Dissolved Oxygen Dynamics in 

Lake Powell and Glen Canyon 

Bridget Deemer, Tom Sabol, Caitlin Andrews, Robin Reibold, Charles Yackulic 

U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon 

Monitoring and Research Center 

Glen Canyon Dam Adaptive Management Program 

Annual Reporting Meeting 

January 24, 2024 

Photo Credit. David Herasimtschuk, 

©Freshwaters Illustrated 

Escalante arm of Lake Powell 

Campsite for Lake Powell quarterly trip- March 9, 2022 

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 liable for any damages resulting from the authorized or unauthorized use of the information. 
 

 

 

 

Project E TWP Accomplishments 

Bug flows increase 

canyon-wide gross 

primary production 

(GPP) especially when 

bed grain size 

distribution is coarse 

Modified from Deemer et al. 

2022 PNAS Nexus 

GPP positively influences 

Flannelmouth Sucker growth 

& modeling efforts are 

underway to explore the role 

of GPP in Humpback Chub 

growth (see Lindsay Hansens’ 

poster!) 

High GPP 

Low GPP 

Modified from Hansen et al. 

2023 CJFAS 

Method improvement 

for estimating 

tailwater metabolism 

will support food web 

inferences in Glen 

Canyon (see Ian 

Bishop’s poster!) 

Preliminary Data, Do Not 

Cite 

2 
 

 

 

 

 

 

 

Project E TWP Accomplishments 

High Flow Events 

(HFEs) and Bug Flows 

do not affect Rainbow 

Trout growth as much 

as water quality from 

reservoir releases 

Modified from Korman et al. 

2022 CJFAS 

Reservoir phosphorus 

release drove declines in 

prey production and collapse 

of Rainbow Trout fishery in 

Glen Canyon (Yard et al. 

2023 TAFS) 

Modified from Yard et al. 

2023 TAFS 

Declining pH from both 

storms and reservoir 

elevation can elevate 

bioavailable phosphorus 

in the Colorado River 

below Glen Canyon Dam 

Modified from Deemer et al. 

2023 Biogeochemistry 

3 
 

 

 

 

 

 

Why Do We Care About Low 

Dissolved Oxygen (DO)? 

• Generally considered a key metric of water quality 

• In the River: Biodiversity 

• Some species are more sensitive to low DO than others 

• In lakes and reservoirs, fish habitat can be “pinched” where fish 

will intentionally avoid low oxygen regions 

Diagram demonstrating how fish breathe dissolved oxygen 

Modified from schematic by Lindsay Lafreniere Carp gasping for oxygen: 

4 Photo by Laszlo Balogh 
 

 

Why Do We Care About Low DO? 

• Generally considered a key metric of water quality 

• In Reservoirs: 

• Drinking water quality and mercury dynamics 

• Can enhance nutrient availability and shift nutrient limitation 

leading to algal blooms 

• Fish habitat can be “pinched” where fish will intentionally avoid 

low oxygen regions 

5 
Danger Zone 

2009-2021 

2023 

2022 

Preliminary 

Information - 

Subject to 

Revision. 

Not for 

Citation or 

Distribution 6 
-

 

How Low is Low? 

The low oxygen in dam releases this year was unprecedented in both magnitude and duration 

2005 

2022 

2023 

Preliminary 

Information 

Subject to 

Revision. 

Not for 

Citation or 

Distribution 7 
- 

 

 

 

How Low is Low? 

The low oxygen in dam releases this year was unprecedented in both magnitude and duration 

Red lines show the median: 

1. LC-50 for invertebrates: concentration that is lethal to 50% of test population w/ 96+ 

hr acute exposure (Saari et al. 2018) 

2. EC-50 for cold water fishes: concentration that has a 50% effect on growth or 

reproductive effect w/ 96+ hr chronic exposure (Saari et al. 2018) 

Chronic Invertebrate LC-50 

Cold Water Fishes EC-50 

Preliminary Information Subject to Revision. Not for Citation or Distribution 
- 

More Persistent Low DO Events 

Below Glen Canyon Dam 

9 

Preliminary Information Subject to Revision. Not for Citation or Distribution 
 

Dynamic Deltas in Powell’s Inflows 

Have Impacts Far Downstream 

• ~7% loss in reservoir storage capacity 

10 Krolczyk and Schmidt 2023- Sediment Delivery to Lake Powell and Lake Mead Factsheet 
 

 

Spring Inflows Remobilize 

Sediment and Create DO Demand 

Metalimnion 

September 19, 2022 

2.9 Million Acre Feet Inflow 

September 11, 2023 

7.5 Million Acre Feet Inflow 

Preliminary Information- Subject to Revision. 11 

Not for Citation or Distribution 
 

 

 

Incubation Experiment 

(funded by Ecosystems Mission Area) 

Oxygen consumption rate 

depends on water temperature 

and sediment source 

Larger temperature response in 

the Colorado than the San Juan 

Highest rates of consumption in 

the monsoonal Chinle Creek 

sediments, but no temperature 

dependence (likely because rate 

is saturated) 

12 

Preliminary 

InformationSubject to 

Revision. Not for 

Citation or 

Distribution 
 

 

Incubation Experiment 

(funded by Ecosystems Mission Area) 

Phosphorus release measured in 

all incubations 

Modified from Deemer et al. 

2023 Biogeochemistry 

13 

Preliminary 

InformationSubject to 

Revision. Not for 

Citation or 

Distribution 
 

 

 

 

What Can The 

Historical 

Dataset Tell 

Us? 

Lower average late 

summer/fall dissolved 

oxygen in the metalimnion 

when: 

1. Reservoir spring 

elevation is low 

2. Spring inflow is large 

3. Age/elevation 

interaction 

Lake-wide low dissolved 

oxygen events will be 

increasingly common when 

lake elevation is below 

~3620 ft. 

3526ft 

3628ft 

3530ft 

3572ft 

3602ft 

3704ft 

Preliminary Information- Subject to Revision. 14 

Not for Citation or Distribution 
 

 

Low Dissolved Oxygen Will Have 

Largest Impact on Trout Near Dam 

2022 

Daily average 

DO ~1 mg/L 

higher at Lees 

Ferry than at 

Dam 

Oxygen fully 

mixed by 

rapids 

downstream 

Preliminary Information- Subject to Revision. Not for Citation or Distribution 
 

DO Departure Largest During Day 

Preliminary Information- Subject to Revision. Not for Citation or Distribution 
- 

How spatially variable is DO? 

17 

Glen Canyon Dam 

(~RM-15.8) 

Lees Ferry 

(RM 0) 

Water Holes 

MiniDOTs (~RM-4) 

Honey Draw 

MiniDOTs (~RM-13) 

Preliminary Information Subject to Revision. 

Not for Citation or Distribution 
- 

 

Side Channel Habitats vs. 

Main Channel 

>1 mg/L 

departures in 

DO between 

main channel 

and 

macrophyte 

beds 

18 

Chronic Invertebrate LC-50 

Coldwater Fishes EC-10 

Preliminary Information Subject to Revision. 

Not for Citation or Distribution 
 

Acknowledgements 

• Eric Frye 

• Morgan Ford 

• Bryce Mihalevich 

• Josh Korman 

• Sasha Reed 

• Funding from the GCDAMP, the Bureau of 

Reclamation and the USGS Ecosystems Mission 

Area 

19 
Questions? 

20 
 

 

 

 

 

 

 

 

What does this mean for the 

Glen Canyon Tailwater? 

Adapted from Saari et al. 2018 

Red box shows where we are 

already below published 

literature median toxicity 

values 

LC50- concentration that is 

lethal to 50% of test 

population w/ 96 hr acute 

exposure 

EC10- concentration that has 

a 10% effect on growth or 

reproductive effect w/ 96+ 

hours chronic exposure 

21