Potential Experiments and 

Management Actions

Clarence Fullard and Mike Moran

TWG Meeting

April 13-14, 2021
Objectives

•Introduce “menu” of LTEMP experiments for 

consideration in the next 12 months.

•Discussion of Process: Planning and 

Implementation Team status for spring 2021 

considerations.

•Tee up GCMRC for more detailed discussion of 

these items.
Potential LTEMP Flow Experiments 

FY2021

GCD Experimental Flow Duration Implementation 

Window

Fall HFE up to 96 hours October - November

Extended Duration Fall HFE 97- 192* or 97-250 hours*** October - November

Spring HFE∆ up to 96 hours March – April

Proactive Spring HFE∆◊ 24 hours** April – June

Trout Management Flows up to 3 cycles/month for 4 months May – August

Macroinvertebrate Flows target 2-3 replicates May – August

* First test not to exceed 192 hours

** First test 24 hours

*** After first test, up to 250 hours

∆ no Spring HFE in same WY as extended duration Fall HFE

◊ no proactive Spring HFE in same WY as sediment-driven Spring HFE

Other FY2021 Flows :

• Apron Repair + Spring Disturbance Flow (March) 

• Releases for Overflight (steady 8,000 cfs for 7 days in May) 
Potential LTEMP Flow Experiments 

FY2022

GCD Experimental Flow Duration Implementation 

Window

Fall HFE up to 96 hours October - November

Extended Duration Fall HFE 97- 192* or 97-250 hours*** October - November

Spring HFE∆ up to 96 hours March – April

Proactive Spring HFE∆◊ 24 hours** April – June

Trout Management Flows up to 3 cycles/month for 4 months May – August

Macroinvertebrate Flows target 2-3 replicates May – August

* First test not to exceed 192 hours

** First test 24 hours

*** After first test, up to 250 hours

∆ no Spring HFE in same WY as extended duration Fall HFE

◊ no proactive Spring HFE in same WY as sediment-driven Spring HFE
High Flow Experiment Timeline

Spring HFE, sediment triggered

• Sediment accounting: Dec 1 – June 30

• Implementation / Planning Team decision: late February

• Possible implementation: March-April

Spring HFE, proactive

• Equalization (GCD releases >= 10 maf)

• Planning Team: late February

• Possible implementation: April-June

Fall HFEs, sediment triggered

• Sediment accounting: July 1 – Nov 30

• Implementation / Planning Team: early September

• Possible implementation: October – November 
HFE Accounting & 

Implementation Windows
Trout Management Flows

TMFs are a special type of fluctuating flow designed 

to reduce the recruitment of trout by disadvantaging 

YOY trout

FIGURE 6 Example 

Implementation of a TwoCycle TMF in June and July 

with Resumption of 

Normal Fluctuations 

between Cycles and 

Afterward (Monitoring for 

effectiveness would occur 

before and after each 

cycle. The horizontal line 

below the graph shows 

periods of normal 

fluctuation [blue] and 

TMFs [orange].) 
Spring Disturbance Flow

• Hydrograph characteristics:

• The spring disturbance flow began with a reduction in flows to 4,000 

cubic feet per second starting on March 15 at 5 a.m., reaching 4,000 

cubic feet per second at 7:00 a.m. GCMRC will provide prelim results 

later.
Macroinvertebrate Flows

“Bug Flows” Objective: Improve food base 

productivity and abundance or diversity of 

mayflies, stoneflies, and caddisflies

• “Give bugs the weekends 

off”

• Weekend stable low flows 

from May-August

• Eggs laid on week-ends

never dry

• Tech Team 2021 considered 

a 4th year.
Bug Flows Year 4- Tech Team Update

•Planning and Implementation (PI) Team Calls: 5

• Q&A document created to address uncertainties.

• Basin Fund status heavily considered.

• Considered 4 potential hydrograph alternatives.

•No consensus recommendation for bug flows in 

2021. 

• PI Team voted to not implement in 2021.

• Next steps: 

• Summary memo for Leadership Team and DOI.

• WAPA -> more info on purchase power cost estimates

• Science Advisors panel to evaluate Bug Flows exp.

• GCMRC will synthesize Bug Flows results. 10
Summary and Budget 

Considerations

•Spring LTEMP flow experiments and flow actions for 

FY21 are set. Experimental funds FY21 are expended.

• No spring or fall HFEs in FY21 

• Bug Flows not recommended in FY21 

• Completed Spring Disturbance Flow in FY21 

• Remote Sensing Overflight – Memorial Day Wknd FY21 

• Fall ’21 / Spring ‘22 LTEMP Experiments: 

• Fall HFE accounting period begins: July 1

• Spring HFE accounting period begins: December 1
Paria River Discharge & Sand Inputs

12

USGS Preliminary Data, 2021. Do Not Cite. 

(https://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09382000# )

Dec 1, 2020 – Apr 7, 2021

Cumulative Sand Load = 14,000
Upper Marble Canyon Sand Mass Balance

13

USGS Preliminary Data, 2021. Do Not Cite. 

(https://www.gcmrc.gov/discharge_qw_sediment/reach/GCDAMP/09380000/09383050#)

Dec 1, 2020 – Mar 31, 2021

Zero Bias Value = -110,000
Lower Marble Canyon Sand Mass Balance

14

USGS Preliminary Data, 2021. Do Not Cite. 

(https://www.gcmrc.gov/discharge_qw_sediment/reach/GCDAMP/09383050/09383100#)

Dec 1, 2020 – Mar 31, 2021

Zero Bias Value = 58,000
2021 Remote Sensing Overflight

What?

 Orthorectified four-band (visible and 

near-infrared) imagery with 20 cm pixel 

resolution

 Digital elevation model with a 1-meter 

pixel size

Where?

 Glen Canyon Dam to Pearce Ferry Rapid
2021 Remote Sensing Overflight 

 Steady 8,000 ft3/s GCD Release

 Starts 6 pm Friday May 28, 2021

 Stops 4 am morning Friday June 4, 2021

 Gives contractor 8 days of flying to 

acquire data

 Flights commence on Saturday May 29th 

 ~10 am to 2 pm each day 

 minimizes shadows

 Start at GCD, move downstream with 8k flow 

 Inclement weather may require extending 

daily flight window and/or duration of 

mission

Clarence Fullard

303-253-1042

cfullard@usbr.gov