Temperature Control 

and Fish Passage at 

Glen Canyon Dam –

Recent Progress

GCDAMP Technical Working Group

Clarence Fullard

June 16-17, 2021
2016 LTEMP Biological Opinion

•Temperature Control Device:

• Reclamation would explore the efficacy of a temperature 

control device at the dam to respond to potential extremes 

in hydrological conditions due to climate conditions that 

could result in nonnative fish establishment. Evaluations 

would be ongoing for all current and evolving 

technological advances that could provide for warming and 

cooling the river in both high- and low-flow discharge 

scenarios, and high and low reservoir levels. These studies 

should include evaluating and pursuing new technologies, 

an analysis of the feasibility, and a risk assessment and cost 

analysis for any potential solutions.
Review: Dam Impacts on River 

Temperature 

•High Reservoir, COLD water impacts

• Low Reservoir, WARM water Impacts
Temp. Control Studies to Date 

• 1978: BO concern for fish populations and aquatic resources from cold 

dam releases (USFWS 1978).

• 1995: BO directed BOR to “...implement a selective withdrawal program 

for Lake Powell waters...” (USFWS 1995).

• 1997: Value Planning Study identified five design proposals costing $15 

to $148.5 million (BOR 1997).

• 1997: Feasibility Study recommends uncontrolled surface withdrawal 

(fixed inlet) design as preferred alternative

• 1999: Draft Science Plan (GCMRC 1999) and Draft EA for a TCD on Glen 

Canyon Dam (BOR 1999)—withdrawn.

• 1999: Scientific Review of EA expressed concern for unintended negative 

effects, esp. NNF (Mueller et al. 1999).
Temp. Control Studies to Date 

• 2001: BOR workshop of scientists and managers evaluated feasibility of a 

TCD (BOR 2001).

• 2003: AMWG requested Survey of Selective Withdrawal Systems 

(Vermeyen et al, 2003)

• 2003: GCDAMP Science Advisors recommended construction of a pilot 

TCD (Garrett et al. 2003).

• 2004 – 2006: Prolonged drought drives a second round of feasibility 

studies. An external frame selective withdrawal structure selected due to 

most operational range (180 vertical feet).

• 2006: Draft EA for a TCD on Glen Canyon Dam (BOR 2006)—preempted 

by LTEP.

• 2006-2007: Value Engineering Study, Constructability Review, Final 

Design completed.

• 2018:Temperature modeling to determine release temperatures using hal

f, full bypass and without bypass at three reservoir elevations (TWG 

presentation)
Recent TCD Exploration

• Reclamation R&D Office report reviewing temp control 

options for reservoir release flows in January 2020.

• A technology search was recommended as a next step.

• In March 2020, Reclamation developed a Technology Search 

to explore innovative TCDs.

• Contractor (Yet2) provided a report with a multitude of 

ideas.

• Reviewed at April TWG meeting.

• Discussed w/ Reclamation GCD staff.

• Reclamation is still shopping the results around internally.
Remaining Questions

•Can we refine the problem statement?

• Advantage native fish... or disadvantage non-native 

fish? 

• Timing: Most critical time of year? 

• Temps: Desired / catastrophic temperature ranges.

• Location: Specific reach of the river? 

• Risk: 

• Most likely future conditions – reservoir levels? 

 At what critical times of year do we need what 

temperatures in what reach of the river?

 At what critical times of the year to we need to avoid what 

catastrophic temperatures in what reach of the river?
2016 LTEMP Biological Opinion 

• Fish Passage:

• Reclamation would pursue means of preventing the 

passage of deleterious invasive nonnative fish through Glen 

Canyon Dam. Because Glen Canyon Dam release 

temperatures are expected to be warmer under low 

reservoir elevations that may occur through the LTEMP 

period, options to hinder expansion of warmwater 

nonnative fishes into Glen and Grand Canyons would be 

evaluated. Potential options to minimize or eliminate 

passage through the turbine or bypass intakes, or minimize 

survival of nonnative fish that pass through the dam would 

be assessed (flows, provide cold water, other). While 

feasible options may not currently exist, technology may be 

developed during the LTEMP period that could help 

achieve this goal.
Fish Passage

•2007 – 2009 GCD forebay fish survey report.

•Improved Fish Exclusion Prize Competition –

Reclamation – 2019.

•Reclamation partnered with DOE Water-Power 

Technologies Office to launch a prize competition 

to evaluate fish passage – 2019 to 2020.

•September 2020: winners were selected at the 

virtual AFS meeting, awarded lab space to 

prototype at DOE lab TBD.

•Internal discussions to look for obvious 

technologies applicable to GCD took place – no low 

hanging fruit.
Questions?
Downstream Temperatures Using 

No Bypass, Half Bypass and Full 

Bypass