SEIS Bypass Releases - Revision history

Cellsworth at 21:15, 18 August 2026

2026-08-18T21:15:07Z

Cellsworth at 21:00, 18 August 2026

2026-08-18T21:00:51Z

Cellsworth at 20:56, 18 August 2026

2026-08-18T20:56:43Z

Cellsworth at 20:54, 18 August 2026

2026-08-18T20:54:18Z

Cellsworth at 20:33, 18 August 2026

2026-08-18T20:33:11Z

Cellsworth at 20:31, 18 August 2026

2026-08-18T20:31:54Z

Cellsworth at 18:00, 18 August 2026

2026-08-18T18:00:05Z

Cellsworth at 17:54, 18 August 2026

2026-08-18T17:54:18Z

Cellsworth at 17:47, 18 August 2026

2026-08-18T17:47:29Z

Cellsworth at 14:18, 18 August 2026

2026-08-18T14:18:00Z

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-Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment (see the Pine et al. 2025 - Yackulic et al. 2026 discussion on the [https://gcdamp.com/index.php/Smallmouth_Bass_Page Smallmouth Bass Page]), continued entrainment of juvenile and adult smallmouth bass and the availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
+Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment (see the Pine et al. 2025 - Yackulic et al. 2026 discussion on the [https://gcdamp.com/index.php/Smallmouth_Bass_Page Smallmouth Bass Page]), continued entrainment of juvenile and adult smallmouth bass and the availability of spawning and nursery habitat like the Dam Slough at -15 mile poses similar risks to humpback chub as allowing warmwater releases from Glen Canyon Dam.
 ===[https://gcdamp.com/index.php/Entrainment Entrainment]===

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 |style="color:#000;"|
-Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment, continued entrainment of juvenile and adult smallmouth bass and the availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
+Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment (see the Pine et al. 2025 - Yackulic et al. 2026 discussion on the [https://gcdamp.com/index.php/Smallmouth_Bass_Page Smallmouth Bass Page]), continued entrainment of juvenile and adult smallmouth bass and the availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
 ===[https://gcdamp.com/index.php/Entrainment Entrainment]===

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 ===Downstream movement of smallmouth bass ===
-[https://warnercnr.colostate.edu/wp-content/uploads/sites/2/2017/04/LFL-154-Hawkins_et_al-2009-Rpt.pdf Hawkins et al. (2009)] found that smallmouth bass in the Yampa River moved long distances both upstream and downstream within short timeframes. This high mobility contributes to rapid basin-wide dispersal and complicates nonnative predator suppression efforts aimed at protecting native endangered fish.
+[https://warnercnr.colostate.edu/wp-content/uploads/sites/2/2017/04/LFL-154-Hawkins_et_al-2009-Rpt.pdf Hawkins et al. (2009)] found that smallmouth bass in the Yampa River moved long distances both upstream and downstream within short timeframes. They found this high mobility contributes to rapid basin-wide dispersal and complicates nonnative predator suppression efforts aimed at protecting native endangered fish.
-−
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-! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Deficiencies of Cool Mix</h2>
+! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Areas where Cool Mix does not work</h2>
 |-
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-Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment, continued entrainment of juvenile and adult smallmouth bass and availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
+Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment, continued entrainment of juvenile and adult smallmouth bass and the availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
 ===[https://gcdamp.com/index.php/Entrainment Entrainment]===
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 ===[https://gcdamp.com/index.php/The_-12_Mile_Slough Water temperatures in backwaters and sloughs]===
-The Rapid Response Tech Team reported on 4/22/26 that bluegill and green sunfish had recently spawned in the Dam Slough at river mile -15. Minimum spawning temperatures for bluegill and green sunfish are 17 C and 19 C, respectively. Releases from Glen Canyon Dam during this period were between 10 and 11 C showing that solar heating of this isolated slough allowed these warmwater nonnative fish to spawn in the tailwater. This shows the ineffectiveness of Cool Mix at cooling backwaters and sloughs that are isolated from the river and the need of modifying these habitats in order to keep them from becoming source areas for invasive fish.
+The Rapid Response Tech Team reported on 4/22/26 that bluegill and green sunfish had recently spawned in the Dam Slough at river mile -15. Minimum spawning temperatures for bluegill and green sunfish are 17 C and 19 C, respectively. Releases from Glen Canyon Dam during this period were between 10 and 11 C. This shows the ineffectiveness of Cool Mix at cooling spawning and nursery habitats that are exposed to solar heating and isolated from the river and the need to modify these habitats in order to keep them from becoming source areas for invasive fish.
 ===Downstream movement of smallmouth bass ===

@@ Line 337: / Line 337: @@
 |style="color:#000;"|
-Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment, continued entrainment of juvenile and adult smallmouth bass and availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam. [https://coloradoriverrecovery.org/uc/wp-content/uploads/sites/2/2022/02/TechnicalReport-NNA-Breton-2015-161b.pdf Breton et al. (2015)] found that eliminating entrainment from source reservoirs was the only way to reduce smallmouth bass populations to zero in Little Yampa Canyon.
+Cool Mix does not prevent entrainment of smallmouth bass through Glen Canyon Dam and it does not cool spawning and nursery habitats that are disconnected from the mainstem (e.g. the Dam Slough at -15 mile). Fish can and will migrate from the tailwater downstream into Grand Canyon and into areas where temperature control at Glen Canyon Dam cannot reach. If habitat in Grand Canyon is in fact suitable for smallmouth bass establishment, continued entrainment of juvenile and adult smallmouth bass and availability of spawning and nursery habitat like the Dam Slough at -15 mile poses the same risk to humpback chub as allowing warmwater releases from Glen Canyon Dam.
 ===[https://gcdamp.com/index.php/Entrainment Entrainment]===
-[https://gcdamp.com/images_gcdamp_com/d/d4/Eppehimer_etal_2025_Declining_res_elevations_non-native_fish_passage_CJFAS.pdf Eppehimer et al. (2025)] found that maintaining Lake Powell elevations above 3590 ft (1094 m) would likely minimize propagule pressure from the reservoir and create downstream conditions that minimize smallmouth bass population growth. Smallmouth bass propagule pressure increases dramatically as reservoir elevation declines below 3530 ft (1076 m).
+[https://gcdamp.com/images_gcdamp_com/d/d4/Eppehimer_etal_2025_Declining_res_elevations_non-native_fish_passage_CJFAS.pdf Eppehimer et al. (2025)] found that maintaining Lake Powell elevations above 3590 ft (1094 m) would likely minimize propagule pressure from the reservoir and create downstream conditions that minimize smallmouth bass population growth. Smallmouth bass propagule pressure increases dramatically as reservoir elevation declines below 3530 ft (1076 m). [https://coloradoriverrecovery.org/uc/wp-content/uploads/sites/2/2022/02/TechnicalReport-NNA-Breton-2015-161b.pdf Breton et al. (2015)] found that eliminating entrainment from source reservoirs was the only way to reduce smallmouth bass populations to zero in Little Yampa Canyon.
 ===[https://gcdamp.com/index.php/The_-12_Mile_Slough Water temperatures in backwaters and sloughs]===

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-===Cool Mix does not stop entrainment===
+===Does not stop entrainment===
-===Cool Mix does not reduce water temperatures in backwaters and sloughs===
+===Does not reduce water temperatures in backwaters and sloughs===
-===Cool Mix does not stop the downstream movement of smallmouth bass into areas of the canyon where temperature control doesn't reach===
+===Does not stop the downstream movement of smallmouth bass into areas of the canyon where temperature control doesn't reach===

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 '''2023'''
 *[https://www.usbr.gov/uc/progact/amp/twg/2023-01-26-twg-meeting/20230126-TWGMeeting-GlenCanyonDamSmallmouthBassEnvironmentalAssessmentUpdate-508-UCRO.pdf Glen Canyon Dam/Smallmouth Bass Environmental Assessment Update]
 |-
-! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Other Stuff</h2>
+! <h2 style="margin:0; background:#cedff2; font-size:120%; font-weight:bold; border:1px solid #a3b0bf; text-align:left; color:#000; padding:0.2em 0.4em;">Cool Mix does not stop entrainment</h2>
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 ==2026==
-After careful consideration of management alternatives and evaluation of all authorized purposes and impacts, DOI made the decision to not implement Cool Mix flows in 2026. Efforts will instead focus on expanded rapid response removal actions, additional backwater modifications, evaluation of innovative tools, and advancement of durable structural solutions.
+After careful consideration of management alternatives and evaluation of all authorized purposes and impacts, DOI made the decision to not implement Cool Mix flows in 2026. Efforts instead focused on expanded rapid response removal actions, additional backwater modifications, evaluation of innovative tools, and advancement of durable structural solutions.
 ==2025==