Angler surveys

Food base (invertebrates, macrophytes)

Sediment dynamics

Aeolian studies

Vegetation

Nutrient dynamics

Spring Disturbance Flow Update

2022 Annual Reporting Meeting

Ted Kennedy1, Bridget Deemer1, Dave Lytle2, Paul Grams1, Joel Sankey

Brad Butterfield3, Kim Dibble1, Bob Tusso1, Lucas Bair1

1-US Geological Survey, Southwest Biological Science Center-Grand Canyon Monitoring and Research Cen

2-Oregon State University, 3-Northern Arizona University

Trout habitat use

1

, 

ter, 

Sandbars
OUTLINE

• Introduction-me (4 slides)

• Nutrients-Deemer (11 slides)

• Invertebrates-Lytle (5 slides)

• Sediment-Grams (13 slides)

• Aeolian-Sankey (11 slides)

• Terrestrial Vegetation-Butterfield (9 slides)

• Aquatic Vegetation-Dibble (8 slides)

• Trout-Dibble (9 slides)

• Angling surveys-Bair (6 slides)

• Sandbars-Tusso (11 slides)

• Wrap up and next steps (4 slides)
Problem Statement

• Disturbance is essential natural process in rivers

– maintains biological diversity

– native species life cycles often tuned to disturbance

– high flows only tool for rebuilding sandbars

• Disturbance was historically most common in spring/early 

summer

Natural Flows-1937

Lees Ferry

Conceptual Model Preliminary results 

subject to review and revision
Problem Statement

• HFE Protocol favors fall HFEs

• Good for sandbars

• But role of spring HFE in achieving LTEMP goals remains unclear

Most recent spring HFE was 2008

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019

2020 2021 2022 2023 2024 2025 2026 2027 2028 2029

•

• Many biology projects didn’t exist in 2008 LEGEND___

Spring HFE

Spring Disturbance Flow

Fall HFE

Sediment trigger,

but no fall HFE

Preliminary results 

subject to review and revision
March 2021-Spring Disturbance Flow

• Apron repair is 

unique opportunity

– 5 days of 4,000 cfs

needed for dam 

maintenance

– low flow = 

disturbance

• Combine with pulse 

flow

– potential synergistic 

effect

– low + pulse >> 

low or pulse alone 

apron repair

pulse flow

LEES FERRY

https://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09380000
U.S. Department of the Interior

U.S. Geological Survey

Nutrient Dynamics During the Spring 

Disturbance Flow

GCDAMP Annual Reporting Meeting

January 12, 2022

Bridget Deemer- bdeemer@usgs.gov
U.S. Department of the Interior

U.S. Geological Survey

People

Ted Kennedy- funding support from Project O

Bob Hall & Adam Baumann- laboratory analysis

Freshwaters Illustrated- photography

Ann-Marie Bringhurst & Clay Nelson- logistics

Tom Sabol Charles Yackulic
U.S. Department of the Interior

U.S. Geological Survey

Hypothesis

 A high flow immediately following a low flow will result in 

a large pulse of nutrients to the water column.

 Three mechanisms:

 elevated sediment nutrient mineralization in dessicated zone

 scouring of benthic algae and associated macroinvertebrates

 elevated suspended sediment and associated nutrients
U.S. Department of the Interior

U.S. Geological Survey

March 21, 2021- Low Flow- Grand Canyon March 24, 2021- High Flow

March 16, 2021- Low Flow- Glen Canyon March 22, 2021- High Flow- Glen Canyon

Methods

Two Sites: 

Glen Canyon (RM -2)

Grand Canyon (RM 225)

Three sediment subsites: 

Temporarily exposed (mainstem)

Temporarily exposed (backwater)

Temporarily inundated

5 time points: 

pre-experiment

day 2 low

day 5 low

high water

return to base
U.S. Department of the Interior

U.S. Geological Survey

Sampling Design

Triplicate water 

sampling

Rhizon porewater 

samples Sediment Cores
U.S. Department of the Interior

U.S. Geological Survey

Results: Turbidity

Increased turbidity during high flow

Preliminary results 

subject to review and revision
U.S. Department of the Interior

U.S. Geological Survey

Results: Porewater

No evidence for mineralization 

in sediment porewater matrix 

(so far)

Preliminary results 

subject to review and revision
U.S. Department of the Interior

U.S. Geological Survey

Results: River Chemistry

Huge bump in total 

phosphorus at Diamond Creek 

can be explained by silt and 

clay concentrations

0.08 TP 

@ 100 

mg/L Fines

Preliminary results 

subject to review and revision
U.S. Department of the Interior

U.S. Geological Survey

Results: River Chemistry

Elevated ammonium 

levels in the river 

suggest that in-stream 

mineralization is 

releasing nutrients

Preliminary results 

subject to review and revision
U.S. Department of the Interior

U.S. Geological Survey

Hypotheses Regarding Future Disturbance Flows

2021 Spring disturbance flow

Similar disturbance effect. 

Results thus far suggest 

similar nutrient mobilization 

would occur even without the 

4000 cfs steady-low

Best disturbance flow for 

nutrients/gpp could be a high 

flow followed by a longer 

steady-low flow

Preliminary results 

subject to review and revision

s

1

10

100

1000

10000

Nutrient dynamics and GPP 100000

0 5 10 15 20 25 30

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

1

10

100

1000

10000

0 5 10 20 25 30

No steady-low 

flow before 

high flow

Longer steady-low 

after disturbance may 

promote GPP, 

especially if timed 

during optimal AprilJune timeframe

River Discharge

Tim15e
Aquatic invertebrate community 

models - low flow parameters

David A. Lytle and Angelika Kurthen

Oregon State University

Goals:

- Develop population models for Grand 

Canyon food base species (amphipods, 

NZMS, midges, blackfies, mayflies, etc.)

- Link population dynamics to flow event 

types (high, low, hydropeaking) and 

environmental conditions (seasonal 

temperatures, food availability)
Green River, Utah. Low flow events and spring 

floods were once a major characteristic of the 

Colorado River ecosystem (Lytle & Poff, Trends in 

Ecol. & Evol.)

Natural flow regime paradigm:

Organisms evolved in the context of seasonal 

floods and low flows

Spring floods and fall low flow events nearly 

absent from system for 50+ years

Question: what role do flow events play in 

supporting food base species? (blackflies, 

chironomid midges, mayflies, caddisflies; also 

Gammarus, NZ mudsnails, quagga mussels)
Population models for food base communities

1. Construct matrix population models for each relevant species

2. Parameterize with vital rates according to major event types: mortality and growth 

rates in response to floods, low flows, hydropeaking, etc.

3. Use model to ask “what if” questions about future flow scenarios
March 2021 Low flow sampling

Goal: Estimate maximum loss rate (LRmax)of 

individuals due to stranding

Paired Design: Sample stranded and still-submerged 

cobble beds

Three locations: 

RM -14 (Below Glen Canyon dam), n=10

RM -3.5 (Above Lees Ferry), n=20

RM 226 (Diamond Creek), n=10

Methods:

1. Benthic core sampler

2. Sediments and algal mats removed and washed 

3x by hand

3. Sediments collected to 5 cm deep, elutriated 10x 

4. Preserved in 95% ethanol in field

5. Physiochemical data: Temp, pH, substrate 

(Wolman walk), dissolved O2

Quagga Mussels in 

exposed algal mats at 

RM -14
Expected outcomes

Samples: In process (URSA Engage student Connor Eck), 

will finish by mid-May.

Dominant taxa: 

RM -14 and RM -3.5: Mostly quagga, NZMS, Gammarus

RM 226: caddisflies (Hydropsyche)

Hypotheses:

- Higher LRmax for Gammarus, quagga, caddisflies

- Likely an overestimate for NZMS (operculum)

Next steps:

- Add parameters to population models

- In a future low flow experiment, measure actual loss 

rates over time
Sediment Dynamics in Western Grand 

Canyon During 2021 Spring Disturbance Flow

GCDAMP Annual Reporting Meeting

January 12, 2022

U.S. Department of the Interior

U.S. Geological Survey

Paul Grams

U.S. Geological Survey

Grand Canyon Monitoring and Research Center
Acknowledgements Project O.2 personnel:

Matt Kaplinski, Katie Chapman, and Vincent Diaz

Northern Arizona University

Paul Grams, Keith Kohl, and Robert Tusso

U.S. Geological Survey

Grand Canyon Monitoring and Research Center

Corey Sannes

U.S. Geological Survey

Arizona Water Science Center
Project O.2 in the Columbine Study Reach in Western Grand 

Canyon

• Objective: Understand and quantify 

relation between changes in bed 

configuration in Western Grand Canyon 

and dam releases. Do certain dam 

operations reduce, exacerbate or mitigate 

sediment accumulation in this reach?

• Measurements conducted during 2021 

pulse flow: Mapping of bed and banks in 

2-mile study reach before during and 

after pulse flow (will map again in 

August).
Columbine Study Reach in Western Grand Canyon

View of study reach from outside of bend at RM 273.6R

RM 273.6
Temporary gage to measure water-surface elevation and 

travel-time between Diamond Creek and study reach

Pearce Ferry Rapid

Pearce Ferry Boat Ramp

Columbine Study Reach

Preliminary results, subject to review, do not cite
Project O.2: Field surveys around 2021 Spring Pulse Flow

March 10: Survey 1

March 26: Survey 2

April 22: Survey 4

March 28: Survey 3

Sept. 15: Survey 5

https://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09380000
Field Surveys

• Sonar survey of riverbed

• Boat-based lidar survey of 

banks

• Ground-based RTK-GPS 

survey of water surface 

and check points

• Time-lapse cameras to 

show bars during low-flow 

and bank erosion 

Multibeam bathymetry in channel

Lidar along banks

Preliminary results, subject to review, do not cite
Columbine Reach Bed erosion and deposition

March 10 to March 26

(pre-pulse to during pulse)

During pulse:

• Lots of dune movement.

• Two concentrated zones of deposition

• Two concentrated zones of erosion

Zones of erosion

Zones of 

deposition

Preliminary results, subject to review, do not cite

• Alternating red and yellow show dune

movement.

• Dark red areas of sediment accumulation.

• Blue-green are areas of sediment erosion.
Columbine Reach Bed erosion and deposition

March 10 to March 28

(pre-pulse to post-pulse)

Zones of erosion

Zones of 

deposition

Preliminary results, subject to review, do not cite
Columbine Reach Bed erosion and deposition

March 10 to April 22

(pre-pulse to late Spring)

• Alternating red and yellow show dune 

movement. 

• Dark red areas of sediment accumulation.

• Blue-green are areas of sediment erosion.

Deposition 

in pool Cumulative changes:

• Dune movement averaged out.

• One concentrated zone of deposition

• Large areas of slight erosion

Preliminary results, subject to review, do not cite
Columbine Reach Bed erosion and deposition

March 10 to Sept. 15

(pre-pulse to late Summer)

• Alternating red and yellow show dune 

movement. 

• Dark red areas of sediment accumulation.

• Blue-green are areas of sediment erosion.

Cumulative changes:

• Dune movement averaged out.

• One concentrated zone of deposition

• Large areas of slight erosion

Deposition 

in pool

Preliminary results, subject to review, do not cite
Conclusions

• As expected, the reach is dynamic

• Preliminary analysis of the repeat 

surveys:

– Bars in the reach were active and aggraded 

slightly during the disturbance flow

– Pools in the reach scoured during the 

disturbance flow

– Following summer operations, bars eroded 

slightly and pools filled

• Repeat with different/higher flow pulse 

would be informative

Proposed FY2022/23 Activities

• Complete analysis of changes in Columbine 

study reach.

• Develop sediment budget for Western Grand 

Canyon based on transport measurements (CR 

at Diamond Creek) and estimates of sediment 

input from banks.

• Develop and calibrate numerical flow model for 

study reach.

• Use model to predict response to different dam 

operations.

• Prepare draft report to be finalized in FY2023.

Preliminary results, subject to review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

Project Element O.3. Aeolian 

Response to a Spring Pulse Flow 

Joel B. Sankey, Joshua Caster, Helen Fairley

U.S. Geological Survey, GCMRC

Annual Reporting Meeting, January 12, 2022
Project Element O.3. Aeolian Response to a Spring 

Pulse Flow 

https://www.usgs.gov/centers/sbsc/science/timing-reallyeverything-evaluating-resource-response-spring-disturbanceflows?

er 

s 

• Focused on the five-day drop in riv

flow (“low steady flow”) during the 

2021 SDF 

• Discharge from the upstream Glen

Canyon Dam dropped to 122 m3/s

(4,300 cfs), approximately 104 m3/

(3,700 cfs) lower than the regularly

occurring contemporary base-flow

discharge of the river
O.3 Fluvial-aeolian experiment in the Colorado 

River in Grand Canyon

• Experimental five-day drop in river flow exposed 

~ 26,154 m2 of sand per kilometer of Colorado 

River in Grand Canyon (Kasprak et al., 2021)

• >100% increase in source area of potential 

windblown sediment supply for 57 aeolian 

dunefields and 60 additional areas of unvegetated 

high-elevation sand that contain archaeological 

sites along Colorado River in Grand Canyon 

National Park (Sankey et al., 2018)

Figure from: Kasprak et al., 2021, "Future regulated flows of the Colorado River 

in Grand Canyon foretell decreased areal extent of sediment and increases in 

riparian vegetation." Environmental Research Letters 16.1 (2021): 014029.
O.3 Fluvial-aeolian experiment: Methods

• Study area was a 18,000 m2 sandbar and adjacent 

dunefield at Lees Ferry on the Colorado River

• Used portable in-situ wind erosion lab (PI-SWERL) 

to measure the threshold friction velocities (U*t) for 

sand saltation. U*t is the wind velocity required to 

initiate aeolian sediment transport 

• Collected measurements on the sandbar during 

each day of the low river flow experiment. 

PI-SWERL
O.3 Fluvial-aeolian experiment: Methods

• Measured particle size distribution, gravimetric 

and volumetric water content at the sample 

locations. 

• Surveyed the elevation, topography, and 

surface roughness of the sample locations using 

ground-based lidar remote sensing.

• Modelled instantaneous aeolian sediment fluxes 

(q; kg/m/s) using measured u*t, wind data, 

following Bagnold (1941)

Caster and others, 2014

USGS on-site weather station

Reigl vz 1000 Terrestrial Lidar

Near surface sediment sample

collection
O.3 Fluvial-aeolian experiment: Questions

• Quantify the variability in U*t as a function of time since inundation 

by the river, sediment water content, grain size, topographic 

position, and surface roughness.

• How the does the magnitude of wind velocity required to initiate 

aeolian sediment transport change with time since inundation by 

river water on the sandbar?

• How does that compare on the adjacent downwind aeolian 

dunefield that was not recently inundated by the river?
O.3 Fluvial-aeolian experiment: Results

• Wind velocity required to initiate aeolian 

sediment transport (U*t) decreased as 

time since inundation increased

• By third day of steady low river flow, U*t 

on the river sandbar was statistically 

similar to adjacent sand dune that hadn’t 

been previously inundated by river

Preliminary results, subject to review, do not cite
O.3 Fluvial-aeolian experiment: Results

• Modelled aeolian sediment flux was 

significantly greater on the dry sand 

dune on Days 1 and 2, but differences 

with modelled sandbar flux decreased 

with exposure time.

• 3 days after river flow dropped, modeled 

sandbar flux ≈ modeled sand dune flux.

• Under typical spring wind conditions, the 

cumulative sandbar flux could be greater 

than half that of weekly cumulative flux 

for the dry sand dune.

Preliminary results, subject to review, do not cite
O.3 Fluvial-aeolian experiment: Results

Multi-model comparison of predictors for u*t

Z Score/ Importance

Significance

Preliminary results, subject to review, do not cite

• Changes in measured U*t over the 

experiment were significantly influenced

by subaerial exposure time, moisture,

and surface roughness
O.3 Fluvial-aeolian experiment: Conclusions

• Confirmed that by drastically lowering flows and allowing sand to dry out, can potentially greatly 

increase the amount of sand transported to inland to dunes and archeological sites

• Low-steady flow of SDF exposed ~ 26,154 m2 of sand per kilometer of the river; >100% increase source area of aeolian sediment supply 

• When river flow dropped and river sand was exposed to the wind, some damp sand could be blown out 

of the river sandbar towards dunefield during the first 48 hours of drying, but was fully susceptible to the wind’s energy after 72 hours of drying

• Predicted u*t (wind velocity required to initiate aeolian sediment transport) on river sandbar as a 

function of subaerial exposure time, moisture, surface roughness, grain size, elevation above water surface

• Modelled aeolian sediment transport on river sandbar as a function of wind and changes in u*t owing to 

subaerial drying time

• Can model aeolian sediment transport on river sandbars for different hydrograph scenarios

• Manage river flows to promote aeolian landscape habitat and support in-situ preservation of archaeological sites in Grand Canyon by optimizing the timing and duration of periods of low flows 

(that might become increasingly relevant in light of drought-mitigation needs).

Preliminary results, subject to review, do not cite
O.3 Hypotheses Regarding Future Disturbance Flows

2021 Spring Disturbance Flow

Better disturbance flow to increase 

aeolian sand transport from sandbars 

to dunefields for preservation of 

archaeological sites and cultural 

resources?

Best disturbance flow to increase 

aeolian sand transport from sandbars 

to dunefields for preservation of 

archaeological sites and cultural 

resources?

River Discharge

Time

Larger 

sediment

-rich 

flood to 

rebuild 

sandbars

Longer low-steady 

flow during the windy, 

dry months April-June 

to increase aeolian 

transport on sandbars 

Preliminary results, subject to review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

Short-term Physiological 

Responses of Two Plant 

Species to the 2021 SDF

Brad Butterfield1 and Emily Palmquist2

1 Department of Biological Sciences, Northern Arizona University

2 Grand Canyon Monitoring and Research Center, Southwest Biological 

Science Center, USGS, Flagstaff
Did Plants Respond to the SDF?
Arrowweed:

Drought-tolerant, 

native shrub
Schedonorus arundinaceae

Tall fescue:

Water-loving, 

non-native grass
Daily Physiological 

Measurements

 Stem water potential

 Tension of the water column 

within a plant stem (more 

negative = more stressed)

 Stomatal conductance to 

water vapor

 Gas exchange with the 

atmosphere (lower = more 

stressed)

 Leaf relative water content

 Leaf hydration (lower = more 

stressed)

USGS/Freshwaters Illustrated
Results: Both Species 

Responded to SDF

 Stem water potential 

responded positively to 

discharge

 Tall fescue responded 

stronger to dry-down

 Arrowweed responded 

stronger to the wet-up

Preliminary results, subject to review, do not cite
Results: Both Species 

Responded to SDF

 Stem water potential 

responded positively to 

discharge

 Tall fescue responded 

stronger to dry-down

 Arrowweed responded 

stronger to the wet-up

 Leaf relative water content 

responded positively to 

discharge

Preliminary results, subject to review, do not cite
Results: Both Species 

Responded to SDF

 Stem water potential responded 

positively to discharge

 Tall fescue responded stronger to 

dry-down

 Arrowweed responded stronger to the wet-up

 Leaf relative water content 

responded positively to discharge

 Caveat: Weather did not 

cooperate

 Though in multiple regression 

models, discharge remained significant while temperature was 

not 

Preliminary results, subject to review, do not cite
Conclusions

 Stem water potential appeared to be the most sensitive 

response to flow variation

 The water-loving grass (tall fescue) appeared to respond most strongly to the dry-down, reflecting its dependence on consistent soil moisture

 The drought-tolerant shrub (arrowweed) appeared to respond most strongly to the wet-up, reflecting its ability to capitalize on enhanced soil moisture that feeds up the soil profile through 

capillary action

 Not entirely capable of teasing apart flow and weather effects

 Most species were not photosynthetically active at this time of 

year, so were unlikely to be affected by the SDF

Preliminary results, subject to review, do not cite
Aquatic vegetation in Glen Canyon: Observations 

following a Spring Disturbance Flow

Kimberly Dibble, Mike Yard, Bob Tusso, Dan Buscombe

(with contributions from Ted Kennedy and Jeff Muehlbauer)

GCDAMP Annual Reporting Meeting

January 12, 2022

U.S. Department of the Interior

U.S. Geological Survey

Freshwaters Illustrated, 2021
Project O.5: How will the pulse flow affect aquatic vegetation?

Background

https://www.usgs.gov/centers/sbsc/science/timing-reallyeverything-evaluating-resource-response-spring-disturbanceFreshwaters Illustrated, 2021 flows?

 Prolonged desiccation followed by an increase in sheer stress 

will export organic matter and aquatic vegetation from LF

 Scour and cleaning of cobble will facilitate re-growth of diatom 

assemblages that are more palatable to invertebrate 

consumers, which may stimulate higher trophic levels

 Hypothesis: The SDF will have a greater effect on 

macroalgal species at the littoral edge such as 

Chara, Cladophora, and Ulothrix, while rooted 

macrophytes (Potamogeton) and bryophytes 

(Fontinalis spp.) located deeper in the water 

column will be less affected by the flow.
Project O.5: Methods

 Field surveys

 Photos taken in August 2016 

and June 2019 (Element E.2)

 2021 SDF trips  Pre-flow: March 9-11

 Post-Flow: March 29-31, July 21-22

 48,084 total images

 Upper site (RM -13.2 to -14.2) and lower site (RM-3.0 to -4.2)

 Overlaps with TRGD 1A & 1C

 Model development

 Label images to train model 

(Dibble & Yard)

 Create a machine learning 

model for image segmentation of vegetation and substrate 

types (Buscombe)

 Use model to create vegetation 

maps

Preliminary results, subject to review, do not cite
Project O.5: Predicted desiccation at various flows 

Lower Site

J. Korman, unpub. maps

Upper Site

Preliminary results, subject to review, do not cite
J. Korman, unpub. maps

Preliminary results, subject to review, do not cite

Project O.5: Observations at lower site
J. Korman, unpub. maps

Preliminary results, subject to review, do not cite

Project O.5: Observations at upper site
Project O.1: Organic matter transport resulting from SDF

Kennedy and Muehlbauer, unpub. data, do not cite

Preliminary results, subject to review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

Future Disturbance Flows

s

1

10

100

1000

10000

100000

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2021 Spring disturbance flow

Potential future disturbance: 

low flow remains the same to 

desiccate nearshore habitat, 

but high flow is higher to 

disturb rooted macrophytes 1

10

100

1000

10000

100000

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River Discharge

Macrophytes

Preliminary results, subject to review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

GCDAMP Annual Reporting Meeting

January 12, 2022

Freshwaters Illustrated, 2021 Freshwaters Illustrated, 2021

Freshwaters Illustrated, 2021

Nearshore habitat use and distribution 

of age-0 trout in Spring 2021

Kimberly Dibble, Laura Tennant, and Clay Nelson

(with collaborators Mike Yard and Josh Korman) 
Project O.6: How will the pulse flow affect juvenile brown trout?

Background

 Peak brown trout emergence occurs in March  Warmer temperatures= ~March 1

 Cooler temperatures= ~March 15

 SDF timing will likely affect the vulnerability of recently 

hatched or newly emerged brown trout

Korman and Yard, unpublished data, do not cite

Warmer fall & 

average winter

Water Temperature 

2020-2021

Preliminary results, subject to review, do not cite

 Hypothesis: A low steady flow during peak emergence may temporarily improve swim-up and growth conditions for YOY trout, but the 

pulse will decrease survival due to energetic 

costs or displacement from nearshore habitats

 Objective: Determine the effect of the SDF on 

hatch date, emergence timing, habitat use, 

survival, and relative abundance
Project O.6: Methods

 Brown Trout Early Life Stage Survey 

(BTELSS, Element H.3)

 Field surveys

 RTELSS design (comparable data)

 January-May (7 trips, 2021 & 2022)

 40 sites, spatially distributed

 Talus (high angle); cobble bars, sand 

bars, debris fans (low angle)

 Laboratory work

 Hatch & emergence dates (otoliths)

 Growth rates

 Compare data to year lacking Spring 

Disturbance Flow (2022)

Field Surveys

Laboratory Work

Otoliths (“ear bones”)

Daily Growth Increments on Otolith

Sunday Low Steady Flows, 2003

Korman and Campana 2009
Project O.6: Results (size structure)

Species Key

Jan-May

2021

Field Identification Challenges

 Spawning periods overlap for brown and 

rainbow trout

 Larval fish difficult to identify in field

 Adipose fins may have characteristics of both 

species

 Issue will resolve in spring 2022

 ‘Unknown’ is YOY brown or rainbow trout (for 

now...)

Species Key

Jan

2022

Preliminary results, subject to review, do not cite
Project O.6: Results

Age-0 trout distribution and catch rates

Map Key

Site location

Size of circle 

indicates CPUE

YOY trout utilize low and high angle 

habitats throughout Lees Ferry

Relatively consistent catch rates except 

downstream from -4 mile bar

Map Key

Low angle site

Size of circle 

indicates CPUE

High angle site

Preliminary results, subject to review, do not cite
Project O.6: Results

Age-1 trout distribution and catch rates

Map Key

Low angle site

Size of circle 

indicates CPUE

High angle site

Preliminary results, subject to review, do not cite

Brown trout primarily use high angle (talus) habitats 

and are spatially distributed throughout Lees Ferry. 

Catch is higher near TRGD reaches 1A and 1C.

Rainbow trout have higher catch rates than brown 

trout and are mostly captured in talus habitats.

Map Key

Low angle site

Size of circle 

indicates CPUE

High angle site
Project O.6: Results

Age-0 trout catch by trip and habitat use

YOY catch in low angle sites steadily increases from Feb-April. 

Large increase in YOY in May in both low/high angle sites could 

be RBT, consistent with RTELSS data. 

The SDF does not appear to have affected YOY trout catch, but 

more analysis and clarity is needed on species identification.

PreFlowPostFlow

PreFlowPostFlow Freshwaters Illustrated, 2021

Freshwaters Illustrated, 2021

Preliminary results, subject to review, do not cite
Project O.6: Results

Age-1 trout catch by trip and habitat use

Brown & rainbow trout catch is consistent in low angle habitats. 

Brown & rainbow trout catch declines in talus from January-May. This 

may indicate movement offshore into deeper habitats or mortality.

The pre- and post-flow difference may be part of a natural declining 

trend in talus habitat use, but data from a non-SDF year is needed.

PreFlow

PostFlow

PreFlow

PostFreshwaters Illustrated, 2021 Flow

Preliminary results, subject to review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

Future Disturbance Flows

s

1

10

100

1000

10000

100000

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2021 Spring disturbance flow

Potential future disturbance: 

low flow is earlier and high 

flow is slightly higher, timed 

during peak emergence

Time

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

River Discharge

Trout

Preliminary results, subject 

to review, do not cite
Lees Ferry angler's expectations and 

response to the Spring Disturbance Flow

Lucas Bair, U.S. Geological Survey

Chris Neher, University of Montana

GCDAMP Annual Reporting Meeting

January 12, 2022

U.S. Department of the Interior

U.S. Geological Survey

U.S Department of Interior

U.S. Geological Survey
Project Element O.8. Do Disturbance Flows 

Significantly Impact Recreational Experience?

 The objective of this project 

element is to refine our 

understanding of recreational 

preferences for flow attributes 

specific to spring disturbance 

flows. 

 Focused on the five-day steady

low flow (4,000 cfs) during the 

disturbance event. 
Project Element O.8: Background

17%

57%

9%

15%

35%

20%

68%

8%

71%

0%

20%

40%

60%

80%

100%

3,000 cfs 10,000 cfs 25,000 cfs

Constant flow in cfs

Constant flow preferences in 2015 survey*

Worse

Similar

Better

*10,800 cfs average 

experienced by anglers

0

50

100

150

200

250

300

350

400

450

3,000 cfs 10,000 cfs 25,000 cfs 40,000 cfs

Estimated willingness to pay per trip ($2015)

Bishop et al. 1987 Neher et al. 2016 (CV) Meldrum In Prep (CE)

Preliminary results, subject to review, do not cite
Project Element O.8: Methods

 Angler choice 

experiment survey

 Modified creel survey 

that respondents 

completed and returned 

by mail

 150 survey forms were 

distributed

 79 completed for an 

overall response rate of 

52.7%

Preliminary results, subject to review, do not cite
Project Element O.8: Results

20%

50%

19%

36%

29%

9%

43%

21%

72%

0%

20%

40%

60%

80%

100%

3,000 10,000 25,000

Constant flow in cfs

Constant flow preferences in SDF survey*

WORSE

SIMILAR

BETTER

*4,000 cfs average 

experienced by anglers

0

100

200

300

400

500

600

3,000 cfs 10,000 cfs 25,000 cfs 40,000 cfs

Estimated WTP per Trip ($2015)

Bishop et al. 1987 Neher et al. 2016 (CV) Meldrum In Prep (CE) Spring Disturbance

Preliminary results, subject to review, do not cite
Hypotheses Regarding Future Disturbance Flows

U.S. Department of the Interior

U.S. Geological Survey

s

2021 Spring 

Disturbance Flow

The best disturbance flow 

for recreational angling 

(in the short run) is no 

disturbance at all.

Steady moderate flows (~10,000 cfs) are 

the preferred flow of anglers in general.

U.S Department of Interior

U.S. Geological Survey

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

River Discharge

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

River Discharge

Time

Recreational angling

Preliminary results, subject to 

review, do not cite
U.S. Department of the Interior

U.S. Geological Survey

Effects of the March 2021 

Disturbance Flow on 

subaerial sandbars

GCDAMP 

Annual Reporting Meeting

January 12, 2022

Robert Tusso

GCMRC
U.S. Department of the Interior

U.S. Geological Survey

GCMRC 

Remote Camera 

Project

- 44 cameras 

- 5 images daily

- Lower quantitative precision than 

terrestrial surveys

- Better temporal precision/resolution
2018 High Flow Experiment

Major Gain

RM 66.1 L

Nov. 10, 2018

RM 66.1 L

Nov. 1, 2018

U.S. Department of the Interior

U.S. Geological Survey
2018 High Flow Experiment

Major Loss

U.S. Department of the Interior

U.S. Geological Survey

RM 55.9 R

Nov. 1, 2018

RM 55.9 R

Nov. 10, 2018
2018 High Flow Experiment

Sandbar Metrics

U.S. Department of the Interior

U.S. Geological Survey Preliminary results, subject to review, do not cite.

66% of sites 

increased 

in size
U.S. Department of the Interior

U.S. Geological Survey

2012-2018 High Flow Experiments

Sandbar Metrics

Preliminary results, subject to review, do not cite.
2021 Disturbance Flow

Minor Gain

U.S. Department of the Interior

U.S. Geological Survey

RM 194.6 L

Mar. 13, 2021

RM 194.6 L

Mar. 31, 2021
2021 Disturbance Flow

Minor Loss

U.S. Department of the Interior

U.S. Geological Survey

RM 123.3 L

Mar. 13, 2021

RM 123.3 L

Mar. 31, 2021
2021 Disturbance Flow

Sandbar Metrics

U.S. Department of the Interior

U.S. Geological Survey Preliminary results, subject to review, do not cite.

74% of sites 

remained the 

same size
U.S. Department of the Interior

U.S. Geological Survey Preliminary results, subject to review, do not cite.

Increase in 

size is the 

predominant 

HFE outcome

No change in 

size is the 

predominant 

SDF outcome
U.S. Department of the Interior

U.S. Geological Survey

Conclusions

• 74% of sites underwent “Negligible Change” vs 20-40% in typical HFE

• 0% of sites underwent “Major Change” vs 15-20% in typical HFE

• Magnitude of beach change was minimal compared to typical HFE’s

• Of changed beaches, 14% underwent “Gain” and 12% underwent “Loss”

• A Typical HFE has 51-66% undergo “Gain” and 9-12% undergo “Loss”

• Sign of beach change was neither overwhelmingly positive or negative

Preliminary results, subject to review, do not cite.
U.S. Department of the Interior

U.S. Geological Survey

Synthesis of the Spring 

Disturbance Flow

Where do we go from here?

GCDAMP 

Annual Reporting Meeting

January 12, 2022

Lucas Bair 

GCMRC
Synthesis of the Spring Disturbance Flow

 The purpose of Project O is to 

evaluate whether a springtimed disturbance flow will 

improve resources in the 

Colorado River Ecosystem. 

 Project O will test the 

hypothesis that disturbance of 

benthic (river bottom) habitats 

in spring enhances the LTEMP 

resources goals such as the 

goal of Natural Processes (i.e., 

food base) of the Colorado 

River.
Synthesis of the SDF: preliminary results

Nutrients

Invertebrates

Sediment

Aeolian

Terrestrial Vegetation

Aquatic Vegetation

Trout

Angling surveys

Sandbars
Synthesis of the SDF: hydrograph results

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

1

10

100

1000

10000

0 5 10 15 20 25 30

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

1

10

100

1000

10000

100000

0 5 10 15 20 25 30

• Nutrients and Aeolian

• Recreational angling

• Aquatic vegetation

• Trout

River Discharge

River Discharge

River DischargeRiver Discharge

Time

Time Time

Time

Preliminary results, subject to review, do not cite.
Synthesis of the SDF: looking forward

 Objective: what do we want to 

accomplish and why? 

 Hydrograph design

 Hypothesized resource response

 Direction and magnitude

 Tradeoff analysis: is there an opportunity to 

achieve multiple objectives?

 Uncertainties that impede management

 Multiple future scenarios 

Tonkin, Jonathan D., Julian D. Olden, David M. Merritt, Lindsay V. Reynolds, Jane S. Rogosch, 

and David A. Lytle. "Designing flow regimes to support entire river ecosystems." Frontiers in 

Ecology and the Environment 19, no. 6 (2021): 326-333.
U.S. Department of the Interior

U.S. Geological Survey

Angler surveys

Food base (invertebrates, macrophytes)

Sediment dynamics

Aeolian studies

Vegetation

Nutrient dynamics

Trout habitat use

Sandbars

Freshwaters Illustrated, 2021