Project A: Streamflow, Water Quality, and Sediment

Transport and Budgeting in the Colorado River Ecosystem

We collect, post, and analyze the following data at stations located through the 

Colorado River Ecosystem, including key tributaries...

• Element 1: Stream gaging

– Stage

– Discharge

• Element 2: Water quality

– Water temperature

– Salinity (specific conductance)

– Turbidity

– Dissolved Oxygen

• Element 3: Sediment transport and budgeting

– Suspended- and bed-sediment data

– Sediment loads (silt and clay loads and sand loads)

– User-interactive sand budgets in 6 reaches from Lees Ferry to Lake Mead

• All elements

– User-interactive duration-curve tool for any continuous parameter

Almost all other projects funded by the Glen Canyon Dam Adaptive Management 

Program (GCDAMP) use these data, and data from this project informs 10 LTEMP goals

Funding: GCDAMP provided $1.15 million during FY 2022
Evaluation of LTEMP sand management

David J. Topping, U.S. Geological Survey

Paul E. Grams , U.S. Geological Survey

Ronald E. Griffiths, U.S. Geological Survey

Matt Kaplinski, U.S. Geological Survey

Joel A. Unema, U.S. Geological Survey

David J. Dean, U.S. Geological Survey

Katie A. Chapman, Northern Arizona University

Joseph E. Hazel, Jr.

The information in several of these slides is preliminary and is subject to revision. It is being 

provided to meet the need for timely best science. The information is provided on the 

condition that neither the U.S. Geological Survey nor the U.S. Government shall be held liable 

for any damages resulting from the authorized or unauthorized use of the information.
Downward spiral has likely occurred in long-term sand mass balance...

and reflected in the high-elevation volume of an unknown percentage 

of the sandbars

>28 million metric tons of sand eroded since 1963, mostly during 3–4 periods of 

sustained high dam releases (Topping and others, JGR, 2021)

~12 million metric tons eroded in late 1990s alone (6 from Marble and 6 from Grand) 

Figures from Topping and others (JGR, 2021) Preliminary figures from Grams, Gushue, Hazel (do not cite)

*~5.5 million Mg 

sand erosion 

measured but 

not predicted in 

1965

*>2 million Mg 

sand erosion 

measured but 

not predicted in 

1965

*

*
Some of the sand involved in sandbar deposition 

during HFEs is part of a “bank account” that cannot 

be replaced

• Although the Paria River is 

by far the dominant 

modern supplier of sand 

(Topping and others, JGR, 

2021), a large percentage 

(~30–50%) of the sand 

stored in sandbars is relict 

“pre-dam” sand (Chapman 

and others, GSA Bulletin, 

2020)

• Stratigraphic and groundpenetrating-radar data 

suggest strongly that predam sand exists at depth in 

at least some sandbars 

(Barnhardt and others, 

USGS-OFR, 2001)
8,000 ft3/s

25,000 ft3/s

15,000 ft3/s

45,000 ft3/s

High-elevation sand

Figure modified from Hazel and others (USGS-PP, 2022) 
67% of the long-term sandbar monitoring sites in Marble Canyon 

had less high-elevation sand in October 2022 than in June 1990,

Data from USGS (2023a)

whereas only 11% of the long-term sites in Grand Canyon had 

less high-elevation sand in October 2022 than in June 1990

∞
High-elevation sand at many of the long-term sandbar 

monitoring sites in Marble Canyon defines a downward spiral 

Data from 37 surveys depicted; data from USGS (2023a)

Only repeated sand-enriched HFEs may reverse this trend, 

as during 2012–2014
Not sustainable 

Bank account mined to 

deposit sandbars

“Living on credit”

Not sustainable Sustainable

“Living 

within your 

means”

Paria

HFE

Paria

HFE

Scenario 1 Scenario 2 Scenario 3

Sustainable management of sand under the LTEMP sediment goal 

thus requires neutral to positive trends in both the sand mass 

balance (i.e., the bank account) and the high-elevation sandbar 

volume (i.e., your expenditures) over decades
Metrics Example: The Bank Account

POSSIBLE SUCCESS! Sustainable in 

Lower Marble Canyon if highelevation sandbar volume is positive 

during this period.

POSSIBLE FAILURE Not sustainable in 

Eastern Grand Canyon regardless of 

whether high-elevation sandbar 

volume is positive during this period.

Data from Topping and others (JGR, 2021); USGS (2023b)
Conducting sand-enriched HFEs at every opportunity 

is central to the LTEMP experimental design

...in future controlled floods, more sand is required to achieve 

increases in the total area and volume of eddy sandbars throughout all 

of Marble and Grand Canyons. Annual tributary inputs of sand much 

larger than one million metric tons occur but are relatively rare. 

Therefore, “more sand” could be achieved directly by augmentation

from sand trapped in the reservoir impounded by Glen Canyon Dam or 

perhaps indirectly by following each large tributary input of sand with 

short-duration controlled floods. Frequent short-duration controlled 

floods under sand-enriched conditions could result in the downstream 

propagation (into the downstream half of Marble Canyon and into 

Grand Canyon) of the gains in total eddy-sandbar area and volume 

observed in the upstream half of Marble Canyon during the 2004 

controlled-flood experiment.

Excerpted from Topping and others (FISC, 2006)
HFE-Protocol Period

Upper Marble Canyon

Data from USGS (2023a, b)

POSITIVE POSITIVE

Possibly sustainable
HFE-Protocol Period

Lower Marble Canyon

Data from USGS (2023a, b)

POSITIVE POSITIVE

Possibly sustainable
HFE-Protocol Period

Eastern Grand Canyon

Data from USGS (2023a, b)

NOT sustainable

NEGATIVE POSITIVE
HFE-Protocol Period

East-Central Grand Canyon

Data from USGS (2023a, b)

POSITIVE POSITIVE

Possibly sustainable
HFE-Protocol Period

West-Central Grand Canyon

Data from USGS (2023a, b)

INDETERMINATE POSITIVE

Possibly sustainable
Unanticipated 4th scenario

“Abandonment of the experimental design” Paria HFE PariaParia

Export rate increases 

as bed-sand fines

Sandbars erode to 

low levels perhaps 

difficult to recover 

from
LTEMP Period

Upper Marble Canyon

Data from USGS (2023a, b)

POSITIVE NEGATIVE

Failing to follow LTEMP experimental design; sandbar erosion
LTEMP Period

Lower Marble Canyon

Data from USGS (2023a, b)

POSITIVE NEGATIVE

Failing to follow LTEMP experimental design; sandbar erosion
LTEMP Period

Eastern Grand Canyon

Data from USGS (2023a, b)

INDETERMINATE NEGATIVE

Failing to follow LTEMP experimental design; sandbar erosion
LTEMP Period

East-Central Grand Canyon

Data from USGS (2023a, b)

BARELY INDETERMINATE NEGATIVE

Failing to follow LTEMP experimental design; sandbar erosion
LTEMP Period

West-Central Grand Canyon

Data from USGS (2023a, b)

LIKELY POSITIVE ZERO SLOPE

Sustainable ? Sandbars starting to degrade
Tributary sand inputs increase 

storage and EXPORT

RM 30

3,530 ft3/s 35,300 ft3/s

Figure from Topping and others (JGR, 2021) Data from USGS (2023b)

Bed-sand fining offsets effect on sand transport of lower dam releases
Despite similar sand-supply magnitudes, sand retention 

decreased faster between 2021 and 2022 than did discharge 

Data from USGS (2023b)
Conclusions

• LTEMP sand management is failing because of the abandonment of the 

experimental design

• 6 years of LTEMP, 3 HFE triggers, only 1 HFE

• Dam maintenance schedule has also compromised LTEMP; last full-magnitude 

HFE was in 2012

• A substantial number of sandbars in Marble Canyon are at their lowest 

condition since monitoring began

• Although sandbar gains did occur during the HFE-Protocol period, it remains 

unclear if it is possible to rebuild sandbars to their early 1990s condition 

because of the large amount of sand eroded during the high flows of the late 

1990s (1997 had the second longest period of sustained high discharge after 

1984; Topping and others, USGS-PP, 2003)

• LTEMP may reach its conclusion and we may still not know if sustainable sand 

management is possible
Thank you
References • Barnhardt, W.A., Kayen, R., Rubin, D., and Minasian, D.L., 2001, The internal structure of sand bars on the Colorado 

River, Grand Canyon, as determined by ground-penetrating radar: U.S. Geological Survey Open-File Report 2001- 425, 74 p. https://doi.org/10.3133/ofr01425

• Chapman, K.A., Best, R.J., Smith, M.E., Mueller, E.R., Grams, P.E., and Parnell, R.A., 2020, Estimating the 

contribution of tributary sand inputs to controlled flood deposits for sandbar restoration using elemental tracers, 

Colorado River, Grand Canyon National Park, Arizona: Geological Society of America Bulletin, v. 133, p. 1141–1156. 

https://doi.org/10.1130/B35642.1

• Hazel, J.E., Jr., Kaplinski, M.A., Hamill, D., Buscombe, D., Mueller, E.R., Ross, R.P., Kohl, K., and Grams, P.E., 2022, 

Multi-decadal sandbar response to flow management downstream from a large dam—The Glen Canyon Dam on 

the Colorado River in Marble and Grand Canyons, Arizona: U.S. Geological Survey Professional Paper 1873, 104 p., 

https://doi.org/10.3133/pp1873

• Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., Melis, T.S., Wright, S.A., Kaplinski, M., Draut, A.E., and 

Breedlove, M.J., 2006, Comparison of sediment-transport and bar-response results from the 1996 and 2004 

controlled-flood experiments on the Colorado River in Grand Canyon: Proceedings of the 8th Federal Inter-Agency 

Sedimentation Conference, Reno, Nevada, April 2-6, 2006, http://acwi.gov/sos/pubs/8thFISC/Session 1B- 3_Topping.pdf

• Topping, D.J., Grams, P.E., Griffiths, R.E., Dean, D.J., Wright, S.A., and Unema, J.A., 2021, Self-limitation of sand 

storage in a bedrock-canyon river arising from the interaction of flow and grain size: Journal of Geophysical 

Research: Earth Surface, v. 126, e2020JF005565. https://doi.org/10.1029/2020JF005565

• U.S. Geological Survey, 2023a, Grand Canyon sandbar monitoring, Grand Canyon Monitoring and Research Center: 

accessed on January 13, 2023, at http://www.usgs.gov/apps/sandbar/

• U.S. Geological Survey, 2023b, Discharge, sediment, and water quality monitoring, Grand Canyon Monitoring and 

Research Center: accessed on January 13, 2023, at http://www.gcmrc.gov/discharge_qw_sediment/
Project A work completed in FY 2022 addressed the following two hypotheses 

paraphrased from the Glen Canyon Dam Long-Term Experimental and Management 

Plan (LTEMP) Environmental Impact Statement (EIS) and earlier GCDAMP documents

• Glen Canyon Dam can be operated such that the sand resources in the Colorado 

River ecosystem (CRe) are sustainable.

• Glen Canyon Dam can be operated such that the other CRe resources affected by 

dam operations can be sustainably managed. In this usage, “dam operations” 

refers to the amount and quality of the water released from the dam, where 

“amount” refers to stage and streamflow, and “quality” refers to temperature, 

salinity, turbidity, and dissolved oxygen.

FY 2022 products

• All required monitoring data collected but only LARGELY processed and posted to 

Project A’s website (https://www.gcmrc.gov/discharge_qw_sediment/) and to NWIS

• 1 peer-reviewed journal article in the Proceedings of the National Academy of Sciences 

NEXUS, 1 peer-reviewed article in Water Resources Research, and 1 USGS OFR 

published; 1 USGS Professional Paper in press and 1 USGS OFR through review (see list 

in Annual Report)