USGS AZ WSC sampling near the PARIA RIVER AT LEES FERRY, AZ 

gage during a flood on the Paria River

US D-74 sampler suspended from 

fixed reel on bridge

ISCO 6712 automatic pump 

sampler

INTAKE location for the ISCO 6712 

pump sampler
Mainstem flow

Mainstem flow and sediment

Tributary flow and sediment

Sediment budget reach

RM 0-30 – upper Marble Canyon

RM 30-61 – lower Marble Canyon

RM 61-87 – eastern Grand Canyon

RM 87-166 – central Grand Canyon

RM 166-225 – western Grand Canyon

Between July 1 and November 17, 2012, ...

Between 551,000 

and 782,000 metric 

tons accumulated 

in upper Marble 

Canyon

91,000 – 101,000 metric 

tons were transported 

past the RM 30 gage

617,000 – 769,000 metric tons entered 

Colorado River from the Paria River

Little to no fine 

sediment 

accumulated in 

lower Marble 

Canyon

Mass balance prior to 2004 and 2008 HFEs

July 1 to November 2004: 275,000 – 491,000 metric tons

December 2004 – March 2008: 567,000 – 1,823,000 metric tons

2. HFER Protocol 

implementation
Cumulative sand 

delivery to the 

Colorado River

617,000

769,000

Paria River at Lees Ferry

water
91,000

101,000

Cumulative amount of sand transported out 

of upper Marble Canyon (past RM30 gage)

water

Cumulative amount of sand 

available for transport in upper 

Marble Canyon

551,000

782,000
water

Sand transport past 

RM30

Sand mass 

balance in upper 

Marble Canyon

212,000

477,000
Review from last year’s 

knowledge assessment

From scale analysis of Exner equation, sandbar 

deposition rates depend on spatial changes in 

sand flux (depth-integrated product of flow and 

concentration) into eddies, which in turn depend 

on

•flow conditions 

•bed-sand grain size 

•bed-sand area (amount)
∆η

∆t

∝ −

∆ u

*

4.5

hAbDb

−2.5

( )

∆x

FLOW BED SAND

•Spatial decrease in “flow” leads to deposition

•Spatial increase in bed-sand grain size leads to deposition

•Spatial decrease in bed-sand area (amount) leads to deposition

•Greatest deposition rates occur in eddies when greatest flow 

“deceleration” occurs between channel and eddy, and sand in 

upstream channel is as fine as possible and amount on upstream 

channel bed is relatively large
In the previous slide, there is no distinction made between new tributary 

supplied sand and background sand storage, both are combined in Db and 

Ab. 

Thus, if background sand storage in a reach of the Colorado River 

decreases in volume or coarsens over time, then similar magnitudes of 

tributary sand inputs will result in progressively lower eddy-sandbar 

deposition rates over a series of artificial floods released from Glen 

Canyon Dam. 

Conversely, if background sand storage remains constant over time, then 

similar magnitudes of tributary sand inputs will result in similar eddysandbar deposition rates over a series of artificial floods released from 

Glen Canyon Dam.

And, if background sand storage in a reach of the Colorado River increases 

in volume or fines over time, then similar magnitudes of tributary sand 

inputs will result in progressively higher eddy-sandbar deposition rates 

over a series of artificial floods released from Glen Canyon Dam. 
Suspended-sand concentration

(after Topping and others, USGS OFR 2010-1128, 2010) 
Suspended-sand median grain size

(after Topping and others, USGS OFR 2010-1128, 2010) 
Bed-sand median grain size

(after Topping and others, USGS OFR 2010-1128, 2010) 
Bed-sand area (amount)

(after Topping and others, USGS OFR 2010-1128, 2010) 
Sand-concentration ranking of 

controlled floods 

RM 0 RM 30 RM 61 RM 87 RM 166 RM 225

2008 2008 2008 1996 ≈ 2008 2008 2012

2004 2004 2004 ≈ 2012 2012 ≈ 2004 1996 2008

1996 2012 1996 2012 2004

•75% of sand-concentration rankings agree with bed-sand area (amount) analysis

•Only 40% of sand-concentration rankings agree with bed-sand grain-size analysis

•Mass-balance sand budgets should teach us more...
Sand mass-balance context

Period of budget Upper Marble Canyon Lower Marble Canyon

July 2002 -

pre2004 flood

330,000 ± 194,000 -280,000 ± 110,000

pre2004 flood –

pre2008 flood

900,000 ± 640,000 290,000 ± 350,000

pre2008 flood –

pre2012 flood

-1,500,000 ± 620,000

(mostly during MayAugust 2011)

-12,000 ± 430,000

July 2012 –

pre2012 flood

670,000 ± 120,000 18,000 ± 15,000

during 2012 flood -320,000 ± 13,000 -78,000 ± 36,000

Shown are changes in sand mass (metric tons)
Relations between sand mass balance

and sand concentrations during 

controlled floods

Upper Marble Canyon Lower Marble Canyon

Cumulative

post-July 2002

sand mass

before flood

(metric tons)

% of sand

concentration

during 2004 

flood

Cumulative

post-July 2002

sand mass

(metric tons)

% of sand

concentration

during 2004 

flood

2004 flood 330,000 100% -280,000 100%

2008 flood 1,230,000 140% 10,000 140%

2012 flood -270,000 68% -2,000 95%

post 2012 flood -590,000 -80,000
Intervening dam operations greatly 

affect sand concentrations and therefore sandbar 

deposition rates during controlled floods...

Should sand accounting be reset to zero every July?

• Twice as much sand accumulated in upper Marble Canyon 

during the months preceding the 2012 flood than during the 

months preceding the 2004 flood.

• But sand concentrations at RM30 during the 2012 flood were 

only ~68% of those during the 2004 flood. 

This apparent paradox was the result of the scour of >1 million 

metric tons of sand from upper Marble Canyon during the high 

equalization flows of May-August 2011.
New tools for this year

• Sand budgets on web by April 2013

• Station discharge, QW, and sediment data on 

web at selected stations now at

http://www.gcmrc.gov/discharge_qw_sediment/