic syringe. Precision is ibetter than 0.5 

part per million. The equipment and supplies are standard items that cost less 

than $15, exclusive of reagents. A 3- by 5-inch card file box will contain all materials needed for up to 50 dissolved oxygen determinations. Reagents for the azide 

modification of the Winkler method are either drawn into the 10-ml syringe or 

injected through the tip into the syringe barrel. The sample can be titrated in 

a small flask or in the 10-ml syringe.

INTRODUCTION

Knowledge of the dissolved oxygen (DO) content of water is important in water-quality investigations to supplement other analyses and 

to identify situations for which more comprehensive samples are 

needed. Oxygen "sags" that are below sewage outfalls on wastereceiving streams are familiar examples of the indicator value of DO 

measurements. Information about the oxygen content of lakes, reservoirs, and ground waters may be even more valuable because of 

nuisance problems resulting from manganese, iron, hydrogen sulfide, 

carbon dioxide, color, and low pH which often accompany oxygen 

deficiency. Although most field chemists recognize these facts, DO 

data frequently are not collected because the usual method requires 

excessive amounts of time and equipment.

A simple portable kit for performing the azide modification of the 

Winkler method rapidly, safely, and with minimum contamination is 

shown in figures 1 and 2. The cost, exclusive of reagents, is less than 

$15. All necessary equipment and supplies can be packed into a 3- by 

5-inch card file box. The time required for a determination is less than 

10 minutes and precision is better than 0.5 ppm (part per million), 

adequate for most purposes. The methods described in this paper are 

applicable both in the laboratory and in the field. 

44
A MICROKIT FOR DISSOLVED OXYGEN DETERMINATION 45 

SAMPLE COLLECTION

Samples for DO determination may be drawn into a 10-milliliter 

hypodermic syringe directly from the water body or from a sampling 

device. In some cases samples may be withdrawn through a large 

hypodermic needle or a cannula thrust through a rubber fitting on the 

sampler.

CLARIFICATION

Suspended sediment interferes with DO determination (American 

Public Health Association and others, 1965, p. 142). Samples may be 

clarified in a greased 25- or 50-ml syringe to prevent this interference. 

To a sample in a 50-ml syringe, add 1 ml of 6 percent alum solution 

and 0.1 to 0.2 ml of concentrated ammonium hydroxide. Gently mix 

by inversion for about 1 minute and allow the floe to settle with the 

syringe tip pointing upward. Insert a long hypodermic needle into 

the 50-ml syringe and withdraw a clear sample into a 10-ml syringe. 

A 3-inch 19-gauge spinal needle is a convenient size for this purpose.

DISSOLVED OXYGEN DETERMINATION

Either of two methods may be used to introduce reagents into the 

10-ml syringe. The first method consists of drawing reagents into the 

syringe from depressions of a glazed porcelain plate (Burke, 1962). 

Although the procedure is simple, great care is required to prevent 

the accidental inclusion of air bubbles which result when slight 

movement of the syringe plunger during mixing allows a minute 

bubble to form in the syringe tip. The depression plate method may be 

inconvenient for use in small boats and during inclement weather. 

Also, the reagents are exposed to contamination and the accuracy of 

reagent measurement is not as great as in the second method. Carpenter 

(1965) noted that errors in the volumes of the alkaline and acid 

solutions should not exceed 5 percent for proper pH control in 

Winkler determinations.

A better method of introducing reagents is to inject them from 

1-ml syringes through a rubber closure on the tip of a 10-ml syringe. 

Small serum caps make satisfactory closures, but they leak after 

repeated puncturing. A more durable closure can be made from a small 

rubber policeman. The open end of the rubber policeman is cut to the 

length of the syringe tip and the solid end is cut off leaving about 

one-eighth inch of rubber for the hypodermic needle to penetrate. The 

exact quantity of each reagent is introduced from 1-ml syringes 

equipped with small-gauge needles stuck through the rubber closure

312-670 O 6£
46 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19 616-6 7

FIGURE 1. A microkit for dissolved oxygen determination. Equipment packed 

in a 3- by 5-inch card file box.

into the barrel of the 10-ml syringe (fig. 3). As the reagents are injected, the plunger of the 10-ml syringe is automatically displaced to 

accommodate the added volume of liquid.
A MICROKIT FOR DISSOLVED OXYGEN DETERMINATION 47

FIGURE 2. Contents of a microkit for determining dissolved oxygen in a 10-ml 

hypodermic syringe J>y the depression plate method.

1-ml syringev

Rubber closure

0-ml syringe

Hypodermic needl

FIGURE 3. Method of injecting reagents from a 1-ml syringe through a 

rubber closure into the barrel of a 10-ml syringe.
48 TECHNIQUES, WATEK RESOURCES INVESTIGATIONS, 1966-67

REAGENTS AND SUPPLIES

Prepare reagents and standard solutions as directed by American 

Public Health Association and others (1965) or by Rainwater and 

Thatcher (1960).

Container

1. Manganous sulfate or chloride (reagent 1)______________ 15-ml bottle.

2. Alkali-iodide-azide (reagent 2)__________________________ Do.

3. Sulfuric acid (or phosphoric acid), concentrated (reagent 3)_ Do.

4. Sodium thiosulfate 0.0125 or 0.0118 N- ______________ 30-ml bottle.

5. Distilled or demineralized water________________________ 15-ml bottle.

6.° Indicator for iodimetry:

Thyodene powder_________________---_______-_____ 8-ml container.

Thyodene solution (0.5 gram per milliliter water) or 15-ml bottle, 

starch solution.

7. Silicone high-vacuum grease.____________________________ 8-ml container.

GENERAL EQUIPMENT

Quantity

Box, 3 by 5 by 2% inches (or other suitable container)_________________ 1

10-ml hypodermic syringe._________________________________________ 2

1-ml hypodermic syringe with 25-gauge needle._______________________ 1

25-ml Erlenmeyer flask___________________________________________ 1 1

3X pocket magnifier_______________________________________________ 1

15-ml polyethylene bottle for reagents________________________________ 2 5

30-ml polyethylene bottle_________________________________________ 1

8-ml polyethylene container for silicone grease.______________________ 1

8-ml polyethylene container for Thyodene indicator___________________ J 1

Absorbent tissue, sheets, small package_____________________________ 1

Measuring spoon, 0.1 g___________________________________________ 1 1

1 Not required if sample titrated in 10-ml syringe.

2 One additional required if sample titrated in 10-ml syringe.

CALCULATIONS

DO ppm=ml 0.0118 N sodium thiosulfate used X 10 (1) 

DO ppm=ml 0.0125 N sodium thiosulfate used X 10.635 (2) 

See Burke (1962) for method of derivation.

FIXING SAMPLES 

DEPRESSION PLATE METHOD

Equipment includes general equipment plus a 92- by 31-millimeter 

glazed porcelain depression plate. 

The procedure is as follows:

1. Place reagents 1, 2, and 3 in separate depressions of the porcelain 

plate.

2. Draw a water sample into a 10-ml syringe which has been internally 

coated with silicone grease to inhibit plunger slippage and to 

prevent air leakage. Hold the syringe tip upward and tap to 

remove bubbles. Expel the water and refill. With the syringe 

tip up, expel water to the 9.4-ml mark.
A MICROKIT FOR DISSOLVED OXYGEN DETERMINATION 49

3. Draw 0.2 ml of manganous sulfate solution (reagent 1) into the 

syringe from the depression plate. Rinse the syringe tip with distilled or demineralized water and wipe dry with tissue. Thoroughly mix the contents by repeatedly upending the springe. 

(Not©: Slight movement of the plunger during mixing may allow 

a minute air bubble to form in the syringe tip. Expel it carefully 

before proceeding.)

4. Draw 0.2 ml of alkali-iodide-azide solution (reagent 2) into the 

syringe from the depression plate. Rinse and wipe the tip. Mix 

well as described above. Allow the precipitate to settK Mix 

again. Check for air bubble in tip.

5. After precipitate has settled, draw 0.2 ml of sulfuric (or phosphoric) acid (reagent 3) from the depression plate into the 

syringe. Rinse and wipe the tip. Mix to dissolve the precipitate.

INJECTION METHOD

Equipment includes general equipment plus two rubber closures for 

10-ml syringe and three 1-ml syringes with 25-gauge needles. Four 

1-ml syringes are required if the sample is titrated in the 10-ml 

syringe. Label syringes to prevent mixing of reagents.

The procedure is as follows:

1. Fill 1-ml syringes with reagents.

2. Draw a water sample into a 10-ml syringe which has been internally 

coated with silicone grease. Hold the syringe tip upward and tap 

to remove air bubbles. Expel the water and refill. With the 

syringe tip up expel water to the 9.4-ml mark.

3. Place a rubber closure on the tip of the 10-ml syringe (Note: Pinch 

the open end of the rubber closure between thumb and forefinger 

to eliminate entrapped air as the closure is forced onto the syringe 

tip. Both the closure and the tip should be dry and free of grease.)

 i. Insert needle of 1-ml syringe (containing reagent 1) through 

rubber closure into the 10-ml syringe (fig. 3). Slowly inject 

0.2 ml manganous sulfate solution into the 10-ml syringe-. Withdraw needle from rubber closure and mix the sample by repeatedly upending the syringe.

5. Inject 0.2 ml alkali-iodide-azide solution (reagent 2) as in. step 4.. 

Withdraw needle and mix. Allow the precipitate to settle. Mix 

again.

6. After precipitate has settled, inject 0.2 ml sulfuric (or phosphoric) 

acid (reagent 3) as in step 4. Withdraw needle and mis" to dissolve the precipitate.

TITRATING SAMPLES

Samples fixed by either of the two methods may be titrated, over a 

white surface in a 25-ml Erlenmeyer flask or directly in the 10-ml
50 TECHNIQUES, WATER RESOURCE'S INVESTIGATIONS, 1966-67

syringe. The end point is easier to observe in the flask, but with practice the syringe method gives satisfactory results. Titrating in the 

syringe decreases the amount of equipment and reduces to a minimum 

the possible loss of iodine by volatilization.

ERLENMEYER FLASK METHOD

Expel the 10.0 ml of solution from the syringe into a 25-ml Erlenmeyer flask. For critical work, draw about 0.5 ml distilled water from 

a depression plate into the 10-ml syringe, invert, and withdraw 

plunger to the 10.0 mark to rinse the syringe barrel. Expel rinse 

solution into the flask. Titrate with standardized sodium thiosulfate 

solution contained in a greased 1-ml syringe with 0.01-ml graduations. 

Use a 25-guage needle on the syringe to control drop size. When the 

iodine color has nearly disappeared, add one measuring spoonful of 

Thyodene indicator powder (about 0.1 g) and continue titrating to 

the first complete disappearance of the blue color. (Note: With practice the syringe can be manipulated with one hand wMle the flask 

is swirled with the other. Use the thumb and forefinger to actuate 

the plunger of the 1-ml syringe, fingers around the plunger and 

barrel.) Estimate readings of the 1-ml syringe to the nearest 0.005 

ml with the aid of the 3 X pocket magnifier.

SYRINGE METHOD

Begin titration by injecting small increments of standardized 

sodium thiosulfate through the rubber closure into the 10-ml syringe. 

Upend the syringes to induce mixing after each addition of sodium 

thiosulfate. When the iodine color has nearly disappeared, remove the 

thiosulfate syringe and inject 0.2 ml Thyodene or starch solution into 

the 10-ml syringe. Remove the syringe containing the indicator solution and leave the hypodermic needle sticking througl^ the rubber 

closure. Carefully draw about 0.5 ml air into the 10-ml syringe and 

remove the hypodermic needle. Reattach the 1-ml syringe containing 

sodium thiosulfate and continue titration to the first complete disappearance of the blue color. (Note: The air bubble improves mixing 

in the syringe barrel and also allows the operator to see the drop size 

for the final additions of sodium thiosulfate.)

GENERAL NOTES

Either glass or plastic syringes may be used. Glass syringes are 

fragile and more expensive than plastic syringes of the disposable 

type. I prefer plastic syringes for the DO samples and for the reagents, 

but a good quality glass tuberculin syringe for titrating.
A MICROKIT FOR DISSOLVED OXYGEN DETERMINATION 51

Smudging of the graduations on disposable plastic syringes can be 

prevented by covering the syringe barrel with transparent, waterproof plastic tape. Transparent heat-shrinkable tubing intended for 

electrical insulation also may be used as a covering for plastic syringe 

barrels. Breakage of glass syringes during transit can be reduced by 

inserting them into lengths of plastic tubing or wrapping with transparent plastic tape.

Air bubbles, which tend to adhere to the rubber ends of plasticsyringe plungers, may be eliminated by placing a generous quantity 

(0.1 to 0.2 ml) of silicone grease on the end of the plunger and by 

pressing the plunger tightly into the barrel of the syringe (C. D. Ripple, oral commun., 1966). The air and excess grease are expelled 

through the tip, and it is possible to draw in a bubble-free water 

sample. Silicone stopcock grease may be substituted for the highvacuum grease in this application.

REFERENCES CITED

American Public Health Association and others, 1965, Standard methods for

the examination of water and wastewater [12th ed.] : New York, Am. Public

Health Assoc., Inc., 769 p. 

Burke, J. D., 1962, Determination of oxygen in water using a 10-ml syringe:

Jour. Elisha Mitchell Sci. Soc., v. 78, no. 2, p. 145-147. 

Carpenter, J. H., 1965, The Chesapeake Bay Institute technique for the Winkler

dissolved oxygen method: Limnology and Oceanography, v. 10, no. 1, p.

141-143. 

Rainwater, F. H., and Thatcher, L. L., 1960, Methods for collection and analysis

of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p.
FIELD KIT FOR DETERMINING ALKALINITY

By J. L. KUKKLER

ABSTRACT

Accurate field determinations of alkalinity are possible with the described 

field kit because the temperatures of the standard buffer so'utions and the 

samples are maintained within 2° O of the temperature of the sampling source. 

Meld determinations of standard solutions indicate that results deviate less 

than 1 percent from the correct values.

Accurate field determinations of alkalinity are necessary for the 

study of many types of water problems. For example, the alkalinity of 

water that is precipitating travertine, a mineral composed of calcium 

carbonate, may change rapidly after sample collection. Samples from 

the Sandia Mountains in New Mexico of spring water precipitating 

travertine have shown changes of more than 0.1 pH unit 30 seconds 

after collection. Such chemical instability requires that alkalinity be 

determined in the field at the time of sample collection if the determination is to be useful for geochemical studies.

Alkalinity is usually caused by the presence of bicarbonates, carbonates, and hydroxides in waters.

Consideration must be given to maintaining the standard buffer 

solutions, the sample, and the electrodes at the temperature of the 

sampling source if accurate field determinations of alkalinity are to 

be made. This article describes a simple portable field Ht that maintains the temperatures of these items within 2° C of the temperature 

of the sampling source.

Selected components of the field kit are shown in figure 1. A reservoir and a water bath are constructed from a 5-gallon GI water can 

and an 8-inch-diameter sieve pan approximately 2 inches deep. A connector for rubber tubing is soldered to the water can about 1 inch above 

the base. Flow into the water bath from the water car through the 

rubber tubing is regulated by a valve soldered about one-half inch 

above the bottom of the water bath. Another connector is soldered 

to the water bath about one-half inch below the top of the bath and, 

when tubing is attached, serves as a drain. 

52
FIELD KIT FOR DETERMINING ALKALINITY 53

Cocktail 

stirrer

FIGUBE 1. Selected components of field kit for determining alkalinity.
54 TECHNIQUES, WATER RESOURCE® INVESTIGATIONS, 19 616-6 7

The bath is covered with a lid containing four holes. Three of these 

holes can accommodate 50-ml (milliliter) beakers and the fourth, a 

150-ml beaker. A bolt soldered to the lid serves as a handle to move 

the lid and position the beakers. Both the reservoir water can and 

the water bath are painted with several coats of white paint and epoxy 

resin to minimize heat transfer.

In field operations the water can is filled with water from the 

sampling source and the valve on the water bath is adjusted for a flow 

of about one-half pint per minute. The 50-ml beakers are filled with 

the appropriate standard buffer solutions and placed in the bath 

water. After water has flowed through the water bath for about 

30 minutes and the buffer solutions have been stirred occasionally, 

thermal equilibrium between the bath water and buffer solutions is 

usually attained. A portable battery-operated pH meter (not shown 

in fig. 1) is calibrated with the buffer solutions at the equilibrium 

temperature. Then a sample of water is collected and titrated in a 

150-ml beaker placed in the water bath. The technique of the alkalinity determination is described by Rainwater and Thatcher (1960, 

p. 94). No attempt is made to bring the titrant to the temperature 

of the water bath and no attempt is necessary if sufficient time is allowed near the end point for the sample to come to thermal equilibrium 

with the water bath. A small battery-operated cocktail s+irrer is used 

to stir the sample during the titration.

A combination glass and reference electrode is used to measure pH 

values. The electrode is attached by an electrode clamp to a thick strip 

of lead, which is attached to a swivel on a ringstand. Tve lead strip 

bends easily and facilitates washing and positioning the electrode.

This apparatus has been field tested on solutions of known alkalinity 

and results were consistently within 1 percent of the correct values.

REFERENCE CITED

Rainwater, F. H., and Thatcher, L. L., 1960, Methods for collection and analysis 

'of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p.
RAPID FIELD FILTRATION OF WATER SAMPLES

By CHARLES F. BEHKSTRESSER, Jr.

ABSTRACT

Water samples should be filtered in the field at the time of collection to 

reduce chemical change when samples are 'Stored. A successful method is to use 

a pressure-filtration apparatus.

INTRODUCTION

The goal of collecting water samples is to determine the chemical 

quality of water at the time of collection. Environmental impurities 

that may alter the chemical nature of water during storage include 

bacteria and colloids, clay, silt, and sand, as well as algae, insect 

larvae, tadpoles, leaves, and twigs. Any of these may affect the chemistry of the sample by biologic appropriation or release, adsorption, 

or other physical and chemical reactions.

Filtration is essential in preserving the chemical quality of samples 

from biotically active environments or when extraneous matter is 

present. The following analytical data demonstrate changes presumably caused by an algal bloom in a sample after collection.

Sample pressure Sample unflltered,

filtered at time analyzed after

of collection algal bloom

Date:

Collected-----.-.---.-.---- --.____-_-__--_.__--____.___.._. January20,1966 January20,1966

Analyzed..-..-..----....--..................--....--....--. January 29,1966 February 21,1966

Bicarbonate _

Carbonate. _

Sulfate_ _ ,_ .- _.

Specific conductance. _

PH__. _______________

_____________ ____ppm_.

.--.__-.___-_---. ppm_.

.___. _-_.--. __ppm__

_ micjromhos at 25° C _

662

0

2

1,670

8.2

420

22

157

1,690

8.6

Except for filtration and length of storage time, these samples were 

collected and stored under identical conditions. The filtered sample 

exhibited no visible evidence of algal bloom after storage for an 

additional 7 months. Experience with other samples also indicates 

that filtration stabilizes alkalinity.

55
56 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196'6-67 

VACUUM FILTRATION

Vacuum filtration is described by Wilder (1966) andH'armon (1966) 

who attempted to solve the problem of sample preservation. Unfortunately, vacuum filtration alters partial pressures of dissolved gaseous 

constituents and consequently tends selectively to remove dissolved 

gases from the sample; for example, carbon dioxide. The following 

tables shows data for both pressure- and vacuum-filtered samples 

compared with data for the raw sample. These analyses were made 

within 48 hours of collection, and presumably before appreciable biotic 

change had occurred. Analyses of the raw and pressure-filtered samples 

agree within the experimental limits of the method; the analysis of 

the vacuum-filtered sample exhibits a significant departure in each 

constituent and in total alkalinity. Reproducibility better than 2 

percent cannot be expected in this determination for the common 

alkalinity components (bicarbonate and carbonate), but the total 

alkalinity value is somewhat more stable than the component values 

(Eainwater and Thatcher, 1960, p. 94). Each of the values above was 

verified by a second filtration.

Sample condition

Bicarbonate. ___ _ _ _ __ppm_

Carbonate ____ ______ _ _ _.ppm _

Total alkalinity (as HCO3)-_--_---__-__--____-ppm_-

Raw

418 

22 

464

Pressure 

f'tered 

(100 psi)

420 

24 

468

Vacuum 

filtered 

(2.1 mm 

Hg)

410 

14 

438

PRESSURE FILTRATION

Pressure filtration, preferably with nitrogen, is an alternative to 

vacuum methods. Both carbon dioxide and oxygen are readily available but can react with the water sample. Compressed air contains 

both carbon dioxide and oxygen and is likewise unsuitable. Helium 

is chemically suitable but is expensive and may be difficult to obtain. 

Nitrogen is cheap, readily available, and only slightly soluble in 

water. No chemical reactions are known to occur in water when nitrogen is introduced under pressure.

In the apparatus and procedure described in the following sections, 

nitrogen gas was used to produce filtration pressure.
RAPID FIELD FILTRATION OF WATER SAMPLES

APPARATUS AND MATERIALS

57

The apparatus (fig. 1, 2) and materials are listed as follows: 

Nitrogen gas, compressed (Airco nitrogen OP or equivalent). 

Gas-pressure regulator, calibrated to 20 psi (pounds per square

inch) or finer.

Stainless-steel pressure vessel, Millipore XX67 000 or equivalent. 

Stainless-steel high-pressure filter holder, Millipore XX45 04700

or equivalent.

High-pressure tubing (250+ psi). 

Stainless-steel fittings.

Fiberglass prefilter, Millipore AP20 or equivalent. 

Plastic-membrane filter, Millipore AP20 or equivalent. 

Sample bottle.

FIGTJKE 1. 'Field filtration equipment. From left to right, the nitrogen cylinder 

and gas-pressure regulator, pressure vessel, high-pressure filter holder, and 

sample bottle.
58 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196>6-67

FIGURE 2. Details of pressure filter holder. Right half shows filter support and 

discharge line. White discs are the fiberglass prefilter and plastic-membrane 

filter. Screws fasten two parts as seen in figure 1.

OPERATION

Water samples generally are collected in the pressure tank. Rinse 

the container at least twice with sample water before collecting the 

sample. If the water is particularly turbid or contains gross solid 

material, such as leaves, spores, or larvae, a sample may be collected 

temporarily in a clean container, sealed tightly, and stored in darkness until the material has a chance to settle. A siphon with an upturned intake that rises above the sediment layer at the bottom of 

the sample bottle can be used to separate the sample from the solids. 

Darkness during storage is necessary to minimize phototropic activity.

The nitrogen cylinder is connected to the pressure tank with tubing 

via a gas-pressure regulator. This regulator should be calibrated 

to at least 20 psi. A minimum pressure (breakthrough pressure) of 

50 psi is required to initiate flow through the filter system. Normal 

operating pressure, which depends upon the relief valve on the pressure tank, is about 100 psi.

The filter system consists of a prefilter and a filter in the holder 

(fig. 2). The prefilter is a fiberglass pad that removes coarse material
RAPID FIELD FILTRATION OF WATER SAMPLES 59

and reduces buildup of unsorted-size material. The filter used by the 

author is a plastic membrane that removes material coarser than 0.45 

micron. A 0.45-micron pore size seems to provide a satisfactory compromise between removal of particulate matter for most analytical 

purposes and a satisfactory flow rate. For special purposes, such as 

the removal of all colloids, smaller pore sizes have been suggested 

(V. C. Kennedy, oral commun., 1966); however the flow rate is substantially reduced. A typical filtration rate for water samples through 

0.45-micron filters is about 0.2 gallon per minute. Use of the fiberglass 

prefilter generally extends filter life at least fourfold.

SAFETY CONSIDERATIONS

Commercial nitrogen tanks are heavy and unwieldy. Therefore, 

they should be anchored securely in the vehicle and in such a position 

that injury to the driver does not occur.

SUMMARY

Solids may cause changes in water quality of samples durirg storage; it is therefore desirable to remove particles in the field. Filtration 

is the best method of doing this; both vacuum filtration and £ assure 

filtration are feasible. However, vacuum filtration and pressure filtration with chemically active gases may cause chemical changes in the 

sample. The author chose nitrogen gas for pressure filtration because 

of low cost, availability, and low chemical activity. This sairple apparatus has furnished excellent results.

REFERENCES CITED

Harmon, N. B., 1966, Filtering water samples using vacuum from automobile 

intake manifold, in Mesnier, G. N., and Chase, E. B., compilers, Selected 

techniques in water resources investigations, 1965: U.S. Geol. Survev WaterSupply Paper 1822, p. 61-62.

Rainwater, F. H., and Thatcher, L. L., 1960, Methods for collection and analysis 

of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p.

Wilder, H. B., 1966, Filtering water samples using vacuum from automobile 

windshield wiper, in Mesnier, G. N., and Chase, E. B., compilers, Selected 

techniques in water resources investigations, 1965: U.S. Geol. Survey WaterSupply Paper 1822, p. 59-60.
FIELD MONITORING OF THE QUALITY OF WATER 

DURING THE DRILLING OF WELI^S

By JACK BAWSON

ABSTRACT

During the drilling of wells, aquifers at different depths that yield water of 

different chemical composition may be penetrated. Although f uid-conductivity 

logging of the wells provides an indication of the total dissolved-solids content 

of the water in the several aquifers, conductivity alone does not indicate the 

types and concentrations of individual ions in the water. In conjunction with 

conductivity measurements, simple, rapid, and accurate visual methods of 

analysis for chloride, sulfate, and hardness can be conducted in the field to provide more detailed and reliable information on the chemical composition of the 

water as it is reached.

INTRODUCTION

Multiple-aquifer wells may penetrate formations that yield water of 

different chemical composition. Dissolved constituents in the water 

from some of these aquifers may limit or preclude the uee of the water 

as a domestic supply. Field monitoring of the quality of water during 

the drilling of wells permits immediate decisions by management and 

thus eliminates the necessity and cost of maintaining a drilling crew 

on standby while waiting for a chemical analysis from a laboratory 

possibly several hundred miles away.

If sufficient data on the chemical composition of the water are obtained as the water is reached during drilling, those formations that 

yield water of poor quality can be identified and sealed off to prevent 

contamination of water from the other formations. Regardless of 

whether a well penetrates one or several aquifers, field analyses will 

aid in determining if the well should be developed as a domestic supply 

or abandoned.

The suitability of a water for domestic use depends partly upon 

the types and concentrations of various ions in the water. Constituents or properties in excessive amounts that often preclude the use 

of a water as a domestic supply include dissolved solids, chloride, 

sulfate, and hardness. According to the U.S. Public Health Service 

(1962), the suggested limits for dissolved solids, sulfate, and chloride 

60
FIELD MONITORING, WATER QUALITY DURING WELL DRILLING 61

in drinking water are 500 ppm (parts per million), 250 ppm, and 250 

ppm, respectively. Fluid-conductivity logging of a well provides some 

indication of the total dissolved-solids content of water in an aquifer. 

However, conductivity alone does not identify the types and concentrations of individual ions in the water. More detailed and reliable 

information on the chemical composition of the water can be obtained 

by simple, rapid, and accurate methods of analysis.

METHODS OF FIELD ANALYSIS

Selected visual laboratory methods for the determination of chloride, sulfate, and hardness are suitable for field use. Chloride can be 

determined by the Mohr method of using silver nitrate as the titrant 

and potassium chromate as the indicator (Rainwater and Thatcher, 

1960, p. 141-143). Detection of the end point in this method is facilitated by illuminating the titration with yellow light. Sulfate 

can be determined visually by using barium chloride as the titrant 

and a dioxane-thorin solution as an indicator (Eainwater and 

Thatcher, 1960, p. 279-281). Because many metal ions interfere with 

this method, all metals are removed before titration by passing the 

sample through an ion-exchange column charged with Amberlite IR120 and operating on the hydrogen cycle. Hardness can be titrated 

visually with disodium dihydrogen ethylenediamine tetraacetate (Na2 

EDTA) by using Eriochrome Black T as the indicator (Rainwater 

and Thatcher, 1960, p. 174-176).

The total dissolved-solids content of water can be estimated by electrical conductivity measurements. Although no exact relation exists 

between dissolved solids and specific conductance, the following general relation is applicable unless the water has an unusual composition:

Dissolved solids (ppm) = specific conductance (micromhos)

X0.65±0.1.

Equipment for the determinations includes filter holders, filter 

flasks, filter paper, pipets, burets, beakers of assorted sizes, chloride 

dishes, stirring rods, a battery-powered lamp with a yellow bulb 

(or yellow goggles), an ion-exchange column, and a portable conductivity meter.

Because the equipment takes little space and requires no electrical 

power, it can be assembled and water samples can be analyzed r,t the 

drilling site. Where no more convenient space is available, the rear 

compartment of a station wagon is adequate.

312-670 O 68 5
62 TECHNIQUES, WATER RESOURCE® INVESTIGATIONS, 19'6'6-67

COLLECTION OF BEPBESENTATIVE SAMPLES WITH BEFEBENCES 

TO VABIOUS METHODS OF DBILLING

Regardless of whether the water sample is analyzed in the field 

or laboratory, the chemical analysis is only as useful as the sample 

is representative. Although a representative sample may be collected 

during either the cable-tool or rotary methods of drilling, the cabletool method is especially advantageous for detecting water-bearing 

formations and for the frequent collection of water samples. Generally 

the small amount of drilling fluid used in cable-tool drilling does 

not seal off a water-bearing formation. The aquifer can be detected 

readily; contaminants can be flushed from the formation with a minimum of bailing or pumping; and a representative water sample from 

the formation can be obtained by pumping or with ?, point sampler.

In the rotary method of drilling, the bore hole is kept full of heavy 

mud that is circulated to cool the bit, return the cuttings to the surface, 

and prevent caving. Due to its specific gravity, this fluid may exert 

a greater pressure against the walls of the hole than water flowing 

in from a formation. The mud tends to penetrate and seal the pore 

spaces of a formation and prevent water in a formation under low 

hydrostatic pressure from entering the hole. As a res lit, some waterbearing formations may be misinterpreted as dry. Drilling fluid 

continuously lost by seepage through the walls of th°, hole may contaminate water in formations. Therefore, identification of all waterbearing formations penetrated by a rotary-drilled well and collection 

of representative water samples may require the us^ of packers to 

isolate the individual formations and may require long periods of 

pumping or surging to flush drilling contaminants from the 

formations.

PBACTICAL APPLICATION OF FIELD MONITOBING OF THE 

QUALITY OF WATEB DUBING TEST DBILLING

In July 1963 the National Park Service began test drilling to locate 

a source of water for a proposed campground and ranger station in 

the Castolon area, Big Bend National Park, Tex. (fig. 1). The results 

of previous work in the area indicated that any fresh-water-bearing 

beds found in the area might be immediately underlain by beds containing water unsuitable for domestic use. The author went to Castolon to monitor the quality of water during the drilling.

Three test wells were drilled in the Castolon area. Wells T-1 and 

T-2 were drilled in the dry channel of Blue Creek. Blue Creek heads 

in the Chisos Mountains and a large part of its course is deeply incised 

in rocks of Tertiary or Cretaceous age. The rocks of Tertiary age consist of bedded tuff, welded tuff, tuffaceous sandstone, conglomerate,
FIELD MONITORING, WATER QUALITY DURING WELL DRILLING 63

and lava; the rocks of Cretaceous age consist of gypsiferous marl, 

clay, silt, sandstone, and coal (Leggat, 1963, p. 7). At the drilling sites, 

Blue Creek occupies an alluvial-filled channel cut in very fine, easily 

eroded silt.

Test well T-3 was drilled in the dry channel of Alamo Creek (fig. 

1). Sedimentary rocks o'f Late Cretaceous age and volcanic rocks of

29°15'

103°30'

FIGURE 1. Map of Castolon area, Big Bend National Park, Brewster County, 

Tex., showing locations of test sites.
64 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19 616-6 7

Tertiary age are exposed in a large part of the drainage area of Alamo 

Creek (Leggat, 1963, p. 13). At the drilling site, the wide channel of 

Alamo Creek is filled with alluvium.

The three test holes were drilled by the cable-tool method. As each 

well was drilled, formation samples were collected at 5-foot intervals; 

and when water was reached, the yield was estimated by bailing. A 

water sample for chemical analysis was collected with a Foerst sampler. Drillers' logs for the test holes are given in table 1 and the 

results of chemical analyses are given in table 2.

TABLE 1. Logs of test wells in the Castolon area, Big Bend National Park, Brewste

County, Tex.

[Driller: C. Langlitz]

Thick- Depth 

ness 

(feet)

Thick- Depth 

ness (feet) 

(feet)

Castolon test well 1

sat - _-.- 

SancL____-_______ . _ _

Sand, with clay. ___-_

Clay, yellow, with some

crav

Clay, blue____--____--_-

Clay, brownish-grayClay, brownish-gray,

gravel __ ______ ____

Clay, gray, slight brown

tint __ ______________

Clay, reddish-brown. ___

Clay, grayish-brown

3

25

9

3

5

5

10

10

5

5

5

35

15

3

28

37

40

45

50

60

70

75

80

85

120

135

Clay, gray, slight brcwn

tint..-.-- --__-__ ___

Clay, gray, with trace

of gray shale _ ____ __

Shale, gray ____________

Clay, gray, shaly _.----__

Clay, gray _________

Clay, gray, sandy

Clay, greenish-gray,

Sand, greenish-gray,

Sand, greenish-gray,

with some clay. _ . _

Sandstone, greenishgray------ _-_- --_-_

Sand, greenish-gray

argillaceous..--.--- __

5

5

15

10

5

5

10

5

5

10

5

140

145

160

170

175

180

190

195

200

210

215

Castolon test well 2

Sand

Sand

and

and

gravel,

gravel.

silty 

20

5

15

20

?S

40

Clay,

Clay,

Clay,

brown ________ .

grayish-brown. __

5

5

10

45

50

60

Castolon test well 3

Sand and gravel __ __

10

_ 36

4

10

4fi

50

Clay, yellowish-gray-- __

Clay, reddish-brown. __

5

10

4

55

65

69
FIELD MONITORING, WATER QUALITY DURING WELL DRILLING 65

TABLE 2. Field analyses of water from test wells in the Castolon area, Big Bend 

National Park, Brewster County, Tex., in 1968

[Kesults in parts per million except as indicated]

Spec'fic conWell Depth Date of collec- Sulfate Chloride Hardness as ductance 

(feet) tion (S0<) (Cl) CaCOs (mic-omhos

at 25° C) i

U.S. Public Health Service drink250 250

T-l

22

2

2

3

3

3

200

25

47

60

46

68

68

July 11

July 13

July 14

July 16

July 17

July 19 3

July 19 4

<5

228

68

54

338

364

316

778

33

10

7.0

14

13

13

26

60

16

36

124

96

128

2,300

900

450

410

1,020

1, 100

1,090

1 Field conductivity instrument was later found to have been operating improperly. Kesults si own are 

believed to be about 200 micromhos too low.

2 Sample possibly contaminated by river water used in drilling, 

s Time of collection, 7:00 a.m. 

* Time of collection, 6:30 p.m.

A water-bearing sand was penetrated in well T-l (table 1) at a 

depth of about 200 feet. However, field analyses showed that the 

dissolved-solids (as indicated by specific conductance) and sulfate 

content of the water exceeded the limits recommended by the U.S. 

Public Health Service. The well was then deepened to 215 feet, where 

a trace of oil was discovered. Therefore, the hole was plugged, capped, 

and abandoned.

A water-bearing sand was penetrated by well T-2 at a depth of about 

18 feet (table 1). At a depth of 25 feet, the hole was cleaned out and 

the yield was estimated by bailing; but before a representative sample 

could be obtained, the hole caved. The hole was again drilled to 25 

feet and was bailed for only a brief period before the collection of a 

water sample. As a result, the sample undoubtedly was contaminated 

with drilling fluid, but because the estimated yield was only about 1 

gpm (gallons per minute) and because the hole could not be kept 

open, casing was installed and drilling was continued to a depth of 47 

feet, where a more representative sample was obtained. A chemical 

analysis of water from this depth (table 2) indicated that the water 

was suitable for domestic use, but the yield was estimated to be only 

about 3 gpm. Therefore the hole was deepened to 60 feet and a chemical analysis of the water from this depth (table 2) indicated that the 

water was suitable for domestic use. Consequently, the well was completed with 6-inch casing, torch slotted from 15 to 45 feet, and was 

developed as a possible domestic supply.

Well T-3, in the channel of Alamo Creek, penetrated a water-
66 TECHNIQUES, WATER RESOURCE'S INVESTIGATIONS, 1966-67

bearing sand and gravel at a depth of about 32 feet (table 1). The 

hole was deepened to 46 feet where a sample of water was collected 

for chemical analysis. The analysis (table 2) indicated that the dis.- 

solved-solids and sulfate content of the water exceeded the limits 

recommended by the U.S. Public Health Service. Subsequently the 

hole was deepened to 69 feet. Between depths of 50 and 69 feet a 

nonwater-bearing clay was penetrated and drilling ws.s discontinued. 

The hole was bailed, the yield was estimated, and another sample 

for chemical analysis was collected. The analysis (table 2) confirmed 

that the dissolved-solids and sulfate content of the water exceeded 

the limits recommended by the U.S. Public Health Service. Nevertheless, the analysis indicated that the water could be used as a supplementary supply in the event that well T-2 could rot yield a sufficient quantity of water. The well was completed and developed as 

a possible supplementary domestic supply.

Field monitoring of the quality of water found during the drilling 

of test wells in the Castolon area, in conjunction with, the collection 

and evaluation of formation samples, indicated that a single, but 

different, aquifer was penetrated by each well. More importantly, 

the field analyses provided almost immediate information on the suitability of the water for domestic use. These data permitted immediate 

decisions by management and eliminated the necessity of maintaining 

a drilling crew on standby while waiting for results of chemical analyses from a distant laboratory.

REFERENCES CITED

Leggat, E. R., 1963, Water supply for the Castolon area, Big Berd National Park, 

Brewster County, Texas: U.S. Geol. Survey open-file rept., 19 p.

Rainwater, F. H., and Thatclier, L. L., 1960, Methods for collection and analysis 

of water samples: U.S. Geol. Survey Water-Supply Paper 1454, 301 p.

U.S. Public Health Service, 1962, Drinking water standards, 3962: U.S. Public 

Health Service Pub. 956, 61 p.
SAMPLING APPARATUS TO MINIMIZE AERATION OF 

WATER COLLECTED AT SHALLOW DEPTHS FOR THE 

DETERMINATION OF DISSOLVED GASES

By B. F. JOYNEK

ABSTRACT

A sampling apparatus for collecting nonaerated water from shallow depths 

for the determination of dissolved gases can be assembled from materials available in any chemical laboratory. The device can be used in water only 1 inch 

deep; conventional samplers for the same purpose cannot be used in water less 

than 18 inches deep.

Frequently it is desirable to coileci water samples for the determination of dissolved gases such as hydrogen sulfide or oxygen. Samples should be collected with a minimum of aeration to prevent loss 

of the gases. Conventional sampling apparatus consists of a cylindrical brass container 4 inches in diameter and 16 inches high that 

has an internal built-in platform, a screw cover with an inlet orifice to 

which a tube is connected, and a special 300-milliliter sample bottle 

that rests on the platform. When the sampler is assembled, the tube 

from the inlet extends to the bottom of the sample bottle. A sample 

is collected by lowering the apparatus, upright, into a water body and 

by allowing enough time for the water flowing into the sample bottle 

to be displaced three times. Excess water overflows into the brass 

container. This apparatus is efficient, but it is expensive ($75 for the 

brass container and $1.95 for each sample bottle). Also, because it 

must remain upright during sampling, it cannot be used in water less 

than about 18 inches deep.

Figure 1 shows a simple piece of apparatus that is effective in the 

collection of samples for the determination of dissolved gasee. The 

sampler can be assembled in a few minutes from materials that should 

be available in any laboratory a polyethylene bottle, glass and rubber tubing, a two-hole stopper, and an aspirator.

The illustrated sampler has been used since 1960 to collect samples 

for hydrogen sulfide determinations from shallow water in Everglades National Park in southern Florida. Most of Everglades National Park is covered with shallow water, except during droughts. 

Often the water is so shallow that the use of conventional apparatus 

for sampling is not practical.

67
68 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'6i6-67

Rubber or plastic tubing

Two-hole rubber stopper ^ I I

Glass tubing inserted to 

about V« inch from 

bottom of bottle

1-quart polyethylene 

bottle

Aspirator

FIGURE 1. Assembled sampler for collecting nonaerated water at shallow depths.

With this new apparatus, the bottle is lowered to collect a sample 

at the desired depth, and the aspirator, which is held above the water 

surface, is operated. As air is evacuated from the bottle by the aspirator, water flows in. After the bottle is filled, the water should be displaced at least three times by continuing to operate the aspirator. To 

sample very shallow water, the bottle can be placed on its side. Another 

method, by which samples can be collected from water only 1 inch 

deep, is to attach a piece of rubber or plastic tubing to the inlet glass 

tube and to place the free end of the attached tubing in the shallow 

water.

The new sampler has been used also to collect lake; samples from 

depths as great as 25 feet. Theoretically, samples could be collected 

at any depth by attaching a sufficiently long piece of flexible tubing 

to the inlet of the bottle. However, the difficulty of displacing water in 

the bottle increases with sampling depth. This problem could be solved 

by using a more effective vacuum system.
USE OF CARBON DIOXIDE IN BUBBLE GAGES TO PREVENT PRECIPITATION OF CALCIUM CARBONATE

By WALLACE D. BOBBINS and LEON S. HUGHES

ABSTRACT

The tube mouth of the gas-purge system of a bubble gage may become blocked 

over a period of time by precipitation of calcium carbonate when nitrogen gas 

is bubbled through the tube into water containing high concentrations of calcium 

and bicarbonate in solution. Carbon dioxide substituted for nitrogen has proved 

 successful in preventing the precipitation of calcium carbonate at the bubblegage orifice. The conversion from nitrogen to carbon dioxide is inexpensive, 

and thereafter, operation and maintenance costs of the bubble gage are reduced 

substantially.

The tube mouth of the gas-purge system of a bubble gage may become blocked over a period of time by precipitation of calcium carbonate when nitrogen gas is bubbled through the tube into water containing high concentrations of calcium and bicarbonate in solution.

A bubble gage measures the elevation of a water surface by sensing 

pressure above an orifice submerged in the body of water of which 

the elevation is being determined. The pressure head of water at the 

orifice is transmitted by a gas-purge system, through flexible polyethylene tubing, to a servomanometer that operates a continuous waterstage recorder. Nitrogen gas from a storage cylinder in the recorder 

shelter feeds into the pressure system and bubbles slowly from the 

sensing orifice. The pressure at the orifice, and hence in any part 

of the system, is related to the head or depth of water over the orifice. 

The bubble gage is described in more detail by Barren (1963, p. Z4).

When the polyethylene tube becomes partly blocked by a precipitate 

of calcium carbonate, more pressure is required to force gas bubbles 

from the orifice. This increase in line pressure is reflected back to the 

servomanometer and causes the recorder to indicate a higher water 

stage than actually exists.

The base flow of streams that drain limestone terranes is likely to be 

saturated with calcium and bicarbonate. Analyses of typical waters 

from such areas have shown 75 ppm (parts per million) of calcium and 

250 ppm of bicarbonate.

69
70 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

The presence of high concentrations of calcium and bicarbonate in 

solution is possible only when a large amount of carbon dioxide is 

available. Hem (1959, p. 71-78) discusses the relation of carbon dioxide in solution to the solubility of calcium carbonate. Water containing carbon dioxide dissolves calcium carbonate until an equilibrium 

is established with calcium and bicarbonate ions in solution :

If carbon dioxide is being added to the system represented by the above 

equation, solution continues ; if it is removed from the system, deposition occurs.

Surface water, being in contact with the air, is usually stable with 

respect to carbon dioxide and calcium carbonate. However, when nitrogen gas is bubbled through the water, some of the nitrogen is dissolved and part of the carbon dioxide is displaced from solution, 

which changes the equilibrium condition and causes the precipitation 

of calcium carbonate. At the orifice of the bubble-gage tube, where 

the water of the stream is continuously in contact with the nitrogen 

gas, maximum displacement of carbon dioxide and maximum precipitation of calcium carbonate occur. Figure 1 compares a clean orifice 

with one partly closed by precipitation of calcium carbonate.

FIGURE 1. Orifice of bubble-gage tubing before and after deposition of calcium 

carbonate. Outside diameter of tubing is three-eighths inch; inside diameter, 

one-eighth inch. Photograph enlarged (about X 4).
USE OF CARBON DIOXIDE IN BUBBLE GiAGElS 71

The substitution of carbon dioxide for nitrogen in the gas-purge system prevents the precipitation of calcium carbonate at the bubblegage orifice. As the carbon dioxide contacts the water at the tube mouth, 

part of the gas is dissolved; thus the capacity of the water to dissolve 

calcium carbonate and to hold calcium and bicarbonate ions in solution is increased. Therefore, a precipitate never forms.

Only minor inconveniences have been experienced in converting to 

the use of carbon dioxide. The regulators furnished with bubble gages 

do not fit the valves on carbon dioxide cylinders, but a valve with proper 

threads is available from gas suppliers for about $5, or a threaded 

adapter, costing about $2.50, can be used to connect the nitrogen regulator to the carbon dioxide valve. The pressure gage does not show how 

much carbon dioxide remains in the cylinder, because the pressure remains the same (except for variations due to temperature) until the 

cylinder is almost empty. It is necessary, therefore, to weigh the cylinder to check its contents. This is easily done with inexpensive bathroom scales.

REFERENCES CITED

Barron, E. G., 1963, New instruments for surface-water investigations, in Mesnier, 

G. N., and Iseri, K. T., compilers, Selected techniques in water resources investigations : U.S. Geol. Survey Water-Supply Paper 1669-Z, p. Z1-Z12.

Hem, J. D., 1959, Study and interpretation of chemical characteristics of natural 

water: U.S. Geol. Survey Water-Supply Paper 1473,269 p.
POLYETHYLENE OIL TUBES FOR STILLING WELLS

By BOBEBT L. STEWAET

ABSTRACT

A polyethylene oil tube used in the stilling well of a lake- or stream-gaging station is an efficient and economical device to prevent ice from affecting the continuous water-stage (gage-height) record. The tube can be installed and removed 

without disturbing the gaging station structure and its instruments.

Many lake- and stream-gaging stations use a stilling well to obtain a 

continuous record of water stage (gage height). If the stilling well is 

exposed to and unprotected from subfreezing air temperatures, ice 

often forms in the well and affects the recording of water stage. Various 

devices are used to prevent the formation of ice in a well; the most common one is a tube or cylinder of oil. A head of kerosene, or No. 1 fuel 

oil, in a tube within the well lowers the elevation of the water surface 

and protects it from freezing air temperatures.

A polyethylene oil tube has an advantage over a metal or rigid oil 

tube because it is flexible and can therefore be installed in the well, 

and removed, with a minimum of effort and without disturbing the 

gaging-station structure or its instruments. The low cost and simple 

construction features of a polyethylene oil tube justify seasonal or 

yearly replacement, if necessary, although experience indicates the 

tubing will last a number of years in continuous operation.

The tube is made by fitting a formed %-inch-thick steel hoop, the 

same diameter as the tubing, at each end of a desired length of tubing; 

3 inches of tubing should be allowed at each end to be turned back, and 

outside, over the hoop (fig. 1). Metal clamps (hog rings) fitted around 

the hoop and through the tubing will hold the hoop in place. The completed oil tube should be re-rolled until it is ready to be lowered into the 

well. Care should be taken not to fold it, particularly at the lower end, 

as a sharp crease might fracture the material and the oil will leak out.

The oil tube can be suspended from the floor of the gage house, 

or from the recorder shelf, by several methods. The simplest method is 

to suspend the tube from the recorder shelf using three long-threaded 

eyebolts and three S-hooks (fig. 2A). Another method is to use a 

shelf bracket, attached to the side of the well, below the floor (fig. 

72
POLYEfTHYLE'NE, OIL TUBES FOR STILLING WELLS 73

FIGURE 1. Formed steel ring fitted into one end of roll of polyethylene tubing.

The oil tub© should be positioned so that the bottom end of the tube is 

well below the lowest stage, or water level, expected. This will prevent 

loss of oil from the tube at extreme low stages. Ten gallons of oil 

(kerosene) in a 14-inch-diameter tube will be about 1.25 feet thick. 

About 5 pounds of extra weight attached to the bottom end of the tube 

will overcome the buoyant effect of the 10 gallons of oil and help keep 

the tube plumb. A polyethylene oil tube longer than 30 feet may require 

a weighted guy wire hung from each eyebolt through the inside of the 

tube to keep it open and plumb.
74 TECHNIQUES, WATE'R RESOURCES INVEiSITIGATIONS, 19 616-6 7

FIGURE 2. Polyethylene oil tube. A, Suspended from recorder shelf. B, Suspended under floor of shelter.
WATER-MANOMETER-AIR-LINE ASSEMBLY FOR 

DETERMINING DEPTH TO WATER IN WELLS

By O. J. LOELTZ

ABSTRACT

A combination water-manometer-air-line assembly provides an accurate and 

reliable means for obtaining water-level measurements in wells. The assembly is 

especially adapted to the rapid measurement of changing water levels during and 

immediately after pumping tests. It successfully overcomes many of the deficiencies of conventional methods.

INTRODUCTION

At some time during most pumping tests, it is necessary to obtain 

successive depth-to-water-level measurements within short time intervals. Conventional means for making water-level measurements 

generally meet this requirement, but sometimes conditions are such 

that the conventional means are inadequate in one or more respects. The 

water-manometer-air-line assembly overcomes the inadequacies of the 

other methods.

The steel-tape method is perhaps the most commonly used method of 

measuring depth to water in wells. A measurement involves chalking 

the first few feet of the tape, inserting sufficient tape to reach below the 

water level, reading the tape at the measuring point, removing the 

tape, and reading the top of the submerged part of the tape. In many 

wells the last is difficult and sometimes impossible because cascading 

water or a wet casing or pump column may have wet the tape above the 

water level in the well.

The time required to obtain successive measurements depends on the 

depth to water. When the depth to water exceeds several tens of feet, 

the desired frequency of readings becomes impractical. Also, the 

probability of getting the tape stuck in the well increases with the 

number of insertions and the depth to the water surface.

The electric sounder, one model of which is described by LeBlanc 

(1966), has considerable advantage over the use of a steel tape in that

75
76 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'6,6-67

the time required for making successive measurements of water level 

is not dependent on the depth to water. The sounder line need be 

moved only the distance that the water level changed since the previous measurement to obtain a new measurement. Although electric 

sounders are designed to function satisfactorily even when water is 

cascading into a well or after the electrode passes through a column 

of oil floating on the water, malfunctioning occurs too often at a time 

when the collection of data is essential to the success of a pumping 

test. The lack of reliability under all conditions is the principal shortcoming of the electric sounder method.

Many large-capacity pumped wells are equipped with an air line 

(copper tubing or small-diameter pipe), an air gage, and suitable 

connections for supplying air to the line, generally by means of a 

hand-operated pump. Enough air is pumped into the system to drive 

all water from the air line and maintain it free of water. The pressure 

required for this condition is shown by the maximum reading that 

can be maintained on the air gage. This, in turn, will depend on the 

distance the air line is submerged below the water level in the well. 

The water depth at which the hydrostatic pressure equals the pressure 

indicated by the air gage is then subtracted from the length of the 

air line to obtain the depth to water.

The principal shortcoming of the above method is that the gage for 

measuring the air pressure rarely is sufficiently accurate or sensitive 

to obtain the data that are needed. This shortcoming is eliminated by 

use of a water manometer in conjunction with a modified air-line system that limits the length of the submerged part of the air line to 

the height of the water-manometer measuring tube.

PRINCIPLES OF OPERATION OF A WATER MANOMETER

Figure 1 represents an open vessel filled with water to a level, A ; 

an air tube with shutoff valve, C\ an airtight container filled with 

water to a level, Z>; and a relatively small-diameter tube, open to the 

atmosphere, that extends a short distance above water level, E. The 

pressure in the air tube is just sufficient to maintain the air line free 

of water. Under this condition, the vertical height of the water column, 

ED, equals the length, AB, that the air tube is submerged.

This is true because (1) the pressures at levels B and Z> are equal, 

(2) the pressures at A and E are equal (both atmospheric), (3) the 

differences in pressure between levels B and A and levels Z> and E 

therefore are equal, and (4) the differences in pressure arise from the 

hydrostatic pressure of columns of water of lengths AB and DE.

It follows, therefore, that the height of the water column in the 

tube above the level of the water in the airtight container equals the
WATER-MANOMETER-AIR-LINE ASSEMBLY 77

FIGURE 1. Sketch showing water levels in a watermanometer-air-line assembly when the air line is 

maintained free of water

depth to which the tube in the open container is submerged. If the 

open container is thought of as a well, the use of a water manometer 

for determining the depth to which an air line is submerged is readily 

apparent.

DESCRIPTION AND OPERATION OF THE ASSEMBLY

Figure 2 shows typical dimensions and materials for assembling a 

simple water-manometer-air-line apparatus. Sketch A shows dimensions for the manometer stand. Sketch B shows one combination of 

tubing, valve, and other accessories. This arrangement is secured to the 

base of the stand in any convenient manner. Sketch C shows the air 

line and its fittings.

A few drops of food coloring can be added to the water in the inkwell reservoir to facilitate reading the manometer. The reservoir is 

filled to about the halfway point, which then becomes the zero mark 

for any height of water level in the manometer tubing that is maintained as a result of submergence of the end of the air line below the 

water level in a well. The height of the water level in the tube above 

the zero level of the reservoir can be measured in a variety of ways. A 

length of steel tape graduated in feet and hundredths of a foot should 

be satisfactory; or marks showing feet, tenths of a foot, and midway 

points between tenths of a foot can be made on the support piece for 

the manometer tubing. Because the inside diameter of the glass tubing 

is small, the water level in the inkwell reservoir lowers insignificantly 

when water is displaced into the glass tubing of the manometer. Therefore, if the water level in the inkwell reservoir is at the zero mark of

312-670 O 68-
78 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'6:6-67

Groove

for 

tubing.

Small-diameter glass 

or translucent 

plastic tubini

Rubber stopper with 

holes that provide 

airtight fit for tubing.

Rubber tubing 

Ink 

bottle

Male end

of brass

union

Copper 

tubing,

Copper 

tubing

"Brass shutoff 

valve

"Tire-valve stem

Windshieldwiper hose. Copper tubing.

-y«"-OD polyethylene 

tubing

FIGURE 2. Sketches showing dimensions and materials for a watermanometer-air-line assembly.
WATER-MANOMETER-AIR-LINE ASSEMBLY 79

the scale when the air line is not submerged, the submerged distance 

can be read directly on the scale when the air line is submerged.

Any decrease in ease of reading the manometer when plastic tubing 

is used is offset by the fact that the plastic tubing is virtually unbreakable and flexible. Thus, the height of the manometer can be reduced 

when in transit or can be extended to increase the range of submergence 

over that range which is practical when using a single piece of glass 

tubing.

Figure 3 is a photograph of a manometer and its accessories. 

Mounted on the same stand is a mercury manometer that can be used 

instead of the water manometer should this be desirable. Also shown 

are a coil containing several hundred feet of small-diameter polyethylene tubing, a graduated steel tape with weight (to which has been 

taped several feet of air tube), and a type of air pump that is convenient for use with the manometer.

Figure 4 shows the assembly in use during a pumping test. The visegrip pliers often are convenient for maintaining the desired marking 

on the steel tape at the measuring point.

The procedure for measuring depths to water is to attach one end 

of the air-line tubing to the steel tape so that the end of the tubing is 

at the zero marking on the steel tape. Plastic tape can be used to make 

the attachment. The tubing and the steel tape are then attached at 

other convenient points, between 10 to 20 feet apart, until a length 

near the maximum depth to be measured is reached. Making the length 

of the tubing between intervals slightly longer than the steel tape 

will keep the tubing from interfering with the free hanging of the 

tape in the well. The reading of the tape at the measuring point should 

indicate the depth of the end of the air line below7 the point.

Determining the depth of the end of the air line on the basis of the 

steel tape marking at the measuring point is much more precise than 

using a calibrated air line because the length of the polyethylene tubing 

changes significantly with time, tension, and temperature. These 

changes can easily exceed 1 percent of the suspended length of the 

air line and are difficult to evaluate.

The other end of the air line is fitted to the manometer by means of 

the brass union shown in figure 2. The pump is attached to the tire 

stem valve and the shutoff valve is closed.

The weighted steel tape with air line properly attached is then 

lowered into the well until submergence of the air line is indicated by 

a slight rise of water level in the manometer. The amount of submergence is determined by (1) pumping sufficient air into the system 

to more than purge the air line of water, (2) closing the valve between 

the air pump and the system before the excess pressure is dissipated,
80 TECHNIQUES, WATER RESOURCES INVEiSTIGATIONS, 1966-67

FIGUBE 3. Water manometer, mercury manometer, and accessories.

and (3) noting the height at which the water column in the manometer tubing stabilizes above the water level in the reservoir.

The depth to water below the measuring point is the difference 

between the steel-tape marking at the measuring point and the height 

of the water column in the manometer.
WATER-MANOMETER-AIR-LINE ASSEMBLY 81

FIGURE 4. Water-manometer-air-line assembly in field use.

Computations are simplified by setting the full foot markings of 

the steel tape at the measuring point. Changes in water level are shown 

by changes in the height of the column of water in the manometer 

tubing between successive determinations of the amount of submergence. Although declining water levels can be ascertained in an 

airtight system merely by noting the decline of the water column in 

the manometer tubing, experience has shown that it is good practice 

to increase the pressure above that required for purging the air line 

for each determination of amount of submergence.

When the top of the column of water approaches either limit of the 

manometer tubing, the steel tape (and hence the end of the air line) 

is raised or lowered to again attain a satisfactory height of the water 

column.

A column of oil floating on the water in the well casing introduces 

problems regardless of the method of measurement, but these problems 

probably are less troublesome with the air-line method than with other 

methods. If the air line terminates in water below the oil, the manometer may be read directly without correction; but if the air line terminates in oil, corrections must be applied. The corrections can readily
82 TECHNIQUES, WATEK REi&OURCEiS INVESTIGATIONS, 196.6-67

be computed if the depth to the bottom of the oil column and the oil's 

specific gravity are determined.

These determinations can be made under stable water-level conditions by increasing the submergence, carefully measured by the steel 

tape, and comparing these differences in submergence with corresponding differences in manometer readings.

The ratio of a difference in manometer readings to a change in submergence will be 1 for all changes in submergence below the oil-water 

interface and will be less than 1, the specific gravity of the oil, for all 

changes above the interface.

At the end of the test, the plastic tape used to join the steel tape and 

the air line is removed. Lengths of air line up to 200 feet may be conveniently coiled, lasso style, into loops 2 feet or so in diameter. Greater 

lengths probably can best be handled by rolling the tubing onto a 

suitable spool from which any needed length can be unwound.

Small-diameter polyethylene tubing is available in continuous 

lengths up to 500 feet, in multiples of 100 feet, at a cost of a few cents 

per foot. The glass, copper, and rubber tubing in needed diameters and 

other materials are available locally. The air pump that is shown in 

figures 3 and 4 has the advantage of one-hand operation, which leaves 

the other hand free to operate the shutoff valve of the manometer.

Many variations can be incorporated in the system. In some areas 

where large changes in water level occur, a mercury rather than a water 

manometer may be more satisfactory. However, considerably more care 

must be used in preventing air leaks if the submergence is to be several 

tens of feet, and, of course, changes of water level of less than 0.05 foot 

will be hard to measure.

Another variation is the use of a pressurized air tank in lieu of the 

hand pump for purging the air line. However, care must be taken that 

all the air supply to the manometer is valved off completely when making a reading, or the height of the water column in the manometer will 

be too high by an unknown amount.

REFERENCE CITED

LeBlanc, R. A., 1966, Electrical water-level measuring reel, in Mesnier, G.N., 

and "Chase, E. B., compilers, Selected techniques in water resources investigations 1965: U.S. Geol. Survey Water-Supply Paper 1822, p. 38-42.
MINIMUM AND MAXIMUM WATER-LEVEL 

RECORDING DEVICES

By T. E. KELLY

ABSTRACT

To supplement periodic water-level measurements in observation wells, two 

inexpensive devices were constructed to determine the minimum and maximum 

water levels between visits to a well site. The minimum water level is determined by use of a float, and the maximum water-level device is a modification of a 

crest-stage station. The devices measure to an accuracy of 0.1 foot.

During the early 1940's a statewide network of observation w^ells was 

established in North Dakota, but for various reasons many of these 

wells were measured only biannually. The measurements were made 

during the spring and fall when the water levels were rising and declining, respectively. Consequently, numerous water-level measurements were obtained without knowledge of the annual range of waterlevel fluctuations. The measurements would have been more useful if 

they had indicated the annual minimum and maximum water levels for 

each well, and, consequently, the annual storage changes in the aquifer. 

The dates of the annual maximum and minimum water levels were 

not critical as they could have been approximated from precipitation 

data, records from observers, or automatic recorders measuring similar 

wells in the same general area.

Two inexpensive devices were designed to measure the minimum 

and maximum water levels in a well between inspections. The devices 

can be made and installed for less than $10, and each will last indefinitely.

Minimum water level is measured by use of a spool of fishing leader 

and a float of nearly any description. A standard 2i/£-inch water-level 

float has been used in North Dakota; but weighted cork, a dowel, or 

Styrofoam could also be used and at less expense. Nylon leader wound 

on a disc-shaped spool is obtainable in most sporting goods stores. It 

is available in a variety of strengths; the most satisfactory strength is 

15- or 18-pound test. As shown in figure 1, the leader is threaded 

through one or more eye hooks and attached to the float, which is lowered into a well.

83
84 TECHNIQUES, WATEK RESOURCES INVESTIGATIONS, 1966-67

FIGURE 1. Devices for measuring minimum and maximum water levels in wells. 

1, Plastic spool of nylon fishing leader; 2, nylon leader (15-pound test) ; 3, 

standard 2^-inch water-level float; 4, transparent %-inch polyethylene tubing 

containing powdered cork; 5, ^4-inch inside diameter (I'D) brass tubing; 6, ^4- 

inch (ID) brass tubing, slotted and filled with shot; 7, measuring points.

As the water level declines, the float pulls the leader material from 

the spool. When the water-level trend reverses, the leader becomes 

slack, but friction of the spool prevents it from rewinding. The lowest 

water level in the well since the previous inspection is determined 

by measuring the amount of leader between the measuring point and 

the float plus the distance from the float-leader connection to the
MINIMUM AND MAXIMUM WATER-LEVEL RECORDING DEiVICES 85

waterline on the float. It is advisable to mark the waterline on the 

float before the float is installed.

The maximum water-level device is a modification of a crest-stage 

station. This device consists of a length of transparent %-inch polyethylene tubing, two short lengths of ^-inch (ID) brass tubing, lead 

shot, and several pinches of powdered cork. An elbow of brass tubing 

is inserted into the upper end of the polyethylene tubing and is used 

to suspend the device in the well. Eight to 12 inches of brass tubing 

is crimped at one end, slotted with a hacksaw, and filled with lead 

shot or fishing sinkers. Several pinches of powdered cork are put 

into the plastic tubing, and the weighted brass tubing is attached 

to the lower end. The plastic tubing is suspended in the well with £he 

slotted brass tubing below the depth of anticipated maximum water 

level (fig. 1).

As the water level rises, the powdered cork rises on the water in 

the tube. After the peak is reached, the water level in the tubing declines ; but the cork adheres to the walls of the tube and marks the maximum water level. The maximum level is determined by gently pulling 

the tubing from the well and measuring the distance between the 

measuring point and the top of the cork. Any kinks in the polyethylene 

tubing will prevent the movement of the cork and will cause an 

anomalous indication of maximum water level. The cork should be replaced annually.

The two devices can be used in nearly any well larger than 2 inches 

in diameter. In smaller diameter wells a weighted dowel instead of the 

standard float can be used satisfactorily. Deep water levels may be a 

limiting factor. At depths exceeding 50 feet there is appreciable stretch 

in the nylon leader; however, this can be reduced by using a larger 

diameter leader. Fine copper wire can also be wrapped on the spool 

and used instead of leader material. Transparent polyethylene tubing 

costs about $0.20 per foot and is the most costly item of the installation.

The greatest advantage in using these devices is that three waterlevel measurements can be obtained for each visit to the site regardless 

of the interval between visits. Figure 2 shows the relation of the 

monthly minimum and maximum water levels at a particular well 

to the measurement made during each visit for the period May 1965 

to November 1966. During the declining phases the taped measurements correspond to the minimum monthly water levels; during the 

rising phases the taped measurements correspond to the maximum 

monthly water levels.

A pilot test was made using these two devices in a well having a 

continuous recorder. The maximum and minimum water levels recorded by the two devices were within 0.1 foot of those shown by 

the recorder.
86 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19 6-6-6 7

asured water 

level

v^axirrum

'\

X - 6 \

water level

^

JFMAMJJASOND 

1965

JFMAMJ JASOND 

1966

FIGURE 2. Hydrograph showing relation of monthly measurements to the 

minimum and maximum water levels in one observation well.
SERVOPSYCHROMETER

By WOODEOW L. YONTS, Jr.

ABSTRACT

A servopsychrometer has been designed that obtains accurate and instantaneous relative humidity observations, which are used to check the operation of 

recording hygrothermographs used in water resources investigations.

Greater water use and water shortages in recent years have emphasized the need for more reliable means of measuring factors affecting 

evaporation. As more reservoirs for water supply and other purposes, 

particularly heat dissipation, are constructed, water losses due to 

evaporation can be appreciable. A direct method of measuring evaporation from a free-water surface has not been developed; consequently, 

various indirect techniques have been used. These techniques include 

mass transfer, energy budget, water budget, and pan evaporation.

Relative humidity readings are part of all these techniques except 

the water-budget method. Generally, relative humidity and dry-bulb 

temperature are continuously recorded on a hygrothermograph. A 

sling psychrometer normally is used to check the hygrothermograph. 

The sling psychrometer consists of wet- and dry-bulb thermometers 

mounted on a common back to which a short length of chain with a 

wooden handle is attached. Ventilation is provided by whirling the 

psychrometer.

The servopsychrometer was developed when differences greater than 

2 percent in hygrothermograph and sling psychrometer readings were 

common in normal operation. These differences were attributed to two 

factors: (1) the hygrothermograph was inside a louvered shelter, but 

the sling psychrometer readings were taken outside, and (2) the inability of the observer to read instantaneous maximum depression 

of the mercury in the wet-bulb thermometer on the sling psychrometer.

The servopsychrometer was designed so that the maximum depressions of mercury of the wet-bulb thermometer are readily visible. Its 

size allows it to be used near the hygrothermograph inside the instrument shelter. The shelter is the standard U.S. Weather Bureau meteorological instrument shelter known as the cotton-region type.

87
88 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'66-67

The servopsychrometer consists of a small direct-current motor, 

a 6-blade fan, two 6-volt batteries, and wet- and dry-bulb thermometers 

on a common holder. The thermometers and the motor, to which the 

fan is attached, are mounted on a frame made of Plexiglas (fig. I A). 

The 6-blade fan was formed by joining together two 3^-inch-diameter 

propellers from plastic model airplanes. The motor operates best on

FIGUBE. 1 (above and facing page). Servopsychrometer. A, Parts, except power 

source, mounted on stand.
SERVOPSYCHROMETER 89

about 12 volts and can be used on up to 24 volts. A convenient power 

source is two lantern-type 6-volt batteries wired in series. Motors are 

available at most hobby shops. Plexiglas was used for the frame, but 

wood could be substituted. The thermometers, wet- and dry-bulb, were 

detached from the sling of a sling psychrometer and mounted on the 

Plexiglas stand. A hinge arrangement (fig. 1Z?) permits the thermometer holder to swing out from the stand and the wet-bulb (wickB, Hinge arrangement for dipping wick on wet-bulb thermometer.
90 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 19&6-67

covered) thermometer to be dipped into a small bottle of distilled 

water.

The servopsychrometer motor is small, and heat transfer to the 

thermometers is negligible. If a larger motor is used, heat generation 

may be significant enough to cause erroneous readings. However, a 

larger motor can be used by placing the fan in a reverse position at one 

end of a funnel-shaped box and by mounting the thermometers at 

the opposite end of the box. This would permit air to be pulled through 

the funnel from the thermometers toward the motor and prevent the 

heat from passing across the thermometer bulbs.

Maintenance of the servopsychrometer is relatively simple. The wick 

of the wet-bulb thermometer should be changed at least once a month 

or more frequently if necessary to keep a clean wick on the bulb. 

Deposition of mineral salts on the wick, or a dirty wick, will cause 

erroneous wet-bulb readings. The motor should be oiled periodically. 

Battery life averages about 6 months.

The total cost of the parts and construction of the servopsychrometer, including 1 hour of labor, is about $15.

The servopsychrometer has been in operation since June 1962, and 

results have been excellent. Simultaneous humidity readings have differed 2 percent or less when both instruments were in the shelter. 

Readings and interpretations of the hygrothermograph chart have 

been more accurate.
RAFT FOR EVAPORATION-MEASUREMENT EQUIPMENT

By RICHAED U. GROZIER

ABSTRACT

Deterioration of steel barrels in rafts used to support equipment for determining evaporation on reservoirs was eliminated by using plastic foam instead of 

steel barrels for raft buoyancy. Special frames were devised to hold the plastic 

foam and the frames were fastened together in a design that made the new 

raft both safe and sturdy.

Evaporation from reservoirs has been studied for several years 

by the U.S. Geological Survey. Some of the principal types of data 

for such studies must be collected by instruments situated on rafts 

moored near the center of reservoirs. For example, windspeed must 

be recorded by an anemometer and surface temperature of reservoir 

water by a thermometer near the center of a reservoir to accurately 

determine evaporation by the mass-transfer theory. A study by Harbeck (1962, p. 102) briefly mentions the type of raft commonly used 

one in which empty steel barrels provide buoyancy.

A steel-barrel raft is made of four 55-gallon steel barrels attached 

together inside a welded frame of steel angles. About every 2 years the 

steel barrels have to be replaced because of rusting. Each replacement 

job amounts to practically rebuilding the raft because the welded 

framework must be taken apart and then reassembled. The barrel 

rafts also have very little freeboard and are so unstable that it is 

dangerous for more than one man to be on a raft at one time.

Another type of raft can be built, however, that eliminates many 

of the problems of the barrel raft. Instead of steel barrels, slabs of 

plastic foam are used to give buoyancy. Plastic foam can be obtained 

in almost any desired size or shape and it will support about 60 pounds 

per cubic foot.

A construction diagram of a raft built with plastic foam instead of 

barrels for buoyancy is shown in figure 1. Two slabs of plastic foam, 

each 8 feet long, 25 inches wide, and 12^ inches deep, are used. Each 

slab weighs about 20 pounds but will keep afloat nearly 1,000 pounds of 

load. A single slab easily floats the weight of a man and the instruments 

used to collect data on windspeed and surface-water temperature; how91
92 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196>6-67

TOP VIEW 

 6' 

|-«- 253/4'-'

Brackets 

for instrument

house. 

3"channek

2" pip

M L^A

U.

 ¥

12%"

r

nemometer pipe

li /.PJastic foamy.

 ~ , :'.;. *;;;; . .. 

l^Plastic fpam-;

1

1

|

t

13»/4"

1

\Motor scooter EN[) V|EW ^Chain and swivel

tire for boat 

fenders \

to anchor

FIGUKE 1. Details of construction of raft in which plastic foam slabs are used

for buoyancy.

ever, for greater stability and ease of design, two slabs of plastic foam 

are used. Because plastic foam is soft and its edges are easily damaged, 

a frame made of 2- by 2- by ^-inch steel is placed around each foam 

slab. Each frame is made in two pieces, top and bottom, and then 

joined together at the corners around a foam slab and at the center on 

the outside. Each half frame is the same except that a redwood plank 

is attached to one to form a walkway for tending the instruments. When 

the two frames around the foam slabs are fastened together, a sturdy 

compact unit is formed that weighs about 250 pounds (including 

a shelter for the instruments). This unit will take considerable rough
RAFT FOR EVAPORATION-MEASUREMENT EQUIPMENT 93

treatment without damage to the plastic foam slabs. All metal parts 

are given one coat of rust-preventive paint and one coat of aluminum 

paint. The completed raft is shown in figure 2.

FIGURE 2. Finished raft with anemometer and instrument house in place.

Some advantages of plastic-foam rafts over barrel rafts are:

1. Greater stability, and, therefore, safety.

2. Will not sink, even if perforated many times by rifle fire.

3. Rides more evenly.

4. Nonsusceptibility to chemicals in water.

5. Low maintenance costs.

Although it costs slightly more to make a plastic-foam raft (total 

cost about $130) than a barrel raft, the maintenance of a foam raft is 

much less than that of a barrel raft. The Texas District of the Water 

Resources Division, U.S. Geological Survey, has been using foam rafts 

for more than 3 years, and no maintenance has been required. Some of 

the rafts have been moved from one reservoir to another by truck and 

have not been damaged.

REFERENCE CITED

Harbeck, G. E., Jr., 1962, A practical field technique for measuring reservoir 

evaporation utilizing mass-transfer theory: U.S. Geol. Survey Prof. Paper 

272-E, p. 101-105.

312-670 O 6S
WATER-STAGE AND RAINFALL DUAL RECORDER

By GEORGE F. SMOOT AND THOMAS J. BUCHANAN

ABSTRACT

An instrument that records both cumulative rainfall and flood stages is used 

on streams with small drainage basins to help dlefine flood frequencies. The 

stilling well and stage-recording mechanism are installed so that 5-, 10-, or 20- 

foot ranges of a stage above a predetermined gage height can 'be recorded during 

24 hours; more than 24 hours of flood record on one chart may be difficult to read. 

Record automatically begins after water stage reaches the predetermined height. 

The rainfall recorder can register any number of inches of rain because of a 

siphon system attached to the rainfall-measuring reservoir. After 5 inches of 

rain have fallen, the siphon empties the reservoir and a new recording cycle 

is begun. Rainfall record is continuous between service visits to an instrument, 

which may be 6 to 8 weeks apart if no flood occurs. Both cumulative rainfall 

and water stage are recorded on one polar coordinate chart with the time of day 

(but not the date) of an event defined. Rainfall is recorded with an accuracy of 

±0.025 inch; different stage ranges are recorded with different accuracies of 

from ±0.025 foot for a 5-foot range to ±0.10 foot for a 20-foot range.

INTRODUCTION

Many State and Federal agencies are presently engaged in programs 

to define flood frequencies in small drainage basins. Additional studies 

are being proposed, particularly in basins of 1 to 10 square miles in 

area. Most of the present programs provide for recording peak stages 

by use of the crest-stage gage.

Although data on peak stages on small streams (for the collection 

of Avhich the crest-stage gage is an efficient device) are the primary 

facts needed to determine flood frequencies in small drainage basins, 

flood hydrographs and rainfall records are also extremely helpful if 

they can be obtained at a reasonable cost. But to economically record 

both a chart of changes in water stage (a hydrograph) and rainfall 

data, an instrument is needed that records two types of information 

simultaneously. In addition, the instrument should be simple, inexpensive, sturdy, and automatic and should require a minimum of 

servicing. 

94
WATER-STAGE AND RAINFALL DUAL RECORDER 95

When studies of flood frequencies in small drainage basins were initiated, no commercial recorders were available that fulfilled these requirements. Therefore, it was decided to design and build the type of 

recorder needed. In 1962 the Instrument and Development Unit, Water 

Resources Division, U.S. Geological Survey, developed a small waterstage recorder and distributed 100 units to Survey field offices. The 

experience gained during the use of these water-stage recorders led 

to the development of an improved and more versatile instrument that 

fulfills the requirements of a device for use in a small drainage basin.

The new instrument is called an SR recorder (fig. 1) because it 

registers both stage and rainfall. It consists of four basic sections the 

chart table and chart drive, the stage-recording mechanism and stilling 

well, the rainfall-recording mechanism and rainwater reservoir with 

siphon, and the housing.

CHART TABLE AND DRIVE

The chart table and chart drive consist of a S^-inch-diameter horizontal disc (the chart table) that is made to rotate about a central vertical axis by a battery-wound timing mechanism. The timing mechanism insures that the chart-table speed is one complete rotation each 

24 hours and that the rotation is evenly distributed. A small flashlight 

battery is used to wind the timer. The battery usually lasts about 6 

months. A polar coordinate chart (made of Mylar) fits on top of 

the chart table. It has radial lines to mark time divisions and concentric circles to indicate levels of stage or amounts of rainfall. The 

usable width of the chart in recording either rainfall or stage changes 

is 2 inches. The entire chart table and drive can be removed from the 

SR recorded by unfastening three screws. (See fig. 2.)

STAGE RECORDER

Part of the stage recorder is shown on the right side of figure 2. A 

2-inch-diameter pipe is fastened inside the pipe flange to act as a stilling well. The lower end of the pipe is covered with a perforated pipe 

cap so that wrater can enter when the stream reaches a certain stage. 

When water enters the pipe, a l^-inch-diameter plastic float rises with 

the water level inside the pipe. The float is suspended from the float 

wheel by several feet of light stainless steel cable that will not stretch 

or contract when the temperature or humidity changes. Also suspended 

inside the stilling-well pipe is a counterweight, w7hich is attached to the 

counterweight drum by a few feet of silk or nylon fishline. Because the 

counterweight line is not attached directly to the float line, it is not 

important if the counterweight line stretches or contracts slightly.
96 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

FIGURE 1. Assembled water-stage and rainfall dual recorder viewed from the 

rear: a, Chart drive; 6, stage-recording mechanism; c, stage stilling well; d, 

rainfall-recording mechanism; c, rainwater reservoir; /, siphon; g, housing; 

h, float; and *', counterweight.
WATER-STAGE AND RAINFALL DUAL RECORDER 97

FIGURE 2. Front view of SR recorder before assembly and attachment to stilling 

well and rainwater reservoir.

The weights of the float and counterweight and the diameters of 

the float wheel and the counterweight drum are arranged in such a 

way that the line to the float is always kept just taut but without strain 

whether the float and the water are rising or falling. As the float and 

the counterweight go up or down, the counterweight drum or the float 

wheel is given a rotary motion, which in turn is transmitted to the 

stage-recording carriage screw.

As the carriage screw turns, a linear horizontal motion is given to 

the stylus assembly because a pawl attached to the assembly fits into 

the carriage screw groove and must follow backward or forward along 

the groove as the screw moves. A piece of pencil lead inserted in the 

stylus assembly traces the horizontal movements of the assembly as the 

chart table slowly rotates.

Carriage screws are available to scale 5, 10, or 20 feet of change of 

stage onto the 2-inch space on the chart, according to what range of 

stage is to be recorded. All the screws are the same length, but the 

screws for large ranges in stage have a greater number of groove turns. 

All the stage-recording carriage screws have right-hand threads.

The stilling-well pipe must be as long as the range of stage to be 

recorded plus adequate length for the counterweight to move up and
98 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

down without touching the float. A stilling well for recording a 20- 

foot range of stage would need to be about 23 feet long. A pipe for 

recording a 5-foot range of stage would need to be a little over 6 feet 

long.

RAINFALL RECORDER

Part of the rainfall recorder is shown on the left side of figure 2. 

The arrangement and function of pipe, counterweight, float, float 

wheel, carriage screw, and stylus assembly is virtually the same as in 

the stage-recording mechanism. A few differences should be noted, 

however. The carriage screw for the rainfall-recording mechanism has 

a left-hand thread, and only screws that scale 5 feet of change of stage 

in the rainwater-reservoir pipe onto the 2-inch space on the chart are 

available. While the trace of the stage-recording mechanism on the 

chart shows the true time at which a stage change occurs, the trace of 

the rainfall-recording mechanism is 12 hours ahead of the time of the 

actual event. This displacement is because the chart time divisions are 

alined with the stage-recording mechanism and the rainfall-recording 

mechanism is 180°, or twelve 1-hour divisions on the polar coordinate 

chart, away from the stage-recording mechanism.

The rainwater-reservoir pipe is 2 inches in diameter and must be a 

little over 6 feet long. The lower end is closed with a pipe cap and the 

upper end is attached to the pipe flange on the left side of the SR 

recorder. Water drains from the rain collector built into the recorder 

cover through a tube into the rainwater-reservoir pipe. The collector 

and pipe are built so that water rises 1 foot in the pipe for 1 inch of 

rain. When the reservoir pipe is installed, the bottom 2 inches is filled 

with water so that the float will sit properly in the pipe; the carriage screw and stylus assembly are adjusted so that 2 inches of water 

in the pipe reads as 0 inches of rainfall on the recording chart. A small 

amount of light oil is placed on the surface of the water to curtail 

evaporation, which would make the water fall below the "no rainfall" 

level.

One of the most important parts of the rainwater-reservoir pipe is 

the external siphon (see fig. 1), which consists of a long U-shaped piece 

of copper tubing. One leg of the siphon tubing extends below the "no 

rainfall" water level on the outside of the reservoir pipe. The other leg 

of the siphon is exactly 5 feet long, and the end is soldered to a small 

hole in the reservoir pipe at the "no rainfall" level. This hole leads 

to the inside of the rainwater-reservoir pipe. When enough rain has 

fallen (5 inches) so that the water level has risen 5 feet above the "no 

rainfall" level, or to the top of the inverted U of the siphon, the siphon 

is tripped and the accumulated 5 feet of water in the reservoir pipe 

drains out through the siphon in about 2 minutes. The rainfall-record-
WATER-STAGE AND RAINFALL DUAL RECORDER 99

ing stylus moves back to read 0 inches of rainfall on the chart, and a 

new cycle of rainfall record is begun. Because of the siphon arrangement, an unlimited number of inches of rain can be recorded.

During servicing visits to the SR recorder, the accumulated water in 

the rainwater-reservoir pipe can be drained either by pouring more 

water into the pipe to trip the siphon or by taking out a small pipe 

plug at the "no rainfall" level. Either method drains out any water 

above the "no rainfall" level and returns the stylus to its original 

setting. One point should be remembered, however. If the rainwaterreservoir pipe is set so low that both the siphon outlet and the pipe 

plug are below high stream stages, the siphon will not work and the 

pipe plug cannot be removed during high water. In other words, during 

high water only 5 inches of accumulated rainfall could be recorded 

and considerable rainfall record might be lost. One solution to this 

problem is to connect the siphon outlet to a watertight drum or reservoir equipped with a snorkel tube that extends above any likely high 

water. Connected to this extra reservoir, the siphon will operate normally even though its outlet from the recorder reservoir is below the 

river level. The snorkel tube is necessary to keep the air pressure in 

the extra reservoir the same as air pressure outside if it were not the 

same, the siphon would not operate properly.

DUAL RECORDER HOUSING

The housing of the SR recorder consists of a cover and a base plate 

with flanges on the bottom to accommodate two 2-inch-diameter pipes 

(fig. 3). The pipes are attached to the flanges by means of setscrews. 

One of the pipes, generally the stage pipe, supports the housing and is 

firmly fastened to some structure in the stream. The cover of the housing is attached to a side edge of the base plate by a hinge (fig. 2). One 

side of the cover is built in a special shape to be a rainfall collector. 

Rainwater runs through a hole in the center of the collector into a drain 

tube (fig. 2) and from there into the rainwater-reservoir pipe. The 

cover can be locked to the base plate to prevent vandalism.

DISCUSSION

SR recorders are purposely installed in such a way that they will 

record only the flood stages of a stream. The bottom of the stilling 

pipe of the stage recorder is set at the height at which it is desired 

that stage recording begin. Unless water in a stream rises past the 

bottom of the stilling-well pipe arid moves the float upward, the stylus 

of the stage-recording mechanism stays on the "0 stage" mark, or the 

innermost circle on the polar coordinate chart, and inscribes an identical circle each day as the chart rotates continually. If water rises past
100 TECHNIQUES, WATE'R RESOURCE® INVESTIGATIONS, 196'6-67

FIGURE 3. Housing of water-stage and rainfall dual recorder with cover closed. 

Note opening for rainwater.

the bottom of the stilling well and moves the float upward in the stage 

pipe, the stylus assembly moves from the inner circle on the chart toward the edge as the water rises. Service personnel should put a new 

chart on the recorder after about 24 hours of stage recording; unless 

they do, the stage record from one 24-hour period may be confused with 

record from the next 24 hours.

The accuracy with which stage can be registered, if the recorder is 

functioning properly, depends upon the range of stage to be recorded. 

The larger ranges of stage can be recorded with less precision than the 

smaller ranges. Assuming that a recorder chart can be read to the 

nearest 0.01 inch, a 5-foot range of stage can be recorded to the nearest 

0.025 foot, a 10-foot range of stage, to the nearest 0.05 foot, and a 

20-foot range of stage, to the nearest 0.10 foot.

Unlike the stage recorder, which only registers after water reaches 

a certain height, the rainfall recorder indicates any measurable 

quantity of rain that occurs. The rainfall stylus inscribes identical circles on the innermost chart circle, or the "0 rainfall" mark, 

until a rain. Then, as the float in the rainwater reservoir moves upward, 

the rainfall stylus moves toward the edge of the chart. When the 

rain stops, the float in the reservoir stops rising, and the stylus starts 

a new series of circles at some distance from the chart center. This
WATER-STAGE AND RAINFALL DUAL RECORDER 101

pattern continues until 5 inches of rain have fallen. Then the rainwater reservoir empties itself, the stylus moves back to its original position, and a new recording cycle begins. While this method of recording 

is very useful in determining the total amount of rain that falls at a 

recorder site during a period, it does not indicate the date of any particular rainfall event. If the date of a rain is needed, it must be determined from other sources than the recorder.

The accuracy with which rainfall can be recorded is quite high. 

Again, assuming that a recorder chart can be read to the nearest 0.01 

inch, rainfall records can be read to the nearest 0.025 inch.

Besides being used as components in a dual stage and rainfall 

recorder, the rainfall recorder and the stage recorder can be used separately if it is desired to register only rainfall or stage at a location.
POLAR COORDINATE CHART READER FOR 

STAGE-RAINFALL RECORDER

BY V. B. SAUER

ABSTRACT

The river-stage and rainfall dual recorder makes graphs on a polar coordinate 

chart that may be difficult and time consuming to read if done by inspection or 

with scales. The polar coordinate chart reader determines the coordinates of any 

point on the chart simply, accurately, and consistently. The chart reader consists 

of a time mechanism and a stage mechanism arranged so that simultaneous readings of time and stage (or cumulative rainfall) can be obtained with one setting 

of a stylus. Time intervals read can be as small as 10 minutes, and they can be 

estimated to 5 minutes. Stage can be read to 0.01 foot and rainfall to 0.01 inch. 

However, the accuracy of such readings depends on the accuracy of the original 

chart.

INTRODUCTION

The river-stage and rainfall dual recorder (or SR recorder) graphs 

stage and rainfall simultaneously on a single polar coordinate chart. 

Visually reading numerous point coordinates from such a chart is 

difficult and time consuming. Inaccurate readings may result.

One problem in reading a polar coordinate chart with radial divisions 

representing time intervals, such as hours, is that the time subintervals 

are hard to estimate because the distance along arcs for a subinterval is 

different at the outer edge of the chart than at the inner edge. On the 

chart from an SR recorder, for example, the distance that represents 

1 hour along the innermost arc is 0.12 inch; the distance that stands 

for 1 hour along the outermost arc is 0.65 inch.

Concentric circles, which represent cumulative rainfall or stage 

measurements, are always equidistant on an SR-recorder chart. But 

the same distances between circles (always 0.10 inch) may represent 

different stage changes on different charts because of the different 

carriage screws that can be used to scale stage changes. And on many 

charts the stage scale is not the same as the rainfall scale. (See the 

preceding article by Smoot and Buchanan.) All these differences of 

scale complicate the task of a person who reads and interprets an SRrecorder chart. 

102
CHART REIADER FOR STAGE,-RAINFALL RECORDER 103

Another fact that interpreters of SR charts must remember is that 

rainfall records are displaced 12 hours ahead of the actual rainfall. 

Therefore, time corrections are required in reading the chart.

The polar coordinate chart reader (see fig. 1) was originally designed to simplify the reading and interpretation of SR-recorder 

charts. The reader consists of two basic units the time mechanism 

and the stage mechanism arranged so that simultaneous readings of 

time and stage coordinates are obtained with one stylus setting. With 

modifications, such as a larger chart table and different scale markings, 

the reader could be used on any polar coordinate chart.

FIGURE 1. Polar coordinate chart reader designed specifically for SR-recorder

charts.

TIME-BEADING MECHANISM

The time mechanism consists of a vertical shaft, set in bearings, 

directly connected to a 12-inch-diameter time wheel and to a 5y2- 

inch-diameter chart table. (See figs. 2 and 3.) The shaft is a standard 

SR-recorder carriage screw machined to fit the bearings and chart 

table, which are also obtained from an SR recorder. The time wheel 

is a %-inch-thick plywood disk attached to the shaft by means of a 

float wheel from an SR recorder. The time scale is printed on a 12- 

inch-diameter piece of scale-stable drafting film, which is glued to the 

top of the plywood disk. The chart table and time wheel are shown
104 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19-&6-67

 Time window and indicator

A- - 

Centerhne of 

^mounting holes

Float wheel, screw.

and carriage

assembly from

SR recorder

FIGURE 2. Top view of polar coordinate chart reader showing stylus assembly, 

carriage screw, and float wheel of stage-reading mechanism and cutaway view 

of time wheel. A-A' is line of section shown in figure 3.

in figure 4. A more durable time wheel could be constructed from a 

material that is not likely to warp, such as aluminum plate or stainless 

steel plate. Markings could be scribed or etched on such a material. 

All the time-reading mechanism, except the chart table, is enclosed 

in a box, as shown in figures 2 and 3. A small window in the cover 

plate shows the time to which a chart has been turned. Time markings show hours or 10-minute subdivisions of hours (fig. 2).
CHART READER FOR STAGER-RAINFALL RECORDER 105

Float wheel, screw, and

Note: The face of the float wheel is marked along its 

periphery to serve as a stage scale (see detailK attached to 

bolts

r

i

CN

"a, '

* J

 "

-*

DETAIL OF STAGE SCALE

^Periphery of float 

wheel marked into sty|us assembly. 

100 equal parts \

Carriage screw \

"

S R chart-table assembly 

IH-diameter hole in cover platev \

|" 3plywood /8

* 1 * i

12 diameter plywood time wheer l"7

Note- If time wheel is n 

ner material (such as

provide ^6" clearanc 

wheel and cover plate

2 "by 2 15/ie'

ade from thin 

's" aluminum), 

be adjusted to 

between time

by 131/2" oak block 

1 A

-p nli R

Needle 

1 I point 

jT^'Stylus

n

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tin

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n

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at-wheel assembly attached to 

le wheel with wood screws

^ SR- recorder ball-bear ng carriage

 Vertical shaft (made from SR carriage screw 

with lower end machined to fit ball bear 

ing and upper end machined to fit chart 

table)

. SR-recorder ball bearing

tr i

 -1" by 2" by '/«" metal retaining plate

3'8 " plywood

 * 3'8 " 

It ..

4

FIGURE 3. Section A-A' through chart reader shown in figure 2. Sections of 

stage-reading mechanism and of time wheel (attached to chart-table assembly). Detail of stage scale marked on inside of float wheel of stage-reading 

mechanism.

FIGURE 4. Chart table and time wheel with cover of box removed.
106 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, lQ'66-67 

STAGE-READING MECHANISM

The stage-reading mechanism consists of a float wheel, carriage 

screw, stylus assembly from an SR recorder, and a stage indicator. 

The stage scale is printed on a 4-inch-diameter piece of drafting film, 

which is glued to the inside face of the float wheel. A needlepoint 

stylus is inserted into the stylus assembly to use as a pointer at locations on the SR chart attached to the chart table. The stage scale, stage 

indicator, and stylus are shown in figure 5.

The stage-reading mechanism is attached to the cover plate of the 

chart-reader box and is alined so that the needlepoint stylus, as it 

moves horizontally, will trace a line exactly above one of the radial 

lines marking an hour on an SR-recorder chart. This alinement must 

be as nearly perfect as possible so that accurate time readings will 

be obtained near the center of a chart as well as at the edge. A stage 

indicator is set near the right edge of the stage scale (fig. 2).

FIGURE 5. View of stage-reading mechanism with stylus and stylus assembly

alined with chart.
CHART RE1ADER FOR STAGE-RAINFALL RECORDER 107 

BEADING AN SB CHABT

Eeading an SR chart correctly requires that the correct carriage 

screw be used in the stage-reading mechanism. That is, a chart on 

which a 5-foot range of stage was recorded requires a carriage screw 

in the reader that scales 5 feet into 2 inches (the effectiveness width 

of the chart); a chart on which a 10-foot range of stage was recorded 

requires a carriage screw that scales 10 feet into 2 inches. Reading a 

group of charts can be done with a minimum of carriage-screw changes 

by reading all charts with a 5-foot stage range in one group, all 

charts with a 10-foot stage range in another group, and all charts 

with a 20-foot stage range in a third group. All rain records should 

be read when the 5-foot stage range carriage screw is in the reader. 

A screwdriver, a small Alien wrench, and a fewT seconds are all that 

are required to change a carriage screw.

To read a chart, place it on the chart table and turn the table 

until an hour marking shows in the time window. Then slip the chart 

until the same hour is alined with the needlepoint stylus. Fasten the 

chart to the table with a clip or tape; the time should now read correctly in the time window when any other time on the chart is alined 

with the stylus. The stage is set by alining the stage indicator with the 

stage wheel when the stylus is pointing at a known stage on the chart 

(generally the base line or peak stage). Usually the stage-scale wheel 

is loosened and turned to read the correct hundredth of a foot next 

to the indicator; when it reads correctly, the stage-scale wheel is tightened. Stage corrections, if uniform, are therefore eliminated. One 

revolution of the stage-scale wTheel represents 1 foot of stage; therefore, 

foot readings must be remembered.

The stage record of the chart is read starting from the first time at 

which the stage trace is above the base line (innermost concentric circle) . The stylus is moved until it is directly over the stage trace. The 

stage height and time are noted. The time wTheel is advanced the desired time interval, the stylus is relocated just over the stage trace, and 

the stage scale is read at the indicator. This procedure is continued 

throughout the period of stage rise and fall, and the readings are 

tabulated in a convenient form for determining discharge or for 

future reference. The same procedure is used for the rainfall record.
108 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

Compensation for the 12-hour displacement of the rain record can be 

immediately made by slipping the chart to read the correct time 

rather than the 12-hour-in-advance time.

The accuracy of reading a flood-stage hydrograph or rainfall record 

in this manner depends upon the accuracy of the original record. With 

reasonable care, time can be read at 5- or 10-minute intervals. Although stage can be read to 0.01 foot on any chart with the chart 

reader, the accuracy of the figure depends on the stage range of the 

original recording. Rainfall can be read to 0.01 inch. If consistent 

methods are used throughout the reading of a chart, good readings 

can be obtained. One innovation that might improve accuracy somewhat would be use of a light source to project a pinpoint of light on 

the chart instead of using the needlepoint stylus. This technique would 

insure better alinement with the stage or rainfall trace.
CORRECTING RIVER VELOCITIES MEASURED FROM 

AN UNANCHORED SHIP

By LTJTHER C. DAVIS, Jr.

ABSTRACT

The problem of correcting observed Amazon River velocities that were measured from a nonstationary ship was solved by measuring the distance the 

unanchored vessel drifted during the 40- to 50-second velocity measurement 

period. By applying the rate of drift, in feet per second, to the observed velocity 

reading obtained by current meter, a corrected river-velocity reading was 

computed.

INTRODUCTION

During the summer and fall of 1963, a field party composed of 

engineers and technicians of the U.S. Geological Survey, the University of Brazil, and the Brazilian Navy made discharge measurements 

of the Amazon River at Obidos, Brazil, a point about 500 miles upstream from the river's mouth. Owing to the absence on the Amazon of 

any river-spanning structures such as bridges or cableways, the conventional platforms from which most large rivers are measured in the 

United States, a ship of the Brazilian Navy was used as the measurement platform. Use of a ship in making discharge measurements normally would present no particular problem if the vessel could be 

anchored at each of the observation points of the selected measuring 

section. However, because of depths as much as 200 feet, anchoring the 

ship at each of approximately 25 observation points across the measuring section was found to be overly time consuming and mechanically 

impractical. It was therefore necessary to make measurements from 

an unanchored ship held as closely as possible on station by varying 

the engine speed and rudder settings. By making velocity measurements from an unanchored ship, however, an error was introduced to 

the observed river-velocity reading because of the drift of the ship 

that occurred regardless of expert ship handling during the 40- to 

50-second measurement period. To determine the magnitude and direction of this error, a method was employed that utilized a tellurometer 

system, a theodolite, and a walkie-talkie radio circuit.

109

312-670 O 68 8
110 TECHNIQUES, WATER RESOURCE'S INVESTIGATIONS, 1966-67

EQUIPMENT

The tellurometer, for measuring distance, is in common use by the 

Topographic Division of the Geological Survey for surveying, but it 

has not been previously used in stream gaging. The system consists of 

a master unit and a remote unit; it operates much on the radar principle. In practice a series of microwaves are transmitted by the master 

unit. These impulses are received by the remote unit, run through 

the circuitry of the receiver, and transmitted to the master unit. The 

time it takes these impulses to travel the round trip is indicated on 

the instrument panel of the master unit. These readings are then converted to distance in feet. During the Amazon measuring operations, 

the master unit was mounted near the bow of the ship (fig. 1), and 

the remote unit was mounted on shore at one end of the measuring 

section (fig. 2). A theodolite, a compact surveying instrument used in 

this application for measuring azimuth angles, also was mounted on 

shore alongside the remote tellurometer unit (fig. 2). Operators were 

required for the theodolite and for each of the two tellurometer units.

FIGURE 1. Stream-gaging equipment arrangement on bow of Brazilian naval 

vessel. Master tellurometer indicated by arrow.
RIVER VELOCITIES MEASURED FROM UNANCHORED SHIP HI

FIGURE 2. Theodolite (left) and remote tellurometer (right) on right bank 

of Amazon River measuring section at Obidos, Brazil.

PROCEDURE

After the ship had been stabilized as accurately as possible at the 

observation station of the measuring section, the following procedure 

was used to determine the corrections to be applied to the observed 

velocity readings:

1. When the current-meter count was started, the shipboard (master) 

tellurometer operator instantly recorded the exact distance the 

ship was located from the reference point on shore where the 

remote tellurometer and the theodolite were located.

2. Concurrently, the shore-based theodolite operator, having received 

the starting signal by walkie-talkie, recorded the azimuth angle of 

the ship's location.

3. As soon as the current-meter count was completed, from 40 to 50 

seconds later, second tellurometer (distance) and theodolite (azimuth angle) readings were made. 

Referring to figure 3, and bearing in mind that angle a was in almost
112 TECHNIQUES, WATE.R RESOURCES INVEOTIGATIONS, 1966-67

every case smaller than 1°, we can see that for practical purposes the 

difference between the first (A-B) and second (A-C) tellurometer 

readings is the lateral distance (B-Br ) the ship moved during the 40- 

to 50-second interval the current-meter count was being made. The 

difference between the theodolite readings is the angular distance (a) 

the ship moved during the same interval of time in an upstream or 

downstream direction. Knowing the linear ship-to-shore distance, we 

can trigonometrically convert this angular distance to a linear distance (B'-C) by using either the tangent or sine function of angle «. 

These two linear distances (B-Br ) and (B'-C) then constitute the 

components of the ship's horizontal movement during the velocity 

measurement interval.

In computing the correction to be applied to the observed velocity, 

the two components were converted to rates of movement, in feet per 

second. These values along with the observed river velocity were then 

plotted as shown in figure 4. The upstream-downstream component 

was either a positive or negative value depending on which direction 

the ship drifted during the current-meter count interval; whereas, the 

lateral component was always a negative value.

The application of corrections to the observed (measured) velocity 

reading is shown graphically in figure 4. (The graphical solution was 

found to be both simpler and less time consuming than the mathematical solution.) A vertical line of arbitrary length is drawn to 

represent the direction of the corrected river velocity. From an arbitrary point (B) on this line, the lateral component of the ship's rate

4

A

Right

bank

Shore location of

) / theodolite and 

'/ remote telluro1 meter unit

^ _____ rr-

\ Not drawn to scale

Direction of flow

Ship location 1

at beginning 

of current- Measuring

Left

bank

meter count ^^_g B' section^

 _____ \

C

r- Ship location at end of

current-meter count

FIGURE 3. iSketch showing typical drift pattern of ship during 40- to 50-second 

velocity-measurement period.
RIVER VELOCITIES MEASURED FROM UNANCHORED SHIP 113

FIGURE 4. Graphical application of corrections to observed 

velocity to obtain corrected velocity reading.

of movement during the velocity count period is shown as B-B'. The 

downstream component of the ship's rate of movement during the 

same period is shown by line B'-C. This component (B'-C} also is 

plotted as distance B-D on the vertical line drawn initially. From point 

67, the observed velocity measured by the current meter during the 40- 

to 50-second velocity measurement period is plotted as C-E\ this 

provides an intersection point (E) from which the corrected velocity 

(D-E) can be scaled off.
PATTERNS OF BACKWATER AND DISCHARGE ON 

SMALL ICE-AFFECTED STREAMS

By R. ELTON COOK and EDWIN E. CERNY

ABSTRACT

A temporary stream-gaging station was built on an ice-free reach to determine 

the winter discharge patterns on an ice-affected stream in northern New Mexico. 

Records from a nearby ice-affected gaging station were compared to records of 

the temporary station to determine the local daily backwater pattern. The 

methods used in the study can be applied to improve winter discharge records 

and the interpretation of winter records of gage height on ice-affected streams.

INTRODUCTION

The annual task of estimating winter mean daily discharges of 

small ice-affected streams from gage-height records, a few discharge 

measurements, and daily temperature and precipitation records can 

be both tedious and time consuming. Backwater caused by ice affects 

the gage height record so that discharges must be estimated.

Unfortunately, the effects of ice on small streams, such as height of 

backwater, change with geographic location, with altitude, with 

weather trends, from drainage basin to drainage basin, from stream 

to stream, and even from site to site on the same stream. This article 

outlines a new method of determining the effects of ice, and backwater 

caused by ice, on the gage heights recorded at particular sites on iceaffected streams. The geographic area in which the outlined method 

was devised and tested is the Southern Rocky Mountains in northern 

New Mexico.

STREAMS IN THE SOUTHERN ROCKY MOUNTAINS

Some basic information on conditions and streams is given below. 

This information is helpful in estimating winter mean daily discharges 

but falls short of what is needed to complete reasonably accurate winter 

discharge estimates without great expenditure of time.

Most winter days have several hours of sunshine. Ice and (or) snow 

melts on sunny afternoons, even on days when maximum air temperatures remain below freezing. The minimum daily temperature most 

114
BACKWATER AND DISCHARGE, ICE^AFFE,CTED STREAMS 115

often occurs around 0700 hours and the maximum between 1300 and 

1500 hours. The difference between minimum and maximum temperatures for most 24-hour periods is 30° to 40° F. Temperatures are relatively mild during storms but drop sharply afterward.

Small streams in the Southern Rocky Mountain area are generally 

shallow with steep gradients and high velocities. Anchor ice, the type 

that attaches on stream beds or on submerged objects, rarely forms. 

Shore ice forms first and builds toward the center of the stream. The 

thread of the stream freezes last. Typical ice cover is shown in figure 1.

Water overflowing the ice cover often causes layering. A stream may 

at times have as many as three layers of ice with some water flowing 

between layers. Recession of flow can withdraw vertical support and 

allow ice to slab off or slough into a stream (fig. 2).

A complete f reezeout, where all flow has gone into temporary storage 

as ice, is unusual.

Ice may form on streams in the area for short periods at any time 

from November through March. Ice on a stream causes backwater that 

increases and is generally greatest during morning hours; backwater 

decreases markedly near noon and on some days may be completely 

eliminated by ice breakup. Stream discharge is generally lowest in 

the early morning and highest in the early afternoon.

FIGURE 1. Typical ice storage on a small stream. The ice bridges the stream, 

but water has almost unobstructed flow underneath the ice. About 4 inches of 

snow cover is on top of the ice.
116 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196'6-67

FIGURE 2. Backwater and ice storage at permanent gaging station on the Rio 

Grande del Bancho. Part of bridged ice has sloughed into channel. Note open 

water in sunny reach upstream.

PLANNING AND PREPARATION

First, an attempt was made to analyze .winter stage and discharge 

patterns from gage-height records available for each gaging station 

in the Southern Rocky Mountains in northern New Mexico. The 

records for ice-affected periods disclosed some interesting patterns of 

backwater and discharge, and this information could be used but 

more specific data and some field verification were needed.

Therefore, it was decided to investigate ice-affected streamflow at 

seven stream-gaging stations in an exploratory program.

In the past, many attempts have been made to calculate backwater 

and discharge effects on ice-affected streams from a study of the causes. 

After considering the large number of causes, and the difficulty of 

evaluating the effects of each, it was decided that an empirical study 

of the effect of ice on streamflow might be a promising approach.

Next, a specific method of investigation had to be chosen that would
BACKWATER AND DISCHARGE, ICE-AFFECTED STREAMS 117

enable several questions to be answered clearly. It seemed to the authors 

that three important questions about ice-affected streamflow were:

1. Did backwater have a pattern of recurrence that could be related to 

other phenomena, such as weather?

2. Was the daily discharge pattern consistent enough to justify extrapolation of discharge from the gage-height recorder graph ?

3. Was the daily discharge pattern consistent enough so that a discharge measurement taken at any particular time of the day had 

a definable relation to the mean discharge for that day?

A direct method of answering the last two questions for any particular site would be to make 10 to 15 discharge measurements ,per day 

for 2 or 3 days and from these to construct a discharge hydrograph, 

which could, in turn, be related to the pattern of backwater from ice. 

We, and others before us, have used this very difficult method as the 

only feasible one at some sites.

Another, and less fatiguing method, which the authors used, is to 

construct a supplementary gaging station at a site selected for its relatively free-flow conditions near the original ice-affected station. A 

gage-height or discharge record collected at the supplementary site can 

be used to study the relation of actual discharge to backwater from 

ice at the regular gaging station.

GAGING STATION NEAR TALPA, NEW MEXICO, ON THE BIO 

GBANDE DEL RANCHO

Of the seven stream-gaging stations studied in the exploratory program, the station near Talpa, N. Mex., on the Rio Grande del Rancho 

(fig. 3) has been selected for individual discussion.

The Rio Grande del Rancho is a small, meandering, pool-riffle-pool 

stream with a drainage area of 83 square miles and a main reach above 

the gaging station 13 miles long. The average altitude of the drainage 

area is about 8,000 feet. The flood plain is narrow, though some 

meadows are flooded during normal high flows, and the terrain bordering the flood plain ranges from foothills and small valleys to relatively steep mountains. Ground cover is medium to heavy and consists 

of grass or forests of conifers and aspens. Areas of bare rock or barren 

soil are negligible. The main valley of the stream receives several hours 

of sunshine most days, but some sites are continually shaded because 

of local topography or vegetation. Annual precipitation averages 16 

inches. Winter precipitation, as snow, equals about 1 inch of water per 

month. Winter discharges of the Rio Grande del Rancho range from 

3 to 10 cfs (cubic feet per second) of clear water.
118 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196>6-67

FIGURE 3. Free-flow conditions at permanent gaging station on the Rio Grande 

del Rancho ; discharge about 5 cubic feet per second.

A reconnaissance was made to find a suitable site for an ice-free 

supplementary gaging station during a period of severe backwater 

conditions due to ice. An ice-free reach was found in an open meadow 

about 1,000 feet upstream from the permanent gage. The unobstructed 

channel at the new location consisted of a long, deep pool fully exposed 

to sunshine; there may have been some ground-water inflow at the head 

of the pool. This location seemed ideal for the supplementary gaging 

station, though it would have been unsuitable for a regular station 

because of overbank flows at medium and high stages.

In one working day two men installed a temporary supplemental 

gaging station consisting of a sharp-crested rectangular weir control, 

a continuous water-stage recorder, a recording thermograph, and a 

vented shelter to hold the recording equipment.

Current-meter measurements rated the weir at near the theoretical 

stage-discharge relation. Comparative measurements showed that 

discharges at the new gaging station and at the regular gaging station 

were equivalent and that discharge at the supplementary station could 

be substituted for discharge at the regular station. Frequent visits or 

inspections verified that the gage pool of the temporary station was 

usually free of ice and that the control weir was clear even when some 

ice did form on the pool. Figures 4 and 5 show the contrast between ice 

cover at the permanent and supplementary gages.
BACKWATER AND DISCHARGE, ICE^AFFECTED STREAMS 119

FIGURE 4. Complete ice cover and submerged control at permanent gage on 

the Rio Grande del Rancho. Overflow and partial thaw make ice appear as 

water in the photograph.

FIGURE 5. Free flow at supplementary gaging station while permanent gaging 

station was affected by ice.
120 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 1966-67 

ANALYSIS OF RECORDS COLLECTED

Fifty-three days of records were collected in the winter of 1959-60 

at the supplementary gaging station. Because of short incomplete or 

doubtful periods, only 39 days of record were used for analytical purposes. Statistically, 39 days of gage-height data supported by a known 

stage-discharge relation are far superior to the data that might have 

been collected during a 3-day series of current-meter measurements.

Gage heights for 3 days on which backwater from ice occurred at the 

regular gaging station are shown in figure 6. The fluctuations in gage 

height are not identical for the 3 days, but they are strikingly similar. 

The gage heights at the regular station that would have corresponded 

to the actual discharges were calculated from data collected at the 

supplementary gaging station.

Gage heights for another period of 3 days at the permanent gaging 

station are shown in figure 7. The gage-height fluctuations indicate 

that in the morning hours there was considerable backwater but that 

in the afternoon there was free flow under bridged ice (a condition 

verified by field inspection). Again, gage heights at the regular station 

that would have corresponded to actual discharges were calculated 

from data collected at the supplementary station. Note that the maximum discharge during a day may be as much as 400 percent of the 

minimum.

In the past it was believed, and often verified by measurements, that 

discharge measurements made in the morning gave results less than the 

daily mean discharge and that afternoon measurements gave results 

greater than the daily mean. Opinions differed as to what quantitative 

relation any given discharge measurement had to the daily mean 

discharge.

For the Rio Grande del Rancho near Talpa, the percentage of the 

daily mean discharge of discharge measurements made at any particular hour is shown in figure 8. This graph was derived from records obtained at the temporary gaging station; the relation of discharge at a 

particular hour to daily mean discharge would be different at another 

station on the same stream and different on another stream. For example, discharge on another small ice-affected stream less than 6 miles 

from the temporary gaging station had almost no daily pattern of 

fluctuation. Other stations studied had pronounced fluctuation patterns in daily discharge in which maximum flows occurred from 1300 

to 1500 hours. Such diverse discharge patterns emphasize the need of 

an individual curve for each station.

The hydrograph in figure 9 shows daily mean discharges, precipitation, and maximum, mean, and minimum daily temperatures for 27
3-0 I | | |

1200

Dec. 7, 1959

2400 1200

TIME, IN HOURS

Dec. 8, 1959

FIGURE 6. Pattern of backwater from ice at permanent station. 

obtained from data collected at supplementary gaging station

degrees Fahrenheit, are from the recording thermograph opera
122 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

133J Nl '1HDI3H 39V9
BACKWATER AND DISCHARGE, ICE-AFFECTED STREAMS 123

2.0

1.9

£ 1.

1.7

1 5 56 percent of daily mean discharge for discharge measurement made at particular hour o' day

0100 0600 1200 1800 2400

TIME, IN HOURS

FIGURE 8. Mean gage-height curve based on 39 days of winter gagQ-height 

records at temporary station. The percentage figures indicate the relation that 

a winter discharge measurement made at a particular hour would have to daily 

mean discharge.

|1 0.5

H z n

1 i i i i i i i i i i i

28 31 

January

10 15 

February

FIGURE 9. Hydrograph of mean daily discharge. Precipitation and maximum, mean, and minimum daily temperatures are also shown.
124 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

days in January and February 1960 at the temporary station on the 

Rio Grande del Rancho.

If the temporary gaging station had not been built, a synthetic hydrograph for the same 27 days could have been estimated for the original gaging station from two or three actual discharge measurements 

and a few daily discharges based on parts of the gage-height record 

corrected for backwater effect. A synthetic hydrograpl for an entire 

winter could have been estimated in a similar manner. Fortunately, 

periods of backwater are generally separated by periods of free flow 

caused by a succession of warm days; the periods of fre0, flow are used 

to correct and interpret the estimated periods of a hydrograph.

OBSERVATIONS

Many of the following observations about constructing gaging stations on ice-affected streams may be common knowledge, but emphasis 

on items previously recognized but given a minimum of attention may 

be useful.

In building either temporary or permanent gaging stations on iceaffected streams, an attempt should be made to place a station where it 

has maximum exposure to sunlight. Winter reconnaissance may reveal 

suitable sites that are relatively ice free.

Nonmetallic flumes are less apt to ice up than metallic ones. Nonmetallic stilling wells and float cylinders, where practical, are less 

conducive to deep freezing inside the gage well. Both gage well and 

float cylinder can be eliminated by using a bubble gage.

,An unobstructed, nonrestricted channel downstream from the gage 

control is highly desirable. On ice-affected streams controls are frequently submerged by ice forming on the control or by an ice jam creating a temporary dam downstream. Also, ice will form sooner and 

build up faster on wide, shallow, riffle controls than on those with more 

constriction through which water moves with higher velocities.

Sharp-crested, or blade, controls are probably the l*ast conducive 

to ice formation if adequate free fall is available. Free-flow Parshall 

flumes make good controls on ice-affected streams except that water 

inside the intake pipes may freeze because the pipe intakes are close 

to the water surface. Funnel, or self-cleaning, flumes may work well 

because they induce higher water velocities both in the approach to 

the control and over the control crest.

CONCLUSIONS

Lasting benefits may be derived from locating a temporary gaging 

station in a reach of stream that has been observed to be relatively free 

of ice during sustained cold weather. This study indicates that such
BACKWATER AND DISCHARGE, ICE-AFFEiCTED STREAMS 125

a station can be used, in conjunction with a nearby ice-affected station, 

to determine the local pattern of backwater from ice on the stream. A 

known backwater pattern for a permanent gaging station can te utilized in the annual analysis of winter streamflow records. Information gathered by the method of investigation used in this study makes 

it possible to reconstruct much of an ice-affected gage-height rword 

with fair confidence.

In addition, the daily discharge pattern ascertained from gageheight records at a temporary ice-free gaging station can be ur^d to 

relate discharge measurements made at a nearby permanent gaging 

station at any particular hour of the day to the daily mean discharge.

Finally, using the information obtained from an ice-free temporary 

station can save substantial time annually in interpreting the winter 

records of an ice-affected permanent station. Also, the results of interpreting records of an ice-affected station should be of improved 

quality.

312-670 O 68-
VARIABLE-SPEED POWER EQUIPMENT FOR DEPTHINTEGRATION SEDIMENT SAMPLING

By CLARENCE T. WELBORN and JOHN V. SKINNER

ABSTRACT

The power units used in collecting depth-integrated suspended-sediment 

samples must be capable of lowering and raising a sediment sampler at a constant speed and must operate over a range of speeds. Two different power units 

were built and tested in an attempt to develop an efficient method of controlling 

transit rates. Power equipment with a series-wound motor was developed by the 

U.S. Geological Survey and equipment with a shunt-wound motor was developed 

by the Federal Inter-Agency Sedimentation Project. Both unite proved successful ; they differ primarily in the type of motor used and in the general method 

of motor-speed control.

INTRODUCTION

Depth-integrated sediment samples are usually collected either by 

wading the stream and using a light-weight sediment sampler or by 

using 50- or 100-pound sediment samplers on a hand-operated crane 

and winch. The latter method, which is commonly used when sampling 

from bridges, boats, or cableways, becomes laborious.

To collect depth-integrated suspended-fluvial-sedim^nt samples, a 

depth-integrating sampler must be lowered to the bottom of the stream 

and raised again at a uniform rate, the sample being continuously 

collected throughout the stream depth. Tf the rate (sp°,ed) of transit 

is not too rapid, the pressure inside and outside the container will be 

balanced and the filling rate will be regulated by the stream velocity. 

It is important that the sampler be lowered and raised at a speed that 

does not exceed 0.4 of the stream velocity and that the rate of travel 

of the sampler be uniform; however, the rate of travel for lowering the 

sampler does not have to be the same as that for raisirg the sampler.

Certain basic requirements must be met by a power unit if the device 

is to be used at several different sites for collecting samples of suspended sediment. At any given site the unit must be capable of lowering and raising a sediment sampler at a constant speed. The unit must 

be capable of operating over a range of speeds because the allowable 

transit rate is determined by water depth and velocity, both of which 

126
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 127

may vary with time and location. For convenience the unit should be 

battery powered and electromechanically efficient.

Several different power units for use with suspended-sediment 

samplers have been developed and are being used. Most of the existing 

units utilize a series-wound motor, and the common method of speed 

control has been either series-connected rheostats or on-off switches. 

Each of these methods has certain disadantages. The series-rheostat 

method has a low efficiency because the entire motor current mus4". flow 

through the rheostat. The resulting heat generated by the rheostat 

represents wasted battery power, which must be replenished by frequent recharging. The on-off switch method has inherent poor speed 

regulation because the motor is either off or operating at full power. 

Intermediate speeds can be achieved by manually switching the motor 

on and off at a rapid rate, but this causes the sampler to move in a 

jerky fashion.

In an attempt to develop an efficient method for controlling transit 

rates, two different power units were built and tested. The two units 

differed primarily in the type of motor and in the general method of 

motor-speed control.

SEDIMENT SAMPLEBS USED WITH POWEB EQUIPMENT

Depth-integrated sediment samplers used with power equipment 

range in weight from 50 to 300 pounds. The light-weight samplers 

(depth-integrating), 50 and 62 pounds, are used only to collect sediment samples continuously throughout the stream depth; the heavier 

samplers (point-integrating), 100 to 300 pounds, can be used to collect 

sediment samples at any point beneath the surface of a stream. The 

heavier samplers also can be used to collect, depth-integrated samples.

These samplers have a cast bronze streamlined body in which a 

sample container (pint or quart milk bottle) is enclosed. The sample 

is collected through an intake nozzle that projects from the nose of 

the sampler into the stream; the rate of the sample intake can b? controlled by the size of the nozzle. Nozzles used have an inside diameter 

°f V^i %e? or Vs inch, and the nose of the sampler is drilled and tapped 

to accommodate any of these standard nozzles. An exhaust port on the 

side of the head of the sampler points downstream and permits air to 

escape from the bottle as it is displaced by the water-sediment sample. 

Tail vanes are an integral part of the sampler to orient the sampler 

nose upstream.

A depth-integrated sampler continuously accumulates a sample of 

the water-sediment mixture by moving vertically at a constant speed 

and by admitting the water-sediment mixture through the nozzle at a 

velocity equal to that of the stream. The 100-, 200-, and 300-pound
128 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 1966-67

samplers have electrically operated valves that alsc permit pointintegrated samples to be collected.

The samplers are raised and lowered by a sounding reel that is 

mounted on a crane or bridge rail. The power equipment used with the 

reel is discussed below.

POWER EQUIPMENT UNITS

SERIES-WOUND MOTOR

The standard power unit used by the U.S. Geological Survey is a 

24-volt series-wound direct-current aircraft starting motor that is 

normally operated by either a 6- or 12-volt storage battery. Whether 

powered by 6 or 12 volts the standard equipment has r o provision for 

varying the speed (other than by braking) of the sounding reel, which 

is a component of the standard equipment. Some mean? of varying the 

speed of the sounding reel is essential for proper deptl~ integration of 

a sediment sampler. For example, the transit rates ir water of 100- 

pound and 50-pound sediment samplers lifted by a sounding reel 

driven by the standard motor powered by a 12-volt battery are about 

4 fps (feet per second) and 6 fps, respectively. Both transit rates 

generally exceed the maximum rate permitted by the design of the 

sediment samplers used by the Geological Survey.

In trying to develop an efficient method of controlling transit rates, 

it was first suggested that a rheostat be used to control the voltage 

supply to the motor. However, a rheostat of the size necessary would be 

too bulky for the portable equipment used by the Ge^ogical Survey. 

The variable-speed power equipment that was finally designed and is 

now used by the Water Resources Division in Texas is shown in 

figure I A. The power equipment, which is mounted on a crane and 

dolly, can be adapted to field trucks as shown in figure IB. The nonstandard items in figure 1 include a heavy-duty multiple switch, two 

6-volt heavy-duty storage batteries, and the motor clutch.

The multiple switch (a in fig. 1) consists of two pieces of i/4-inch 

insulating board; six silver-alloy contacts and a control arm on the 

front of the multiple switch; and electrical connections to each contact 

and to the control arm at the back of the switch.

The power supply (b in fig. 1) is two 6-volt heavy-duty storage 

batteries. The batteries must be altered so that each cell of the batteries 

has a positive and negative connection. Then, when the batteries are 

connected in series, any voltage from 2 to 12 volts, in multiples of 2, 

can be delivered to the motor.

When 50- or 62-pound sediment samplers are used, a clutch must be 

on the motor to overcome the friction in the motor (c in fig. 1). Without the clutch these lighter weight sediment samplers could not be
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 129

FIGURE 1. Views of variable-speed power equipment with a series-wound motor: 

a, Multiple switch; &, storage batteries; and c, Grozier clutch. A, Arrangement 

of equipment. B, Adaption of equipment to field trucks.
130 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196<6-67

used with the variable-speed equipment discussed here. The motor 

clutch, which was designed by Kichard U. Grozier, Geological Survey, 

was made from parts of a standard centrifugal clutch as used on 

motorscooters. Additional information on the design of the motor 

clutch is available in the office of the U.S. Geological Survey, Water 

Kesources Division, Austin, Tex.

The motor is activated by a 12-volt solenoid, and 12 volts must be 

supplied to the solenoid at all times. By proper wiring and insulation 

of the solenoid from the vehicle, 12 volts can be delivered to the solenoid, and voltage from 2 to 12 volts can be supplied to the motor (fig. 

2). Four volts to the motor is about the minimum voltage that can be 

used with the sediment samplers. Changing the voltages to the motor 

by switching to the 4-, 6-, 8-, 10-, or 12-volt circuit will make the 

upward speed of a 100-pound sediment sampler in water range from 

0.5 fps to 4 fps. The speed of a 50- or 62-pound sampler will be a little 

faster. The downward speed of the sampler is controlled by the brake 

on the winch after the motor is disengaged from the power pulley by 

the action of the clutch.

Multiple switch

Motor control 

switch

FIGURE 2. Schematic wiring diagram for the variable-speed power equipment 

with a series-wound motor.
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 131

SHUNT-WOUND MOTOR

A shunt-wound motor differs from a series-wound motor with respect to the resistance and connection of the field winding and to the 

possible methods of speed control. The field resistance of the shuntwound motor is several hundred times greater than the resistance of 

the field winding of an equivalent horsepower series motor, and, as the 

name implies, a shunt-wound motor has the field connected in shunt (in 

parallel) with the armature.

The speed of a shunt-wound motor can be varied in two ways: one 

method is to connect the field to a constant voltage supply and vary the 

armature voltage; the other method is to connect the armature to a 

constant voltage supply and vary the field current. The field current is 

normally less than about 5 percent of the current supplied to the motor 

through its armature and field. Because the field current is small, a 

rheostat can be used to change the field current without lowering the 

overall motor efficiency by more than about 4 percent. This loss in efficiency is almost negligible in comparison with mechanical losses in 

speed-reduction equipment, such as belts and pulleys, which are present in any power-operated hoist.

In the experimental power unit that was constructed, both armature 

voltage and shunt field current variation were utilized as methods of 

speed control. As figure 3 indicates, the armature was connected 

through relay A contacts to either 12 volts or 24 volts. With the field 

current held constant, doubling the armature voltage caused the motor 

speed to double. The shunt field was connected through either rheostat 

Rd or Ru to 36 volts. Relay D was wired so that while the sampler was 

being lowered the shunt field current was supplied through Rd and 

while the sampler was being raised the field current was supplied 

through Ru. Both rheostat settings could be adjusted by the operator. 

With the two separate rheostats, the operator could adjust the raising 

and lowering speeds independently. The rheostats provided a continuously variable speed control over a speed ratio of 2:1. The combination of the two speed-control methods allowed the operator to adjust 

the transit rate of a 100-pound sampler to any value between 0.5 and 

2.0 fps.

Reversal of sampler traverse directions could be done either automatically or manually. Reversal of motor rotation was performed by 

the contacts of relay B, which changed the polarity of the applied 

armature voltage. For automatic reversal, relay B was activated 

through switches S3 , Ss, and SM- The automatic reversal signal originated with switch Ss, which was mounted near the tip of the crane. 

The switch was restrained by a spring-loaded pulley that was supported by the suspension cable. When the sediment sampler struck the
132 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 196'6-67

Indicating lamps

l u . up 

lp, power 

Id, down

Low speed, down* 

High speed, downDETAIL OF REMOTE CONTROL 

APPROXIMATELY 5" by 5" by 4"

Cam operated from tive position lever

Positions of switches Sj. S2, and Sj 

during various phases of operation

Switch

Si

S2

S 3

Phase

High 

speed 

down

Relaxed

Relaxed

Relaxed

Low 

speed 

down

Depressed

Relaxed

Relaxed

Brake

Depressed

Relaxed

Depressed

Low 

speed 

up

Depressed

Depressed

Relaxed

High 

speed 

up

Relaxed

Depressed

Relaxed

Relay (A-D) 

Coil Contacts

Switch (S)

Note: Arrows point to relay and switch 

contacts that are normally closed. 

Relay contacts are normally in deenergized position and switches are 

normally in relaxed position

FIGUEE 3. Schematic diagram showing wiring and operation of the variablespeed power equipment with a shunt-wound motor.

bottom of the stream, the suspension cable went slack, switch Ss closed, 

and current immediately flowed to the coil of relays B and D. While 

relay B contacts were reversing the armature voltage, relay D contacts 

were simultaneously performing the two functions of switching the 

field rheostats and bypassing switch Ss. The bypass contacts insured a 

continuous supply of power to relay B even after cable tension had 

been restored. For manual reversal the operator could open toggle 

switch SM- Power could then be supplied to relay B only through
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 133

switch S2 that was coupled to a manually operated five-position lever. 

The positions of switches Si, S2, and S3 in relation to the five positions 

of the manually operated control lever are shown on the cam chart in 

figure 3.

The power unit also was equipped with a circuit that enabled the 

shunt-wound motor to function as an electromagnetic brake. The operator could switch the control lever to the brake position and thus energize relay C through switch S3 . Relay C contacts performed the two 

functions of applying 36 volts to the shunt field and short-circuiting 

the motor armature. With the armature shorted and disconnected from 

a power supply, the motor functioned as a viscous damping device. 

The damping, when combined with the friction of the belting, was 

sufficient to hold a 100-pound sampler suspended. The brake function, 

when combined with the four lowering and raising functions, gave the 

operator complete sampler control with only one operating lever.

In its final form, the power equipment consisted of six major parts: 

remote-control unit, power-control unit, batteries, shunt-wound motor, 

automatic reversing switch, and speed-reduction equipment. (See table 

1 for an itemized list of parts.) The parts were mounted on a crane and 

the motor was mechanically coupled to a sounding reel as shown in 

figure 4. The mechanical coupling consisted of two stages of belting 

between the motor shaft and the power shaft of the reel. Overall speed 

reduction from motor shaft to reel drum was 40:1.

Some difficulty was encountered with arcing on relay B contact 

when automatic reversing was used. The almost instantaneous reversal 

of the motor rotation caused large surge currents of 90 to 100 amperes 

to pass through the relay contacts. It was found that manual reversal 

reduced the contact burning considerably but increased slightly the 

reversal time.

The complete crane and power equipment was transported to the 

U.S. Corps of Engineers office at Omaha, Nebr., for testing. At the 

testing site the automatic reversal was not used because samples were 

collected only while the sampler was moving from the streambed 

upward. Between battery charges, the Corps field personnel were able 

to collect 40 to 50 samples with a 100-sampler operating through a lift 

of about 100 feet. The testing team reported that operation was very 

favorable.

In general, the power unit met the requirements for use with suspended-sediment samplers. With a 100-pound sampler, speed regulation could be maintained within about 5 percent over the 0.5 to 2.0
134 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

Pulley coupled to switch Ss through 

spring-loaded plunger

Suspended-sediment 

sampler. 100 Ib or less

^Sounding reel

Mechanical -coupling 

belts and gears 

(refer to photograph) 

Power-control unit 

approximately 

8" by 10" by 4"

^Batteries

Multiconductor cable

'c'jfc-l- --"l£ 'Ir-Tr**; fl

FIGURE 4 (above and facing page). Views of variable-speed 

power equipment with a shunt-wound motor. A, Sketch of 

equipment; B, power equipment;
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 135

r?

C, reversing mechanism; and D, hoist details.
136 TECHNIQUES, WATER REiSOURCEiS INVESTIGATIONS, 1966-67 

TABLE 1. Components of variable-speed power equipment with shunt-wound motor 

Component Location Description Function

Batteries (three re- Rear of crane__..... 12 volts, 55 amperes......_ Power supply and counterquired) . weight. 

Fuse________.- Power-control unit-... 40 amperes. ____..__.. Motor protection. 

Indicating lamp:

Id_____.... Remote-control unit.. 24-36 volts, minature____ Indicates downward traverse. 

Iu __........... ....do__----------- .-..do__..__--.-__... Indicates upward traverse.

IP_...._..._ __do__..-------.. ....do_--.---._-.-.-.-.. Indicates control power on.

Motor_________ Frame of crane__ _ J£-horsepower 32-volt d-c, Prime mover.

shunt wound. 

Relay:

A. _. __. _ _ Power-control unit.... Single-pole double-throw, Coarse speed control.

heavy duty, 36-volt d-c Applies either 12 or 24 

coil, 25-ampere contacts. volts to motor armature.

B___...___ ._do__-___.__ Double-pole double-throw, Controls direction of motor

heavy duty, 36-volt d-c rotation, 

coil, 25-ampere contacts. 

C----------------- -...do_--.--------.. ....do_-----.-.-------._ Short motor armature for

electromagnetic brake 

action. 

D_---._...... ....do__-.-.-----.. Double-pole double-throw, Permits operator to adjust

light duty, 36-volt d-c up and down traverse 

coil, 5-ampere contacts. speeds independently.

Overrides automatic reversing switch S. after 

sampler reverses traverse 

at stream bottom.

Resistors, RL (three Remote-control unit.. Fixed carbon.. _ _. ____ Drops 36-volt supply to 

required). voltage level required by

indicating lamps. 

Switch:

Si_.-.-----.-.-. ....do__-.---.--... Singletpole double-throw, Switches power to coil of

light duty, snap action relay A. 

with roller leaf actuator, 

28-volt d-c, 10 amperes. 

S2 _--.-.__... __do_.__-.-_. ....do__..._____... Switches power to coil of

relays B and p. 

83_..._------- __do___---.-.-.. ..._do__..-------------.. Reverses direction of motor

rotation and simultaneously inserts appropriate 

Rd or Ru rheostat in field 

circuit; switches power to 

relay C to set motor run 

or brake mode. 

SE--.-_.__... Power-control unit.... Double-pole double-throw, Main power disconnect.

heavy duty, toggle, 250- 

volt a-c, 20 amperes. 

SF-.___....... Remote-control unit.. Single-pole single-throw, Remote power disconnect.

heavy duty, toggle, 250- 

volt a-c, 20 amperes.

SM____--.-.-. __do____.__ Single-pole double-throw, Switches control of motor

heavy duty, toggle, 120- reversal to switch Ss or to 

volt a-c, 5 amperes. manually operated fiveposition lever. 

Se---------------- Arm of crane. --..-. _ Single-pole double-throw, Automatically reverses

light duty, pushbutton, motor rotation when sus120-volt a-c, 5 amperes. pension cable is slack. 

Rheostat:

Rd__.-----._. Remote-control unit.. 25 watts, wire wound_._ Vernier speed control for

lowering samples. 

Ru ____.___ ....do__._...__ .._.do__________.... Vernier speed control for

raising samples.

fps range. This range of speed probably would be adequate to meet 

the requirements at most sampling sites. The overall efficiency, 

measured as the rate of change of sample potential energy divided by 

the power drain from the batteries, was about 40 percent. Roller 

chains and sprockets were later substituted for the V-belts and pulleys
EQUIPMENT FOR DEPTH-INTEGRATION SEDIMENT SAMPLING 137

shown in figure 4, and the efficiency was increased to about 50 percent. 

The motor functioned as a generator while the sampler was being 

lowered at high speed, and battery charging currents in excess of 5 

amperes were observed.

The shunt-wound motor power equipment was developed from wTork 

financed by the Federal Inter-Agency Sedimentation Project, 

Acknowledgment also is due B. C. Colby and T. F. Beckers, formerly 

assigned to the Federal Inter-Agency Sedimentation Project, both of 

whom assisted with the design and testing of the prototype.

COST

A cost comparison of the two power units is shown in the following 

tabulation:

Series-wound unit Shunt-wound unit

Materials: Materials:

Motor ______________ $170 Motor ______________ $175

Batteries __________ 60 Batteries __________- 45

Switch _____________ 65 Remote-control unit____ 40

Clutch _____________ 45 Power-control unit _ 50

 Mechanical coupling

Total _____________ 340 (V-belt) __________ 65

Labor ________________ 60 

 Total ____________ 375

Total ____________ 400 Labor ________________ 300

Total ____________ 675 

SUMMARY

The advantage of either the series-wound or the shunt-wound power 

equipment for sediment sampling is that the power equipment relieves 

the fieldman of much laborious work. Also the equipment enables the 

fieldman to control the transit rate better than by manual control.

A comparison of the series-wound and the shunt-wound power units 

reveals that the two units differ with respect to complexity, efficiency, 

maintenance, degree of control, and initial cost. The shunt-wound 

unit affords a greater degree of control and efficiency but at the expense of greater complexity, cost, and maintenance. The series-w^ound 

unit, because of the smaller number of parts, has a lower initial 

cost, is more rugged, and requires less maintenance.
ELECTRIC CONTROL SYSTEM FOR DUAL OPERATION 

OF CURRENT METER AND SUSPENDED-SEDIMENT 

SAMPLER

By HERBERT H. STEVENS, Jr., and ROBERT E. SOMMER, Jr.

ABSTRACT

An electric control system permits monitoring a current meter and operating 

a U.S. P-61 suspended-sediment sampler without surfacing the equipment. Use 

of this control system reduces the time required for observing velocity and sediment concentration in major streams.

Water discharge and sediment concentration of streams are usually 

determined by obtaining water velocity and stream depth with a current meter and sounding weight and by collecting suspended-sediment 

samples with a sampler. Dempster and Stevens (1965) described the 

use of a U.S. P-61 suspended-sediment sampler as a sounding weight 

for the current meter in place of the usual Columbus-type weight and 

described the meter-rating corrections that are required for this sampler suspension. This combination of current meter and sediment 

sampler expedites the collection of velocity and sediment data.

Since voltage requirements of the current meter and sediment 

sampler are very different, the electric circuits must be separated. 

Alternatives are sequential connection of the current meter and headphones or sediment sampler and sampler control switch to the available 

two-wire circuit, which requires raising the assembly from the water 

to the bridge level between observing velocities and sampling sediment; substitution of a three-wire circuit, which is an expensive operation; or the use of a system such as the diode-connected control 

described in this article. The electric control system as explained 

below permits sequential monitoring of the current meter and operation of the sediment sampler without surfacing the equipment.

The two parts of the electric control system are a selective control 

switch in a battery box that is mounted on the crane (fig. 1A) and a 

diode voltage-divider that is placed on the hanger bar between the 

current meter and sediment sampler (fig. 15). A schematic wiring 

diagram for the control system is shown in figure 2. The DPDT 

(double-pole double-throw) selective control switch changes voltage 

and reverses polarity in the inner wire of the suspension cable. When 

138
CURREINT METER AND SUSPENDED-SEDIMENT SAMPLER 139

FIGURE 1. Current-meter and sediment-sampler control system. A, Selective 

control switch and battery box; B, diode voltage-divider taped to hanger bar 

between Price current meter and U.S. P-61 suspended-sediment sampler.
140 TECHNIQUES, WATEiR RESOURCES INVESTIGATIONS, 1966-67

Battery box

Double-pole 

double-throw 

 ' switch

Headphones

Suspension-cable inner wire 

( + 48 volts or -l.SvoltsK

Reel terminals 

Suspension-cable sheath

Diodes-2 amp,200 volts 

(peak inverse voltage)

Rubber tubing,

silicone-rubber sealant

on both ends

$ Meter contacts

3 Sampler valve

solenoid

FIGURE 2. Schematic wiring diagram of electric system used 

as a control of Price current meter and U.S. P-61 suspendedsediment sampler.

the DPDT switch is in the meter position, a negative 1.5 volts is supplied to the inner wire through the headphone circuit; when the switch 

is in the sampler position, a positive 48 volts is supplied to the inner 

wire through the sampler control switch. The diode voltage-divider 

consists of two diodes, encased in a waterproof housing, that are connected in opposite polarity to the inner wire of the suspension cable. 

One of these diodes is connected to the meter and the other diode is 

connected to the sampler. The meter diode allows 1.5 volts to flow 

through the meter contacts while the sampler diode blocks the 1.5 

volts from the sampler solenoid. Conversely, the sampler diode allows 

48 volts to flow through the sampler solenoid while the meter diode 

blocks the 48 volts from the meter contacts.

The electric control system has provided reliable and trouble-free 

service during 2 years of field use. Use of the control shortens datacollection time and prolongs reel-motor battery life by reducing the
CURRENT METER AND SUSPENDED-SEDIMENT SAMPLER 141

number of times the equipment must be raised or lowered between the 

bridge and the stream.

REFERENCE CITED

Dempster, G. R., Jr., and Stevens, H. H., Jr., 1965, Concurrent collection of 

hydraulic and sediment data in rivers: Am. Water Works Assoc. Jour., v. 

57, no. 9, p. 1135-1138.

312-670 O 68 10
CHARACTERISTICS OF LOGARITHMIC RATI] T G CURVES

By S. E. RANTZ

ABSTRACT

An understanding of the shapes of logarithmic rating curves is requisite for 

analyzing the stage-discharge relation of a stream. The principles that govern 

the shapes of rating curves are demonstrated. As a general rule, linear logarithmic 

rating curves for section control have slopesi greater than 2; linear logarithmic 

curves for channel control have slopes less than 2.

INTRODUCTION

The rating curve, or stage-discharge relation, for a stream is usually 

plotted on logarithmic graph paper to simplify analysis of the characteristics of the stage-discharge relation. Analysis of the rating is perhaps of only academic interest where the entire range of stage of the 

rating curve is defined by discharge measurements. However, rating 

curves are often incompletely defined by measurements and must be 

extrapolated beyond the stage of the highest discharge measurement or 

must be interpolated between discharge measurements made at greatly 

differing stages. When rating curves are incompletely defined by 

measurements, a knowledge of the characteristics of logarithmic rating 

curves is needed so that extrapolation or interpolation can be performed on a rational basis.

STAGE-DISCHARGE CONTROLS

A prerequisite for any discussion of logarithmic rating curves is an 

understanding of the functioning of stage-discharge controls on 

streams. Two types of controls are section and channel. Section control 

exists when the geometry of a single cross section of a stream controls 

the relation between stage and discharge. Often the crops section that 

is the control for lower stages is not the control for higher stages. A 

cross section downstream may become effective at higher stages by 

causing backwater that submerges the original low-water control, or 

channel control may become effective at higher stages. Channel control 

exists when the geometry and roughness of a long reach of channel, 

142
CHARACTERISTICS OF LOGARITHMIC RATING CURVES 143

downstream from a gage, control the relation between stage and discharge. Channel control is generally effective at high stages; the 

most common exception is when the section control is a high dam or 

weir that does not become submerged at high flows.

A logarithmic rating curve is seldom a straight line or gentle curve 

for the entire range in stage at a site on a stream. Even if a single 

cross section of channel is the control for all stages, a sharp break in 

the contour of the cross section causes a break in the slope of the rating 

curve. Commonly, however, a break in slope of the rating curve is 

due to the low-water section control being submerged because a 

downstream section control or channel control becomes effective.

THEORY OF LOGARITHMIC RATING CURVES

The general equation of any straight line drawn on logarithmic 

graph paper is

Y=aXm , (1)

where Y= the dependent variable, 

X= the independent variable, 

a=the value of Y when X equals 1, 

and 7tt = the slope of the line.

If this same straight line is a rating curve, or a segmer t of a 

rating curve, its equation is

(2)

where Q=the discharge, in cubic feet per second,

.H=the head, or depth, of water on the control, in feet, 

p = the discharge when H equals 1 foot,

and 6= the slope of the line.

Because the dependent variable, Q, is conventionally plotted as 

the abscissa of the rating curve, slope, 6, is computed as the ratio of 

the horizontal projection of a segment of the curve to the 

vertical projection.

Commonly, the gage height of the water surface does not represent 

depth of water. For example, if the gage is set to sea-level datum, gage 

height obviously will not represent depth except in the special case 

where the elevation of the control is exactly at sea level. Therefore, to 

transform gage height of the water surface to head or depth of water 

(H in eq. 2), we must subtract the effective gage height of the control, or the gage height of effective zero flow, e, from the gage height 

of the water surface, G. For simple controls, e is the stage at. which 

discharge ceases. G and e are both measured in feet. By substitution of 

the gage-height terms for H in equation 2, we obtain the following
144 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

basic equation for a linear segment of a rating curve plotted on logarithmic graph paper:

Q = p(G-e)». (3)

Ordinate scales printed on logarithmic graph paper represent G e; 

however, ordinate scales can be transformed to gage readings of water 

surface by adding the value of e to each printed number.

Because the constants in equation 3 are related to the physical 

characteristics of the stage-discharge control, it is interesting to examine the effects of control changes on the rating curve. If the width 

of the control increases, p increases, and the new rating curve will be 

parallel to and to the right of the original curve. If the control scours, 

e decreases, and the depth for a given gage height increases; the new 

rating curve will move to the right and will no longer be a straight 

line but will be concave downward.

This change in shape of the logarithmic rating curve v^ith a change 

in the value of e is an example of a general rule that is illustrated in 

figure 1. All three curves in figure 1 represent the same rating. For 

example, when the gage height, 6r, is 4 feet, Q = 10 cfs (cubic feet 

per second; when the gage height, 6r, is 8 feet, $=90 cfs If too small 

a value of e is used, the curve is concave upward; if too large a value 

of e is used, the curve is concave downward. Consequently, if a curve 

is concave upward, it can be transformed to a tangent by increasing 

the value of e. If a curve is concave downward, it can be transformed 

to a tangent by decreasing the value of e.

20 30 50 70 100 200 300 500 700 

DISCHARGE (Q), IN CUBIC FEET PER SECOND

FIGURE 1. Rating-curve shapes resulting from the use of different values of 

effective zero flow, e. All curves represent the same rating. The true value of 

e is 2.
CHARACTERISTICS OF LOGARITHMIC RATING CURVES 145

An awareness of these principles of logarithmic curve plotting is 

necessary for an understanding of the shapes of logarithmic rating 

curves. The discussion that follows starts with explanations of rating 

curves for simple controls and progresses to explanations of rating 

curves for the more complex types.

SECTION CONTROLS OF REGULAR SHAPE

Thin-edged rectangular weir. For a thin-edged rectangular weir 

with negligible velocity of approach, the discharge equation (King 

and Brater, 1963, p. 5-11) is approximately

Q=3.3LH1 - 6 , (4) 

or

eY- 5 , (5)

where Z/=length of weir, in feet. If the gage height of the weir crest 

is used as the value of e in equation 5, the rating curve will be a straight 

line on logarithmic graph paper with p = 3.3L and 6=1.5.

Thin-edged triangular weir. For a thin-edged triangular weir with 

a central angle equal to 9 and a negligible velocity of approach, the 

discharge equation (King and Brater, 1963, p. 5-16) is

Q=2.5 tan H2 - 5 , (6)

or

Q=2.5 tan (G-e) 2 - 5 . (7)

&

If the gage height of the bottom of the weir notch is used as the 

value of e in equation 7, the logarithmic rating curve will be a straight

Q

line with p 2.5 tan - and 6=2.5.

^

Thin-edged trapezoidal weir. The discharge equation for a trapezoidal weir is dependent on the geometry of the weir and usually 

must be determined from discharge measurements. This type of weir 

has a shape between a rectangle and -a triangle, and, if the velocity of 

approach is negligible, the slope of the logarithmic rating curve will 

lie between the slope values for a rectangle and a triangle, or between 

1.5 and 2.5. The closer the shape is to a rectangle, the closer the slope 

will be to 1.5.

Broad-crested rectangular iveir. Sharp-crested weirs are seldom 

used as controls in natural streams. The simplest type of artificial con-
146 TECHNIQUES, WATER RESOURCE'S INVESTIGATIONS, 1966-67

trol used is a flat, broad-crested rectangular weir, whose basic discharge 

equation is

Q = GL(G-eY^ (8) 

where 6'~-s\, variable coefficient.

At the lower stages G varies with stage approximately according to the 

equation

<7=/i(£-e)°- 15 , (9)

where K=a coefficient.

By substituting the value of C from equation 9 into equation 8, the following equation is obtained:

Q = CP (G-e) , (10) 

where CP =KL.

In equation 10, Cp is used as a term to indicate a general constant that 

has the same function as p in equation 3. In later equations differently 

derived constants, if they serve the same function, will be labeled Cp.

Because the rate of change of velocity of approach increases with 

higher stages, the slope of the logarithmic rating curve for the control 

increases and the exponent of (6r e) also increases. If, as at most 

controls, width of the stream also increases with stage, the exponent of 

(6r e) becomes even greater and may exceed a value of 3. Therefore, 

the value of the exponent for the entire range of stage is considerably 

greater than 1.5, which at first thought might be considered the expected value for the slope of the rating curve.

Because the rating curve for an unsubmerged natural riffle has many 

of the characteristics of the rating curve for a broad-crested weir, the 

above remarks are applicable to the rating curve for a natural riffle.

Notched broad-crested control. Figure 2 shows a cro>s section of a 

notched broad-crested control and the rating curves for the gaging 

station. Because there is a sharp break in the cross section of the control 

at a gage height of 1.4 feet, a break occurs in the slope of the rating 

curve at that stage. For stages between 0.0 and 1.4 feet, th Q. gage height 

of zero flow is 0.0 feet; for stages above 1.4 feet, the gage height of effective zero flow is at some stage between 0.0 and 1.4 feet.

If the low end of the rating curve is made a tangent, the gage height 

of zero flow is 0.0 feet; and the slope of this tangent trrns out to be 

2.5, which is expectedly greater than the theoretical slope of 1.5 for a 

broad-crested weir. The upper part of this rating curve is concave upward because the value of e used (0.0 feet) is lower than tihe gage height 

of effective zero flow for high stages.

If the upper end of the rating is made a tangent, it is found that the 

AT alue of e, or effective zero flow, must be increased to 0.6 feet. Because
CHARACTERISTICS OF LOGARITHMIC RATING CURVEIS 147

Gage height 

= 1.4 feet

0.7

10 20 30 50 70 100 

DISCHARGE (Q), IN CUBIC FEET PER SECOND

200 300 500 700

FIGURE 2. Cross section of notched artificial broad-crested control at the gaging 

station on Great Trough Creek near Marklesburg, Pa., and rating curves for the 

station. Cross section not to scale.

the value of e is increased, the low-water end of the curve becomes concave downward. The high-water tangent of the curve, principally because of increased rate of change of velocity of approach, has a slope 

greater than the slope of the low-water tangent of the curve. The slope 

of the high-water tangent is found to be 3.0.

COMPOUND SECTION CONTROL

Figure 3 shows the rating curves for a compound section control 

and a profile of the control. The control consists of two rocl'-ledge 

riffles. Zero flow, e, for very low stages is at gage height 1.3 feet and 

for higher stages is at gage height 1.2 feet. If the low end of the rating 

curve is made a tangent, it means that too large a value of e is used for 

the high end of the rating curve 1.3 feet instead of 1.2 feet and the 

high-water end of the curve is concave downward. Conversely, if the 

high end of the curve is made a tangent, the low-water end of the 

curve is concave upward.

The high-water tangent of the one curve has a greater slope than 

the low-water tangent of the other curve. The differences in slope
148 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

reflect the differences in the geometries of the two controls as well 

as the effect of the increased rate of change of approach velocity at 

the higher stages. The slopes of the two tangents ar? 2.9 and 2.2. 

Both values are greater than the theoretical slope of 1.5 for a broadcrested control.

5 7 10 20 30 50 70 100 200 300 500 

DISCHARGE (Q), IN CUBIC FEET PER SECOND

FIGURE 3. Profile of compound section control at the gaging station on 

Muncy Creek near Sonestown, Pa., and rating curves for th? station. Profile 

not to scale.

CHANNEL CONTROL

Up to this point there has been little mention of rating curves for 

channel controls. The discharge equation for the condit: on of channel 

control is the familiar Manning equation (King and Brater, 1963,

p. 7-13),

where n=the Manning roughness coefficient,

A=ihe cross-sectional area, in square feet,

.R=the hydraulic radius, in feet, 

and «S'=the slope of the energy gradient.
CHARACTERISTICS OF LOGARITHMIC RATING CURVES 149

However, A is approximately equal to the depth of water in feet 

on the control, H, multiplied by width in feet, W; and the value of 

S at high stages frequently approaches a constant value. Therefore, 

equation 11 can be rewritten as followrs:

(12)

, n 1.486 M where Cl= £*. 

n

If W is considered a constant, as in a rectangular channel, and if R 

is considered equal to H, equation 12 becomes

Q=C9HIM, (13) 

where (7,= 0i W.

By substituting Q e for H, equivalent expressions, equation 13 

becomes

Q= Cp (G-eY-v. (14)

Compare equation 14 with equation 10 and with equation 3.

The assumption that R is equal to H, used in deriving equation 14, 

is valid only for an extremely wide stream. If the stream is not extremely wide, R, is smaller than H. For a deep narrow stream, R is 

much smaller than H. For most streams the difference between R and H 

lias the effect of reducing the exponent in equation 14. The exponent 

reduction may be offset, however, by an increase in 8 or W as discharge 

increases. Changes in roughness, n, with stage will also afect the 

value of the exponent. The net result of all these factors is that the 

channel control discharge equation can be put into the general form

Q=p(G-ey, (3)

where 5 = from 1.3 to 1.8 and rarely reaches a value as high as 2.0. 

Stage- discharge relations are shown in figure 4 for a gaging station 

with the common situation of a compound control section control 

at low stages and channel control at high stages. The low-water control 

is a low weir with gage height of effective zero flow, e, at 2.2 feet. At 

a stage of 3.9 feet the weir starts to "drown out," and channel control 

becomes effective. If the low end of the rating curve is made a tangent, 

a value for e of 2.2 feet must be used. Because the value of e for the 

upper end of the rating curve is something less than 2.2 feet, the high 

end becomes concave downward. If the high end of the curve is made 

a tangent, the value of e is found to be 0.0 feet, which is too low a value
150 TECHNIQUES, WATER RESOURCE'S INVESTIGATIONS, 1966-67

of e for the lower end of the curve. The low end becomes concave 

upward.

Where the rating for a section control (low end of the curve) is a 

tangent, the slope, 5, is expected to be greater than 2.0. In figure 4, 

b is 2.3. Where the rating for a channel control (high end of the curve) 

is a tangent, the value of b is expected to be less than 2.0 and probably 

between 1.3 and 1.8. In figure 4, b is 1.3 for the channel-control tangent. 

Should overbank flow occur at higher stages, the rating curve bends 

to the right to reflect an accelerated increase in discharge with stage.

3.2

2.7

3 5 7 10 20 30 50 70 100 200 300 

DISCHARGE (Q), IN THOUSANDS OF CUBIC FEET PER SECOND

500

FIGURE. 4. Rating curves for section control at low stages and channel control 

at high stages for a compound control at the gaging station on the Susquehanna River at Harrisburg, Pa.
CHARACTERISTICS OF LOGARITHMIC RATING CURV'EIS 151

A GENERAL NOTE ON THE SLOPE OF LOGARITHMIC RATING

CURVES

It can be demonstrated, nonrigorously, that logarithmic straightline rating curves for section controls almost always have slopes 

greater than 2 and that rating curves for channel controls generally 

have slopes less than 2. To illustrate this, first examine the equation

Q=pH", (2)

a general equation for a straight-line rating curve on logarithmic 

graph paper. If equation 2 is differentiated with respect to H, an 

equation is obtained for computing the change in discharge pev tenth

of a foot change in stage, or ^L which is usually obtained graphically. 

This first derivative obtained from equation 2 is

If we differentiate again, we obtain an equation for computing the 

change in -TV, per tenth of a foot change in stage, commonly referred

A.TZ

to as the second difference of the rating table. The second derivative 

of equation 2 is

*. (16)

Examination of equation 16 shows that the second difference increases 

with stage when 6, the slope of the straight-line rating curve, is 

greater than 2; the second difference decreases with stage when b 

is less than 2.

Now examine the rating shown in table 1 for a hypothetical stream 

having compound control. This rating table represents the common 

condition of section control at the lower stages and channel control 

at the higher stages. Where two values of discharge are shown for 

an item in the table, the figure in parentheses is exact and tl~ Q, other 

figure is the rounded value that normally would be used in r, rating 

table. Experienced hydrographers will recognize this rating ?.s being 

typical of ratings for the most streams. Inspection of the second difference column shows that the second differences increase as gage 

height increases at the low-water end (section control, 6>2) and decrease as gage height increases at the high-water end (channel control, 

6<2) . These are the results that one would predict from the preceding 

discussion.
152 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 19'66-67

TABLE 1. Hypothetical stage-discharge rating table

[If two figures are given under one heading, the figure in parentheses is exact and 

the other figure is the rounded value that would normally be used in a rating 

table]

Gage height, in feet Discharge, in cfs

1.0-._._ ___.-_-____ 100

!.!__ _________________ 120

1.2______.___. _________ 141

1.3_______. _____ _ _____ 163

1.4___.__. _____________ 187

1.5_______-____________ 213

1.6._ ------- ----- 242

1.7_____ --------------- 274

1.8____-------___-___._ 310

1.9_____-______ ______ 350 (349)

2.0 390

2.1_-__-____. ___--_____ 435 (433)

2.2______-___-____-____ 480 (478)

2 3 525

2.4. ___________________ 575 (573)

2.5 . ----- _ 625 (622)

2.6_____-----___-~--_- 675 (672)

2.7 _ ----- _ 725 (723)

Change in

discharge

per 0.1 ft

change in 

gage height

(A^)

20

21

22

24

26

29

32

36

40 (39)

40 (41)

45 (43)

45 (45)

45 (47)

50 (48)

50 (49)

50 (50)

50 (51)

50 (52)

Ch-jige in

AQ

Aff

per 0.1 ft 

change in

gage t eight '

1

1

2

2

3

3

4

3

2

2

2

2

1

1

1

1

1

1 Second difference.

REFERENCE CITED

King, H. W., and Brater, E. F., 1963, Handbook of hydraulics [5th ed.] 

New York, McGraw-Hill Book Co., Inc., p. 5-11, 5-16, and 7-13.
INTERPRETATION OF FLOOD-FREQUENCY DATA

By J. R. CEIPPEN and S. E. RANTZ

ABSTRACT

The conventional flood-frequency curve is an excellent tool for stud-ing the 

economics of planned flood-control measures, but the curve presents an incomplete picture of flood risk. That is, the flood-frequency curve shows the probability of an annual peak discharge being exceeded in any one year, but does not 

show the probability for a sequence of years. A family of curves is presented that 

overcomes the deficiency. These curves have universal use in studies of food risk 

because they are based on fundamental probability principles and are independent of both the flood data and the statistical distribution represented by the conventional flood-frequency curve.

Data on the peak discharges of flood events have been gathered from 

many sites over many years. These data are frequently studied in efforts to arrive at a more complete understanding of the hycfrologic 

and climatic phenomena that are involved. The data are also examined 

for more obvious and immediately practical purpose of planning construction features that must be related to the hydraulic characteristics 

of the streams during flood periods. For both purposes the flood data 

must be considered as a sample from a parent population whose characteristics are inferred by the statistical concepts of sampling theory 

and probability distribution.

When flood data are to be analyzed statistically, the assumptions, 

postulates, and hypotheses involved should not only be recognized but 

should also be specifically stated. Most analyses of flood data include 

the following assumptions:

1. The data studied consist either of annual flood peaks (on a wateryear basis) or of peaks above a predetermined magnitude (a partial-duration series).

2. The sample (that is, the data chosen) is a random sample from a 

parent distribution with characteristics that can be estimated by 

graphical or mathematical means.

3. Other samples (specifically, flood events during the period of future 

concern) will be from the same parent distribution and will 

occur within limits that can be defined by probability methods.

153
154 TECHNIQUES, WATE'R RESOURCES INVESTIGATIONS, 19'66-67

With regard to the first assumption, the probabilities or the recurrence intervals of all but the smaller flood peaks on a stream are usually 

almost identical whether determined from either the annual-flood series 

or the partial-duration series. Because of this similarity and because 

the annual-flood series is more easily manipulated statistically, annual 

floods are generally used in flood-frequency analysis.

As for the second assumption, several theoretical distributions for 

example, logarithmic normal, extreme value (Gumbel), Pearson type 

III, and gamma distributions are widely used in flood-frequency 

studies; other nonstandard distributions are derived from the flood 

data by graphical or semigraphical techniques. Whatever the distribution or technique used, the cumulative distribution of flood magnitudes 

at a site is the conventional flood-frequency curve, as illustrated in 

figure 1. The ordinate of any point on the curve is discharge; the corresponding abscissa is recurrence interval, or the average number of

3.0

2.5

Example: A discharge of 2,870 cfs 

 will be exceeded, as an annualpeak, at intervals averag: ng 100 

years in length I

7

2.0

1.5

1.0

0.5 1.1 1.5 35 10 20 

RECURRENCE INTERVAL, IN YEARS

50 100

FIGURE 1 Typical flood-frequency curve showing avearge numb?r of years between floods greater than the indicated magnitude.
INTERPRETATION OF FLOOD-FREQUENCY DATA 155

years between occurrences of an annual peak flow greater thr.n that 

discharge.

The third assumption concerning the distribution of future flood 

events in effect states that our only clue to flood experience in the future 

lies in our experience of the past.

The traditional wording related to the coordinates of the floodfrequency curve includes the phrase "discharge equal to or greater 

than * * *." Because the flood-frequency curve is a continuous function rather than discrete, the probability of a specific, precisely defined 

discharge is infinitesimal and the words "equal to" are therefore unnecessary and are not used in this paper.

The conventional flood-frequency curve is widely used to compute 

average annual flood damage in studying the economics of planned 

flood-control measures (Eckstein, 1958, p. 121-126; Maass and others, 

1962, p. 230-232). In these studies it is necessary to know the stage-discharge relation at the study site and the relation of monetary damage 

to stages. With this knowledge the frequency curve of flood peak discharge can be transformed to a frequency curve of monetary damage 

which, when integrated, gives the average annual flood damage. Figures of average annual damage are needed for computing cost-benefit 

ratios.

Although the conventional flood-frequency curve is an excellent 

and necessary tool for such economic studies, it presents an incomplete 

picture of the flood risk (Biggs, 1961, p. 21). If we compute the 

reciprocal of the recurrence interval of a given peak discharge, the 

flood-frequency curve gives us the probability of that discharge being 

exceeded in any year. It is equally important to know the probability 

of that discharge being exceeded during a sequence of years-. This 

probability can be computed on the basis of fundamental statistical 

principles that are independent of the distribution represented by 

the flood-frequency curve.

If the flood-frequency curve shows that a peak discharge of magnitude y has a recurrence interval of T years, then py=-Ff,, wher?, py is

the probability of an annual flood, y, being exceeded in any 1 year. 

The probability of y not being exceeded in any 1 year is therefore 

1 py, and the probability of y not being exceeded in a period of n 

years is (1 py) n . This logic is general and is independent of the 

nature of the flood-frequency graph. It follows then that the prob-
156 TECHNIQUES, WATER REiSOURCE'S INVESTIGATION TS, 19'66-67

ability, Py, of y being exceeded in a sequence of n years is computed 

by the equation

Py=\-(\-pyY (1)

or, substituting ^ for py,

(2)

For example, to determine the probability of a flood of 100-year 

recurrence interval being exceeded in the next 25 years, substitute 

into equation 2 as follows:

= 1-(0.99) 25 

= 1-0.778 

= 0.222.

The probability is 22 percent that the 100-year flood w'll be exceeded 

in any 25-year period (see fig. 2).

Similar computations can be made for various values of T and n, 

and the results are presented in the family of curves in figure 2. Used 

with figure 1 the curves indicate, for example, a 22-percent probability 

that a flood peak greater than 2,870 cfs (cubic feet per second) will 

occur during any 25-year period. Figure 2, a graphic presentation of a 

basic probability principle, has universal use in studies of flood risk 

because it is independent of both the flood data and the statistical distribution represented by flood-frequency curves.
INTERPRETATION OF FLOOD-FREQUENCY DATA 157

Example: During any 25-year pe-od there 

is a 22-percent probability that a flood of 

100-year recurrence interval will be exceeded

2 5 10 20 30 40 50 60 70 80 90 95 

PERCENT PROBABILITY OF OCCURRENCE OF A FLOOD GREATER THAN THAT HAVING THE IND'CATED 

RECURRENCE INTERVAL DURING PERIODS OF SELECTED LENGTH

FIGURE 2. Relation between recurrence internal and probability of exceedence during periods of selected length.

BEFEBENCES CITED

Eckstein, Otto, 1958, Water-resource development: Cambridge, Mass., Harvard

University Press, 300 p. 

Maass, Arthur, and others, 1962, Design of water-resource systems: Cambridge,

Mass., Harvard University Press, 604 p. 

Riggs, H. C., 1961, Frequency of natural events: Am. Soc. Civil Engineers Proc.,

Paper 2706, Hydraulics Div., Jour., v. 87, no. HY1, p. 15-26. 

312-670 O 68 11
AN OUTLINE OF GEOPHYSICAL LOGGING METHODS 

AND THEIR USES IN HYDROLOGIC STUDIES

By A. I. JOHNSON

ABSTRACT

Information on the depth, thickness, extent, and structure of an aquifer may 

be obtained for use of the hydrologist by judicious choice of the proper geophysical logging methods. To assist in making this choice, the various methods of 

borehole logging, the uses that may be made of each log, and the recommended 

borehole conditions are summarized. However, proper use of 1 orehole logs requires some knowledge of the geology of the area and considerable experience in 

log interpretation.

When the Schlumberger brothers made their first electrical survey 

of a borehole in France more than a quarter of a century ago, only 

one simple curve resistivity was recorded. The early equipment was 

very simple but signaled the beginning of a whole new industry that 

has provided many useful tools in the solution of hydrologic problems.

The hydrologist has the problem of selecting the logging methods 

most efficient, technically and economically, for answering his particular need. Information on aquifer depth, thickness, extent and structure, as well as details of permeability, porosity, moisture content, and 

the chemical quality of the contained water, are often ne°ded in hydrologic studies. Borehole geophysical logging methods now are available 

to provide the hydrologist with the data needed to give (through interpretation) all the above information, if the logging is properly 

supplemented by driller's logs, some knowledge of the local geology, 

and considerable experience in interpretation of the geophysical logs.

If funds are not to be wasted on unnecessary data, the logging 

methods must be chosen with due regard for the problem at hand. 

When there is doubt as to what type of log will give the information 

desired, logging experts in the hydrologist's organization or in the 

technical service centers of commercial logging companies should be 

consulted. In addition to a knowledge of the type of information desired from the logs, those logging experts probably wTould desire information on the following borehole conditions: depth, size, and condition 

or borehole; type of fluid in hole; classification and general thickness 

158
GEOPHYSICAL LOGGING METHODS IN HYDROLOGIC STUDIES 159

of formations; and quantity of fluid lost into formations. The technical 

consultation would be of even greater assistance if requested before 

drilling the boreholes.

It is the purpose of this paper to list various methods available for 

the geophysical logging of boreholes, and to briefly summarize the use 

that may be made of each log, as well as the specific borehole characteristics that provide conditions for optimum use of each method. The 

information was compiled from the references at the end of this paper 

and does not necessarily represent the opinions of the author. For more 

detailed information than that presented in table 1, the reader is referred to the references.

TABLE 1. Borehole geophysical logging methods

Method Uses Recommended conditions

Electric logging: 

Single-electrode 

resistance.

Short normal (electrode spacing of 

16 inches).

Long normal (electrode spacing of 

64 inches).

Deep lateral (electrode spacing 

approximately 

19 feet).

Limestone sonde 

(electrode spacing 

of 32 inches).

Determining depth and 

thickness of thin beds. 

Identification of rocks, 

provided general lithologic 

information is available, 

and correlation of formations. Determining casing 

depths.

Picking tops of resistive beds. 

Determining resistivity of 

the invaded zone. Estimating porosity of formations (deeply invaded and 

thick interval). Correlation 

and identification, provided general lithologic 

information is available.

Determining true resistivity 

in thick beds where mud 

invasion is not too deep. 

Obtaining data for calculation of formation-water 

resistivity.

Determining true resistivity 

where mud invasion is 

relatively deep. Locating 

thin beds.

Detecting permeable zones 

and determining porosity 

in hard rock. Determining 

formation factor in situ.

Fluid-filled hole. 

Fresh mud required. Ho1 ?- diameter less than 8 

to 10 inches. Log 

only in uncased 

holes.

Fluid-filled hole. 

Fresh mud. Ratio 

of mud resistivity 

to formationwater resistivity 

should be 0.2 to 4. 

Log only in uncased part of hole.

Fluid-filled hole. 

Ratio of mud 

resistivity to 

formation-water 

resistivity should 

be 0.2 to 4. Log 

only in uncased 

part of hole.

Fluid-filled uncased 

hole. Fresh mud. 

Formations should 

be of thickness 

different from 

electrode spacing 

and should be 

free of thir limestone beds.

Fluid-filled uncased 

hole. May be 

salty mud. 

Uniform hole 

size. Beds thicker 

than 5 feet.
160 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67 

TABLE 1. Borehole geophysical logging methods Continued

Method Uses Recorr mended conditions

Electric logging Con. 

Laterolog --____.

MicrologMicrolaterologSpontaneous potential.

Radiation logging: 

Gamma ray_ _

Investigating true resistivity 

of thin beds. Used in hard 

formations drilled with 

very salty muds. Correlation of formations, 

especially in hard-rock 

regions.

Determining permeable beds 

in hard or well-consolidated 

formations. Detailing beds 

in moderately consolidated 

formations. Correlation in 

hard-rock country. Determining formation factor 

in situ in soft or moderately 

consolidated formations. 

Detailing very thin beds.

Determining detailed resistivity of flushed formation 

at wall of hole when mudcake thickness is less than 

three-eighths inch in all 

formations. Determining 

formation factor and 

porosity. Correlation of 

very thin beds.

Helps delineate boundaries of 

many formations and the 

nature of these formations. 

Indicating approximate 

chemical quality of water. 

Indicate zones of water 

entry in borehole. Locating 

cased interval. Detecting 

and correlating permeable 

beds.

Differentiating shale, clay, 

and marl from other formations. Correlations of formations. Measurement of 

inherent radioactivity in 

formations. Checking formation depths and thicknesses with reference to 

casing collars before perforating casing. For shale 

differentiation when holes 

contain very salty mud. 

Radioactive tracer studies. 

Logging dry or cased holes. 

Locating cemented and 

cased intervals. Logging in 

oil-base muds. Locating 

radioactive ores. In combination with electric logs 

for locating coal or lignite 

beds.

Fluid-filled uncased 

hol^. Salty mud 

satisfactory. Mud 

invasion not too 

deep.

Fluid required in 

hol^. Log only in 

uncased part of 

hoK Bit-size hole 

(caved sections 

may be logged, 

presided hole 

enlargements are 

not too great).

Fluid-filled uncased 

hol^. Thin mud 

cake. Salty mud 

permitted.

Fluid-filled uncased 

hole. Fresh mud.

Fluid-filled or dry 

cas^d or uncased 

hol^. Should have 

appreciable contrast in radioactivity between 

adjacent formations.
GEOPHYSICAL LOGGING METHODS IN HYDROLOGIC STUDIES 161 

TABLE 1. Borehole geophysical logging methods Continued

Method Uses Recommended conditions

Radiation logging Con.

Neutron____________ Delineating formations and

correlation in dry or cased 

holes. Qualitative determination of shales, tight 

formations, and porous 

sections in cased wells. 

Determining porosity and 

water content of formations, especially those of 

low porosity. Distinguishing between water- or oilfilled and gas-filled reservoirs. Combining with 

gamma-ray log for better 

identification of lithology 

and correlation of formations. Indicating cased 

intervals. Logging in oilbase muds.

Induction logging________ Determining true resistivity,

particularly for thin beds 

(down to about 2 feet 

thick) in wells drilled 

with comparatively fresh 

mud. Determining resistivity of formations in dry 

holes. Logging in oil-base 

muds. Defining lithology 

and bed boundaries in hard 

formations. Detection of 

water-bearing beds.

Sonic logging___.________ Logging acoustic velocity for

seismic interpretation. 

Correlation and identification of lithology. Reliable indication of porosity 

in moderate to hard formations; in soft formations of high porosity it is 

more responsive to the 

nature rather than quantity of fluids contained in 

pores.

Temperature logging_ _ _ _ _ Locating approximate position of cement behind casing. Determining thermal 

gradient. Locating depth of 

lost circulation. Locating 

active gas flow. Used in 

checking depths and thickness of aquifers. Locating 

fissures and solution openings in open holes and leaks 

or perforated sections in 

cased holes. Reciprocalgradient temperature log 

may be more useful in correlation work.

Fluid-filled or dry 

cased or uncased 

hole. Formations 

relatively free from 

shaly material. 

Diameter less than 

6 inches for dry 

holes. Hole diameter similar 

throughout

Fluid-filled or dry 

uncased hole. 

Fluid should not 

be too salty.

Not affected materially by type of 

fluid, hole size, or 

mud invasion.

Cased or uncrsed 

hole. Can b? used 

in empty hole if 

logged at very 

slow speed, but 

fluid preferred in 

hole. Fluid should 

be undisturbed (no 

circulation) for 6 

to 12 hours minimum before logging; possibly 

several days may 

be required to 

reach thermal 

equilibrium.
162 TECHNIQUES, WATE'R RESOURCES INVESTIGATE NS, 1966-67 

TABLE 1. Borehole geophysical logging methods Continued

Method Uses Recommended conditions

Fluid-conductivity logging.

Fluid-velocity logging--__

Casing-collar locator.

Caliper (section gage) 

survey.

Locating point of entry of 

different quality water 

through leaks or perforations in casing or opening 

in rock hole. (Usually fluid 

resistivity is determined 

and must be converted to 

conductivity.) Determining 

quality of fluid in hole for 

improved interpretation of 

electric logs. Determining 

fresh-water-salt-water 

interface.

Locating zones of water entry 

into hole. Determining 

relative quantities of water 

flow into or out of these 

zones. Determine direction 

of flow up or down in sections of hole. Locating 

leaks in casing. Determine 

approximate permeability 

of lithologic sections penetrated by hole, or perforated section of casing.

Locating position of casing 

collars and shoes for depth 

control during perforating. 

Determining accurate depth 

references for use with 

other types of logs.

Determining hole or casing 

diameter. Indicates lithologic character of formations and coherency of 

rocks penetrated. Locating 

fractures, solution openings, and other cavities. 

Correlation of formations. 

Selection of zone to set a 

packer. Useful in quantitative interpretation of 

electric, temperature, and 

radiation logs. Used with 

fluid-velocity logs to determine quantities of flow. 

Determining diameter of 

underreamed section before 

placement of gravel pack. 

Determining diameter of 

hole for use in computing 

volume of cement to seal 

annular space. Evaluating 

the efficiency of explosive 

development of rock wells. 

Determining construction 

information on abandoned 

wells.

Fluid required in 

cased or uncased 

hole. Temperature 

lo;7 required for 

quantitative info~mation.

Fluid-filled cased or 

urcased hole. Injection, pumping, 

flcwing, or static 

(at surface) conditions. Flange or 

packer units required in large 

diameter holes. 

Caliper (section 

gage) logs required 

for quantitative 

interpretation.

Cased hole.

Fluid-filled or dry 

ca^ed or uncased 

hole. (In cased 

holes does not 

give information 

on beds behind 

casing.)
GEOPHYSICAL LOGGING METHODS IN HYDROLOGIC STUDIES 163 

TABLE 1. Borehole geophysical logging methods Continued

Method Uses Recommended conditions

Dipmeter survey.

Directional (inclinometer) survey.

Determining dip angle and 

dip direction (from magnetic north) in relation to 

well axis in the study of 

geologic structure. Correlation of formations.

Magnetic logging.

Locating points in a hole to 

determine deviation from 

the vertical. Determining 

true depth. Determining 

possible mechanical difficulty for casing installation or pump operation. 

Determining true dip and 

strike from dipmeter 

survey.

Determining magnetic field 

intensity in borehole and 

magnetic susceptibility of 

rocks surrounding hole. 

Studying lithology and 

correlation, especially in 

igneous rocks.

Fluid-filled uncased 

hole. Carefully 

picked zone? needing survey, because of expense 

and time reauired. 

Directional survey 

required for determination of true 

dip and stril'e 

(generally obtained 

simultaneously 

with dipmeter 

curves).

Fluid-filled or dry 

uncased hole.

Fluid-filled or dry 

uncased hole.

REFERENCES

Dakhnov, V. X., 1962, Geophysical well logging [translated from Russian edition, 

1959, by G. V. KELLER] : Colorado School Mines Quart., v. 57, no. 2, 445 p.

Doll, H. G., 1951, Induction logging and its application to logging of wells drilled 

witli oil-base mud, in LeRoy, L. W., ed., Subsurface geologic methods a 

symposium [2cl ed.] : Golden, Colo., Colorado School Mines, p. 393-398.

 1951. The niicrolog, in LeRoy, L. W., eel., Subsurface geologic methods 

a symposium [2cl eel.] : Golden, Colo., Colorado School Mines, p. 399 119. 

Gaskell. T. F., and Tlireadgold, P., 1960, Borehole surveying, in Runcorn, S. K.,

ed., Methods and techniques in geophysics: London, Interscience PuPisliers,

Ltd., v. 1, p. 62-103. 

Guyod, H. C., 1952, Electrical well logging fundamentals: Houston, Tex., Well

Inst. Developing Co., 104 p.

 1957, Electric detective investigation of groundwater supplies with electric well logs pt. 1: Water Well Jour., v. 11, no. 3, p. 12-13, 32, 35-36; 

Pt. 2, v. 11, no. 5, p. 14-15, 2&-34.

Jones, P. H., and Skibitzke, H. E., 1956, Subsurface geophysical methods in 

ground-water hydrology, in Landsberg, H. E., ed., Advances in geophysics: 

Xew York, Academic Press, v. 3, p. 241-300.
164 TECHNIQUES, WATER RESOURCES INVESTIGATIONS, 1966-67

Langton, Arthur, 1951, Well logging by drilling-mud and cutting analysis, in 

LeRoy, L. W., ed., Subsurface geologic methods a symposium [2d ed.] : 

Golden, Colo., Colorado School Mines, p. 449-455.

Mercier, V. J., 1951, Radioactivity well logging, in LeRoy, L. W., ed., Subsurface 

geologic methods a symposium [2d ed.] : Golden, Colo., Colorado School 

Mines, p. 419-439.

Tapper, Wilfred, 1951, Caliper and temperature logging, in LeRoy, L. W., ed., 

Subsurface geologic methods a symposium [2d ed.] : Golcler. Colo., Colorado 

School Mines, p. 439-449.

Schlumberger Well Surveying Corporation, 1958, Introduction to Schlumberger 

well logging: Houston, Tex., Schlumberger Well Surveying Corp., Schlumberger Doc. 8, 176 p.

Stratton, E. F., and Lord, R. D., 1951, Electric logging, in LeRoy, L. W., ed., Subsurface geologic methods a symposium [2d ed.] : Golden, Colo., Colorado 

School Mines, p. 364-392.

U.S. GOVERNMENT PRINTING OFFICE: 1968 O 312-670