1

Proposal for Experimental Fund Support

Mike Yard, USGS GCMRC, and Josh Korman, Ecometric.

Development of an Information Base to Implement Trout Management Flows

1.0 Introduction

Trout Management Flows (TMFs) are an experimental element identified in the Glen Canyon 

Dam Long-Term Experimental and Management Plan (LTEMP) Environmental Impact 

Statement (EIS). These flows are intended to reduce the probability of large recruitment events

of young rainbow trout in Glen Canyon. High levels of recruitment have been shown to lead to 

poor growth and population collapse which has negative effects on the trout fishery in Glen 

Canyon. High levels of recruitment in Glen Canyon can also increase the number of trout that 

disperse into Marble Canyon and lead to higher trout abundance at the Little Colorado River and

have negative effects on humpback chub. 

TMFs will be timed to coincide with the emergence of rainbow trout in Glen Canyon, which 

peaks between May, June, and July. Newly emerged trout are small and fragile and are limited to 

very shallow and low velocity areas in immediate shoreline areas. The premise of TMFs is that 

newly emerged fish will move into microhabitats newly inundated by the peak TMF flow, and 

that these fish will be stranded when the flows are rapidly reduced. 

The conceptual model from the final LTEMP EIS does not recognize the many variables and

uncertainty related to the characteristics that would comprise a successful TMF. Variables that 

we believe important to consider when designing a TMF include:

1. The maximum discharge at the peak of the TMF cycle, which relates directly to the area 

and amount of inundation. This discharge would depend on the distribution and elevation 

of floodplain habitats and other characteristics such as substrate, distance to the main 

channel, slope, and vegetation cover.

2. The length of time needed for young fish to colonize newly wetted areas inundated at the 

maximum peak of the TMF cycle (a key uncertainty).

3. The rate at which flows should be reduced to the minimum of the TMF cycle.

4. The minimum flow level at the end of the recession and the duration of the low flow 

period (which may be lower than the normal minimum flow in the month it is 

implemented).

5. The hydropower cost of a range of TMF flows and their potential impact on beaches, fine 

sediment storage, and water levels in Grand Canyon in areas used by native fish.

Due to the recent increase in brown trout in Glen Canyon, interest has been expressed in using 

TMFs to limit their recruitment. The characteristics of TMFs focused on brown trout will likely 

be similar to those for rainbow trout with the exception that they will likely need to be conducted 

earlier in the year to coincide with the period of brown trout emergence (February-April), which 
2

is prior to the May-August TMF window for rainbow trout allowed under the LTEMP Record of 

Decision. Verification is warranted for both the timing of brown trout emergence and the 

similarity of their habitat requirements relative to rainbow trout.

2.0 Workplan

This proposal summarizes work elements that will provide critical information on characteristics 

of TMFs in order to optimize their effectiveness at reducing recruitment while minimizing 

negative side-effects. TMFs could have negative effects on important LTEMP resources 

including native fish, beaches, and hydropower. It is therefore critical to do as much preliminary

work on these flows as possible so that the first potential implementation of a TMF is successful 

and does not cause unintended harm. The work elements will be conducted in FY2019-20, 

ideally prior to the first TMF. It is proposed that the work described below will be supported 

under the Experimental Fund in the Glen Canyon Dam Adaptive Management Program’s 

FY2018-20 Triennial Work Plan (FY18-20 TWP). The work elements are:

1. A literature review of micro-habitat requirements of recently emerged rainbow trout and 

brown trout. This review will establish the ideal depth, velocity, and substrate

characteristics for each species (rainbow trout and brown trout) that will be targeted at 

the peak of the TMF cycle. This information will be used in element 2 below, to identify 

discharges that provide the optimal habitat and attracts as many recently emerged trout 

into flood plain habitats as possible during the peak flows of any TMF. Extensive 

literature indicates that the rate of stranding and mortality depends on the downramp 

rate, time of day (day or night), water temperature, and fish size. It is likely that other 

factors such as substrate type, shoreline complexity, and shoreline angle also play a role. 

This work element will review the available literature for guidance on the timing and 

flow rate of ascension and recession for a TMF and guidance for mesocosm experiments 

described below.

2. An analysis of Glen Canyon bathymetry, stage-discharge relationships, and 2D hydraulic 

model predictions of depth and velocity (based on recent modelling of S. Wright, 

USGS). This analysis will identify the discharge levels that maximize the area of lowangle shoreline inundated at the peak TMF flow. Information from the literature review 

(element 1) will be used to refine these calculations. Higher discharges (e.g., 20,000-

25,000 ft3/s) may provide greater areas of inundation and therefore result in higher rates 

of stranding. However, these discharge levels may result in greater hydropower losses 

and increase erosion of beaches. Thus, it is critical to quantify the relationship between 

discharge and the area of floodplain inundation so that managers can evaluate potential 

trade-offs between maximizing the effectiveness of TMFs and minimizing negative side 

effects.
3

3. Mesocosm experiments will be used as a low cost and low risk means of defining TMF 

characteristics such as the rate of ascension, the duration of the peak flow period required 

for colonization of inundated flood plain habitat by small trout, and the rate and timing 

(day vs. night) of the recession. Mesocosms will be constructed at a source of water 

adjacent to the National Park Service facility at Lees Ferry (behind the 14-day parking 

lot). Recently emerged rainbow trout will be collected in Glen Canyon in June and July 

to seed the mesocosms. These experiments will be used to define the length of time 

necessary to maintain the peak flow, colonize newly wetted areas, and to provide details 

on recession (rate of downramp, day vs. night, effectiveness on fish of different sizes, 

etc.). 

4. A small-scale field experiment will be conducted to measure the rate of colonization as 

flows are increased, and to develop and test field techniques to determine the extent of 

colonization. This experiment will be conducted at a single location with a low angle 

cobble bar that is flooded over the range of flows (likely prop bar at RM -11). It will be 

timed to coincide with the normal June-July volume increases, with possible 

modification to maximize its utility. Minimum flows typically increase from ~ 7,000-

10,000 ft3/s between June and July. Ideally the minimum flow during July could be 

increased to 15,000 ft

3

/s or even 18,000 ft3/s for 1-5 days. Shoreline, nighttime, backpack 

electrofishing will capture recently emerged rainbow trout during low flows of 5,000-

8,000 ft3/s. These small fish will be marked using alternate marking techniques (visual 

implant elastomer (VIE), clipping, batch dying). Flows will be increased to levels of 

approximately 15,000 ft3/ after marking and a second electrofishing event will recapture 

marked fish to determine the rate and extent of colonization of recently inundated areas.

5. Addition of a single Trout Recruitment Growth Dynamics (TRGD) trip in July. The 

TRGD project funded in the FY18-20 TWP has trips scheduled for April, September, 

October, and January (4 trips/yr.). The October trip is used to reliably quantify annual 

recruitment using mark-recapture (most of the annual cohort are >=75 mm at that time).

The September, October, and January trips quantify growth rates before and after High 

Flow Experiments (HFE). The April and September trips characterize the combined 

spring-summer growth rates. The proposed July trip will be critical to quantifying TMFrelated mortality. TMFs will potentially result in high mortality during the summer. 

Differences in abundance between the additional July trip and the currently funded 

September trips will quantify TMF-related mortality. However, it is important to collect 

this information in years when TMFs are not conducted to provide a baseline to compare 

with years when they are implemented. This baseline is available in 2012-2017, and the 

proposed addition of a July trip would provide an extended baseline through 2020. 

September and October trips will determine if TMF-related losses are compensated by 

higher survival rates due to lower densities following the TMF (the rate of change in 
4

abundance between July, September, and October trips will allow us to evaluate this 

potential compensation). The TRGD projects mark trout with passive integrated 

transponder (PIT) tags down to a minimum size of 75 mm. Large numbers of smaller 

trout are captured and enumerated during July and September trips; however, these fish 

will be too small to tag. Previously they have been marked with fin clips to provide 

estimates of abundance. To date these data have not been analyzed or integrated into 

existing mark-recapture models. This work element therefore also requires funding to

analyze data and integrate it into the existing mark-recapture model. This model will 

provide a quantitative tool for evaluating the population-level effect of TMFs.

6. Economic and sediment loss evaluations and flow routing for a variety of TMFs will be 

conducted by GCMRC, Western Area Power Administration (WAPA), Reclamation, and 

cooperators using models developed for the LTEMP EIS. Unsteady flow modelling will 

be used to evaluate the extent to which the low flow component of the TMF is attenuated 

at increasing distance from Glen Canyon Dam. This will help define the maximum low 

flow period that can be implemented without having that low flow reach the Little 

Colorado River confluence. The recently updated suspended sediment rating curve 

model will be used to evaluate effects of peak TMF flows on sand storage. The WAPA 

planning model used to optimize hourly flows will be used to calculate the hydropower 

cost of TMF experiments.

3.0 Project Timeline

Project element 1 (literature review) will be conducted prior to conducting mesocosm 

experiments and the GIS analysis. Element 2 (bathymetry, stage, etc.) is underway and analysis 

of these data will be continued in FY19. Element 3 (mesocosm experiments) will be conducted 

in June and July of 2019 and 2020. Element 4 (small-scale field experiment) will be conducted in 

July of 2019 or 2020. Element 5 (July TRGD field trips) will be conducted in 2018, 2019, and 

2020. Element 6 (economic, sediment loss, and flow-routing evaluations) will be conducted in 

2018 and 2019. 

Information from this project will provide sufficient resources to adequately define 

characteristics and evaluate the first potential implementation of a TMF in 2021. It will also 

inform the development of the FY21-23 Triennial Work Plan. If a spring HFE is implemented in 

2020 (the first year allowed under the LTEMP EIS) and a large trout recruitment event results,

information gained from this project prior to that date would be useful if it were deemed 

necessary to conduct a TMF to manage trout recruitment. Implementation of a TMF in summer 

of 2021 would be preferred, however, since it would allow for an additional year of data 

collection and synthesis leading to a more sound design.
5

4.0 Project Budget

The estimated cost for the proposed work is approximately $120,000 in FY2019 and $130,000 in 

FY2020. Specific details on cost for model development, analyses, logistics, labor and 

expenditures for field work and experimental mesocosms are provided in Table 1. The biological 

science technicians that will work on this project have not been identified yet. We intend on 

hiring qualified biological science technicians using an interim 180-day hire (GS 5-7), or 

alternatively, reallocating some of this funding to existing staff for conducting the mesocosm 

experiments at Lees Ferry.
6

Table 1. Trout Management Flow Experiment budget.

Component 1. Literature compilation and review of trout micro-habitat requirements 

No cost - Covered by existing GCMRC staff

Component 2. Analysis of spatial and hydraulic data 

No cost - Covered by existing GCMRC staff

Component 3. Mesocosm experiments

2019 2020

Supplies & Materials $ 1,000 $ 1,000

Technician Salaries $ 21,117 $ 21,751

Travel $ 14,280 $ 14,280

Overhead $ 5,511.35 $ 9,367.99

SubTotal $ 41,908.56 $ 46,398.72

Component 4. Small-scale field experiments (GCMRC Staff)

2019 2020

Supplies & Materials $ 1,000 $ 1,000

Technician Salaries $ - $ -

Travel $ 1,830 $ 1,830

Overhead $ 989 $ 1,678

SubTotal $ 3,819 $ 4,508

Component 5. - Trout Recruitment Growth Dynamics (TRGD).

5.A - Annual July 7-day Trip

2019 2020

Supplies & Materials $ 5,562 $ 5,729

Logistics $ 28,018 $ 28,859

Technician Salaries $ 8,651 $ 8,910

Overhead $ 5,709.36 $ 9,819.95

Ecometric $ 9,000.00 $ 9,000.00

SubTotal $ 56,940 $ 62,318

5.B - Integration of batch marks into existing mark-recapture models

2019 2020

Ecometric $ 13,000 $ 13,000

Component 6. Economic and sediment loss evaluations and flow routing

No cost - Covered by existing GCMRC, BOR, and WAPA staff

2019 2020

TOTAL COST $ 119,486 $ 130,733 $250,219.34

Overhead rate: FY19 = 0.1557, FY20 = 0.26