Effects of Low Summer Stea

(LSSF) and Habitat Maint

Flows in 2000 on Sedim

Transport and Storage in M

Upper Grand Canyon

John C. Schmidt

Utah State University
Study Team

U.S. Geological Survey -- Water 

Division and Pacific Marine Geolo

Rubin, Hornewer, Anima, Wiele, 

Sandbar Studies Group,

Northern Arizona University (Hazel a

Fluvial Geomorphology La

Utah State University (Schmidt, Goekin

Webb

Grand Canyon Monitoring and Rese

(Melis)
Sediment Budg

• Fundamental conceptual tool 

organizing knowledge, identifyresearch needs, and developimanagement plans
Study design

• Inflow - outflow = change in stora

banks)

• Budget for Marble Canyon

I(Lake Powell, Paria,, other tributaries) - O(lower MC gage) 

• Examine how each of these terms 

downstream
Sediment-transport r
Study Plan

• Measure sediment inflow and 

gages

• Measure changes in amount o

sediment on the bed

• Measure changes in sand bars 

term study sites and in long treaches
Data 

Collection

1,2,3,4,5,6 -

gages

* - detailed 

survey sites

boxes - air 

photo analyses 
Hypotheses

1) Sediment accumulates during low f

ft

3/s)

2) Sand does not accumulate during n

operations

3) The “effectiveness” of a high flow i

to the amount of fine sediment avatransport immediately before the f

4) There will be a downstream shift in 

sinks associated with a downstream fine sediment supply and fine sedim
Hydrograph
There was little inflow 

from tributaries.

200300400500600700800900

1000

LCR 

GC

LCR Grand 

Canyon
There was little fi

sediment inflow

0.00.51.01.52.02.5

AUG 1999

SEP 1999

OCT 1999

NOV 1999

DEC 1999

JAN 2000

FEB 2000

MAR 2000

APR 2000

MAY 2000

JUN 2000

JUL 2000

AUG 2000

SEP 2000

OCT 2000

PARIA RIVERPARIA RIVER +AND- 20%LITTLE COLORADO RIVERLITTLE COLORADO RIVER +AND- 30%HOUSE ROCK WASH (after July 25, 2000)

CUMULATIVE SAND SUPPLY (million metric tons)

MAY 2000 SPIKE FLOW

SEPTEMBER 2000 SPIKE FLOW

0.01.02.03.04.05.0

AUG 1999

SEP 1999

OCT 1999

NOV 1999

DEC 1999

JAN 2000

LOWER MARBLE CANYLOWER MARBLE CYN GGRAND CANYON GAGEGRAND CANYON GAGE 

CUMULATIVE SAND EXPORT (million metric tons)

Sand supply from 3 tributaries

Sand export 

Canyon and G
Fine sediment accumulated 

Canyon when flows < 800

-1500000-1000000

-500000

0

500000

10000001500000

AUG

SEP

OCT

NOV

DEC

JAN

FEB

MAR

APR

MAY

MARBLE CANYONUPPER GRAND CANYON

SAND BUDGET (metric tons)

1999 2000

SUBPERIOD 1

EROSION

ACCUMULATION

-100000

-50000

0

50000

100000

MARBLE CANYONUPPER GRAND CANYON

JUNE JULY AUGUST SEPTEMBER

SAND BUDGET (metric tons)

SUBPERIOD 4

EROSION

ACCUMULATION

-500000-400000-300000-200000-100000

0

100000200000300000400000500000

MARBLE CANYONUPPER GRAND CANYON

SAND BUDGET (metric tons)

SUBPERIOD 5 (SEPT

-500000-400000-300000-200000-100000

0

100000200000300000400000500000

MARBLE CANYONUPPER GRAND CANYON

SAND BUDGET (metric tons)

SUBPERIOD 2 (MAY SPIKE FLOW)

EROSION

ACCUMULATION
The concentration of fine sed

transport increased downs

0.01

0.1

1

10

100

1000

0

10

20

30

40

50

60

70

80

90

100

AFTER MAY SPIKE FLOW (Q=480 m3/s steady)JULY (Q=230 m3/s steady)SEPTEMBER SPIKE FLOW (Q=870m3/s steady) 

SURFACE SAND CONCENTRATION (mg/l)

RIVER MILE

MOUTH OF THE PARIA RIVER

MOUTH OF THE LITTLE COLORADO RIVER

0.01

0.1

1

10

100

1000

0

10

20

30

AFTER MAY SPIKE JULY (Q=230 m3/s sSEPTEMBER SPIK

SURFACE SILT & CLAY CONCENTRATION (mg/l) 

MOUTH OF THE PARIA RIVER

Sand Silt 
High sand concentration

not sustained during hig

0

100200300400500600700800900

100011001200130014001500

-1 0 1 2 3 4

MAY SPIKE LOWER MARBLE CANYON GAGEMAY SPIKE GRAND CANYON GAGESEPTEMBER SPIKE RIVER-MILE 30SEPTEMBER SPIKE LOWER MARBLE CANYON GAGE SEPTEMBER SPIKE GRAND CANYON GAGE

SUSPENDED-SILT&CLAY CONCENTRATION (mg/l)

DAYS AFTER ARRIVAL OF STEADY 870m3/s DISCHARGE

0

200400600800

10001200140016001800200022002400260028003000

-1 0 1 2 3 4

MAY SPIKE LOWER MARBLE CANYON GAGE MAY SPIKE GRAND CANYON GAGESEPTEMBER SPIKE RIVER-MILE 30SEPTEMBER SPIKE LOWER MARBLE CANYON GAGE SEPTEMBER SPIKE GRAND CANYON GAGE

SUSPENDED-SAND CONCENTRATION (mg/l)

DAYS AFTER ARRIVAL OF STEADY 870m3/s DISCHARGE

0.070.080.090.100.110.120.130.140.150.160.170.180.190.20

-1 

SUSPENDED-SAND D 50 (mm)

Suspended silt and 

clay concentrations

Suspended sand 

concentrations
Accounting for san

change
Long-term 

trends, 8-25K zone:Today’s area is smaller than in 1984.Today’s area probably smaller than in 1990.

0

10002000300040005000

1984 1987 1990 1

AREA, IN SQUARE METERS

RG

PH

LF

TG

Marble Canyon

average

0

10002000300040005000

1984 1987 1990 

AREA, IN SQUARE METERS

PH

RGTG

LF

Marble Canyon

average

Mean

Median

(USU and NAU)
There was no 

significant change in the volume of eddy sand bars at elevations higher than the stage of 25,000 ft3/s. There 

was no reversal of long-term trends.

0 500 

0

100020003000400050006000

0

100020003000400050006000

0

100020003000400050006000

(NAU)

UpperMarble

LowerMarble

UpperGrandCanyon
Site to site changes 

in the volume of sand at elevations between 8000 and 25,000 ft3/s were highly variable.

0 500 1000 

0

2000400060008000

1000012000

444555

0

2000400060008000

1000012000

0

2000400060008000

1000012000

3-Mile 8-Mile 16-Mile 22-Mile 30-Mile 32-Mile 

(NAU)

UpperGrandCanyon

LowerMarble

UpperMarble

Deposition during spike flows: RM 30, 51, 55, 65Erosion during May spike flow: RM 3, 45, 68Erosion during September spike flow: RM 50, 87
Average changes

• Eddy sand was exchanged 

between low and med elevations.

• During high flows, sand is 

eroded from low elevation and transferred to higher elevations. Evidence points to more erosion near Lees Ferry than elsewhere.

• During low flows, banks 

erode and some of this sand accumulates in the eddy at lower elevation.

• Trends differ in UGC, 

perhaps indicating more sand on bed.

Although the Sept spike increased 

of backwaters, the resultant cha

no different from what has existe

past.

(USU)
Conclusions

• Continued evidence of supply limit

high flows.

• Fine sediment accumulates when • During LSSF (< 8K), eddy-bar at t

edge was eroded but sand accumustage.

• Indications of greater erosion of b

Lees Ferry; 

• Changes in bar topography during 

increase the area of backwaters, bsignificantly different than historic
Implications

• Flows < 8 K to retain fine sed

bed and in eddies

• High flows cause erosion of lo

elevation eddy sand and depoelevation sand under conditiolimited supply

• Changes caused by 2000 did 

reverse long-term degradatioErosion may be greater near than further downstream.


Summary of the effects of the LSS

on Marble and upper Grand C

5 nc nc43 nc2 nc1 nc ,Upper Grand Canyon5 nc4321

Midbar (n=

Low-elev. bar area (n=19)

Mid-elev. bar area (n=19)

Reachwide bar area

Bed grain size

Sand mass

Marble Canyon