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GCMRC's Proposed Experimental Flow Options for the Colorado River

Ecosystem in Water Year 2005 and Beyond

[for Consideration and Discussion by the Glen Canyon Dam Technical Work Group]

May 3, 2004 IINTRODUCTION

In December 2002, U.S. Secretary of Interior Norton approved an adaptive management experiment to

be conducted in Grand Canyon National Park. This experiment, recommended by the Glen Canyon Dam

Adaptive Management Program (AMP) and the Grand Canyon Monitoring and Research Center (GCMRC),

began in January 2003 and consists of elements designed to provide a better and more integrated understanding

of both sediment and fisheriesresources. The GCMRC originally proposed a five-treatment experimental design

that encompassed 16 years of experimentation (Table 1). The AMP recommended and Secretary Norton

approved the first 2 years of this experimental design, and determined that the GCMRC and the AMP's

Technical Work Group (TWG) would determine subsequent annual treatments towards attaining an effective

long-term experimental design. Recent review of the original experimental design by the AMP's Science

Advisors suggested that the design was perhaps unduly complicated and would benefit from some level of

simplification. Therefore, GCMRCis responding to these suggestions by providing a simplified design contained

in this document to form a foundation for discussions and experimental design planning with the TWG during

theirMay3-4,2004meetingandbeyond. .

LONG TERM EXPERIMENTAL DESIGN

Fisheries

A number of factors are speculated to be responsible for the recent decadal decline in the survivorship

and recruitment of the humpbackchub population below Glen Canyon Dam. These factors include: 1) Colorado

and Little Colorado River hydrology, 2) infestation of juvenile HBC by Asian tapeworm, 3) predation by or

competition with warm-waternative cyprinids and catastomids and non-native cyprinids and ictalurids within the

Little Colorado River, 4) predationby or competition with cold-water non-native salmonids within the Colorado

River mainstem, 5) near shore-line habitat alteration that includes back-waters, and 6) reduced growth rates

associated with colder temperatures. Of the total number of factors identified, only a few can be effectively

controlled for in a large-scaleexperimental manipulation.For this reason the scope of this experiment is focused

on treatments applied in the ColoradoRiver mainstem to address two prevailing hypotheses regarded as possible

causal mechanisms responsible for the recent decadal decline in the survivorship and recruitment of the

humpback:

1) predation/competitionis contributing to the decline of humpback chub,

and

2) change in physicalhabitat (flows and temperature)is contributing to the decline of humpback chub.

These two factors are identifiedas affecting humpback chub in the U.S. Fish and Wildlife Services' biological

opinion.

Fine Sediment

The fundamental sediment experiment is considered event driven based on uncontrolled hydrological

factors that influence tributary sediment supply from the Paria River and export of such inputs relative to

monthly release volumesfrom the dam. The underling strategy is to deposit available sediment at high elevations

with a short-term high discharge under sediment enriched conditions. Because of current regulatory restrictions,

this high discharge event can occur only during the months of January - July. However, sediment enriched

conditions following Paria River inputs typically occur August - October. Therefore, the original experimental

design contained operational elements to conserve fall sediment inputs until a January Beach Habitat Building

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Flow (BHBF) could occur. Two different strategies have been identified to conserve sediment input during fall:

1) low stable flows that minimize sediment transport (sand conservation), and 2) short-duration, power-plant

capacity releases immediately following Faria River inputs that are intended to load eddies with new sand under

non-steady flows prior to a controlled flood greater than power plant capacity during the following January.

Both of these tests (Scenarios #1 & 2) focus on the question of whether or not a solely operational strategy exists

for restoring and maintaining sand habitats within the critical upper one-third of the Colorado River ecosystem?

An additional strategy (Scenario #3) recommended by USGS sediment scientists consists of releasing a

controlled flood greater than power plant capacity immediately following sand inputs from the Faria River.

Under the currently approved design, a test of this strategy can only occur if such tributary floods occur during

January throughJune.

Modified Blocked Experimental Design

Following development of the initial long-term experimental design, concerns were raised regarding

confounding effects associated with the degree of complexity of testing multiple factors, as well as effects from

uncontrolled factors. In an attempt to achieve greater simplicity in the design, the GCMRC staff proposes

decoupling the fisheries portion of the integrated experiment from the sediment experiment while maintaining

key element of the original 16-year blocked design (Table 2) including 2-fixed treatment effects and 2-random

treatment effects (described below). The scheduled arrangement of the individual treatments allows for an

analytical method to determine the effects of each factor alone or in combination with other factors on humpback

chub recruitment and sediment response.

PROPOSED EXPERIMENTAL TREATMENTS

Flow Treatment, Fixed Effect (Jan - Mar, Aug - Dec)

The GCMRC recommends that the flow treatment consist of two alternating flow regimes 1) high

fluctuating flows, and 2) stable flows. These flow patterns are scheduled to occur in two-year alternating blocks,

and are to be applied consistently over the duration of the 16-year experimental period.

The fluctuating flow regime is similar to the operational constraints that are identified for the High

Fluctuating Flow (HFF) alternative in the EIS for operations of Glen Canyon Dam (BaR 1995). The GCMRC

recommends that the TWG consider, as an alternative to the original design, that fluctuating flows occur

seasonally during winter and early spring (January through April), followed again during the late summer and

fall (August through December). Under this approach, daily and hourly operations would maximize the range in

flow release (constrained only by annual forecasts and water deliveries), ramp rates for the ascending release are

to be unrestricted, and the descending release is to range between 4,000 to 5,000 cfs. The daily maximum

release would not to exceed 31,000 cfs, and the minimum release would not go below 5,000 cfs.

The stable flow regime would consist of a constant flow release based on monthly projected volumes.

The GCMRC recommends high, stable flows during winter-early spring, and low, stable flows during the late

summer-fall season. As Upper Basin hydrology will allow, the late summer-fall (August through December) is

to remain at a low constant level of 8,000 cfs (:t 1,000 cfs). This provides stability in near shoreline and

backwater habitat and conditions for sediment conservation if tributary sand inputs occur. During the application

of this stable treatment, differences in projected monthly flow volumes (low or high water years) are to be backcalculated and offset in preceding winter-early spring releases. A constraint to flow stability is to be maintained

within but not among months during the winter-early spring period.

The GCMRC proposes that the summer operations (May through July) remain consistent through all

treatments during both fluctuating and stable flow effects. Flow patterns are to follow existing flow guidelines

identified in the Modified Low Fluctuating Flow alternative (MLFF) (BaR 1995). The overall flow treatment

among all years providesfor a combination of maximum load following during the application of the fluctuating

treatment. Combinations of fluctuating and stable flows provide a means to determine how physical habitat

influences reproduction and young-fish survivorship for both native and non-native fishes. Additionally,

recreational use is not hampered during most of the summer period owing to MLFF being implemented

consistentlyas a control.

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Mechanical Removal Treatment, Fixed Effect (Jan - Mar & Jul- Sept)

The ongoing mechanicalremoval of non-native fish program will continue in 4 year blocks as originally

proposed (Coggins et al 2002, Coggins and Yard in Review). This experimental manipulation has been

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implemented in an attempt to better understand interactions between native and non-native fishes (see hypothesis

above), particularly non-native coldwater salmonids and the FederalIy endangered humpback chub.

Temperature Treatment, Random Effect

As originalIy designed by the GCMRC in 2002, the temperature treatment was scheduled as two 8-year

blocks. The thermal regime in the first 8-years was to have remained at normal conditions that represented cold,

seasonalIy constant temperaturesthat were typical of this system. The latter block was to consist of temperatures

that were seasonalIy warmed over the remaining portion of the experiment. This scheduled time lag for applying

treatment effects alIowed for development of the appropriate temperature control device (TCD) design,

environmental compliance, construction, instalIation, and implementation.Currently, it remains uncertain when

the entire TCD will be fulIy operational.

This is important because the effect of each treatment on the response of the experimental unit must be

approximately the same from block to block. The consistency in treatment effect among blocks requires

recognition and commitment by managers to avoid inconsistencies in the application of treatment effects

throughout a long-term experiment. A departure from this invariably makesit more difficult to detect differences

or to be able to separate out treatmenteffects among alternate treatments.

Unfortunately, in an ecologicalsetting certain treatment effects are not entirely uncontrolIable. This has

been problematic owing to unexpected temperature increases in the Colorado River mainstem due to recent

drought conditions, reduced inflows, and changes in the reservoir elevation. AdditionalIy, the construction and

initial testing of the TCD is currently recommended by the AMP Science Advisors to be incrementalIy scheduled

and phased in over multiple years in the near future. For this reason, the TCD treatment should be considered

more as a random variable in the first 8-years as an incremental titration.

Beach Habitat Building Flow, Random Effect (January)

Owing to the fact that there is no certainty as to which years the Colorado River ecosystem will be

subject to sand inputs from the Paria River, it is impossible to implement the sand conservation tests under

anything but a random fashion. While several key hypotheses remain to be tested with respect to sand bar

restoration and maintenance, there is substantialIy less need for replication of the proposed treatments than exists

for the fishery related treatments. The basic question to be answered regarding sand-based habitats is whether or

not the desired objectives can be achieved under the highly limited sand supply conditions that exist below the

dam.

DISCUSSION

Although relevant sand-based issues may be mostly addressed within one to three flow-based scenarios,

conducting a large scale-manipulationis hampered by two recurring problems: a lack of complete independence

among the biological experimental units (e.g. recruitment response) to treatment effects, and a lack of a control.

Relative to humpback chub recruitment,lack of independence is confounded by variability in growth among ageclasses such that actual age must be estimated from pooled length-age relationships. There is then variability in

the annual recruitment response because a particular age-class may be partialIy assigned to incorrect cohorts.

Lastly, there is no secondary river system that can be used as an effective independent control to assess

recruitment responses under reference conditionsin absence of applied treatments.

The blocked design provides a means to experimentalIy test multiple hypotheses using large-scale and

long-term manipulations of the Colorado River mainstem.This is always problematic in an ecological setting

because certain environmental factors are not entirely controlIable (i.e., inter-annual differences in hydrology,

sediment supply, and temperature in the mainstem). For this design to be effective, treatment factors must be

applied consistently among and within scheduled blocks. This is important because the effect of each treatment

on the response of the experimental unit must be approximately the same from block to block. Therefore,

consistency in treatment effect among blocks requires recognition and commitment by managers to avoid

inconsistencies in the application (time and intensity) of treatment throughout a long-term experiment. A

departure from this implementationapproach invariably makesit moredifficult to detect differences or to be able

to separate out treatment effects amongother alternate treatments.

The proposed design elements address both sediment and fisheries resources. However, because the

sediment treatments are event driven relative to enriched conditions folIowing a tributary input and the

treatments relative to fisheries folIow a more structured design, the revised design outlined here decouples these

treatments to some degree. The intersection of the fisheries and sediment experiments is during the falI when the

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fisheries treatment may call for either stabilized flows or fluctuating flows depending on the year. During this

same time period, the system may either be in an enriched sediment condition following significant Faria River

input, or in a reduced sediment condition assuming no inputs.If sediment inputs occur during a scheduled stable

flow year, sediment Scenario #1 (see above) would be pursued.Alternately, Scenario #2 would be pursued under

enriched conditions during a scheduled fluctuating flow year. Scenario #3 would continue to be an option for

testing in any year in which Faria River sand inputs meet or exceed the required triggering thresholds in the

January through July timeframe.

II

ILITERA TURE CITED

Coggins, LG., M.D. Yard, and C. Paukert. 2002. Piscivoryby non-native salmonids in the Colorado River and

an evaluation of the efficacy of mechanical removal of non-native salmonids. USGS, Grand Canyon

Monitoring and Research Center, Flagstaff, AZ.

Coggins, LG., and M.D. Yard. In Review. Mechanical removal of non-native fishes in the Colorado River in

Grand Canyon: Update of winter 2003 operationsand findings. Grand Canyon Monitoring and Research

Center. Flagstaff, Arizona. 69 pp.

U.S. Bureau of Reclamation. 1995. Operations of GlenCanyon Dam Colorado River Storage Project Act. Final

Environmental Impact Statement. Department of the Interior, March 1995. 337 pp.

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Table 1. Original experimental design with 4 fixed factors and I random factor (Beach Habitat Building Flow).

IMPLEMENT TREA TMENT DO NOT IMPLEMENT TREATMENT

Water Year

WY2002-03

WY2003-04

WY2004-05

WY2005-06

WY2006-07

WY2007-08

WY2008-09

WY2009-10

WY2010-11

WY2011-12

WY2012-13

WY2013-14

WY2014-15

WY2015-16

WY2016-17

WY2017-18

Increased

Fluctuations

In Daily Flows

(Jan - Mar)

Mechanical

Removal of Rainbow

Trout in GC

(Jan-Mar, Jul - Dec)

Stable-Low

Flows in Fall

Temperature

Control

Device

(Future)

Beach Habitat

Building Flow

Table 2. Proposed modified experimental design with two fixed factors (Flow Treatment and Mechanical

Removal) and two random factors (TCD/Low Reservoir Releases and Beach Habitat Building Flow).

Water Year

WY2002-03

WY2003-04

WY2004-05

WY2005-06

WY2006-07

WY2007-08

WY2008-09

WY2009-10

WY2010-11

WY2011-12

WY2012-13

WY2013-14

WY2014-15

WY2015-16

WY2016-17

WY2017-18

DRAFT

Flow

Treatment

(Jan -Apr,

Aug- Dec)

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Temperature Beach

Control Habitat

Device/Low Building

Reservoir Releases Flow

(Jan -Jul)

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven

Random Event Driven