The FLAHG 

Hydrograph 

Ted Kennedy 

14 October 2020

Grand Canyon Monitoring and Research Center

Southwest Biological Science Center

U.S. Geological Survey

U.S. Department of the Interior

Preliminary results subject to review and revision
Outline

 Background (5 slides)

 FLAHG hydrograph (3 slides)

 Knowledge Assessment (14 slides)

 Contingencies, conclusions (5 slides)
Spring floods = healthy ecosystems

“...the apparent nationwide importance of high flows in spring 

(March, April, May) also indicates that the timing...of high flows 

is critical.”

Daren Carlisle, June 2020 TWG Presentation
Regular Testing of Fall HFEs

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

Fall HFE Spring HFE

Preliminary results subject to review and revision
Some benefits of regular Fall HFE testing

Reduced critical 

uncertainties

for HFE  sediment

Sandbar resource improved

2012

2020

Preliminary results subject to review and revision
Why so few Spring HFEs?

 They were prohibited

• 2011 HFE EA initially prohibited

• 2016 LTEMP extended thru 2019

 Why prohibit Spring HFE?

• Study HFE → sandbar w/o creating RBT at LCR

• Key finding from 2008 spring HFE

 Prohibitions were superfluous 

• Spring sediment trigger not reached in 8 years

 See Grams and Topping, June 2020 TWG presentation

Preliminary results subject to review and revision
A Path Forward

FLow Ad Hoc Group (FLAHG) formed in 2019

“As a starting point, the FLAHG shall 

consider the benefits of and opportunities 

for conducting higher spring releases 

within power plant capacity” –FLAHG charge
Proposed FLAHG hydrograph

 Spring disturbance flow (March proposed)

 Apron repair is unique opportunity

• 5 days at 4,000 ft3/s for dam maintenance

• Low flows = disturbance

 Combine with spring pulse flow disturbance

• low + pulse >> low OR pulse alone

Preliminary results subject to review and revision
Why March?

 Keep it simple...

• Prior Spring HFEs (‘96 & ’08) were in March

• Favorable natural process response documented

• Simplifies comparison of FLAHG & HFE data

• Avoids commercial motor season in April

Down the road....Could explore April, May, or June disturbance flows

But for right now (FLAHG hydrograph) March makes a ton of sense. 

Preliminary results subject to review and revision
Desiccation & scour potential

Low Flow = Desiccation

In a nutshell

Large area change between 4,000 and 8,000 cubic 

feet per second (cfs)

-Change in area = metric of drying potential

Cobble hotspots:

27% of habitat exposed to drying

Reach wide:

12% of habitat exposed

Fun fact: Flow of 4000 cfs last occurred in early 90s

Pulse Flow = Scour

In a nutshell

Shear stress = shearing force of water on bed

-Direct measure of scour potential

Cobble hotspots:

~5% increase in scour at 20,000 vs. 25,000 cfs

Reach wide: ~13% increase in scour

Fun fact: Since ‘96, flows of 20,000 cfs or greater have 

occurred just ~7% of the time. 

Cobble hot spots

• Average: -27%

• Range: -16 to -36%

Cobble hot spots

• Average: +5%

• Range: +1 to +7%

90th percentile

Range of possible

Spring Pulse Flow

Preliminary results subject to review and revision; pers comm Scott Wright
Why a Knowledge Assessment?

 Stakeholder requested

 Forces communication among scientists

• Must work in groups, think deeper, get in weeds

 Facilitates communication with stakeholders

• Translate science with easy-to-understand symbols

 Rubric updated in 2017 & 2019

• Clear definitions and guidance for scoring

• Relatively quick and easy to conduct

Preliminary results subject to review and revision
Knowledge Assessment Teams

 Cultural & Archaeological: Peter Bungart, Jen Dierker, Jakob Maase, Joel Sankey

 Natural Process: Ted Kennedy, Jeff Muehlbauer, Bridget Deemer, Jess Gwinn, Larry 

Stevens

 Humpback chub: Charles Yackulic, Kirk Young, Mike Yard, Maria Dzul

 Hydropower & Energy: Craig Ellsworth, Leslie James, Lucas Bair

 Other Native Fish: Brian Healy, Melissa Trammel, Bob Schelly, Charles Yackulic, 

Mark McKinstry

 Recreational Experience: Lucas Bair, Kim Dibble, Jim Strogen, David Brown, Leslie 

James, Craig Ellsworth, David Rogowski

 Sediment: Paul Grams, David Topping, Lucas Bair, Matt Kaplinski, Joe Hazel, David 

Brown, Ben Reeder

 Tribal Resources: Peter Bungart, Jakob Maase

 Rainbow Trout Fishery: Kim Dibble, Charles Yackulic, Mike Yard

 Nonnative Invasive Species: David Ward, David Rogowski

 Riparian Vegetation: Emily Palmquist, Brad Butterfield, Barb Ralston, Larry Stevens

33 participants from 12 different agencies:

US Geological Survey, National Park Service, Hualapai Dept. of Cultural Resources, US 

Fish and Wildlife Service, Grand Canyon Wildlands Council, Western Area Power 

Administration, Colorado River Energy Distributors Association, Bureau of Reclamation, 

Federation of Fly Fishers, Grand Canyon River Guides, Arizona Game and Fish Dept. 

Northern Arizona University
Specific Measures = bookends

 Cultural & Archaeological: 5 measures

 Natural Process: 4 measures

 Humpback chub: 1 measure

 Hydropower & Energy: 5 measures

 Other Native Fish: 2 measures

 Recreational Experience: 7 measures

 Sediment: 3 measures

 Tribal Resources: 1 measure

 Rainbow Trout Fishery: 2 measures

 Nonnative Invasive Species: 2 measures

 Riparian Vegetation: NA

Example: Rainbow Trout Fishery

1) RBT at Lees Ferry

2) RBT at LCR

Use as bookends

Lowest 

performing 

measure

Highest

performing

measure

Preliminary results subject to review and revision
Knowledge Assessment

 Used rubric from 2019

 Evaluated 3 management actions

• Spring disturbance flow (FLAHG hydrograph)

• Spring HFE

• Fall HFE

FLAHG hydrograph Spring HFE Fall HFE

Preliminary results subject to review and revision
Old KA Symbols

Not intuitive

what colors

mean

Distaste for

arrows

Not intuitive what 

outline means

Distaste for

term

‘confidence’

Hard to visualize 

data, see patterns

Preliminary results subject to review and revision
New KA Symbols

Goals of Redesign: 

1) Make symbols more intuitive, 

2) Improve data visualization (i.e., quickly compare +/- of actions)

Dumbbell Size = 

Weight of evidence

Y-axis = strength

Direction Unknown

Strength Unknown

No Effect

Decreasing Increasing

Stronger

Effects

Stronger

Effects

Preliminary results subject to review and revision
Lowest Performing Measure

Appears to 

be relatively 

low risk

Preliminary results 

subject to review and 

revision
Potential Decreases identified in KA

 Hydropower & Energy

• Small decrease in ‘load following capability’ predicted

 Other Native Fish

• Razorback spawning period, eggs may dry at 5d low flow

 Recreational Experience

• Crowding and navigation risk during low flow

 Sediment

• Small decrease in ‘total sand volume’ predicted

 Nonnative Invasive Species

• Pierce Ferry may be barrier, low flow may allow greater 

movement

Preliminary results 

subject to review and 

revision
Highest Performing Measure (1)

Because 

sometimes

‘No Effect’

is a Win

Preliminary results 

subject to review and 

revision
No Effects identified in KA

 Hydropower and Energy

• Electric generation not affected, no bypass, shoulder month

 Other Native Fish

• No effect predicted, outside of spawning window for FMS/BHS

 Sediment

• Volume of deposition/erosion small, bc pulse flow small

 Nonnative Invasive Species

• Unknown effects, low confidence

Preliminary results 

subject to review and 

revision
Highest Performing Measure (2)

Some 

intriguing

potential

upsides

Preliminary results 

subject to review and 

revision
Potential Increases identified in KA

 Cultural and Archaeological Resources

• Potential increase in available sand for aeolian transport

 Natural Processes

• Potential increase in production & diversity of algae and insects

 Humpback chub

• Potential indirect effect on HBC via food base

 Tribal Resources

• Potential increase in ecosystem health

 Rainbow Trout Fishery

• Potential indirect effects on RBT via food base, spawning

 Nonnative Invasive Species

• Spring disturbance disfavors Brown Trout

Preliminary results 

subject to review and 

revision
Spring timing does not align with 

brown trout spawning calendar

Fall HFE

Spring HFE

From Dibble et al. 2015, Ecological Applications.

Preliminary results subject to review and revision
FLAHG Hydrograph

Essential Context

 Provides ‘contrast’ to last 5 fall HFEs

• Key biology projects are poised to study

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

2009-Juvenile chub monitoring (JCM) starts

2010-Gross primary production monitoring starts

2012-Citizen science insect monitoring starts

Fall HFE

Spring HFE

Preliminary results subject to review and revision
FLAHG hydrograph will reduce uncertainties

In particular, critical uncertainties for fish and aquatics will be 

reduced if FLAHG hydrograph tested and Project O funded. 

Critical Uncertainties

Few Many

Preliminary results 

subject to review and 

revision
What about Bug Flows?

 Complementary? Yes

• Bug Flows: Egg stage

• FLAHG flow: Larval stage

 Complicating? Yes

• Will make data analysis harder

 Confounding? No

• Effects can be disentangled

26

Bug Flows

 Sine wave pattern

 Grand Canyon focus

FLAHG flow

 Insect, NZ mudsnail count

 Lees Ferry focus

No (scientific) issues with 

FLAHG flow + Bug Flows in 2021

Preliminary results 

subject to review and 

revision
FLAHG hydrograph

qualitative narratives

 Tribal Resources 

• Spring timing aligns with 

Father Earth’s calendar 

 Natural Processes

• Spring timing aligns with 

Mother Nature’s calendar

 Recreational Experience

• Spring timing aligns with 

human calendar

Preliminary results 

subject to review and 

revision
Contributors

 USGS/GCMRC- Ted Kennedy, Lucas Bair, Bridget Deemer, 

Kimberly Dibble, Helen Fairley, Paul Grams, Jeff Muehlbauer, 

Emily Palmquist, Joel Sankey, Dave Topping, David Ward, 

Charles Yackulic, Mike Yard; 

 USGS/CAWSC-Scott Wright

 Hualapai Department of Cultural Resources-Peter Bungart

 Western Area Power Administration-Craig Ellsworth

 Northern Arizona University-Brad Butterfield

 National Park Service-Brian Healy

 Grand Canyon Wildlands Council-Larry Stevens

 Colorado River Commission of Nevada-Peggy Roefer
Questions?

Preliminary results subject to review and revision