Amazon River Investigations 

Reconnaissance Measurements 

of July 1963

GEOLOGICAL SURVEY 

CIRCULAR 486

Prepared in cooperation with the University of Brazil and the Brazilian Navy
Amazon River Investigations 

Reconnaissance Measurements 

of July 1963

By R. E. Oilman, H. O'R. Sternberg (University of Brazil), 

F. C. Ames, and L. C. Davis, Jr.

GEOLOGICAL SURVEY CIRCULAR 486

Prepared in cooperation winS the University of 

Brazil and the Brazilian Navy

Washington 7964
United States Department of the Interior

STEWART L UDALL, Secretary

Geological Survey

William T. Pecora, Director

First printing 1964 

Second printing 1967

Free on application to Jfie U.S. Geological Survey, Washington, O.C. 20242
CONTENTS

Page Page

Abstract. ___________________________ 1 Results of discharge measurements __ 4

Introduction_________________________ 1 Procedures for observing quality ____ 9

Acknowledgments_________________ __ 2 Results of water-quality observations. 10

Procedures for measuring discharge___ 3 References.-----___-________-__--_ 15

ILLUSTRATIONS

Page 

Figure 1. Map showing the reach in which observations were made______________________ 5

2. Map showing location of measuring sections in vicinity of Manaus______________ 5

3. Cross sections and mean velocity in verticals at measuring sites __-___-_-_-___ 7

4. Daily river stages at Manaus for the period 1903 52 by decades, and for

the year 1953 __________________________________________________________ 8

TABLES

Page

Table 1. Summary of measurements of the Amazon River and tributaries------__________ "6

2. Variation of velocity in vertical_____________________________._______________ 6

3. Water-quality observations, Amazon River, Brazil____________________________ .11

III
Amazon River Investigations 

Reconnaissance Measurements of July 1963

By R. E. Oltman, H. O'R. Sternberg,1 F. C. Ames 

and L. C. Davis, Jr.

ABSTRACT

The first measurements of the flow of the Amazon River 

were made in July 1963 as a joint project of the University of 

Brazil, the Brazilian Navy, and the U.S. Geological Survey. 

The discharge of the Amazon River at Obidos was 7,640,000 

cfs at an annual flood stage somewhat lower than the average. 

For comparison the maximum known discharge of the Mississippi River at Vicksburg is about 2,300,000 cfs. Dissolvedsolids concentrations and sediment loads of the Amazon 

River and of several major tributaries were found to be low.

INTRODUCTION

The discharge of water, solutes, and suspended sediment of the Amazon River (Rio 

Amazonas)to the Atlantic Ocean is estimated 

to be a significant part of the total discharge 

from all the continents to the oceans. Parde 

(1956, p. 14) reviewed several estimates of 

the Amazon flow at Obidos and concluded that 

"the mean ought to exceed 90,000 cubic meters 

per second(3,178,000 cfs) and possibly 100,000 

cubic meters per second (3,531,000 cfs)."

The average annual runoff from the continents to the oceans has been estimated by 

Durum and others (1960) to be about 40 million cfs (cubic feet per second). Thus at Obidos, 

the estimated average discharge of the Amazon 

River, which at that point drains an area of 

1,945,000 2 square miles in contrast to the 

2,368,0002 square miles it drains at its mouth, 

is about 9 percent of the estimated average 

continental discharge into the oceans. Assuming equal yield from all parts of the basin, the 

average discharge of the Amazon at its mouth 

might be as much as 11 percent of the average 

world runoff to the oceans.

In 1957, the International Association of 

Scientific Hydrology (IASH) adopted a program

1 University of Brazil.

2 From Encyclopedia Britannica, 1960.

of computation of the riverborne dissolved 

solids carried to the oceans. The studies 

carried out under that program showed that 

the lack of data for discharge and dissolved 

solids of the Amazon River seriously hampered the precision of results. In May 1961, 

Luna B. Leopold, chief hydrologist of the U.S. 

Geological Survey, Walter B. Langbein, staff 

scientist of the U.S. Geological Survey, and 

Prof. H. O'R. Sternberg, Director, Centre de 

Pesquisas de Geografia do Brazil, University 

of Brazil (Rio de Janeiro), jointly proposed a 

plan for measuring the flow, solute load, and 

sediment concentration of the Amazon River 

so that greater refinement in the worldwide 

analysis of flow and dissolved solids could be 

attained. In June 1963 arrangements were 

completed for an Amazon reconnaissance 

gaging to be conducted as a joint project of 

the Centre de Pesquisas de Geografia do 

Brazil, University of Brazil; the U.S. Geological Survey; and the Diretoria de Hidrografia 

e Navegacao of the Brazilian Navy.

The lower Amazon is little affected by 

short-period flood events, but has a smooth 

annual cycle of changing flow. It rises slowly 

for about 8 months from a minimum in late 

October or early November to a maximum in 

June and falls in about 4 months to the next 

low.

The channel width ranges from about 1 mile 

in some of the narrower reaches to 2 or 3 

miles for long stretches, and up to 5 or 6 

miles in some places. The depth ranges from 

20 to 40 feet in the north and south channels 

near the mouth, to more than 300 feet in some 

of the narrower, reaches at least as far upstream as the Rio Madeira. In spite of the 

tremendous size of the channel, the annual 

high flow inundates much of the flood plain to
AMAZON RIVER INVESTIGATIONS, RECONNAISSANCE MEASUREMENTS OF JULY 1963

depths ranging from a few inches to several 

feet.

The flood plain is generally very flat and 

ranges in width from a few hundred feet to 

many miles. The lower levels of this flood 

plain are perpetually wet and swampy and 

contain many large, shallow lakes. These 

lakes rise and fall with the river through 

mazes of small streams and distributary 

channels known as furos and paranas. These 

lakes and channels store enough water to 

have a substantial dampening influence on 

discharge fluctuations and a stabilizing influence on water quality.

The lower parts of several large tributaries 

to the lower Amazon, notably the Rio Negro, 

Rio Tapajos and Rio Xingu, are virtually lakes 

in what appear to be submerged valleys rather 

than true river channels. The actual mouths 

of these streams are only a mile or so wide, 

but the water-surface widths above the mouths 

range from 5 to 10 miles for distances of 50 

to 100 miles. These "lakes" also exert major 

stabilizing influences on fluctuations of runoff 

and water quality.

The reconnaissance investigations provided 

for measurement of water discharge, sediment 

concentrations, and dissolved-solids concentrations at two locations on the Amazon 

Obidos and Manaus. Obidos was a logical selection because stage observations were made 

there from 1928 to 1947 and because it is at 

or near the upstream limit of tidal effect.

The waters of the Amazon fork and rejoin 

enclosing long strings of alluvial islands, 

which split the stream into a master channel 

and one or several side channels known as 

paranas. In the vicinity of Manaus, one such 

channel is the Parana* do Careiro, which diverges from the main stream just above the 

mouth of the Rio Negro and rejoins the main 

stream about 25 miles downvalley. It has 

been suggested that the Amazon is tending to 

preempt the bed of the Careiro, increasing 

the caliber of this channel while progressively 

abandoning its present course to the north 

(Moraes, 1926).

The dilation in cross section that the channel of the Careiro would have to undergo in 

order to carry the entire flow of the Amazon, 

if this event were ever to occur, would be at 

the expense of the densely settled strip of

land fronting on or contiguous to the Careiro. 

The problem has been considered by Sternberg (1956), but the lack of any information 

regarding streamflow and the distribution of 

sediment load in the area of study prevented 

a solution.

Arrangements were accordingly made to 

measure the flow and to collect material for 

sediment concentration studies in the ManausCareiro area under more favorable conditions than those under which Sternberg(1956, 

p. 48) obtained some 20 concentration figures 

with the use of improved equipment in 1948 

and 1950, in the "black, "sediment-poorwaters 

of the Negro and the "white" silt-bearing 

waters of the Amazon and the Careiro.

In July 1963 the first measurements were 

made at high flow of discharge, dissolvedsolids concentrations, and sediment loads. 

Because of the worldwide interest in the 

Amazon the results of the first measurements 

are being made available in this report before 

the second (low-flow) series of measurements, 

started in October 1963, are analyzed. A complete analysis of the results of the reconnaissance program will be reported later.

The essential information collected during 

July 1963 and comments helpful in understanding the methods of data collection are 

presented in sections following "Acknowledgments." The section "Procedures for measuring discharge" contains a description of the 

general methods and the detailed procedure 

followed. A similar section, "Procedures for 

observing water quality," is provided. Results 

of discharge measurements and water-quality 

observations are given in separate sections.

ACKNOWLEDGMENTS

The Amazon measurements could not have 

been made without the cooperation of the 

Brazilian Navy. The key role of Vice Adm. 

Helio Gamier Sampaio, Diretoria de Hidrografia e Navegacao, Ministerio da Marinha, 

in arranging for the use of the corvette 

Mearim and the assignment of Lt. Comdr. 

Almir Dantas (an expert hydrographer and 

English-Portugese interpreter) to the project 

is gratefully acknowledged. Dr. Fernando 

Andrade,Profe88orSternberg's assistant, arranged important conferences with several 

Brazilian government officials who furnished 

information on gage locations, gage records,
PROCEDURES FOR MEASURING DISCHARGE

and charts of the Manaus region. Doctor 

Carvalho, Vice President of the Conselho 

Nacional Pesquisos, was most helpful in furnishing advice about Amazon River conditions 

based on personal knowledge gained from 12 

earlier expeditions to the Manaus region. 

Alfred Bodenlos, chief of the U.S. Geological 

Survey party in Brazil (U.S. AID Mission), 

was instrumental in arranging many contacts 

with key Brazilian officials and in getting 

needed scientific .materials. The Office of 

Naval Research, U.S. Navy, furnished transportation on Military Air Transport Service 

from Charleston, N.C., to Rio de Janiero and 

return for the four-man Geological Survey 

gaging team. The officers and men of the 

corvette Mearim under the command of Lt. 

Comdr. Milton Carvalho are commended for 

the extremely efficient handling of the ship 

during the tedious stream observations. Walter Langbein of the U.S. Geological Survey 

was a key man in initial negotiations to start 

the project and in seeing that it was consummated.

PROCEDURES FOR MEASURING DISCHARGE

Measurement of discharge followed the 

standard procedures in use by the Geological 

Survey in the domestic program. Point-velocity observations were made with a Price AA 

current meter suspended forward of the ship's 

oowfrom an 1/8-inch diameter two-conductor 

cable and located 1 foot above the bottom of a 

streamlined 300-pound lead sounding weight. 

A calibrated electric-powered winch of 2^-foot 

drum circumference was used to raise and 

lower the meter for soundings and for meter 

settings. Angular departure of the cable 

from vertical was measured by an indicator 

applied to the suspension cable at the pulley 

located at the outboard end of the horizontal - 

winch support. The vertical-angle observations were used to calculate the true sounded 

depth, which was compared with depths recorded by the ship's fathometer or a portable 

fathometer.

Distance from the initial point on right or 

left bank was measured with tellurometer 

equipment under the direct supervision of G. 

R. Staeffler, U.S. Geological Survey. The 

master tellurompter was set up on the foredeck of the corvette immediately astern of 

the sounding winch. The remote tellurometer 

was set on the most favorable bank at the end 

of the cross section chosen for observations. 

An auxiliary tellurometer circuit permitted

communication between operators of the 

master and remote tellurometers. A theodolite placed next to the remote tellurometer 

was used to measure any upstream or downstream movement of the ship during velocity 

observations in case the ship could not be 

held exactly on the cross section. The theodolite operator relayed angle observations 

to the note keeper aboard ship through a twoway portable voice radio. A portable fathometer recorded soundings during the measurement to supplement those taken by the ship's 

fathometer, and by the cable-weight suspension.

The step-by-step procedure in measurement of discharge was as follows:

1. The best cross section available in a 

long reach of river adjacent to the gage site 

was selected on the basis of combined uniformity of section bed profile and alinement 

of surface velocities normal to the section. 

The ship's fathometer was used for sounding 

the many cross sections considered.

2. Remote tellurometer and theodolite were 

set on the most favorable bank at the end of 

the chosen cross section.

3. The ship was brought to the desired location of first vertical on cross section by 

using required rudder and propeller settings. 

The ship's gyrocompass with auxiliary sighting telescope was used to place the ship on 

section.

4. When the ship had stabilized on section 

at first vertical, tellurometer reading of distance from remote instrument was taken and 

observations of any lateral movement from 

first vertical were continued while sounding 

and metering velocities jln vertical.

5. Soundings were taken with the meterweight suspension and checked with portable 

fathometer.

6. If vertical angle of the sounding line was 

significant, it was used to correct the sounding taken with meter-weight suspension.

7. Meter was set at 80 percent of water 

depth from water surface.

8. At given signal, counting of meter revolutions, theodolite observation of upstream or 

downstream movement of meter suspension,
AMAZON RIVER INVESTIGATIONS. RECONNAISSANCE MEASUREMENTS OF JULY 1963

and tellurometer observations of the lateral 

position of ship parallel to cross section 

were started.

9. Meter revolutions were counted for 

more than 40 seconds.

10. At signal from meter-revolutions 

counter, observations of upstream-downstream and lateral movements were stopped 

at exact end of velocity observation.

11. Meter was raised to 20 percent of 

depth and theodolite-tellurometer observations were repeated during observation of 

velocity at that point.

12. Ship proceeded to second vertical on 

cross section and the tellurometer observer 

furnished the approximate distance of lateral 

movement.

13. The types of measurements made at 

the first vertical were repeated at second 

vertical.

14. Process was continued until entire 

cross section was traversed, during the 

course of which, measurements were made 

at 20 to 24 verticals.

15. Observed velocity at each point in 

cross section was adjusted by vector analysis for the movement of ship during observation.

16. Discharge measurement was computed.

RESULTS OF DISCHARGE MEASUREMENTS

Figure 1 shows the general location of the 

measuring sections nearObidos and Manaus. 

Figure 2 is a large scale map .showing the 

locations of the Manaus gage and the measuring sections in the vicinity of Manaus. For 

the measurements on the Rio Negro and the 

Parana do Careiro, a Brazilian Army launch 

was used in place of the corvette Mearim, 

which could not easily be held on station 

owing to the prevailing velocity of flow. A 

small channel, the Parana do Autaz-Miri, 

which carries an insignificant part of the 

total flow of the Rio Solimoes, was not measured because of difficulty of access. Results

of all discharge measurements are summarized in table 1.

The soundings and mean measured velocity 

in the vertical at sounding locations for each 

measurement are plotted in figure 3. The 

detailed variation of velocity with depth was 

measured near the middle of the Obidos 

cross section and at two verticals in the 

cross section of the Amazon near Manaus. 

Of those two verticals, one (Sta. 4740) is 

representative of the Rio Solimoes water, and 

the other (Sta. 1810) of the Rio Negro water. 

The observed data are listed in table 2. 

Point velocities were observed for 40 to 50 

seconds. The effect of pulsatioris is noticeable in the scatter of velocities about any 

curve one may try fitting to the data.

The July 1963 measurement of the Amazon 

near Manaus (A) was made at stage 26.46 

meters on the staff gage on the Rio Negro in 

Manaus. Because the slope of water surface 

of the Amazon is so small (a total fall of 65 

meters in the 3,000 kilometers from the 

Peruvian border to the sea has been reported 

by Scares in 1956), the water stage observed 

at the Manaus gage is valid for the Amazon 

River below the junction of the Rio Negro 

and the "Rio Solimoes. How does the stage of 

26.46 meters compare with the 1963 crest 

and other annual crests? The 1963 crest 

stage of 27.31 meters occurred June 17 to 19. 

Average-stage hydrographs by decades for 

the period 1903 52 in comparison with the 

stage hydrograph of the outstanding flood 

year of 1953 are shown in figure 4 for the 

Manaus gage. The great regularity of seasonal flows is readily apparent. In the period 

1902-53, the highest annual stage, 29.70 

meters, occurred June 6,1953 and the lowest 

annual flood stage, 21.77 meters, occurred 

July 5-7, 1926. The 1963 crest of 27.31 

meters is seen by reference to figure 4 to be 

nearly equal to the average maximum stage 

(27.4 meters) for the period 1903-52.

Comparison of the Obidos measured discharge with pertinent data for the Mississippi 

at Vicksburg, Miss., the most downstream 

gaging station on North America's -largest 

river, indicates the relative magnitude of the 

Amazon River flow.
60'

RESULTS OF DISCHARGE MEASUREMENTS

56- » 52 . 48"

Figure 1. Map showing the reach in which observations were made.

5 KILOMETERS

EXPLANATION

Direction of flow 

A

Location of discharge 

measurement section

r

MANAUS 

(Staff gage located 

about 300 feet 

upstream from g 

\ floating dock)

Figure 2. Map snowing locatton of measuring sections in vicinity of Manaus.
AMAZON RIVER INVESTIGATIONS, RECONNAISSANCE MEASUREMENTS OF JULY 1963 

Table 1. Summary of measurements of the Amazon River and tributaries

Stream

Amazon River 

Do........

Parana do 

Careiro. 

Rio Negro. __ 

Rio Solimoes 

Amazon River 

Rio Solimoes

Location 

(Letter designates 

location on fig. 2)

Near Obidos.....

Near Manaus (A) _ . 

(D)__

(B)__ 

(C)__ 

Below Manaus (A+D) 

Near Manaus (C+D)

Date

1963

July 16 

20 

22

22 

23

StageMm)

5.8 

26.46 

26.35

26.34 

26.29

Section properties

Width 

(ft)

7,500 

6,880 

2,240

7,730 

5,920

Area 

(lO^t2 )

1,184 

922 

160

890

746

Mean 

velocity 

(fps)

6.45 

5.72 

4.43

2.65 

3.98

Discharge (cfs) 

Measured

7,640,000 

5,260,000 

710,000

2,360,000 

2,970,000

Total

5,970,000 

3,680,000

1Obidos gage destroyed in 1953. Stage recovered approximately from levels based on gage 

datum scaled from photograph of original gage against background of building still in place in 

July 1963. Manaus gage readings used for Amazon, Negro, Solimoes, and Parana do Careiro 

measurements. The Manaus gage is tied in with an arbitarary bench mark = 100.000 m, set in 

the steps of the Municipal Prefecture; gage readings are usually referred to sea level, on the 

basis of a mark on the steps leading to the Parish Church (Matriz), which is assumed to lie at an 

altitude of 35.874 m, according to observations made many years ago under the direction of 

Samuel Pereira, an engineer in charge of the Manaus Sanitation Comm. Whereas such an altitude cannot by any means be considered to be a precise 4atum point, observations may be provisionally referred"to it.

Table 2. Variation of velocity in vertical

Obidos

Depth of 

observation 

(ft)

2

17

35

52

71

87

104

117

133

. 150

160

Bottom at 171

Velocity 

(fps)

7.44

7.53

7.62

7.62

7.28

7.62

fc.97

7.28

5.96

6.07

3.74

Manaus 

(Sta. 1810)

Depth of 

observation 

(ft)

3

14

29

43

57

71

81

93

106

119

133

Bottom at 147

Velocity 

(fps)

7.18

7.17

7.35

7.02

7.68

7.21

7.19

6.55

6.52

6.92

6.18

Manaus 

(Sta. 4740)

Depth of 

observation 

(ft)

3

20

41

62

83

101

121

142

158

179

194

Bottom at 198

Velocity 

(fps)

7.41

7.36

6.26

6.16

6.39

7.53

6.97

5.64

5.35

6.20

4.32
ui Oi 01 01

O O O o O O O

| II 1

ro ro ro

6 bo bo o 

o oo o oo o oo

.r* «-» L

CO

n

I

1

a velocity ia

R

8

^^

_o

o

ro

_o

£ 0

2

* (D

(D

CO

!*

 *

* 

ro 

o

8

f

4k 

_O 

O 

O

C

- c 

c.

c 

o> =

0 * ~ O

o

00 

0

0

 n

(D

(D

F5"

/ T»

\ OQ

°S

i fl> 3

;\ T°v

:S °?

 JJJiiim^.

^

1

2

(D 

Q

< m 

< X

1 '

0 o r

> 2. >

; ? z 

L - >

r » ±

' * o

-. z

^

I i

/

f'

5»

/ o

/ w

/ o

/ li

/ 

.' o

/ f

1 °

V ' C

\ m

i

V - .

1 1

o 1 c%

Q

1 1 1

 01 o 

o

FEET PER SECOND

1 1

\7

.-^^'

/

/

S i

\

\

\

/

\ Tl

\ o

i z

\ -2

/ 

\ 

i

\

01 

O O 

II 

 ro 

O o o 

0 00 0 

i i

^?

 *'

3>

3

Q

N 

O

3

<* 5 

(D

"1

y °

/ <:

\ " /

\ ° )

1 1

1 °

vx -:-

\ ' 

i ""i

i

I it i

OJ O

Q

Ns^

"""^s*^

1 1

1 

/

/ . 

/

i ,,--'' 

\ \

\ i

u 

/ I 

1 ' 

1 

N 

\ 

i 

\ 

/ ' 

-v 

\ \

"*

' 

METERSPCR SECOND
AMAZON RIVER INVESTIGATIONS. RECONNAISSANCE MEASUREMENTS OF JULY 1963

I I I I I I I I I I I I I I I I I I

2 : | x 

< -ro 110 10 to 10 O - tM - ' -

>. 

I 

£

1 

I

I

£

04

 ?

Sd313W Nl '1H9I3H 39V9
PROCEDURES FOR OBSERVING WATER QUALITY

Mississippi River at Vicksborg, Miss. 

Drainage area........................ 1,144,500 sq mi

Max. known discharge (approx) 2,300,000 cfs...May 1927

and date. 

Avg. discharge (33 yr)............. 560,200 cfs

Amazon River at Obidos

Drainage area........................ 1,945,000 sq mi

Measured discharge and date..... 7,600,000 cfs.. July 16, 1963

Probable max. discharge 10,000,000 cfs..1953 

(approx) and year.

PROCEDURES FOR OBSERVING WATER QUALITY

Water-quality data were obtained to supply 

reconnaissance-type information on: (1) The 

magnitude of dissolved solids and suspendedsediment concentrations and loads carried 

by the lower Amazon; (2) variations in these 

factors along the river; and (3) possible thermal or salinity stratification.

Data were obtained in the 700 -mile reach 

of river from the junction of the Rio Negro 

with the Rio Solimoes (Amazon River) near 

Manaus to long 52° W., where the river divides into two main outlet channels; along 

the south channel to the Ilha Maritiapina, 

thence along a series of "estreitos" (inlets) 

to the Rio Para, and along that river to 

Belem. Observations were made from the 

Brazilian corvette Meartm as the ship traveled 

upstream July 10 18 and downstream July 

26 29. Samples for field observations were 

taken at or near the water surface at intervals along the main channel, in the mouths 

of the Rio Tapajos and Rio Madeira, and at 

various depths at the cross sections where 

discharge measurements were made near 

Obidos and near Manaus. Samples for detailed chemical analyses were taken at or 

near the surface at the measuring sections 

near Obidos and near Manaus and in the 

mouths of the Rio Tapajos and Rio Madeira. 

Suspended-sediment samples were taken at 

several depths at the measuring cross sections, and bed-material samples were taken 

at the same sections.

The chemical-quality samples at the surface were taken in an open container suspended near the bow of the ship. Most of 

these samples were collected while the ship 

was moving at speeds of 5 to 13 knots. The 

chemical-quality samples at depth were taken 

in an oceanographic sampler consisting of an 

open tube allowing through flow of water until 

closed at the desired depth by sponge rubber, 

ball-type valves. Suspended-sediment samples were taken in 1 pint containers in a U.S.

P-61 suspended-sediment sampler with a 

3/16-inch diameter nozzle. This sampler is 

the point-integrating type, with an electrically 

operated valve opened only at the desired 

depth and held open only long enough to collect 300 to 400 cubic centimeters of sample. 

Bed-material samples were taken with an 

oceanographic clamshell type bottom sampler. Temperature-depth profiles were obtained with a bathythermograph.

All the devices for obtaining data at depth 

were suspended from the bow of the ship with 

the same cable and reel equipment used for 

the discharge measurements.

The field observations included direct 

readings of temperature, specific conductance, and pH, plus titrations for alkalinity 

and dissolved oxygen. These observations 

are tabulated along with companion observations of air temperatures and altimeter 

readings.

Water temperatures were measured with a 

mercury thermometer graduated in degrees 

Fahrenheit, and (or) from the trace produced 

on a glass slide in the bathythermograph. 

Specific conductance was read on a portable 

conductivity meter with a manual temperature compensator and a platinum elect rodeconductivity cell having a constant of 0.10. 

Readings of pH were made on a portable pH 

meter (Beckman Model N) with standard electrodes. Frequent checks were made using 

standard buffer solutions at pH 7.0 and pH 

4.0. Titrations to determine alkalinity and 

dissolved oxygen were performed according 

to standard methods used by the Geological 

Survey (described in Water-Supply Paper 

1454).

Laboratory analyses of samples, to be conducted in the future, will include determination of concentrations of the common major 

dissolved constituents, the presence and concentration of several minor elements, and of 

gross radioactivity; in addition, radium and 

uranium contents will be determined, if possible. Suspended-sediment samples will be 

analysed for sediment concentration. The 

concentrations of suspended sediment that 

have already been obtained were less than 

anticipated, and it was not feasible to concentrate or to ship the large volumes of 

sample that would have been required to 

provide sufficient sediment for analyses of
10 AMAZON RIVER INVESTIGATIONS, RECONNAISSANCE MEASUREMENTS OF JULY 1963

particle-size distributions and mineralogy. 

None of the samples have arrived at the 

laboratory as of this writing (October 1963); 

results of analyses will be included in a 

subsequent report.

RESULTS OF WATER-QUALITY OBSERVATIONS

Various reports on the Amazon indicate 

that the exposed rocks of the headwater areas 

are quite resistant to chemical weathering, 

and that the soils of the high-rainfall areas 

have been almost completely leached of 

readily soluble minerals. As a result, a low 

dissolved-solids concentration is to be expected at all discharges. This was found to 

be true from the high-flow observations made 

during July 1963. The specific conductance 

(in micromhos per centimeter) ranged from 

52.8 at the mouth of the Rio Solimoes to only 

9 in the Rio Negro at Manaus. (See table 3.)

The waters of the two streams flow side by 

side for many miles in the common channel 

below the junction, and mix very slowly. At 

the high discharge observed in July, the Rio 

Negro water was virtually sediment free but 

was colored almost black by organic material, whereas the Rio Solimoes water was 

quite turbid and gray brown or yellow brown 

in color. Thus, the degree of mixing at the 

surface was readily discernible. A distinct 

though irregular and fluctuating interface 

between the two waters persisted for at least 

12 miles below the junction. For several 

miles beyond this reach, the surface of the 

intermingling had a mottled appearance, and 

the sizes of the patches decreased rapidly 

downstream. Where mixing was fairly well 

advanced, the turbidity had a curdled or stippled appearance, indicating some reaction 

between the two waters and some flocculation 

of the fine sediments. Specific conductance 

and pH readings indicate that mixing was not 

entirely uniform for at least 70 miles below 

the junction.

In the absence of chemical or ion-exchange 

reactions between two dissimilar streams, 

the proportionality of specific conductance in 

each stream to specific conductance of a uniform mixture of the two would be the same 

i as the proportionality of discharge. For the 

Rio Negro-Rio Solimoes, the proportions 

based on conductivity would be 9N + 52,S = 

40(N+S) or 72 percent SolimSes water and 28 

percent Negro water. Discharge measurements showed that the actual proportions

were 3.0 and 2.4 to 5.3, or 57 percent Solimoes 

and 43 percent Negro water. This lack of 

agreement substantiates the visual evidence 

of some reaction between the two waters.

Some reaction is expectable in view of the 

differences in pH. The pH of the Solinioes 

water was about 6.6, of the Negro about 5.0, 

and of the mixture about 6.4. The higher 

acidity of the Negro water is buffered to 

some extent by the Solimoes water and also 

causes some desorption, or possibly some 

solution, of the sediment in the Solimoes.

The Rio Madeira was passed in the night 

on both the upriver and downriver trip, 

making it impossible to observe comparative 

color or turbidity. However, specific conductance and pHwere somewhat higher in the 

Rio Madeira just above its mouth than in the 

Amazon River above and below (52 and 6.9 

compared with 40 and 6.4). Differences in 

specific conductance of the Amazon above 

and below the Madeira were no greater than 

the general range of variation from point to 

point, making it impossible to evaluate probable flow of the Madeira.

Observations in and below the Rio Tapajos 

may indicate an appreciable flow in that 

stream. The Rio Tapajos was virtually clear; 

the color was the characteristic deep blue of 

clear fresh water. A secki disc was visible 

to a depth of 20 feet. A zone of clear water 

was visible along the south side of the Amazon for 5 or 6 miles below the mouth of the 

Tapaj6s, and incomplete mixing was evident 

for several more miles. Temperature of the 

Rio Tapajos on the afternoon of July 13 was 

about 4°F higher than that of the Amazon; the 

difference was due to solar heating on the 

large lake above the mouth.

The pH (7.15) of the Tapajos water was 

slightly above neutral and the pH (about 6.5) 

of the Amazon water from both above and below the Tapajos was slightly below neutral. 

On the basis of this evidence, little reaction 

would be expected between the two waters. 

The specific conductance of the Tapajos 

water was 15.0; that of the Amazon water 

from above and below the Tapajos was 40.5 

and 39.5. This difference is too small to 

permit placing much reliance on a computation of discharge in the Tapajos, but taken at 

face value it indicates a discharge equal to 4 

or 5 percent of the Amazon, or 0.3 or 0.4 

million cfs on the basis of 7.6 million cfs
RESULTS OF WATER-QUALITY OBSERVATIONS 11

Table 3. Water-quality observations, Amazon River, Brazil

Day 

(July 

1963)

Time

Location

Lat S. Long W.

Water

Temperature 

(«F)

Specific 

conduct - 

ance 

(micro - 

mhos at 

25°C

pH

Bicar - 

bonate 

(ppm)

Dissolved 

oxygen 

(ppm)

Air

Temperature 

(°F)

Dry 

bulb

Wet 

bulb

Relative 

humidity 

[percent)

Altimeter 

reading1 

(ft)

Baia de Guajara

10__ 1000

1 14^

1004.1

i°r>Qi

Aftoqrj!

AQoqni

84 0

85.5

<?3 81

83

1,010

1,020

Rio Para

10_-

11

1 99(\

1 <?9fi

1450

1630

1 o^n

0600

1 °noi

1°23'

1°36'

1°46'

1°50'

1°50'

Aftoq4l

48°43'

49° 07'

49° 36'

50° 09'

50° 09'

86.0

85.0

86.0

85.5

85.0

83.0

38

37

35.0

35.0

35.0

7 0

6.7

84

84

85

8fi 5

78 0

76

76

76.5

77.5

70

66

64

98

1,022

1,045

1,070

1,090

1,070

1,020

Estraito de Boiucu

11-- 0800 1°47' 50°28' 83.0 37.0 6.65 78.0 75.5 89 1,020

Furo do Tajapuru

a..

11-.

1100 

1140

!°n'. 50°49' 

50° 51'

1300

11-. 

12_.

1430 

1600 

2200 

0600

1°02' 51°03'

83.0 

83.0

38.0 

37.5

6.70 84.0 75.0 66 1,000 

1,000

Furo do Ituquara

83.5 37.8 6.55 t 1,020

Amazon River (south channel)

1«29'

51°27' 

51°55'

83.0 

84.0 

82.5 

82.5

37.0 ' 

37.2

39.0

6.6t) 

6.60 87

76.0

75

75.0

58

95

1,045 

1,070

Amazon River

1 9

1 ^

0800

1000

1200

1700

0600

0800

1000

1200

1230

1°26'

1°34'

1°35'

1 04,01

1°59'

2

01 C|

2°25'

2°28'

2°25'

eoorkfii -

52°24'

52°42'

53°27'

2coocci

CLAOflQI

54°18'

54°38'

t\A°A9i

82.5

82.8

83.0

83.0

82.0

82.2

82.5

83.0

^Q n

39.5

39.5

39.5

39.8

39.8

39.5

35.5

28.5

6.40

6.45

6.50

6.50

6.55

6.50

6.55

77,0

80 5

82 0

84

77,0

82 0

84

75.5

76.0

76.0

76.5

75.0

74.0

76

93

82

76

71

91

68

69

1,000

970

982

1,060

1,005

990

1,008
12 AMAZON RIVER INVESTIGATIONS, RECONNAISSANCE MEASUREMENTS OF JULY 1963

Table 3. Water-quality observations, Amazon River, Brazil Continued

Day 

(July 

1963)

Time

Location

Lat S. Long W.

Water

Temperature 

(°F)

Specific 

conduct - 

ance 

(micro - 

mhos at 

25°C

pH

Bicarbonate 

(ppm)

Dissolved 

oxygen 

(ppm)

Air

Temperature 

(°F)

Dry 

bulb

Wet 

bulb

Relative 

humidity 

(percent)

Altimeter 

reading1 

(ft)

Rio Tapajos

1 ?

14__

1300

1300

2000

0600

oooci

2°25'

2°25'

oooci

3^404 ci

454°45'

54°43'

^4.°4^i

86.0

86.0

86.0

85.0

15.0

17.0

15.0

15.0

6.90

7.10

7.15

7.15

7.7 81 0 73.0 68

1,020

1,020

1,050

1,045

Amazon River

14__ 

15. _

17__ 

18__

0800 

1000 

1200 

1400 

0600 

1300

1700 

1330 

1930 

0600 

1200 

1215

2°21' 

2°09' 

2°07' 

1°58' 

1°54' 

1°55' 

(Measu 

cross 

Sta. 7 

68 ft. 

At 3 

At 6 

Sta. 4 

175 ft 

At 1 

At 5 

Sta. 2 

155 ft 

At 1 

At 5 

2°35' 

2° 50' 

3°21' 

3°04' 

3°04'

54044 ,

54° 54' 

55°15' 

55°23' 

655°32' 

55°31' 

rement 

section.) 

,400 depth,

-ft depth 

5 -ft depth 

,000,depth,

3 -ft depth 

3 -ft depth 

,000,depth,

3 -ft depth 

0-ft depth 

2 57°17' 

2 58°00' 

2 58°48' 

7 59°45' 

8 59°46'

82.0 

82.+ 

82.+ 

82.5 

82.0

83.0 

83.0

83.0 

83.0

83.0 

83.0 

82.0 

82.0 

82.0 

82.5 

82.0

40.5 

40.2 

40.5 

5 37.5 

37.0

37.5 

39.5

37.5 

38.5

37.5 

39.0 

42.5 

45.0 

35.5 

13.5 

51.5

6.45 

6.50 

6.45 

6.60 

6.52

6.55 

6.55

6.55 

6.55 

6.4 

6.34 

6.40 

5.60 

6.37

14.1

16.0

17.0 

18.4

17.3 

18.2 

15.6

. 7.0 

5.6

6.0 

5.5

6.0 

5.8

5.8 

5.8 

6.0

79

82 

83.5 

73.5

82 

77.2 

81.5

75

75 

76.0 

71.5

76 

73.8 

76.0

82

72 

71 

90

76 

85 

78

1,040 

1,020 

1,030 

1,070 

1,070

1,060 

1,070 

1,060 

1,060

Rio Negro

18_. 

20.-

1430 

1330

3°09' 

3°09'

960°01' 

60°01'

83.0 

83,0

9.0 

9.5

4.95 

4.9 5.5

1,130

Amazon River

20-. 1630 3°08' 59° 54'

(Measurement

.cross section.)

Sta. 4, 800, depth,

194 ft. 

At 10 -ft depth 

At 100-ftdeoth

83.5 

83.0

52.5 

52.5

6.55 

6.60

24.0 

24.7

5.3 

5.8
RESULTS OF WATER-QUALITY OBSERVATIONS 13

Table 3. Water-quality observations, Amazon River, Brazil Continued

Day 

(July 

1963)

Time

Location

Lat S. Long W.

Water

Temperature 

<°F)

Specific 

conduct - 

ance 

(micro - 

mhos at 

25°C

PH

Bicarbonate 

(ppm)

Dissolved 

oxygen 

(ppm)

Air

Temperature 

(°F)

Dry 

bulb

Wet 

bulb

Relative 

humidity 

(percent)

Altimeter 

reading1 

(ft)

Amazon River Continued

20__ 1630 

1700

Sta. 1,700, 

depth, 148 ft. 

At 10 -ft depth 

At 70 -ft depth 

At 140-ft depth

83.5 

83.0 

83.0

10.0 

9.0 

9.0

5.10 

5.12

5.2 

5.8 

6.2

Parana do Careiro

22.. 1200 3°13' 59°50' 

(Measurement 

cross section; 

center of channel, depth, 80 ft.) 

At 10 -ft depth 

At 60 -ft depth 

At 7 7 -ft depth

83.0 

84.0. 

84.0

50.2 

50.2 

50.2

6.65 

6.65 

6.65

Rio Solimoes

23__ 1630 3°11' 59°54' 

(Measurement 

cross section.) 

Sta. 4, 000, 

depth, 150 ft. 

At 10 -ft depth 

At 50 -ft depth

83.0 

83.2

52.8 

52.8

6.70 

6.65

26.5 6.0 

6.0

Rio Negro

26_. 1520 

1550

3°09' 

3°10'

26_. 1610 

1630 

1700 

1815 

1930

2°08' 

3°04' 

3°06' 

3°14' 

3°16'

26.. 2030 3°24'

96o°or

59° 56'

83.0 

83.0

9.0 

9.0

4.80 

5.00

5.4 

5.4

Amazon River

10 59° 54' 

n59°47' 

59°38' 

59°17' 

58° 58'

83.0 

83 

82.5 

82.2 

82.2

12.0 

38.0 

21.0 

52.0 

39.5

5.50 

6.20 

L26.00 

6.50 

6.35

\ 

Rio Madeira

58°46' 84.0 52.0 6.9 21.0 7.5
14 AMAZON RIVER INVESTIGATIONS, RECONNAISSANCE MEASUREMENTS OF JULY 1964

Table 3. Water-quality observations, Amazon River, Brazil Continued

Day 

(July 

1963)

Time

Location

Lat S. Long W.

Water

Temperature 

<°F)

Specific 

conductance 

(micro - 

mhos at 

25°C

pH

Bicarbonate 

(ppm)

Dissolved 

oxygen 

(ppm)

Air

Temperature 

(°F)

Dry 

bulb

Wet 

bulb

Relative 

humidity 

(percent)

Altimeter 

reading1 

(ft)

Amazon River

26..

27_.

OQ

9Q

2200

0745

0845

OQ9O

1200

1430

1700

1845 

0600

1700

0700

3°15'

2°40'

2

00CI

2

004.1

2

0QC 1

2°14'

1°58'

1°58 

i o^fti

1°47'

101 0|

CQoq^i t

57°41'

«i 7oqqi

£709 ci

^fioti1 i

56°16'

55°45'

55°23«

cco9qi

cqof\7i

^1°91 >

82.2

82.8

go n

83.0

po A

83.0

83.0

83.0 

82.5

83.5

83.0

38.0

42.5

4.9 9

40.0

°.Q ft

39.5

39.5

37.5 

9.7 n

38.0

37.5

6.40

6.35

6.40

6.35

6.35 

6.25

H K

15.0

i K n

12.3

5 A

5.4

5.5

5.4

5.7 

6.1

77 3

7Q n

84.0

R5 5

R4 5

80.0

7?,

R4 8

75.8

75.5

73.0

75.0 

71

77.5

93

63

58

79 

96

72

990

1,000

1,050

1,085

1,080

1,060

Furo do Tajapuru

9Q 1200 IOOQI KQ007I 84.5 9Q n R6.0 73.5 55

1 1,000 ft = 0 at mean sea level at standard pressure.

Approximate.

3Depth » 82 ft. Sampled at surface.

4Depth = 82 ft. Sampled at 10-ft depth.

5May be affected by flow from Rio Trombetas.

6At Obidos..

7Mostly Rio Negro water, black or Coca-Cola color.

8Mostly Rio Solimoes water, turbid, yellow brown.

9At Manaus.

10At measurement cross section. Largely Rio Negro water. 

11Large areas of Rio Negro and Rio SolimSes water.

12Size of areas of unlike water mucb smaller. Turbid waters have "grainy appearance, indicating flocculations.
REFERENCES 15

measured in the Amazon near Obidos, 75 

miles above the Tapajos.

Neither temperature nor chemical-quality 

gradients were indicated by temperature, 

specific-conductance, and pH measurements 

at various depths at the measuring sections 

near Obidos and near Manaus.

In the Rio Tapajos, about 3 miles above 

Santarem where water depth was about 80 

feet, samples taken at the surface and at 10- 

foot depth had specific conductances of 15 

and 17, and pH values of 6.0 and 7.1, respectively, at 1 p.m., July 13. However, these 

differences are considered too small to be 

meaningful. The temperature was 86.0°F at 

both the surface and the 10-foot depth. At 8 

p.m., the pH was 7.15 at the surface, and temperature and conductivity were unchanged.

In the Amazon River at Obidos, the temperature and pH were identical at the surface and at 10- and 50-foot depths at three 

cross-section locations where the total depth 

ranged from 68 feet to 175 feet. Conductivity 

readings showed no change to 10-foot depth 

and values were only slightly higher at 50- 

foot depth. Titrations for dissolved oxygen 

showed virtually the same values for water 

from different depths and from the surface 

taken at different times of day.

At the measuring section in the Amazon 

River below the Rio Negro, there was no 

change of temperature, conductivity, or pH 

with depth, but the dissolved-oxygen content 

was appreciably higher at depth in both the 

Solimoes water and the Negro water.

As mentioned earlier, the samples collected for laboratory analyses are not available at this writing. Consequently no data 

are available yet on sediment characteristics. Visual observation of sediment samples 

in the field indicated no suspended sediment 

in the Rio Negro and Rio Tapajos at the 

mouths, and only small concentrations in the 

Amazon itself. Field inspection of samples 

indicated no vertical gradient in the concentration of fine material. The concentration 

of sand grains decreased rapidly from bottom to top, but a few grains of very fine sand 

were evident in samples from 10-foot depth, 

where depth to riverbed was as much as 150

feet and velocities were as low as 4 feet per 

second. The largest particles in samples 

taken near both Obidos and Manaus appeared 

to be fine sand.

The occurrence of upwelling water in the 

form of mild but large-scale boils at the 

surface was evident in many places along 

the river. At first this manifestation seemed 

quite general, but later observation showed 

that it occurred only near the banks or in. 

areas where shoals were indicated on the 

charts. Appreciable activity well out in the 

channel appeared to occur only in patches or 

in bands extending across the river. This in 

turn was thought to indicate quite shallow 

water, but .inspection of the ship's echosounder chart at two or three of these locations indicated that the surface manifestation 

of turbulence occurred where depths were as 

great as 100 feet, downstream from deeper 

water. The boils probably result from upward vectors of velocity generated along the 

rising bed of the river in these reaches or 

from macroturbulent eddies generated by 

irregularities or bed configuration and velocity distribution (Sternberg, 1960).

REFERENCES

Bittencourt, A., 1946, Uma RegiSo Prospera: 

O Careiro; O Journal, Manaus (transcribed 

in Bol. Geog. 4), p. 1478-1480.

Durum, W.H.,Heidel, S.G., and Tison, L. J., 

1960, World-wide runoff of dissolved solids : Internat. Assoc. of Sci. Hydrology, pub. 

no. 51, p. 618-628.

Moraes, R., 1926, Na Plarilcie Amazonica: 

Manaus, Livraria Classica, 242 p. (6th ed., 

1960, Rio de Janeiro, Conquista, 23 p.)

Parde, Maurice, 1956, Quelques apergus 

relatifs a 1'hydrologie bre"silienne: Paris, 

51 p., La Houille Blanche.

Soares, L. de C., 1956, Excursion guidebook 

no. 8, Amazonia: Internat. Geog. Union, p. 

55.

Sternberg, H. O'R., 1956, A Agua e o Homen 

na Varzea do Careiro: Rio de Janeiro, 229 

p. and portfolio of maps.

____1960, Radiocarbon dating as applied to 

a problem of Amazonian morphology: Cong. 

Internat. de Geographie, XVIIIe , Rio de 

Janeiro, 1956, Comptes rendus, p. 399-424 

and insert map.

* U.S. GOVERNMENT PRINTING OFFICE : l»67 O 27«-OJO