Sediment budget for the 2000 LSSF Experiment,

in context of the last half century

David J. Topping, David M. Rubin,

Nancy J. Hornewer, Gregory G. Fisk,

James R. Allen, Elizabeth Fuller,

and Jamie P. Macy (USGS)

REVIEW

HYPOTHESES

• UNDER NORMAL POWERPLANT OPERATIONS, NEWLY INPUT TRIBUTARY SAND WILL BE EXPORTED FROM MARBLE CANYON WITHIN SEVERAL MONTHS

• SAND WILL ACCUMULATE IN THE REACH DOWNSTREAM FROM LEES FERRY WHEN DISCHARGES ARE HELD BELOW 9,000 cfs

MARBLE CANYON NET CHANGE

• -900,000 to - 2,100,000 metric tons, without estimates for additional inputs

• -500,000 to -1,700,000 metric tons, with estimates for additional inputs

• 500,000 metric tons is equivalent to 3 cm of erosion spread over the entire area of Marble Canyon

0.001

0.01

0.1

1

5000

10000

15000

20000

25000

30000

35000

2933329335293372933929341293432934529347293492935129353293552935729359

MENLO_SUSPENDED_SED_OUTPUT

SU

SP

EN

DE

D-S

AN

D C

ON

CE

NT

RA

TIO

N (

vo

l. %

)D

ISC

HA

RG

E (c

fs)

days after 0:00 on 1-1-20

0.0057%

0.0042%

ANOTHER COST:

SAND CONCENTRATIONS ARE HIGHER AFTER A SPIKE THAN BEFORE A SPIKE

CONCLUSIONS

• SAND BUDGET FOR MARBLE CANYON WAS NEGATIVE DURING AUGUST 1999-SEPTEMBER 2000

• 1999 PARIA RIVER SAND INPUTS WERE EXPORTED FROM MARBLE CANYON WITHIN 1-3 MONTHS

• SAND DID ACCUMULATE IN MARBLE CANYON DURING THE STEADY 8,000 cfs FLOWS, BUT NOT AS MUCH AS WAS ERODED DURING THE MAY SPIKE

• BECAUSE THE MARBLE CANYON SAND BUDGET WAS SLIGHTLY NEGATIVE FROM PRE-MAY SPIKE TO PRE-SEPT SPIKE, SAND CONCENTRATIONS WERE 20% LOWER DURING THE SEPTEMBER SPIKE

• BECAUSE THE SAND EXPORT FROM MARBLE CANYON WAS VERY SIMILAR TO THE SAND EXPORT PAST THE GRAND CANYON GAGE, VERY LITTLE CAN BE SAID ABOUT THE SAND BUDGET IN UPPER GRAND CANYON

• SILT AND CLAY CAN ALSO ACCUMULATE WHEN THE FLOWS ARE KEPT AT 8,000 cfs

• BETA SUGGESTS THAT THE CHANNEL AND EDDIES BELOW 8,000 cfs WERE MORE DEPLETED IN JUNE-JULY 2000 THAN AT ANY OTHER TIME