March 22, 2024 

Kathleen Callister 

Adaptive Management Division Manager 

U.S. Bureau of Reclamation 

125 South State Street, Suite 800 

Salt Lake City, UT 84138 

LTEMPSEIS@usbr.gov 

Sent via email 

RE: Draft Supplemental Environmental Impact Statement for the Glen Canyon Dam 

Long-Term Experimental and Management Plan dated February 2024 

Dear Ms. Callister, 

The Grand Canyon Trust (“Trust”) submits this letter to provide comments on the U.S. 

Bureau of Reclamation’s Draft Supplemental Environmental Impact Statement for the Glen 

Canyon Dam Long-Term Experimental and Management Plan (“Draft SEIS”). Reclamation 

analyzes revising the 2016 Record of Decision for the Long-Term Experimental and 

Management Plan1 (“2016 ROD”) to 1) modify releases from Glen Canyon Dam to prevent 

smallmouth bass and other nonnative fish from establishing in Marble and Grand Canyons, 

which threaten the recovery of native humpback chub; and 2) modify the sediment 

accounting window set forth in the protocol for conducting high flow experiments in Marble 

and Grand Canyons under the Long-Term Experimental and Management Plan (“LTEMP”). 

The Grand Canyon Trust is a 501(c)(3) non-profit advocacy organization founded in 1985 with 

a mission to safeguard the wonders of the Grand Canyon and the Colorado Plateau, while 

supporting the rights of its Native peoples. We are headquartered in Flagstaff, Arizona and 

have more than 3,000 members and supporters. For decades, we have worked across the four 

corners region to secure protections for important cultural landscapes, safeguard water from 

uranium mining pollution, defend the unsustainable withdrawal of groundwater for 

development, protect the Grand Canyon ecosystem, and restore healthy forests and springs. 

We appreciate the opportunity to comment on these proposals to modify operations at Glen 

Canyon Dam and to consider how they fit into the broader challenges facing the Colorado 

River Basin. 

This Draft SEIS comes on the heels of Reclamation’s separate process to revise existing 

operational guidelines and obtain additional water conservation from the basin states in the 

near-term (2023-2026) to protect dam infrastructure, “stabilize the decline in reservoir 

1 U.S. Department of the Interior, Record of Decision for the Glen Canyon Dam Long-Term Experimental and 

Management Plan Final EIS dated December 2016. Available at:

https://ltempeis.anl.gov/documents/docs/LTEMP_ROD.pdf. 
2

storage,” and avert “system collapse” due to free falling reservoir elevations at Lakes Powell 

and Mead through 2022. 2 Earlier this month, Reclamation released its Final Supplemental 

Environmental Impact Statement for Near-Term Colorado River Operations (“Final Near-Term 

SEIS”), which adopted the Lower Basin’s plan to conserve an additional 3-million acre-feet 

over three years and granted Reclamation authority to reduce releases from Glen Canyon 

Dam to 6-million acre-feet as needed to protect elevations in Lake Powell at 3,500 feet above 

sea level.3 We commend this effort by Reclamation, the basin states, tribes, and others to 

reduce the risk of system collapse; however, the failure of that process to integrate and 

consider challenges to other environmental, biological, and cultural resources—especially 

those in Marble and Grand Canyons—and the water savings needed to also address those 

concerns4 is a missed opportunity and falls short of meeting the agency’s responsibilities 

under the Grand Canyon Protection Act of 19925 and the Endangered Species Act. 6 

Reservoir elevations at Lake Powell are the cause of and the solution to addressing the 

problems this Draft SEIS seeks to tackle including warmer water releases, passage of 

nonnative fish through the dam, establishment of nonnative species in Marble and Grand 

Canyons that will harm endangered and threatened native fish, and erosion of sandbars and 

beaches impacting environmental, cultural, and recreational resources below Glen Canyon 

Dam. While the flow options considered here may serve as a short-term solution to prevent 

smallmouth bass from establishing and causing harm to humpback chub and other native 

fish below the dam, the long-term and more sustainable solution requires balancing supply 

and demand in the basin—not just to prevent system failure and ensure continued water 

deliveries and power production—but to ensure that cultural, environmental, and 

recreational resources are protected and that native species that once thrived in the waters of 

the Colorado River—like humpback chub—persist long-term. 

It is with frustration that we find ourselves in a position that requires us to make a choice to 

endorse flow options, against the strong wishes of tribal communities expressed for many 

decades to respect and not take life in Marble and Grand Canyons, or decide between 

protecting, sustaining, or sacrificing resources like river flows, native fish, archaeological 

sites, recreational fishing and boating, hydropower, among others. It is important to consider 

here that these forced difficult choices remain because another difficult task—to live within 

2 U.S. Bureau of Reclamation, Final Supplemental Environmental Impact Statement for Near-Term Colorado River

Operations dated March 2024 at 1-8. Available at:

https://www.usbr.gov/ColoradoRiverBasin/documents/NearTermColoradoRiverOperations/20240300-NeartermColoradoRiverOperations-FinalSEIS-508.pdf. 3 Id. at 2-8 and 2-10. 4 The amount of water conservation adopted in the Final Near-Term SEIS for the 2023-2026 period was 2 to 3 times

less than proposals offered by the 6-basin states (1.7 to 3.4 million acre-feet per year) and California (1.2 to 3.3

million acre-feet per year) that were made before the windfall snowmelt runoff during the 2023 water year. For a 

more detailed analysis of the Final Near-Term SEIS, see Grand Canyon Trust’s Comments on Reclamation’s Draft

Supplemental Environmental Impact Statement for Near-Term Colorado River Operations dated October 2023. 

Available at: 

https://www.usbr.gov/ColoradoRiverBasin/documents/NearTermColoradoRiverOperations/PublicComments/Organi

zations/288_Grand%20Canyon%20Trust_508.pdf. 5 Grand Canyon Protection Act of 1992, Pub. L. No. 102-575, 106 Stat. 4600 (1992). 6 Endangered Species Act, Pub. L. No. 93-205, 87 Stat. 884, 16 U.S.C. §§1531-1544 (1973).
3

the means of the Colorado River—continues to be pushed aside to uphold century old 

promises to more water than exists in the watershed today. Further, those original promises 

were made in the absence of basin tribes and without consideration for the sustainability of 

the Colorado River and its tributaries, the health of river ecosystems, and the challenges a 

warming climate would have on the water supply in the basin. Ultimately, these promises can 

no longer be kept, and doing so will only deprive those not at the table a century ago, tribes 

and the environment, from receiving water to sustain their communities and the landscapes, 

ecosystems, and natural wonders we all hold dear. 

The Trust is supportive of Reclamation implementing the suite of cold-water alternatives 

analyzed in the Draft SEIS and updating the sediment accounting protocol for high flow 

experiments. We strongly encourage Reclamation to time flow spikes with high flow 

experiments where possible to create dual benefits for sediment resources in the canyons and 

to prevent spawning and establishment of nonnative fish. We fear that if Reclamation does 

not take immediate action—by implementing the most effective of the cold-water flow 

options based on the science (e.g. Cool Mix and Cool Mix with Flow Spike)—that 

smallmouth bass and other nonnative fish will become established in Grand Canyon. Such 

establishment will lead to harm to native fish including the largest and most stable 

population of humpback chub in the basin and result in even more consistent lethal 

management of nonnatives fish in the Grand Canyon, which will have direct, indirect, and 

cumulative effects on tribal values.7 The Draft SEIS specifies that “[t]he Zuni, in particular, 

have linked fish mortality in the Canyons with adverse physical, mental, and psychological 

effects within the Zuni Pueblo. Consequently, additional mortality would have negative 

cumulative effect on the Zuni.”8 We hope that Reclamation whenever possible will move 

forward with the least intrusive means (one that does not take life in the canyon) to prevent 

establishment of smallmouth bass and other nonnative fish, for example, focusing on 

utilizing the cool mix options (or other options preferred by Zuni, Hopi, Navajo, and other 

tribes) whenever possible. 

We also expect Reclamation to swiftly take other measures such as designing and 

implementing a fish barrier in Lake Powell to prevent additional nonnative fish passage 

through the dam and evaluating a temperature control structure or other infrastructure 

changes that could allow colder water to be passed through the dam. Ultimately, we expect 

Reclamation, the basin states, tribes, and other stakeholders to thoughtfully craft post-2026 

guidelines that incorporate these and other goals that protect cultural and environmental 

resources in the Grand Canyon and conserve water at a level and design storage in a way that 

meets the spirit and mandates of the Grand Canyon Protection Act and Endangered Species 

Act. 

The Trust details its comments below: 

7 See Hopi Tribe Comments on Framework to Prevent Invasive Fish Species Establishment Below Glen Canyon

Dam dated February 22, 2023 at 2, stating that “[t]he interrupting of life process through a process leading to death 

is not an acceptable method for Hopi. If something like a flow event would match a natural event in a natural time

this is something that can be discussed with Hopi as an option before Hopi elders and its Cultural Advisory Task 

Team.” Hopi comments 2-22-23 p1 8 Draft SEIS at 3-179.
4

I. Reclamation should take immediate action to finalize the Draft SEIS 

and issue a record of decision so the cold-water alternatives can be

implemented in summer 2024.

We appreciate Reclamation’s recognition that the timing of this Draft SEIS is key.9 The need 

to operate Glen Canyon Dam to reduce water temperatures and/or conduct flow spikes as 

soon as summer 2024 cannot be understated. The inability to implement such flows in 2023 

only set back efforts to curb population growth and expansion of smallmouth bass 

populations below Glen Canyon Dam (three times more smallmouth bass were captured in 

2023 than in 2022). The U.S. Fish and Wildlife Service emphasized that “the establishment of 

warmwater invasive fish, including smallmouth bass, below [Glen Canyon Dam] represents 

the greatest current potential threat to the continued survival and recovery of humpback 

chub in the Lower Colorado River basin.” 10 Similarly, the Arizona Department of Fish and 

Game “stress[ed] the importance of preventative measures in the management of high-risk 

warmwater non-native fish through temperature control” and commented that they support 

the proposed flow options “and believe that they serve as viable options to contribute to 

efforts designed to reduce the risk of establishment of Smallmouth Bass.”11 

Smallmouth bass populations below Glen Canyon Dam have increased significantly over the 

past two years and their distribution has expanded.12 “Prior to 2022, there are records of 22 

individuals being caught between Glen Canyon Dam and Pearce Ferry.”13 These mostly large 

adult or subadult fish were more highly concentrated above Lees Ferry (12 captures) and at 

the inflow into Lake Mead (7 captures), only a few were found near the confluence of the 

Little Colorado River (3 captures).14 These fish likely originated from passage through the 

dam at low elevations or past Pearce Ferry rapid above Lake Mead, but release temperatures 

from the dam were likely too cold for reproduction.15 However, “[s]tarting in 2022, many of 

the bass are smaller, indicating that these fish have been produced locally, probably in and 

around the -12-mile slough” in Marble Canyon.16 In 2022, 361 smallmouth bass were captured 

and that number increased three-fold to 1,073 smallmouth bass captured in 2023.17 These 

smallmouth bass were distributed more uniformly and consistently throughout the Colorado 

9 Draft SEIS at 1-8. 10 U.S. Fish and Wildlife Service, Scoping Comments on the Notice of Intent to Prepare a SEIS for Glen Canyon 

Dam LTEMP Revisions dated November 3, 2023 (USFWS 2023) at 2. Available at:

https://www.usbr.gov/uc/DocLibrary/EnvironmentalImpactStatements/GlenCanyonDamLongTermExperimentalManagementPlan/LTEMP-SEIS-ScopingComments/008_USFWS_508.pdf. 11 Arizona Department of Fish and Game, Comments on draft Glen Canyon Dam/Smallmouth Bass Flow Options

Environmental Assessment dated March 10, 2023 at 2. Available in Reclamation’s Public Comment Report at:

https://www.usbr.gov/uc/DocLibrary/EnvironmentalAssessments/GlenCanyonDamSmallmouthBassFlowOptions/20

230500-GlenCanyonDamSmallmouthBassFlowOptions-DraftEA-PublicCommentAnalysisReport-508-UCRO.pdf 12 Draft SEIS at 3-67. 13 Id. at 3-66. 14 Figure 3-24, Draft SEIS at 3-67. 15 Id. at 3-68; Attachment E, 2016 LTEMP ROD, U.S. Fish and Wildlife Service Biological Opinion for the Glen

Canyon Dam Long-Term Experimental and Management Plan at E-68. 16 Draft SEIS at 3-68. 17 Figure 3-24, Draft SEIS at 3-67.
5

River below Glen Canyon Dam, but are still mostly heavily concentrated in Marble Canyon 

above Lees Ferry, as shown in Figure 3-24 from the Draft SEIS, reproduced below: 

Further, preliminary modeling of potential smallmouth bass population growth (lambda) in 

2024 based on water temperature predicted that taking no action led to population growth in 

3% of traces at the confluence of the Little Colorado River (River Mile 61) based on the 30 

hydrologic traces analyzed.18 The population growth results were similar for the non-bypass 

18 Draft SEIS at 3-85 and Figure 1, Appendix A.
6

alternative.19 It should be noted that these percentages may be a little misleading in that these 

are estimates for the entire year. As shown in Figure 3-3520, water temperatures of Glen 

Canyon Dam releases are not predicted to reach anywhere near the temperature threshold of 

15.5°C for about half the year (December through April), and the median release temperatures 

do not reach this threshold until late summer August to November. Thus, it would be helpful 

for Reclamation to revisit this analysis to separate out the population growth by month, 

week, or day (e.g. the % of traces in July that showed population growth of lambda greater 

than 1), based on how many times the 15.5°C threshold is reached and for how long it 

continues. This would help assess the efficacy of the flow options and provide more granular 

picture of what operations under these alternatives might look like in a given summer. Since 

we do not have access to that analysis, we use the existing preliminary modeling as evidence 

to inform this analysis. 

The population growth predicted in 2024 would be on top of that seen in 2022 and 2023 and 

in a location—at the Little Colorado confluence—where a significant population of native 

humpback chub reside and would have increasing interactions with smallmouth bass.21 The 

Draft SEIS22 warns that 

Smallmouth bass are a major concern in the Upper Basin and are considered a 

contributing factor to the low abundance of native fish. If under the No Action 

Alternative smallmouth bass and other invasive fish (for example, green 

sunfish, walleye, and striped bass) become established in the Lower Colorado 

River despite other management actions to prevent further distribution (for 

example, mechanical removal), the No Action Alternative could detrimentally 

affect native species. 

Further, the cold-water flow options become more difficult and less effective to implement 

at target locations farther away from Glen Canyon Dam. As nonnative fish populations 

become established in the Little Colorado River confluence (River Mile 61), the amount and 

temperature of water required to cool the river this far downstream becomes incredibly 

challenging because of the miles of warming of those releases that occur between the dam 

and the target location. Acting now is important to addressing this serious problem for 

humpback chub and other native fish. 

The continued reproduction, distribution, and establishment of smallmouth bass in Marble 

and Grand Canyons will continue exponentially along the invasion curve unless and until 

Reclamation takes immediate and decisive action to operate the most effective cold-water 

alternative(s) contemplated in the Draft SEIS to cool the river and prevent additional 

spawning of smallmouth bass. We do not have time to wait, take no action, or try actions like 

the non-bypass alternative at this juncture. We appreciate Reclamation’s efforts to move 

swiftly through this process under the National Environmental Policy Act and hope that the 

agency can issue a Record of Decision before summer of 2024. The Trust strongly 

19 Id. 20 Draft SEIS at 3-157. 21 Id. at 3-85. 22 Id.
7

recommends Reclamation take immediate action using the most effective means possible 

(e.g. implementation of the Cool Mix or Cool Mix with Flow Spike alternatives) based on its 

research and modeling to ensure that additional population growth and distribution of 

smallmouth bass does not occur in Marble and Grand Canyons in 2024 and beyond. 

II. Reclamation should move forward with the suite of cold-water

alternatives to prevent establishment of smallmouth bass in

Marble and Grand Canyons.

Given the current and projected reservoir elevation(s) at Lake Powell from 2024-2027 and the 

modest amount of water savings secured in the Final Near-Term SEIS, the cold-water flow 

options (Cool Mix, Cool Mix with Flow Spike, Cold Shock, and Cold Shock with Flow Spike) 

appear to be the best and most effective short-term option for preventing the establishment 

of smallmouth bass in Marble and Grand Canyons. Figure 3-5 from the Final Near-Term 

SEIS23, reproduced below, shows in purple the projected end-of-month reservoir elevations at 

Lake Powell through the end of 2026 based on the selected alternative. While the current 

reservoir elevation (3,560 feet) presents a lower risk of passing additional nonnative fish 

through the dam and warmer water releases than elevations reached in 2022 and 2023 (3,520 

feet), Lake Powell’s elevation is still only 32% of capacity and is projected at the lower end of 

forecasts to fall in 2025 toward critical elevations and may fall below or hover around 3,500 

feet for an extended part of 2026. 

If Lake Powell reservoir elevations again decline, which is very likely, it will mean 1) more and 

ongoing nonnative fish passage through the dam as the warmer reservoir layer with 

nonnative fish approaches the penstocks, 2) warmer dam releases and increased water 

temperature in the Colorado River below, 3) the creation of favorable conditions for 

23 Final Near-Term SEIS at 3-29.
8

nonnative fish spawning and establishment below the dam and further downstream, 4) the 

cold-water flow options will be harder to achieve target temperatures, and 5) more cold water 

bypass will likely be required in an effort to reverse those conditions (especially at 

downstream locations like the Little Colorado River and Diamond Creek) to prevent 

spawning of nonnative fish. Taking no action or implementing the non-bypass alternative 

will only increase the already unacceptable risk of additional reproduction and distribution 

of smallmouth bass in Marble and Grand Canyons. 

Preliminary modeling24 shows that the Cool Mix and Cool Mix with Flow Spikes followed by 

the Cold Shock and Cold Shock with Flow Spikes appear to be the most effective options we 

have for decreasing river water temperatures and preventing spawning of smallmouth bass.25 

Figure 1 in Appendix A26 shows the percentage of 30 modeled traces that showed population 

growth for the no action, four cold-water, and no bypass alternatives; data from that figure is 

reproduced as the Trust’s Table 1, below: 

Table 1. Forecast of Potential Annual Smallmouth Bass Population Growth Rate27

Alternative River Mile Percent of traces showing population growth 

(lambda >1)

2024 2025 2026 2027

No Action RM 15 (Lees Ferry) 0% 7% 10% 17%

RM 61 (LCR) 3% 10% 17% 17%

Cool Mix and

Cool Mix with Flow Spikes

RM 15 (Lees Ferry) 0% 0% 0% 0%

RM 61 (LCR) 0% 0% 0% 0%

Cold Shock and

Cold Shock with Flow Spikes

RM 15 (Lees Ferry) 0% 0% 3% 3%

RM 61 (LCR) 0% 3% 7% 10%

Non-Bypass RM 15 (Lees Ferry) 0% 7% 10% 17%

RM 61 (LCR) 3% 10% 17% 17%

Table 1 shows that annual population growth is predicted in more traces in the no action and 

non-bypass alternatives than if the cold-water alternatives are deployed. This makes sense 

given how important temperature is at regulating spawning in smallmouth bass.28 

The preliminary modeling reported in Appendix A “predicts that smallmouth bass 

population growth (lambda) at river mile 15 and at the Little Colorado River confluence 

24 The preliminary modeling developed by Eppehimer and Yackulic (see Appendix A) “assesses the potential for

smallmouth bass population growth rate at river mile 15 and river mile 61 for each year 2024-2027 “[b]ased on 

assumed functional relationships between smallmouth bass population dynamics, available habitat, predicted 

temperature responses, and rate of entrainment.” The model’s output predicts the rate of population growth (lambda) 

and shows the average annual percentage of traces showing such growth (lambda great than 1). Draft SEIS at 3-88; 

see report in Appendix A. 25 Draft SEIS at 3-97. 26 Figure 1, Appendix A, Draft SEIS at A-7. 27 Data reproduced from Draft SEIS, Figure 1, Appendix A at A-7. 28 See the detailed discussion of the science in Section III, below.
9

would be below 1.0 for only the cool mix and cool mix with spike flows. This means that 

these two alternatives, if implemented under the right conditions and model assumptions 

are accurate, could prevent population growth of the smallmouth bass in these two areas.”29 

Given the modeled effectiveness of the cool mix flow option, we suggested utilizing the cool 

mix option in 2024 upon triggering of threshold temperatures and executing a 

comprehensive program to monitor, measure, and report the results of that effort (especially 

in backwater habitats) to determine if additional efforts (e.g. flow spikes) are necessary or if 

cool water bypass alone will lower water temperatures in those habitats and prevent the 

initiation of spawning by smallmouth bass. The cool mix flow option may be the most 

effective and possibly least controversial flow option (if any of these options address the 

concerns of the Zuni, Hopi, Navajo, or other tribes) from the perspective of working with the 

least invasive measures to honor the tribes’ value of not taking life in the canyon. 

While there was some population growth in traces for the Cold Shock and Cold Shock with 

Flow Spike alternatives, these alternatives still appear to have population growth in less 

traces than the no action and non-bypass alternatives. Reclamation should include these 

additional cold water flow options as additional measures to test as needed to cool water 

temperatures and prevent spawning and establishment of smallmouth bass. These options 

also have less impacts to hydropower production, so these might be alternatives that can be 

used in situations where those impacts are greatest and/or cannot be mitigated. 

Reclamation should adopt and implement the full range of proposed cold-water flow options 

that tackle both the temperature of the Colorado River and disruptions to spawning through 

changes in river velocity. We understand that these cold-water alternatives will need to be 

implemented, monitored, and the results documented to fully understand their effectiveness 

and impacts to other LTEMP resources. The sooner we can test the effectiveness of these 

tools—hopefully in 2024 when conditions may be less dire in terms of reservoir elevations, 

warmwater releases, and nonnative fish passage, than is projected for 2025-2026—the more 

information we will have to help refine these flow options, mitigate resource impacts, and 

operate under more challenging conditions. We suggest moving forward will all four coldwater flow alternatives to allow a range of tools that can be deployed based on when and 

where the threat is highest for nonnative reproduction each year. 

III. The Non-Bypass Alternative does not meet the purpose and need

of the proposed action.

Reclamation should eliminate the Non-Bypass Alternative from consideration at this time 

because it does not meet the purpose and need of the proposed action and it fails to perform 

in preliminary modeling any better than the no action alternative in limiting the population 

growth rate of nonnative species in the Colorado River below Glen Canyon Dam. We 

appreciate that Reclamation modeled and analyzed this option for preventing smallmouth 

establishment below the dam considering its benefits for hydropower resources; however, 

the alternative (at least at current and projected Lake Powell reservoir elevations) does not 

29 Draft SEIS at 3-97.
10

address the problematic temperature regime in the Colorado River below the dam and thus 

does not meaningfully discourage or prevent recruitment in smallmouth bass. Further, this 

alternative may have additional negative effects on other LTEMP resources. Thus, under 

current and projected conditions, the non-bypass alternative does not meet the purpose and 

need. 

As an initial matter, the flow options designed in the Draft SEIS are triggered when Glen 

Canyon Dam water releases through the penstocks reach a threshold temperature of 15.5°C 

(60°F). At that time, the goal is to reduce water temperatures in the Colorado River below 

Glen Canyon Dam to avoid the onset of spawning. The non-bypass alternative does nothing 

to address the threshold issue of increased water temperatures. Instead, the non-bypass 

alternative suggests releasing additional both low and high flow fluctuations to disrupt 

nesting by smallmouth bass and displace individual adult fish and harm the young being 

produced. This strategy essentially allows spawning and recruitment to continue. While the 

disruption of the physical habitat from flow fluctuations may result in nest abandonment or 

displace fry and eggs temporarily, it does not affect water temperature, thus allowing 

smallmouth bass the ability to renest, spawn and continue recruitment once river stage 

changes cease. 

The Non-Bypass Alternative does not act to mitigate warm water temperatures in the 

Colorado River below Glen Canyon Dam. “Temperature is one of the most important factors 

limiting distribution of smallmouth bass (Bestgen 2018)”30. “Smallmouth bass have been 

observed laying eggs at water temperatures as low as 15 degrees Celsius (°C) (59 degrees 

Fahrenheit [°F]) in some systems; however, water temperature of 16°C (61°F) or greater are 

typically required for smallmouth bass to lay eggs.”31 The Draft SEIS states 

Water temperatures of 16°C (61°F) or greater are also required for young of 

year to grow significantly, if hatched. Growth of smallmouth bass at a 

temperature of 16°C (61°F) is marginal. Therefore, if a fish is hatched and 

maintained at approximately 16°C (61°F) for the length of a typical growing 

season, it would be very unlikely to grow large enough to survive the winter 

(Shuter et al. 1980; Dudley et al 2104).32 

Thus, the best chance for limiting recruitment would be to keep temperatures below these 

thresholds so no eggs are laid or the young of year stay so small that they do not survive to 

become adults. 

Preliminary modeling33 of the potential annual population growth rate for smallmouth bass 

under the non-bypass alternative showed population growth in similar number of traces as 

the no action alternative. Generally, the analysis found that at both River Mile 15 and 61 the 

non-bypass alternative reduced “the estimated lambdas when compared with no action, but 

30 Draft SEIS at 3-68. 31 See Appendix A, Draft SEIS at A-1 to A-2. 32 Appendix A describes the assumptions made including how release temperatures were calculated for every day of

the year and an estimate of downriver warming was predicted based on similar model by Dibble et al. 2021.32 Id. at 

A-2. 33 See Draft SEIS, Figure 1, Appendix A at A-7.
11

did not stop population growth.”34 Figure 1, showed the number of traces that showed 

population growth (lambda greater than 1) : 

Table 2. Forecast of Potential Annual Smallmouth Bass Population Growth Rate35

Non-Bypass 

Alternative 

Percent of traces showing population growth (lambda >1) 

2024 2025 2026 2027 

River Mile 15 (Lees 

Ferry) 

0% 7% 10% 17% 

River Mile 61 (LCR 

confluence) 

3% 10% 17% 17% 

The percentage of traces showing population growth for the non-bypass alternative are the 

same as for the no action alternative. Reclamation found that “[t]he No Action Alternative 

would not meet the project’s purpose or need.”36 Likewise, the non-bypass alternative does 

not meet the purpose and need of the proposal. The Fish and Wildlife Service, in its scoping 

comments for this SEIS, agreed that “[t]he scientific literature, in addition to recent flow and 

temperature modeling, indicate that cooling water temperatures to below 16°C is the only 

effective method to prevent spawning, recruitment, and establishment of smallmouth bass in 

Glen Canyon” and “this is the best method for preventing their spread into western Grand 

Canyon.”37 

The Non-Bypass Alternative fails to meet the purpose and need of the proposed action 

during the 2024-2027 timeframe. The purpose and need of the proposed action is “to analyze 

flow options at Glen Canyon Dam . . . to disrupt the establishment of smallmouth bass below 

Glen Canyon Dam by limiting additional recruitment” (Emphasis added).38 While the nonbypass alternative seeks to use fluctuating flows to “cause male smallmouth bass to abandon 

nests in shallower nearshore habitats, such as backwaters or sloughs, and higher-velocity 

releases to displace eggs and fry, or cause abandonment by male smallmouth bass,”39 these 

disruptions do not affect temperature “limiting additional recruitment.” The Service “does 

not believe that penstock releases alone (the new Hydropower Alternative), would meet the 

purpose and need of this program in the short term as water temperatures at the penstock 

intakes are too warm to meet outflow temperature objectives needed to prevent spawning.”40 

34 Id. at A-6. 35 Data reproduced from Figure 1, Appendix A at A-7. 36 Draft SEIS at 2-10. 37 USFWS 2023, Scoping Comments at 3. 38 Draft SEIS at 1-6. 39 Draft SEIS at 3-94. 40 USFWS 2023, Scoping Comments at 3.
12

IV. The Non-bypass Alternative’s benefits to hydropower do not

outweigh the risks to other cultural, environmental, and

recreational resources in Marble and Grand Canyons.

Reclamation should not move forward with the Non-Bypass Alternative because its benefits 

to hydropower generation do not outweigh the risks to other resources in Marble and Grand 

Canyons. The non-bypass alternative is the only flow option that does not “operate within 

the spatial and temporal bounds and under the assumptions of the existing analysis in the 

LTEMP FEIS.”41 Thus, Reclamation should be more cautious about implementing such an 

option without greater certainty of the impacts to LTEMP resources as outlined throughout 

the Draft SEIS as follows: 

Geomorphology and Sediment—The non-bypass alternative “would cause the greatest 

reductions in mass balance starting in Spring 2025” and “would generally produce the 

second-smallest sandbars, slightly surpassing volumes that would be generated under 

alternatives without flow spikes.”42 

Aquatic Resources/Native Fish—High flows resulting from the non-bypass alternative may 

cause “some young [native] fish [to] become displaced from shorelines or backwaters and 

exposed to predation and starvation,” but the effects should be minimal. The low flows, 

however, “if they occurred April - June, could negatively affect young and juvenile 

flannelmouth suckers and bluehead suckers that could be displaced from desiccated 

shoreline habitats and backwaters.”43 

Aquatic Resources/Rainbow Trout—The flow fluctuations in the non-bypass alternative are 

“expected to displace young and juvenile [rainbow] trout and expose these fish to starvation 

and predation.”44 

Aquatic Resources/ Food Base—The non-bypass alternative’s low flows “would desiccate 

much of the river bottom, especially the shallow shelves where most primary and secondary 

production occur” and the Draft SEIS admits that the effects of 2,000 cfs on the food base 

have not been evaluated.”45 

Riparian Vegetation/Wildlife—The daily flow fluctuations that would occur as a result of 

the non-bypass alternative may reduce shoreline stability46 and such “instability could lead to 

a decrease in the abundance of aquatic invertebrates and greater disruption to wildlife 

habitat.”47 “Amphibians, reptiles, and insects may be less able to adapt to the less stable 

shoreline environment, resulting in decreased biodiversity or abundance.”48 

41 Draft SEIS at 3-16. 42 Id. at 3-47. 43 Id. at 3-95. 44 Id. 45 Id. at 3-96. 46 Id. at 3-103 and 3-112. 47 Id. at 3-112. 48 Id.
13

Threatened and Endangered Species—The non-bypass alternative’s low flow events “have 

rarely been seen in the Colorado River downstream of Glen Canyon dam” and studies (Valdez 

and Ryel 1995) indicate “that much of the shoreline talus habitat and backwaters used by 

juveniles were dewatered during extreme low-flow events, forcing fish to move to 

mainstream habitats” at risk of greater predation.49 This may harm native humpback chub 

and razorback sucker. 

Cultural Resources/Archaeological Sites—“The low flows proposed under the Non-Bypass 

Alternative are outside those analyzed in the LTEMP FEIS and may lead to the exposure of 

archaeological sites and sacred sites.”50 Such “exposure could lead to damage or disturbance 

from wave action, wet/dry effects, and increased visitation.”51 

Tribal Resources/Taking of Life in the Canyons—The non-bypass alternative has the 

greatest impacts on fish compared to the other alternatives.52 The high and low “flows would 

be intended to reduce survival of smallmouth bass eggs and fry through desiccation of eggs, 

abandonment of nests, and impacts on fry.”53 The non-bypass alternative adds to the 

cumulative impacts on tribal values including those expressed by the Zuni who “have linked 

fish mortality in the Canyons with adverse physical, mental, and psychological effects within 

the Zuni Pueblo.”54 “Because the action alternatives could result in the taking of life within 

the Canyons, they would have an adverse impact on the Zuni culture and TCPs, if 

Reclamation implements the flow options with expected fish mortality.”55 

Recreation/Fishing—The non-bypass alternative’s “rapid fluctuations in water levels may [] 

disrupt fishing during implementation.” High flows are “likely to displace young and juvenile 

rainbow trout and expose these fish to starvation and predation,”56 while low flows that occur 

“between January and March, [] could negatively affect eggs and fry through desiccation and 

displace juvenile [rainbow trout].”57 

Recreation/Boating—Under the non-bypass alternative, low flows “could limit the ability of 

boats to freely navigate in the Glen Canyon reach, which would adversely impact boating and 

the rafting concessionaire in the short term compared with other alternatives.”58 In the 

Grand Canyon, the low flows of 2,000 cfs “would be below the safe whitewater minimum, 

which would adversely affect whitewater boating opportunities [in the park]”59 “and the 

ability of Hualapai River Runners to provide boating trips compared with all other 

alternatives.”60 

49 Id. at 3-133 and 3-134. 50 Id. at 3-172, 3-180, and 3-181. 51 Id. at 3-172. 52 Id. at 3-179 53 Id. 54 Id. 55 Id. 56 Id. at 3-190. 57 Id. 58 Id. at 3-193. 59 Id. at 3-191 and 3-193. 60 Id. at 3-191.
14

Recreation/Socioeconomic—“The high and low fluctuations of water under the Non-Bypass 

Alternative could impact the boater experience in both the Glen Canyon and Grand Canyon 

reaches.” The flow “unpredictability could pose challenges for boaters navigating through the 

area” and low flows “would limit the ability of boats to navigate freely in the Glen Canyon 

reach. This would adversely impact boating and rafting concessionaires’ operations 

compared to other alternatives.”61 

To summarize, the non-bypass alternative has direct, indirect, and cumulative effects to 

nearly all the LTEMP resources and thus requires Reclamation to eliminate it from further 

consideration. This alternative likewise does not meet the mandates of the GCPA “to protect, 

mitigate adverse impacts to, and improve” the cultural and environmental resources in 

Grand Canyon or ensure the survival and recovery of native fish listed under the ESA. 

V. Reclamation should amend the HFE protocol to allow for more 

consistent and naturally timed spring high flows through Grand

Canyon.

A. Adjusting the sediment accounting period is key for improving Reclamation’s 

ability to implement HFEs and ensure sediment resources are protected as

mandated by the GCPA.

High flow experiments are critical to protect, mitigate adverse impacts to, and improve the 

transport and accumulation of sediment in Marble and Grand Canyons as mandated by the 

GCPA. “Glen Canyon Dam effectively cut off approximately 95 percent of the historical 

sediment supply from the upper watershed (Topping et al. 2000).”62 Since the dam was closed 

in 1963, at least 28 million metric tons of sand has eroded and about half of that eroded in the 

late 1990s, including six metric tons from each Marble and Grand Canyons.63 HFEs are the 

only mechanism for transporting sediment inputs from tributaries throughout Marble and 

Grand Canyons and are the sole source of mitigation to address the adverse impacts to 

sediment resources since the construction of Glen Canyon Dam. 

“Sandbars and beaches are important for biological, cultural, and recreational resources 

along the Colorado River.”64 Sandbars are vital as a foundation for riparian vegetation, to 

create low velocity habitat for young fish, provide a source of sand to be transported by wind 

to protect archaeological resources, and to build camping beaches for recreation.65 These are 

all values the GCPA was intended to safeguard and are key to consider when thinking about 

61 Id. at 3-209. 62 Id. at 3-35. 63 Topping, D. J., Grams, P.E., Griffiths, R.E., Dean, D.J., Wright, S.A., & Unema, J.A. (2021). Self-limitation of 

sand storage in a bedrock-canyon river arising from the interaction of flow and grain size. Journal of Geophysical

Research: Earth Surface, 126, e2020JF005565. Available at: https://doi.org/10.1029/2020JF005565 64 Final Near-Term SEIS at 3-89. 65 Id.
15

making changes to the sediment accounting windows that currently exist in the HFE 

protocol. 

Amending the HFE protocol to allow for more consistent high flows through Grand Canyon 

is needed given climate change. The warming climate and overallocation of water in the 

Colorado River Basin have led to lower water levels at Lake Powell, which has resulted in 

decisions by the Secretary of the Interior to not implement HFEs in years when the sediment 

triggers were met including 2015, 2021, and 2022.66 “The absence of Spring HFEs during the 

first 10 years of the HFE protocol, coupled with analyses documenting reduced transport of 

fine sediments in years with low reservoir volumes and low Lake Powell elevations, have 

prompted the [Glen Canyon Dam Adaptive Management Program] to reassess the HFE 

protocol.”67 The two 6-month (fall and spring) sediment accounting windows are proposed to 

be adjusted to operate under a new 1-year window in all but the no action alternative.68 

The HFE protocol is being updated “to improve Reclamation’s ability to implement HFE 

releases” by adjusting sediment accounting periods and HFE implementation windows.69 

Failing to take action to ensure more frequent and high magnitude HFEs is contrary to the 

mandates of the GCPA and does not meet the purpose and need of the proposed action. The 

Draft SEIS provides that taking no action under the existing conditions of drought and 

aridification “could result in the continued trend of fewer and smaller HFE releases.”70 Like 

historically, “HFEs are more likely to be triggered in the fall with low likelihood of HFEs in 

the spring,” and would be subject to the same concerns that HFEs would be triggered but not 

implemented like in 2021 and 2022.71 Reclamation concludes that “the reduced number and 

magnitude of HFE releases would not optimize the best available science for sediment 

accounting” and determined that the no action alternative does not meet the purpose and 

need of the proposed action.72 Further, fewer and smaller HFEs would amplify the impacts on 

sediment resources, which is contrary to the mandates of the GCPA. 

B. The cold-water alternatives combined with modification of the HFE protocol

will lead to a greater chance of spring HFEs and if flow spikes are combined 

with HFEs where possible dual benefits for sediment resources and preventing

smallmouth bass establishment may be possible.

The cold-water alternatives in combination with modification of the sediment accounting 

window will lead to favorable conditions for high flow experiments that have greater chance 

of occurring in spring mimicking pre-dam hydrology. The cold-water alternatives without 

flow spikes “would increase the likelihood of spring HFEs by approximately 26 percent.”73 

66 2023 Proposal to Amend the High-Flow Experiment Protocol and Other Considerations developed by the Flow at

5. Available at: https://www.usbr.gov/uc/progact/amp/amwg/2023-08-17-amwg-meeting/20230817-

ProposalAmendHigh-FlowExperimentProtocolOtherConsiderations-508-UCRO.pdf. 67 Id. at 5. 68 Draft SEIS at 2-5. 69 Id. at 1-6. 70 Id. at 2-10. 71 Id. at 3-42. 72 Id. 73 Id. at 3-42.
16

The duration of springs HFEs would also increase to about 110 hours on average, but fall 

HFEs duration will likely decrease by half (56 hours compared to 98 hours under no action).74 

The sediment mass balance for the alternatives without flow spikes would be slightly higher 

than the no action alternative because on average the HFE duration (spring and fall) would 

be slightly shorter.75 Sandbar volume would continue to increase with smaller, but more 

frequent growth.76 

The cold-water alternatives with flow spikes lead to similar HFE regimes as those that would 

occur without flow spikes, but in some years, “would cause sand export in the lead-up to 

HFE implementation” reducing the resulting duration.77 Thus, Reclamation should combine 

flow spikes with HFEs whenever possible and avoid flow spikes outside the accounting 

window, so as not to export sand prior to the HFE potentially affecting HFE duration or lead 

to deferral.78 Further, flow spike alternatives that “increase sediment export, thereby 

decreasing the amount of available sand to perform an HFE . . . would cause a reduction in 

sandbar size, because HFEs are the only mechanism for providing substantial deposition of 

high elevation sandbars (Hazel et al. 2022).”79 Flow spikes could lead to a negative mass 

balance over the long-term.80 

As intended, the change to the sediment accounting period should “enable decision-makers 

to more easily implement HFEs in the spring, which would better approximate pre-dam 

conditions of high spring run-off flows.”81 While “sand mass balance would undergo more 

gradual and frequent decreases following HFEs and this trend would be mirrored in sandbar 

growth patterns,” the result may be smaller and slower growth but more consistent 

implementation and better timing of HFEs. 82 When combined with the cold-water 

alternatives, Reclamation should combine HFE and flow spikes whenever possible to meet 

multiples goals of getting cold water into backwater habitats, disrupting spawning, and 

creating a river stage large enough to transport sediment and build sandbars in Marble and 

Grand Canyons. These efforts are needed to protect, mitigate adverse impacts to, and 

enhance the cultural, environmental, and recreational resources in the canyons. The Trust is 

supportive of modifying the sediment accounting window and strongly encourages 

Reclamation to proceed with this amendment of the HFE protocol. 

74 Id. 75 Id. 76 Id. at 3-46. 77 Id. at 3-43. 78 Id. at 3-43 and 3-47 79 Id. at 3-46 and 3-47. 80 Id at 3-46. 81 Id. at 3-47. 82 Id.
17

C. Reclamation needs to be explicit about whether Lake Powell reservoir 

elevations of 3,500 feet will prevent implementation of HFEs in practice and

take additional measures to ensure continued HFEs are possible.

The Draft SEIS assumes that no HFEs will occur if Lake Powell is below 3,500 feet.83 The 

Draft SEIS does not clarify at what point Lake Powell falling below 3,500 feet eliminates the 

HFE (e.g. in the water year, within the month the HFE is planned). This should be made 

explicit so that it is not used too narrowly or broadly to prevent HFEs when triggered. 

Further, it should be clearly stated that, flow spikes can and will occur as needed to prevent 

the establishment of smallmouth bass despite the elevation of Lake Powell and will be timed 

with HFEs whenever possible. If this is not the case, then the flow options with flow spikes 

have little to no utility when the conditions are the worst for passage of nonnative fish and 

warmwater conditions in the Colorado River below Glen Canyon Dam. Finally, Reclamation 

has a responsibility under the GCPA to protect, mitigate adverse impacts to, and to enhance 

sediment resources in Grand Canyon. HFEs are critical to meeting this charge. Reclamation 

needs to work to secure additional water conservation measures in the basin to ensure that 

Lake Powell reservoir elevations stay well above 3,500 feet (the threshold for HFEs 

enumerated in the Draft SEIS) to ensure that cultural and environmental resources can be 

sustained. 

VI. Reclamation’s decision needs to honor the mandates of the Grand

Canyon Protection Act.

A. Reclamation has authority to prioritize the cultural, environmental, and

biological resources in Marble and Grand Canyons over hydropower interests.

Reclamation has authority under the GCPA to ensure that the environmental, cultural, and 

biological resources below Glen Canyon Dam are protected even if in so doing impacts occur 

to hydropower resources. Section 1802(a) of the GCPA provides that: 

The Secretary shall operate Glen Canyon Dam in accordance with the 

additional criteria and operating plans specified in section 1804 and exercise 

other authorities under existing law in such a manner as to protect, mitigate 

adverse impacts to, and improve the values for which Grand Canyon National 

Park and Glen Canyon National Recreation Area were established, including, 

but not limited to natural and cultural resources and visitor use. 

(Emphasis added.)84 

83 Draft SEIS at 2-5. 84 The Draft SEIS at 1-9, suggests a much narrower view of the law that “LTEMP [] controls the timing of annual

releases to improve downstream conditions, meeting the requirements of the Grand Canyon Protection Act, and

minimizing—consistent with other laws—adverse impacts on downstream natural, recreational, and cultural

resources.” We believe this is too narrow an interpretation of the authority in section 1802(a) of the GCPA.
18

Former Reclamation Commissioner and Deputy Secretary of the Interior, Michael Connor, 

described the Act85 as follows: 

The GCPA is a congressional attempt to protect the natural and cultural 

environment downstream of Glen Canyon by defining the priorities under 

which DOI must operate the dam. The law of the river is still paramount in 

dictating releases, but now the protection of downstream resources takes 

priority over all other values. In fact, the legislative history indicates that the 

GCPA specifically rejects the notion that power generation has any priority 

over protection of downstream environmental, recreational, or cultural values. 

This reordering of priorities, recognizing traditionally overlooked values, is by 

itself enough to make the GCPA a significant piece of legislation. 

Further, the goal of the GCPA goes beyond protecting downstream resources and specifically 

contemplates “improv[ing] the values for which Grand Canyon National Park and Glen 

Canyon National Recreation Area were established.”86 Reclamation has authority under the 

GCPA that “gives priority to protection of the Grand Canyon, and all other values must 

operate within this mandate.”87 We request that Reclamation consider and prioritize 

safeguarding humpback chub and other native species over hydropower in this instance. 

B. The GCPA should be included in the Draft SEIS as a key source of authority.

The GCPA should be included as the source of authority for the Long-term Experimental and 

Management Plan in the introductory paragraph of the Draft SEIS at 1-1. The existing 

statement emphasizes hydropower generation of the dam without putting that in context of 

other resources that are required to be managed by Reclamation including the mandate to 

“protect, mitigate adverse impacts to, and improve the values for which Grand Canyon 

National Park and Glen Canyon National Recreation Area were established.” The Trust 

recommends being explicit about Reclamation authority to “adaptively manage this stretch 

of river” by including the following additional language: 

To adaptively manage this stretch of river according to the mandates of the 

Grand Canyon Protection Act of 1992 and other laws, the United States (US) 

Department of the Interior (Department) Bureau of Reclamation 

(Reclamation), developed the Long-Term Experimental and Management Plan 

(LTEMP) for operations of Glen Canyon Dam, the largest hydropowergenerating unit of the Colorado River Storage Project (CRSP; DOI 2016a).88 

(Emphasis added). 

85 Connor, Michael. June 1994. Extracting the Monkey Wrench from Glen Canyon Dam: The Grand Canyon

Protection Act – An Attempt at Balance. 15 Pub. Land L. Rev. at 152. Available at

https://scholarworks.umt.edu/cgi/viewcontent.cgi?article=1313&context=plrlr. 86 Id. at 154. 

87 Id. at 137. 88 Draft SEIS at 1-1.
19

VII. The Endangered Species Act requires Reclamation not to 

jeopardize the survival and recovery of endangered and

threatened species.

The Endangered Species Act provides “a program for the conservation of . . . endangered 

species and threatened species” and “a means whereby the ecosystems upon which 

endangered species and threatened species depend may be conserved.”89 Congress intended 

by enacting the statute “to halt and reverse the trend towards species extinction, whatever 

the cost.”90 The ESA mandates the federal agencies “afford first priority to the declared 

national policy of saving endangered species.”91 

Section 7 of the ESA prohibits federal agencies from undertaking actions that are “likely to 

jeopardize the continued existence” of any listed species or “result in the destruction or 

adverse modification of” critical habitat. 92 “Jeopardy” results when it is reasonable to expect, 

“directly or indirectly,” the action would appreciably reduce “the likelihood of both the 

survival and recovery of a listed species in the wild by reducing the reproduction, numbers, or 

distribution of that species.”93 “Adverse modification” is defined as “a direct or indirect 

alteration that appreciably diminishes the value of critical habitat for the conservation of a 

listed species.”94 

As such, Reclamation has both a procedural and substantive obligation under Section 7(a)(2) 

of the ESA. First, to satisfy its procedural duty, Reclamation must consult with the Service 

before undertaking any “action” that “may affect” a listed species or its designated critical 

habitat using the best available science. 95 Second, based on that formal consultation, the 

Service must issue a biological opinion to make a substantive determination and explain 

whether the agency action is likely to cause jeopardy to any listed species.96 

Reclamation’s ongoing actions under the 2016 Long-term Experimental and Management 

Plan are taken pursuant to the 2016 LTEMP Biological Opinion97 issued by the Service, 

which found no jeopardy to listed species at that time. However, the 2016 LTEMP Biological 

Opinion detailed conservation measures necessary to prevent jeopardy and help ensure the 

survival and recovery of the threatened humpback chub. The danger to humpback chub from 

nonnative species was clear in 2016 and several significant measures were included to ensure 

89 16 U.S.C. § 1531(b). 90 Tennessee Valley Authority v. Hill, 437 U.S. 153, 184 (1978). 91 Id. at 188. 92 16 U.S.C. § 1536(a)(2). 93 50 C.F.R. §402.02. 94 Id. 95 16 U.S.C. § 1536(a)(2); 50 C.F.R. §402.14(a). 96 16 U.S.C. § 1536(a)(2); 50 C.F.R. §402.14(h). 97 U.S. Fish and Wildlife Service, 2016, Final Biological Opinion for the Glen Canyon Dam Long-Term Experimental 

and Management Plan, U.S. Fish and Wildlife Service, Arizona Ecological Services Office, Phoenix, Ariz., 

Executive Summary E-11 to E-12, E-69. Available at 

https://www.usbr.gov/uc/DocLibrary/Reports/LTEMPReports/20230628-LTEMPBiologicalOpinionProgressReportComplianceConservationMeasuresFY2022-508-UCRO.pdf. 
20

Reclamation took steps to protect the humpback chub from these threats. The conservation 

measures set out the in the 2016 Biological Opinion include: 

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; 

pursue means of preventing the passage of deleterious invasive nonnative fish 

through Glen Canyon Dam; 

planning and compliance to alter the backwater slough at River Mile (RM) 12 

(commonly referred to as “Upper Slough”), making it unsuitable or inaccessible 

to warmwater nonnative species that can compete with and predate upon 

native fish, including humpback chub; and 

planning and compliance of a plan for implementing rapid response control 

efforts for newly establishing or existing deleterious invasive nonnative species 

within and contiguous to the action area.98 

“These conservation measures are designed to minimize or reduce the effects of the proposed 

action or benefit or improve the status of listed species as part of the LTEMP.”99 It is clear 

from the 2016 Biological Opinion that a need already existed to take actions around 

nonnative warmwater fish in 2016 and that it “may become a more frequent need ... with 

lower reservoir elevations and warmer dam releases.”100 

As detailed in the Draft SEIS, the threat to the threatened humpback chub and endangered 

razorback sucker from the establishment of nonnative fish below the dam has increased 

significantly since 2022. Low reservoir elevations at Lake Powell—that have and will likely 

continue to pass nonnative fish through the penstocks as well as facilitate warmer water 

releases from the dam—have created conditions in Marble and Grand Canyons that make the 

establishment of smallmouth bass below Glen Canyon Dam possible and likely if immediate 

actions are not taken by Reclamation. The problem may not be as acute today had 

Reclamation fulfilled the conservation measures it committed to in 2016. Given the threefold increase in captures of smallmouth bass below Glen Canyon Dam in 2023 and urgent 

need for the actions proposed in the Draft SEIS, Reclamation must reconsult with the 

Service. The Service should review Reclamation’s progress over the past decade and 

determine if more clear and mandatory measures are needed on the part of Reclamation to 

ensure the continued survival and recovery of humpback chub and razorback sucker in the 

Grand Canyon. The Service should consider the long-term consequences of nonnative fish 

establishment in the canyons when making its jeopardy decision. 

98 Id. at E-11-E-12. 99 Id. at E-69. 100 Id. at E-12. 
21

VIII. Reclamation should consider the most effective and least invasive

means for preventing the establishment of smallmouth bass in the

Colorado River below Glen Canyon Dam.

The Pueblo of Zuni, the Hopi Tribe, and other tribes have expressed significant ongoing 

concerns regarding taking of life in the Marble and Grand Canyons. Specifically, the tribes 

oppose many, if not all, of the measures proposed by Reclamation to prevent the 

establishment of smallmouth bass in the Colorado River downstream of Glen Canyon Dam. 

Given these concerns, we strongly encourage Reclamation and other partners to prioritize 

and elevate consultation with the Grand Canyon affiliated Tribes to understand their 

interests, consider alternate solutions that do not conflict with their culture and values, and 

do so in a way that allows adequate time and engagement to ensure meaningful consultation 

and to influence outcomes. This consultation should be ongoing, not just during the Draft 

SEIS process, including during planning, design and implementation of actions related to 

preventing the establishment of nonnative fish in the Grand Canyon, and should include 

travel to respective reservations to reduce barriers to conversation and consultation. Further, 

preventative methods—such as creating a barrier in Lake Powell to ensure nonnative species 

do not pass through the dam—have long been advised as an action Reclamation could take 

that may not conflict with the values of and cause harm to tribes and Native communities. 

We strongly recommend that these proactive solutions be expedited and prioritized to carry 

out the agency’s trust responsibility to the tribes and Native communities with ties to the 

Colorado River and its canyons. 

The Trust appreciates the opportunity to comment on this Draft SEIS. The Trust supports a 

decision by Reclamation to implement the proposed cold-water alternatives and to modify 

the sediment accounting window for high flow experiments to facilitate more frequent and 

naturally timed high flows in Marble and Grand Canyons. Ideally, HFEs would be timed with 

flow spikes where possible to create benefits for sediment resources and address smallmouth 

bass spawning. We believe that under the urgent circumstances these short-term cold-water 

alternatives will provide additional tools for Reclamation to prevent spawning and 

establishment of nonnative species in the Grand Canyon and it is important to have all tools 

available. The failure to act—on this threat to the largest population of humpback chub in 

the basin and to numerous other native fish that have found refuge from nonnative 

predation and competition in the Grand Canyon—will over the long term diminish and 

likely destroy the successful recovery of the remaining assemblage of Colorado River native 

fish and may doom their survival. Further, we believe modifying the sediment accounting 

window will restore the opportunity and frequency of high flow events in Grand Canyon 

under low reservoir conditions, which will help restore natural processes such as spring peak 

flows, transport and redistribute sediment throughout the canyons, build sandbars, and 

provide sand to protect archaeological sites. 

We look forward to working with you to integrate this solution with the larger challenge of 

sustainable management of the Colorado River Basin. 
22

Sincerely, 

Jen Pelz 

Water Advocacy Director 

Grand Canyon Trust