SOUND SCIENCE LLC

712 N. Eastridge Place

Boise, ID 83712

SOUND SCIENCE LLC

Task Order 140R4022Q0028 

IDIQ Contract # 140R3021D0010 

GCDAMP, TWG Non-Native Fishes Tabletop Exercise

April 12-13, 2022 

Draft Final Report

May 5, 2022 

Introduction Sound Science LLC facilitated a “tabletop exercise” as part of an online meeting of the Glen 

Canyon Dam Adaptive Management Program (GCDAMP) Technical Work Group (TWG) on 

April 12-13, 2022. The exercise was planned to provide the TWG with an opportunity to learn 

about and discuss a potential emergency resulting from escapements of non-native predatory fish 

through Glen Canyon Dam. This potential exists because falling reservoir levels in Lake Powell 

put warmer surface waters and their biota—including several non-native predatory fish species—

in increasing proximity to the intake (penstock) for the dam’s turbines. These conditions may 

enable escapements of living non-native fish through the dam. Any such escapements potentially

could result in these fish becoming established in the Grand Canyon ecosystem in Glen, Marble, 

and Grand Canyons and their tributaries, threatening endangered native fishes and the existing 

rainbow trout tailwater fishery.

The exercise focused mostly on potential escapements of two non-native fish species, 

smallmouth bass (Micropterus dolomieu) and, secondarily, green sunfish (Lepomis cyanellus). 

Both are native to eastern North America. Other non-native fishes present in Lake Powell and 

mentioned during the TWG meeting that have escaped or could escape through the dam and 

potentially threaten endangered native fishes and the rainbow trout fishery include walleye 

(Stizostedion vitreum) and gizzard shad (Dorosoma cepedianum), both also native to eastern 

North America.

As stated in the final exercise plan and agenda, the specific purpose of the exercise was to help 

the TWG identify areas of potential importance to the AMWG [Adaptive Management Work 

Group], concerning: (a) agency responsibilities for monitoring and responding to such events, 

(b) possible ways in which these agencies may respond to such events and ways in which these 

actions may affect the river and its canyons and biota, and (c) possible roles for the AMWG and 

its TWG in the decision-making process for such actions. 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 2

The TWG meeting and the exercise took place online, on the Webex meeting platform. The 

Bureau of Reclamation managed the technical aspects of the virtual meeting.

This report describes the exercise and summarizes its results under the three topics identified in 

the above statement of purpose, summarizes the results of a post-exercise, online survey of 

participants, and provides an overall summary of findings. 

The exercise participants found the exercise—and the presentations that preceded it in the 

meeting agenda—informative and useful. The participants also expressed concerns about: 

a. Agency capabilities to detect and report on non-native fish abundances and activity both 

above and below the dam quickly enough to guide management 

b. The identification of levels of abundance and patterns of activity that should be treated as 

triggering thresholds for reporting warnings or taking other management actions 

c. The processes through which federal agencies will make decisions on preventing or 

responding to escapements, or make decisions on water distribution and hydropower 

generation among the reservoirs in the Upper and Lower Colorado River Basins that in 

turn will affect the potential for escapements through Glen Canyon Dam 

d. The extent to which the federal agencies will consult with the AMWG and its TWG as 

parts of these decision-making processes 

e. Funding limitations at both the state and federal levels affecting monitoring efforts, 

potential actions to prevent escapements, and potential actions to respond to escapements 

f. The extent to which federal agencies will be able to consult meaningfully with the tribes 

on planned actions in the face of potentially urgent needs to respond to escapements 

g. Limitations at both the state and federal levels in the availability of equipment, personnel, 

and logistical capabilities for responding to escapements 

h. Limitations on the applicability and effectiveness of available mechanical and chemical 

methods for capturing/removing or killing/removing non-native fishes

i. A need to prioritize prevention over detection and reaction to escapements. 

Exercise participants noted that escapements of non-native predatory fish could erase the hardwon gains of recent decades in conserving the native fish species in the Grand Canyon 

ecosystem, and that failing to prevent or (as a less-desirable fallback) to contain such 

escapements would constitute an unacceptable systemic failure. TWG members also spoke about 

a need for a longer-term, holistic approach to managing the river and its ecosystem. Such an 

approach would need to consider the likely effects of climate change, continuing introductions of 

non-native species, and other factors that shape the Colorado River ecosystem. 

Exercise Design and Conduct TWG Chair Seth Shanahan, TWG Vice-Chair Michelle Garrison, Clarence Fullard with the

Bureau of Reclamation (Reclamation), and Emily Zmak with the Colorado Water Conservation 

Board began planning the Non-Native Fishes Tabletop Exercise in February 2022. David Braun 

and Robert Unnasch of Sound Science LLC joined the planning effort on April 6 after receiving 

a task order for the work under Reclamation IDIQ Contract # 140R3021D0010. Attachment I to 

this report presents the final agenda developed by this planning team, finalized on April 11. 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 3

Nine technical presentations on the topic of the exercise preceded the exercise in the TWG 

meeting agenda. These presentations significantly informed the discussions throughout the 

exercise: 

1. Basin Hydrology, Operations and Water Quality, Heather Patno, Reclamation

2. Lake Powell Water Quality Conditions, Robert Radtke, Reclamation 

3. Update on Glen Canyon Dam/Lake Powell Dissolved Oxygen State-of-Practice Project, 

Steve Hollenback, Reclamation

4. Smallmouth Bass Management in the Upper Colorado River Basin, Kevin Bestgen, 

Colorado State University 

5. Characterizing the Fish Assemblage of the Lake Powell Forebay: Identifying the 

Potential for Nonnative Fish Escapement through Glen Canyon Dam and into the Lower 

Colorado River, Phaedra Budy, Casey Pennock, Barrett Friesen, and Gary Thiede, Utah 

State University

6. Hydroacoustic Fish Distribution Lake Powell 2022, Mike Horn, Reclamation 

7. Glen Canyon Fish Escapement Options, Connie Svoboda, Reclamation 

8. Near-Term Threat of Smallmouth Bass Establishment below Glen Canyon Dam, 

Smallmouth Bass Task Force, presented by Kirk Young, Fish and Wildlife Service 

(FWS), and Charles Yackulic, U.S. Geological Survey-Grand Canyon Monitoring and 

Research Center (GCMRC)

9. NPS Rapid Response Compliance, High Risk Invasive Fish Concerns at Glen Canyon 

Dam in 2022, Rob Billerbeck, National Park Service (NPS)

Several of the presenters, other members of the Smallmouth Bass Task Force (see Presentation 

8), and other scientists from the GCMRC and NPS also participated in the exercise, contributing 

further to the deliberations. Their presentations are available through the GCDAMP and are not 

attached or summarized in this report. 

Tabletop exercises such as the one conducted during the April 2022 TWG virtual meeting 

typically present the participants with a hypothetical but plausible scenario—a specific set of 

initial conditions—for which they or their organization(s) would need to be prepared, either to 

prevent it from occurring or to detect and respond to it, if that scenario actually occurred. Such

exercises conventionally take place in the setting of a meeting, where the participants think their 

ways through (or “play out”) the framing scenario and its implications. Alternative types of 

scenario-based exercises may include or incorporate computer modeling and physical enactments 

or “drills.” The planning team for the TWG Non-Native Fishes Tabletop Exercise developed its

framing scenario based on the most recent two-year forecasts for reservoir levels in Lake Powell 

and the history of detections of smallmouth bass and green sunfish below the dam as reported by 

the Arizona Game and Fish Department [AZGFD], FWS, GCMRC, and NPS. 

A tabletop exercise consists of a sequence of discussions designed and guided to allow the

participants thoroughly to examine and question planned preparations, preventive measures, 

warning systems, decision-making procedures, and management responses, and develop 

recommendations for addressing potential weaknesses, conflicts, and other concerns. Such 

exercises are intended to help the participants: (1) clarify roles and responsibilities, (2) explore 

additional information and management preparedness levels and needs, and (3) document 

program plans, procedures, and capabilities as well as logistical hurdles and overall program 

deficiencies. Such exercises therefore are a useful tool for the TWG: As noted by Reclamation in 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 4

its statement of the roles of the TWG within the GCDAMP, “[t]he Technical Work Group is a 

subcommittee of the Adaptive Management Work Group... [with responsibilities] to develop 

criteria and standards for monitoring and research programs; provide periodic review and 

updates; develop resource management questions for the design of monitoring and research by 

the Grand Canyon Monitoring and Research Center [GCMRC]; and provide information, as 

necessary, for preparing annual resource reports and other reports, as required for the AMWG.” 

The inclusion of the nine technical presentations in the TWG meeting agenda ahead of the 

exercise affected the exercise in four important ways. First, the presentations covered all aspects 

of the situation potentially facing the Grand Canyon ecosystem from escapements of non-native 

predatory fishes through Glen Canyon Dam. This coverage included the ways in which 

conditions in Lake Powell can affect the potential for escapements (Presentations 1, 2, 3, 5, and 

6), the possibilities for preventing escapements through engineering modifications to the dam 

and its forebay (Presentation 7), lessons learned from efforts to monitor and control smallmouth 

bass in the Upper Colorado River Basin (Presentation 4), challenges for monitoring and 

managing non-native predatory fishes in Glen, Marble, and Grand Canyons (Presentation 8), and 

efforts by the Smallmouth Bass Task Force and its member agencies (AZGFD, FWS, GCMRC, 

NPS, and Western Area Power Authority [WAPA]) to formulate plans for detecting and 

responding rapidly to escapements (Presentations 8 and 9). Second, each presentation was 

followed by time for questions from the TWG. This time for questions and answers provided an 

advance opportunity for the TWG to begin working on the topic of the exercise, including 

identifying subjects for which they needed more information to help them understand the 

situation. Third, as noted above, the participation of the presenters and others from their 

institutions in the exercise allowed the TWG to continue asking questions of these experts 

throughout the exercise. Fourth, the inclusion of the presentations ahead of the exercise allowed 

the exercise to follow a simpler design than is typical of scenario planning exercises. Rather than 

strictly “playing out” the scenario provided for the exercise (see Attachment I), the exercise 

could focus directly on the questions and concerns of the TWG about the situation in the water 

and the planning efforts already underway. 

The exercise took place over two days, as shown in the exercise agenda (Attachment I): 

• Session 1 on Day 1 mostly consisted of breakout group sessions. Clarence Fullard, 

Reclamation, with input from David Braun, Sound Science LLC, assigned every TWG 

member and alternate, along with several GCMRC scientists, to one of the three breakout 

groups. The assignments ensured that each breakout group included representatives from 

every category of stakeholder with membership in the TWG (Federal Agencies, Indian 

Tribes, Basin States, Environmental Groups, Recreation Interests, Federal Power 

Purchase Contractors, and Other Stakeholders). Additional individuals were added to 

these breakout groups at the time of the exercise. Attachment II lists the original 

assignments of individuals to the three breakout groups, including the group facilitators. 

Some individuals participated in breakout groups other their original assignments. Sound 

Science LLC prepared guidance for the facilitation; Attachment III provides a copy of 

that guidance. 

• Session 2 on Day 2 consisted entirely of summaries of the breakout group deliberations 

from Day 1 followed by discussions by the whole group, all facilitated by David Braun, 

Sound Science LLC, assisted by Christine Wisnewski, Sound Science LLC. 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 5

• Session 3 on Day 2 consisted entirely of discussions by the whole group, facilitated by 

David Braun, Sound Science LLC, assisted by Christine Wisnewski, Sound Science LLC. 

Sound Science LLC also developed an online survey for the TWG members and alternates to 

complete after the end of the exercise. The survey had two purposes: (1) to poll the TWG on 

their final thoughts about the topic of the exercise; and (2) to poll the TWG on their final 

thoughts about the structure and conduct of the exercise itself. Attachment IV presents the survey 

form itself.

Sound Science LLC compiled the written notes from the breakout and full-group sessions, 

digitally generated transcripts of the Webex session recordings, the digital record of Webex 

“Chat” comments that accumulated over the course of the exercise, and the results of the online 

survey. The remainder of this report synthesizes this information and summarizes the results of 

the exercise under the three topics identified in the exercise statement of purpose. That is, the 

summary identifies areas in which the TWG expressed concerns relating to: (a) agency 

responsibilities for monitoring and responding to such events, (b) possible ways in which these 

agencies may respond to such events and ways in which these actions may affect the river and its 

canyons and biota, and (c) possible roles for the AMWG and its TWG in the decision-making 

process for such actions. The summary of TWG concerns about agency responsibilities 

distinguishes them under the headings of preparations, preventive measures, warning systems, 

and decision-making. 

Exercise Results: Agency Responsibilities 

Preparations

Discussions during the exercise and in the Webex Chat window did not identify any significant 

concerns about which agencies should be involved in preparations for detecting and potentially 

responding to threats of escapements or actual escapements. The presentations and discussions 

made it clear that these agencies—AZGFD, FWS, GCMRC, NPS, and Reclamation—are already 

working together on the Smallmouth Bass Task Force. However, TWG members did emphasize 

the importance of consultations with the Tribes and with the Western Area Power Authority (a 

member of the Task Force) and Federal Power Purchase Contractors as parts of preparations for 

responding to actual escapements. TWG members also asked questions about the possible role(s) 

of the TWG and AMWG in reviewing agency preparations, as discussed below (see Exercise 

Results: Possible AMWG and TWG Roles).

Preventive Measures

Discussions during the exercise and in the Webex Chat window did not identify any significant 

concerns about the central role of Reclamation in efforts to prevent escapements through the 

dam. Meeting participants appreciated the information presented by Reclamation on its current 

study of possible options for preventing escapements, and on the need for approvals up to the 

Secretary of Interior (as well as likely through Congress) for any eventual decisions and actions 

on installing mechanical preventive measures either in the water or into the dam itself. However, 

TWG members did ask questions about the possible role(s) of the TWG and AMWG in 

reviewing the engineering options that Reclamation identifies as potentially physically and 

financially feasible, as discussed below (see Exercise Results: Possible AMWG and TWG 

Roles). Concerns about the ways in which dam operations might be managed to prevent non-
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 6

native fishes such as smallmouth bass from becoming established below the dam are addressed 

below (see Exercise Results: Possible Agency Responses).

Warning Systems

Discussions during the exercise and in the Webex Chat window identified some concerns about 

the capability of existing monitoring programs in Lake Powell to detect and report promptly on 

threats of escapements. TWG members understand the importance of data on lake levels, water 

temperature and water quality profiles, and the horizontal and vertical distributions of non-native 

fishes in lower Lake Powell for assessing the likelihood of escapements. However, they await 

information on what species and life stages may remain viable after passing through the dam 

(part of the Reclamation study noted above). TWG members also asked questions about how 

quickly information on lake hydrologic, thermal, chemical, and biotic conditions can be 

translated into near-real-time information on the potential for escapements. The agencies 

responsible for detecting and potentially responding to escapements, after they occur, all require 

such information to guide their preparations and actions. Additionally, other stakeholders may 

require or prefer having such information to enable them to engage in decision making about 

responses to escapements.

Discussions during the exercise and in the Webex Chat window also highlighted concerns about 

the capability of existing monitoring programs along the river below the dam to detect and report 

promptly on actual escapements. The monitoring of fishes below the dam takes place through 

several programs that are either explicitly designed to detect non-native fishes or capable of 

detecting them because of the methods they employ. These programs include the long-term, 

standardized monitoring efforts of AZGFD throughout the Colorado River from Lees Ferry 

(River Mile [RM] 0) to Pearce Ferry (RM 281). As stated in the recent GCMRC “Fiscal Year 

2021 Annual Project Report to the Glen Canyon Dam Adaptive Management Program,” AZGFD

conducts this monitoring “... for the combined purposes of tracking the status of native fish as 

well as identifying new invasive aquatic species. This project also provides detection capability 

for new warm-water invasive fish which may be entering the Colorado River Ecosystem (CRe) 

from Lake Powell by passing through Glen Canyon Dam, descending tributaries such as the 

Little Colorado River (LCR), or swimming upstream from Lake Mead.” Other monitoring 

programs capable of detecting non-native fishes, mentioned during the exercise or in the 

preceding presentations, include the Trout Reproductive and Growth Dynamics (TRGD) study 

and Brown Trout Early Life Stage Survey (BTELSS) (AZGFD, FWS, GCMRC), several 

activities under the general umbrella of humpback chub population studies (FWS, GCMRC), and 

several monitoring efforts by Grand Canyon National Park. 

Discussions during the exercise and in the Webex Chat window specifically identified concerns 

that: (1) the existing monitoring programs below the dam are not designed for or capable of 

detecting “all” or even a large fraction of any non-native fishes that may be present below the 

dam at any one time or over the course of any single year, with diminishing capabilities 

downstream of Lees Ferry and even lower capabilities in the tributaries; (2) these existing 

programs are not designed for or capable of reliably detecting all life stages of these fishes with 

equal probability; (3) these existing programs are not designed for or capable of reliably 

detecting spawning or nesting activity throughout the potential reproductive season; (4) the 

translation of detection counts of fishes (numbers captured by reach by different methods) into

estimates of abundance produces estimates with statistical margins of error that may be quite 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 7

wide; (5) monitoring specifically aimed at detecting non-native fishes in low-velocity habitats 

(which smallmouth bass use for foraging cover and reproduction) currently takes place only 

twice a year, and the frequency and scope of these focused monitoring efforts are tightly limited 

by budget; (6) it is not clear what levels of detection (numbers captured by reach) or statistical 

estimates of abundance or spawning/nesting activity would be high enough to warrant a “threat 

alert” or trigger a response; and (7) it is not clear how, or how quickly, detection data from Glen, 

Marble, or Grand Canyon or their tributaries can be assimilated among the agencies involved in 

the monitoring, to identify high-risk situations. The agencies responsible for detecting and 

potentially responding to escapements all require such information to guide their preparations 

and actions. Additionally, other stakeholders may require or prefer having such information to 

enable them to engage in decision making about responses to escapements. 

For example, for the sixth of the points listed in the preceding paragraph, Dr. Yackulic, GCMRC, 

explained during his presentation before the exercise that adult fish density affects the likelihood 

of reproduction: below some threshold of density for a given species, adults may not encounter 

each other often enough to reproduce at a rate greater than the rate of population loss to mortality 

(e.g., from predation). That is, the population growth rate, lambda (λ), depends on the density of 

adults. If the density is too low, λ will be less than 1.0 and population numbers will decline, but 

if the density is greater than some threshold level, λ will be greater than 1.0 and population 

numbers will increase. The presentations that preceded the exercise, including the presentation 

about Upper Colorado River efforts by Dr. Bestgen, Colorado State University, showed that 

below-dam surveys for an ecologically disruptive non-native species, such as smallmouth bass, 

therefore need to be capable of detecting either, or both, of two things: (1) an abundance of 

reproductive-age adults that has a very low probability of being close to or greater than the 

threshold of density for λ=1.0 for that species, or (2) evidence of reproductive activity per se. 

Smallmouth bass seek out specific types of low-velocity habitat, both for foraging cover and for 

nesting. Monitoring efforts below Glen Canyon Dam survey only a fraction of these types of 

habitats every year in any river reach, and sampling specifically targeted at non-native habitat 

occurs only twice a year, as noted above. Dr. Yackulic noted that, based on modeling 

experiments and detection probabilities, the population threshold for a value of λ>1.0 in the Lees

Ferry reach for smallmouth bass might correspond to a detection of only 6-7 adult bass in that 

reach during the Spring system-wide monitoring survey. TWG members noted that the framing 

scenario for this exercise, which hypothesized the detection of 12 adult smallmouth bass in the 

same reach, constitutes a “breakthrough” scenario: if surveys find 12 adult bass in that reach 

during April monitoring, there likely will be several hundred bass in that reach. That is, the bass 

would already be well established in that reach. Dr. Yackulic indicated that, once smallmouth 

bass are established in the Lees Ferry reach or, even worse, downstream from Lees Ferry, it will 

be extremely difficult, time-consuming (over years), and costly to ever bring their numbers under 

control again. 

Discussions during the exercise and in the Webex Chat window also identified a concern, 

reinforced by comments by experts involved in fish monitoring efforts below the dam, that 

temperature monitoring along the river does not provide sufficient information about water 

temperatures in low-velocity habitat along channel margins or in backwaters. These are the 

settings in which some of the non-native species of interest reproduce (e.g., smallmouth bass, 

green sunfish), particularly smallmouth bass when water temperatures in these settings exceed 16 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 8

°C. Water temperatures in these settings frequently can exceed the temperature of the bettermixed waters in the main river channel. 

TWG members noted that recreational anglers and the citizen science efforts of the river boating 

community might be engaged to report observations of non-native fishes. However, no 

information was presented, or suggestions offered, on how such observations might be 

encouraged or assimilated, or which agencies might need to be involved in making this happen. 

Decision-Making Procedures

Discussions during the exercise and in the Webex Chat window identified some concerns about 

which agencies would be involved in decision making about (1) possible preventive measures to 

implement above or in the dam forebay, (2) improving detection capabilities and alert systems 

for threats of escapements or actual escapements, (3) engaging with recreational visitors and 

citizen science programs to incorporate their observations into detection efforts, or (4) responses 

to actual escapements. As noted above, TWG members emphasized the importance of 

consultations with the Tribes and with the Western Area Power Authority and Federal Power 

Purchase Contractors as parts of preparations for responding to actual escapements. TWG 

members also asked questions about the possible role(s) of the TWG and AMWG in decision 

making, as discussed below (see Exercise Results: Possible AMWG and TWG Roles).

Exercise Results: Possible Agency Responses Discussions during the exercise and in the Webex Chat window repeatedly identified prevention

as the top priority for addressing the threat of non-native fish escapements through the dam. This 

prioritization arose in response to expert statements both during the pre-exercise presentations 

and during the exercise itself. These statements emphasized that, under plausible future 

conditions in the lake and the river, smallmouth bass specifically may be able to pass through the 

dam, begin reproducing before the situation is fully diagnosed, and become established in the 

river below the dam faster than monitoring and removals can control the threat. The exercise 

participants also heard from the experts that it was not possible to predict how soon such a 

“breakthrough event” might occur based on forecasts of lake water levels. Some of this 

uncertainty results from a lack of information at the time of the exercise, about how the Upper 

Division States, Reclamation, and the Upper Colorado River Commission will implement the 

2019 Drought Response Operations Agreement (DROA), including a lack of information about 

whether their Drought Response Operations Plan will include additional deliveries of water to 

maintain higher water levels in Lake Powell. Raising water levels in Lake Powell would reduce 

the likelihood of entrainment of non-native fishes through the turbine intake. 

The exercise participants also learned that, even optimistically, it could take several years for 

Reclamation to complete its process for (1) identifying effective, physically suitable, financially 

feasible options for preventing escapements, (2) obtaining approvals up to the Secretary of 

Interior, (3) obtaining funding through Congress, and (4) installing and beginning operating any 

preventive measures. This information prompted further discussions about what the next lines of 

defense should be. 

Discussions during the exercise and in the Webex Chat window also followed up on ideas 

presented by the Smallmouth Bass Task Force, concerning the possible use of dam operations to 

disrupt spawning and nesting behavior of non-native fishes along the first miles of the river 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 9

below the dam. The Task Force presentation covered two possibilities: (1) discharging water at 

high rates (up to 45,000 cubic feet/second [cfs]) to reduce the availability of low-velocity 

spawning habitat specifically for smallmouth bass along the channel margins; and (2) 

discharging sufficient volumes of cold hypolimnetic water to maintain water temperatures below 

the critical smallmouth bass spawning threshold of 16 °C. Both possibilities would require 

releases through the dam’s bypass tubes, removing the released water from the volume available 

for power generation. The Task Force presentation covered several increments of discharge rate 

for the high-flow method, and several variations on the timing of releases for the cold-water 

method. The presentation did not address (a) how the timing of high-flow pulses might affect 

outcomes or (b) how temperatures within the river channel might affect water temperatures in 

low-velocity habitat along the channel margins during cold-water releases. TWG members 

emphasized the importance of consultations with the Western Area Power Authority and Federal 

Power Purchase Contractors as parts of any discussions about using releases through the bypass 

tubes to try to disrupt smallmouth bass spawning. TWG members also asked questions about the 

possible role(s) of the TWG and AMWG in decision making concerning releases through the 

bypass tubes, as discussed below (see Exercise Results: Possible AMWG and TWG Roles).

TWG members took note of comments in the Task Force presentation that any releases of water 

through the bypass tubes to disrupt smallmouth bass spawning would be experimental: The ideas 

are highly plausible based on what is known about smallmouth bass biology in the Colorado 

River Basin and what is known about the effects of dam operations on downstream flow 

velocities and temperatures. However, neither approach has ever been tested with the Glen 

Canyon Dam and neither is anticipated in the Glen Canyon Dam Long-Term Experimental and 

Management Plan [LTEMP] approved in 2016. Off-screen discussions between TWG member 

Larry Stevens and Dr. Bestgen during the evening interval between the two days of the exercise 

also resulted in the suggestion of a third possible experimental approach to disrupting 

smallmouth bass reproduction: Raising or sustaining the discharge rate through the dam at a 

moderate level during the spawning season to create spawning habitat at a particular elevation, 

and then episodically and abruptly dropping the discharge rate (and hence the water surface 

elevation) very low to expose the resulting nests. This pulsing would either desiccate or flush out 

the eggs and larvae, resulting in very high (or complete) mortality. TWG members noted that this 

approach would again require consultations with the Western Area Power Authority and Federal 

Power Purchase Contractors and noted that extreme low flows would also affect recreational use 

of the river.

Discussions during the exercise touched on a question of how quickly federal and state agencies 

might be able to obtain authorization to act, to try to prevent or reverse the establishment of nonnative fishes below the dam—other than through adjustments to dam operations. The 

presentations before the exercise, and comments during the exercise from Rob Billerbeck, 

National Park Service, made it clear that the Park Service, at least, is authorized to remove nonnative fishes as “incidental take” during routine monitoring activities. The Grand Canyon 

National Park Comprehensive Fish Management Plan (CFMP) and its supplementary Expanded 

Non-Native Species Plan identify additional response “tiers” for rapidly responding to detections 

of priority non-native fish species using “mechanical, physical, biological, and chemical” means. 

Each of these tiers requires a different combination of consultations and permits for compliance 

with federal and state laws. TWG members questioned whether the Endangered Species Act and 

the protections it provides for the listed humpback chub might already provide the authorizations 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 10

that the responsible agencies (FWS, AZGFD, NPS) would need, to respond promptly to 

incursions of smallmouth bass below the dam that could threaten humpback chub abundance. 

This last matter was not fully addressed by the time the exercise concluded. (TWG members 

were informed that all agencies involved in fish monitoring below the dam are covered by 

“incidental take” permits for removing non-native fishes encountered during that monitoring). 

More generally, discussions during the exercise led to questions about whether the planning 

efforts underway have fully explored all requirements for compliance with federal and state laws 

and regulations. Bob Billerbeck, National Park Service, explained that the Grand Canyon 

National Park CFMP and its supplementary Expanded Non-Native Species Plan provide 

comprehensive information on all aspects of compliance affecting the National Park Service, 

including for inter-governmental consultations that would be involved under each of its 

designated response tiers; and that current planning efforts take all that information into account. 

However, Mr. Billerbeck also noted that the National Park Service would not and cannot 

undertake all of the rapid response actions described in his presentation, both because the skills, 

expertise, and equipment needed for such activities are spread among several agencies (AZGFD, 

FWS, GCMRC, NPS) and because the Park Service does not have sufficient funds to cover all 

(or even most) of the expenses that would be involved. 

Discussions during the exercise and in the Webex Chat window identified concerns about the 

state of planning for responses to escapements below the dam described in presentations 

preceding the exercise. TWG members expressed concerns about a perceived focus of this 

planning on individual labor-intensive interventions rather than on systemic solutions. The 

presenters clarified that their presentations in fact emphasize the need for less labor-intensive, 

less costly, systemic responses. Presenters offered several variations on the idea that “... 

spending $1 on prevention now could save $100 on remediation later.” Dr. Yackulic’s 

presentation also indicated that, once a species such as smallmouth bass becomes established 

below Lees Ferry, especially if it becomes established in Grand Canyon and its tributaries, 

reversing this situation may be physically and financially impossible. Discussions and Webex 

Chat comments noted that removal by capture or poisoning will work well only in isolated pools 

such as backwaters and sloughs, and in tributaries. 

Discussions during the exercise and in the Webex Chat window identified concerns about the 

specific methods under consideration for killing and/or mechanically removing non-native fish 

species such as smallmouth bass. These methods include killing with piscicides and capturing 

through various combinations of electrofishing and netting and/or seining. TWG members 

expressed concerns about: (1) the potential costs of such labor-intensive methods, including the 

costs of monitoring both to guide the removal efforts and to assess their effectiveness; (2) the 

difficulty of marshaling the logistical resources for such efforts fast enough, among multiple 

agencies; (3) the difficulty of obtaining permits for such efforts; (4) the complexity of obtaining 

prior consent from the sovereign tribes, who would need to be consulted through formal 

channels; and (5) the ethics of killing and removing some fish species in order to conserve 

others, including the ethics of going against the clearly expressed traditional values of some of 

the sovereign tribes that are parties to the GCDAMP. 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 11

Exercise Results: Possible AMWG and TWG Roles As noted above, TWG members throughout the exercise asked about the possible role(s) of the 

TWG and AMWG in decision making concerning actions being contemplated to prevent 

escapements, use specialized flow releases to disrupt smallmouth bass reproduction below the 

dam, or intentionally remove non-native fishes below the dam. These questions led to 

explanations from representatives from Reclamation and the National Park Service about the 

strictly advisory role of Federal Advisory Committees. Both the AMWG and TWG are Federal 

Advisory Committees, governed by the rules established in the Federal Advisory Committee Act 

of 1972 (FACA). Reclamation’s Director for the GCDAMP, Lee Traynham, further clarified that 

meetings of the AMWG and TWG can only take place at regular intervals, and only after a 

notice for each meeting is approved and posted in the Federal Register a required number of days 

beforehand. These rules limit the ability of these committees to respond quickly to issues that 

may arise. TWG members responded to this information with suggestions for making sure that 

“hot” topics were quickly brought to the attention of the TWG, since it is responsible for looking 

into technical matters for the AMWG. One member offered the idea that a TWG Ad Hoc Group 

such as the Steering Committee Ad Hoc Group (SCAHG) could be charged with keeping track 

of hot topics to bring to the attention of the full TWG or the AMWG.

The exercise facilitator suggested that TWG members who want to learn more about the laws 

and precedents governing the GCDAMP could refer to the documents listed on Reclamation’s 

home web page for the GCDAMP under the heading “Law of the River” and to the LTEMP 

Environmental Impact Study (EIS) and Record of Decision (ROD). If the TWG does not already 

have a briefing book or primer for new members, it also might consider developing one. This 

primer could discuss federal advisory committee rules and responsibilities, the TWG charter, the 

Law of the River and other legislation and legal decisions affecting Glen Canyon Dam 

operations and the decisions of the GCDAMP. One respondent to the online survey (see below) 

also asked if it would be possible for the TWG to hear presentations on the roles of the federal 

and state agencies responsible for managing the lake and river water and caring for the biological 

and cultural resources of the Grand Canyon ecosystem. 

Post-Exercise Survey Results Twelve TWG representatives submitted responses to the online survey (see Attachment IV). 

Respondents were asked to answer “Yes,” “No,” or “Uncertain” about eighteen questions, and 

submit narrative answers to clarify their answers as they saw fit. The respondents represent one 

federal agency, one tribe, five basin states, two environmental groups, one recreational interest, a 

group of five federal power purchase contractor representatives from CREDA and Utah 

Associated Municipal Power Systems [UAMPS], and AZGFD. 

The survey responses to questions about agency plans for monitoring and mitigation (Survey 

Part I; Table 1) were unanimous in (a) their level of concern about the possibility that non-native 

fishes or altered water quality conditions in lower Lake Powell could affect the Grand Canyon 

ecosystem, and in (b) their prioritizing prevention over detection and reaction to such events. The 

respondents also were nearly unanimous in answering either “No” or “Uncertain” to questions 

about whether the agencies responsible for managing conditions in lower Lake Powell have 

adequate plans for preventing the passage of problematic water temperatures, water chemistries, 

and/or non-native fishes through the dam and are moving quickly to implement these plans; and 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 12

whether the agencies responsible for taking action below the dam have adequate resources for 

mitigation responses, including for monitoring outcomes for adaptive management. 

Table 1.—Survey results Part 1: Plans for Monitoring and Mitigation.

Part 1 – Plans for Monitoring and Mitigation Yes No Uncertain

1. My nation, community, or agency is concerned about the possibility that non-native fishes or altered 

water quality conditions in lower Lake Powell could affect the Grand Canyon ecosystem.

12 0 0

2. My nation, community, or agency would prefer that greater priority be given to preventing the 

passage of problematic water temperatures, water chemistries, and/or non-native fishes through the 

dam, versus detecting and reacting to such events after the fact.

12 0 0

3. The agencies responsible for managing conditions in lower Lake Powell have adequate plans for 

preventing the passage of problematic water temperatures, water chemistries, and/or non-native fishes 

through the dam and are moving quickly to implement these plans.

0 9 3

4. Unless smallmouth bass can be prevented almost completely from passing through Glen Canyon 

Dam, detecting and removing and/or preventing the reproduction of this species below the dam—in 

Glen, Marble, or Grand Canyon and their tributaries—will be too costly and/or physically impossible to 

accomplish.

6 0 6

5. The agencies responsible for monitoring water temperatures, water chemistries, and/or non-native 

fishes above and below Glen Canyon Dam have adequate resources for conducting this monitoring.

5 2 5

6. The timing and spatial design for monitoring water temperatures, water chemistries, and/or nonnative fishes above and below Glen Canyon Dam is appropriate to the need to respond promptly and 

accurately to potentially problematic conditions.

3 4 5

7. The agencies responsible for monitoring water temperatures, water chemistries, and/or non-native 

fishes above and below Glen Canyon Dam have adequate plans for alerting the AMWG when potentially 

problematic conditions are detected.

5 1 6

8. The agencies responsible for mitigating potentially problematic water temperatures, water 

chemistries, and/or non-native fishes below the dam have adequate plans for deciding how and when 

to respond, including consulting with the AMWG.

4 6 2

9. The agencies responsible for mitigating potentially problematic water temperatures, water 

chemistries, and/or non-native fishes below the dam have adequate resources for mitigation responses, 

including for monitoring outcomes for adaptive management.

1 8 3

10. There appear to be important gaps in knowledge gaps that could affect decision making concerning 

the potentially problematic water temperatures, water chemistries, and/or non-native fishes below the 

dam.

4 3 5

11. The mitigation responses under consideration respect the values of my nation, community, or 

agency with respect to the river, canyons, and its biota.

7 3 2

12. The plans for mitigation responses take into account the possibility of unwanted effects that may 

require additional attention, including consulting with the AMWG.

5 0 6

13. The plans for mitigation responses take into account the possibility of failures. 4 1 7

14. The agency plans for mitigating potentially problematic water temperatures, water chemistries, 

and/or non-native fishes below the dam adequately to take into account the need to address possible 

effects of the agency actions on other aspects of dam operations including water storage and 

hydropower management.

4 2 6

Table 2.—Survey results Part 2: Tabletop Exercise Review.

Part 2 – Tabletop Exercise Review Yes No Uncertain

1. The exercise was a useful way to help me understand the potential for altered water temperatures, 

water chemistries, and/or non-native fishes introductions below the dam.

11 0 1

2. The exercise was a useful way to help me understand agency plans for monitoring and responding to 

the potential for altered water temperatures, water chemistries, and/or non-native fishes introductions 

below the dam.

8 1 3

3. The exercise gave me ample, respectful opportunities to express my views and listen to others’. 11 0 1

4. I would be interested in using this (or a similar) “tabletop exercise” approach to look into other topics 

of interest to the TWG.

12 0 0
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 13

Answers to the other twelve survey questions in Part I were more mixed, indicating a high level 

of disagreement or uncertainty among the respondents. For example, for Question 10 (“There 

appear to be important gaps in knowledge gaps that could affect decision making concerning the 

potentially problematic water temperatures, water chemistries, and/or non-native fishes below 

the dam”), the answers were almost evenly distributed among “Yes” (4), “No” (3), and 

“Uncertain” (5).

The survey responses to questions about the tabletop exercise itself (Survey Part II; Table 2) 

were unanimous or nearly unanimous in finding the exercise useful, agreeing that the exercise 

gave them ample, respectful opportunities to speak and listen, and expressing interest in using 

this (or a similar) “tabletop exercise” approach to explore other topics of interest to the TWG. 

The respondents had the greatest range of responses to the second question in this part of the 

survey (“The exercise was a useful way to help me understand agency plans for monitoring and 

responding to the potential for altered water temperatures, water chemistries, and/or non-native 

fishes introductions below the dam”), with eight saying “Yes,” one saying “No,” and three 

saying they were “Uncertain.”

Finally, the narrative comments of survey respondents provided explanations and clarifications 

for several responses. One TWG representative, whose Yes/No answers indicated doubts about 

current agency preparations and capabilities for responding to escapements, expressed concern 

that the agencies are proceeding without adequate input from the larger community of 

stakeholders. This response included an expression of grave concern that these agencies were 

bypassing the GCDAMP as a long-standing and important forum for fully vetting analyses, 

plans, and their underlying assumptions with the stakeholders. Another narrative respondent 

expressed concern about the potential magnitude of uncertainties in the present understanding of 

the lake and river ecosystems, how they will function at even lower lake levels, and possible 

ripple effects of new types of management actions. 

Summary of TWG Member Concerns and Responses to Exercise Discussions during the exercise and in the Webex Chat window, and the responses to the online 

survey, highlighted several concerns among TWG members, bearing on both the specific topic of 

the exercise and on TWG activities in general, as follows: 

• The exercise participants in general, including the survey respondents, are concerned 

about the possibility that non-native fish or altered water quality conditions in lower Lake 

Powell could affect the Grand Canyon ecosystem. The participants therefore prioritize 

prevention over detection and reaction to such events. Several exercise participants noted 

that escapements of non-native predatory fish into the river below Glen Canyon Dam 

could erase the hard-won gains of recent decades in conserving the native fish species in 

the Grand Canyon ecosystem, and that failing to prevent or (as a less-desirable fallback) 

to contain such escapements would constitute an unacceptable systemic failure. 

• The TWG participants in the exercise expressed concern that, except for the planning to 

prevent escapements through Glen Canyon Dam, the planning taking place seems to 

focus on preparations for reacting to escapements once they happen. As noted above, 

TWG members and participating experts expressed a consensus that prevention should be 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 14

the top priority. However, several TWG members also spoke about a need for the 

GCDAMP to develop a longer-term, holistic approach to managing the river and its 

ecosystem. Such an approach would need to consider the likely effects of climate change, 

continuing introductions of non-native species, and other factors that shape the Colorado 

River ecosystem. A “big picture” approach would provide a framework for proactively 

addressing individual concerns such as the threat of smallmouth bass escapements. The 

representative for Zuni Pueblo offered a caution that, in the historical experiences of the 

Pueblo, governmental actions taken to manage ecosystems across their landscape—

including human interactions with these ecosystems—can have considerable harmful 

effects if they do not rest on a deep understanding of those ecosystems. 

• At least judging from the survey respondents, the exercise participants did not leave the 

exercise convinced the agencies responsible for managing conditions in lower Lake 

Powell have adequate plans for preventing the passage of problematic water 

temperatures, water chemistries, and/or non-native fishes through the dam and are 

moving quickly to implement these plans. 

• The TWG participants in the exercise expressed concern that aquatic monitoring 

capabilities below the dam are not sufficient to detect and report on actual escapements

before the new arrivals can begin reproducing and spread downstream into Marble 

Canyon, the Grand Canyon, and their tributaries. This concern arises from understanding 

that current monitoring efforts: (a) produce probabilistic estimates of fish abundances, 

age distributions, and spatial distributions with ranges of statistical error; (b) do not target 

every habitat type or every life stage in every survey; and (c) have timing gaps between 

surveys during which escapements could occur. 

• The TWG participants in the exercise expressed concerns about what detection levels 

(thresholds) for non-native predatory fish either above or below the dam will or should be 

used either to trigger alerts (warnings) for agencies to be prepared for possible 

escapements or to trigger agency responses to escapements. The Grand Canyon National 

Park CFMP and its supplementary Expanded Non-Native Species Plan identify some 

thresholds for triggering rapid responses to detections of priority non-native fish species 

below the dam, but do not identify warning levels to guide preparations and do not 

address thresholds of potential concern for fish above the dam. 

• The participants in the exercise heard—and expressed concern about—statements from 

Reclamation, the National Park Service, and the Arizona Game and Fish Department that 

little in the way of “additional” funding is available for emergency response to incursions 

of non-native fish below the dam, let alone for any large-scale response in the event of a 

large or widespread incursion. Federal and state legislation would be needed to obtain 

funding at the right scale, and an effort to have such funding included in the National 

Park Service budget request for FY23 was not successful. Participant concern about this 

matter is also reflected in the survey responses.

• Similarly, the participants in the exercise heard—and expressed concern about—

statements from Reclamation that presently there is no budget for installing any 

preventive measures in the forebay of the dam to prevent species such as smallmouth 

bass from entering the penstock when the lake level is low enough, let alone for the longterm maintenance of such measures. Funds for such a substantial engineering effort 

would need to be requested and approved through Reclamation, the Department of 

Interior, and Congress, a lengthy process—and Reclamation is only at the stage of 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 15

compiling information about possible options to consider. Consequently, it will be years 

before any such measures could be approved, designed, installed, and activated. 

• The TWG participants in the exercise expressed concerns that the decision-making 

process—for planning and obtaining approvals for emergency responses to incursions of 

non-native fish below the dam—could take weeks or months absent fully approved plans 

and logistical readiness among the responsible agencies. The exercise participants heard 

that getting permits for some removal efforts (beyond what is already permitted) could be 

faster than getting approvals for systemic solutions. However, the participants expressed 

concern that this caveat should not be a reason for the responsible agencies to prioritize 

those more readily-approved actions over systemic solutions. Rather, the exercise 

participants voiced concern that the present task force needs to get plans in place and 

fully approved—including by the Secretary of Interior as needed—and ensure their 

logistical readiness as soon as possible. This sense of urgency resulted from their 

understanding that an incursion could occur even in the next year or so, given predicted 

lake levels in the forebay over the next two years. At the same time, the TWG 

participants in the exercise expressed concerns that, in working to get plans in place, the 

federal agencies involved in the planning should not treat the required consultations with 

the Tribes merely as “box-checking” exercises, but rather as important opportunities to 

try to identify, understand, and address Tribal concerns. 

• TWG members questioned whether the Endangered Species Act and the protections it 

provides for the listed humpback chub might already provide the authorizations that the 

responsible agencies (FWS, AZGFD, NPS) would need, to respond promptly to 

incursions of smallmouth bass below the dam that could threaten humpback chub 

abundance. 

• In discussing the urgency of the situation, further, TWG participants in the exercise heard 

from at least some of the fishery experts that it is not possible to predict how soon a 

smallmouth bass incursion might occur. Dr. Yackulic stated that, based on lake level 

forecasts, it might not occur for another 3-4 years, allowing the task force, TWG, and 

others to look at both short- and long-term solutions without having to react to any crises. 

However, Dr. Yackulic also noted that events can get ahead of such forecasts.

• The TWG participants in the exercise expressed concerns that removal of non-native 

fishes by capture or poisoning will work well only in isolated pools such as backwaters 

and sloughs, and in tributaries. 

• TWG members expressed interest in receiving presentations by the Upper Colorado 

River Endangered Fish Recovery Program and the Lower Colorado River Multi-Species 

Conservation Program, to inform the TWG about the activities and lessons being learned 

by these sister programs. One respondent to the online survey also expressed interest in 

additional presentations by Grand Canyon National Park on other management actions it 

has taken along the river in the past. 

• Finally, the exercise participants who responded to the online survey mostly found the 

exercise useful; mostly felt that it gave them ample, respectful opportunities to speak and 

listen; and unanimously expressed interest in using this (or a similar) “tabletop exercise” 

approach to examine other topics of interest to the TWG.
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 16

Attachment I. Tabletop Exercise Agenda 

 

Glen Canyon Dam Adaptive Management Program Technical Work Group 

 

Table 3.—Tabletop exercise agenda. 

Time Topic / Activity

Day 1, 3:15 - 5:00 EXERCISE, PART 1 OF 3

• Orientation, Agenda Review, and Goals: Facilitated, 15 minutes

o Explanation of exercise and session purposes, structure, intended 

outcomes, rules and sideboards

o Note: Exercise is not intended to commit anyone to anything in the 

event of an actual biotic or water quality threat passing through the 

dam. Participation is limited to TWG members and invited experts.

• Framing Scenario: 5 minutes

o It’s April 12, 2023. AZGFD has captured 12 reproductive-age adult 

smallmouth bass in Glen Canyon and 25 adult and juvenile green 

sunfish in the lower slough at RM 12 and observed additional green 

sunfish in both the upper and lower sloughs. Lake elevation at the 

dam is 3,510’ where it has stood for five weeks; and mid-channel 

water temperature at Lees Ferry is 10 °C.

• Brainstorming Discussion: Virtual breakout rooms, pre-assigned, 30 minutes

o Consider and discuss the following questions:

 Is your nation, community, or agency concerned about the 

possibility that non-native fishes or altered water quality 

conditions in lower Lake Powell could affect the Grand Canyon 

ecosystem? Is this a priority concern? What solutions might you 

Statement of Exercise Purpose: A real possibility exists that future discharges of water from Lake 

Powell through Glen Canyon Dam could have temperatures, water chemistries (e.g., dissolved oxygen 

levels), and/or entrained non-native fishes that could affect the aquatic ecosystem below the dam. 

The purpose of the exercise is to help the Technical Work Group (TWG) identify areas of potential 

importance to the Adaptive Management Work Group (AMWG), concerning: (a) agency 

responsibilities for monitoring and responding to such events, (b) possible ways in which these 

agencies may respond to such events and ways in which these actions may affect the river and its 

canyons and biota, and (c) possible roles for the AMWG and its TWG in the decision-making process 

for such actions.
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 17

propose?

 Is your nation, community, or agency concerned about the ways 

in which federal or state agencies may respond to an introduction 

of non-native fishes or altered water quality conditions from Lake 

Powell into the Grand Canyon ecosystem? Is this a priority 

concern? What solutions might you propose?

 What kind(s) of response(s) would you like or not like to see 

among the agencies responsible for addressing such situations, 

with what kinds of outcomes?

 What other options would you recommend be considered for 

responding (or not responding) to introductions of non-native 

fishes or altered water quality conditions from Lake Powell into 

the Grand Canyon ecosystem?

o Identify topics you might want to know more about (e.g., technical 

information gaps, possible technical approaches and their possible 

outcomes, decision-making processes).

• Full Group Report-Out: Breakout group facilitator summaries, 15 minutes

o 5 minutes per group

o Lead facilitator summary; Q&A

• Topic-Specific Discussion: Same pre-assigned virtual breakout groups, 40 

minutes

o Breakout group assigned foci:

1. Potential remediation responses to unwanted biotic or water 

quality conditions in Glen and Marble Canyons (Clarence Fullard 

facilitates)

2. Decision-making arrangements and their information 

requirements (Michelle Garrison facilitates)

3. Detection/alert systems for unwanted biotic or water quality 

conditions in Lake Powell forebay and/or in Glen and Marble 

Canyons (David Braun facilitates)

o Building off the results of earlier brainstorming, consider the 

following four topics (and others you may want to address) for your 

breakout group focus:

 Highest priority concerns overall [e.g., what issues or concerns 

are your highest priority as a stakeholder, including things that 

are missing in current plans?]

 Information gaps [e.g., what do you need to know to have a 

better understanding of the situation and possible solutions?]

 Management and resources issues [e.g., what potential gaps do 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 18

you perceive in management arrangements and resources (funds, 

equipment, staffing, logistics) for addressing the situation?]

 Concerns about potential unacceptable actions or effects [e.g., 

what potential impacts to the canyons, ecosystem, and other 

conditions and values are of concern?]

• Concluding: Full group, 5 minutes

o Final comments for the day

Day 2, 10:00 -

11:00

EXERCISE, PART 2 OF 3

Full Group Report-Out: Full group, 15 minutes

○ Breakout room facilitators report out on the discussions from Day 

One

○ Q&A

• Full Group Discussion: Full group, 45minutes 

○ Use the WebEx “chat” function to identify topics or issues from the 

first session seem most important to you for identifying as potentially 

important to the TWG or AMWG.

 Take two minutes to enter down your comments – just post 

please, do not comment on each other’s posts in the chat field.

 Facilitator will lead discussion of a handful of comments.

○ Identify the priority concerns among TWG members that emerged in 

the Day-One breakout groups. We will start with the following nine 

topics and expand as needed. Use the WebEx chat input to suggest 

additional discussion topics:

1. Information gaps

2. Management and resources issues

3. Decision-making process

4. Openness of management and decision-making to TWG or 

AMWG advice

5. Speed with which decisions need to versus can be made

6. Defining actionable threshold conditions

7. Potential unacceptable effects of agency actions

8. Nimbleness of planned approaches including fallback position(s) 

if planned approaches do not work

9. Potential for/acceptability of failure

○ Final discussion for the session
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 19

 How confident are you that a solution to an emergency could find 

consensus support from the TWG?

 When dealing with potential emergencies, do you favor taking a 

“wait and see approach” or an “act immediately” approach?

Day 2, 11:00 -

11:15

BREAK

During the break, please think about roles and responsibilities:

• How can the TWG be a responsive asset and resource to the Glen Canyon 

Adaptive Management Program in potential emergency situations such as the 

one examined?

Day 2, 11:15 -

12:15

EXERCISE, PART 3 OF 3

• Full Group Discussion: Full group, 30 minutes

o How can the TWG be a responsive asset and resource to the Glen 

Canyon Dam Adaptive Management Program in an emergency 

resulting from introductions of non-native fishes or altered water 

quality conditions from Lake Powell into the Grand Canyon 

ecosystem?

o What barriers or inhibitors could prevent the TWG from responding 

effectively to such an emergency?

o Please take two minutes to post a single chat, stating your top 

takeaway from the exercise – just post please, do not comment on 

each other’s posts in the chat field.

• Full Group Discussion Wrap-Up: Full group, 15 minutes

o Facilitator summaries of key findings and concerns highlighted by the 

exercise and final discussion

• Concluding Summary: Full group, 15 minutes

• Final Instructions

○ You will be sent a link to an online survey tool, for you to provide 

further comments on the topic of the exercise and feedback on the 

exercise itself.

○ Please post your response to the survey by April 19 (COB)
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 20

Attachment II. Tabletop Exercise Breakout Group Assignments 

Breakout Group 1

Facilitator: Clarence Fullard, Reclamation

• Emily Omana Smith, National Park Service - Grand Canyon 

• Carrie Canon, Hualapai Tribe

• Daniel Bulletts, Southern Paiute Consortium 

• Kristen Johnson, Arizona Department of Water Resources

• Emily Halverson, Colorado Water Conservation Board 

• Laura Dye, State of Nevada

• Betsy Morgan, Utah Department of Water Resources

• Larry Stevens, Grand Canyon Wildlife Council 

• Ben Reeder, Grand Canyon River Guides 

• Bill Persons, Fly Fisher's International / Trout Unlimited

• Shane Capron, Western Area Power Authority 

• Dave Rogowski / Julie Carter, Arizona Game and Fish Department

• Ted Kennedy, GCMRC 

Breakout Group 2

Facilitator, Michelle Garrison, Colorado Water Conservation Board and TWG Vice Chair

• Chip Lewis, Bureau of Indian Affairs

• Brian Healy, National Park Service - Grand Canyon 

• Rob Billerbeck, National Park Service - Glen Canyon 

• Jakob Maase, Hopi Tribe

• Chris Harris / Jessica Neuwerth, Colorado River Board of California 

• Christine Noftsker, New Mexico Interstate Stream Commission

• Charlie Ferrantelli, Wyoming State Engineer's Office 

• Scott McGettigan, Utah Department of Water Resources

• David Brown, Grand Canyon River Guides 

• Gary Tallman / Jim Strogen, Fly Fisher's International / Trout Unlimited

• William E. Davis, Colorado River Energy Distributor's Association

• Craig Ellsworth, Western Area Power Authority 

• Lucas Bair / Charles Yackulic, GCMRC

Breakout Group 3

Facilitator, David Braun, Sound Science LLC 

• Garry Cantley, Bureau of Indian Affairs

• Kerri Pedersen, Reclamation

• Kirk Young, U.S. Fish and Wildlife Service 

• Erik Stanfield, Navajo Nation

• Kurt Dongoske, Pueblo of Zuni 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 21

• Shana Rapoport, Colorado River Board of California 

• Mel Fegler, Wyoming State Engineer's Office 

• Sinjin Eberle, American Rivers

• Kelly Burke, Grand Canyon Wildlife Council 

• Clifford Barrett, Utah Associated Municipal Power Systems 

• Leslie James / Ted Rampton, Colorado River Energy Distributor's Association 

• Ryan Mann, Arizona Game and Fish Department

• Mike Moran, GCMRC
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 22

Attachment III. Tabletop Exercise Breakout Group Facilitator Guidance 

Background

The function of the Glen Canyon Dam Adaptive Management Program (GCDAMP) Technical 

Work Group (TWG) is to provide technical assistance to the GCDAMP Adaptive Management 

Work Group (AMWG). Standing responsibilities of the TWG, as assigned by AMWG, are to 

consult with the Grand Canyon Monitoring and Research Center (GCMRC) in developing 

criteria and standards for monitoring and research programs; develop resource management 

questions for the design of monitoring and research administered by the GCMRC; and provide 

information, as necessary, for preparing annual resource reports and other reports, for the 

AMWG. ... The TWG [also] will identify opportunities to increase dialogue among members. 

Educating each other about our different perspectives is crucial.1

Exercise Purpose

A real possibility exists that future discharges of water from Lake Powell through Glen Canyon 

Dam could have temperatures, water chemistries (e.g., dissolved oxygen levels), and/or entrained 

non-native fishes that could affect the aquatic ecosystem below the dam. The purpose of the 

exercise is to help the TWG identify areas of potential importance to the AMWG, concerning: 

(a) possible agency responses to such introduced conditions below the dam and (b) possible roles 

for the AMWG and its TWG in the decision-making process for such responses. The exercise 

and preceding expert presentations will examine agency roles and responsibilities, and 

information and management preparedness needs. 

Facilitator Technical Responsibilities

The facilitators for the breakout groups (Michelle, Clarence, David) and the facilitator for the 

exercise overall (David) are responsible (a) for ensuring that each part of the exercise completes 

its goals; and (b) for ensuring that the exercise overall provides useful information for 

communicating to the AMWG. This information will concern the anticipated introductions from 

Lake Powell and agency responses to these introductions, including (a) plans for monitoring for 

unwanted biotic or water quality conditions in Lake Powell forebay and/or in Glen and Marble 

Canyons and alerting decision-makers of findings; (b) plans for remediation responses to 

unwanted biotic or water quality conditions in Glen and Marble Canyons; and (c) plans for how 

decisions will be made for responding to these unwanted conditions in Glen and Marble 

Canyons. The information to be communicated to the AMWG will address at least the following 

five questions: 

1. What issues or concerns are the highest priorities for individual stakeholders and for the 

TWG, including matters that may be missing in current agency plans for monitoring and 

response? 

2. What information gaps does the TWG see affecting understanding of the situation, and 

what solutions might it propose to close these gaps? 

3. What potential gaps does the TWG perceive in plans and assignments of responsibilities 

for monitoring, response actions, and decision making, including the openness of 

decision making to input from the AMWG and its members? 

1 Quoted from TWG Operating Guidelines.
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 23

4. What potential gaps does the TWG perceive in the resources (funds, equipment, staffing, 

logistics) likely available for monitoring and for response actions? 

5. What are TWG concerns about potential unacceptable actions or effects to the canyons, 

ecosystem, species, and other conditions and values of importance to AMWG members?

The exercise agenda identifies several more specific questions and topics to pursue, including to 

prompt discussion if needed. 

Facilitator Sociocultural Responsibilities

The TWG is a diverse assemblage of knowledgeable, experienced individuals representing 

stakeholders with diverse interests, values, and points of view—not only concerning the Glen, 

Marble, and Grand Canyons and the Colorado River as it flows though these canyons, but also 

concerning Glen Canyon Dam and its operations, and concerning the effects of visitors and 

federal and state agency actions on the river and its canyons. 

Facilitation of the exercise will allow all TWG members to express their views and concerns 

without judgement by the facilitators or by other participants and will not try to steer discussions 

toward “majority” versus “minority” views. The facilitators will encourage the participants to 

think creatively about the topics of the exercise and share these thoughts with the larger group. If 

participants disagree on some matter, the facilitators will make note of these differences but not 

take time from the overall discussion to have these differences debated. If participants raise 

topics or concerns that do not seem to be germane to the subject of the exercise, the facilitators 

will ask that they be held aside for separate discussion outside the exercise. Our intention is to 

foster open, thoughtful, mutually respectful dialogue. 

Reporting

Please take notes or have a colleague take notes during the breakout group discussions. And 

please provide the lead facilitator with a copy of your notes from each day, to assist with the 

preparation of the final report. 
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 24

Attachment IV. Tabletop Exercise Online Survey Form 

April 2022 TWG Tabletop Exercise: Information & Management Gaps

Please complete this survey to provide your final thoughts as a TWG representative, on the results of 

the tabletop exercise conducted as part of the April 2022 TWG virtual meeting. 

Please submit your responses by COB April 19, 2022.

The exercise concerned the possibility that future discharges of water from Lake Powell through Glen 

Canyon Dam could introduce problematic water temperatures, water chemistries, and/or non-native 

fishes into the aquatic ecosystem below the dam.

*Required

Email*

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Plans For Monitoring & Mitigation

Please rate the following statements (Yes/No/Uncertain)

1. My nation, community, or agency is concerned about the possibility that non-native fishes or 

altered water quality conditions in lower Lake Powell could affect the Grand Canyon Ecosystem.

o Yes

o No

o Uncertain

2. My nation, community, or agency would prefer that greater priority be given to preventing the 

passage of problematic water temperatures, water chemistries, and/or non-native fishes 

through the dam, versus detecting and reaction to such events after the fact.

o Yes

o No

o Uncertain

3. The agencies responsible for managing conditions in lower Lake Powell have adequate plans for 

preventing the passage of problematic water temperatures, water chemistries, and/or nonnative fishes through the dame and are moving quickly to implement these plans. 

o Yes

o No

o Uncertain
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 25

4. Unless smallmouth bass can be prevented almost completely from passing through Glen Canyon 

Dam, detecting and removing and/or preventing the reproduction of this species below the 

dam–in Glen, Marble, or Grand Canyon and their tributaries–will be too costly and/or physically 

impossible to accomplish.

o Yes

o No

o Uncertain

5. The agencies responsible for monitoring water temperatures, water chemistries, and/or nonnative fishes above and below Glen Canyon Dam have adequate resources for conducting this 

monitoring.

o Yes

o No

o Uncertain

6. The timing and spatial design for monitoring water temperatures, water chemistries, and/or 

non-native fishes above and below Glen Canyon Dam is appropriate to the need to respond 

promptly and accurately to potentially problematic conditions.

o Yes

o No

o Uncertain

7. The agencies responsible for monitoring water temperatures, water chemistries, and/or nonnative fishes above and below Glen Canyon Dam have adequate plans for alerting the AMWG 

when potentially problematic conditions are detected.

o Yes

o No

o Uncertain

8. The agencies responsible for mitigating potentially problematic water temperatures, water 

chemistries, and/or non-native fishes below the dam have adequate plans for deciding how and 

when to respond, including consulting with the AMWG.

o Yes

o No

o Uncertain

9. The agencies responsible for mitigating potentially problematic water temperatures, water 

chemistries, and/or non-native fishes below the dam have adequate resources for mitigation 

responses, including for monitoring outcomes for adaptive management.

o Yes

o No

o Uncertain
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 26

10. There appear to be important gaps in knowledge that could affect decision making concerning 

the potentially problematic water temperatures, water chemistries, and/or non-native fishes 

below the dam

o Yes

o No

o Uncertain

11. The mitigation responses under consideration respected the values of my nation, community, or 

agency with respect to the river, canyons, and its biota.

o Yes

o No

o Uncertain

12. The plans for mitigation responses take into account the possibility of unwanted effects that 

may require additional attention, including consulting with the AMWG.

o Yes

o No

o Uncertain

13. The plans for mitigation response take into account the possibility of failures.

o Yes

o No

o Uncertain

14. The agency plans for mitigating potentially problematic water temperatures, water chemistries, 

and/or non-native fishes below the dam adequately to take into account the need to address 

possible effects of the agency actions on other aspects of dam operations including water 

storage and hydropower management.

o Yes

o No

o Uncertain

Narrative Responses Concerning Monitoring & Mitigation

If you would like to explain or elaborate on your response to any of the fourteen statements above, 

please use the space provided here. Please number your responses to correspond to the ten [sic] 

numbered statements above.

Tabletop Exercise Review

Please rate the following statements (Yes/No/Uncertain):

1. The exercise was a useful way to help me understand the potential for altered water 

temperatures, water chemistries, and/or non-native fishes introductions below the dam

o Yes

o No
GCDAMP, TWG Non-Native Fishes Tabletop Exercise, April 12-13, 2022, Draft Final Report 27

o Uncertain

2. The exercise was a useful wat to help me understand agency plans for monitoring and 

responding to the potential for altered water temperatures, water chemistries, and/or nonnative fishes introductions below the dam

o Yes

o No

o Uncertain

3. The exercise game me ample, respectful opportunities to express my view and listen to others’.

o Yes

o No

o Uncertain

4. I would be interested in using this (or a similar) “tabletop exercise” to look into other topics of 

interest to the TWG.

o Yes

o No

o Uncertain

Narrative Responses Concerning Tabletop Exercise Review

If you would like to explain or elaborate on your responses to any of the four statements above, please 

use the space provided here. Please number your responses to correspond to the four numbered spaces 

above. 

End Survey