1

-UpdateExperimental Flow Options 

for the 

Technical Work Group 

Grand Canyon Monitoring and Research Center 

January 20, 2006 

Introduction: 

Agreement on an experimental flow regime or operation of Glen Canyon Dam (GCD) is 

a fundamental element of the FY 07-FY 11 Monitoring and Research Plan (MRP). 

Following is a preliminary description and evaluation of three experimental flow options 

for consideration by the Science Planning Group. Option 1 and 2 were developed 

primarily by GCMRC; Option 3 reflects a proposal presented by WAPA, ADFG, and 

FFF at the November 2005 TWG meeting (as amended); Option 4 reflects a proposal by 

the Grand Canyon Trust to implement a modified version of a 2000 proposal by Rich 

Valdez et al which provides for extended periods of steady flows. 

These options are provided to facilitate a productive evaluation of alternative GCD 

operations by the SPG (and TWG). The options are not meant to be exhaustive and SPG 

may ultimately develop and evaluate additional options beyond those presented below 

e.g., combine the best elements of different options or consider an entirely new option. 

It is anticipated that each of the experimental flow regimes would be implemented in 

conjunction with some or all of the following “non flow” treatments or actions: 

• Implementation of a selective withdrawal structure on Glen Canyon Dam (GCD) 

to enhance water temperature and other water quality parameters in the Colorado 

River below GCD 

• Implementation of the some or all elements of HBC Comprehensive Plan (refugia, 

translocation, etc) 

• Implementation of mechanical removal of non native fishes that compete with or 

prey upon native fishes 

The SPG reviewed and discussed these options at its January 9-10, 2006 meeting. The 

SPG agreed on a process and schedule to better define the scope, objectives and timing of 

these experimental options (Attachment 1). The SPG also agreed to select the preferred 

option at its meeting on Feb 22-23, 2006. 

Option 1 – Continue Baseline Monitoring of Modified Low-Fluctuating Flow Operation 

Under the 1996 Record of Decision w/Testing of Beach Habitat Building Flows (BHBF) 

and winter ramping rate studies 

1) Flow Regime– the daily operation of Glen Canyon Dam is continued under the 

operating rules defined in the Record-of-Decision during all months as determined by 

projected annual hydrology. Stable flows would not occur within any month of the 

water year, except for the purpose of flying remote sensing missions before and 

following BHBF tests. 
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• Daily ranges in flow are 4,000, 5,000 or 8,000, while the hourly ramping rates are 

4,000 cfs/hr up and 1,500 cfs/hr down. 

• Flows below 8,000 cfs are only allowed between 1900 and 0700 each day. 

• Down-ramping rate studies would occur in the months of December through 

March, whereby a range of changes in down-ramping rates would be evaluated 

with respect to sandbar habitat stability. 

• BHBF tests would be conducted to determine the most effective operation for 

conserving sediment and creating and maintaining sandbars and associated 

backwater habitats. BHBF tests would occur following tributary sand enrichment 

and some period of MLFF operations to distribute sand throughout critical 

downstream reaches. The duration of BHBF would be 2-days or perhaps even 

shorter. 

• Studies would be conducted to determine whether or not implementation of the 

BHBF and alternative winter or spring diurnal fluctuations affect (a) the 

formation, and persistence of sandbars (b) the abundance and distribution of nearshore backwater habitats, and (b) the use of the use of backwaters by humpback 

chub during subsequent summer and fall months. 

2) Pros – 

• Provides continuity with baseline data on similar operations that have occurred 

consistently in spring, summer and fall months since 1991, with respect to 

fisheries and sand conservation studies, while major treatments (river warming 

and mechanical removal) are implemented (both started in WY 2003 and continue 

at present). 

• Will determine whether and under what conditions BHBF’s can be more 

effectively used to achieve desired restoration and maintenance of sandbars and 

related habitats. 

• Assesses humpback chub recruitment under MLFF, a prolonged period of exotic 

fish control, and naturally occurring warmer river temperatures; (warming that 

approximates what might occur under future operation of a Selective Withdrawal 

Structure). 

• Defers the high costs associated with stable flow tests with the expectation that 

benefits to native fishes and other resources can be achieved without such costly 

or controversial treatments being implemented. 

3) Cons – 

• If non-steady habitat conditions are the key factor limiting chub recruitment, then 

this option will delay the desired biological benefits to endangered fish and 

delayed learning about that fact. (The importance of habitat stability vs. influence 

of warmer water in chub recruitment was clearly identified as a fundamental 

uncertainty in the recent Knowledge Assessment workshops). 

• Reduced power generation that meets customer demands (as compared to Option 3). 
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Option 2 – “Baseline Monitoring of Modified Low-Fluctuating Flow Operation Under 

1996 Record of Decision w/BHBF Testing + Winter ramping rate studies + Stable Flow 

Operations in September & October” 

1) Flow Regime . The same as Option 1 except that stable flows would be implemented 

and tested in September and October. The level of stable flow depends on annual 

hydrology and may vary through the course of the experimental period, 2007-2011.

2) Pros – 

• Same as Option 1 

• Stable flows in the fall may result in stable habitat conditions that enhance 

recruitment of YOY native fishes (HBC) 

3) Cons – 

• Reduced power production to meet customer demands and the higher power 

replacement costs 

• Experimental results are potentially confounded by having three major flow and 

non-flow treatments implemented simultaneously. If the desired fisheries 

response does occur under this suite of treatments, it is not possible to determine 

which of the three treatments provides the most or least significant role in the 

response. Learning is limited compared with Option 1. 

Option 3 – WAPA/AFGD/FFF “Experimental Modification of the Record-of-Decision 

Modified Low-Fluctuation Flow” 

1) Flow Regime The daily operation of Glen Canyon Dam is under a hybrid of 

fluctuating operations that closely approximates MLFF 

• Down ramp rates are increase for seven months, increased daily range [10,000 to 

12,000 cfs] increased down ramp rate [3,000 cfs/hr]) for five months. 

• Up ramp appears to be identical ROD in all twelve months. 

• In five of the twelve months, the daily minimum flow is lower by approximately 

5,000 cfs in winter [December through February] and 3,000 cfs in summer [July 

& August]. 

• In every month, this option includes one to three additional “on-peak” hours, but 

the peaks appear to be essentially identical to those that would occur under the 

strict MLFF, as described in Option 1. 

• It is unclear from the current proposal whether BHBF tests would be conducted 

under this option and if so under what terms and conditions. 

• Its unclear whether this option includes studies to determine the affects of the 

proposed operation on (a) the formation, and persistence of sandbars (b) the 

abundance and distribution of near-shore backwater habitats, and (b) the use of 

the use of backwaters by humpback chub during subsequent summer and fall 

months. 

2) Pros – 

• Increased generation of hydropower during winter and summer months by the 

better aligning dam operations with daily customer power demands. 
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• Presumed increase aquatic food and drift which may benefit both the trout fishery 

and native fish. 

• Increased summer flows would inhibit successful trout reproduction which may 

benefit native fishes 

• Although not identical to MLFF operations, there is still an emphasis on 

continuity with limited fluctuating-flow baseline data for similar operations that 

have occurred consistently in spring, summer and fall months since 1991, with 

respect to fisheries and sand conservation studies. 

• Biological response studies could continue to focus on the potential for successful 

humpback chub recruitment under MLFF, a prolonged period of exotic fish 

species control, and naturally occurring warmer river temperatures that 

approximate what might occur under operation of a Selective Withdrawal 

Structure. 

• The high costs associated with stable flows are also still deferred for some time, 

with hope that the desired biological benefits to native can be achieved without 

such a costly or controversial treatment being implemented. 

3) Cons 

• The fluctuating-flow operations are not identical to those for which 15 years of 

baseline data have been collected with respect to fisheries and sediment resource 

responses. This may be a concern especially for the summer months of July and 

August, where biological responses of fish and the food base are not well 

documented or highly predictable. 

• If non-steady habitat conditions are the key factor limiting chub recruitment, then 

this option will delay the hoped-for biological benefits to endangered fish and 

delayed learning about that fact. (The importance of habitat stability vs. influence 

of warmer water in chub recruitment was clearly identified as a fundamental 

uncertainty in the recent Knowledge Assessment workshops). 

• Potentially greater export of sand although this can not be fully analyzed without 

additional information 

Option 4 – Grand Canyon Trust (GCT) Experimental Modification of the Record-ofDecision Modified Low-Fluctuation Flow 

Flow Regime. The RPA and Valdez et al. report (Valdez et al. 2000) would serve as the 

foundation for designing the experimental flows. However, the Valdez et al. design may 

be modified after considering new information (e.g., LSSF results, research results since 

2000 and the Knowledge Assessment). For example, it would be useful to evaluate 

whether the spike flows recommended in the Valdez design have enough value to the fish 

community to offset the potential negative impact they might have to trout, hydropower 

generation, sediment conservation or other park values. The Valdez et al. (2000) proposal 

consists of: 

• 1 year of MLFF at 8.23 maf (MLFF8.23), as a baseline, followed by 2 years of the 

EF hydrograph at 8.23 maf (EF8.23), as independent treatments. 
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• The EF hydrograph for each treatment extends for 1 year and consists of a high 

steady release of 21,400 cubic feet per second (cfs) from mid-March through May 

with a 4-day spike of 33,000 cfs in late April. 

• This is followed by a low steady release of 8,000 cfs from June through February 

with a 4-day spike of 33,000 cfs in late September. 

• Ramping rates of 4,000 cfs/hr up and 1,500 cfs/hr down are applied to the two 

spike releases. 

• Based on the pattern of dam releases from 1964 to 1998, the probability of a 

release of 8.5 maf, or less, is about 46%, and the probability of consecutive years 

of 8.5 maf, or less, is only about 26%. Hence, consecutive years of approximately 

8.23 maf releases are unlikely to occur, and the study design considers each EF8.23 

as an independent treatment for comparison against the 1-year baseline of 

MLFF8.23, supplemented with data from previous studies. 

• If Glen Canyon Dam is modified to control downstream temperatures before the 

program of experimental flows is implemented, the temperature control device 

must be implemented equally during both the baseline and treatment years. 

• Other experimental releases from Glen Canyon Dam (e.g., beach/habitat building 

flows, test floods) should not be implemented during the 3-year program of EF in 

order to avoid confounding results of the EF. However, if water volume is 

available, the 4-day spike can be allowed to exceed 33,000 cfs. 

 

4) Pros – 

• The major results from implementing the experimental flows are to benefit 

humpback chub and other native fish, and satisfy Element 1A of the RPA. 

5) Cons – 

• Reduced power production to meet customer demands and the higher power 

replacement power costs. 
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SPG Process and Schedule for Evaluating Experimental Options and Designs 

1. GCMRC will further evaluate and describe similarities and differences in the 

proposed experimental options including a new option proposed by Rick Johnson 

for extended periods of steady flows (patterned after Valdez’s 2000 proposal). 

Rick will provide a written description of his option to GCMRC. Rick’s 

expectation is that GCMRC will modify and adjust the proposal based on new 

information. WAPA will provide written description of Opt 3. (GCMRC will 

send an outline to WAPA and Rick Johnson identifying info that should be 

included in the write-up). Impacts of options to all resource categories/AMP 

goals will be evaluated (including an analysis of impacts to habitat required to 

support extirpated species i.e., SWF, RBS, CP, NLF). Expand pros and cons of 

each option. 

2. GCMRC’s will utilize a format that facilitates easy comparison by the SPG 

3. The evaluation will focus on next 5 years but will be put in context of a long term 

(e.g., 10 year) plan or perspective 

4. The evaluation will identify the experimental hybrid design(s) (as defined by 

AMWG) associated with each option and the implications for “learning” and 

resource restoration 

• Management action – a management action is an action that is turned on 

and left on indefinitely and is not formally tested/evaluated (based on 

manager’s review of the KA, other pertinent scientific info, and an 

assessment of the risk of being wrong). For the purposes of this exercise 

the person proposing the option will initially define the “management 

actions” associated with the option. This will be reviewed at the next SPG 

meeting with understanding that a more detailed assessment will occur in 

next planning cycle 

• Id strengths and weaknesses of each design in terms of timeframes 

(duration required for success), financial costs, degree of learning, 

resource risks, etc 

5. The evaluation will include a hydrograph for each option. The hydrograph will 

show monthly volumes, and max and min flows for each month 

6. GCMRC will complete its evaluation by Feb 13 for consideration by the SPG at it 

Feb 21 meeting FOR A DECISION OR RECOMMENDATION TO TWG