United States Department of the Interior

FISH AND WILDLIFE SERVICE

Post Office Box 1306

Albuquerque, New Mexico 87103

In Reply Refer To: 

FWS/R2/ES-ARD/ 080647 

Kathleen Callister

LTEMP SEIS Project Manager

Bureau of Reclamation, Upper Colorado Basin 

125 South State Street, Suite 800 

Salt Lake City, Utah 84138 

Dear Ms. Callister: 

The U.S. Fish and Wildlife Service (Service) appreciates this opportunity to comment on the 

Bureau of Reclamation’s (Reclamation) Glen canyon Dam Long-Term Experimental and 

Management Plan (LTEMP) Draft Supplemental Environmental Impact Statement (SEIS) as 

announced in the Federal Register on Feb 9, 2024 (89 FR 9147). The Service has prepared 

comments to address issues related to this action and its compliance with the Endangered Species 

Act of 1973 (16 U.S.C. et seq.) (ESA), as amended. The Service previously provided comments 

during the January 2024 Cooperating Agency review and appreciates the significant work 

Reclamation has completed to incorporate, address, and respond to those comments. 

We are at a critical juncture in time to prevent the establishment of smallmouth bass 

(Micropterus dolomieu) and other warm water invasive fish species downstream of Glen Canyon 

Dam in the Colorado River. As you are aware, approximately 90% of all known federally listed 

humpback chub (Gila cypha) occur within the Grand Canyon reach of the Colorado River. The 

Service recently downlisted the humpback chub from “endangered” to “threatened” (86 FR 

57588; November 17, 2021) due to the population of humpback chub below Glen Canyon Dam 

being mostly free of impacts from predatory nonnatives as well as the commitment to invasive 

fish removal efforts in the Upper Basin, including flow alterations at the Upper Basin dams. 

Establishment of warm water predatory nonnative invasive fish within the Grand Canyon reach 

would constitute a significant new threat to humpback chub. Consistent with the Department of 

the Interior’s 2021-2025 Invasive Species Strategic Plan, it is imperative to address invasive 

species while they are early in the invasion process to prevent full establishment and spread (U. 

S. Department of Interior 2021). The Service sent Reclamation letters on September 27, 2023,
Kathleen Callister, LTEMP SEIS Project Manager 2

and January 12, 2024, expressing our concerns about smallmouth bass establishment and the 

urgency of addressing this issue. 

The Service has documented how quickly smallmouth bass can invade, become established, and

impact federally listed aquatic species, from their invasion in the Upper Colorado River (Breton 

et al. 2014). It took less than 5 years following the initial invasion in 2002 for smallmouth bass to 

become established in hundreds of miles of river in the Upper Colorado River basin (Haines and 

Modde, 2007). Similar smallmouth bass invasion and impacts patterns are documented 

worldwide by Loppnow et al. (2013), who noted that management agencies have been mostly 

unsuccessful controlling these invasive fish, that eradication has not been successful even when 

expensive and intensive techniques were used, and that an important part of control should 

emphasize efforts to prevent smallmouth bass introductions. There is evidence from the Upper 

Colorado River Endangered Fish Recovery Program (UCREFRP) that smallmouth bass cannot 

co-exist with native fish species (Bestgen and Tuttle, 2022). The UCREFRP reports that in areas 

where smallmouth bass are present they observe no native juvenile or subadult chub species, 

postulating that predation from smallmouth bass halts recruitment of those native fish species. 

The UCREFRP views smallmouth bass as the primary nonnative predator in the basin and as a 

result, smallmouth bass are the focus of the vast majority of removal efforts. The program spends 

more than $2 million annually in removing smallmouth bass and even with those targeted efforts 

they continue to see smallmouth bass populations increase or remain stable (Breton et al 2015, 

UCREFRP annual reports at www.coloradoriverrecovery.org/uc).

Smallmouth bass populations in the Grand Canyon reach are currently small and geographically 

confined in a relatively small section of river. Previous invasion patterns suggest that the window 

to eradicate invasion is closing. Many partners are invested in our native fish recovery programs 

in the Colorado river, and the humpback chub downlisting exemplifies those efforts and 

partnerships. Smallmouth bass establishment in the Lower Colorado River could reverse those 

accomplishments within a short timeframe as occurred in the Upper Colorado River basin. It is 

essential that all Colorado River agencies and partners take all possible actions as frequently as 

possible in 2024 to prevent the establishment of smallmouth bass in the Lower Colorado River, 

including responding swiftly to bass detections and monitoring the effectiveness of actions taken. 

Implementing the most effective alternative(s) from the LTEMP SEIS will be critical in creating 

conditions that disrupt or prevent spawning to prevent smallmouth bass establishment. 

The attached excel spreadsheet contains 91 unique comments. For ease of review, the comments 

have been color coded into categories: 19 editorial comments (grey), 43 clarifying comments 

(green), and 29 substantive comments (orange). The clarifying comments are typically seeking 

additional information to explain the "why" behind a conclusion drawn and not necessarily 

requesting a change in the conclusion. Some substantive comment themes are summarized

below. 

Smallmouth Bass Flow Alternatives Population Growth Rate Model 

The Service is pleased at the incorporation of the Eppehimer and Yackulic smallmouth bass 
Kathleen Callister, LTEMP SEIS Project Manager 3

model in Appendix A assessing the potential for smallmouth population growth rate under each 

of the flow alternatives. The Service recommends expanding these discussions within the SEIS 

to provide more context and understanding for the reader on what the lambda values mean and 

how to compare them for effectiveness across the different flow alternatives. This model is the 

most powerful tool available to interpret and evaluate potential success of the alternatives and 

needs to be presented in a way that is simple for readers to understand, such as in tabular format. 

The Service also suggests asking the authors to add an analysis where they compare the lambda 

of each flow alternative using only the hydrological traces where a flow alternative would be 

triggered due to anticipated river temperatures. Breaking out lambda values specifically for the 

years in which the temperature is modeled to be above the trigger of 15.5 degrees Celsius will 

help to better tease out the effectiveness of each flow alternative and allow a better comparison 

across alternatives. As currently analyzed, an alternative flow option will only be triggered in 17 

percent of the 30 modeled hydrological traces; no alternative flows would be triggered in 83 

percent of the modeled scenarios. The high percentage of hydrological models that would not 

trigger an alternative flow swamps out the effectiveness of each modeled flow alternative in the 

hydrological scenarios where a flow would be triggered. Adding an analysis that removes the 

excess signal will more clearly demonstrate which flow alternatives meet the purpose and need. 

At the current scale it is very difficult to tell if adding a flow spike(s) adds any additional 

effectiveness as compared to the same flow alternative without flow spike(s). This information 

also needs to be added to the summary table in Chapter 2. 

Purpose and Need

The draft SEIS defines the need as “to disrupt the establishment of smallmouth bass below Glen 

Canyon Dam by limiting additional recruitment, which could threaten populations of threatened 

humpback chub below the dam (page 1-6, section 1-4)”. The Service remains concerned that the 

Non-Bypass flow alternative does not meet this stated need. This alternative focuses on 

impacting the nest guarding behaviors of male smallmouth bass and reducing survivorship of 

eggs and fry. These impacts occur after a successful spawn and do not prevent spawning. The 

Eppehimer and Yackulic smallmouth bass population growth model indicates that the NonBypass flow option never reduces the smallmouth bass population growth below 1. In every 

modeled hydrological trace in which an additional flow option would be needed (17 traces), the 

Non-Bypass alternative appears to function equivalently to the No Action Alternative in terms of 

meeting the purpose/need of the SEIS. The model demonstrates that smallmouth bass would 

continue to recruit, and population would grow, and therefore establishment will still occur. The 

Service recommends removing the Non-Bypass flow option from further consideration as it does 

not meet the purpose and need of the SEIS, nor does it meet the needed management for the 

ecological issue stressing the stability of the humpback chub population. 

Preferred Alternative

It is unclear within the document if Reclamation is considering selecting one alternative from 
Kathleen Callister, LTEMP SEIS Project Manager 4

those analyzed or if multiple alternatives may be implemented under different scenarios. If one 

alternative will be selected, the Service strongly suggests using modeling to evaluate impacts to 

lambda as a way to prioritize alternatives based on effectiveness. The data presented in this SEIS 

demonstrate that only the Cool Mix and Cool Mix with Flow Spike are effective at reducing 

lambda below 1 under all hydrologic scenarios analyzed, suggesting this should be the preferred 

alternative as it best meets the purpose and need of the SEIS. 

If after this SEIS process Reclamation decides to maintain all 5 smallmouth bass flow 

alternatives as a "menu" of options for use, the Service strongly recommends running the 

smallmouth bass model for the particular hydrology presenting in any given year and limiting 

menu "choices" to only flow alternatives that reduce lambda to below 1 for that specific

hydrological scenario. Specifically, the Service recommends only implementing flow 

alternatives that are likely to reduce lambda to 0.96 or lower due to model uncertainties when the 

modeled lambda is very close to "1" in value. This could also be done to model hydropower 

costs of the different flow options for a given hydrological scenario in any given year where 

temperatures are anticipated to rise above the trigger of 15.5 degrees Celsius. If Reclamation is 

considering utilizing multiple alternatives, the Service encourages Reclamation to cooperatively 

develop any hybrid alternatives with the Service and other partners and to still prioritize options 

based on anticipated effectiveness during peak smallmouth bass spawning timeframes. It is 

essential to use the most effective alternatives to prevent establishment in 2024.

Timeframe

Currently the plan states that smallmouth bass flow alternatives would end in 2027. The 

document implies this decision is predicated on the assumption that other tools may be available 

that would be effective by 2027. However, given uncertainties the Service recommends 

extending the timeframe for allowing smallmouth bass flow alternatives to be implemented 

through the lifetime of the original LTEMP, in case other tools or options are not available by 

2027, or if other tools prove ineffective. If the smallmouth bass flow alternatives are effective, it 

will be important to be able to continue to implement them when needed to address smallmouth 

bass and the threat they pose to humpback chub. 

ESA Requirements 

There is a long consultation history between the Service and Reclamation involving operations at 

Glen Canyon Dam. A full list of consultations is on file in the Arizona Ecological Services Field 

Office. Consultation histories and summaries can also be found in the 2016 Biological Opinion 

for the LTEMP. In evaluating the various flow alternatives presented in the draft SEIS it appears 

that several alternatives may require re-initiation of Section 7 consultation. For example, the low 

flows associated with the Non-Bypass Alternative (2,000 cfs) are well below the flows analyzed 

in current ESA compliance documents for the LTEMP and are reminiscent of hydropeaking 

flows from the 1990’s. Hydropeaking does disadvantage the early life history stages of fish, 

however that disadvantage affects all fish species. Data from that time (see 1995 EIS and 2016 

LTEMP EIS) demonstrated negative impacts to federally listed native fish species, particularly if 
Kathleen Callister, LTEMP SEIS Project Manager 5

those flows occur during the spawning season of native fish and/or their macroinvertebrate prey. 

Further, the 2016 Biological Opinion analyzed up to two High Flow Experiments annually and 

up to 38 HFEs over the 20-year LTEMP period. If the various flow alternatives could result in 

more High Flow Experiments in a given year or over the lifetime of the LTEMP that may not be 

analyzed in existing consultations. If Reclamation chooses to implement such flows, Section 7 

consultation would likely need to be reinitiated and would likely need to include updates to the 

baseline for humpback chub. 

Monitoring 

The preliminary draft SEIS contains many assumptions based on smallmouth bass detections 

and/or other sampling efforts that would need to occur in conjunction with the various 

alternatives as well as scenarios where flow alternatives may be curtailed or halted. The Service 

would like additional information about how those decisions will be made and if there will be 

input from cooperating agencies. As we enter into Glen Canyon Dam Adaptive Management 

Working Group (AMWG) Triennial Work Planning, time is of the essence to ensure sampling 

and removal efforts are prioritized and fully funded. The Service also strongly recommends 

monitoring of the effectiveness of implementing any flow alternatives. 

Conclusion 

Thank you again for the opportunity to comment on this important issue. The Service recognizes 

the breadth of challenges facing Reclamation as you work to balance water demand and water 

availability, federally listed species and habitat needs, and dam safety and integrity. The Service 

continues to believe that it is critical that all Colorado River partners do everything possible to 

prevent the establishment of smallmouth bass in the Lower Colorado River. It is essential that 

agencies and partners swiftly respond to bass detections and monitor the effectiveness of actions 

taken to remain flexible in approaches and respond nimbly to changing conditions. Completing 

this process by late spring 2024 is imperative to prevent smallmouth bass establishment below 

the Glen Canyon Dam to protect native and federally listed fish when river temperatures increase 

above 15.5 degrees Celsius. The Service encourages Reclamation to act with urgency to identify 

the most effective tools starting in June 2024 to mitigate invading smallmouth bass populations 

close to Glen Canyon Dam. The Service recognizes that Western Area Power Administration

recently submitted additional modeling for consideration. The Service believes the current 

document contains sufficient information in the existing draft and urges Reclamation to complete 

the SEIS on the timeline agreed to during Cooperator Agency calls. The Service stands 

committed and ready to assist Reclamation with all phases of this SEIS and the other concurrent 

NEPA planning processes. Please include the Service as early as possible so that we can provide 

input and be responsive to time intensive aspects of project requirements. 
Kathleen Callister, LTEMP SEIS Project Manager 6

If we can be of further assistance, please contact Jonna Polk, Assistant Regional Director, 

Ecological Services, at Jonna_polk@fws.gov or 918-408-0850. If you need any further 

clarification of our comments, please contact Deborah Williams, Colorado River Special 

Assistant, at Deborah_williams@fws.gov or 575-517-6091. 

Sincerely,

Regional Director

Enclosure 
Kathleen Callister, LTEMP SEIS Project Manager 7

cc: Paul Souza, Region 8 Regional Director, Business Office paul_souza@fws.gov

Matt Hogan, Region 6 regional Director, Business Office matt_hogan@fws.gov 

Bureau of Reclamation General Email for LTEMP SEIS LTEMPSEIS@usbr.gov

Wayne Pullan, Upper Colorado Regional Director WPullan@usbr.gov 

William Stewart, LTEMP SEIS Project Co-Manager WStewart@usbr.gov 
Kathleen Callister, LTEMP SEIS Project Manager 8

Literature Cited

Bestgen, K. R., and D. Tuttle. 2022. Evaluating effects of non-native predator removal on native 

fishes in the Yampa River, Colorado. Project 140 annual report submitted to the Upper 

Colorado River Endangered Fish Recovery Program, Denver, Colorado. Department of 

Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins. Larval 

Fish Laboratory. 

Breton, A. R, D. L. Winkelman, J. A. Hawkins, and K. R. Bestgen. 2014. Population trends of 

 smallmouth bass in the upper Colorado River basin with an evaluation of removal effects. 

 Final report to the Upper Colorado River Endangered Fish Recovery Program, Denver, 

 Colorado. Larval Fish Laboratory Contribution 169. 

Breton, A. R, D. L. Winkelman, K. R. Bestgen, and J. A. Hawkins. 2015. Population dynamics 

 modeling of introduced smallmouth bass in the upper Colorado River basin. Final report 

 to the Upper Colorado River Endangered Fish Recovery Program, Denver, Colorado. 

Larval Fish Laboratory Contribution 186. 

Haines, G. and T. Modde. 2007. A review of smallmouth bass removal in Yampa Canyon, with 

notes on the simulated effort needed to reduce smallmouth bass in the Green River 

subbasin. Final Report to the Upper Colorado Endangered Fish Recovery Program. 

Loppnow, G. L., K. Vascotto, and P. A. Venturelli. 2013. Invasive smallmouth bass 

(Micropterus dolomieu): history, impacts, and control. Management of Biological 

Invasions 4:191–206. 

U. S. Department of Interior. 2021. Invasive Species Strategic Plan 2021 - 2025. Pages 1–54. 

Washington, D.C., United States. 
USFWS 

Comment 

Color:

Editorial 

Comment 

(typos)

Clarifying 

Comment - 

we are asking 

for a 

correction or 

addition of 

more info to 

give better 

context to 

statement

Substantive 

Comment

Cmt # Section # Page #

Table or 

Figure # Comment Response (reviewers leave blank)

1 Entire

Please add a description of what the lambdas mean and how to compare them across the different 

SMB flow alternatives. There is no context in the document to help a reader who is not already 

involved in lambda type discussion to understand how to interpret the information being presented 

and its value in decision making. It is the most powerful success based tool in the document but isn't 

presented as such. Also this information needs to be added and highlighted in the summary table. A 

lambda over 1 indicates that this alternative fails to limit additional recruitment of SMB which could 

continue to threaten humpback chub below the dam.

2 Entire

Suggest emphasizing and repeating information on page 1-3 that in 20 years of mechanical removal 

of smallmouth bass in the upper basin there has been limited success in reducing smallmouth bass 

densities to benefit native fish populations.

3 Entire

The Need is to disrupt the establishment of smallmouth bass below Glen Canyon Dam by limiting 

additional recruitment, which could threaten populations of threatened humpback chub below the dam 

(page 1-6, section 1-4). A lambda over 1 indicates that this alternative fails to limit additional 

recruitment of SMB which could continue to threaten humpback chub below the dam. The Non 

Bypass option does not meet this stated need of the SEIS. The population growth model indicates 

that in every modeled hydrological trace in which temperatures would indicate that an additional flow 

option would be needed, the modeled lambda (population growth) is still above 1 for all 17 traces. 

This is the same overall result of the No Action Alternative. This result indicates that in all of the 

modeled traces where a flow option would be needed, the smallmouth bass would continue to recruit 

and population would grow. This result does not meet the need of the SEIS, nor does it meet the 

ecological needs of the issue. The Service recommends removing this option from further 

consideration as it does not meet the purpose and need of the SEIS. The Non bypass alternative also 

does not address or provide the needed management for the ecological issue stressing the stability of 

the humpback chub population. 
4 Entire

Recommend adding an analysis where you look at the effectiveness of lambda only in the years 

where a an additional flow option is triggered due to anticipated temperatures. This will help to better 

tease out the effectiveness of each tool and allow a better comparison across tools. As currently 

analyzed, an alternative flow option will only be triggered in 17 percent of the 30 modeled hydrological 

traces; no alternative flows would be triggered in 83 percent of the modeled scenarios. The high 

percentage of hydrological models that would not trigger an alternative flow swamps out the 

effectiveness of each modeled flow alternative in the hydrological scenarios where a flow would be 

triggered. Adding an analysis that removes the excess signal will more clearly demonstrate which flow 

alternatives meet the purpose and need. Further breaking out lambda values specifically for the 

years in which the temperature is modeled to be above the trigger of 15.5 degrees Celsius will better 

tease out alternative effectiveness. At the current scale it is very difficult to tell if adding a flow 

spike(s) adds any additional effectiveness as compared to the same flow alternative without flow 

spike(s).Further, this will affect the hydropower cost analysis associated with each flow alternative. 

Finally at the scale as described in the current analysis it's very difficult to tell if adding a flow spike(s) 

is needed or adds additional effectiveness as compared to the same flow alternative without flow 

spike(s). This information also needs to be added to the summary table in Chapter 2.

5 Entire

If after this SEIS process Reclamation decides to maintain all 5 SMB flow alternatives as a "menu" of 

options for use, the Service strongly recommends running the SMB model for the particular hydrology 

presenting in any given year and limiting menu "choices" to ONLY flow alternatives that reduce 

lambda to below 1 for that given hydrological scenario. Specifically, the Service recommends only 

implementing flow alternatives that are likely to reduce lambda to 0.96 or lower due to model 

uncertainties when the modeled lambda is very close to "1" in value. This could also be done to model 

hydropower costs of the different flow options for a given hydrological scenario in any given year 

where temperatures are anticipated to rise above the trigger of 15.5 degrees Celsius. If Reclamation 

is considering utilizing multiple alternatives, the Service encourages Reclamation to cooperatively 

develop any hybrid alternatives with the Service and other partners and to still prioritize options based 

on anticipated effectiveness during peak smallmouth bass spawning timeframes. It is essential to use 

the most effective alternatives to prevent establishment in 2024.

6 Entire

Currently the plan states that smallmouth bass flow alternatives would end in 2027. The document 

implies this decision is predicated on the assumption that other tools may be available that would be 

effective by 2027. However, given uncertainties the Service recommends extending the timeframe for 

allowing smallmouth bass flow alternatives to be implemented through the lifetime of the original 

LTEMP, in case other tools or options are not available by 2027, or if other tools prove ineffective.

If 

the smallmouth bass flow alternatives are effective, it will be important to be able to continue to 

implement them when needed to address smallmouth bass and the threat they pose to humpback 

chub.

7 Entire

The SEIS lacks an analysis in the effects section to native and non-natives fish based on the lambda 

modeling (pp3-85 to 3-96). The effects analysis does not appear to have been updated following the 

addition of the lambda modeling. The effects analyses should also include effects to native fish if the 

flow alternative is not likely to be successful in years where the temperature modeling indicates 

temperatures will rise above 15.5 degrees celcious and trigger that flow alternative. A less effective 

alternative will allow population growth of smallmouth bass and have negative impacts to native fish. It 

looks like it was all written before the lambda modeling and didn't get it incorporated into the effects at 

all. 
8 Entire

Completing this process by late spring 2024 is imperative to prevent smallmouth bass establishment 

and to protect native and federally listed fish by having the most effective tools available when river 

temperatures increase. Reclamation should avoid any delays to this process that would result in the 

loss of the opportunity to use the most effective tools starting in June 2024. If there are delays or we 

don’t select the most effective tools; we will lose a year and lose the advantage of the invading 

population having a restricted distribution close the dam. Many of these tools will be less effective the 

longer we wait to use them. 

9 Entire

Suggest updating references used throughout the document. There is a lot of newer peer reviewed 

information that can be incorporated. Suggest coordinating with GRMRC and NPS to get updated 

references.

10 2 2-3

Statement that river mile targets for implementation could vary depending on where bass are located 

could use more specifics or an example to be fully understood. It would be helpful if a realistic 

example were provided regarding how this may be exhibited.

11 2 2-3 Missing Space in Header Title

12 2 2-4

GCD Operational constraints - the modeling assumed a minimum flow of 2,000 cfs through the 

penstocks in every flow alternative. In a public webinar it was shared that this operational constraint 

may be increased to 3,500 cfs based on recommendations from an upcoming cavitation report. If the 

operational constraint gets increased the Service recommend re-running the SMB lambda model to 

investigate if that operational constraint has any modeled impact to the likelihood of success (defined 

as reducing the lambda to below 1) for hydrological traces that would trigger a flow alternative.

13 2 2-10

Sentence regarding the endangered species status of humpback chub population requires a 

"because" statement. Indicating a causal mechanism here and the result would strengthen the 

argument.

14 2 2-17 Missing Space in Header Title

15 2 2-17

The description of the Non-Bypass Alternative states that it is centered on substantial river stage 

changes that are targeted along the Lees Ferry reach. That would correspond to the RM 15. The 

other flow options are analyzed for effectiveness at RM 15 and RM 61. Recent survey efforts have 

detected SMB all the way at the confluence of the Little Colorado River. Humpback chub 

congregations begin at RM 30. If this alternative is not designed to impact those locations it should 

not be considered as meeting the purpose and need of the SEIS. 

16 2 2-17

The document sites McKinney et al. 1999a in stating that the Non-Bypass Alternative "is predicted on 

the "flow fluctuations that reduced rainbow trout reproduction during the pre-ROD period (1965-1991) 

to the point where the fishery could only be maintained through stocking." What does this statement 

mean for potential impacts to rainbow trout and why?

17 2 2-20 2-1

Recommend adding statements to address how each of these alternatives will or won't be modified 

and effective at the two river miles analyzed throughout the rest of the document (RM 15 and 61). A 

reminder of the RM's where SMB have been recently detected would be helpful to the reader. 

18 2 2-23 2-2

This table is not congruent with all the information presented in the rest of the document and needs to 

be thoroughly reviewed and updated. It should include the SMB lambda information as that is the 

most significant data to help compare the effectiveness of the different alternatives. Also for those 

modeled traces where an alternative flow would be needed, the table should also reflect and 

summarize what the impacts of the positive lambdas means for all the species and resources 

analyzed in this SEIS.

19 2 2-25 2-2

Recommend adding details in this document validating and demonstrating how the Non-Bypass 

Alternative "could allow the area's landscape character to appear more natural". This statement 

appears to be unsupported.
20 2 2-26 2-2

Recommend adding details within this document that supports and validates the conclusion that small 

mouth bass spawning could be disrupted while not impacting native fish spawning. Data suggests 

that native fish occur and spawn at RM 30 and SMB occur and spawn all the way to RM 61. Also 

suggest adding modeled lambda information and explanation that demonstrates that in years where a 

tools would be warranted that this tool would actually impact lambda and reduce modeled population 

growth to below 1. Please add substantive information supporting the conclusion that the Non Bypass alternative would not impact aquatic food base items in the Lees Ferry and Marble Canyon 

areas. This document later states that these areas have the highest aquatic invertebrate food 

production of the river between GCD and Hoover dam. Please add information on potential impacts 

to rainbow trout to this table.

21 2 2-27 2-2

Recommend adding details in the Special Status Species section on the modeled lambda 

effectiveness of each alternative in the hydrologic traces that indicated a flow alternative would be 

needed. This is needed to adequately compare the analysis. Additionally, add information explaining 

what will likely happen in those years/traces where the lambda stays above 1. Also in the document it 

appears that this section may actually be sub header "Threatened and Endangered Species" and not 

"Special Status Species"

22 2 2-28 2-2

Recommend adding information to indicate if the economic analyses are run representing any given 

year a flow alternative is needed or if they are run as if a flow alternative is needed in every given 

year.

23 3 3-3 Editorial strikethrough should be removed in 3.2.2

24 3 3-14

The Non-Bypass Flow Alternative section references research flows from the early 1990's where 

flows as low as 1,000 cfs, is there anything that we learned from those research flows that we should 

be referencing and including in the descriptions of potential impacts of these flows on aquatic 

resources?

25 3 3-22 Editorial spacing error in impact analysis area - word "these"

26 3 3-50

The first paragraph of the macroinvertebrate section implies that the highest macroinvertebrate 

production below GCD occurs in the GCD reach. The next paragraph indicates that cold water can 

prevent eggs from hatching and limit success - recommend adding what temperature these impacts 

are related to. The paragraph continues to state that varial zone increases associated with 

hydropower production leads to desiccation-induced mortality of eggs. This information should be 

described appropriately in impacts analyses of the appropriate flow alternatives and added to the 

summary table (Kennedy 2016).

27 3 3-51

The section also states that Kennedy (2016) hypothesizes that dam operations may constrain 

abundance of aquatic insects...thereby limiting amount of prey available for native fish. How does 

this conclusion align with the Non-Bypass alternative, could there be even greater impacts to 

macroinvertebrates? Please explain this further and update summary table as appropriate.

28 3 3-51

Please add more information about findings of the "bug flows" and if food base was enhanced by 

steadier flows.

29 3 3-54

Food Web Dynamics section - recommend expanding the analysis describing potential effects of 

fluctuating flows from power plant releases and the results of "bug flows". The section has one 

statement concerning a 400 percent increase in caddisflies but minimizes that increase as it could 

have been due to low sediment or steady flows. Expand this section to support that conclusion but 

also demonstrate that the steady flows may have caused a 400 percent increase (this is not stated). 

Recommend adding analysis of what this data may mean when considering non bypass alternative 

flows and potential impacts to the food web in the most productive section of the river below GCD, 

where these flows will impact the varial zone during macroinvertebrate production peak times. Please 

include these risks in the summary table.
30 3 3-59

Flannelmouth sucker Life History - any conclusions about the variability reported by long-term fish 

monitoring by AZGFD and catch per unit effort? The document describes some significant variability 

among years. Are there any hypotheses on what might be driving that inter-year variability and 

therefore are there any potential connections to the different flow alternatives being analyzed?

31 3 3-63 3-30

Please add a column to this table indicating the Threat Levels per non-native fish as identified in the 

NPS 2013a Comprehensive Fisheries Management Plan. This would help the reader understand the 

magnitude of concern associated with each species in this table. Also consider adding a column 

indicating the prey base of the species and/or it's piscivorous nature.

32 3 3-63 3-30 Several spacing issues between words throughout this table in the Presence in Project Area column.

33 3 3-69

Please add clarifying information in the "Proposal to Manage Smallmouth Bass in the Grand Canyon" 

section on whether each of the flow alternatives can be adapted (or can't be) to be effective at both 

RM 15 and RM 61. From reading the flow alternatives description it doesn't sound like the Non 

Bypass Alternative could impact SMB all the way to RM 61. Where does the trough attenuate? Also 

please include description here about the modeled lambdas for each flow alternative and 

communicate what those values mean for the reader and how effective flows will be in the individual 

modeled traces where a flow alternative is triggered.

34 3 3-75

Brown Trout section - The Runge 2018 cited paper concludes that brown trout management flows will 

not be an effective strategy - extrapolating from that conclusion - please explain why or why not the 

same types of flows (the non-by-pass alternative) is anticipated to be effective for SMB. Also please 

update the incentivized harvest section with the most recent data. This can be found in notes from 

Jeff Arnold's presentations to AMWG and the TWG.

35 3 3-81 Mis-spelling of "few" and "trout" in first paragraph on page.

36 3 3-82 Font issue in second paragraph.

37 3 3-85

Recommend expanding this entire section to better explain what the lambdas in Appendix A mean in 

terms of comparing the various alternatives. Add a description of what the lambdas mean and how to 

compare them across the different SMB flow alternatives. There is no context in the document to help 

a reader who is not already involved in lambda type discussion to understand how to interpret the 

information being presented and its value in decision making. It is the most powerful success based 

tool in the document but isn't presented as such. Recommend adding an analysis where you look at 

the effectiveness of lambda only in the years where a an additional flow option is triggered due to 

anticipated temperatures. This will help to better tease out the effectiveness of each tool and allow a 

better comparison across tools. Breaking out lambda values specifically for the years in which the 

temperature is modeled to be above the trigger of 15.5 degrees Celsius will help to better tease out 

the effectiveness of each flow alternative and allow a better comparison across alternatives. As 

currently analyzed, an alternative flow option will only be triggered in a few of the 30 modeled 

hydrological traces, leading to SMB population growth on anticipated in a no action alternative in 17 

percent of the traces. This means in 83 percent of all the modeled hydrological scenarios, no 

alternative flow would even be triggered. This can swamp out clearly demonstrating the effectiveness 

of each modeled flow alternative. Removing the excess signal will more clearly demonstrate that 

some flow alternatives do not meet the purpose and need of the SEIS. Further, this will affect the 

hydropower cost analysis associated with each flow alternative. Finally at the scale as described in 

the current analysis it's very difficult to tell if adding a flow spike(s) is needed or adds additional 

effectiveness as compared to the same flow alternative without flow spike(s). 

38 3 3-86

Please explain how warmer water releases under the no action alternative could increase growth 

rates of rainbow trout and/or place that information in context of overall concerns of warmer waters 

decreasing trout populations.
39 3 3-86

The Nonnative and native fish paragraphs seem inaccurate for the no action alternative and read 

more like response to flow increases.

40 3 3-87 The paragraph on Spring HFE seems out of place in a section on the No Action alternative.

41 3 3-88

Recommend additional emphasis on pointing out that the cool mix alternative is the only flow 

alternative in which the modeled lambda is always below 1 no matter what hydrological trace is used 

in the model and how that relates to its anticipated effectiveness. This is clearly the most effective 

flow alternative analyzed in terms of meeting the purpose and need. A lambda over 1 indicates that 

this alternative fails to limit additional recruitment of SMB which could continue to threaten humpback 

chub below the dam. In general explaining lambda in plain language will help readers less familiar 

with the subject matter understand the science being presented.

42 3 3-89

If the model anticipates that cooling can be accomplished to RM 15 or RM 30, what about RM 61 and 

if it's not to RM 61 then why are all the economic analyses carried to RM 61? This is internally 

inconsistent and confusing and should be addressed. Later sections of this chapter indicate that 

cooling can be achieved at RM 61.

43 3 3-89

In the cool mix with flow sike alternative section please correct the phrase "cold release" to "cold 

spike" for clarity. 

44 3 3-90

Please explain the SMB lambdas further in this section. If you limited the analysis to just hydrological 

traces where a flow alternative would be triggered - is there any modeled difference in success 

between cold mix and cold mix with a flow spike? Breaking out lambda values specifically for the 

years in which the temperature is modeled to be above the trigger of 15.5 degrees Celsius will help to 

better tease out the effectiveness of each flow alternative and allow a better comparison across 

alternatives.

45 3 3-91

Strongly recommend adding some information for the reader to help interpret the difference in the 

lambdas between the cool mix and cold shock alternatives. This is important both in giving context of 

modeled effectiveness but also in understanding differences in other potential negative impacts of the 

two alternatives, including the increase in risk of SMB population growth. Add analysis and 

explanation that breaks out lambda values specifically for the years in which the temperature is 

modeled to be above the trigger of 15.5 degrees Celsius - this will help to better tease out the 

effectiveness of each flow alternative and allow a better comparison across alternatives.

46 3 3-92

The aquatic food base section details anticipated negative impacts to the aquatic food base 

associated with magnitude of releases and the persistence of those impacts weekly for 12 weeks. 

These same effects should be in the Non-By Pass alternative based on velocities, number of weeks 

and repetitive nature of that alternative.

47 3 3-92

Please add how many spike flows are anticipated. The Cool Mix section states that "up to 3 cold 

shocks" may occur.

48 3 3-93

Describe any measurable difference in the modeled lambda for the cold shock with spike flow 

alternative that would justify including spike flows in addition to the cold shock given the potential 

negative impacts associated with the spike flows. Limiting the lambda analysis to just hydrological 

traces where a flow is actually triggered may help to elucidate those differences such that they can be 

better described.

49 3 3-94

The Non Bypass Alternative is described as an "experiment" and according to the SMB model and 

associated lambdas - this alternative performs no better than the no action alternative. All associated 

lambdas are above 1 in all of the hydrological traces in which a flow alternative would be triggered for 

the 30 hydrological regimes analyzed. Therefore, the Service does not believe that this alternative 

meets the Purpose and Need of this LTEMP SEIS and recommends it be removed from further 

consideration. 
50 3 3-95

The Non By-Pass Alternative was designed with low flows down to 2,000 cfs. With the new potential 

operational restrictions of maintaining penstock flows at least 3,000 cfs or perhaps even 3,500 cfs; 

how would those guidelines affect the modeled lambdas?

51 3 3-95

The "triggers" for initiating a Non-By-pass flow appear to be different from the triggers for the other 

flow alternatives. This description ties the temperature trigger to 12 mile slough and reads as if written 

by a different author. Recommend ensuring the trigger for a flow alternative is the same for all 

alternatives.

52 3 3-96

The potential impacts to Aquatic Food Base paragraph should be coordinated with species expert Ted 

Kennedy as on face value it does not seem to account for all the potential impacts as outlined in 

previous sections of the SEIS.

53 3 3-105

Based on the Amphibian and Reptile section, would the Non-By-pass alternative potentially cause any 

desiccation of amphibian eggs? If yes please add this to the analysis. If no please explain why those 

potential impacts are not expected.

54 3 3-114 Humpback chub section has repeated words on one sentence (river flows).

55 3 3-116 3-29 Font/spacing issue in figure heading.

56 3 3-117 3-30 Font/spacing issue in figure heading.

57 3 3-118 3-31 Font/spacing issue in figure heading.

58 3 3-118 3-31

In figure caption or in text please describe the "buffer" that is identified in the legend. Also please add 

confidence intervals to the caption.

59 3 3-123

In Distribution and Abundance section please add information on recently augmented populations of 

razorback sucker in GCNP

60 3 3-123

Please add information in this first paragraph indicating temperature effects at various RM along the 

river. These impacts are not equal.

61 3 3-131 Section

For the entire section of Issue 2 - recommend adding context of the lambda analysis for the different 

flow alternatives as described in other comments. Give context to what lambda means, how many 

traces actually would trigger a flow alternative and then the difference in the modeled ability of an 

alternative to impact lambda within a trace in which it is triggered. This will give the reader better 

context for understanding the effectiveness of the different alternative. Breaking out lambda values 

specifically for the years in which the temperature is modeled to be above the trigger of 15.5 degrees 

Celsius will help to better tease out the effectiveness of each flow alternative and allow a better 

comparison across alternatives. Please also add analysis explaining the differences in risks for those 

traces where a flow alternative would be triggered but lambda stays above 1. This will help the reader 

understand the difference in the continued threat of SMB establishment per alternative. Also please 

add information explaining how quickly bass can become established (as compared to other 

nonnative fish species). There is ample information from the Upper Basin Recovery programs that 

can be provided upon request demonstrating establishment in less than 5 years. This could also be 

done to model hydropower costs of the different flow options for a given hydrological scenario in any 

given year where temperatures are anticipated to rise above the trigger of 15.5 degrees Celsius.

62 3-132

Low water temperature swimming impairment is described here. It would be helpful to know the extent 

of this effect. For instance, can there be a proportion or other value be provided that would indicate 

how many young fish may be impacted?

63 3 3-133

Here impacts of cold shock are suggested to be less due to distance from the dam. Can there be a 

value applied, roughly or estimable, that would demonstrate this pattern? Without data or citation this 

statement appears to be arbitrary.
64 3 3-134

Add any potential impacts to humpback chub egg and fry from the Non-Bypass Alternative. There is 

a congregation of humpback chub at RM 30 that does not appear to have the impacts to their fry and 

eggs analyzed at all. The non bypass alternative anticipates up to 26 big fluctuations between MayOct. It doesn't look like the fluctuations dissipate by the 30 mile humpback chub aggregation. Impacts 

to these fish, eggs and fry need to be analyzed and are not analyzed in any existing consultations. 

65 3 3-135

The following quote/conclusion does not seem to be supported by Appendix A (Figure 1): "The 

alternatives with the most potential effect for disrupting smallmouth bass spawning are the Cool Mix 

with Flow Spike and the Cold Shock with Flow Spike Alternatives; this is because these alternatives 

disrupt both the physical habitat of smallmouth bass nesting and the suitable and necessary 

temperature regimes." In contrast, Appendix A suggests that it is the Cool Mix and Cool Mix with Flow 

Spike are the alternatives with the most potential effect. We recommend revising this statement so 

that it is congruent with Appendix A.

66 3 3-157 3-35 Font/spacing issue in figure heading.

67 3 3-161 3-37 Font/spacing issue in figure heading.

68 1.2 1-4

Add a definition of high-flow experiments for readers not familiar with the LTEMP. Consider 

summarizing the description of HFE in Section 3.4.1 on page 3-37. 

69 1.2 1-4 Add information about why BOR conducted the 3-day HFE in April 2023 for context.

70 1.2 1-5

Add what specific sediment conditions are you trying to improve in the Grand Canyon (i.e. transport 

from one area to another).

71 1.2 1-5 Define "sub-annual flow options."

72 1

This section needs a clearer definition of the project area versus the analysis area. If the analysis 

area is different for each resource, then define the analysis area for each resource somewhere in the 

document. 

73 1

It would be good to define the terms "sediment account period" and "implementation window" early on 

in the document. Consider adding some clarity on the purpose/need concerning the sediment 

accounting window. For a reader not familiar with the issues its confusing to seem to have to different 

"needs" for the SEIS.

74 1.3 1-6

Define the term "slough modifications," and either put the location of the slough on a map or provide a 

narrative description of the slough. 

75 2.6 2-11

The following sentence is very confusing to a reader not familiar with the issue. Consider re-phrasing. 

"To align with actual implementation without necessitating multiple weeks of hydropower maximization 

(that is, the operation of the hydropower system to generate the maximum amount of electrical power) 

within each month, daily bypass estimates from the smallmouth bass model were post-processed. 

Flows were simulated to occur all month, if they were triggered before the month’s halfway mark, and 

start in the subsequent month, if they were triggered after the halfway mark. Additionally, all days 

within a month would have bypass equal to the median of the month, with minimal changes observed 

in overall bypass across traces (USGS 2022)."

76 2.7 2-12 Explain the difference between an HFE and a flow spike. 

77 Figure 2-2

Is jet tube the same as river outlet works and the same as Bypass? If so, please select one term and 

try to use the same term throughout the document. 

78 3.2.2 3-16

This sentence is missing some words: "Overall elevation changes in Lake Powell under the action 

alternatives are relatively minor, and water."

79 3-56

A sentence is the first paragraph says that roundtail chub were extirpated from the Colorado River. It 

would be more accurate to say that the project area is outside the current and historic range of the 

species, according to the species status assessment. 

https://ecos.fws.gov/ServCat/DownloadFile/215366 
80 Table 3-29

Column 3. If you're going to name these places, please make sure they're on a map somewhere in 

the document, or otherwise described (such as RM #), so that the reader doesn't have to google the 

places. 

81 3.5.2

Consider adding information about the effects of the alternatives on the New Zealand mud snail 

population size and distribution. 

82 3.7.2 3-109 Correct header "species status species"

83 3.7.2 3-110

"HFE releases and flow spikes may enhance germination for certain riparian plant species and 

prevent establishment of other species, changing composition in ways that could have beneficial 

impacts on invertebrate biodiversity and abundance." Please provide a citation for this statement. 

84

3.7.2/specialstatus birds 3-113

This section says that the alternatives would affect none of the birds protected under MBTA, because 

these birds aren't in riparian areas. This is not correct. Many birds protected under MBTA nest in 

riparian areas. Please prove clarifying statement of the MBTA assemblage expected in this area. 

85 3.9.1 3-135

"If less electricity is unavailable at Glen Canyon Dam..." Change to "If less electricity is available at 

Glen Canyon Dam..."

86 3-143

Tables 3-36 

and 3-37

The titles of these tables say "5-year total emissions" of the pollutants, but these values aren't the 

total emissions. They appear to be the change in emissions compared to the No Action. Please revise 

as appropriate

87 3.11.2/Issue 33-161 Please explain why the concentration of 5.2 mg/L of DO is important. 

88 3.12.2 3-172

Please add additional clarifying language explaining the rationale behind the statement that the coldwater alternatives would have the same impacts as the No Action.

89 3.12.2 3-173

Please explain why aeolian transport of sand is important for cultural resources. Will it increase the 

area of sand bars, or decrease? 

90 3.12.2 3-173

Please add clarifying language explaining the rationale behind the statements that the alternatives 

would be similar to the No Action or one another, with regard to sediment transport. 

91 4.5 4-3

Please update the second paragraph - as currently written it does not accurately reflect where we are 

currently in consultation on this SEIS.