U.S. Department of the Interior

U.S. Geological Survey

Project B Overview and 

Evaluation of High-Flow Experiments During Aridification

Glen Canyon Dam Adaptive Management Program

Annual Reporting Meeting

January 25, 2023

Paul Grams

U.S. Geological Survey

Southwest Biological Science Center

Grand Canyon Monitoring and Research Center

*This information 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 liablefor any damages resulting 

from the authorized or unauthorized use of the information.
Acknowledgements Project B personnel:

Paul Grams, Katie Chapman, Matt Kaplinski, Keith Kohl, 

Gerard Salter, Shannon Sartain, and Robert Tusso

GIS and website support:

Thomas Gushue, Caitlin Andrews, and Erica Byerley

Collaborators and field assistants:

David Topping and Project A, Erich Mueller, Scott Wright, Jon Nelson, 

GCRG, Jeff Behan, Sinjin Eberle, Jesse 

Collier, Daniel Buscombe, Robert Ross, 

Daniel Hamill, David Rubin, Joel 

Sankey, Jack Schmidt, Rod Parnell, 

Bryan Cooperrider, Karen Koestner, 

Emily Thompson, Daniel Hadley, Ryan 

Semptua, Geoff Gourley. Somer Morris. 

Lydia Manone, Lauren Tango, John 

O’Brien, Morgan Barnard, Pete 

Koestner, Logistics team: Ann-Marie, 

Seth Felder, Dave Foster, Clay Nelson, 

Lucien Bucci, and Fritz!

photo: Geoff Gourley

photo: Jeff Behan

photo: Geoff Gourley
Project B: Sandbar and Sediment Storage Monitoring and 

Research 

• Project Elements

• B.1 Sandbar Monitoring

• B.2 Bathymetric and topographic mapping for monitoring long-term trends in 

sediment storage

• B.3 Control Network and Survey Support

• FY 2021 involvement in other projects: 

• O.2 (sediment dynamics in Western Grand Canyon) 

• L (overflight remote sensing)

• Project Objectives

• track the effects of individual High Flow Experiments (HFEs) on sandbars

• monitor the cumulative effect of successive HFEs and intervening operations on 

sandbars and sand conservation

• investigate the interactions between dam operations, sand transport, and eddy 

sandbar dynamics

• GCDAMP FY2022 Funding: $994,345

• Cooperators: Northern Arizona University, Grand Canyon River Guides, 

Southern Utah University
Project B: AMP goals addressed and information provided

• LTEMP goal: 

– “Increase and retain fine sediment volume, area, and distribution in the Glen, Marble, and Grand 

Canyon reaches above the elevation of the average base flow for ecological, cultural, and 

recreational purposes.”

• Question from HFE Protocol: 

– “Can sandbar building during HFEs exceed sandbar erosion during periods between HFEs, such 

that sandbar size can be increased and maintained over several years?”

• Project B address these questions by two related monitoring efforts:

– Annual sandbar and campsite monitoring (sandbar surveys and daily photographs)

• Annual assessment of the effects of HFEs and other dam operations on selected sandbars and campsites.

• Assessment of immediate response to HFEs by network of remote time-lapse cameras

– Periodic channel mapping (Combined topographic and bathymetric mapping)

• Evaluation of LTEMP performance by measuring long-term trends in sand area, volume, and distribution from a large 

sample of sandbars. 

• Measurement of long-term trends in sand storage on the riverbed. 
Project B: Publications (2022)

• Hazel, J. E., Jr., Kaplinski, M. A., Hamill, D., Buscombe, D., Mueller, 

E. R., Ross, R. P., Kohl, K., & 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.

• Kaplinski, M., Hazel, J. E. J., Grams, P. E., Gushue, T., Buscombe, 

D. D., & Kohl, K. (2022). Channel mapping of the Colorado River 

from Glen Canyon Dam to Lees Ferry in Glen Canyon National 

Recreation Area, Arizona. U.S. Geological Survey Open-File Report 

2022-1057. https://doi.org/10.3133/ofr20221057.

• Kaplinski, M., Hazel, J.E. Jr, Grams, P.E., Gushue, T., Buscombe, 

D.D., and Kohl, K., 2022, Channel mapping Glen Canyon Dam to 

Lees Ferry in Glen Canyon National Recreation Area, Arizona -

Data: U.S. Geological Survey data release, 

https://doi.org/10.5066/P98GFP93.

Data and web applications

• Images from remote camera monitoring of sandbars: 

https://grandcanyon.usgs.gov/gisapps/sandbarphotoview

er/RemoteCameraTimeSeries.html

• Images from GCRG adopt-a-beach program: 

https://grandcanyon.usgs.gov/gisapps/adopt-abeach/index.html

• Data from long-term sandbar monitoring sites: 

https://www.usgs.gov/apps/sandbar/
Project B: Key findings with respect to LTEMP Goals and 

Knowledge Assessment

• LTEMP goal: 

– “Increase and retain fine sediment volume, area, and distribution in the 

Glen, Marble, and Grand Canyon reaches above the elevation of the 

average base flow for ecological, cultural, and recreational purposes.”

• Assessment: 

– Although specific targets for sanbars are not defined, each HFE has resulted 

in deposition demonstrating that the general objective of retaining and/or 

increasing sand volume above the 8000 cfs stage can be achieved when 

sand inputs occur and HFEs are implemented (2012-2018).

• Prognosis: 

– Deposition at sandbars is likely stage-limited (bars not likely to get larger 

without larger HFEs)

– Sandbar volume increased and maintained from 2011 to 2018 when dam 

releases were relatively low and sand inputs from Paria River average or 

above and HFEs were implemented. 

– Since 2019, sandbar volume has decreased for most bar types because 

monsoon failure (2019, 2020) and low reservoir levels (2021, 2022) 

prevented HFE implementation for 4 consecutive years.

Status: Significant concern because sandbars 

are eroding and not being rebuilt by HFEs.

Trend: decreasing because bars have eroded 

since last HFE in 2018

Confidence: high, because the monitoring is 

robust.

Preliminary results, subject to review, do not cite
Short update on Project B.2 

(Channel Mapping for Sandbar and Sand 

Storage Change)

• Mapped Lower Marble Canyon and Eastern 

Grand Canyon (60 river miles) in 2019

• Working on report that will provide a ~10-year 

status update on performance of HFE protocol 

by:

– Evaluating the effects of HFEs on more than 100 

sandbars throughout LMC and EGC (compared to the 20 

measured annually in this reach)

– Showing where sand eroded or deposited on the 

riverbed 

– Verifying the sand mass balance measured in Project A

• In April 2022, we completed the first channel 

mapping survey of RM 87 to RM 166, resulting in 

a complete basemap for all reaches from the 

dam to Diamond Creek

Mapped at least once

Mapped twice or more

Segment (river miles) Completed Maps

Glen Canyon (-15 to 0) 2014

Upper Marble Canyon (0 to 30) 2013, 2016

Lower Marble Canyon (30 to 61) 2009, 2012, 2019

Eastern Grand Canyon (61 to 87) 2011, 2014, 2019

East Central Grand Canyon (87 to 166) 2022

West Central Grand Canyon (166 to 225) 2017

Western Grand Canyon (225 to 280) *

* A 2-mile study reach has been mapped for project O.2. 
April 2022 Mapping of RM 

87 to 166

• 64 topographic surveys of sandbars

• 165 bathymetric surveys

• 18,677 measurements of bed grain 

size at 409 sample locations
Other Project B Activities

• Control network and survey support

• Water-surface and bed profile collected during 2021 

overflight (see upcoming talk by Shannon Sartain)

• Sandbar monitoring (see upcoming talk by Katie 

Chapman and poster by Bob Tusso)

• Sediment and sandbar modeling for HFE planning

• Work on new fine sediment model (see poster by 

Gerard Salter)

• Processing of “Columbine Reach” surveys (see poster 

by Matt Kaplinski)
U.S. Department of the Interior

U.S. Geological Survey

Evaluation of High-Flow Experiments 

During Aridification

Sandbar after November 2013 HFE (photo by M. Collier)

Lake Powell at 3526 ft in December 2022 (photo by P. Grams)

Glen Canyon Dam Adaptive Management Program

Annual Reporting Meeting

January 25, 2023

Paul Grams

U.S. Geological Survey

Southwest Biological Science Center

Grand Canyon Monitoring and Research Center
Hazel and others (2022)

Purpose of HFEs in LTEMP ROD

• The purpose of HFEs is to address the LTEMP 

sediment goal: 

– “Increase and retain fine sediment volume, area, 

and distribution in the Glen, Marble, and Grand 

Canyon reaches above the elevation of the 

average base flow for ecological, cultural, and 

recreational purposes.”

• The fine-sediment deposits (sandbars) erode 

by dam operations and other processes such 

as hillslope runoff from monsoon rains.

• HFEs are the only mechanism that has 

produced widespread re-distribution of 

sediment from the riverbed to the sandbars 

above base flow elevations.

Sand-enriched period 

with 7 HFEs (2004-2020)

Sand-depleted period 

with 1 HFE (1990-2003)

Entire period with 8 HFEs 

(1990-2020)

When implemented, HFEs have functioned 

as intended by the HFE Protocol and LTEMP 

EIS to address the LTEMP sediment goal

Hazel and others (2022)
Three Key Ingredients for Successful HFEs:

1. There is sufficient sand in the system to build sandbars without causing 

net erosion. 

– Addressed in HFE Protocol by using sediment model to design HFE.

2. Sand grain size is sufficiently fine to create conditions of high sand 

concentration in eddies. 

– Addressed in HFE Protocol by using sediment model to design HFE.

3. HFE magnitude is high enough to deposit sand at the high-elevation parts 

of sandbars and campsites. 

– Addressed in HFE Protocol by step-down approach to find the largest HFE that 

can be implemented for the available sand supply (consistent with 1 and 2, 

above).

These guidelines are embedded in the LTEMP ROD and are based 

on observations from first three HFEs (1996, 2004, and 2008) and 

verified by observations from recent HFEs (2012, 2013, 2014, 2016, 

and 2018)

https://ltempeis.anl.gov/

Eroded sandbar before HFE

HFE inundates sandbar

Sandbar following HFE
HFE magnitude, duration, and frequency all affect 

response and are not interchangeable

Hazel and others (2022), Wiele and others (1999)

Following the HFE Protocol to maximize magnitude 

first, then duration, and implement as frequently as 

conditions allow is the only way to test the LTEMP 

hypotheses and possibly achieve the LTEMP sediment 

goals.

• Magnitude has strongest control over deposition because it controls potential deposit size by inundating 

more area. We have very high confidence in this physical control on bar deposition based on observations 

and modeling results dating back to the 1996 HFE (Hazel and others, 2022)

– Low magnitude (~30,000 cfs) are much less effective than ~40,000 cfs, but still result in sandbar deposition.

• Duration is secondary to frequency, but also important because time is needed for sand concentrations to 

increase and for sand to be redistributed within eddies. Duration is hypothesized to control the number and 

distribution of sites that benefit (Wiele and others, 1999).

• Frequency is important because repeat HFEs are needed to rebuild the deposits that inevitably erode 

between HFEs (Hazel and others, 2022)

• What adjustments must be 

made to follow these guidelines 

under conditions of low runoff 

and low Lake Powell Elevations?
Predicted changes in sandbar volume as functions of HFE 

duration and Magnitude

48-hr HFE predicted to be about half as effective as a 

standard 96-hr HFE. 24-HFE about one-third as effective.

Preliminary model results. Do not cite.

*Predictions from Mueller and Grams (2021) sandbar model using obser

33,100 cfs HFE predicted to be about one-third as 

effective as 45,000 cfs HFE.

ved flow and sediment inputs through 9/14/2022.
 

Importance of HFE Frequency 

Model simulations reducing the number of HFEs Proportion of time sandbars 

are larger during HFE protocol. 

 

Fewer HFEs = reduced sandbar size Over the period of 

the protocol, 

sandbars are at least 

70% of maximum 

observed size for 80% 

of the time. 

Without protocol, sandbars are 

that large only 20% of the 

time. 

Mueller and Grams (2021) 
HFE Optimization 

“How do we optimize HFEs for the current low 

flow and low Lake Powell reservoir elevations 

and minimize the impacts to hydropower?”

HFE impacts:

• Bypass of hydroelectric turbines

– All HFEs require bypass

– These impacts were analyzed in LTEMP

– Impacts to hydropower could be reduced by ensuring that all 

hydropower units are available for any potential HFE 

implementation window. 

• Lake Powell Elevations

– HFEs do not impact annual release volumes or Lake Powell 

elevations on annual scale.

– HFEs may require reallocation of monthly release volumes, 

and therefore, may temporarily affect Lake Powell elevations

Impacts on Lake Powell elevations 

can be mitigated by changing the 

timing of HFE implementation.
LTEMP provides specific procedures for designing HFEs and specifies 

monthly flow volumes based on annual release volume

• October and November are the lowest volume months.

• LTEMP recognizes that water may need to be allocated from other 

months.

• But that can increase the risk of Lake Powell elevations becoming 

critically low in the winter months.

https://ltempeis.anl.gov/

Table in LTEMP does not include 

HFE volumes
 

 

LTEMP provides specific procedures for designing HFEs and specifies 

monthly flow volumes based on annual release volume 

• October and November are 

• LTEMP recognizes that wat

months.

• But that can increase the risk of Lake Powell elevations becoming

critically low in the winter months. 

https://ltempeis.anl.gov/ 

Table in LTEMP does not include 

HFE volumes 

 

 

 

thean lowd west e voldum

o

e

n

 m

’t kn onths.

ewin r may tneeer will bring? d to be allocated from other 

ow what the 

How do we reallocate 300k ac-ft of 

water to a 500k ac-ft month in the 

fall when Lake Powell is 

approaching minimum power pool 
November HFEs occur 

just before the period 

of year with lowest 

reservoir elevations

https://www.usbr.gov/uc/water/crsp/studies/index.html
LTEMP works to implement HFEs when annual volumes are 

“normal” and Lake Powell elevations are “non-critical”

• All but one of the HFEs have been implemented when annual volume was

8.6 maf or greater

– The 2014 HFE was implemented in a year with a 7.6 maf volume, but reservoir

levels were still above 3600 feet

• LTEMP HFE triggering makes fall HFEs more likely

– Although the LTEMP analysis predicted Spring HFEs would occur in about 5 out of

20 years, none have been triggered in the 10 years of the HFE protocol.

• But when Lake Powell is low, reallocation of water to the fall months has

been deemed too risky by the majority of the HFE Technical Team

•

•

In LTEMP, the HFE process was guided by the assumption that

sediment availability was the critical limiting factor in HFE

implementation: water availability was assumed.

For low-reservoir conditions, water availability is an

additional constraint to factor in the decision process.
Why have HFEs been 

implemented in Fall?

• Sediment concentrations and deposition

rates will be greatest when the sand supply in

the channel is greatest and is the finest grain

size

– These conditions are highest soon after a

series of tributary floods and then decrease

– If dam releases are relatively high during the

winter, there can be much less sand and 

coarser sand by spring

– But if dam releases are relatively low during

the winter, more of the fine sand will remain

available

– The HFE Protocol was designed to guard

against losing the sand over the winter but did

not include provisions for allowing use of the

sand if it persisted over the winter.

Paria and LCR 

average monthly 

sand loads used in 

HFE Protocol and 

LTEMP

Paria and LCR median monthly sand loads for 1998-2017 

(Topping et al., 2021)

https://ltempeis.anl.gov/

• Important when winter releases are high.

LTEMP sediment accounting optimizes to 

implement HFE as soon after Paria sediment 

inputs as possible.
Low-water HFE Protocol Step 1

• Revise the sediment accounting window to run a full 12 months, 

starting and ending July 1 every year. 

– This adjustment would allow HFE implementation when water availability is 

known (spring) using sediment from previous summer/fall

– This adjustment to the protocol is scientifically justified because low-water

conditions allow greater sediment retention over the winter than was anticipated 

for LTEMP flows above 8.2 million ac-ft.

– By limiting HFEs to one per sediment year, this would not increase the number of 

HFEs anticipated in the LTEMP ROD.

The LTEMP modeling analysis anticipated 15 fall HFEs and 

another 5 to 7 spring HFEs in the 20-year period. Six years 

into LTEMP, three fall HFEs and zero spring HFEs have been 

triggered and only one fall HFE implemented.
Revised sediment accounting periods

LTEMP sediment accounting optimizes to 

implement HFE as soon after Paria sediment 

inputs as possible.

• Important when winter releases are high.

Preliminary results, subject to review, do not cite

Low-water sediment accounting optimizes to 

implement HFE following accumulation of both 

Paria and LCR inputs.

• Will only work when winter releases are low.
Example mass 

balance for Upper 

Marble Canyon 

• Switch from “two-period” to 

“annual” sediment 

accounting when annual 

release volumes are less than 

8.2 maf (~11,300 cfs average 

flow) (Topping et al., 2021) 

i

 

 

LTEMP Accounting 

2015-2016 (Powell above 3600 ft) 

- ~ 800,000 metric tons accumulation 

- ~ 9 million acre-ft annual volume 

- Most sand eroded by following 

spring 

Important to implement HFE in 

fall before sand is exported. 

https://www.gcmrc.gov/d

 

Revised Accounting 

2021-2022 (Powell at and below 3550 ft) 

- ~ 1,400,000 metric tons accumulation 

- ~ 8 million acre-ft annual volume 

- Most sand retainied through 

following spring 

HFE could be implemented in either 

fall or spring because sand is retained 

scharge_qw_sediment/ 
Low-water HFE Protocol Step 2

Annual volume = 5 maf

~7000 cfs daily avg First 6 months at 

~5000 cfs daily avg

Second 6 months at 

~9000 cfs daily avg

Adding variability pretects Lake Powell 

elevations in winter and allows higher 

flows in spring/summer.

Preliminary results, subject to review, do not cite
Low-water HFE Protocol Step 2

Preliminary results, subject to review, do not cite

Annual volume = 5 maf

First 6 months at 

~5000 cfs daily avg

~8300 cfs daily avg with 

HFE in May or June

~7000 cfs daily avg

Second 6 months at 

Adding variability pretects Lake Powell 

elevations in winter and allows higher 

flows in spring/summer and HFE.
Low-water HFE Protocol Step 2

Preliminary results, subject to review, do not cite

5 maf variable pattern 

revised to 3.5 maf

~5000 cfs daily avg ~4000 cfs daily avg

~5000 cfs daily avg

5 maf variable pattern 

revised to 7 maf

Second 6 months at 

~8300 cfs daily avg with 

HFE in May or June
Conditions for potential Spring/Summer 2023 HFE

Current sediment 

conditions support 

a high flow of up to 

40,000 to 45,000 

cfs and up to 72 

hours anytime 

between fall 2022 

and summer 2023. 

Preliminary model results. Do not cite.

*Predictions from Mueller and Grams (2021) sandbar model using observed flow and sediment inputs through 9/14/2022.

* Includes Paria sand inputs through Sept. 14, 2022.

Predicted sandbar response to 

potential June 2023 HFE of

40,000 cfs for 72 hr

No HFE
Spring HFE for sediment consistent with spike flows for SMB control

2015 2016 2017 2018 2019 2020 2021 2022 2023

1800

2000

2200

2400

2600

2800

3000

3200

Bar volume (m 3

)

Sand bar volume (8000 ft 3 /s reference stage)

Percent change in sand bar volume 

 between June 7, 2023 and August 30, 2023 

 = 0.11 %

modeled

measured

Predicted sand mass balance and sandbar response for 

small mouth bass control options without flow spikes

Predicted sand mass balance and sandbar response for small 

mouth bass control with 72-hr 40,000 ft3/s flow spike.

*Predictions from Mueller and Grams (2021) sandbar model using observed flow and sediment inputs through 9/14/2022.

Preliminary model results. Do not cite.

2015 2016 2017 2018 2019 2020 2021 2022 2023

1800

2000

2200

2400

2600

2800

3000

3200

Bar volume (m 3

)

Sand bar volume (8000 ft 3 /s reference stage)

Percent change in sand bar volume 

 between June 7, 2023 and August 30, 2023 

 = 51.10 %

modeled

measured
Conclusions: HFEs under conditions of low flows and low 

reservoir elevations

• LTEMP ROD intended frequent HFEs for sediment goals.

• HFEs are not being implemented because sediment triggering criteria is incompatible 

with need to prevent Lake Powell storage from “bottoming out” in late winter.

• Two-part solution:

– Adjust sediment accounting window to allow sediment-triggered HFEs in spring/summer

– Plan distribution of monthly volumes such that water is available for HFE regardless of annual 

volume.

• Resource benefits

– Sediment enriched HFEs for sandbar building

– Spring high flows for other resources (e.g. small mouth bass control)

– Highest monthly volumes (relatively) in summer for recreation and power generation

– Maximum protection for Lake Powell elevations
References

• 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, https://doi.org/10.3133/pp1873

• Mueller, E.R., and Grams, P.E., 2021, A morphodynamic model to evaluate long-term sandbar rebuilding 

using controlled floods in the Grand Canyon: Geophysical Research Letters, v. 48, no. 9, e2021GL093007, 

https://doi.org/10.1029/2021GL093007.

• Wiele, S.M., Andrews, E.D., and Griffin, E.R., 1999, The effect of sand concentration on depositional rate, 

magnitude, and location in the Colorado River below the Little Colorado River, in Webb, R.H., Schmidt, 

J.C., Marzolf, G.R., and Valdez, R.A., eds., The controlled flood in Grand Canyon: Washington, D.C., 

American Geophysical Union, Geophysical Monograph Series, v. 110, p. 131–145.

• Wright, S.A., Topping, D.J., Rubin, D.M., and Melis, T.S., 2010, An approach for modeling sediment budgets 

in supply-limited rivers: Water Resources Research, v. 46, p. 1–18, doi:10.1029/2009WR008600.

• U.S. Department of the Interior, 2016, Record of Decision for the Glen Canyon Dam Long-Term 

Experimental and Management Plan Final Environmental Impact Statement, https://ltempeis.anl.gov/