April 8, 2022 

To: Glen Canyon Leadership Team for Implementation of Experiments under the Long Term 

Experimental and Management Plan (LTEMP) 

From: LTEMP Planning/Implementation Team 

Re: Final Recommendation to Implement Experimental Macroinvertebrate Production Flow 

Releases (“Bug Flows”) at Glen Canyon Dam in Water Year 2022 

I. Recommendation Summary 

The LTEMP Planning/Implementation Team (PI Team) recommends that experimental 

Macroinvertebrate Production Flows (“Bug Flows”) be implemented at Glen Canyon Dam 

beginning May 1 through August 31, 2022. This recommendation does not reflect consensus: the 

Western Area Power Administration (WAPA) has substantial concerns with implementing a Bug 

Flows experiment in 2022 and does not support the recommendation; Arizona and New Mexico 

abstained; and the U.S. Fish and Wildlife Service and Arizona Game and Fish Department were 

not present for final deliberations. 

The PI Team has determined the Bug Flows experiment has the potential to improve food base 

productivity and aquatic insect diversity, with consequent benefits to native fish and ecosystem 

health also likely. The Science Advisors concluded that Bug Flows appeared to have met the 

experimental objectives described in the LTEMP (i.e., improve food base productivity and insect 

diversity) and that reducing uncertainties through additional experimentation would inform 

future design considerations. 

The PI Team also identified the potential for adverse effects to the hydropower resource. Using 

forecasted energy prices obtained in March 2022, the Western Area Power Administration 

estimates that the expense of a Bug Flows experiment in 2022 would be approximately $1.4M 

based on current data. The PI Team defers the determination of whether these effects are 

unacceptable to the Leadership Team and to the Department of the Interior. 

In recognition of uncertainty in WY 2022 hydrology, annual and monthly operations, and 

resource conditions, the PI Team would meet bi-weekly beginning the week of May 1st and 

continuing throughout implementation of the Bug Flows experiment to evaluate whether new 

conditions or unanticipated negative impacts have occurred or are likely to occur. Items that may 

warrant the PI Team to consider recommending termination of implementation include, but are 

not limited to: 

• Detection of juvenile smallmouth bass in Lees Ferry and/or observations that indicate the 

Bug Flows experiment could benefit smallmouth bass. 

• An increase to the estimated cost of the Bug Flows experiment to more than double the 

current estimated cost (i.e. an increase from $1.4M to $2.8M or more) that may result 

1 
 

 

 

from increases in forecasted energy prices relative to the March 2022 estimate or other 

unforeseen factors. 

• A decrease in annual or monthly release volumes from May through August 

The Secretary of the Interior or her Designee will consider the recommendations of the PI Team, 

including those to terminate implementation of an experiment, but retains sole discretion to 

decide how best to accomplish operations and experiments in any given year pursuant to the 

ROD and other binding obligations. 

Finally, the PI Team recommends further consideration by the GCDAMP to refine hypotheses, 

specify measures of success, and explore potential design improvements for the Bug Flows 

experiment. Such consideration would be subject to direction from the Secretary’s Designee and 

pursued in a manner consistent with the operating procedures of the AMWG and the TWG. 

The purpose of this memorandum is to transmit these technical recommendations regarding 2022 

implementation of the Bug Flows experiment to the Glen Canyon Leadership Team for 

Implementation of Experiments (Leadership Team) under the LTEMP and to DOI in accordance 

with the LTEMP Record of Decision (ROD). The PI Team includes technical representatives 

from National Park Service (NPS), U.S. Fish and Wildlife Service (Service), the Bureau of 

Indian Affairs (BIA), U.S. Geological Survey (USGS) Grand Canyon Monitoring and Research 

Center (GCMRC), the Bureau of Reclamation (Reclamation), WAPA, Arizona Game and Fish 

Department (AZGFD), and one liaison from each of the seven Colorado River Basin States 

(States) and the Upper Colorado River Commission (UCRC). 

In January 2022, the PI Team began meeting regularly to discuss LTEMP flow experiments with 

the potential for implementation in 2022. Deliberations specific to the Bug Flows experiment 

took place from mid-February through mid-April, with a recommendation targeted for Friday, 

April 8. The PI Team evaluated the potential implementation of the experiment, including the 

latest data from agency experts, and considered multiple issues in making its recommendations, 

as summarized below. The Secretary of the Interior or her Designee will consider the 

recommendations of the PI Team but retains sole discretion to decide how best to accomplish 

operations and experiments in any given year pursuant to the ROD and other binding obligations. 

II. Introduction 

Bug Flows are a flow experiment that consists of steady, low weekend releases from Glen 

Canyon Dam and normal fluctuating releases for hydropower during weekdays. The purpose of 

these experimental flows is to identify whether this type of operation can improve the 

abundance, diversity, and stability of aquatic insect populations, thereby increasing aquatic insect 

prey available for endangered humpback chub (Gila cypha), other native fishes, and the sportfish 

rainbow trout (Oncorhynchus mykiss), as well as for terrestrial wildlife such as bats, lizards, and 

birds. Table 4 in Appendix B of the LTEMP ROD summarizes implementation criteria for 

LTEMP experiments, and an excerpt of the criteria for Bug Flows is provided below (Table 1). 

2 
 

 

 

 

 

Table 1. LTEMP Implementation Criteria for the Bug Flows Experiment 

a Triggers will be modified as needed during the 20-year LTEMP period in an adaptive manner through processes 

including ESA consultation and based on the best available science utilizing the experimental framework for each 

alternative. 

b Annual determination by the DOI. Any implementation will consider resource condition assessments and resource 

concerns using the annual processes described in Sections 1.3 and 1.4. 

c Suspension of experiment if the DOI determines effects cannot be mitigated. 

g The duration and other characteristics of experimental macroinvertebrate production flows could be adjusted based 

on the results of initial experiments. 

Source: 2016 LTEMP ROD, Appendix B, Table 4 – Implementation Criteria for Experimental Treatments of 

Alternative D 

The Bug Flows experiment was implemented at Glen Canyon Dam from May through August 

for three consecutive years: 2018, 2019, and 2020. The steady weekend flows of Bug Flows were 

originally conceived as a means of providing more favorable conditions for aquatic insects to lay 

eggs along the Colorado River downstream from Glen Canyon Dam. These weekend flows are 

designed to be similar to daily minimum flows on the weekdays. This flow regime eliminates 

stage change in the river on the weekends, thus preventing aquatic insect eggs laid along the 

river margins from drying out. Additional research indicates that the more stable, lower weekend 

flows provided by Bug Flows also increase gross primary production (GPP) of algae in the river 

and promote enhanced emergence of adult aquatic insects on weekends. These effects are 

thought to both increase the food available for aquatic insect larvae and promote increased egg 

laying during these more favorable low flow conditions. As such, the steady low flow conditions 

provided on weekends during Bug Flows may have further, synergistic effects on aquatic insect 

populations beyond their original focus solely on reducing egg mortality. 

III. Recent Findings: Synthesis Report and Science Advisors Review 

The experiment was initially conceived by GCMRC scientists, as stated in the LTEMP, as 

targeting two to three consecutive years as a test of the original egg-laying hypothesis. Following 

these three consecutive years of Bug Flows implementation, the PI Team recommended against 

implementing Bug Flows in 2021. The recommendation was driven by multiple factors including 

estimated increases in the cost of the experiment to the hydropower resource relative to prior 

years and by the stakeholders’ desire to have GCMRC synthesize knowledge and learning from 

the first three replicates of the Bug Flows experiment before undertaking additional 

experimentation. The PI Team identified several “next step” action items that would support its 

consideration of Bug Flows in future years. 

3 
 

 

 

To inform discussion of potential future implementation of the Bug Flows experiment, the PI 

Team recommends, by consensus, the following next steps for DOI to consider: 

o The PI Team commits to document its considerations in a memo to DOI and the LTEMP 

Leadership Team. 

o Request that GCMRC state resource implications for non-implementation of Bug Flows 

in water year 2021. 

o Request that GCMRC complete a report by January 2022 summarizing experimental 

findings and discuss how the observations of non-implementation compared to the 

predictions. 

o Request that WAPA provide additional information regarding purchase power cost 

estimates, including assumptions and uncertainty, such that effects to hydropower are 

minimized if Bug Flows are implemented in the future. 

o Request that the Science Advisors Program establish and convene an independent review 

panel to evaluate the Bug Flows experiment in achieving its objective and to develop 

opportunities for further experimentation. 

Each of these actions items has been completed in preparation for 2022 PI Team discussion. 

GCMRC produced a synthesis report in fall 2021 and workshops were convened through the 

GCDAMP Science Advisor Program to discuss their findings with a panel of four internationally 

recognized freshwater science advisors. These workshops took place on October 28 and 

November 4, 2021 and featured presentations, question-and-answer periods, and discussions that 

included stakeholders. Key findings from the Bug Flows synthesis report included: 

1. Approximately 25% greater emergence of adult aquatic insects (midges) from the 

Colorado River during steady weekend Bug Flows compared to weekday fluctuating 

releases (i.e., canyon-wide average of 161 midges/hr for weekdays compared to 207/hr 

for weekends, a statistically significant difference). 

2. The abundance of caddisflies increased by 400% riverwide in two of three years that Bug 

Flows were conducted. Caddisflies have been rare in Grand Canyon and improving 

conditions for them was a primary objective of the experiment. These increases are 

statistically significant (e.g., error bars for these years do not overlap at all with years 

from pre-Bug Flows baseline) but cannot be definitively attributed to the Bug Flows 

experiment owing to confounding of these years with low sediment conditions that are 

also favorable to aquatic insects (see discussion in Status of Resources, below, for 

additional information). 

3. Modeling prior to the experiment suggested that a ~30% increase in non-biting midges, a 

common type of aquatic insect, might be realized riverwide if Bug Flows was successful. 

However, contrary to predictions, no increases in the abundance of midges were observed 

during the three-year Bug Flows experiment compared to pre-Bug Flows baselines across 

multiple long-term datasets (i.e. invertebrate drift data spanning 2008-2020, community 

science light trap data spanning 2012-2020). 

4 
 

 

 

 

 

 

 

4. Algae production increased by 56% in Marble and Grand Canyon during Bug Flows, 

resulting in an additional 200 metric tons of algae-carbon per year to sustain food webs. 

5. Anglers captured an average of 1.7 more rainbow trout per day during Bug Flows 

compared to weekday fluctuating flows in a study of volunteer anglers conducted by 

GCMRC (average of 5.1 trout per angler during weekday flows compared to 6.8 trout per 

angler during weekend flows, which is a statistically significant difference). 

The Science Advisor panel submitted their review of the Bug Flow experiment and synthesis 

report to Reclamation on January 4, 2022. The Science Advisors provided varied advice on the 

analyses and monitoring carried out by GCMRC scientists and suggested potential alterations to 

the design and implementation of Bug Flows moving forward. GCMRC is currently preparing an 

updated synthesis report based on the recommendations of the Science Advisor panel; see 

Section V. Assessment of Resources, for additional analysis of monitoring data from the 

experiment. However, throughout this diverse feedback and suggestions for improvements, there 

was uniform support from the Science Advisors for additional replicates of the Bug Flows 

experiment. This recommendation by the Science Advisors for additional replicates was 

grounded in their conclusion that 1) Bug Flows were successful at achieving experimental 

objectives stated in the LTEMP to “Improve food base productivity and abundance or diversity 

of mayflies, stoneflies, and caddisflies,” and 2) additional replicates would reduce uncertainties 

concerning treatment effects on aquatic insects and underlying mechanisms. 

As noted by the Science Advisors, a fourth replicate of the Bug Flows experiment would help 

address key uncertainties remaining from the first three years of Bug Flows by further 

disentangling the effects of hydroclimatic and other physical conditions from experimental flow 

conditions, particularly as they relate to aquatic insect response. Identifying linkages between 

Bug Flows and native fish populations is central to the long-term goals of Bug Flows as stated in 

the LTEMP. 

IV. LTEMP Process for Implementing Experiments 

The 2016 LTEMP ROD provides the framework for implementing flow experiments at Glen 

Canyon Dam. The purpose of LTEMP experiments is to leverage adaptive management to better 

protect, mitigate adverse effects, and improve resources downstream of Glen Canyon Dam, 

while complying with relevant laws. Ongoing research and monitoring through the Glen Canyon 

Dam Adaptive Management Program (GCDAMP) ensures the best science and data are available 

for making decisions related to flow experiments. 

Under the LTEMP ROD, the DOI may conduct flow experiments, such as Bug Flows, at Glen 

Canyon Dam when resource conditions warrant and if it is determined that there will not be 

unacceptable adverse impacts to other resources. 

Prior to implementation of any experiment, the relative effects of the experiment on the 

following resource areas will be evaluated and considered: (1) water quality and water 

delivery, (2) humpback chub, (3) sediment, (4) riparian ecosystems, (5) historic 

properties and traditional cultural properties, (6) Tribal concerns, (7) hydropower 

5 
 

 

 

 

 

 

 

production and WAPA’s assessment of the status of the Basin Fund, (8) the rainbow trout 

fishery, (9) recreation, and (10) other resources. 

--P. B-8, Implementation Process for Experiments Under Alternative D, 2016 LTEMP ROD 

The process for recommending experiments under the LTEMP, which has been used for past 

experiments and has been followed here, involves outreach to GCDAMP partners through 

regular meetings and additional notification to Tribes inviting consultation. The process also 

involves coordination with the PI Team to plan for the possible experiment, evaluate the status of 

resources, and make the technical recommendation of whether to conduct an experiment. The PI 

Team presents its recommendation to the Leadership Team, which makes a recommendation to 

DOI. The Secretary’s Designee to the Adaptive Management Work Group (AMWG) is the chair 

of the Leadership Team and may make the decision for DOI regarding the experiment, 

as delegated by the Secretary of the Interior. 

V. Hydrologic and Operational Uncertainty 

Lake Powell elevation as of March 5, 2022, was 3,523.02 feet, which is below the critical 

elevation threshold of 3,525 feet outlined in the Drought Response Operations Agreement. 

Elevation 3,525 feet provides a 35-foot buffer prior to reaching the minimum power pool 

elevation of 3,490 feet. The April 2022 final inflow forecast of 4,100 thousand acre-feet (kaf) is 

64 percent of average and decreased 500 kaf in volume from the forecast provided the prior two 

weeks. Conditions are expected to worsen over the summer with continued warm and dry 

conditions and Reclamation’s 2-year Colorado River Mid-term Modeling System projections 

indicate that Lake Powell could drop below 3,490 feet before the end of this calendar year – 

leading to cessation of all hydropower at Glen Canyon Dam. For these reasons, considerable 

uncertainty exists regarding operations of the Initial Unit facilities in the Upper Colorado Basin 

(Flaming Gorge, Blue Mesa, Navajo and Glen Canyon Dams) for the remaining months of water 

year 2022. For the purposes of this technical assessment, the total annual release volume from 

Glen Canyon Dam in water year 2022 is assumed to be 7.48 million acre-feet (maf). Operational 

adjustments may occur at Glen Canyon Dam that require additional coordination and analyses of 

alternatives by the PI Team to determine if continued implementation makes sense under 

changing conditions. 

VI. Hydrograph Alternatives 

By releasing stable and low flows every weekend, Bug Flows are intended to provide two days 

of ideal egg-laying conditions each week for aquatic insects that lay their eggs along river 

margins (Kennedy and others, 2016, Miller and others, 2020). From 2018-2020, technical 

experts at GCMRC and WAPA coordinated the design of the experiment to optimize the benefits 

for aquatic insects throughout Glen, Marble, and Grand Canyons (the Canyon) while minimizing 

negative impacts to hydropower. In 2019 and 2020, a Bug Flows hydrograph that incorporated 

weekend steady low flow releases that were 750 cubic feet per second (cfs) higher than weekday 

low flow releases in all months (May – August) was implemented (see Figure 1). This flow is 

similar to the Bug Flows hydrograph implemented in 2018, when a 1,000 cfs increase on 

weekends was implemented. Models of egg-laying developed by GCMRC technical experts 

indicated that hydrographs featuring this type of weekend offset would optimize insect egg6 
 

 

laying benefits at sites around the Little Colorado River confluence and sites downstream while a 

hydrograph without this offset (i.e., H0) would optimize egg-laying benefits in Glen Canyon near 

the dam and these benefits would diminish in the downstream direction. A hydrograph with a 

negative offset (H-250) would not optimal benefits at any sites, where optimal is defined as no 

difference between weekend steady flows and weekday daily minimums. 

Figure 1. Example hydrograph from August 2020 under base operations (no Bug Flows, dark blue) and 

Bug Flows (H750, green) scenarios. 

In response to concerns regarding the rising cost of the experiment, particularly estimated 

purchase power costs, GCMRC and WAPA proposed three hydrograph alternatives that had 

potential to reduce negative impacts to hydropower while still meeting objectives for ecosystem 

benefits and learning. These alternatives shifted the weekend offset with variations surrounding 

the base operations scenario for the May through August period (see Figure 2 and Table 2). 

WAPA provided a cost estimate for each alternative relative to base operations releases during 

the May through August bug flow implementation window (see Figure 3). The H750 alternative 

provides scientific replication as recommended by the science advisors at an increased cost of 

approximately $180,000 as compared against the H-250 alternative and $170,000 as compared 

against the H1 alternative. 

7 
 

 

 

Figure 2. Example hydrograph from May 2022 under base operations (no Bug Flows, dark blue dashes); 

H750 Bug Flows (green); H1 Bug Flows (light blue); and H -250 Bug Flows (orange) scenarios. 

Table 2. Summary of bug flow hydrograph alternatives considered and the minimum and maximum 

hourly releases under the base operations (no bug flows), H1, H-250, and H750 bug flow alternatives. 

8 
 

 

 

 

 

 

 

 

Figure 3. Cost estimate for each Bug Flows hydrograph relative to the base operations scenario for H1 

Bug Flows (light blue), H -250 Bug Flows (orange) and H750 Bug Flows (green) in millions of dollars. 

VII. Assessment of Resources 

This section summarizes the assessment of resources and expected effects of a Bug Flows 

experiment. 

Aquatic foodbase 

The objective of the Bug Flows experiment as described in LTEMP is to, “Improve food base 

productivity and abundance or diversity of mayflies, stoneflies, and caddisflies.” The design of 

the Bug Flow experiment was informed by GCMRC research showing load following operations 

create a life history bottleneck for aquatic insects through acute mortality of insect eggs. The 

design of the Bug Flows experiment was also informed by ecological insights and hydropower 

impacts of prior steady flow experiments in 2000 and 2008-2012. The 2000 experiment involved 

120 days of steady flow during summer months, but had a major impact on the hydropower 

resource. The 2008-2012 experiment involved 60 days of steady flow per year from SeptemberOctober. This experiment reduced impact to the hydropower resource compared to the 2000 

experiment, but benefits to biological resource responses were somewhat constrained because 

natural processes and biological activity are natural in decline at this time of year. Thus, the Bug 

Flow experiment sought to mitigate egg mortality caused by daily fluctuations in the least 

impactful and most cost-effective way possible while still targeting months of high biological 

activity and rates of natural processes. The purpose of the Bug Flows experiment is to provide 

favorable egg laying conditions during weekends from May-August, when egg laying activity is 

highest and hydropower impacts of steady flows are reduced compared to weekdays. 

In 2018 and prior to Bug Flows implementation, GCMRC technical experts developed 

predictions that would be used to evaluate success of a three-year test of the Bug Flows 

experiment. These included the predictions that, over a three-year experiment, a) midges would 

exhibit modest increases and b) caddisflies would exhibit major increases. Contrary to 

9 
 

 

 

 

 

 

 

 

 

predictions, midge abundance did not increase during the 3-year experiment (see Figure 4) but 

consistent with predictions, a 400% increase in caddisflies was measured in two of three Bug 

Flow years compared to the pre-Bug Flow baseline. The large increase in caddisflies was 

noteworthy and highlighted in GCMRC’s synthesis report, because it directly supports the 

LTEMP objective to “Improve...abundance or diversity of...caddisflies.” 

Monitoring and modeling from 2018-2019 also demonstrated that water clarity and subsequently 

the rate of algae production increased during the Bug Flows experiment (COVID-19 prevented 

this same data collection in 2020); algae is the foundation of aquatic food webs and a primary 

food for aquatic insects and some native fish. During weekends when Bug Flows were 

conducted, an increase in rates of algae production of roughly 56% canyon-wide was observed 

compared to weekday rates. This increase in algae production on clear-water weekends in May 

and June conservatively translates to an additional 200 metric tons of algae energy available per 

year to sustain aquatic food webs. This ecosystem benefit is noteworthy and was highlighted in 

GCMRC’s synthesis report. 

In 2021 following cessation of Bug Flows, the abundance of midges captured in community 

science light traps declined by 50% while the abundance of caddisflies declined by 25% relative 

to the preceding year (note that caddisfly abundance in 2021 remained above the pre-Bug Flows 

baseline). Multiple environmental (e.g., suspended sediment, water temperature, nutrients, GPP) 

and flow drivers affect aquatic insect populations and abundance measured in light traps. 

Suspended sediment concentrations in particular were a major explanatory variable of insect 

growth rates (timing of emergence) and insect abundance (average catch rate in light traps) from 

2012-2020, low suspended sediment and Bug Flow treatments and large increase in caddisflies 

observed in 2018 and 2020. Thus, with only the data from 2012-2020, it was impossible to fully 

disentangle the role of low sediment from Bug Flow treatment effects in driving caddisfly 

increases in these years. In other words, the experimental design matrix was somewhat 

confounded, where the design matrix refers to the unique combination of environmental 

conditions that occurs during a given year of the experiment or during “control years” when the 

experiment is not conducted. Sediment conditions in 2021 were lower than 2018 and 2020 but 

Bug Flow treatments were ceased, which means that 2021 improved the design matrix and 

helped disentangle sediment from Bug Flow effects. The decline in midge and caddisfly 

abundance that were documented in 2021 despite favorable sediment conditions provides 

additional evidence that the 2018-2020 Bug Flows was likely supporting insect populations. 

GCMRC technical experts and cooperators at Oregon State University are developing life history 

model for aquatic insects that will more rigorously quantify these interpretations of light trap 

data, including quantitatively disentangling the role of environmental drivers (ie. nutrients, GPP, 

sediment, water temperature) from the effects of Bug Flow treatments in influencing aquatic 

insect population dynamics. 

10 
 

 

 

 

 

Figure 4. Graph showing abundance of key aquatic insects (midges and caddisflies) captured in 

community science light traps prior to Bug Flows (2012-2017), during Bug Flows (2018-2020), and one 

year after discontinuation (2021). During 2018-2020 Bug Flows, caddisfly abundance increased by as 

much as 400% compared to the pre-Bug Flow baseline while midge abundance remained unchanged. In 

2021 following cessation of Bug Flows, midge abundance declined by 50% and caddisfly abundance 

declined by 25% relative to the prior year, although caddisfly abundance remained above the pre-Bug 

Flows baseline. Data are based on a mixed effects model of aquatic insect abundances that includes the 

geomorphic reach, month, and year in which the sample was collected, and error bars are one standard 

error from the mean. Provisional data, do not cite. 

Invasive species 

Nonnative invasive species were not predicted to benefit from the Bug Flows experiment, but 

large increases in the abundance of invasive Brown Trout in Glen Canyon starting around 2013 

and through 2020 led to a reevaluation of this prediction during 2021 PI Team discussions. 

11 
 

 

 

 

Subsequent analysis of Brown Trout data demonstrated that these Brown Trout increases were 

unlikely to be arising because of Bug Flows (Yackulic and others, 2021). 

Warm-water invasive fish such as smallmouth bass are of great concern to managers. Warmwater invasives have been absent or maintained at low levels within the Colorado River in Glen, 

Marble, and Grand Canyons largely because of cool water temperatures that are well below 

optimal for growth and reproduction. However, low elevations in Lake Powell reservoir have 

increased the likelihood of passage of smallmouth bass and other warm-water invasives to the 

downstream ecosystem; increased water temperatures have also increased the likelihood of 

smallmouth bass and other warm-water invasives becoming established in Grand Canyon 

moving forward. 

Expert opinion among multiple fishery biologists on the Smallmouth Bass Task Force is that 

testing Bug Flows in 2022 would only lead to a small increase in the likelihood of smallmouth 

bass establishment, with fish passage and water temperatures being the biggest factors 

determining whether smallmouth bass become established. The predicted increases in GPP and 

aquatic insect diversity associated with Bug Flows may provide some small benefits to 

smallmouth bass in the event that passage increases and water temperatures are well-suited, but 

increases in GPP or aquatic insect diversity arising from Bug Flows are unlikely to be a 

determinative factor in whether smallmouth bass become established compared to degree of 

passage and temperature. Additionally, improvements in GPP and insect diversity that are 

predicted with Bug Flows are expected to benefit native fish populations including humpback 

chub, whose populations are limited by the low abundance and diversity of aquatic insect food 

resources in some segments and times of year (Cross and others, 2013). 

Endangered humpback chub and other native fish abundance 

Although the humpback chub population in the Little Colorado River aggregation is above the 

Tier-1 threshold of 9,000 adults identified in the Biological Opinion for the LTEMP EIS, the 3-

year average of sub-adults has been below the trigger for the last two years. Specifically, the 3-

year average (2019-2021) of juvenile humpback chub in the Colorado River mainstem from river 

mile 63.45-65.2 was estimated at 433, which is well below the 810 necessary to prevent 

requirements to take additional action. In response to the trigger, 535 humpback chub were 

translocated above Chute Falls in 2021 where fish generally grow faster and have higher survival 

rates. Although the translocation action is expected to improve humpback chub survival in the 

long-term, an immediate impact on the trigger was not expected. The humpback chub 

population continues to be monitored and additional conservation actions will be planned in the 

spring once larval recruitment data are available. 

A long-term goal of Bug Flows is to have a positive, indirect effect on humpback chub and other 

native fish through increases in the diversity and production of aquatic insects that are the 

primary prey for these fish. Year-to-year variation in water temperature, sediment, and nutrients 

affects native fish growth and should be accounted for before quantifying the marginal effect of 

Bug Flows. Additional testing of the Bug Flow experiment in 2022 combined with planned 

studies of native fish diets and feeding habits will help identify whether enhancements to natural 

processes that have been documented during Bug Flows experimentation (i.e, increased GPP, 

12 
 

 

 

 

 

 

 

 

increased caddisfly abundance) are contributing to native fish growth and production. Recent 

modeling shows that Flannelmouth sucker growth is positively related to GPP. The springtime 

(May and June) increase in GPP due to Bug Flows is estimated to have increased the growth of 

individual Flannelmouth suckers by about 1.6 mm per month (Hansen, 2021). Further, additional 

years of Bug Flow experimentation combined with robust mark-recapture studies of native fish 

vital rates (i.e., Juvenile Chub Monitoring-JCM) will allow GCMRC to quantify the effect of 

Bug Flows on humpback chub vital rates including growth and survival. 

Hydropower production, marketable capacity, and Basin Fund status 

WAPA has firm electric power contracts and must meet these contract amounts either with 

generation from Colorado River Storage Project powerplants or from purchases from the 

wholesale electrical market. During the Bug Flows experiment, low volume releases from Glen 

Canyon Dam during the weekend require WAPA to purchase extra electric power to meet 

contract amounts. Some of these expenses are offset with extra electrical production during the 

weekdays. Using forecasted energy prices obtained in March 2022, WAPA estimates that the 

expense of a Bug Flows experiment in 2022 would be about $1,401,000 based on current data. 

This is roughly four times the amount of prior year cost estimates, as shown in Table 3, and is a 

direct result of the projected high energy prices and the difference between the on and off peak, 

particularly in July and August. Over the course of the last three years we have seen this trend in 

energy price increases, as seen in Table 3 as well. 

Table 3. Estimated and Actual Purchase Power Costs Associated with the May to August Bug Flows 

Experiment Relative to Standard Operations at Glen Canyon Dam 

Implementation Year Estimated Cost Actual Cost 

water year 2018 $335,000 $165,000 

water year 2019 $332,000 $327,000 

water year 2020 $407,000 $1,200,000 

water year 2021 $1,021,000 N/A 

water year 2022 $1,401,000 N/A 

Summer energy prices are uncertain and may be impacted by a reduction in baseload capacity in 

the West. 

WAPA projects that the Upper Colorado River Basin Fund will have a balance of $83M at the 

end of fiscal year 2022. This projection considers the decrease in funding requirements for BOR, 

no non-reimbursable funding for environmental programs, and does not include any potential 

funding from the Bipartisan Infrastructure Law (BIL). The Basin Fund balance does not meet 

WAPA’s target for an end of year balance. 

Rainbow Trout fishery 

The LTEMP ROD suggests that the Bug Flows experiment may have an indirect effect on the 

Lees Ferry rainbow trout fishery through increases in the diversity and production of aquatic 

insects, which are an important prey item for these fish. Formal analysis and modeling of 

rainbow trout growth and condition data suggest that climatic drivers are having a stronger effect 

on fish vital rates than Bug Flows over the period of record (2011-2021); Korman unpublished 

13 
 

 

 

 

 

 

 

manuscript). The analysis also shows how Bug Flows are confounded with phosphorus 

concentrations since all three years where Bug Flows were conducted were low phosphorus 

years. Preliminary results suggest that Bug Flows have a weak positive effect on rainbow trout 

growth in length. The effect on growth could be made more certain if Bug Flows were conducted 

during a year where springtime phosphorus concentrations in Glen Canyon were higher; it is 

unclear whether 2022 will have low or high phosphorus concentrations. 

To assess whether the 2018-2019 Bug Flows experiment had a significant effect on angler catch 

rates (catch per unit efforts [CPUE] fish/hour), AZGFD analyzed data from boat angler surveys 

conducted from April to September in 2018 and 2019 to determine if angler CPUE was higher on 

days with low, steady flows (weekends). Stepwise model selection showed that bug flows 

explained most of the variance in angler CPUE compared to other significant factors (day of 

year, guided, year, and interactions) (Rogowski 2018). Angler catch rates were higher on 

weekends particularly in the early months of the study (i.e. May, June) although this relationship 

was not observed by August where CPUE was lower on weekends. Although AZGFD’s long 

term monitoring was not designed specifically to investigate whether flow experiments achieve 

their objectives, creel data suggests Bug Flows influenced the quality of the recreational fishing 

experience in Lees Ferry. Similar results were obtained in a GCMRC study involving volunteer 

anglers with higher catch rates observed on weekends compared to weekdays. In AZGFD creel 

surveys, many anglers commented that they enjoyed fishing more during low, steady flows 

compared to weekdays. Anglers reported that during weekend low flows (~8,900 cfs) gravel bars 

were shallow and it was easier to place lures or flies where fish were located. Conversely, guides 

and anglers expressed that weekday high water levels made it difficult to get fishing gear into 

habitat where fish were located, and that fishing success declined when the water was rising or 

falling. Discharges below 8,000 cfs can inhibit or complicate navigation for boat anglers 

traveling upstream from Lees Ferry as gravel bars become more exposed; however, the proposed 

hydrograph for 2022 Bug Flows should provide enough discharge as to not impede navigation. 

Overall, positive effects on recreational fishing are anticipated from a 2022 Bug Flows 

experiment. 

Riparian vegetation 

There is no evidence that the Bug Flows experiment significantly impacts riparian vegetation 

resources. The primary impact is to slightly extend the active channel, which is the zone of daily 

inundation, upslope on weekdays. This may slightly extend the suitable habitat for obligate 

wetland herbaceous species that respond positively to inundation, though longer-lived perennial 

species are unlikely to respond significantly to this short-term increase in inundation (Butterfield 

and others, 2018). Weekend low flows are also unlikely to have a significant impact, as sufficient 

water for plant metabolic activity is likely to be retained within sediments for the 2-day duration 

of the low flows. 

Sediment resources 

Based on a detailed analysis of prior year data and consistent with predictions in the LTEMP, the 

Bug Flows experiment exports around 2-7% more sand in a given month relative to normal 

operations. This increase in sediment transport during Bug Flows arises because hydropower 

fluctuations are increased during weekdays to make up for less water being released during low 

weekend Bug Flows, combined with the fact that the relation between sediment transport and 

14 
 

 

 

 

 

discharge is non-linear. Due to lower release volumes in 2022, it is expected that Bug Flows will 

have similarly small effects on sediment transport compared to routine operations. 

Cultural Resources 

Impacts from Bug Flows are anticipated to be minimally beneficial to archaeological site 

condition and stability, because sand bars may have an opportunity to dry out and windy 

conditions may allow for the redistribution of sand from the bars to high elevation areas 

containing archaeological sites. The lower, slower steady weekend flows may also result in oarpower river runners spending more time on the water and less time on shore, reducing the 

potential for impacting archaeological sites though visitation. 

Grand Canyon Whitewater Recreational Rafting 

Impacts to the whitewater rafting recreational experience are expected to be negligible. While the 

weekend steady flows may require boaters to spend slightly more time rowing and less time on 

shore, the slightly higher low flows on weekends and weekdays may improve the navigability of 

some rapids. Also, the steady, low weekend flows may allow for a more consistent campsite area 

during the weekend flow period and minimize the need to move and re-tie boats during the night. 

VIII. Monitoring Plan and Hypotheses 

If a Bug Flows experiment is implemented in 2022, GCMRC and cooperators will monitor 

Colorado River food web responses using standardized methods described in the 2021-2023 

Triennial Budget and Work Plan. These efforts include a network of dissolved oxygen sensors 

for Canyon-wide measurements of GPP, Canyon-wide sampling of adult aquatic insects through 

community science light trapping, an annual aquatic invertebrate benthic (riverbed) sampling 

river trip targeting larval life stages of insects, and seasonal mark-recapture studies of growth 

and survival for humpback chub, rainbow trout, and other fish species. These studies and models 

will provide the GCDAMP with a comprehensive picture of how a 2022 Bug Flows experiment 

affected natural processes that sustain Colorado River food webs including key fish species. 

Starting in 2022, GCMRC will also add non-lethal seasonal diet sampling of native and nonnative fishes to assess the potential effect of Bug Flows on native fish feeding habits. 

Additionally, cooperators at Oregon State University are developing life history models for 

aquatic insect populations that will help disentangle the role of the Bug Flows experiment from 

other flow (e.g., annual volume, monthly volume) and environmental drivers (e.g., water 

temperature, sediment conditions, nutrients, etc.) of aquatic insect populations. Importantly, 

these models will provide insight into the role of improved egg laying in driving aquatic insect 

response to Bug Flows compared to potential benefits of steady weekend Bug Flows on other 

aquatic insect life stages (i.e., larvae/nymph, pupae, adult). Collectively, this monitoring 

combined with an additional replicate of the Bug Flow experiment in 2022 will inform potential 

experimental design modifications and considerations that were discussed during Science 

Advisor review and recent PI Team meetings, including increasing or decreasing the duration of 

the experiment and altering target months. Note that if the Bug Flows experiment is not 

implemented in 2022, all of the above monitoring will still occur. See 2021-2023 Triennial 

Budget and Work Plan for more detail. 

15 
 

 

 

 

Quantifiable hypotheses for the resource outcomes of a Bug Flows experiment in 2022 are based 

broadly on prior results and our current best understanding of the interactions of environmental 

conditions, Bug Flows impacts, and organismal ecology. The predictions and hypotheses 

outlined below are based on an H-level of 750 (i.e., weekend flows are offset 750 cfs higher than 

weekday minimums) across all four months of the 2022 Bug Flow experiment. 

An alternative H-level of 0 (i.e., no offset, weekend minimum identical to weekday minimum) 

has also been discussed owing to potential to reduce impacts to the hydropower resource. In 

addition to reducing impacts to hydropower, an H0 design would shift the location of greatest 

egg-laying benefits to Glen Canyon and Upper Marble Canyon compared to the H1000 and 

H750 designs that were tested from 2018-2020, which optimizes egg-laying benefits at the Little 

Colorado River confluence and sites farther downstream; the offset determines which segment of 

river experiences optimal egg-laying benefits owing to how daily fluctuations propagate and 

change shape with distance downstream. A hydrograph with a negative offset (H-250) would not 

provide optimal insect egg laying benefits at any sites, where optimal is defined as no difference 

between weekend steady flows and weekday daily minimums. Below we outline predictions for 

a 2022 Bug Flow with an H-level of 750, but we also discuss possible differences in ecological 

outcomes under an H-level 0: 

1. If Bug Flows are tested in 2022, caddisfly abundance is predicted to resemble levels in 

2018 and 2020 (the years of highest abundance). Testing Bug Flows this year (2022) will 

improve the design matrix of the experiment (i.e., the unique combination of 

environmental conditions that occurs during a given year of the experiment or during 

“control years” when the experiment is not conducted). Specifically, based on current 

conditions a test of Bug Flows in 2022 will likely help disentangle the relative influence 

of sediment loads from experimental Bug Flows effects on caddisfly. Fall/winter 

conditions in 2021 included high sediment inputs, and this is associated with low 

caddisfly abundance in the following spring. Thus, a test of Bug Flows in 2022 sets up a 

unique contrast that will disentangle effects: if sediment inputs are an overarching filter 

on caddisfly populations, abundances in summer 2022 should be low; alternately, if Bug 

Flows effects are a stronger driver of caddisfly abundance and population growth, 

observed abundances in 2022 should be high. 

2. If Bug Flows are tested in 2022, midge abundance is predicted to resemble levels 

observed during Bug Flows from 2018-2020. This prediction is informed by the 

observation that midge abundance declined by ~50 percent in 2021 following cessation of 

Bug Flows compared to the 2012-2020 baseline. In other words, Bug Flows may have 

been supporting higher midge abundance from 2018-2020 than would have otherwise 

occurred, but owing to the design matrix (i.e., low nutrient concentrations during 2018-

2020) this effect was masked and statistically indistinguishable from the 2012-2017 

baseline that was available for comparison; adding a Bug Flows experiment for the year 

2022 provides a path for learning to address the extent to which the 2021 decline (and 

potentially the stability of 2018-2020) was indeed due to a positive effect of the 

experiment on midge abundance. 

16 
 

 

 

 

 

 

 

 

 

 

 

3. Rainbow trout vital rates in 2022 are predicted to be more influenced by the elevated 

temperatures predicted in Glen Canyon than by Bug Flows. With an H-level of 0, we 

expect 2022 Bug Flows to have a greater positive effect on rainbow trout in Glen Canyon 

than has been observed in previous years, since flows with an H-level of 0 are optimized 

for egg-laying in Glen Canyon. If springtime phosphorus concentrations are higher in 

2022 than in previous Bug Flows years, all of which have been low phosphorus, the 

additional year of Bug Flows will likely improve understanding of the small but positive 

effect of Bug Flows on rainbow trout growth rates. 

4. Canyon-wide rates of GPP are expected to increase with Bug Flows in 2022, possibly to a 

greater extent than in previous years. Rates of GPP increase as a function of water 

temperature, so the predicted warm water releases combined with the planned lower 

annual flow volumes will contribute to warmer water temperature canyon-wide, resulting 

in a more pronounced positive effect of Bug Flows on GPP canyon-wide. Elevated 

tributary sediment inputs during summer months could reduce any positive effect of the 

Bug Flow experiment on GPP, but we nonetheless still expect large canyon-wide 

increases in GPP under Bug Flows in May and June before tributary flooding begins. 

The 200 metric tons of additional algal-carbon reported during 2018 and 2019 Bug Flows 

testing uses only the months of May and June when these positive bug flow effects on 

GPP were most likely. The H-level 0 Bug Flows will also present an opportunity to test 

how a greater degree of weekend shoreline desiccation affects GPP at the weekly time 

step. Analysis of data from previous Bug Flows years shows no longitudinal trend in the 

Bug Flow effect, which would be expected if shoreline desiccation was important 

mechanism driving GPP response. 

IX. Coordination During Implementation and Experiment “Offramps” 

In recognition of uncertainty in WY 2022 hydrology, annual and monthly operations, and 

resource conditions, the PI Team will meet bi-weekly beginning the week of May 1st and 

continuing throughout implementation of the Bug Flows experiment to evaluate whether new 

conditions or unanticipated negative impacts have occurred or are likely to occur. Items that 

may warrant the PI Team to consider recommending termination of implementation include, 

but are not limited to: 

• Detection of juvenile smallmouth bass in Lees Ferry and/or observations that indicate 

the Bug Flows experiment could benefit smallmouth bass. 

• An increase to the estimated cost of the Bug Flows experiment to more than double the 

current estimated cost (i.e. an increase from $1.4M to $2.8M or more) that may result 

from increases in forecasted energy prices relative to the March 2022 estimate or other 

unforeseen factors. 

• A decrease in annual or monthly release volumes from May through August 

The Secretary of the Interior or her Designee will consider the recommendations of the PI 

Team, including those to terminate implementation of an experiment, but retains sole 

17 
 

 

discretion to decide how best to accomplish operations and experiments in any given year 

pursuant to the ROD and other binding obligations. 

In addition, members of the PI Team will continue to meet regularly with stakeholders 

throughout the implementation of the four-month experiment. This will occur through the 

regularly scheduled monthly Glen Canyon Dam operations coordination calls. Scientists 

conducting field surveys during the experiment and agency technical experts will report back on 

data collected and preliminary results to the Department and the GCDAMP at regularly 

scheduled meetings. Glen Canyon Dam operations will be adjusted accordingly in the event of 

unexpected impacts from Bug Flows. 

X. Safety Considerations 

Potential, but minimal effects on public health and safety could occur in conjunction with the 

Bug Flows experiment, primarily impacting recreational river users. The proposed minimum 

flows are within the range experienced by recreational users in the past and those currently 

expected on a monthly basis. Reclamation and NPS coordinate to ensure that safety measures are 

implemented and will provide public notice about the timing and purpose of the experimental 

flows. The three affected parks (Glen Canyon—GLCA, Grand Canyon—GRCA, and Lake 

Mead—LAKE) have coordinated communications plans, medical plans, and resource 

capabilities for search and rescue responses. Flow and stage change information will be provided 

via public media, the individual park websites, and by on-site NPS staff at Lees Ferry and 

Phantom Ranch. 

XI. Communications Plan 

If a Bug Flows experiment is implemented in 2022, the communications/public affairs aspect of 

these experimental flows will not include a public/media event at Glen Canyon Dam, and will 

include communications product development and media coordination. 

Reclamation’s Upper Colorado Basin – Interior Region 7 Public Affairs Office, in coordination 

with NPS, USGS, and WAPA public affairs contacts and the Department, will lead 

communications product development. If the Bug Flows experiment is approved, a detailed news 

release, for publication on or near the experimental Bug Flows start date, will be sent to convey 

the intent and timing of the experiment to media representatives and the public. This may be 

prepared for distribution by the Secretary's Office. Social media outlets will also be used to 

communicate with the public leading up to and during the event, including to share imagery of 

the experiment. 

XII. Consultation 

Reclamation and GCMRC presented much of the information in this report that was available at 

that time to the AMWG at its regular meetings, and at the GCDAMP Annual Reporting 

Meetings. An informational webinar and request for input regarding a potential 2022 Bug Flows 

18 
 

 

 

 

 

 

experiment was held for GCDAMP stakeholders on March 30, 2022. Written stakeholder 

comments have been attached to this report (Attachment B), for reference. 

On March 30, 2022, the required 30-day advance notification and offer for consultation was 

emailed to the Tribes and parties to the LTEMP cultural Programmatic Agreement of the 

potential for a Bug Flows experiment beginning May 1, 2022. As of the finalization of this 

report, no requests for consultation have been received. A follow-up notification will be sent 

electronically to stakeholders, including Tribes, following DOI decision regarding the 

implementation of a Bug Flows experiment in 2022. 

XIII. Reporting 

The PI Team will coordinate to report findings at the 2022 GCDAMP Annual Reporting Meeting 

in early 2023. In addition, the PI Team will report ongoing findings at meetings of the GCDAMP 

Technical Work Group (TWG) and Adaptive Management Work Group (AMWG). Reclamation 

has a commitment to provide an annual monitoring report to the FWS Arizona Ecological 

Services Office (AESO) in compliance with the 2016 Biological Opinion; this report will also 

include a summary of the effects of any flow experiments conducted under the LTEMP ROD. 

GCMRC and Reclamation will use the monitoring information and feedback from AESO and 

GCDAMP stakeholders to inform monitoring for future experiments, and to design and 

implement any measures necessary to address any adverse effects that may occur due to these 

flows. 

XIV. Planning for Future Experiments 

The three years (2018, 2019, 2020) of Bug Flows experimentation showed promising ecosystem 

benefits including increases in algae production and greater abundance of sensitive caddisflies. 

However, the link between caddisfly increases and Bug Flows is not definitive and contrary to 

predictions, midges have not increased during Bug Flows experimentation. Other noteworthy 

resource benefits include improved catch rates and higher angler satisfaction during Bug Flows 

weekends compared to fluctuating weekday flows. Significantly, the negative impact of the Bug 

Flows experiment on the hydropower resource increased each year owing primarily to increasing 

purchase power prices. 

It is critical to determine if the objective, as stated in the LTEMP ROD, can be met by the Bug 

Flows experiment and to ensure that there are no unacceptable adverse effects to other resources. 

PI Team deliberations in 2021 and in 2022 indicate that there may be experimental design 

alternatives that, with further development and analysis, could better meet these objectives. To 

inform discussion of potential future implementation of the Bug Flows experiment, the PI Team 

recommends further consideration by the GCDAMP to refine hypotheses, specify measures of 

success, and explore potential design improvements for the Bug Flows experiment. Such 

consideration would be subject to direction from the Secretary’s Designee and pursued in a 

manner consistent with the operating procedures of the AMWG and the TWG. 

The PI Team will meet in early 2023 to review the results of any 2022 implementation activities, 

and to begin coordination on the evaluation of resources and potential experiments that may be 

19 
 

 

 

 

 

 

conducted in 2023. In accordance with the LTEMP ROD, the Department may make the decision 

to conduct future flow-based experiments (High Flow Experiments, Bug Flows, Trout 

Management Flows, and Low Summer Flows) at Glen Canyon Dam if it is determined that there 

are no unacceptable adverse impacts on other resource conditions. Information and data from this 

or other experiments will be considered in future recommendations and decisions. 

XV. Conclusion 

Determining whether to recommend the Bug Flows experiment required coordination of many 

details and effective communication among technical staff from multiple agencies. In particular, 

the PI Team would like to acknowledge the contributions of staff at the GCMRC to support its 

deliberations regarding Bug Flows. The PI Team recognizes that the development and 

implementation of a Bug Flows experiment at Glen Canyon Dam requires significant staff time 

and resources. 

The PI Team has thoroughly evaluated the issues discussed above and has taken into 

consideration the information and analysis included in the LTEMP EIS and ROD. The PI Team 

has reached a recommendation to proceed with implementation of the Bug Flows experiment in 

2022 based on the careful assessment of resources and best available science. This 

recommendation does not reflect consensus; the Western Area Power Administration (WAPA) 

has substantial concerns with implementing a Bug Flows experiment in 2022 and does not 

support the recommendation. 

In recognition of uncertainty in WY 2022 hydrology, annual and monthly operations, and 

resource conditions, the PI Team would meet bi-weekly beginning the week of May 1st and 

continuing throughout implementation of the Bug Flows experiment to evaluate whether new 

conditions or unanticipated negative impacts have occurred or are likely to occur. 

The PI Team recommends further consideration by the GCDAMP to refine hypotheses, specify 

measures of success, and explore potential design improvements for the Bug Flows experiment, 

which will support potential implementation in future years. 

Attachments 

A. Final Recommendations Regarding Implementation of the Bug Flows Experiment 

in 2022, LTEMP Planning/Implementation Team, April 8, 2022 

B. Stakeholder Comments 

a. Colorado River Energy Distributors Association (CREDA) 

b. Fly Fishers International/Trout Unlimited (FFI/TU) Recreational Fishers 

20 
 

 

 

References 

Butterfield, B.J., Palmquist, E.C., and Ralston, B.E., 2018, Hydrological regime and climate 

interactively shape riparian vegetation composition along the Colorado River, Grand Canyon: 

Applied Vegetation Science, v. 21, no. 4, p. 572-583, https://doi.org/10.1111/avsc.12390. 

Cross, W.F., Baxter, C.V., Rosi-Marshall, E.J., Hall Jr, R.O., Kennedy, T.A., Donner, K., 

Wellard Kelly, H.A., Seegert, S.E.Z., Behn, K.E., and M.D. Yard, 2013, Food‐web dynamics in 

a large river discontinuum: Ecological Monographs v.83, no. 3: 311-337. 

Hansen, L.E., 2021, Factors influencing growth in the Grand Canyon Colorado River population 

of flannelmouth sucker (Catostomus latippinis). Masters thesis, Northern Arizona University. 

Kennedy, T.A., Muehlbauer, J.D., Yackulic, C.B., Lytle, D.A., Miller, S.W., Dibble, K.L., 

Kortenhoeven, E.W., Metcalfe, A.N., and Baxter, C.V., 2016, Flow management for hydropower 

extirpates aquatic insects, undermining river food webs: BioScience, v. 66, no. 7, p. 561-575, 

http://dx.doi.org/10.1093/biosci/biw059. 

Korman, J., and others, unpublished manuscript, Climate effects surpass experimental flow 

effects on the vital rates of a tailwater fish population 

Miller S.W., Schroer, M., Fleri, J.R., and T.A. Kennedy. 2020. Macroinvertebrate oviposition 

habitat selectivity and egg-mass desiccation tolerances: Implications for population dynamics in 

large regulated rivers. Freshwater Science. 39(3):584–599 

Rogowski, D.L., 2018, Do bug flows result in better fishing?—Adaptive Management Working 

Group presentation—August 22, 2018: Flagstaff, Ariz., Arizona Game and Fish Department, 

https://www.usbr.gov/uc/progact/amp/amwg/2018-08-22-amwg-meeting/attach_07.pdf. 

Yackulic, C, Korman, J., Tennant, L. Boyer, J. Yard, M, 2021, Brown trout population modeling. 

Annual Reporting Meeting January 2021. https://www.usbr.gov/uc/progact/amp/twg/2021-01-

22-twg-meeting/20210122-AnnualReportingMeeting-BrownTroutPopulationModeling-508-

UCRO.pdf 

21 
Attachment A

Final Recommendations Regarding Implementation of the Bug Flows 

Experiment in 2022, LTEMP Planning/Implementation Team, April 8, 2022
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Friday April 8, 2022 

LTEMP Planning and Implementation Team 

GCD Flow Experiment Deliberations – Bug Flows 2022 

Recommendation 

The LTEMP Planning/Implementation Team (PI Team) recommends that experimental 

Macroinvertebrate Production Flows (“Bug Flows”) be implemented at Glen Canyon Dam 

beginning May 1 through August 31, 2022. This recommendation does not reflect consensus: 

the Western Area Power Administration (WAPA) has substantial concerns with implementing a 

Bug Flows experiment in 2022 and does not support the recommendation; Arizona and New 

Mexico abstained; and the U.S. Fish and Wildlife Service and Arizona Game and Fish 

Department were not present for final deliberations. 

The PI Team has determined the Bug Flows experiment has the potential to improve food base 

productivity and aquatic insect diversity, with consequent benefits to native fish and ecosystem 

health also likely. The Science Advisors concluded that Bug Flows appeared to have met the 

experimental objectives described in the LTEMP (i.e., improve food base productivity and insect 

diversity) and that reducing uncertainties through additional experimentation would inform 

future design considerations. 

The PI Team also identified the potential for adverse effects to the hydropower resource. Using 

forecasted energy prices obtained in March 2022, the Western Area Power Administration 

estimates that the expense of a Bug Flows experiment in 2022 would be approximately $1.4M 

based on current data. The PI Team defers the determination of whether these effects are 

unacceptable to the Leadership Team and to the Department of the Interior. 

In recognition of uncertainty in WY 2022 hydrology, annual and monthly operations, and 

resource conditions, the PI Team would meet bi-weekly beginning the week of May 1st and 

continuing throughout implementation of the Bug Flows experiment to evaluate whether new 

conditions or unanticipated negative impacts have occurred or are likely to occur. Items that 

may warrant the PI Team to consider recommending termination of implementation include, 

but are not limited to: 

• Detection of juvenile smallmouth bass in Lees Ferry and/or observations that indicate 

the Bug Flows experiment could benefit smallmouth bass. 

• An increase to the estimated cost of the Bug Flows experiment to more than double the 

current estimated cost (i.e. an increase from $1.4M to $2.8M or more) that may result 

from increases in forecasted energy prices relative to the March 2022 estimate or other 

unforeseen factors. 

• A decrease in annual or monthly release volumes from May through August 

The Secretary of the Interior or her Designee will consider the recommendations of the PI 

Team, including those to terminate implementation of an experiment, but retains sole 
 

 

 

 

 

 

 

 

 

Friday April 8, 2022 

discretion to decide how best to accomplish operations and experiments in any given year 

pursuant to the ROD and other binding obligations. 

Finally, the PI Team recommends further consideration by the GCDAMP to refine hypotheses, 

specify measures of success, and explore potential design improvements for the Bug Flows 

experiment. Such consideration would be subject to direction from the Secretary’s Designee 

and pursued in a manner consistent with the operating procedures of the AMWG and the TWG. 

Recommendation Support 

Support: BIA, BOR, CA, CO, NV, UT, WY, UCRC, NPS, USGS 

Opposed: WAPA 

Abstained: AZDWR, NM 

Absent: AZGFD, FWS 

Planning and Implementation Team Members 

• National Park Service (NPS) 

• U.S. Fish and Wildlife Service (FWS) 

• Bureau of Indian Affairs (BIA) 

• U.S. Geological Survey (USGS) Grand Canyon Monitoring and Research Center (GCMRC) 

• Bureau of Reclamation (Reclamation) 

• Western Area Power Administration (WAPA) 

• Arizona Game and Fish Department (AZGFD) 

• 7 x Colorado River Basin States (AZ, CA, CO, NM, NV, UT, WY) 

• Upper Colorado River Commission (UCRC) 
Attachment B: Stakeholder Comments

1. Colorado River Energy Distributors Association

2. Fly Fishers International/Trout Unlimited Recreational Fishers
 

 

 

 

 

 

 

From: creda@creda.cc 

To: Fullard, Clarence D; Traynham, Lee E 

Cc: Pullan, Wayne G; cibarre@q.com; kevin@umpa.energy; jbrown@tristategt.org; creda@creda.cc; "Bennett Raley"; 

"John Bezdek" 

Subject: [EXTERNAL] Bug Flows Webinar - March 30, 2022 

Date: Tuesday, April 5, 2022 12:01:25 AM 

 This email has been received from outside of DOI - Use caution before clicking on 

links, opening attachments, or responding. 

CREDA is in receipt of the March 10, 2022, notification to the Parties of the 2017 Programmatic 

Agreement that bug flows are again being considered for summer, 2022. We appreciate 

Reclamation’s hosting the March 30, 2022, AMWG stakeholder webinar on the same subject. 

Having reviewed and discussed the information provided on the webinar and the accompanying 

powerpoint presentation, as well as reviewing comments submitted in October 2021, following is 

CREDA’s response to the webinar’s request for input.

 Referring to CREDA’s comments on the LTEMP DEIS and FEIS, CREDA has consistently urged “that 

experiments must include a description of the proposed experiment, the time or frequency of 

implementation of the experiment, and the triggers or other conditions that must exist prior to 

implementation of the experiment. Each experiment must also include a description of the 

hypotheses that will be tested by the experiment and benchmarks or other identifiable criteria that 

will allow the Secretary and interested parties to assess the success or lack thereof, when an 

experiment or action must be terminated because of unacceptable impacts (as specifically 

defined)..” It does not appear that these parameters are fully fleshed out for an experiment 

proposed to begin less than a month from now.

 CREDA recommends that given the significant annual and monthly uncertainties at this point 

(identified on slide 19), and in support of the comment made on the webinar regarding the Flow Ad 

Hoc Group (FLAHG), that the FLAHG be convened/charged with reviewing and considering the 

science design/hydrograph narrative descriptions identified in slide 15; “new” information contained 

on slides 10-11; and refine and define the hypotheses, research and monitoring to be included in a 

potential future bug flow experiment. This process was supported by the AMWG/TWG stakeholders 

and enabled successful planning, implementation and monitoring the 2021 Spring Disturbance flow. 

CREDA requests that the Technical Team and Implementation Team give serious consideration to 

these comments and concerns. Please don’t hesitate to contact me if additional information is 

required. 

Leslie James 

Executive Director 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

From: Jim Strogen 

To: Traynham, Lee E; Fullard, Clarence D; Kennedy, Theodore 

Cc: Bill Persons TU; Tallman, Gary; Rod Buchanan; John and Carol Jordan; JOHN HAMILL; Jim Strogen 

Subject: [EXTERNAL] Bug Flows Comments from Jim Strogen, AMWG Recreational Fishing Representative 

Date: Wednesday, April 6, 2022 4:09:19 PM 

 This email has been received from outside of DOI - Use caution before clicking on 

links, opening attachments, or responding. 

Lee, Clarence and Ted,

 I appreciated the webinar to update all of us on Bug Flows. 

 I again want to express support for these experimental flows and feel that they are very 

helpful to the productivity of the river and benefit trout, native fish, and the many birds and 

animals that may benefit from extra "bugs" in, on, and above the water. 

I know that some members of the AMWG and TWG have concerns that in some regards 

there is not conclusive evidence that the bug flows are accomplishing what they 

potentially might. From my perspective, there are variables like turbidity, temperature, 

and nutrients that make it hard to get a clear picture of how much the bug flows are directly 

responsible for the additional productivity of the river. 

Rather than abandon the experiment I believe it is important to continue them, and look for 

ways to clarify the data. I appreciate the emphasis on the impact to native fish that is being 

considered for example. 

The intuitive nature of these experiments to improve the productivity of the river to me 

means that given the adverse effects of the dam on the river in so many ways, we must engage 

in actions that will try to counter those negative impacts whenever we have an opportunity. 

 The science review comment about the seeming discrepancy of bugs produced and them 

not showing up in traps or drift, and the possibility that they might be in the stomach of trout, 

native fish, birds, and bats is a critical question for further study. I think the native fish study 

aspect will be important information and it would seem that the trout data from the previous 

angler catch trips would help with that question, but may need a larger sampling size to 

provide more certainty. 

The issue of cost for the Bug Flow experiments has seemed to increase as a factor of 

concern with changing hydroelectric rate structures and the critical flows in our future from 

the dam. While it might not be ideal from a data collection perspective, if shifting the timing 

allows for future studies due to lessening the costs due to impact on energy delivery/water 

flow issues, then I would suggest considering ways to shift the timeline that would still 

provide you useful data to help answer questions that you would like to become clearer about. 

 While I would personally like to see bug flows continue due to their likely value to the 

system, I understand that cost issues may prohibit that, and like all of the experiments in the 

TWP process, I believe that most require a defined endpoint when it is clear that no 

appreciable additional information will be gained and the money can be better spent on some 

other valuable experiment. To that end, I think it is important to clarify the number of years 

that you think this experiment should continue, and what you hope to gain by X number of 

years more of this study. You might include a summary that describes the benefit of one , two, 
 

 

 

 

 

 

 

 

 

 

three, or five more years, and what you would gain from those data set points for example. 

I think the likely temperature increases, and lower overall flows will impact the bug life. 

Studying those impacts from the perspective of the bug flow experiments may be important 

for us to further understand the impact on the changing conditions on the river system. 

One last note/question: Was there any way to incorporate the dam repair flows into the bug 

flow findings? Or the constant flow for the overflights into the bug flow findings given the 

extended low flows for both events?

 Thank you. 

Jim Strogen, Recreational Fishing AMWG Representative