REVIEW OF THE “SCIENCE PLAN FOR POTENTIAL 2008 

EXPERIMENTAL HIGH FLOW AT GLEN CANYON DAM” 

BY 

GLEN CANYON DAM ADAPTIVE MANAGEMENT PROGRAM 

SCIENCE ADVISORS 

JILL BARON 

VIRGINIA DALE 

DON FOWLER 

LANCE GUNDERSON 

JAMES KITCHELL 

DALE ROBERTSON 

HAROLD TYUS 

ELLEN WOHL 

AND 

L.D. GARRETT, SA EXECUTIVE DIRECTOR 

JANUARY 13, 2008
REVIEW OF THE “SCIENCE PLAN FOR POTENTIAL 2008 

EXPERIMENTAL HIGH FLOW AT GLEN CANYON DAM” 

BY GCD AMP SCIENCE ADVISORS 

EXECUTIVE SUMMARY 

 The authors provide a convincing argument that high flow events in the CRE can 

mitigate some ongoing adverse effects of Glen Canyon Dam on sediment, and also 

benefit HBC, the aquatic food base, cultural resources, etc. The Plan also clarified goals 

and findings of previous high flow tests (1996/2004), explain how each differed, and 

identified inherent weaknesses and strengths. The summary review explains why 

additional tests are needed, and also what might be learned from this proposed high flow 

experiment. We find the overall plan acceptable for implementation, and provide the 

following input for improvements. 

 More explicit description of what is to be accomplished in this test would benefit 

from additional information. Some questions and comments from the SAs are: 

• To complete the test of contrast to the 2004 test, having more sand distributed 

throughout the system is important. More sand is in the system, but is it 

distributed throughout the system? 

• Impacts to the HBC may be avoided by a lack of movement of yoy out of the 

LCR. However, could winter storm events jeopardize this setting? 

• Benefits to HBC are to be assessed from backwaters. However, it is unclear 

how benefits will be realized from this test in reviewing Table 1.A and the 

text. It seems realistic from current science that backwaters might offer 

beneficial habitat that might be used by chubs, but more information is needed 

to structure and test effective hypotheses in this high flow event. 

• Documented impacts of high flow events on potential food base for RBT or 

HBC do not seem to be known well enough to develop good hypotheses for 

testing. As noted additional information will benefit hypotheses development. 

• Sufficient knowledge seems to exist to test flow and sediment impacts on 

cultural resources. Yet, this is an area which appears to have separate rather 

than collaborate efforts to satisfy resource protection and learning in the AMP. 

2
The science approach outlined does not mention BOR’s efforts on protection, 

and the science approaches presented here are not referenced in the BOR 

effort. 

 The authors have listed the concerns of AMP members in Table 1.A and made 

these more specific in the strategic science questions (SSQ) in Table 1. However, when 

one tries to put all of these together it is not clearly apparent exactly what scientists 

currently know regarding potential expected impacts. It is not clear whether the scientific 

effort on a specific resource should be a test of a fully specified hypothesis, or should it 

be continued research or discovery to gain more knowledge to enable hypothesis testing 

in the future. 

 It would be helpful to clarify for each resource of concern, i.e. food base, HBC, 

cultural resources, vegetation, etc., those hypothesis tests the scientists feel they can fully 

articulate for the 2008 experiment, and what additional knowledge is required to allow 

pertinent hypothesis to be tested in the next high flow experiment. 

 Mention is made of socio-economic tradeoff assessments in the test, i.e. treatment 

of costs and benefits. However, no specific science activity is endorsed for this high flow 

event. The SAs have noted in prior reviews that significant benefits could be obtained for 

the AMP, most specifically the AMWG and TWG, if operable but simplistic Cost Benefit 

Analysis (CBA) models were developed for use in science and management program 

planning. As noted in SA comments, however, development of CBA capabilities for 

AMP managers might best be structured to respond to overall ongoing decision needs of 

the organization. In this regard, they should be designed and incorporated into an annual 

work plan where focus could be attached to the broader need. GCMRC has noted this 

effort is outside the scope of this project. 

 It is true that due to the complexity in determining overall and individual resource 

effects from high flow events, a longer term multi-event assessment is necessary. This 

does, of course, not obviate some interpretations from each event evaluated, such as the 

proposed 2008 event. GCMRC has noted, for example, some of the benefits or findings 

that might occur from the proposed 2008 event. 

 It is postulated that the GCD AMP will continue to complete its effort on the 

LTEP, part of which includes specification of the number and potential frequency of high 

3
flow events. Although the SAs also agree that the AMP will accomplish this task, we 

feel it is likely this activity could be delayed for several years. Should similar conditions 

to 2008 develop in the next 3 year period; will another high flow event be proposed by 

the AMP and GCMRC? If so, design of some of its primary elements should be part of 

the outcome of the 2008 high flow assessments. 

 The AMP must balance its program of learning with its long-term pursuit to 

resolve 12 differing and often conflicting, resource goals that range from sand 

conservation to HBC enhancement to stable electric power generation. In the overall 

program direction, high flow events can contribute opportunity to resolve these multiresource issues. 

 The LTEP selected in the 1996 ROD is the Moderate Low Fluctuating Flow 

(MLFF). It is apparent from AMP collaborative workshop efforts that both managers and 

scientists see potential marginal changes to the MLFF as offering capability over the next 

5 years to enhance overall knowledge about sediment conservation. This issue is raised 

in the plan but not discussed. 

 It seems important to discuss how LTEP options might be best aligned to 

maintain the derived benefit of the high flow experiment. GCMRC should at least 

introduce this issue as a prologue to this plan. In this regard, science seems to point to 

some semblance of increased flow stability after implementation of a high flow event to 

gain greater assurance of conserving the sand that has been moved up and out of the 

channel to sand bars. 

 Extended low stable flows would create opportunity for conservation of sand but 

would also reduce the opportunity to maintain power supplies, one of the important goals 

of the AMP. A more marginal change under current 8.23 constraints would be to pursue 

a variant discussed in the Science Planning Group (SPG) that would establish equal 

monthly volumes and daily flows of lower variability, i.e. 7-13,000 CFS. These 

operations would be a slight modification of the MLLF that might reduce conflicts 

between power and environmental resources, and since they are within the ROD so they 

could be easily implemented. At the minimum, a discussion of the potential tradeoffs to 

this approach would seem a logical step to evaluate sand conservation after the high flow 

event. 

4
REVIEW OF THE “SCIENCE PLAN FOR POTENTIAL 2008 

EXPERIMENTAL HIGH FLOW AT GLEN CANYON DAM” 

BY 

GLEN CANYON DAM ADAPTIVE MANAGEMENT PROGRAM 

SCIENCE ADVISORS 

JILL BARON 

VIRGINIA DALE 

DON FOWLER 

LANCE GUNDERSON 

JAMES KITCHELL 

DALE ROBERTSON 

HAROLD TYUS 

ELLEN WOHL 

AND 

L.D. GARRETT, SA EXECUTIVE DIRECTOR 

INTRODUCTION 

 The Science Advisors (SAs) reviewed the first draft of the current science plan in 

February 2007, and reported on that review to the GCMRC1

, TWG and AMWG. 

General and specific comments were contained in the review. The following general 

comments was provided by the Science Advisors: 

• Presentation of background information from 1996 and 2004 high flow events 

were important. 

• Detailed study information was important. More information on methods was 

requested. The riparian vegetation surveys are insufficiently supported by 

current literature. 

• The Plan was generally well designed with good study linkage. Primary plan 

elements are covered. 

 

1

 GCD AMP Science Advisors. 2007. A review of the Science Plan for Potential 2007 Beach Habitat 

Building Flow Experiment. Final review report on file at GCMRC, USGS, 2/12/07. 13 pages, Appendix. 

5
• Greater documentation of HBC planned and ongoing science activity was 

needed. Some tracking was recommended on habitat change (backwater) and 

HBC. 

• Additional documentation was needed of ongoing planned cultural resource 

programming. 

• Vegetation study should be revised. 

• Expand proposed Lake Powell assessment. 

GCMRC committed to revise the draft plan based on recommendations from the SAs and 

other AMP members. 

 It was originally anticipated that a high flow experiment would be attempted in 

2007, but due to several concerns it was delayed. Since then lower fluctuating flows 

during the remainder of 2007, and significant additional sand inputs from the Paria and 

Little Colorado River established even greater sand enrichment in the system for the 

winter and spring of 2008. 

REVIEW OF REVISED PLAN 

 In late December 2007, GCMRC requested a review of the 2008 High Flow 

Experimental Science Plan. The plan had received significant changes since the SA 

review in February, 2007. New studies had been added, the text had approximately 

doubled to over 100 pages, and the total cost had increased over one million dollars. 

Review Charge to SAs 

 A review charge and schedule was developed for the revised plan. The SAs and 

SA Executive Director selected a rapid review procedure that is to be finalized (final 

review report) with an executive summary forwarded to the GCMRC Chief by January 

14 (Appendix A). The reason for the rapid review is that the Science Plan is scheduled as 

a topic of an AMWG conference call by the Secretary Designee January 17, 2008. 

Structure of Review 

 This review is structured into two primary sections as follows: 

• SA general comments on the high flow science plan 

• SA specific comments on the high flow science plan 

 The SAs specific comments are indexed to page and paragraph of the text. 

Comments are also addressed to Appendix A and Appendix B. 

6
SA GENERAL COMMENTS ON THE HIGH FLOW SCIENCE PLAN 

 This science plan responds in a very structured manner to implementation of a 

2008 high flow event. It builds on both scientific knowledge and adaptive management 

approaches of the last decade, specifically information developed over the last three 

years. Significant advances in scientific findings and documentation have occurred from 

2005-2008, including the following: 

• Status of Knowledge 

• Knowledge Assessment 

• Science Planning Group and GCMRC assessments and proposals 

• April 10-11, 2006 Scientist Workshop and Assessments 

• HBC Age Structure Mark Recapture (ASMR) population assessments 

 Following are general comments of the SAs on overall plan elements and 

proposed studies included in the plan. 

• The Science Advisors feel the overall plan is acceptable for implementation. The 

SAs have reviewed the plan with the objective to identify areas for potential 

improvement. 

• The plan overview of findings of the 1996 and 2004 high flow experiments are 

critical, as well as science information that has been developed to extend the knowledge 

gained from the high flow events. The high flow experiment has transitioned from focus 

of high flow impacts on sediment to the more complete array of Colorado River 

Ecosystem resources. 

• The two merged AMP thrusts of resource enhancement and learning have been 

important to the interactive collaboration of scientists and managers on the 2008 high 

flow event. This focus permits one to put the high flow into proper perspective as relates 

to overall AMP goals. 

• The Executive Summary is very good, especially they way it describes what 

makes this experiment different than 1996 and 2004. You may want to change the 

1996 write up to bullets, and add something about effects on Lake Powell from proposed 

studies. 

• One of the justifications given for a March experiment on p 8 (#2) is that life 

7
history strategies of fish and other aquatic organisms have evolved with spring high flows 

from mountain snowmelt. That may be true, but we doubt the hydrograph historically 

peaked as early as March each year. The rising limb of the spring hydrograph may begin 

in the Grand Canyon in March, but would not have peaked until several months later. 

We question this particular justification for selection of the March date. 

• Studies 1 A-D: The plan contains limited information about actual details of the 

methods to be used. This may reflect length constraints for the plan as a whole. We don't 

feel too uncomfortable with the overview, because GCMRC has consistently done a very 

good job in the past, but it would be nice to see more details on some of the new efforts 

in 1C in particular, such as exactly how they plan to measure aeolian transport, how long 

monitoring will continue after the BHBF, and details of the spatial sampling (number of 

gullies, resolution of surveys). 

 We are concerned by the lack of detail regarding the geomorphic aspects of 1D, 

the study of backwaters. It is very good to explicitly focus on backwaters. The summary 

comments (p. 43) indicate some integration among 1A-1D and geographically 

throughout the study area, but the integration of 1D with the other components of Study 1 

does not appear to be well developed. Backwaters are fundamentally a reflection of 

channel-margin processes and thus must eventually be integrated into a quantitative 

sediment budget model and eddy-dynamics model. The lack of identification of 

investigators, and the emphasis on changes in form without any apparent link to process, 

makes it unclear how useful the measurements described in 1D will be related to 1B. 1D 

is a "pilot study", but it should be integrated as effectively as possible into the other 

geomorphic studies -- and use the BHBF as effectively as possible -- by providing 

evidence that the pre- and post-flood topographic surveys are the most useful information 

that can be gleaned from backwaters during the BHBF (or at least balance time/cost vs 

utility) for incorporation into linked hydraulic-sediment models of channel-margin areas 

(1B) and sediment budget models (1A). 

 Because of the enormous size and logistical challenges of the Colorado River 

ecosystem study area, the investigators take either a "black box" statistical approach 

where they track changes in geomorphic components (beaches, backwaters) throughout 

the canyon in relation to the BHBF, or take a more site-specific, mechanistic approach in 

8
which they identify and measure processes responsible for geomorphic changes at a more 

limited subset of sites. Reading through the limited details provided on Study 1 (mainly 

parts 1C and 1D), it is not clear what balance GCMRC scientists are striking between 

these two endpoints. One of the goals of 1D is to determine where backwater habitats 

will develop, but isn’t that really part of the goals of 1-B and 1-C. The “High-flow 

Science Questions” are proper things to examine, but most of the effects appear to be 

sediment moving questions. This leads to a bigger question: How do the high flow 

experiments fit into the bigger picture, i.e. LTEP? For example, how do you best 

conserve sand under normal flows? 

• Study 1.C: This study proposes to examine how high flows from the GCD and 

“normal” annual releases will: 1) Contribute to -- or subtract from -- the amount of 

sediments on sandbars, especially “campable” ones; and 2) Determine whether or not 

aeolian sands will be moved by Canyon winds up and over archaeological sites to protect 

them from the tourists and possibly fill in the erosion gullies currently decimating many 

of the sites, both of these will contribute to the well-being of the Grand Canyon. The 

Abstract for the study admits, however, that the high flow experiments of 1996 and 2004 

did little to “increase campable areas at sandbars on a more sustainable basis” (p. 26). 

The immediate question is, why might the next one produce a more positive outcome? 

The Abstract goes on to ask, “Do sandbars deposited by high-flow experiments 

contribute to the preservation of archaeological sites in the river corridor?” The answer, 

at least as observed by those on the June 2007 SA river trip, is that sandbars, however 

derived, do not appear to contribute to the preservation of sites. The sites that were 

reviewed are melting away through water erosion, wind erosion, and trampling. The big 

sites we saw at the Palisades area would require many cubic meters of aeolian sand to fill 

existing gullies that run directly through the sites and then remain there. A relevant 

question is, assuming the sand did somehow get properly distributed, how would such 

loose deposits resist fast running water coming down through the existing gullies from 

cliffs and terraces above? The check dams previously built across the gullies at the 

Palisades sites were obviously of no avail. This is not sufficiently addressed in the study 

methods. 

9
The general study of sediment transport and deposition on the Canyon sandbars, 

campable or not, is a legitimate scientific issue, one that is critical to the health of the 

Canyon. From what we can see, GCMRC has assembled an excellent team to do the 

general sediment parts of the study. Getting more sediment into the system to form more 

beaches seems to work. 

 The part of the study relating to the cultural sites does not appear to be a 

legitimate scientific matter, at least as stated in Section 1.C. It is, rather, an ethical 

archaeological issue (Fowler2

, Jolie and Salter 2008; Green 2008). Archaeological sites 

are containers of cultural and scientific data. When archaeological sites are threatened by 

natural actions, vandalism, or federally sanctioned activities, archaeologists are bound 

ethically, scientifically, and legally to insure that the data they contain are collected, 

preserved and made part of the public record. 

 Given all the data on the Grand Canyon sites contained in all the “stakeholder” 

archaeological studies, it is clear that most, if not all, of the archaeological sites on the 

lower terraces in close proximity to the river are endangered to greater or lesser degrees. 

Those melting away through erosion and trampling should be excavated as soon as 

possible. Is the proper course of action to wait several years to see if sediment, which 

may or may not be generated as a result of a number of high flow experiments, will blow 

over the sites and fill the ever deepening gullies running through them, thereby 

“conserving” them. The proposed “scientific approach” might in some locations be 

effective. However, in many locations it may only result in a loss of information 

valuable to the scientific community and cultural information valuable to the Indian tribes 

concerned with the Grand Canyon. The great concern with this approach is that it has 

significant risk that the solution may come to late, if it comes. The unspoken coda is we 

will lose some more of the cultural sites and the information they contain. That doesn’t 

sound like either good archaeological science or good archaeological ethics. It would be 

 

2

 Fowler, D.D., E.A. Jolie and M.W. Salter. 2008 Archaeological Ethics in Context and Practice, In 

Handbook of Archaeological Theories, edited by R.A. Bentley, H. Maschner and C. Chippindale, pp.409-

422. AltaMira Press, Lanham, Md. 

Green, T. J. 2008 Cultural Resource Management. In Handbook of Archaeological Theories, edited by R.A. 

Bentley, H. Maschner and C. Chippindale, pp.375-394. AltaMira Press, Lanham, Md. 

10
most useful if many more specifics as to possible outcomes of the “experiment” in 

relation to the cultural sites could be provided. How specifically does, or might, aeolian 

sands get blown onto sites and what keeps them there? How, specifically, does, or might, 

aeolian sands get blown into erosion gullies across sites and what keeps them there? The 

questions are not meant to be facetious, but rather to say, “provide us with more 

information.” As presently stated, the “experiment” does not read like a well designed 

inquiry into a difficult, possibly intractable, problem. 

 It is of interest that the Bureau of Reclamation has issued a request for proposals 

to excavate several sites that will be threatened by the proposed high flow experiment. 

This is an appropriate response given the relevant federal laws and guidelines relating to 

the mitigation of threatened cultural resources. It is of further interest, that none of the 

relevant archeological studies generated by other “stakeholder” agencies are cited or 

mentioned in the current BOR document, nor are any relevant archaeological studies 

from GCMRC. It would be very useful to know why this dichotomy exists in the GCD 

AMP. 

• Study 1.D: This study has 2 goals, one of which is to determine use of 

backwaters by native and nonnative fishes. This relates to scientific questions posed by 

GCMRC (Table 1), specifically, the question of how important is backwaters and 

vegetated shoreline habitats to growth and survival of young native fish. Some confusion 

does exist as to what assessments in this study are really being accomplished with the 

high-flow, as versus the proposed longer term efforts. 

 In paragraph 3 of this plan it states that highest densities of humpback chub occur 

in vegetated shorelines and only 5% or less are captured in backwaters. This indicates 

that some shorelines (perhaps eddies or shallow runs) are important for the fish. 

However, “The relative value of backwaters for native fishes as compared to other 

habitats is not evaluated with this study.” BHBF effects on vegetated shorelines in 

particular would appear to be of interest if that is where most of the humpback chub are 

in the mainstream Colorado River. The plan later notes that measurement difficulties 

make the assessment intractable. 

 Shorelines would be greatly affected by a BHBF and perhaps affect the fish in 

several ways. Humpback chub are insectivores, and some benefits would result from 

11
flooding habitats and making terrestrial insects more available for food. Conversely, 

disruption in the aquatic habitats occurs with inundation and scouring of vegetated areas. 

Thus, the effects of BHBF on shoreline fish habitat, and the use of vegetated shorelines 

by native fishes (especially humpback chub) should be included in this study if feasible. 

GCMRC might consider some sampling of shorelines located in the vicinity of 

backwaters for fish abundance, water temperature, food base, etc.? 

 Methods (p.38) state that an effort will be made: “to assess as many backwaters as 

possible.” This suggests that there may be more backwaters than there is time to sample 

all of them. In this case, it is important to consider just what constitutes a backwater that 

will be studied? Discussions on the river trip suggested that only very large and more 

permanent “backwaters” will be sampled– smaller alongshore embayments would not. If 

this is true, then sampling bias could be a problem. This is a concern because very large 

and more permanent backwaters in the upper basin tend to harbor some of the more 

aggressive nonnative fishes (e.g., centrarchids). If there may be more backwaters than 

can be sampled, then selection criteria are needed to guide sampling. In this case, a range 

of backwaters should be selected that would include more ephemeral as well as more 

permanent types. Finally, the study should address what attributes constitute the “best” 

target “backwaters”— is it area, depth, substrate, current, morphology, etc. 

 On page 39, it says that water temperatures will be taken in all backwaters 

sampled and in the mainstream. This should be extended to include temperatures of 

shallow shoreline eddies or runs. It would be instructional to find out how backwater and 

shoreline temperatures vary. On page 41, it states that one of the products would be to 

compare backwaters with “nearshore areas”. This needs to be discussed more fully. How 

would such comparisons be made and how would nearshore areas be selected for foodbase studies? How will these areas be characterized and would the impact of BHBF on 

vegetated shorelines be evaluated? Again this seems more appropriate for longer term 

assessments as well. 

 It seems that everyone has a different idea about what is a backwater. In a 

publication by Armantrout, N.B. (1998). Glossary of aquatic habitat inventory 

terminology American Fisheries Society, Bethesda, MD; six different definitions for the 

12
term “backwater”were provided. Thus, the term needs to be defined more clearly up front 

and throughout the plan (e.g., p. vi). 

 Table 1, p. viii, We would like to see 1.D. (b) be changed to: “ how many fish use 

them” and a part (c) added to indicate: “why fish use them”. 

Overall, Study 1.D is a good design, but why the emphasis solely on 

autochthonous production, particularly in backwaters. Many of the backwaters we have 

observed on river trips are surrounded by lush growth of riparian plants. Since chub are 

opportunistic feeders, and since we have still not yet seen a definitive report on how 

important autochthonous versus allochthonous production of organic matter is to the 

overall energy budget of the river, it seems this study should include estimates of riparian 

material inputs to backwaters and their potential importance for fish. Allochthonous 

inputs to backwaters may be important, and estimates could be done with 13C isotopic 

analysis of sediment, or possibly even litter or sediment traps. 

 Table 4 (p. 40), does not include a schedule for ecological measurements of 

chlorophyll, NPP, phytoplankton, or zooplankton. 

Study 2: The revisions in Study 2, riparian vegetation study, has improved the 

overall approach. It is a good study to conduct as part of an assessment of resource 

effects. Questions of the rate of recovery of flooded river banks and bars, or 

establishment on newly bare deposition surfaces relate back to questions of substrate 

stability, recreational uses, and potential allochthonous inputs of organic matter to the 

river and backwaters. We are not sure the theoretical discussion of invasibility of various 

sites based on species richness is very helpful, and there are a host of recent studies 

specifically on species composition of riparian ecosystems, including many in the 

Colorado River Ecosystem, that go uncited. Look at these papers and the references 

therein: 

Adair, E.C., D. Binkley, D.C. Anderson 2004. Patterns of nitrogen accumulation and 

cycling in riparian floodplain ecosystems along the Green and Yampa rivers. Oecologia 

(2004) 139: 108–116. DOI 10.1007/s00442-004-1486-6 

and 

13
Uowolo, A.L., D. Binkley, and E. C. Adair 2005. Plant diversity in riparian forests in 

northwest Colorado: Effects of time and river regulation. Forest Ecology and 

Management 218:107-114 and references therein. 

 The working hypothesis for this effort is good, and can be answered with surveys 

of species composition. I do not think the alternative hypotheses, which are more 

complex and less robust, can be addressed well enough in the absence of better 

familiarity of current literature and with the proposed study design. The riparian study is 

a good example of why there is need for a broad ecosystem approach to understanding 

river physical and ecological dynamics. 

 The study design has not been cross-fertilized by other investigative efforts going 

on now or in the past. One unpublished report by Kearsley is cited for methods, location, 

and sample design. Where is the justification from the literature for attempting to link 

species establishment to grain size, soil C and soil N? And how does that relate 

specifically to the paragraph on species richness? A reference from prior studies of 

buried organic matter that might be helpful is: Parnell, R.A., Jr., Bennett, J., and Stevens, 

L., 1999, Mineralization of riparian vegetation buried by the 1996 controlled flood, in 

Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., eds., The Controlled Flood 

in the Grand Canyon: Washington, D.C., American Geophysical Union, Geophysical 

Monograph Series, v. 110, p. 225–240. Personal communication with Dr. Jennifer Tank, 

who is a participant in the ongoing food base study, notes river water N concentrations 

are unexpectedly high from Lake Powell all the way down to Lake Mead, suggesting that 

a nuanced approach toward addressing the links between soil nutrients, flooding, and 

species establishment could provide interesting results. However, that should be 

developed with more care and understanding of riparian species-biogeochemical 

linkages. 

SA SPECIFIC COMMENTS RELATED TO SECTIONS OF THE PLAN 

 Following are developed comments that relate to specific sections of the plan. As 

such, these comments are indexed to page and paragraph of the text. 

 P1 P3: The text might lead one to conclude that Appendix A and Table A.1 

provides information on costs and benefits associated with the high flow event. 

14
Appendix A does provide general treatment of issues identified by stakeholders which is 

helpful. Cost Benefit Analysis (CBA) information, however, is not provided. The SAs 

note that provision of some science effort to develop a simplistic CBA tool for tradeoff 

analysis would be beneficial for evaluations necessary for effective adaptive 

management. 

 P2 P1: It needs to be stressed that the study area is only part of the Colorado 

River ecosystem, and the text and table should be revised to indicate that this is only a 

part of the greater ecosystem — not the entire ecosystem. Political boundaries defeat the 

purpose of viewing the entire Colorado River ecosystem as a functional whole. 

 P5 P3: It refers to Figure 3 as evidence that humpback chub populations 

increased in the period 1994 to 2000. However, this figure shows overlapping confidence 

intervals at the 95% level. Thus, the statement doesn’t seem very credible. If the CIs 

shown are correct, then tests of significance would show that there may be no difference 

among those years. The text should tell us at what level we would be willing to “not 

accept” the null hypothesis (no difference). 

 P5 P 2-3: Although it is not inaccurate to make the statement here that tracking 

increased levels of HBC adults and juveniles through use of ASMR would indicate no 

impacts of high flow events (1996, 2004), it is good that it is treated more as a hypothesis 

statement for testing than a test result. 

 P8 P2: March dam releases may simulate spring flow levels, but not the 17o C 

elevated temperatures. 

 P8 P5: Will the food base and trout assessments test the hypothesis relating to 

algae response from “cropping”. 

 P9 P2: The authors do not say that “sufficient sand” has been transported into 

lower Marble and Grand Canyon to produce an effective test. Is the longer time period of 

5-19 months at MLFF “assumed” or “not assumed” to have transported sufficient sand 

downstream? #1 a P8 P1 implies that the sand is still in Marble Canyon. P9 P3 seems to 

imply that the sand is more evenly distributed through the canyon. At this time, February 

2008, what is the confidence level that sufficient sand exists throughout Grand Canyon to 

conduct the test? 

15
 P11 Table 1: Can the question be answered by just this one test? Or are you 

saying that if deposits are at some optimum level “the test result” could surely be 

represented at some pre-assigned confidence level? 

 P11, Q 1.D on HBC: What assumed criteria or “quality backwater factors” are 

established that are assumed to benefit HBC? Will a combination of these positive 

factors be used to rank backwaters from “better” to “worse”? Or, is “quality” determined 

by presence or absence of HBC? Not sure if the question is properly specified. 

 P11, Q1.C: The question appears to be clearly specified to permit measurement 

and test. However, can assessments be made in reasonable times to protect resources? 

 P12, Q-4. A & B, RBT: The question about RBT movement to Marble and 

Grand Canyon might not be appropriate specification. That is, movement may not 

normally occur at all under lower flows. However, high flows could cause the young and 

old life phases to be swept downstream. Or, is the test directed at determining which life 

stage is most vulnerable to movement by high flows? 

 P 12 Q-3: Food base effects. Greater insight exists on this question by reading 

the section on study 3. The primary initial factors affecting food base is water flow 

velocities. Over the longer run water quality and its effects on primary productivity 

seems critical. 

 P12 Q-5 Lake Powell Water Quality: Changes in Lake Powell during 

drawdown should be predictable and able to be simulated with a dynamic model. The 

research question should look more at how imposed currents will react with the lakes 

thermal structure during drawdown. 

 P12 Q-6 Cultural Resources: The issue of direct high flow water and sediment 

impacts to cultural sites would seem predictable by site location, and presence or absence 

of vegetation. It seems we are trying to use the tests to develop hypotheses rather than 

test hypotheses. 

 P12 Q-2 Vegetation: Is it assumed that this will be the tested hypothesis? 

 P12 P1-2: These paragraphs seem to defend the position that much of the 2008 

test would be directed at formulating hypotheses to test in the future, rather than testing 

hypotheses already developed. The position taken appears to be one in which more study 

16
is needed to accurately formulate good hypotheses about food base and backwaters that 

can be tested in a later high flow event. 

 P13 P1-3: This section provides a good overview of what of the science of CRE 

hydrology, sedimentology and geomorphology is most effectively known i.e. can be used 

to accurately predict other events, and what areas still need more extensive learning. 

 P19 P4: It is unclear what is meant by, “based on the findings of a future high 

flow within 12-24 months of the next high flow.” 

 P35 P1: It is difficult to determine how the research will relate “occupation” and 

“physical site characteristics”. Correlation methods are assumed such as principal 

component analysis, but it is not specified. It does not appear that the hypothesis test is 

fully specified at this time. Instead it appears that developed data will help with this 

process, as well as define a potential future hypothesis test. 

 P36 P1: It is stated that this study will not evaluate the relative value of 

backwaters and other habitats for native fish; but instead evaluate 1) their development 2) 

food availability 3) and presence or absence of native fish. And, these evaluations will be 

used to develop more comprehensive studies to evaluate HBC use of backwaters and 

other habitats. 

 P36 P4: Given the more constrained planned accomplishments, will the 

researchers be able to answer the last two strategic questions listed? 

 P39 P1: Is the second question meant to apply to aquatic food production in the 

entire CRE, or just backwaters? We assume backwaters, but it is not clear. 

 P50 P2: The researchers note that measurements have been taken on previous 

high flow, but they have not been linked to whole system carbon budgets. As such will 

none of the previous assessments be used in this experiment to confirm sampling 

procedures and/or other assumed characteristics of the food base? 

 P53 P3: The study of contrasts; i.e. MLFF monitoring data contrasted to high 

flow data should also provide input on sensitivity of results from measurement techniques 

to differing disturbance regimes, i.e. very high flow event. Will this be evaluated? 

 P56 P2: Under study goals the term “compensatory survival response” is 

mentioned as a mitigating factor for juvenile RBT survival. A similar term “strong 

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compensatory mechanisms” after emergence (P57 P5) is used in hypothesis 2. What are 

these mechanisms, i.e. how are they measured and documented? 

 P57 P3: Strategic Science Question. Earlier it is proposed that methods 

developed in studies 4A and 4B could possibly be transferred to native fish 

interpretations. What elements are being considered besides the sonic tracking method? 

 P62 P2: Occupancy assessments and sonic technology are proposed as the most 

reasonable methods to study RBT migration into Marble and Grand Canyon. Are these 

methods suited to HBC application? 

 P63 P2: Will sampling for relative abundance assessments also use the same three 

river strata? 

 P66 P4: Why would the MPS be needed at the ring outlets? Mixing would not 

have been accomplished here. Could additional benefit be derived from measurement 

during ramp up and ramp down of the event; i.e. assessment of any critical threshold 

values? You might consider changing the emphasis of this section to first the lake and 

second downstream. Leading these discussions with the downstream changes does not 

follow the title and is a backward way of assessment. You could add a modeling 

component to the study. It would provide more learning and future predictability. 

 P69 P1: Compliance monitoring. The text references a 2006-07 high flow 

experiment. Change to 2008. 

 P71-73: Synthesis of Knowledge. The proposed integrated synthesis report is an 

excellent approach to providing a more comprehensive look and assessment of the series 

of high flow experiments. Dedicating this specific assessment to evaluate interactive 

processes, linkages, integrated impacts etc, will realize important additional benefit from 

the assessments. Scheduling writing and assessment workshops will provide emphasis to 

the project activity. 

 P75 & 76; Table 6: The text and table are confusing as they present differing 

information on the same trips. We recommend the section be reevaluated by science and 

logistic staff and differences corrected. 

REFERENCE SECTION 

 The references have been screened to provide primarily information related to 

high flows or supporting information to specific conclusions, hypothesis or other 

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statements in the text. Some references, however, have been eclipsed by more current 

research. Some have limited relevance. For example, although use of Darwin (1859) to 

contrast theories of invasive species provides emphasis, recent work contrasting these 

positions provide greater clarity of differences. 

APPENDIX A: GCMRC RESPONSE TO ISSUES 

RAISED BY GCD AMP MEMBERS

 Issue 1. Table A.1: The table is a good representation of issues presented by 

members at the AMWG meeting and by TWG representatives. The documentation is an 

important part of the process.

 Issue 2: Although many questions are implied in Table A.1, they are not 

specified fully as questions. 

 Issue 4: Table A.2 provides sufficient information to focus on the primary 

differences in the two regimes. 

 Issue 6: Appendix B does clarify the difficulty in determining HBC associated 

impacts with high flows. 

 Issue 7: Will the proposed food base studies provide the comparative data to 

define a “net benefit” or “net loss” to the food base from flow impacts? 

 Issue 8: A question exists as to why a simplistic socio-economic impact 

assessment tool could not be developed with this or one of the past high flow tests. 

Significant benefit could be derived from, for example, a simple cost benefit analysis 

(CBA) model that captures the primary factors that can significantly shift costs or 

benefits. The tool could be used by AMWG in the future for looking at tradeoffs among 

options, i.e. time of application, length of event, size, etc. As noted in other comments, 

development of this tool might better be attached to GCMRC’s annual work plan where 

emphasis could be adjusted to overall AMP needs. However, it is important to recognize 

the need. 

 Issue 9: Although impacts to upper Lake Mead from this one high flow event 

may not be significant, the impact to a cultural site in Glen Canyon will be significant. 

However, planned actions for the necessary mitigation are being developed by BOR.

APPENDIX B: FACTORS INFLUENCING 

DESIGN OF HIGH FLOW EXPERIMENTS 

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 P 97: This Appendix does highlight the difficulties to determine impacts of a high 

flow event on the HBC. The reference to continued monitoring activities does provide 

insight into possible identification of significant departures should they occur. However, 

finding reference points for this single event may not be possible, due to variance in the 

system. Again this points to a need to provide more reference of how the high-flow 

outcomes will link to the LTEP. Perhaps a prologue should be developed to discuss 

sediment conservation. GCMRC has discussed the merit of testing equal monthly 

volumes under 8.23 constraints. With lower fluctuating flows, i.e. 7-13,000 cfs, 

minimum compliance would sum to be required for the test. 

 Table B.1: Please note the second March trip must be an August trip due to 

location in list, and it is noted as “autumn.” 

 P99-104: This discussion of testing new methods for evaluating HBC abundance, 

movement, use of habitat etc, is an appreciated response to the SAs concerns over HBC 

assessments in the first science plan draft. Discussion and proposed attempts at new 

methods, i.e. sonic tag assessments and occupancy assessments are encouraged. 

Although probable success is limited in isolating direct flow impacts to HBC population, 

tracking movements could benefit other assessments relating to competition and habitat 

change. 

 

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