pening the jet tubes at Glen 

Canyon Dam on March 26, 1996, 

released from Lake Powell a controlled flood of water that traveled 

down the Colorado River in Grand 

Canyon. How fast did the water 

move? How long did it take for water 

to reach a particular point along the 

river? The answers to these questions 

are important because the speed of 

river water affects the amount of 

physical and chemical changes, such 

as warming by sunlight, that the 

water will undergo as it moves 

downstream. Also, very fine particles 

and substances dissolved in the water 

travel along with the water, and 

the speed of the water tells us

how fast these move downstream.

U.S. Department of the Interior

U.S. Geological Survey

Grand Canyon Monitoring and Research Program

The Colorado River

in Grand Canyon:

How Fast Does It Flow?

O

How is the Water Speed 

Measured?

One way to measure the speed of 

water is to tag it with a harmless 

substance that is easily identified and 

measured with the proper instruments. 

These substances are called water tracers 

and are commonly used in both ground 

water and surface water to track the 

water movement. A fluorescent dye 

developed specifically for this purpose 

has been used in surface-water studies 

for many years because it is safe and 

readily detectable at very low 

concentrations.

To make a measurement, dye is put 

into the river as nearly as possible at a 

single point and time. Samples of river 

water are collected at sites of known 

distances downstream as the dyed water 

passes. The samples are measured using 

an instrument designed to detect the very 

small amounts of dye present. The speed 

of the center of mass of the dyed water is 

determined from the data and represents 

the average speed of the water through 

the reach for the discharge during the 

measurement.

Dye movement was tracked by sampling the water and measuring the dye 

concentration at eight sites during the controlled flood.

Athough the dye is easy to see where it is first put into the river, it quickly mixes with 

the much larger mass of river water and becomes invisible. The highest concentration 

at sampling sites was between 5 and 35 parts per billion. One part per billion is about 

equal to one drop in a backyard swimming pool.

Ri ver

Lees Ferry

Pearce

Ferry

Gneiss Canyon

Li

le t t

do ra

Colo

Glen

Canyon

Dam

Grand

Canyon

National

Park

50 KILOMETERS

0 50 MILES

EXPLANATION

DYE-SAMPLING SITE

0

C

olora do

River

Colorado

35Υ

114Υ UTAH 112Υ 111Υ

ARIZONA

NEVADA

ARIZONA

ARIZONA

CALIFORNIA

Virgin River

Paria

Lake

Mead

113Υ 37Υ

36Υ

Rive r

Diamond

eek

Cr

PAGE

FLAGSTAFF

ver Ri

TUCSON

FLAGSTAFF

PHOENIX

ARIZONA
When Dam Releases are 

Constant, Water Moves 

Faster at Higher Dam 

Releases than at Lo wer

Releases

Measurements of water speed have 

been made in the Colorado River 

between Glen Canyon Dam and Lees 

Ferry at three different dam releases 

within the operating range of the 

powerplant at the dam —5,000, 15,000, 

and 23,000 ft

3

/s. At the lowest releases, 

water moved through the reach at an 

average speed of 0.7 mph, taking a little 

less than 1 day (22 hours) to travel the 

15 mi between the dam and Lees Ferry. 

At the highest releases, water moved at 

2.3 mph and took about 7 hours to travel 

the same distance. The speed of water 

was found to be directly related to the 

magnitude of dam releases.

The speed of water downstream from 

Lees Ferry has been measured at two dam 

releases—15,000 ft 3/s in 1991 and 

45,000 ft3/s during the controlled flood of 

March 1996. At 15,000 ft 3/s, the water 

moved at an average speed of 2.3 mph 

and took 41/2 days to travel the 235 mi 

from Lees Ferry to Gneiss Canyon, which 

is 10 mi downstream from Diamond 

Creek. At that same dam release, water 

flowed at an average speed of only 1.6 

mph from the dam to Lees Ferry. 

Downstream from Lees Ferry, water 

traveled almost twice as fast (4 mph) at 

45,000 ft3/s as it had at 15,000 ft 3/s.

Flow is Faster in Some 

Reaches than Others

The water mo ves through the 

reaches defined by dye-sampling sites 

faster or slower than the average speed 

depending on the channel shape and 

slope of the particular reach. For 

measurements made at both 15,000 and 

45,000 ft3/s, water moves more slowly 

than average from Lees Ferry to the 

Little Colorado River, 61 mi 

downstream, and about equal to or 

faster than average from that point 

downstream. The slowest reach 

downstream from Lees Ferry was in 

Lower Marble Canyon, which is just 

upstream from the Little Colorado 

River.

Water speed through reaches defined by sampling sites was less than the average 

for Marble Canyon and equal to or greater than the average for Grand Ca nyon for 

both constant dam releases measured.

Water speed from the dam to Lees Ferry has been measured at three dam 

releases and downstream from Lees Ferry at two releases. Wa ter moves a little 

more slowly upstream from Lees Ferry than downstream. We can use the results 

to estimate the average water speed for a range of constant discharges. For 

example, the data indicate that at 30,000 ft 3/s water would flow downstream from 

Lees Ferry at a little more than 3 mph. 

AVERAGE W

ATER SPEED, IN MILES PER HOUR

DAM RELEASES, IN CUBIC FEET PER SECOND

30,000 40,000

Fastest reach

Slowest reach

Average for 15,000 ft3/s dam releases

20,000

15,000 ft

3/s

0 10,000 50,000

0

1

2

3

4

5

W

ATER SPEED, IN MILES PER HOUR

DISTANCE DOWNSTREAM FROM LEES FERRY, IN MILES

100 150 200

Grand Canyon

Little Colorado River

Marble Canyon

0 50 250

1

5

Slowest reach

Fastest reach

Lees Ferry downstream Example

Glen Canyon Dam to Lees Ferry

Average for 45,000 ft3/s dam releases

2

3

4
How has Knowledge of the 

Water Speed Helped?

Knowledge of the speed of Colorado 

River water in Grand Canyon will help 

managers make decisions needed to 

protect the unique natural resources. The 

speed of water through a reach is one 

factor that controls the amount of time 

the water is exposed to light. Knowledge 

of the water speed has helped to provide 

an understanding of light-dependent 

processes, such as photosynthesis and 

respiration of aquatic plants, in the reach 

between the dam and Lees Ferry. Also, 

because water speed is controlled in part 

by channel roughness, which is very 

difficult to measure directly , 

measurements of water speed provide a 

means to determine values of this 

important channel characteristic. 

Channel-roughness values computed 

from the water speed have been used to 

develop a relation between roughness and 

river stage that was needed to develop a 

numerical model that accurately 

computes discharge 

throughout the canyon. 

Accurate knowledge 

of discharge at any 

point in the canyon 

produced by given 

dam releases is 

critical to assess -

ment of effects of 

those releases on 

resources.

The difference in speed of the water 

and the discharge wave caused the water 

to move through some reaches faster and 

others more slowly than when releases 

were constant. The measured water 

speeds during the rapidly changing 

releases were higher than those measured 

during the constant 15,000 f t

3

/s 

release for the reaches in which the dyed 

water moved with the higher, faster part 

of the discharge wave and lower for 

those in which it moved with the lower, 

slower part of the wave. Averaged over 

the whole 235 mi measured, the speed 

for rapidly changing releases was the 

same as that measured during the 

constant 15,000 ft

3

/s release.

—Julia B. Graf

Water speed measured in reaches between sampling sites was either higher or lower 

at rapidly changing releases than at constant releases, depending on whether the dyed 

water moved through the reach with the peak or trough of the discharge wave. DISCHARGE, IN CUBIC FEET PER SECOND

Discharge waves move downstream faster than the water. For example, in May 1991, 

the discharge waves produced by rapidly changing dam releases moved through the 

canyon in about 12/3 days, whereas the water took about 41/3 days to travel the 235 miles 

from Lees Ferry to Gneiss Canyon. The dye was injected at Lees Ferry into the 

discharge wave labeled wave 1 (top graph). Wave 1 passed the Gneiss Canyon 

sampling location on May 8, whereas the dyed water passed that location late on May 10.

15,000

30,000

0

30,000

MAY 1991

6 7 8 9 10 11

15,000

0

30,000

Lees

Ferry

Wave 1

Dye

injected

Center

of dyed

water

Center of

dyed water

Wave 1

Wave 1 Wave 2 Wave 3

Wave 2 Wave 3

Wave 2 Wave 3

Gneiss

Canyon

Little

Colorado

River

15,000

0

when dam releases changed from

3,250 ft 3/s at night to 26,600 ft 3/s at 

midday and averaged 15,000 ft 3/s over 

each 24-hour period. Dye was released 

at Lees Ferry not long before the peak of 

the discharge wave reached that point. 

By the time the dyed water had reached 

the Little Colorado River mouth, 61 mi 

downstream, it was moving with the 

trough of the same discharge wave. At 

Gneiss Canyon, 235 mi downstream 

from Lees Ferry, almost three discharge 

waves had passed the Gneiss Canyon 

water-sampling location before the dyed 

water arrived.

How do Rapidly Changing 

Releases Affect the Speed 

of the Water?

We’ve seen that the speed of water 

released from the dam is higher for higher 

dam releases when releases are constant 

throughout the dye measurement. When 

dam releases change rapidly during the 

day, as they normally do for production 

of electricity, a wave of water is produced 

that moves downstream, but the water 

itself moves more slowly than the surface 

wave.

A measurement of water speed was 

made during an 11- day period in 1991

WATER SPEED, IN MILES PER HOUR

DISTANCE DOWNSTREAM FROM LEES FERRY, IN MILES

0 50 100 150 200 250

1

2

3

Average for both releases

Constant 15,000 ft3/s releases

Rapidly changing releases
Decemberer 1997

USGS Fact Sheet

FS-168-97

At each site, water samples were collected from near the riv erbank during passage of the dye and measured in the field f or dye 

concentration using a fluorometer. At the site pictured, the dye concentration peaked at around midnight. Samples from a ll sites 

were retained and remeasured in the lab under controlled tem perature conditions to obtain the final concentrations.

Marzolf, G.R., Bowser, C.J., Stephens, D.W., Hart, 

R.H., and Vernieu, W.S., 1997, Flood effects 

on benthonic metabolism of carbon and oxygen 

in Glen Canyon Dam's tailwater: American 

Geophysical Union, EOS, Transactions, v. 77, 

no. 46, p. F258.

Wiele, S.M., and Smith, J.D., 1996 , A reachaveraged model of diurnal discharge wave 

propagation down the Colorado River through 

the Grand Canyon: Water Resources 

Research, v. 32, no. 5, p. 1375–1386.

Selected References

Graf, J.B., 1995, Measured and predicted velocity 

and longitudinal dispersion at steady and 

unsteady flow, Colorado River, Glen Canyon 

Dam to Lake Mead: Water Resources Bulletin, 

v. 31, no. 2, p. 265–281.

Konieczki, A.D., Graf, J.B., and Carpenter, M.C.,

1997, Streamflow and sediment data collected 

to determine the effects of a controlled flood 

in March and April 1996 on the Colorado River 

between Lees Ferry and Diamond Creek, 

Arizona: U.S. Geological Survey Open -File 

Report 97–224, 55 p.

For more information contact:

U.S. Geological Survey

520 N. Park Avenue, Suite 221

Tucson, AZ 85719

Julia B. Graf

(520) 670-6671, ext. 252

http://wwwdaztcn.wr.usgs.gov