USGS Workshop on Scientific Aspects of a 

Long-Term Experimental Plan for Glen Canyon

Dam, April 10–11, 2007, Flagstaff, Arizona

Open-File Report 2008–1153

U.S. Department of the Interior

U.S. Geological Survey

USGS Workshop on Scientific Aspects of a 

Long-Term Experimental Plan for Glen Canyon 

Dam, April 10–11, 2007, Flagstaff, Arizona 

A report of the USGS Grand Canyon Monitoring and Research Center 

Open-File Report 2008-1153 

U.S. Department of the Interior 

U.S. Geological Survey 
U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2008 

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Suggested citation: 

Grand Canyon Monitoring and Research Center, 2008, USGS workshop on scientific 

aspects of a long-term experimental plan for Glen Canyon Dam, April 10–11, 2007, 

Flagstaff, Arizona: U.S. Geological Survey Open-File Report 2008–1153, 79 p. 

Cover: Humpback chub (photo courtesy of Arizona Game and Fish Department); 

sand grains on the surface of a Colorado River eddy sandbar (USGS photo by David 

Rubin); sign at entrance of Grand Canyon National Park (USGS photo by Don Becker); 

and Secretary of the Interior Kempthorne opening the jet tubes at Glen Canyon Dam 

(USGS photo by Anne Phillips). 
Content 

Executive Summary............................................................................................................................. 1

Introduction and Background ........................................................................................................... 5

Role of Science ................................................................................................................................ 6

Workshop Purpose and Scope ......................................................................................................... 7

Context for Workshop Discussions................................................................................................ 10

Management Objectives .............................................................................................................. 10

Resources, Conditions, and Trends ........................................................................................... 13

Discussions ........................................................................................................................................ 21

Flow Treatments ............................................................................................................................ 21

Nonflow Treatments ..................................................................................................................... 24

Workshop Outcomes ........................................................................................................................ 28

Environmental Triggers Approach ............................................................................................. 28

Comparison of Environmental Triggers Approach to Science Planning Group Options.. 32

Conclusions ........................................................................................................................................ 33

References ......................................................................................................................................... 36

Appendix A.Workshop Participants and Attendees ................................................................... 44

Appendix B.Flow and Nonflow Treatments Associated with Various Experimental Science 

Planning Group Options and Environmental Triggers Approach.............................................. 47

Appendix C.Summary of Post-Workshop Telephone Conference Call (April 26, 2007) ........ 51

Appendix D.Participants Abbreviated Curriculum Vitae............................................................ 55

Appendix E.Responses to EIS Cooperator Questions................................................................. 72

Figures 

1. Map of the Colorado River ecosystem below Glen Canyon Dam, Ariz. ............................. 6 

2. Simplified illustration of a decision tree based on humpback chub responses to 

treatments compared to humpback chub goals/desired future conditions ........................... 31

Tables 

1. Core scientific questions identified by the Bureau of Reclamation and agencies 

cooperating in the development of the environmental impact statement for a long-term 

experimental plan for the operation of Glen Canyon Dam........................................................... 9 

2. Timeline with contingencies for environmental triggers experimental approach ........30

 iii
 iv
USGS Workshop on Scientific Aspects of a 

Long-Term Experimental Plan for Glen Canyon 

Dam, April 10–11, 2007, Flagstaff, Arizona 

Executive Summary 

Glen Canyon Dam is located in the lower reaches of Glen Canyon National 

Recreation Area on the Colorado River, approximately 15 miles upriver from Grand 

Canyon National Park (fig. 1). In 1992, Congress passed and the President signed into 

law the Grand Canyon Protection Act (GCPA; title XVIII, sec. 1801–1809, of Public 

Law 102-575), which seeks “to protect, mitigate adverse impacts to, and improve the 

values for which Grand Canyon National Park and Glen Canyon National Recreation 

Area were established.” The Glen Canyon Dam Adaptive Management Program 

(GCDAMP) was implemented as a result of the 1996 Record of Decision on the 

Operation of Glen Canyon Dam Final Environmental Impact Statement to ensure that the 

primary mandate of the GCPA is met through advances in information and resources 

management (U.S. Department of the Interior, 1995). 

On November 3, 2006, the Bureau of Reclamation (Reclamation) announced it 

would develop a long-term experimental plan environmental impact statement (LTEP 

EIS) for operational activities at Glen Canyon Dam and other management actions on the 

Colorado River. The purpose of the long-term experimental plan is twofold: (1) to 

increase the scientific understanding of the ecosystem and (2) to improve and protect 

important downstream resources. The proposed plan would implement a structured, longterm program of experimentation to include dam operations, potential modifications to 

Glen Canyon Dam intake structures, and other management actions such as removal of 

nonnative fish species. The development of the long-term experimental plan continues 

efforts begun by the GCDAMP to protect resources downstream of Glen Canyon Dam, 

including Grand Canyon, through adaptive management and scientific experimentation. 

The LTEP EIS will rely on the extensive scientific studies that have been 

undertaken as part of the adaptive management program by the U.S. Geological Survey’s 

(USGS) Grand Canyon Monitoring and Research Center (GCMRC), one of the four 

research stations within the USGS Southwest Biological Science Center. On April 10 and 

11, 2007, at the behest of Reclamation, the GCMRC convened a workshop with scientific 

experts to identify one or more scientifically credible, long-term experimental options for 

Reclamation to consider for the LTEP EIS that would be consistent with the purpose and 

need for the plan. Workshop participants included government, academic, and private 

scientists with broad experience in the Colorado River in Grand Canyon and regulated 

rivers around the world. Resource managers and GCDAMP participants were also present 

on the second day of the workshop. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

In advance of the workshop, Reclamation and LTEP EIS cooperating agencies 

identified 14 core scientific questions. Workshop participants were asked to consider how 

proposed options would address these questions, which fall primarily into four areas: (1) 

conservation of endangered humpback chub (Gila cypha) and other high-priority 

biological resources, (2) conservation of sediment resources, (3) enhancement of 

recreational resources, and (4) preservation of cultural resources. 

A secondary objective of the workshop was the evaluation of four long-term 

experimental options developed by the GCDAMP Science Planning Group (SPG) 

(appendix B). The flow and nonflow treatments called for in the four experimental 

options were an important starting point for workshop discussions. 

At the beginning of the workshop, participants were provided with the final LTEP 

EIS scoping report prepared by Reclamation. Participants were also advised that 

Reclamation had committed to “make every effort...to ensure that a new population of 

humpback chub is established in the mainstem or one or more of the tributaries within 

Grand Canyon” in the 1995 Operation of Glen Canyon Dam Final Environmental Impact 

Statement (U.S. Department of the Interior, 1995). This decision was consistent with the 

U.S. Fish and Wildlife Service’s 1995 biological opinion for Glen Canyon Dam 

operations that describes the establishment of a “second spawning aggregation” of 

endangered humpback chub as a reasonable and prudent alternative. 

Before beginning their discussions, workshop participants were also briefed by 

GCMRC scientists on the current status and trends of downstream resources, particularly 

native and nonnative fish and sediment resources. The following findings were presented 

to the participants and provided the basis for workshop discussions: 

• Nonnative fish removal efforts from 2003–06, including the removal of more than 

19,000 rainbow trout (Oncorhynchus mykiss), seem to have accelerated the decline of 

rainbow trout in the vicinity of the confluence of the Little Colorado River, a tributary 

of the Colorado River in Grand Canyon. Possibly in response to the reduction of 

competitive and predatory nonnative species, native fish represented 60 percent of the 

fish community captured near the confluence of the Little Colorado River in 2006, 

which was up from 10 percent in 2003 (U.S. Geological Survey, unpub. data, 2007); 

however, natural warming caused by warmer than average releases from Glen 

Canyon Dam (2004−06) is a confounding factor in determining the impact of 

mechanical removal on native fish. 

• Between 2001 and 2005, the number of adult humpback chub (age-4+) appears to 

have stabilized at approximately 5,000 (Melis and others, 2006). A summary of the 

analysis of the Grand Canyon humpback chub published after the workshop 

concludes that the adult population in 2006 was approximately 6,000 (Coggins, 

2007). The number of humpback chub younger than 4 years of age appears to have 

reached a modern low in 1991, but in 2001, the most recent year for which data are 

available, population numbers have increased to the levels found during the late 

1980s. There is also some indication that a few young humpback chub survived in the 

mainstem nearshore habitats near river mile 30, which is above the Little Colorado 

River, during the winter of 2005–06 (U.S. Geological Survey, unpub. data, 2007). 

• Bluehead sucker (Catostomus discobolus) and flannelmouth sucker (Catostomus 

latipinnis) catch rates increased fivefold between 2003 and 2006 (Arizona Game and 

 2
Fish Department, unpub. data, 2007; U.S. Geological Survey, unpub. data, 2007). The 

presence of multiple size classes of flannelmouth sucker indicate that this species has 

successfully recruited during this period. 

• Substantial increases in total eddy-sandbar area and volume are only possible during 

high-flow releases following large tributary floods, which enrich sand supplies in the 

main channel of the Colorado River (Rubin and others, 2002; Topping and others, 

2006). 

• Sandbars created by the 2004 beach/habitat-building flows (BHBF) test increased the 

windborne transport of sand toward some of the archaeological sites in Grand Canyon 

(Draut and Rubin, 2006). Increased sand carried by the wind from restored sandbars 

may reduce erosion and increase the preservation potential at some sites. 

Participants discussed the pros and cons of the possible flow and nonflow 

experimental treatments identified by the SPG. Flow treatments considered by 

participants included steady, fluctuating, and beach/habitat-building flows. Nonflow 

treatments included the installation of a temperature control device (TCD), also called a 

selective withdrawal structure; nonnative fish control; humpback chub translocation; and 

increased mainstem water temperatures. The discussions relied on the available scientific 

literature and professional opinion. Workshop participants reached the following 

conclusions: 

• The single most important condition that would benefit the endangered humpback 

chub in the near term is warming mainstem nearshore habitats, although control of 

nonnative species is also very important. Given existing volumetric constraints and 

the current state of knowledge, the most readily available tool to stabilize the 

presence and persistence of nearshore habitats and, thus, enhanced warming in those 

environments during the summer months, is steady flows from Glen Canyon Dam. 

• Additional BHBF tests should occur following tributary sand enrichment and be 

evaluated to determine whether this treatment is capable of rebuilding and 

maintaining sandbars in a sustainable manner or if augmentation of the downstream 

sand supply is needed to achieve sediment conservation goals. 

• A TCD should be built only if it is designed to release the warmest water possible. 

Additionally, the TCD must have the ability to release cool water under all 

conditions, including when reservoir conditions are relatively low. The ability to also 

release cool water was thought to be necessary to control the expansion of warmwater 

nonnative aquatic species. 

• Managers should continue their efforts to control nonnative fish numbers, including 

both warmwater and coldwater species, especially in the vicinity of the Little 

Colorado River, where more than 90 percent of the Grand Canyon population of 

humpback chub spend most of their lives. 

• Monitoring efforts should be increased for warmwater nonnative fish because they 

pose a significant risk to the humpback chub population and their numbers may 

increase if warmer water temperatures continue. Early, consistent monitoring of 

warmwater species is critical to successful control. It is highly unlikely that these 

species can be controlled as readily as rainbow trout. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

• The risk of catastrophic loss of Grand Canyon humpback chub would be reduced if 

one or more populations were reproducing and growing in the mainstem Colorado 

River or in another Grand Canyon tributary. The best possible alternative for a 

spawning location is the main channel of the Colorado River. 

• Translocation of young humpback chub from the Little Colorado River to one or 

more of the tributaries the Colorado River could be beneficial for the Grand Canyon 

humpback chub population, providing a refuge and perhaps expanding the population. 

It was considered unlikely that such translocations would confound humpback chub 

monitoring or population modeling. 

Following discussions of possible treatments, the participants developed an 

experimental research design that was consistent with the stated purpose and need of the 

LTEP EIS. The experimental design, called the environmental triggers approach, uses 

environmental cues to trigger new experimental treatments or management actions. The 

best defined of these environmental triggers is the delivery of additional sediment from 

tributary streams to trigger BHBF tests. 

An important element of the environmental triggers approach requires the 

specification of desired future conditions, or measurable targets, for humpback chub, 

sediment conservation, archaeological sites, camping beaches, and other resources of 

interest to managers. Explicit desired future conditions will provide reference points for 

evaluating treatment effectiveness and the need to implement additional treatments or 

management actions. Workshop participants also recommended a comprehensive 

monitoring program for native and nonnative fishes. The results of monitoring would be 

used to trigger changes in dam operation and nonnative fish control. 

From 2009 through 2012, before a TCD could be built, the participants 

recommended testing summer and fall steady dam releases. The environmental triggers 

approach includes the construction and testing of a TCD. 

Because it takes at least 4 years for humpback chub to reach maturity (reviewed in 

U.S. Fish and Wildlife Service, 2002), treatments should be applied for 4 consecutive 

years to measure biological response, especially in the humpback chub population. 

However, shorter, isolated flow treatments, such as beach/habitat-building flows, would 

be likely to provide new information about sediment conservation strategies and possible 

benefits to other resources. 

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Introduction and Background 

Glen Canyon Dam, one of the last major dams built on the Colorado River, is 

located in the lower reaches of Glen Canyon National Recreation Area, approximately 15 

miles upriver from Grand Canyon National Park (fig. 1). The international prominence of 

Grand Canyon and public concern about the impacts of the dam resulted in Federal 

efforts to protect downstream resources. In 1992, Congress passed and the President 

signed into law the Grand Canyon Protection Act (GCPA; title XVIII, sec. 1801–1809, of 

Public Law 102-575), which seeks “to protect, mitigate adverse impacts to, and improve 

the values for which Grand Canyon National Park and Glen Canyon National Recreation 

Area were established.” The Glen Canyon Dam Adaptive Management Program 

(GCDAMP) was implemented as a result of the 1996 Record of Decision on the 

Operation of Glen Canyon Dam Final Environmental Impact Statement to ensure that the 

primary mandate of the GCPA is met through advances in information and resources 

management (U.S. Department of the Interior, 1995). 

On November 3, 2006, the Bureau of Reclamation (Reclamation) announced it 

would develop a long-term experimental plan environmental impact statement (LTEP 

EIS) for operational activities at Glen Canyon Dam and other management actions on the 

Colorado River. The stated time period for the LTEP EIS is 2009−19, and the 

downstream environment it considers, known as the Colorado River ecosystem (CRE), 

encompasses the Colorado River corridor from the forebay of Glen Canyon Dam to the 

western border of Grand Canyon National Park (fig. 1). The proposed plan would 

implement a structured, long-term program of experimentation including dam operations, 

potential modifications to Glen Canyon Dam intake structures, and other management 

actions such as removal of nonnative fish species. The purpose of the long-term 

experimental plan is twofold: (1) to increase the scientific understanding of the ecosystem 

and (2) to improve and protect important downstream resources. This LTEP EIS process 

is consistent with and implements the provisions of the settlement agreement recently 

executed between the United States and the Center for Biological Diversity and other 

environmental groups in the Center for Biodiversity v. Kempthorne litigation regarding 

the operation of Glen Canyon Dam. 

The development of the long-term experimental plan continues efforts begun by 

the GCDAMP to protect resources downstream of Glen Canyon Dam, including Grand 

Canyon, through adaptive management and scientific experimentation. As a result, the 

LTEP EIS will rely on the extensive scientific studies that have been undertaken as part 

of the adaptive management program by the U.S. Geological Survey’s (USGS) Grand 

Canyon Monitoring and Research Center (GCMRC), one of the four research stations 

within the USGS Southwest Biological Science Center. The GCMRC conducts scientific 

monitoring and research for the Glen Canyon Dam Adaptive Management Program. 

On April 10 and 11, 2007, at the behest of Reclamation, the GCMRC convened a 

workshop with scientific experts to discuss options for a long-term experimental plan to 

be considered by the LTEP EIS. The workshop involved scientists with broad experience 

in the Colorado River in Grand Canyon and regulated rivers around the world. Resource 

managers and GCDAMP participants were also present on the second day of the 

workshop. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Figure 1. Map of the Colorado River ecosystem, showing the Colorado River corridor 

that extends from the forebay of Glen Canyon Dam to the western boundary of Grand 

Canyon National Park.

Role of Science 

Experimental research plays an important role in providing information to land 

and resource managers and stakeholders participating in the Glen Canyon Dam Adaptive 

Management Program. The GCDAMP has been identified as a model for adaptive 

ecosystem assessment and management (Walters and others, 2000). The 1995 Operation 

of Glen Canyon Dam Final Environmental Impact Statement (U.S. Department of the 

Interior, 1995) was developed using experimental studies conducted between 1990 and 

1995. Over the past decade, monitoring and research data for CRE resources have been 

collected, evaluated, and reviewed for GCDAMP by the Grand Canyon Monitoring and 

Research Center. As early as 1998, sediment scientists published findings suggesting that 

the strategy for rebuilding and maintaining eroded sandbar habitats proposed in the 1995 

environmental impact statement needed to be reevaluated (Rubin and others, 1998). By 

2002, sediment researchers had identified alternative experimental flow strategies for 

conserving the limited sand supplies below the dam and recommended to managers 

specific tests tied to such strategies (Rubin and others, 2002). Gloss and others (2005) 

reported that many of the anticipated resource responses for sediment, endangered 

 6
humpback chub (Gila cypha), cultural sites, and other resources identified in the 1995 

environmental impact statement had not been realized. 

In response to the scientists’ earlier reports to stakeholders in 2002, and on the 

basis of recommendations from the GCDAMP later that year, the U.S. Department of the 

Interior approved new experimental flow and nonflow research for 2003 and 2004. This 

research was intended to promote learning about how CRE resources could be better 

managed to meet management objectives. The experimental research was approved for 

another 2 years (2005–06); however, the extension recognized the need for a longer term 

experimental plan for the program beyond 2006. GCDAMP participants and others called 

for a different approach than the one originally proposed in the 1995 environmental 

impact statement (U.S. Department of the Interior, 1995). In response, Reclamation 

proposed the preparation of an LTEP EIS. 

Workshop Purpose and Scope 

On April 10 and 11, 2007, the Grand Canyon Monitoring and Research Center, at 

the request of Reclamation, convened a workshop with scientific experts to discuss 

experimental options and treatments that could be considered during the development of 

the LTEP EIS for operational activities at Glen Canyon Dam and other management 

actions. The workshop took place in Flagstaff, Ariz. Reclamation has the lead 

responsibility for identifying alternatives consistent with various Federal and State laws, 

including, but not limited to, the Grand Canyon Protection Act, the Endangered Species 

Act, various laws and Supreme Court decrees known as the Law of the River, the Interim 

Shortage Criteria Environmental Impact Statement, and the Annual Operating Plan for 

the Colorado River. 

The workshop convened scientists with broad experience in the Colorado River in 

Grand Canyon and regulated rivers around the world. Participants came from the United 

States and Canada. The experience of the participants was diverse, with competence in 

fluvial geomorphology, river hydrology, and fish biology, especially in the regulated 

rivers of western North America. The participants are listed in appendix A and their 

abbreviated curricula vitae are presented in appendix D. 

The specific purpose of the eventual long-term experimental plan as stated in the 

Federal Register (December 12, 2006) is to: 

increase understanding of the ecosystem downstream from Glen Canyon Dam and to 

improve and protect important downstream resources. The NEPA [National 

Environmental Policy Act] process would evaluate the implications and impacts of 

each of the alternatives on all of the purposes and benefits of Glen Canyon Dam as 

well as on downstream resources. The proposed plan would implement a structured, 

long-term program of experimentation (including dam operations, modifications to 

Glen Canyon Dam intake structures, and other non-flow management actions, such 

as removal of non-native fish species) and monitoring in the Colorado River below 

Glen Canyon Dam. 

The proposed Long-Term Experimental Plan is intended to ensure a continued, 

structured application of adaptive management in such a manner as to protect, 

mitigate adverse impacts to, and improve the values for which Grand Canyon 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

National Park and Glen Canyon National Recreation Area were established, 

including, but not limited to natural and cultural resources and visitor use, consistent 

with applicable Federal law. 

The goal of the workshop was the identification of one or more scientifically 

credible, long-term experimental options consistent with the purpose and need for the 

long-term experimental plan. A research and monitoring program would be developed by 

the GCMRC following completion of the LTEP EIS. In addition to improving and 

protecting downstream resources, the purpose of the long-term experimental plan would 

be to increase scientific understanding of the ecosystem. Workshop participants were 

asked to consider how the proposed options would address 14 core scientific questions 

(table 1) identified by Reclamation and LTEP EIS cooperating agencies.1 The core 

scientific issues to be addressed by the plan fall primarily into four areas: (1) 

conservation of endangered humpback chub and other high-priority biological resources, 

(2) conservation of sediment resources, (3) enhancement of recreational resources, and 

(4) preservation of cultural resources. Following the workshop, GCMRC scientists 

developed answers to the first 10 core scientific questions based on the information 

presented and discussions undertaken during the workshop (see appendix E). 

A secondary objective of the workshop was the evaluation of four long-term 

experimental options developed by the GCDAMP Science Planning Group (SPG) 

(appendix B). The flow and nonflow experimental treatments called for in the four 

options were an important starting point for workshop discussions. Because the workshop 

was limited to 2 days, activities focused primarily on the two resources identified by 

Reclamation as priorities of the LTEP EIS: humpback chub and sediment. There was 

inadequate time to address the full range of resources or science questions of interest to 

resource managers. 

 

1

 State of Arizona—Arizona Department of Water Resources, Arizona Game and Fish Department, Bureau 

of Indian Affairs, State of Colorado—Colorado Water Conservation Board, Hualapai Tribe, Kaibab Band 

of Paiute Indians, National Park Service, State of New Mexico—New Mexico Interstate Stream 

Commission, Pueblo of Zuni, The Hopi Tribe, Upper Colorado River Commission, U.S. Fish and Wildlife 

Service, U.S. Geological Survey, Utah Associated Municipal Power Systems, State of Utah—Utah 

Department of Natural Resources, and Western Area Power Administration. 

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Table 1. Core scientific questions identified by the Bureau of Reclamation and 

cooperating agencies to be considered in the environmental impact statement for a longterm experimental plan for operation of Glen Canyon Dam. 

1. What are the factors limiting humpback chub reproduction and rearing in the main channel of 

the Colorado River below Glen Canyon Dam? 

2. Have humpback chub population estimates stabilized or increased recently, and if so, why 

(warmer water temperatures, nonnative control, other factors)? 

3. Will warming dam releases positively affect listed or special status species in the Colorado 

River ecosystem (including humpback chub and effects of nonnative species)? 

4. Can the decline in sediment resources since 1990 be reversed using “flow” options with 

remaining downstream sand supplies from tributaries (Paria and Little Colorado Rivers and 

lesser tributaries)? 

5. Will high-flow experiments promote conservation of high priority Adaptive Management 

Program biological resources (for example, native fishes, native riparian vegetation, aquatic 

food base, rainbow trout)? 

6. What effect do powerplant releases (ramp rates, fluctuating and steady) have on listed or 

special status species (including humpback chub) in the Colorado River ecosystem? 

7. Can the decline of humpback chub be reversed by expanding the current range of humpback 

chub into suitable unused historical habitat within Grand Canyon National Park and Glen 

Canyon National Recreation Area (tributaries/mainstem)? 

8. If the answer to core question 4 is yes, will enhanced sediment conservation promote in situ 

preservation of archaeological sites? 

9. How can invasive or nonnative species be eliminated, reduced, or controlled in the Colorado 

River ecosystem? 

10. If the answer to core question 4 is yes, will enhanced sediment conservation promote 

conservation of recreation beaches and campable area? 

11. How can the Lees Ferry trout fishery be improved? 

12. Will dam operations, including temperature changes, diel fluctuations, and high 

experimental flows, affect razorback sucker in Lake Mead and Grand Canyon? 

13. Will high-flow experiments affect the water quality released from Glen Canyon Dam? 

14. Can visitor experience (boating, camping, sightseeing, safety) be enhanced through 

alteration of the modified low fluctuating flow regime? 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Context for Workshop Discussions 

Before the workshop, participants were provided with the final public scoping 

report prepared by Reclamation, which also contained the purpose and need statement 

excerpted from the Federal Register notice of intent to prepare an environmental impact 

statement. Descriptions of the flow and nonflow treatments contained in the four 

experimental options developed by the Science Planning Group were provided to the 

participants in advance of the workshop and were an important starting point for the 

workshop deliberations (see appendix B for a summary of the treatments). Flow 

treatments included reduced or increased fluctuating flow releases, beach/habitat-building 

flows (BHBF) tests, and steady flow tests. Nonflow treatments included installation and 

operation of a temperature control device (TCD), or selective withdrawal structure, on 

Glen Canyon Dam and removal of nonnative fishes. The four SPG options were 

described by their proponents to the participants during a telephone conference call on 

April 5, 2007. 

At the beginning of the workshop, a Reclamation representative reviewed the 

purpose and need of the LTEP EIS for the participants. Participants were advised that the 

U.S. Fish and Wildlife Service’s (USFWS) 1995 final biological opinion on the operation 

of Glen Canyon Dam included a reasonable and prudent alternative calling for the 

establishment of a “second spawning aggregation” of humpback chub downstream of 

Glen Canyon Dam (U.S. Fish and Wildlife Service, 1995). Consistent with this 

alternative, Reclamation made an environmental commitment in the 1995 Operation of 

Glen Canyon Dam Final Environmental Impact Statement to “make every effort...to 

ensure that a new population of humpback chub is established in the mainstem [Colorado 

River] or one or more of the tributaries within Grand Canyon” (U.S. Department of the 

Interior, 1995). How a “second spawning aggregation” and a “new population” may be 

similar or different has not been formally determined. 

Workshop scientists were briefed about the current status and trends of native and 

nonnative fishes, sediment resources, and water release temperatures from the dam. 

GCMRC staff provided updates on preliminary and published results from past 

experimental research on both sediment and fish between 1996 and 2006. The briefings 

included information about two BHBF tests conducted in 1996 and 2004, the low 

summer steady flow (LSSF) of 2000, the 4-year-long experimental nonnative fish 

removal in specific reaches below the dam, and an overview of GCMRC fisheries 

research, including estimates of the Grand Canyon adult humpback chub population. 

Management Objectives 

The 1995 Operation of Glen Canyon Dam Final Environmental Impact Statement 

(U.S. Department of the Interior, 1995) identified resources that the preferred alternative 

(the alternative selected and described in the final EIS, along with the basis for selection) 

and other management actions might improve or affect. The natural and cultural resource 

categories identified included (1) sediment and aquatics, (2) vegetation, (3) wildlife, (4) 

endangered and other special-status species, (5) cultural resources, (6) air quality, (7) 

recreation, and (8) power. Because the humpback chub is a federally listed endangered 

 10
species, conserving the Grand Canyon population has long been a focus of management 

activities. Sediment conservation has also driven management efforts because of its 

relationship to other resources, including habitat, recreation, and cultural sites. 

Improvements projected in the 1995 environmental impact statement for a number 

of downstream resources, including both humpback chub and sediment, had not been met 

by 2004 (Lovich and Melis, 2005). As a result, humpback chub and sediment have been 

identified by Reclamation as the primary focus of the LTEP EIS. Workshop discussions 

were guided by the need to reach management objectives for these resources. In most 

cases, measurable targets have not yet been defined. 

1995 Biological Opinion Reasonable and Prudent Alternative 

The U.S. Fish and Wildlife Service prepared a biological opinion in 1995 on Glen 

Canyon Dam relating to operation and other criteria of the preferred treatment alternative 

for the 1995 environmental impact statement. The USFWS recognized that there were 

risks inherent to the entire Grand Canyon humpback chub population being dependent on 

a single tributary for spawning and rearing habitat, namely, the Little Colorado River, a 

tributary of the Colorado River in Grand Canyon (fig. 1). To help reduce this risk, the 

biological opinion required the establishment of a second spawning aggregation of 

humpback chub in Grand Canyon (U.S. Fish and Wildlife Service, 1995). 

The current Grand Canyon humpback chub population is heavily dependent on 

the Little Colorado River. More than 90 percent of the fish spend most of their lives in 

the lowest 11 miles of the Little Colorado River and in the reach of the Colorado River 

immediately upstream and downstream from the Little Colorado River (Paukert and 

others, 2006). This geographic constriction has some advantage for genetic 

homogenization (Douglas and Douglas, 2007) because the majority of the adult 

population remains in proximity to other adults, increasing the likelihood of complete 

mixing of genetic material during spawning, especially over a period of years. However, 

the geographic constriction also means that the population is susceptible to catastrophic 

loss. There is general agreement among scientists working with the Grand Canyon 

humpback chub population that the greatest risk from catastrophic loss would be an 

accidental spill of hazardous liquids (for example, petroleum products) where U.S. 

Highway 89 crosses the river drainage near Cameron, Ariz. (U.S. Fish and Wildlife 

Service, 2002). Just such an accident occurred in summer 2005 when a tanker truck 

carrying gasoline ran off the highway and overturned in Moenkopi Wash, a tributary of 

the Little Colorado River. Fortunately for the aquatic resources downstream, this accident 

occurred during a dry period when the wash did not contain running water. If water had 

been present, as regularly occurs during rainstorms, gasoline could have been transported 

to the Little Colorado River. Although other risks threaten the Grand Canyon humpback 

chub, the risk of an accidental spill may be the most critical, because if it occurs a large 

proportion of the population could be lost quickly along with the attendant genetic 

diversity (Douglas and Douglas, 2007). The risk of catastrophic loss would be reduced if 

one or more humpback chub populations were reproducing and growing in the mainstem 

Colorado River or in another Grand Canyon tributary stream. 

 11
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Sediment Conservation 

A recent synthesis of geomorphic data on sandbars below Glen Canyon Dam 

reported a 25 percent reduction in the sandbar area within the 87-mile reach from Lees 

Ferry to Bright Angel Creek between 1984 and 2000 (Schmidt and others, 2004). It is 

clear that managers are interested in mitigating further losses of these sediment resources, 

but there is little detail about the future desired conditions that managers are seeking to 

achieve. The focus of sandbar habitats is on terrestrial deposits, which supply recreational 

camping areas and terrestrial substrates for riparian plant communities. As an aquatic 

habitat resource, sandbars are known to support low-flow-velocity zones within 

recirculating eddies, known commonly as backwaters (Goeking and others, 2003). 

Because of warm temperatures and low velocities found in backwaters, such habitats are 

thought to benefit early life stages of native fish (Goeking and others, 2003), but little 

conclusive data exists to support this hypothesis in Grand Canyon. Further research will 

be required to determine the extent to which sandbars and related habitats play a role, if 

any, in the life history and management of humpback chub. 

Increase Camping Beaches 

According to recent data compiled by USGS and cooperating scientists, open sand 

area preferred by recreational campers has decreased by 55 percent since 1998, with an 

average rate of decline of about 15 percent per year (Kaplinski and others, 2005). The 

only deviation from the overall decline in available campable area has occurred in 

conjunction with BHBF tests in 1996 and 2004. In both cases, the increases in campable 

area were relatively short lived and did not reverse the overall downward trend in 

available campsite area. Reduction in sediment supply related to dam operations, plus the 

lack of periodic sediment-rich flood flows to replenish sediment above the zone of daily 

fluctuating flows, have contributed to the loss of camping area. Additionally, colonization 

of sandbars by native and nonnative vegetation, which is no longer periodically reduced 

or removed by floods, has also contributed to the loss of campable area over time 

(Kearsley and others, 1994; Kaplinski and others, 2005). 

The diminishing availability of campable area, particularly in some of the 

narrower reaches of the river corridor, is an important issue for national park managers 

and recreational river runners. The loss of campable area could increase campsite 

crowding and competition for campsites, which impacts the quality of the recreational 

experience for park visitors (U.S. Department of the Interior, 1995). The primary 

recreation-related management goal of the GCDAMP is to “maintain or improve the 

quality of recreational experiences for users of the Colorado River ecosystem,” and a 

closely related secondary objective is to “increase the size, quality, and distribution of 

camping beaches” (Glen Canyon Dam Adaptive Management Program, 2003). 

Measurable targets tied to these objectives have not yet been defined. 

Cultural Resource Protection 

The preservation of cultural resources, specifically archaeological sites, is closely 

linked to sediment conservation because the majority of sites near the Colorado River 

 12
below Glen Canyon Dam are either situated in or buried by sediment derived from the 

predam river (Fairley and others, 1994; Hereford and others, 1996; Draut and others, 

2005). As the ecosystem has adjusted to postdam hydrologic parameters, there has been 

an overall reduction in sediment being supplied to lower elevation sandbars and a lack of 

periodic high flows to replenish sand deposits at higher elevations above the current daily 

fluctuating flows zone. Meanwhile, uncontrollable natural processes such as precipitation 

and wind remove fine sediment from higher elevation zones. These interrelated factors of 

reduced sediment supply, insufficient sediment availability, and the postdam hydrologic 

regime, coupled with precipitation, wind deflation, and visitor impacts, all contribute to 

the degradation of archaeological sites within the river corridor (Fairley, 2005). The 

general management objective is to mitigate the surface sediment loss and gully erosion 

now occurring at the many archaeological sites in the river corridor. 

Resources, Conditions, and Trends 

The following summarizes the published literature and other current information 

that was discussed by the participants. Some information was so current that it is still 

being prepared for publication. 

Rainbow Trout 

Nonnative fishes have been present in Colorado River for more than 100 years 

(Mueller and Marsh, 2002). The community species composition likely changed through 

time (for example, Woodbury and others, 1959), and it can be anticipated that it will 

continue to change in response to climate, water temperatures, and other factors. Native 

fishes persisted in the presence of nonnative species, but absolute community species 

ratios are unknown because rigorous sampling and estimating for them was not 

conducted. With the closure of Glen Canyon Dam in 1963, the hydrology of the river 

changed dramatically, with more daily flow fluctuations but reduced annual variability 

(Topping and others, 2003). The temperature of the river continues to exhibit an annual 

cycle as it did historically, but, like the flow pattern, the temperature pattern now exhibits 

much less seasonal and annual variability, with a lower average annual temperature 

(Voichick and Wright, 2007). Because of the presence of Glen Canyon Dam, the annual 

peak release temperatures occur in the late fall or winter instead of the summer as they 

did before the dam (Vernieu and others, 2005). These conditions, along with the reduced 

sediment loads, have allowed expansion of rainbow trout (Oncorhynchus mykiss) and 

brown trout (Salmo trutta) populations. 

The rainbow trout population introduced below the dam is currently concentrated 

between the dam and Lees Ferry, although rainbow trout can also be found further 

downstream in Grand Canyon. Using data collected in cooperation with the Arizona 

Game and Fish Department, population trends and condition factors (a measure of 

relative body proportions that indicates individual health) can be correlated with releases 

from Glen Canyon Dam. In 2006, the rainbow trout catch rate was relatively low, but the 

condition of individuals was moderate to high, on average. Catch rates of rainbow trout 

below Glen Canyon Dam have been shown to be correlated with population size 

(Makinster and others, 2007). Between 1997 and 2001, the catch rate for rainbow trout 

 13
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

was usually inversely proportional to condition. In other words, when catch rates were 

high, individual condition was low, and vice versa. Catch rates were proportional to 

annual flow volume; higher flows were generally coincident with higher catch rates. In 

turn, annual flow volume was generally proportional to basin hydrology (L.G. Coggins, 

oral commun., 2007). 

At least two size classes of rainbow trout (50–200 mm and >200 mm) can be 

identified in the reach of the Colorado River between Glen Canyon Dam and Lees Ferry. 

Numbers of rainbow trout diminish with distance downstream, and smaller size classes 

are generally not represented downstream to the mouth of the Little Colorado River; 

larger, presumably older rainbow trout are usually found near the Little Colorado River 

confluence (Gorman and others, 2005; Korman and others, 2005). 

The GCDAMP engaged in experimental removal of rainbow trout and other 

nonnative fish in the vicinity of the Little Colorado River confluence from 2003 through 

2006. This effort removed more than 19,000 rainbow trout. In 2003, rainbow trout 

represented more than 90 percent of the fish captured using electrofishing at night, 

consistent with the findings of Gorman and others (2005). However, the proportion of the 

fish had dropped to less than 10 percent by 2006 (U.S. Geological Survey, unpub. data, 

2007). By contrast, native fish, including humpback chub, were only 10 percent of the 

fish captured in 2003; in 2006, native fish represented more than 60 percent of the fish 

community captured in the Little Colorado River experimental reach (U.S. Geological 

Survey, unpub. data, 2007). While GCMRC and Arizona Game and Fish Department 

scientists have found that rainbow trout declined throughout Marble Canyon (upstream of 

the mechanical removal reach) during this period, the removal of more than 19,000 

rainbow trout seems to have accelerated the population decrease of this species also in the 

vicinity of the Little Colorado River confluence. Other factors that may have caused a 

decrease in population numbers of rainbow trout include increased intraspecific 

competition and warmer mainstem water temperatures. 

Other Nonnative Fishes 

It is likely that current coldwater conditions are generally hindering the 

proliferation of warmwater nonnative fish in the CRE (Moyle and Light, 1996). It is 

known that a suite of warmwater nonnative fishes continues to inhabit the Lower 

Colorado River and tributaries in Grand Canyon (Gloss and Coggins, 2005, table 1; 

Mueller and Marsh, 2002, table 6; Stone and others, 2007). Additional species are 

possible in the future. Warmwater nonnative fishes prey on and compete with native 

Colorado River fish (Minckley and Meffe, 1987; Minckley and Deacon, 1991; Lynch and 

others, 1996; Tyus and Saunders, 2000). 

GCMRC scientists presented a comprehensive overview of current data and 

findings regarding other nonnative Grand Canyon fishes. The 2003–06 experimental 

removal project discussed above contributed to changes in the composition of the fish 

community in the treatment reach, which was located immediately upstream and 

downstream of the mouth of the Little Colorado River. With removal of large numbers of 

rainbow trout, the proportions of other native and nonnative fishes increased during the 

sampling period (L.G. Coggins, oral commun., 2007). 

 14
Below the Little Colorado River, catch rates for striped bass (Morone saxatilis) 

and channel catfish (Ictalurus punctatus) increased with distance below the Little 

Colorado River. The frequency of both of these species in the catch below Diamond 

Creek (river mile 225) increased above the rates within Grand Canyon (Ackerman and 

others, 2006). 

Humpback Chub 

The participants were informed that the current population of adult humpback 

chub (age-4+) is less than 50 percent of what it was as late as 1990, according to the most 

recent capture and modeling information that was available (Coggins and others, 2006). 

This conclusion assumes that the initial 1989 population estimate was accurate. Colder 

water temperatures and predation by and competition with nonnative fishes are likely 

causative factors for the decline. Since 2000, however, the number of adult fish stabilized 

at a new, lower level, which is estimated at 5,000 (Melis and others, 2006). Results of 

even more current data, published after the workshop, indicate that the adult humpback 

chub population is closer to 6,000 (Coggins, 2007). The recent stabilization of the adult 

population could reflect the loss of humpback chub that resided primarily in the 

mainstem since the late 1980s and the inability of mainstem habitat to support successful 

recruitment. The current population of approximately 6,000 adults may represent the 

capacity of the Little Colorado River. These population changes may or may not reflect a 

response of the population to changes in river conditions or actions taken under the 

auspices of the GCDAMP. 

The participants also reviewed information regarding the recruitment abundance 

of humpback chub younger than 4 years old. This segment of the population seems to 

have reached a modern low in 1991. However, numbers of young humpback chub 

increased steadily during the 1990s, returning to approximately late 1980s levels by 2001, 

the most recent year for which these data are available (Coggins, 2007). 

Humpback chub are adapted to warmer water conditions than are currently 

available in the mainstem Colorado River in Grand Canyon (Hamman, 1982; Kaeding 

and Zimmerman, 1983; Clarkson and Childs, 2000). Summer and fall temperatures are 

still colder than historical levels during the same seasons (Voichick and Wright, 2007). 

This remains true in spite of slight increases in the temperature of water releases from the 

dam during the summer and fall of recent years, especially in 2005 when the released 

water temperature was warmer than 16°C in October. Humpback chub appear able to 

survive the current temperatures, at least during adult life stages. Colder summer 

mainstem temperatures may be limiting to the survival of smaller, younger native fishes. 

Adult mainstem survival has been documented by the repeated captures of adult 

humpback chub in the mainstem (for example, Valdez and Ryel, 1995). 

Summer mainstem water temperatures, however, are so low that growth is 

reduced and spawning is almost exclusively limited to the Little Colorado River (Stone 

and Gorman, 2006). Nearly all humpback chub are hatched in and return to this tributary 

for spawning. Following spawning here, most humpback chub spend their life either in 

the tributary or the mainstem immediately upstream and downstream from the tributary 

(Paukert and others, 2006). 

 15
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Aggregations of humpback chub elsewhere in Grand Canyon have been 

documented (Valdez and Ryel, 1995; Valdez and Masslich, 1999; Paukert and others, 

2006). The numbers of individuals in these aggregations are much smaller than the 

number of fish associated with the Little Colorado River, making accurate abundance 

estimates more difficult. The strong site fidelity of the humpback chub captured in these 

aggregations suggests that adult fish, once established, tend to remain at or return to these 

locations (Paukert and others, 2006). The source of young fish for the aggregations found 

downstream of the Little Colorado River is not known⎯whether active spawning occurs 

at the aggregation locations, or humpback chub spawned in the Little Colorado River are 

dispersed downstream to aggregations, or both. 

The aggregation of humpback chub at river mile 30, which is upstream of the 

confluence with the Little Colorado River, occurs in the vicinity of warmer perennial 

springs that emerge from the riverbed (Valdez and Masslich, 1999). Catches of 

humpback chub less than 1 year old increased between 2003 and 2005 (Melis and others, 

2006). Using a bioenergetics model for humpback chub (Petersen and Paukert, 2005), 

scientists estimate that some of the young humpback chub captured in nearshore habitats 

in the vicinity of river mile 30 in 2006 were hatched in 2005 and survived the winter of 

2005–06 in this habitat (Ackerman, 2008). This estimate is being reviewed, but it 

suggests that habitat conditions in this mainstem reach may allow for some spawning and 

larval survival of humpback chub. Winter temperatures are elevated in the reach relative 

to historical predam water temperatures, and the summer and fall mainstem temperatures 

between 2003 and 2006 were elevated over the 12-year running average (Voichick and 

Wright, 2007). In addition to having warmer water temperatures, the river mile 30 reach 

is approximately 20 river miles upstream from the start of the area from which nonnative 

fishes, especially rainbow trout, were removed during 2003–06. The lower rainbow trout 

population in Marble Canyon, which was reduced because of intraspecific competition, 

warmer water temperatures, mechanical removal, or some combination of these, could 

have resulted in reduced predation of and competition with humpback chub; these factors 

may have contributed to the increased captures of young humpback chub in river mile 30 

reach. Natural warming is a confounding factor in determining the impact of mechanical 

removal on native fish. 

Other Native Fishes 

Scientists with GCMRC, Arizona Game and Fish Department, and U.S. Fish and 

Wildlife Service have noted increases in catch rates of not only humpback chub in 2005 

and 2006, but also bluehead sucker (Catostomus discobolus) and flannelmouth sucker 

(Catostomus latipinnis). Catch rates for these two native sucker species increased 

fivefold, especially below the confluence of the Colorado and Little Colorado Rivers (fig. 

1). Examination of length frequency distributions for native fish caught in the Little 

Colorado River removal reach suggests that most of this abundance increase is because of 

increased numbers of juvenile fish. These observations of shifts in native fish length 

frequency distributions support the increases in abundance indicated by the catch-rate 

data and suggest multiple successful recruitment events, particularly for flannelmouth 

sucker. 

 16
Bluehead sucker were so abundant in the Little Colorado River during 2006 that 

they filled hoop nets before they could be pulled and enumerated (Van Haverbeke and 

Stone, 2007). This species has demonstrated elevated catch rates throughout Grand 

Canyon from 2002–06 (R.S. Rogers, Arizona Game and Fish Department, unpub. data, 

2006). The high catch rates for flannelmouth sucker in 2006 remained elevated 

throughout Grand Canyon, and the size structure of the population indicated recent 

successful reproduction (R.S. Rogers, Arizona Game and Fish Department, unpub. data, 

2007). 

Sediment 

Participants were briefed by GCMRC staff and other cooperating sediment 

scientists about the results of sediment studies conducted during the past decade; much of 

this information is summarized by Wright and others (2005). As a means of providing the 

participants with additional information about the recent status of sediment resources and 

BHBF research, GCMRC staff also reviewed information contained in a recently 

published U.S. Geological Survey fact sheet (Melis and others, 2007). 

Studies have demonstrated that sandbars can be rebuilt relatively quickly when 

high flows such as BHBF tests are released from the dam, but that new tributary sand 

inputs do not accumulate in the river channel under typical modified low fluctuating flow 

(MLFF) dam operations as predicted in the 1995 environmental impact statement (U.S. 

Department of Interior, 1995). 

Summary of the 2004 Beach/Habitat-Building Flows Results 

In September 2002, the U.S. Department of the Interior approved implementation 

of new BHBF testing on the basis of a triggering threshold linked to sand inputs from the 

Paria River. The new experimental paradigm focused on evaluating how effectively highflow releases could be used to move new sand up onto shorelines before it was flushed 

downstream. The sand input trigger was to be a high volume of sand deposition from the 

Paria River, which occurs every other year on average. The only BHBF test conducted as 

a result of the Paria sediment trigger occurred in 2004; significant sand inputs to Marble 

Canyon occurred during September–November 2004 and exceeded the sediment trigger. 

A supplemental environmental assessment was prepared and approved in order to permit 

the BHBF test that began on November 21, 2004 (U.S. Department of the Interior, 2002). 

During the 2004 experiment, a net transfer of channel sand into eddies resulted in 

an increase in sandbar total area and volume in the upper half of Marble Canyon, 

approximately river mile 1 through river mile 40 (Topping and others, 2006). Further 

downstream, where sand was less abundant, the experiment resulted in the net transfer of 

sand out of eddies (Topping and others, 2006). 

Results of the 2004 BHBF test confirmed that high flows released under sandenriched conditions can increase the nearshore source areas for windborne sand, leading 

to increases in the rate of sand transported toward some locations in Grand Canyon that 

contain cultural resources (Draut and Rubin, 2006). Increased sand transport by wind and 

backfilling of gullies and deflated areas with aeolian sand can potentially reduce the rate 

of erosion and increase the preservation potential of these sites. Draut and Rubin (2006) 

 17
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

have shown that a measurable increase in sediment transport to some archaeological sites 

is possible when sandbars are created at higher elevations during a BHBF and when the 

sandbars have time to dry out and are retained long enough to be available for reworking 

by wind during the spring windy season. These findings suggest that if more highelevation sandbars could be created and retained for sufficient time periods, it would be 

possible to mitigate some of the surface sediment loss and gully erosion now occurring at 

some archaeological sites in the river corridor that are subject to aeolian processes. 

Scientists also confirmed that substantial increases in total eddy-sandbar area and 

volume are only possible during high-flow releases conducted under the sand-enriched 

conditions that follow large tributary floods (Rubin and others, 2002; Topping and others, 

2006). In the future, more sand than the 800,000 to 1,000,000 metric tons of sand 

available during the 2004 experiment will be required to achieve increases in total eddysandbar area and volume throughout all of Marble and Grand Canyons (Topping and 

others, 2006). 

Because tributary inputs of sand larger than those that preceded the 2004 BHBF 

test are relatively rare, it is not considered feasible to achieve significant systemwide 

rebuilding of sandbars with a single BHBF test. Rather, the most promising method of 

rebuilding sandbars over the long term is by following each average to above-average 

tributary input of sand with a short-duration BHBF test (Topping and others, 2006). 

Under this scenario, each subsequent BHBF test could presumably build upon the 

depositional results of the previous one, potentially resulting in cumulative increases in 

systemwide sandbar area and volume over decadal time scales. However, this strategy is 

only feasible if the intervening powerplant releases do not completely erode the sand 

deposited in sandbars by BHBF tests. Since theory and monitoring data in this system 

have shown that fluctuating flows transport more sand than equivalent-volume steady 

flows, intervening releases with the least amount of fluctuation will have the highest 

probability of maintaining the sandbar building achieved during BHBF tests. Hence, 

there is a long-term need for monitoring sandbar changes over a period of repeated BHBF 

tests under multiple sand enrichment scenarios (perhaps at least over a decade) to answer 

the core science question for sediment (table 1, no. 4). The establishment of specific 

goals for this resource and associated monitoring will be necessary to determine whether 

sandbars are created and maintained where they are most desired by managers. 

Sand Triggering and other Considerations for Future BHBF Tests 

Following the 2004 BHBF, the sand input trigger used for that experiment was 

reevaluated by the GCMRC and the Science Planning Group and revised to include sand 

inputs from the Little Colorado River and other lesser tributaries in addition to the Paria 

River. The revised sediment trigger proposed for future BHBF tests would occur when 

0.5 million metric tons of sand are introduced by the Paria River and retained above river 

mile 30, and an additional “weighted” 0.5 million metric tons of sand are delivered by the 

Paria River, Little Colorado River, or sources that enter the ecosystem annually (late 

summer and fall through early winter) in between these two primary tributaries and 

retained upstream of Diamond Creek (fig. 1). To calculate the weighted input, sand from 

the Paria River is given full value and sand from the Little Colorado River and other 

sources is valued at 50 percent of the actual input. Thus, a BHBF test could be triggered 

with an input of 1.0 to 1.5 million metric tons of sand, depending on how much of the 

 18
sand is derived from the Paria River. The rationale for revising the sand input trigger is 

that it allows experimentation under enriched sand conditions that could occur below 

Marble Canyon from the Little Colorado River during periods when the Paria River 

inputs alone may not equal the earlier trigger, but weights the Paria River inputs over 

downstream inputs to prevent BHBF tests from occurring at times when Marble Canyon 

has not had any annual sand inputs. Under the revised triggering criteria, repeated 

experiments could occur more frequently and would facilitate a more rapid evaluation of 

whether or not cumulative sandbar deposition occurs on a systemwide basis through time. 

In general, the optimal timing for a BHBF test is when the most new tributaryderived sand is available in the system. The rationale for conducting experiments under 

sediment-enriched conditions has been documented in several peer-reviewed outlets, 

including Webb and others (1999), Topping and others (2000), Rubin and Topping 

(2001), Rubin and others (2002), Schmidt and others (2004), Wright and others (2005), 

Hazel and others (2006), Topping and others (2006), and Melis and others (2007). 

Historically, the largest Paria River inputs have occurred during the late-summer and fall 

thunderstorm season. For the Little Colorado River, large inputs may occur during the 

late summer and fall as well as during spring floods. 

The rate at which the tributary-derived sand is exported downstream to Lake 

Mead is dependent on the availability of new sand and releases from the dam. Under 

moderate and higher dam releases, the export rate can be quite high, which may constrain 

the time available for the new sand to be used for BHBF tests (Rubin and others, 2002). 

Most sand in a moderate input is predicted to be lost within days (at discharges >35,000 

cfs), weeks (at discharges of about 25,000 cfs), or months (at discharges of about 15,000 

cfs); however, at discharge rates of 10,000 cfs and less, sand is retained for periods of 

months to years. 

The new sand will only be available for a BHBF if the test is implemented 

promptly following sediment inputs or if dam releases are constrained; however, basin 

hydrology may prohibit low releases. Because of this interaction between the timing of 

tributary inputs and basin hydrology, the optimal timing of BHBF tests will vary from 

year to year. For example, during periods of wet hydrology and high dam releases, when 

export rates are expected to be high, the optimal time to conduct BHBF tests would likely 

be within days or weeks of large tributary inputs, such as during late fall for typical Paria 

inputs. Conversely, during periods of dry hydrology and low-volume dam releases, when 

export rates are expected to be lower, it may be optimal to wait until late in the spring so 

as to accumulate Paria and Little Colorado River sand throughout the input seasons. 

Finally, export rates are dependent on the amount of fluctuation as well as the total 

volume; thus, the amount of fluctuation will affect the amount of sand available and the 

optimal timing of BHBF tests (that is, less fluctuation leads to more retention and thus 

more flexibility in timing BHBF tests). Clearly, the optimal timing for a BHBF in one 

year may not be the same as in another year, but ideally a BHBF test would avoid the 

summer and early fall when the probability of high numbers of juvenile humpback chub 

entering the mainstem is highest. 

Consistent with the 1995 environmental impact statement (U.S. Department of the 

Interior, 1995), as well as BHBF tests undertaken in 1996 and 2004, future tests should 

be conducted in the range of 41,500 to 45,000 cfs, or possibly higher if Lake Powell 

storage is high enough to reach the spillway gate elevations, to promote the most robust 

 19
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

conservation of sand at higher elevations along river banks. Replication of the 2004 peak 

magnitude of 41,500 cfs during future BHBF tests is most likely to support comparative 

analyses to determine whether sandbar habitats can be effectively rebuilt and maintained 

by sand-enriched high flows. 

The concept of replicating the 2004 hydrograph (rising limb, peak, and 

descending limb) was discussed extensively among cooperating sediment scientists at the 

2005 knowledge assessment workshop convened by the GCMRC with stakeholders. The 

2004 test hydrograph was designed on the basis of sandbar simulations for a subset of 

eddies under a scenario of 45,000-cfs peak magnitude and sand concentrations that were 

measured in the postdam era. These outcomes of the simulations and data collected from 

the 1996 BHBF test influenced the choice of 60 hours as the reduced duration for peak 

flow, down from the 168-hour test that occurred in 1996. The 2004 peak magnitude was 

limited to 41,500 cfs because one of the eight units at Glen Canyon Dam was undergoing 

maintenance. Replication of the 2004 hydrograph in a future test is aimed at determining 

whether or not the sandbar-building responses that occurred under the 2004 BHBF test in 

upper Marble Canyon will occur consistently each time a BHBF test is released under 

locally sand-enriched conditions. Replication of the 2004 test hydrograph would also 

allow scientists to evaluate whether there are incremental cumulative benefits to sandbar 

conservation in lower Marble Canyon and Grand Canyon reaches each time sandenriched BHBF tests occur. 

The GCMRC and its science cooperators recently evaluated the limitations and 

benefits of a shorter duration peak at 41,500 cfs, such as one that would last for only 30 

hours. Exact predictions about the outcome of a BHBF test with a shorter duration are not 

possible at this time without field experimentation. Predictability is limited because 

current sediment models have limited success in making such robust predictions; there 

are many factors to consider related to peak-flow duration and peak magnitudes for highflow experiments. While the main recommendation from scientists at present is to use the 

same hydrograph for the next test as was used in 2004, they acknowledge that a peakflow duration of not less than 30 hours would also provide sufficient data collection to 

advance learning about these high releases and sediment dynamics. 

By conservation of mass, flood waves in a wet channel travel downstream at a 

higher velocity than the water (Lighthill and Whitman, 1955). Additionally, the water 

travels much faster than the sand in suspension. Thus, depending on the longitudinal 

distribution of sand in the river, substantial lags may develop between an experimental 

BHBF flood wave and the sand in transport, with the flood wave greatly leading the 

suspended sand. During the 2004 BHBF test, this disparity in travel time between the 

flood wave and the water and new sand input from the Paria River was as much as 27 

hours by the time the flow peak reached Diamond Creek, more that 250 river miles below 

Glen Canyon Dam. During evaluation of the flow and sediment data from the 2004 test, it 

became apparent that once the peak of the test release had moved ahead of the new sand 

supply in upper Marble Canyon, it became another test of the 1996 BHBF, except with 

even less sand available in the downstream reaches owing to continued sand export 

between 1996 and 2004. 

Although the fall 2004 dam releases (5,000- to 10,000-cfs daily range) were very 

effective in limiting downstream sand transport between September and late November 

2004, having the new sand mostly stockpiled in the upper section of Marble Canyon 

 20
meant that the flood wave’s higher velocity took it downstream of the new sand supply 

by the time the flood reached lower Marble Canyon and beyond. As a result, scientists 

now hypothesize that some redistribution of new sand inputs should occur before 

conducting future BHBF tests. The hypothesis to test here is that a more uniformly 

distributed new sand supply will be more evenly transferred to eddy sandbars throughout 

this critical upper Marble Canyon reach as the fast-moving flood wave propagates 

downstream. It is unknown whether such preconditioning of new sand supplies can be 

effectively achieved or not. The 2004 BHBF test followed several months of downstream 

transport under 1996 Record of Decision operations. Some uniform distribution of 

sandbars was observed. If the results from replicating the 2004 experimental BHBF 

hydrograph under more sand-enriched conditions in the spring result in even more 

uniformly distributed sandbars, or deposition progresses farther downriver with 

successive floods as upriver eddies become filled, then this approach may be interpreted 

as being a sustainable strategy for longer term habitat rebuilding and maintenance. 

Discussions 

To clarify the range of proposed management options that could be evaluated 

experimentally, the workshop facilitator described a variety of flow and nonflow 

experimental treatments that had been previously identified by the Science Planning 

Group (appendix B). Examples of flow treatments include steady, fluctuating, and 

beach/habitat-building flows. Consideration was given to how flow treatments affect 

sediment conservation and native fish. Examples of nonflow treatments include 

construction and operation of a temperature control device and continued efforts to 

mechanically remove and control the abundance of nonnative fish. 

Flow Treatments 

Steady Releases 

The participants discussed whether there was any value in recommending steady 

releases from Glen Canyon Dam. Steady releases appear to allow shallow nearshore 

habitats to warm more than the mainstem when exposed to the higher solar radiation 

values available from June to September. They agreed the evidence indicated that the 

most important treatment managers could implement to benefit humpback chub was the 

warming of mainstem nearshore habitats; however, they emphasized the need to control 

predation and competition by nonnative fishes, since warming the water might promote 

the expansion of warmwater nonnative fishes as well. 

Nearshore habitats are usually located between the margin of the mainstem 

current and the shoreline and are typically characterized by low water velocities 

(compared to the mainstem) and reduced turbulent mixing. Nearshore habitats generally 

include low-angle sandy shorelines, talus slopes, tributary mouths, and backwaters 

(usually associated with eddies). 

 21
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

The physical mechanisms controlling the development of nearshore habitats are 

relatively well known. For example, backwater environments are typically formed in 

eddy return-current channels and are partially isolated from mainstem flows by 

reattachment bars. Sediment mass balance and transport data suggest that stabilized dam 

releases may inhibit the daily fluctuation of these types of nearshore environments, 

resulting in increased potential for warming because of the lack of turbulent mixing with 

cold mainstem water. 

While numerous empirical datasets indicate that some nearshore environments, 

especially backwaters, have the potential for warmer water temperatures than the 

mainstem (for example, Arizona Game and Fish Department, 1996; Korman and others, 

2006; Kaplinski, 2006; W.S. Vernieu, U.S. Geological Survey, unpub. data, 2001), there 

are relatively few published studies that definitively link elevated nearshore water 

temperatures to steady flows. The Arizona Game and Fish Department (1996) showed 

that daily mean, minimum, maximum, and diel temperature ranges were significantly 

warmer under steady versus fluctuating flows at four backwater sites near the confluence 

of the Little Colorado River for a 7-day period in the summer of 1994. Korman and 

others (2006) showed similar warming patterns for three nearshore habitat sites during a 

2-month period in fall 2004. Both of these studies, however, cautioned that the effects of 

steady versus fluctuating flows on nearshore water temperatures are highly variable and 

dependent upon several complex, interacting factors, such as the timing of maximum and 

minimum flows, backwater morphology, and ambient meteorological conditions. 

Additionally, recent thermal modeling studies by the GCMRC suggest that release 

volumes may play a more substantial role in mainstem warming than daily flow regimes 

(Anderson and Wright, in press). 

To maximize benefit to native fishes, low-volume releases during the summer 

months would provide the highest available mainstem temperatures (Anderson and 

Wright, in press). In turn, low-volume, steady releases would hypothetically yield 

warmer nearshore water temperatures. Given the volumetric constraints imposed by 

water law and the current state of knowledge on nearshore habitat morphology and 

resultant thermal dynamics, the most readily available tool to stabilize the presence and 

persistence of nearshore habitats and, thus, enhance warming in those environments 

during the summer months is the release of steady flows from Glen Canyon Dam. 

The timing of desired temperature increases was discussed extensively. If the 

primary goal is to promote humpback chub spawning in the mainstem and increased 

larval survival in the mainstem, then efforts to increase mainstem temperatures should be 

initiated in June. If the goal is limited to promoting survival and growth of fish produced 

in the Little Colorado River that are transported into the mainstem of the Colorado River 

by late summer monsoon rain events, then efforts to increase mainstem temperatures 

should be initiated in August. Downstream and nearshore warming also requires elevated 

air temperatures, so reduced flows in late fall (that is, past about mid-October) would not 

be expected to increase water temperature. Workshop participants emphasized the need 

for an aggressive monitoring and control program for nonnative fishes that could benefit 

from warmer water, a point also made by previous review panels (Mueller and others, 

1999; Garrett and others, 2003). 

 22
Fluctuating Releases 

There was little discussion of the effect of increased, load-following flow 

fluctuations during nonsummer months on native fish. Participants recognized that there 

are few, if any, data that suggest that existing fluctuations during nonsummer months 

were adversely impacting native fish. At the same time, they believed that greater 

fluctuations were also unlikely to provide any benefit for native fish. These conversations 

took place in the context of seeking to balance biological and financial considerations, 

because fluctuating releases are used to generate hydropower. However, there are scant 

data available for a definitive conclusion that nonsummer fluctuating flows have no ill 

effects on native fishes in Grand Canyon, and so additional investigation would be 

needed before it could be accepted as true. Although the youngest humpback chub are 6 

months old or older in the winter, and so have some swimming ability, winter can be a 

sensitive season for organisms as they attempt to survive adverse conditions and limited 

food resources. Overwinter survival is a primary factor determining year-class strength 

for most temperate fishes (Garvey and others, 1998). Small changes in growth or 

mortality have been shown to have important impacts on population recruitment in fishes 

(Houde, 1987). Haines and others (1998) showed that Colorado pikeminnow 

(Ptychocheilus lucius) survival was much reduced in a year with high, fluctuating winter 

releases from Flaming Gorge Dam on the Green River, compared to more stable years. 

Therefore, in the absence of more data, it would be premature to conclude that high, 

fluctuating releases from Glen Canyon Dam during the winter months would have 

minimal impact on humpback chub and other native fishes. 

Beach/Habitat-Building Flows 

BHBF tests, common to all of the SPG options, were also considered by 

workshop participants for rebuilding sandbars and related habitats throughout the river 

ecosystem. Given the information presented by sediment experts participating in the 

workshop and owing to the fact that testing of this flow treatment started early in the 

program in 1996, the participants acknowledged that the strategy for future BHBF testing 

and evaluation has evolved further than other experimental treatments such as steady 

flows or operation of a temperature control device. The sediment transport processes 

associated with using short-duration high flows to conserve sand, though complex, are 

easier to study and evaluate over short time periods, compared with treatments aimed at 

the conservation of humpback chub. 

Participants found no evidence that two previous BHBF tests negatively impacted 

native fishes below the dam. They concluded that additional BHBF tests should occur 

following tributary sand enrichment, assuming they can be timed to minimize negative 

effects on native fishes. The tests should be further evaluated to determine whether or not 

they achieve sandbar rebuilding and maintenance in a sustainable manner. Participants 

debated the presumed critical role for rearing of juvenile humpback of backwaters formed 

by sandbars along shorelines. The possible, though unproven, importance of shoreline 

habitats was acknowledged. Clearly, further research will be required to determine the 

extent to which sandbars and related habitats play a role in management of humpback 

chub. 

 23
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

BHBF tests may be of benefit to native fishes because high flows may displace or 

disrupt reproduction of nonnative fish species (Valdez and others, 2001). Springtime 

BHBF tests seem to hold promise for contributing to small-bodied nonnative fish control, 

and would not conflict with summer and fall flow optimization to benefit native fishes. 

Further experimentation would be needed to evaluate the efficacy of this potential 

management tool. 

Use of steady flow tests combined with sand-enriched BHBF tests was also 

thought to support the most favorable flow, temperature, and habitat objectives for 

humpback chub. The participants acknowledged that although this experimental sediment 

strategy was likely to benefit downstream sediment resources and promote rapid learning 

(both objectives of the LTEP EIS), it could also impose significant operating constraints 

for generating hydropower at the dam. 

Nonflow Treatments 

Temperature Control Device 

Another approach that Reclamation is considering to improve river conditions for 

native fishes is the implementation of a temperature control device for Glen Canyon 

Dam. At least two previous scientific review panels have evaluated the potential benefits 

and risks of the temperature control device (Mueller and others, 1999; Garrett and others, 

2003). Current designs call for modification of at least two intake structures on Glen 

Canyon Dam that would allow for the withdrawal of water from the reservoir at higher 

elevations than those currently available, especially during years in which the reservoir is 

relatively high. Water near the surface of the reservoir is exposed to increased solar 

radiation, especially during spring through fall, leading to increased warming of the 

releases (Vernieu and others, 2005). Current modeling results produced by the GCMRC 

indicate that water released through a temperature control device on Glen Canyon Dam 

could be expected to increase release temperatures about 5°C during the summer and fall 

months (Garrett and others, 2003; U.S. Geological Survey, 2006). 

The participants supported construction and testing of a temperature control 

device with the following caveats: the TCD (1) should be designed to maximize 

warmwater releases and (2) must have the ability to release cool water, even in years 

when the reservoir elevation is relatively low. Maximizing release temperatures is 

important because the temperature targets in the Little Colorado River confluence are 

relatively cool and suboptimal for humpback chub reproduction and growth (Hamman, 

1982; Clarkson and Childs, 2000), especially compared to the warmwater temperatures 

that humpback chub populations in the upper Colorado River Basin are exposed to during 

the brief summer season. The participants suggested that the proposed TCD must also 

have the flexibility to release cool water because reducing mainstem water temperatures 

could help to control the abundance of warmwater nonnative fishes. 

The previous reviews of Mueller and others (1999) and Garrett and others (2003) 

emphasized that a TCD could increase existing risks to native fishes. Both reviews noted 

that warmer water was likely to favor not only nonnative fishes, but also invertebrate 

species, including introduced New Zealand mudsnail (Potamopyrgus antipodarum) and a 

 24
range of fish parasites, including anchorworm (Lernaea cyprinacea) and Asian fish 

tapeworm (Bothriocephalus acheilognathi). The review by Mueller and others (1999) 

also anticipated the introduction of whirling disease (Myxosoma cerebralis) below Glen 

Canyon Dam. Whirling disease is caused by an organism that infects young rainbow trout 

and would benefit from warmer water temperatures. Arizona Game and Fish Department 

unpublished data indicate that whirling disease has now been found in very low 

concentrations below the Dam. Workshop participants recommended BHBF tests and 

releases of cool water as tools that might control infestation rates from these organisms as 

well as nonnative fish populations. 

Sediment Augmentation 

Recent studies by Randle and others (2007) determined that importing fine 

sediment into the CRE from source areas upstream of Glen Canyon Dam is technically 

feasible using existing technologies. However, the practicality of sediment augmentation 

remains uncertain owing to factors such as environmental concerns and costs for the 

construction and operation of a sediment delivery system. Given time limitations, there 

were no substantive discussions about how a sediment delivery system could be included 

in future experimental programs. Sediment scientists at the workshop recommended 

determining whether the BHBF (flow-only) strategy was viable before developing 

experimental designs involving sediment augmentation. The biological implications 

associated with importation of silt and clay to manage elevated turbidity in the mainstem 

(presumably to disadvantage sight predators and thereby benefit juvenile native fishes) 

were not discussed during the workshop. 

Nonnative Fishes Control 

All of the Science Planning Group’s experimental options include nonnative fish 

control. The motivation for limiting the population size of nonnative fish below Lees 

Ferry comes from experience in other parts of the Colorado River, where native fish have 

suffered severe declines after the introduction and proliferation of nonnative fish species 

(Minckley and Deacon, 1991; Lentsch and others, 1996). The participants discussed 

several case studies, including the recent and dramatic shift from natives to nonnatives in 

the Green and Yampa Rivers (Bestgen and others, 2006; 2007), as justification for doing 

everything practical to control nonnative fishes in the Colorado River ecosystem. 

Although nonnative fish removal between 2003 and 2006 reduced salmonid 

abundance, especially rainbow trout (U.S. Geological Survey, unpub. data, 2007), 

scientists have not determined whether this benefited native fish. However, on the basis 

of the participants’ knowledge of other ecosystems, they suggested that managers should 

continue to suppress nonnative fish abundance (coldwater and warmwater species) in the 

future rather than allow their numbers to increase. 

The participants explored the value of conducting an experiment to determine 

which factor—the presence of nonnatives or water temperatures—was most likely to 

limit native fish population expansion. For example, the active removal of nonnative 

fishes could be stopped, allowing nonnative fish populations to increase, while water 

temperatures increased because of low reservoir levels, thereby providing a contrast to 

 25
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

the 2003–06 period of experimental mechanical removal when both warmer water and 

nonnative removal were the “treatments.” The participants determined that allowing an 

increase in the population size of rainbow trout in the Little Colorado reach for the 

purpose of experimentation would be inconsistent with the goal of increasing the 

humpback chub population in Grand Canyon (that is, the LTEP EIS purpose and need 

that call for benefits to downstream resources). In this instance, they determined that 

resource conservation should take priority over scientific learning. Control of nonnatives 

has proven difficult in many cases (Minckley and Deacon, 1991; Bestgen and others, 

2007) and given the current threats to humpback chub, the participants concluded that the 

best course of action was to continue to suppress rainbow trout and other nonnative fish, 

especially in the vicinity of the Little Colorado River. Nonnative fish control in the Little 

Colorado River and at its confluence at the mainstem must be considered a priority 

because of the critical importance of the tributary for humpback chub and because of the 

numbers and diversity of nonnative species present there (Stone and others, 2007). 

Similarly, the participants determined that the risk to the humpback chub 

population posed by warmwater nonnative fishes would grow if increased water 

temperatures were to continue, whether as a result of below-average basin hydrology, a 

TCD, or both. They noted that it will be important to increase monitoring of the 

abundance of these species, which will also help inform scientists and managers 

regarding effective control measures (for example, appropriate gear, timing of monitoring 

and removal). Consistent with their discussions regarding rainbow trout, the participants 

agreed that early, consistent monitoring and control of nonnative species is critical 

because reactionary control efforts initiated after nonnative species have proliferated 

often have limited or no success (Bestgen and others, 2007). 

The participants observed that control of fish adapted to cold water, such as 

rainbow trout, will likely be easier than controlling warmwater nonnative fish, because 

the latter, as a group, have greater capacity for explosive population growth when 

favorable conditions exist. Warmwater nonnative fishes also have higher potential for 

habitat overlap with warmwater native fishes, and so they pose a greater risk to natives 

than coldwater species. The risks from warmwater species expansions are formidable and 

warrant a high level of attention in order to support native fish conservation in Grand 

Canyon. The participants observed that nonnative fish control will have to include 

tributary populations if there is to be any reasonable hope of success. 

Humpback Chub Second Population and Translocation 

The participants discussed possible alternatives for spawning locations, such as 

other Grand Canyon tributaries, and the associated impact to the entire population of 

transferring some individuals. They agreed that the best option to pursue was the 

mainstem Colorado River. While translocating young humpback chub from the Little 

Colorado River to other tributaries (for example, Shinumo Creek) may be successful in 

supporting some reproduction and growth, the size and length of these streams suggest 

that they could only support a population of a few hundred fish (Valdez and others, 

2000). The existence of one or more of these populations certainly decreases the risk of 

catastrophic loss; however, multiple small populations would be required to maintain the 

numbers of fish needed to preserve genetic integrity (U.S. Fish and Wildlife Service, 

 26
2002). Current recovery goals for humpback chub recommend that individual populations 

consist of at least 2,100 individuals to maintain a minimum level of genetic diversity 

within each population (U.S. Fish and Wildlife Service, 2002). A review of some of the 

available scientific literature on the subject finds widely varying estimates of the 

population numbers (from dozens to thousands of individuals) necessary to maintain 

genetic diversity in wild vertebrate populations (Franklin and Soulé, 1981; Gilpin and 

Soulé, 1986; Haig and Avise, 1996; Reed and others, 2003). 

Grand Canyon National Park is proposing to move approximately 300 young-ofyear humpback chub from the Little Colorado River to Shinumo Creek (fig. 1; M. Hahn, 

Grand Canyon National Park, oral commun., 2007). The workshop participants generally 

agreed that such translocations were unlikely to cause any important confounding of 

humpback chub monitoring or population modeling. Further, they concluded that such 

translocations could support expansion of the humpback chub population, and that the 

best available review of this topic is the work of Valdez and others (2000), which serves 

as an informed starting point for managers who may wish to conduct translocations as a 

conservation action. 

Humpback Chub Refuge 

The establishment of one or more offsite refuges for humpback chub was not 

discussed by the participants owing to time constraints. However, the participants did 

discuss the value of laboratory studies for contributing to our understanding of the effects 

of various physical parameters, especially temperature, on humpback chub. The 

establishment of a refuge population of humpback chub that was able to successfully 

spawn could supply the fish needed to support such laboratory experiments. 

Increased Mainstem Water Temperatures 

The participants determined that warmer mainstem water temperatures could 

encourage (1) growth of humpback chub hatched and reared in the Little Colorado River 

and (2) increased humpback chub spawning and rearing in the mainstem. These two 

different life-history stages are temporally distinct, and therefore the timing of warmer 

water releases would affect whether one or both of the two life-history stages are 

supported by warmer dam releases. 

Humpback chub hatched and reared in the Little Colorado River spend from 1 to 

16 months residing in this tributary before they are washed by high flows into the 

mainstem Colorado River (Valdez and Ryel, 1995). The high flows that transport these 

young fish out of the tributary occur between July and September in most years 

(Robinson and others, 1998). The participants agreed that the thermal shock of being 

washed from the relatively warm Little Colorado River into the colder Colorado River 

may reduce humpback chub survival in the mainstem (Clarkson and Childs, 2000). 

Therefore, survival of these young fish produced in the Little Colorado River may be 

enhanced by warming mainstem water temperatures between July and September. 

The participants noted that the goal of increased spawning of humpback chub in 

the mainstem Colorado River is consistent with the 1995 biological opinion on the 

operation of Glen Canyon Dam (U.S. Fish and Wildlife Service, 1995) and the 1995 

 27
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

environmental impact statement (U.S. Department of the Interior, 1995). Participants 

agreed that temperature was the most important physical parameter to be addressed to 

increase mainstem spawning. Warmer mainstem temperatures greater than 18°C 

(Hamman, 1982) as early as May or June would likely promote mainstem spawning. 

However, it is unlikely that humpback chub would engage in large-scale mainstem 

spawning with a single year of warmer temperatures. It is more likely that they would 

gradually increase spawning as increasing numbers survived to maturity and were able to 

locate suitable habitats. Mainstem temperatures would need to be warm enough to allow 

feeding to support growth and maintenance of body size as well as warm enough to 

stimulate the maturation of gonads, a necessary precursor to successful spawning. 

As discussed above, warmer temperatures would also favor expansion of 

nonnative fish species (Moyle and Light, 1996). A TCD at Glen Canyon Dam that allows 

for the release of cooler water may inhibit the proliferation of warmwater nonnative fish. 

Effective nonnative fish monitoring to detect changes in distribution or abundance and a 

control program for nonnative fishes are essential. These measures were all 

recommended by workshop participants. 

Workshop Outcomes 

Environmental Triggers Approach 

The experimental research design developed to be consistent with the stated 

purpose and need of the LTEP EIS included the use of environmental cues, or triggers, to 

determine management actions. Specifically, workshop participants recommended the 

continued evaluation of the current flow regimes and associated resource responses in 

water years 2007 and 2008. By 2009, additional data would be available on the effects on 

humpback chub and sand resources of flow and nonflow treatments implemented 

between 2003 and 2008. The flow and nonflow treatments implemented during this 

period included (1) mechanical removal of nonnative trout within treatment and control 

reaches, which resulted in a 90 percent decrease of trout in the treatment reach, (2) at 

least five consecutive summers (2003–07) of dam releases that were warmer than average 

releases from 1988 through 2002, (3) testing during three consecutive years of larger 

winter fluctuating flows, (4) consistent release of modified low fluctuating flows (Record 

of Decision operations) under minimum hydrologic conditions during spring through fall, 

and (5) a fall 2004 test of the beach/habitat-building flows under moderately enriched 

sand supply conditions. 

The environmental triggers approach also included a recommendation for the 

construction and testing of a temperature control device at Glen Canyon Dam not only to 

benefit humpback chub (warm releases), but also to suppress expansion of warmwater 

nonnative fishes (cool releases) during periods of drought when warm releases would 

otherwise be unavoidable. The participants suggested that by 2013 the TCD could either 

be operated to continue warmer releases (in the event that the reservoir has refilled) or 

provide cooler releases. 

From 2009 through 2012, the participants recommended testing summer and fall 

steady releases from the dam for anticipated benefits to native fish. Steady flows might 

 28
warm nearshore habitats, which are hypothesized to be beneficial for survival of young 

humpback chub in the mainstem. Steady flows were also identified as a potential means 

of mitigating the effects of cooler releases in the absence of the TCD. Blocks of 

treatments lasting four or more consecutive years were recommended to test responses in 

all resources, especially in humpback chub, because this species matures on average at 4 

years of age. Implementing treatments in 4-year blocks also provides researchers with 

opportunities to evaluate reproduction and age-1 year-class strength for several years. 

The environmental triggers approach is summarized in table 2 and figure 2, which 

illustrate one example of the timeline and decision points that would be used under the 

environmental trigger approach. 

An important element of the environmental triggers approach requires the 

specification of desired future conditions, or measurable targets, for humpback chub, 

sediment, archaeological sites, camping beaches, and other resources of interest to 

managers. Explicit targets will provide the needed reference points for evaluating the 

effectiveness of treatments and the need to implement additional treatments. Accurate 

monitoring data to assess the status of native and nonnative fish, sediment, and other 

important resources were also critical elements of this strategy. 

The participants discussed the ability of the environmental triggers approach to 

definitely answer the core science questions that were developed and prioritized by the 

managers (table 1). The consensus of the participants was that to fully answer the 

questions, particularly biological questions, would be complicated and could be 

impossible in the 10-year timeframe of the LTEP EIS. Participants reached this 

conclusion because of factors that may confound the interpretation of experimental 

studies, including large hydrologic variability of the upper Colorado River Basin, 

continued introductions of nonnative species, and climate change. Despite such problems, 

the scientists encouraged managers to develop the desired future conditions and pursue an 

adaptive management strategy as the most viable approach for providing resource 

benefits and learning. 

The participants discussed the environmental triggers approach with managers 

after the workshop during a teleconference meeting on April 26, 2007, and through email correspondence. The teleconference discussion between workshop participants and 

managers is summarized in appendix C. 

 29
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

 30

Table 2. Timeline with contingencies for environmental triggers and experimental 

approach. 

Interim Phase, 2007–08: Continued evaluation of resource responses to 

modified low fluctuating flow (MLFF) 

Continue modified low fluctuating flow operations: Monitor native and nonnative fish, 

sediment, and other relevant resource data, and compare changes relative to baseline data 

from Record of Decision operations collected from 1991 through 2002. Compare the 

resource status with desired future conditions (DFCs) to determine Phase I treatments. 

Phase I, 2009–12: Evaluate steady versus fluctuating flows 

1a. Continue MLFF operations: If target resources (humpback chub, sediment, etc.) are 

meeting DFCs, continue MLFF operations. Maintain monitoring and control for 

nonnative fishes. Discontinue MLFF operations if declines in target resources are 

identified. 

1b. Test summer steady flows: If DFCs for sediment and humpback chub resources are 

not met, implement steady flows in summer months (June–August), to test anticipated 

benefits of warming, especially in nearshore habitats, and sediment retention. 

Phase II, 2013–16: Temperature control device (TCD) operational 

2a. Test warm TCD releases: Use a TCD to warm release temperatures if humpback 

chub are in decline. Emphasize warm, steady releases in June–August to encourage 

mainstem spawning, growth, and recruitment. TCD operation will be especially 

important in the event that basin hydrology returns to higher, colder dam releases. If 

warmwater nonnative species increase significantly above previously determined trigger 

levels, then implement cool releases. Cooling could be accomplished with a TCD that 

extracts water from the lower depths of the reservoir. If DFCs for humpback chub are not 

met, continue to operate TCD to warm mainstem water temperatures. Maintain 

monitoring and control for nonnative fishes. If DFCs are not met, consider 

implementation of additional flow and nonflow treatments to benefit humpback chub. 

2b. Test cool TCD releases: If by 2016 the humpback chub population is meeting DFCs, 

which are assumed to include mainstem reproduction, or if populations of nonnative 

fishes significantly increase in the mainstem, discontinue use of TCD and lower release 

temperatures to limit expansion of nonnative fishes, ideally increasing likelihood of new 

humpback chub cohort(s) recruiting to adult population. Implement nonnative fish 

control. 

2c. Relax flow restrictions and warm releases with TCD: If the humpback chub 

population begins to reproduce in the mainstem and nonnative fish populations are not 

considered a threat, relax flow restrictions somewhat to allow for hydropower loadfollowing operations. Reinstate flow restrictions if mainstem humpback chub population 

begins to decline or undesirable decreases in other resources are detected as by ongoing 

monitoring activities. 
Continue 

MLFF (and BHBF) 

DFCs met 

Evaluate DFCs of HBC following 2009–12 

Figure 2. Simplified illustration of a decision tree based on humpback chub responses to treatments compared t

desired future conditions. DFCs are desired future conditions; BHBF is beach/habitat-building flows test; HBC is his modified low fluctuating flow; TCD is temperature control device.

Environmental Triggers 1 Environmental Triggers 2 Environmenta

Determine 

HBC DFCs 

and 

evaluate 

HBC status 

relative to 

DFCs 

following 

2003–06 

Evaluate DFCs of HBC following 2007–08 

DFCs met DFCs not met 

Continue MLFF (and BHBF) 

Test steady flows (and BHBF) and 

DFCs warm water not met 

Test steady flows (and BHBF) 

Evaluate DFCs of HBC following 2009–12 

DFCs met DFCs not met 

Year: 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 

Begin building TCD 

Operate/test TCD

Have nonnatives increased? Test MLFF (and BHBF) and warm water Test steady flow(and BHBF) and warm water 

Interim Phase I Phase II

 31
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Comparison of Environmental Triggers Approach to Science Planning Group 

Options 

The participants had insufficient time to fully evaluate all of the specific elements 

of the four experimental approaches (SPG options A, A′, B, and C, see below) that were 

developed by the GCDAMP Science Planning Group in 2005–06. However, participants 

suggested that managers consider further evaluation of the SPG options by comparing 

each of them to the environmental triggers approach developed during the workshop. 

Such comparisons may be useful for determining where overlap exists between the 

various options. One commonality among all four SPG options is that they depend on 

assessments of environmental criteria, much like the environmental triggers approach. 

SPG Option A and A′

The participants agreed that there were no specific data suggesting that increased 

fluctuations in winter and spring would be detrimental to humpback chub, although, as 

noted above (p. 23), overwinter habitat conditions are critical for many fishes. However, 

increased fluctuations at these times would promote more sediment transport and erosion 

of sandbars (Rubin and others, 2002; Wright and others, 2005). Because increased 

fluctuations in summer and fall are potentially a limiting influence on both nearshore 

warming and edge habitat stability, these fluctuations were hypothesized to be counter to 

the needs of humpback chub reproduction and rearing in the main channel. Steady flows 

were not identified as part of SPG option A and A', representing a major point of contrast 

with the environmental triggers approach, which provided for steady flows testing to 

benefit humpback chub and sediment conservation. 

SPG Option B 

The participants partially concurred with the implementation of steady flows 

during the summer and fall seasons that were advocated in this option. The participants 

and reviewers of this document identified limited scientific justification for implementing 

and testing steady flows in winter and spring to promote the early life-history needs of 

native fish, but there are very limited data on this subject in Grand Canyon. Sediment 

would be conserved during extended periods of steady flows, compared with other SPG 

options or the environmental triggers approach. The sediment experts in the workshop 

stated that steady flows throughout the year would produce the most learning and benefit 

for sediment resources and would likely be achieved in the shortest amount of time. 

SPG Option C 

The participants determined that the timing of steady flows proposed in this 

option—during September and October—would provide stable habitat and possible 

warming only for a short portion of the early life history of juvenile humpback chub. 

There was wide agreement that SPG option C would provide greater benefit to humpback 

chub if it included steady flow tests earlier in the summer, such as in June or perhaps 

mid-July through October. A possible environmental trigger for steady flows during the 

 32
month of August is included in this alternative, but the criteria for such an operational 

decision had not yet been identified by managers. 

Treatment Elements Common to the Environmental Triggers and SPG Options 

All of the SPG experimental options included the testing of a temperature control 

device, which would presumably entail retrofitting of at least two of the eight Glen 

Canyon Dam units. However, details about how the TCD would be designed and tested 

were not clearly articulated in the SPG options. Owing to time limitations, workshop 

participants were not able to identify a detailed approach for long-term testing and 

evaluation of a TCD. 

Mechanical removal of nonnative fish is a common element included in all the 

options, including the environmental triggers approach. The workshop participants 

concluded that some advantage would be gained through continued mechanical control of 

nonnative fishes; although, they noted that the control of warmwater species is likely to 

be much more difficult than the relatively successful mechanical removal of salmonids. 

Continued BHBF testing was common to all the options, including the 

environmental triggers approach, as a means of rebuilding sandbars and related habitats 

throughout the river ecosystem. Because BHBF tests have been conducted since 1996, 

the strategy for future BHBF testing and evaluation is further evolved than other 

experimental treatments such as steady flows or operation of a temperature control 

device. 

Conclusions 

The purpose of the LTEP EIS is to increase scientific understanding and protect 

important resources in the Colorado River ecosystem downstream of Glen Canyon Dam. 

Workshop participants identified a variety of treatments and an experimental approach 

that meets the purpose and need of the LTEP EIS. Their conclusions are supported by the 

best available science and years of professional experience studying the Colorado River 

and other regulated North American rivers. Many of their conclusions were consistent 

with two previous scientific reviews of a proposed temperature control device. Elements 

of the recommended approach, many of which were identified in one or more of the four 

options developed by the GCDAMP Science Planning Group, include 

1. releasing steady flows from Glen Canyon Dam, which is the most readily available 

tool to enhance warming in nearshore environments during the summer months; 

2. implementing periodic beach/habitat-building flows during sand-enriched conditions 

following tributary flooding; 

3. building and testing a temperature control device that can both increase and decrease 

water temperatures according to need as indicated by monitoring of aquatic 

organisms (Warmer water is likely to benefit humpback chub spawning and 

recruitment in the mainstem and cooler water could be used to disadvantage 

nonnative fish, nonnative invertebrates, and fish parasites.); 

 33
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

4. continuing mechanical removal of both coldwater and warmwater nonnative fish near 

the confluence of the Little Colorado and Colorado Rivers; and 

5. translocating humpback chub from the Little Colorado River to other Grand Canyon 

tributaries with suitable habitat. 

The participants recognized that the Colorado River ecosystem below Glen 

Canyon Dam is a large, complex environment that is difficult to study and understand. 

However, they believe a great deal of information is available to inform future 

management decisions related to the operation of Glen Canyon Dam. Existing 

knowledge—particularly with regard to humpback chub and sediment transport—is 

sufficient to propose an approach supporting the purpose and need of the LTEP EIS, that 

is, the environmental triggers approach. 

The environmental triggers approach relies on measurable resource goals as the 

basis for determining the experimental treatments that should be implemented. Currently, 

measurable resource goals and clear criteria for meeting goals are not available for CRE 

resources. However, participants asserted that such measurable goals are needed for 

managers to determine whether or when to test summer steady flows, for example. The 

use of environmental triggers to initiate management treatments is common to all SPG 

experimental options. Similar criteria would presumably need to be determined in 

advance of any of the other SPG options that promote either steady flow or TCD tests. 

The participants agreed that they may be able to assist managers with an evaluation of the 

status of various resources, but insisted that it was not appropriate for scientists to define 

triggering criteria that would be fundamentally tied to nonscientific values and resource 

management objectives for the ecosystem. Ultimately, the specific environmental 

triggering criteria will be up to managers to determine, presumably on the basis of 

desired future conditions for downstream resources. 

The environmental triggers approach calls for the continued evaluation of flow 

regimes for water years 2007 and 2008. Continuing treatments would provide data on the 

effects on humpback chub of flow and nonflow treatments implemented between 2003 

and 2008. Following assessment of ongoing treatments, the environmental triggers 

approach proposes 4 years (2009–12) of summer−fall steady flows testing, if resource 

goals for humpback chub and sediment have not been reached as the result of current 

operations. From 2013–16, the approach recommends testing of a temperature control 

device capable of releasing both warm and cool water. The participants were very 

concerned about the potential for the expansion of species adapted to warm water and 

strongly recommended increasing monitoring efforts for these species, echoing the 

concerns of previous scientific review panels (Mueller and others, 1999; Garrett and 

others, 2003). Participants agreed that early, consistent monitoring and control of 

nonnative species is critical to successful nonnative fish management. If humpback chub 

begin to reproduce in the mainstem and nonnative fishes are not considered a threat, the 

approach calls for some relaxation of flow restrictions to allow for hydropower loadfollowing operations. However, the impact of winter fluctuations on native fishes is little 

studied in Grand Canyon, and managers should not assume that they would have no 

impact on native fishes. 

Two days of deliberations were insufficient for all resources to be fully 

considered, so the workshop participants focused, at Reclamation’s request, on humpback 

chub and sediment. Flow recommendations for Glen Canyon Dam must take into account 

 34
a complex suite of natural, social, economic, and political factors. Compounding this 

complexity is the likelihood that the Colorado River Basin will be experiencing higher 

than historical temperatures and lower than historical runoff in the years and decades to 

come (Seager and others, 2007), which would affect its capacity to serve all needs and 

values. Any long-term planning should take the warmer, drier forecast into account. The 

participants focused on natural concerns; full consideration of societal values was beyond 

the scope of the workshop. Further consideration should be given to how the approach 

could be modified to consider other resources, including hydropower production. The 

participants expressed the hope that the insights resulting from the workshop will inform 

future experimentation in the Glen Canyon Dam Adaptive Management Program. 

 35
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

References

Ackerman, M.W., 2008, 2006 native fish monitoring activities in the Colorado River, 

Grand Canyon: annual report. Annual report to the U.S. Geological Survey Grand 

Canyon Monitoring and Research Center, Flagstaff, Ariz.: Flagstaff, Ariz., SWCA 

Environmental Consultants, agreement no. 04WRAG0011. 

Ackerman, M.W., Ward, D., Hunt, T., Rogers, S., Van Haverbeke, D.R., and Morgan, A., 

2006, 2006 Grand Canyon long-term fish monitoring Colorado River, Diamond Creek 

to Lake Mead: 2006 annual report. Annual report to the U.S. Geological Survey Grand 

Canyon Monitoring and Research Center, Flagstaff, Ariz., cooperative agreement no. 

04WRAG0011. 

Anderson, C.R., and Wright, S.A., in press, Development and application of a water 

temperature model for the Colorado River ecosystem below Glen Canyon Dam, 

Arizona, in American Institute of Hydrology Annual Meeting and International 

Conference, Reno, Nev., April 22–25, 2007 [Proceedings]. 

Arizona Game and Fish Department, 1996, Ecology of Grand Canyon backwaters: 

Flagstaff, Ariz., report to Bureau of Reclamation, Glen Canyon Environmental Studies, 

Cooperative Agreement 9-FC-40-07940, 155 p. 

Bestgen, K.R., Zelasko, K.A., Compton, R.I., and Chart, T., 2006, Response of the Green 

River fish community to changes in flow and temperature regimes from Flaming Gorge 

Dam since 1996 based on sampling conducted from 2002 to 2004: final report, 

Colorado River Recovery Implementation Program Project Number 115, Larval Fish 

Laboratory Contribution 144, 129 p. 

Bestgen, K.R., Zelasko, K.A., Wilcox, C.T., 2007, Non-native fish removal in the Green 

River, Lodore and Whirlpool Canyons, 2002–2006, and fish community response to 

altered flow and temperature regimes, and non-native fish expansion: final report, 

Colorado River Recovery Implementation Program Project Number 115, Larval Fish 

Laboratory Contribution 149, 84 p. 

Clarkson, R.W., and Childs, M.R., 2000, Temperature effects of hypolimnial-release 

dams on the early life stages of Colorado River Basin big-river fishes: Copeia, v. 2000, 

no. 2, p. 402–412. 

Coggins, L.G., Jr., 2007, Abundance trends and status of the Little Colorado River 

population of humpback chub: An update considering 1989−2006 data: U.S. 

Geological Survey Open-File Report 2007-1402, 53 p. 

Coggins, L.G., Jr., Pine, W.E., III, Walters, C.J., Van Haverbeke, D.R., Ward, D., and 

Johnstone, H.C., 2006, Abundance trends and status of the Little Colorado River 

population of humpback chub: North American Journal of Fisheries Management, v. 

26, p. 233–245. 

Douglas, M.R., and Douglas, M.E., 2007, Genetic structure of humpback chub Gila 

cypha and roundtail chub G. robusta in the Colorado River Ecosystem: Report to 

 36
Grand Canyon Monitoring and Research Center, contract 051884, Colorado State 

University Project 5-31614, Ft. Collins, Colo. 

Draut, A.E., and Rubin, D.M., 2006, Measurements of wind, aeolian sand transport, and 

precipitation in the Colorado River corridor, Grand Canyon, Arizona–January 2005 to 

January 2006: U.S. Geological Survey Open-File Report 2006-1188, 88 p., 

http://pubs.usgs.gov/of/2006/1188/, accessed February 22, 2008. 

Draut, A.E., Rubin, D.M., Dierker, J.L., Fairley, H.C., Griffiths, R.E., Hazel, J.E., Jr., 

Hunter, R.E., Kohl, K., Leap, L.M., Nials, F.L., Topping, D.J., and Yeatts, M., 2005, 

Sedimentology and stratigraphy of the Palisades, Lower Comanche, and Arroyo 

Grande areas of the Colorado River corridor, Grand Canyon, Arizona: U.S. Geological 

Survey Scientific Investigations Report 2005-5072, 68 p., 

http://pubs.usgs.gov/sir/2005/5072/, accessed February 21, 2008. 

Fairley, H.C., 2005, Cultural resources in the Colorado River Corridor, in Gloss, S.P., 

Lovich, J.E., and Melis, T.S., eds., The state of the Colorado River ecosystem in Grand 

Canyon: U.S. Geological Survey Circular 1282, p. 177–192. 

Fairley, H.C., Bungart, P.W., Coder, C.M. , Huffman, J., Samples, T.L., and Balsom, 

J.R., 1994, The Grand Canyon river corridor survey project: archaeological survey 

along the Colorado River between Glen Canyon Dam and Separation Canyon: 

Flagstaff, Ariz., report prepared in cooperation with the Bureau of Reclamation Glen 

Canyon Environmental Studies Program and Grand Canyon National Park, cooperative 

agreement no. 9AA-40-07920. 

Federal Register, 2006, Notice of intent to prepare an environmental impact statement on 

the adoption of a long-term experimental plan for the operation of Glen Canyon Dam, 

v. 71, no. 238 (December 12, 2006), p. 74556–74558. 

Franklin, O.H., and Soulé, M.E., 1981, Conservation and Evolution: Cambridge, 

England, Cambridge University Press, 327 p. 

Garrett, L.D., Baron, J., Dale, V., Gunderson, L.H., Howard, A., Hulse, D., Kitchell, J., 

Loomis, J., Palmer, M., Parker, R., Robertson, D., Schwartz, D., and Watkins, J., 2003, 

Evaluating a Glen Canyon Dam temperature control device to enhance native fish 

habitat in the Colorado River: A risk assessment by Adaptive Management Program 

Science Advisors: Prepared for the Glen Canyon Dam Adaptive Management Program 

and the Grand Canyon Monitoring and Research Center, Flagstaff, Ariz. 

Garvey, J.E., Wright, R.A., and Stein, R.A., 1998, Overwinter growth and survival of 

age-0 largemouth bass (Micropterus salmoides): revisiting the role of size: Canadian 

Journal of Fisheries and Aquatic Sciences, v. 55, p. 2412−2424. 

Gilpin, M.E. and Soulé, M.E., 1986. Minimum viable populations: Processes of species 

extinction, in Soulé, M.E., ed., Conservation Biology: Sunderland, Mass., Sinauer 

Associates, Inc., p. 19–34. 

Glen Canyon Dam Adaptive Management Program, 2003, Final draft information needs, 

November 7, 2002, updated June 25, 2003, with recommendations from the Ad Hoc 

Committee on What’s in and Out of the Strategic Plan (AHCIO), 

 37
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

http://www.usbr.gov/uc/rm/amp/amwg/mtgs/03aug13/Attach_09a.pdf, accessed 

February 21, 2008. 

Gloss, S.P., and Coggins, L.C., Jr., 2005, Fishes of Grand Canyon, in Gloss, S.P., Lovich, 

J.E., and Melis, T.S., eds., The State of the Colorado River ecosystem in Grand 

Canyon: U.S. Geological Survey Circular 1282, p. 33–56. 

Gloss, S.P., Lovich, J.L, and Melis, T.S., eds., 2005, The state of the Colorado River 

ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, 220 p. 

Goeking, S.A., Schmidt, J.C., and Webb, M.K., 2003, Spatial and temporal trends in the 

size and number of backwaters between 1935 and 2000, Marble and Grand Canyons, 

Arizona: Final report from Utah State University to U.S. Geological Survey Grand 

Canyon Monitoring and Research Center, Flagstaff, Ariz. 

Gorman, O.T., Bramblett, R.G., Hervin, R.M., Van Haverbeke, D.R., and Stone, D.M., 

2005, Distribution and abundance of native and non-native fishes of the Colorado River 

ecosystem of Grand Canyon, Arizona, in Brouder, M.J., Springer, C.L., and Leon, S.C., 

eds., The Lower Colorado River: restoring natural function and native fish within a 

modified riverine environment: Proceedings of two symposia and workshops, Las 

Vegas, Nev., July 8–9, 1998, and July 13–14, 1999, U.S. Fish and Wildlife Service, 

Southwest Region, Albuquerque, N. Mex., p. 78–94. 

Haig, S.M., and Avise, J.C., 1996, Avian conservation genetics, in Avise, J.C., and 

Hamrick, J.L., eds., Conservation genetics: case histories from nature: New York, 

Chapman and Hall, p.160–189. 

Haines, G.B., Beyers, D.W., and Modde, T., 1998, Estimation of winter survival, 

movement and dispersal of young Colorado squawfish in the Green River, Utah, 

Recovery Program Project 36: Final report prepared for the Recovery Implementation 

Program for Endangered Fish Species in the Upper Colorado River Basin, U.S. Fish 

and Wildlife Service, Denver, Colo. 

Hamman, R.L., 1982, Spawning and culture of humpback chub: Progressive Fish 

Culturist, v. 44, no. 4, p. 213–216. 

Hazel, J.E., Jr., Topping, D.J., Schmidt, J.C., and Kaplinski, M., 2006, Influence of a dam 

on fine-sediment storage in a canyon river: Journal of Geophysical Research, Earth 

Surface, v. 111, F01025, doi: 10.1029/2004JF000193, 2006, 16 p. 

Hereford, R., Thompson, K.S., Burke, K.J., and Fairley, H.C., 1996, Tributary debris fans 

and the late Holocene alluvial chronology of the Colorado River, eastern Grand 

Canyon, Arizona: Geological Society of America Bulletin, v. 108, no. 1, p. 3–19. 

Houde, E.D., 1987, Fish early life dynamics and recruitment variability: American 

Fisheries Society Symposium, v. 2, p. 29−38. 

Kaeding, L.R., and Zimmerman, M.A., 1983, Life history and ecology of the humpback 

chub in the Little Colorado and Colorado Rivers of the Grand Canyon: Transactions of 

the American Fisheries Society, v. 112, p. 557–594. 

 38
Kaplinski, M., 2006, Near shore water temperature data: August 12 to November 14, 

2005: Data delivery report submitted to U.S. Geological Survey Grand Canyon 

Monitoring and Research Center, Flagstaff, Ariz., 23 p. 

Kaplinski, M., Behan, J., Hazel, J.E., Jr., Parnell, R.A., and Fairley, H.C., 2005, 

Recreational values and campsites in the Colorado River ecosystem, in Gloss, S.P., 

Lovich, J.E., and Melis, T.S., eds., The state of the Colorado River ecosystem in Grand 

Canyon: U.S. Geological Survey Circular 1282, p. 193–205. 

Kearsley, L.H., Schmidt, J.C., and Warren, K.D., 1994, Effects of Glen Canyon Dam on 

Colorado River sand deposits used as campsites in Grand Canyon National Park, USA: 

Regulated Rivers, v. 9, p. 137–149. 

Korman, J., Kaplinski, M., and Buszowski, J., 2006, Effects of air and mainstem water 

temperatures, hydraulic isolation, and fluctuating flows from Glen Canyon Dam on 

water temperatures in nearshore and backwater environments in the Colorado River in 

Grand Canyon: Final Report to U.S. Geological Survey Grand Canyon Monitoring and 

Research Center, Flagstaff, Ariz., 57 p. 

Korman, J.M., Kaplinski, M., Hazel, J.E., III, and Melis, T.S., 2005, Effects of 

experimental fluctuating flows from Glen Canyon Dam in 2003 and 2004 of the early 

life history stages of rainbow trout in the Colorado River: Final report to U.S. 

Geological Survey Grand Canyon Monitoring and Research Center, Flagstaff, Ariz., 

cooperative agreement no. 04WRAG0006 

http://www.gcmrc.gov/library/reports/biological/Fish_studies/Ecometric/Korman2005.

pdf, accessed April 22, 2008. 

Lentsch, L.D., Muth, R.T., Thompson, P.D., Hoskins, B.G., and Crowl, T.A., 1996, 

Options for selective control of nonnative fishes in the upper Colorado River Basin: 

Salt Lake City, Utah, Utah Division of Wildlife Resources Publication 96-14. 

Lighthill, M.J., and Whitman, G.B., 1955, On Kinematics waves, I. Flood movement in 

long rivers: Proceedings of the Royal Society A, v. 229, p. 281−316. 

Lovich, J., and Melis, T.S., 2005, Lessons from 10 years of adaptive management in the 

Grand Canyon, in Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., The state of the 

Colorado River ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 

207–220. 

Lynch, L.D., Muth, R.T., Thompson, P.D., Hoskins, B.G., and Crowl, T.A., 1996, 

Options for selective control of nonnative fishes in the upper Colorado River Basin: 

Salt Lake City, Utah, Utah Division of Wildlife Resources Publication 96-14. 

Mankinster, A.S., Rogers, R.S., Persons, W.R., 2007, Status of Lee’s Ferry trout fishery: 

2006 annual report: Annual report to the U.S. Geological Survey Grand Canyon 

Monitoring and Research Center, Flagstaff, Ariz.: Phoenix, Ariz., Arizona Game and 

Fish Department. 

Melis, T.S., Martell, S.J.D., Coggins, L.G., Jr., Pine, W.E., III, and Andersen, M.E., 

2006, Adaptive management of the Colorado River ecosystem below Glen Canyon 

Dam, Arizona: using science and modeling to resolve uncertainty in river management 

in Specialty Summer Conference on Adaptive Management of Water Resources, 

 39
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Missoula, Mont., 2006, CD-ROM Proceedings (ISBN 1-882132-71-8): Middleburg, 

Va., American Water Resources Association. 

Melis, T.S., Topping, D.J., Rubin, D.M., and Wright, S.A., 2007, Sediment research 

supports sandbar restoration: U.S. Geological Survey Fact Sheet 2007-3020, 4 p. 

Minckley, W.L., and Deacon, J.E., eds., 1991, Battle against extinction: Tuscon, Ariz., 

University of Arizona Press, 517 p. 

Minckley, W.L., and Meffe, G.K., 1987, Differential selection for native fishes by 

flooding in streams of the arid American Southwest, in Matthews, W.J., and Heines, 

D.C., eds., Ecology and evolution of North American stream fish communities: 

Norman, Okla., University of Oklahoma Press, p. 93–104. 

Moyle, P.B., and Light, T., 1996, Fish invasions in California: do abiotic factors 

determine success?: Ecology, v. 77, no. 6, p. 1666–1670. 

Mueller, G.A., and Marsh, P.C., 2002, Lost, a desert river and its native fishes: a 

historical perspective of the lower Colorado River: Fort Collins, Colo., U.S. Geological 

Survey Information and Technology Report USGS/BRD/ITR 2002-0010, 69 p. 

Mueller, G., Walters, C., Holden, P.B., Walker, P.G., Landye, J., Johnson, B., 1999, 

Scientific review of the Glen Canyon Dam modifications to control downstream 

temperatures plan and draft environmental assessment, January, 1999, and supporting 

documentation: Prepared for the Bureau of Reclamation, Upper Colorado Region, Salt 

Lake City, Utah. 

Paukert, C.P., Coggins, L.G., Jr., and Flaccus, C.E., 2006, Distribution and movement of 

humpback chub in the Colorado River, Grand Canyon, based on recaptures: 

Transactions of the American Fisheries Society, v. 135, p. 539–544. 

Petersen, J.E., and Paukert, C.P., 2005. Development of a bioenergetics model for 

humpback chub and evaluation of water temperature changes in the Grand Canyon, 

Colorado River: Transactions of the American Fisheries Society, v. 134, p. 960–974. 

Randle, T.J., Lyons, J.K., Christensen, R.J., and Stephen, R.D., 2007, Colorado River 

ecosystem sediment augmentation appraisal engineering report: Denver, Colo., Bureau 

of Reclamation, Technical Service Center, Sedimentation and River Hydraulics Group. 

Reed, D.H., O’Grady, J.J., Brook, B.W., Ballou, J.D., and Frankham, R, 2003, Estimates 

of minimum viable population sizes for vertebrates and factors influencing those 

estimates: Biological Conservation, v. 113, p. 23–34. 

Robinson, A.T., Clarkson, R.W., and Forrest, R.E., 1998, Dispersal of larval fishes in a 

regulated river tributary: Transactions of American Fisheries Society, v. 127, p. 772–

786. 

Rubin, D.M., Nelson, J. and Topping, D.J., 1998. Relation of inversely graded deposits to 

suspended sediment grain-size evolution during the 1996 flood experiment in Grand 

Canyon: Geology, v. 26, no. 2, p. 99−102. 

Rubin, D.M., and Topping, D.J., 2001, Quantifying the relative importance of flow 

regulation and grain size regulation of suspended sediment transport α and tracking 

changes in grain size of bed sediment β: Water Resources Research, v. 37, no. 1, p. 

 40
133–146, http://www.gcmrc.gov/library/reports/physical/Fine_Sed/Rubin2001.pdf, 

accessed February 21, 2008. 

Rubin, D.M., Topping, D.J., Schmidt, J.C., Hazel, J., Kaplinski, M., and Melis, T.S., 

2002, Recent sediment studies refute Glen Canyon Dam hypothesis: EOS, 

Transactions, American Geophysical Union, v. 83, no. 25, p. 273, 277–278,

http://www.gcmrc.gov/library/reports/physical/Fine_Sed/Rubin2002.pdf, accessed 

February 21, 2008.

Schmidt, J.C., Topping, D.J., Grams, P.E., and Hazel, J.E., Jr., 2004, System-wide 

changes in the distribution of fine sediment in the Colorado River corridor between 

Glen Canyon Dam and Bright Angel Creek, Arizona: Grand Canyon Monitoring and 

Research Center final report, cooperative agreement no. 1425-98-FC-40-22640, 

http://www.gcmrc.gov/library/reports/physical/Fine_Sed/Schmidt2004.pdf, accessed 

February 22, 2008. 

Seager, R., Ting, M., Held, I., Kushnir, Y., Lu, J., Vecchi, G., Huang, H.-P., Harnik, N., 

Leetmaa, A., Lau, N.-C., Li, C., Velez, J., and Naik, N., 2007, Model projections of an 

imminent transition to a more arid climate in southwestern North America: Science, v. 

316, p. 1181–1184. 

Stone, D.M., and Gorman, O.T., 2006, Ontogenesis of endangered humpback chub (Gila 

cypha) in the Little Colorado River, Arizona: American Midland Naturalist, v. 155, p. 

123–135. 

Stone, D.M., Van Haverbeke, D.R., Ward, D.L., Hunt, T.A., 2007, Dispersal of nonnative 

fishes and parasites in the intermittent Little Colorado River, Arizona: The 

Southwestern Naturalist, v. 52, no. 1, p. 130–137. 

Topping, D.J., Rubin, D.M., Nelson, J.M., Kinzel, P.J., and Corson, I.C., 2000, Colorado 

River sediment transport: Part 1: natural sediment supply limitation and the influence 

of Glen Canyon Dam: Water Resources Research, v. 36, no. 2, p. 515–542. 

Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., Melis, T.S., Wright, S.A., 

Kaplinski, M., Draut, A.E., and Breedlove, M.J., 2006, Comparison of sedimenttransport and bar-response results from the 1996 and 2004 controlled-flood 

experiments on the Colorado River in Grand Canyon, in Federal Inter-Agency 

Sedimentation Conference, 8th, Reno, Nev., 2006, CD-ROM Proceedings (ISBN 0-

9779007-1-1). 

Topping, D.J., Schmidt, J.C., and Vierra, L.E., Jr., 2003, Computation and analysis of the 

instantaneous-discharge record for the Colorado River at Lees Ferry, Arizona, May 8, 

1921, through September 30, 2000: U.S. Geological Survey Professional Paper 1677, 

118 p. 

Tyus, H.M, and Saunders, J.F., III, 2000, Nonnative fish control and endangered fish 

recovery: lessons from the Colorado River: Fisheries, v. 9, p. 17–24. 

U.S. Department of the Interior, 1995, Operation of Glen Canyon Dam Final 

Environmental Impact Statement, Colorado River Storage Project, Coconino, Arizona: 

Salt Lake City, Utah, Bureau of Reclamation, Upper Colorado Regional Office, 337 p. 

 41
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

U.S. Department of the Interior, 2002, Proposed experimental release from Glen Canyon 

Dam and removal of nonnative fish: environmental assessment: Salt Lake City, Utah, 

Bureau of Reclamation, Upper Colorado River Region, 112 p., appendices. 

U.S. Fish and Wildlife Service, 1995, Final Biological Opinion: Operation of Glen 

Canyon Dam as the modified low fluctuating flow alternative of the Final 

Environmental Impact Statement operation of Glen Canyon Dam (2-21-93-F-167): 

Albuquerque, N. Mex., U.S. Fish and Wildlife Service, 56 p. 

U.S. Fish and Wildlife Service, 2002, Humpback chub (Gila cypha) recovery goals: 

amendment and supplement to the Humpback Chub Recovery Plan: Denver, Colo., 

U.S. Fish and Wildlife Service, Mountain-Prairie Region (6). 

U.S. Geological Survey, 2006, Assessment of the estimated effects of four experimental 

options on resources below Glen Canyon Dam: Flagstaff, Ariz., Grand Canyon 

Monitoring and Research Center, Southwest Biological Science Center. 

Valdez, R.A., Carothers, S.W., Douglas, M.E., Douglas, M., Ryel, R.J., Bestgen, K.R., 

and Wegner, D.L., 2000, Research and implementation plan for establishing a second 

population of humpback chub in Grand Canyon: Final Report to the Grand Canyon 

Monitoring and Research Center, 80 p. 

Valdez, R.A., Hoffnagle, T.L., McIvor, C.C., McKinney, T., and Leibfried, W.C., 2001, 

Effects of a test flood on fishes of the Colorado River in Grand Canyon, Arizona: 

Ecological Applications, v. 11, no. 3, p. 686–700. 

Valdez, R.A., and Masslich, W.J., 1999, Evidence of reproduction by humpback chub in 

a warm spring of the Colorado River in Grand Canyon, Arizona: The Southwestern 

Naturalist, v. 44, no. 3, p. 384–387. 

Valdez, R.A., and Ryel, R.J., 1995, Life history and ecology of humpback chub (Gila 

cypha) in the Colorado River, Grand Canyon, Arizona. Final report to the Bureau of 

Reclamation, Salt Lake City, Utah, contract no. 0-CS-40-09110: Logan, Utah, 

BIO/WEST Report, Inc. 

Van Haverbeke, D.R., and Stone D.M., 2007, Stock assessment and fisheries monitoring 

activities in the Little Colorado River within Grand Canyon during 2006: report to the 

U.S. Geological Survey Grand Canyon Monitoring and Research Center, Flagstaff, 

Ariz.: Flagstaff, Ariz., U.S. Fish and Wildlife Service, interagency acquisition no. 01-

3022-R1009. 

Vernieu, W.S., Hueftle, S.J., and Gloss, S.P., 2005, Water quality in Lake Powell and the 

Colorado River, in Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., The state of the 

Colorado River ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 

69–85. 

Voichick, N., and Wright, S.A., 2007, Water temperature data for the Colorado River and 

tributaries between Glen Canyon Dam and Spencer Canyon, northeastern Arizona, 

1988–2005: U.S. Geological Survey Data Series 251, 24 p., 

http://pubs.usgs.gov/ds/2007/251/ds-251.pdf, accessed February 21, 2008. 

 42
Walters, C.J., Korman, J., Stevens, L.E., and Gold, B.D., 2000, Ecosystem modeling for 

evaluation of adaptive management policies in the Grand Canyon: Conservation 

Ecology, v. 4, p. 1–65. 

Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., eds., 1999, The controlled 

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

Monograph Series, v. 110, 367 p. 

Woodbury, A.M., Flowers, S., Lindsay, D.W., Durrant, S.D., Dean, N.K., Grundmann, 

A.W., Crook, J.R., Behle, W.H., Higgins, H.G., Smith, G.R., Musser, G.G., McDonald, 

D.B., 1959, Ecological studies of the flora and fauna in Glen Canyon: Anthropological 

Papers of the University of Utah, no. 40 (Glen Canyon Series no. 7), Dibble, C.E., 

editor, University of Utah Press, Salt Lake City, 226 p. 

Wright, S.A., Melis, T.S., Topping, D.J. and Rubin, D.M., 2005, Influence of Glen 

Canyon Dam operations on downstream sand resources of the Colorado River in Grand 

Canyon, in Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., The state of the Colorado 

River ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 17–31.

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Appendix A. Workshop Participants and Attendees

Workshop Participants 

Kevin Bestgen, Ph.D., Director, Larval Fish Laboratory, Department of Fishery and 

Wildlife Biology, Colorado State University 

Mike Bradford, Ph.D., Research Scientist, Freshwater Ecosystems Section, Fisheries 

and Oceans Canada, Cooperative Resource Management Institute based at Simon Fraser 

University, Canada 

Lewis G. Coggins, Jr., Fishery Biologist, U.S. Geological Survey, Southwest Biological 

Science Center, Grand Canyon Monitoring and Research Center 

David L. Garrett, Ph.D., Executive Director of Glen Canyon Dam Adaptive 

Management Program Science Advisors, M3 Research 

Theodore A. Kennedy, Ph.D., Aquatic Ecologist, U.S. Geological Survey, Southwest 

Biological Science Center, Grand Canyon Monitoring and Research Center 

Theodore S. Melis, Ph.D., Physical Scientist, U.S. Geological Survey, Southwest 

Biological Science Center, Grand Canyon Monitoring and Research Center 

Randall Peterson, Environmental Resources Division Manager, Upper Colorado 

Region, Bureau of Reclamation 

William E. Pine III, Ph.D., Assistant Professor, Department of Fisheries and Aquatic 

Sciences, University of Florida 

Roger Pulwarty, Ph.D., Director, National Integrated Drought Information System 

Physical Scientist (Climatologist), National Oceanic and Atmospheric Administration, Physical 

Sciences Division 

Dale M. Robertson, Ph.D., Research Hydrologist, Wisconsin Water Science Center; 

Glen Canyon Dam Adaptive Management Program Science Advisor 

David J. Topping, Ph.D., Research Hydrologist, U.S. Geological Survey, Southwest 

Biological Science Center, Grand Canyon Monitoring and Research Center 

Harold M. Tyus, Ph.D., Senior Research Associate, Center for Limnology, Cooperative 

Institute for Research in Environmental Studies, University of Colorado; Glen Canyon 

Dam Adaptive Management Program Science Advisor 

Richard A. Valdez, Ph.D., Senior Aquatic Biologist, SWCA Environmental Consultants 

Carl Walters, Ph.D., Professor, Fisheries Centre, University of British Columbia 

Scott A. Wright, Ph.D., Research Hydrologist, U.S. Geological Survey, California 

Water Science Center 

 44
GCMRC Scientists and Cooperating Scientists in Attendance 

Matthew E. Andersen, U.S. Geological Survey, Southwest Biological Science Center, 

Grand Canyon Monitoring and Research Center. 

Craig Anderson, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

Glenn Bennett, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

Amy Draut, Ph.D., U.S. Geological Survey, Marine Geology Team. 

Helen C. Fairley, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

A. Elizabeth Fuller, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

Dan Gwinn, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

John F. Hamill, U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center. 

Josh Korman (Workshop Facilitator), Ecometric Research, Inc., Vancouver, British 

Columbia, Canada. 

David Rubin, Ph.D., U.S. Geological Survey, Marine Geology Team. 

William S. Vernieu, U.S. Geological Survey, Southwest Biological Science Center, 

Grand Canyon Monitoring and Research Center. 

LTEP EIS Cooperators and other Interested Parties in Attendance 

Jan Balsom, Grand Canyon National Park. 

Charley Bulletts, Southern Piaute Consortium. 

Kelly Burke, Grand Canyon Wildlands Council. 

Wayne Cook, Western Area Power Administration. 

Cole Crocker-Bedford, Grand Canyon National Park. 

Norman Henderson, National Park Service. 

Leslie James, Colorado River Energy Distributors Association. 

Rick Johnson, Grand Canyon Trust. 

Glen Knowles, U.S. Fish and Wildlife Service. 

Dennis Kubly, Bureau of Reclamation. 

Andrew Markinster, Arizona Game and Fish Department. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

 46

Steve Martin, Grand Canyon National Park. 

Ken McMullen, Grand Canyon National Park. 

Don Ostler, Upper Colorado River Commission. 

Clayton Palmer, Western Area Power Administration. 

Heather Patno, Bureau of Reclamation. 

R. Scott Rogers, Arizona Game and Fish Department. 

Tom Ryan, Bureau of Reclamation. 

Sam Spiller, U.S. Fish and Wildlife Service. 

Mark Steffen, Federation of Flyfishers. 

Bill Werner, Arizona Department of Water Resources. 

Mike Yeatts, Hopi Tribe.
Appendix B. Flow and Nonflow Treatments Associated with Various Experimental 

Planning Group Options and Environmental Triggers Approach. Summary matrix of flow and nonflow treatments that scientists and managers have identified as possible 

Canyon long-term experimental strategies 

Flow or nonflow treatment 

Treatment description 

Potential range of variable 

Workshop environmental triggers strategy1

Science Planning Group option A 

Science Planning Group option A variation 

Science Planning Grooption B 

Flow 

Increased daily flow fluctuations 

No flow fluctuations to 20,000 cfs/day 

No Yes (increased 

by 50 to 66% in winter months and by 25% in summer months) 

Yes (increased by 25 to 66% in all months except April and May) 

No 

Flow Stable flows 

Stable flows from 0 to 12 months/year 

Yes, either (a) Jun. 1, or (b) Jul. 15 through mid-Oct. (2009−12)2 

No No Yes, (tests of 4

8, and 12 months) 

Flow 

Beach/habitat-building flows 

BHBF frequency between 1-time test and every year 

Yes, winter/spring under sand triggering3

Yes, as tests under sand triggering 

Yes, as tests under sediment input triggering 

Yes, as tests under sand triggering 

Flow 

Alternative ramping rates 

Ramping rates from 0 cfs/hr (steady flow) to 5,000 cfs/hr 

No4 Yes (hourly 

downramping rate increased 100% in all months) 

Yes (hourly downramping rate increased 100% in Apr.–Oct. and 167% in Nov.–Mar.) 

No 

Nonflow 

Temperature control device 

TCD construction, with releases from 9−22 °C 

Yes5 Yes Yes Yes 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Flow or nonflow treatment 

Treatment description 

Potential range of variable 

Workshop environmental triggers strategy1

Science Planning Group option A 

Science Planning Group option A variation 

Science Planning Grooption B 

Nonflow 

Control of nonnative coldwater fish 

Reduction of nonnative coldwater fish from 0 to ~ 95% 

Yes, ongoing and within control reach 

Yes, as needed Yes, as needed Yes, as needed 

Nonflow 

Control of nonnative warmwater fish 

Control of nonnative warmwater fish from 0 to unknown level of reduction 

Yes, with enhanced monitoring and to the degree determined possible6 

Yes, as needed, with R&D starting in 2007 

Yes, as needed, with R&D starting in 2007 

Yes, as neededwith R&D starting in 200

Nonflow 

Humpback chub disease/parasite research 

Unknown Yes Yes Yes Yes 

Nonflow 

Humpback chub translocation 

Translocation from 0 to 5 tributaries 

Yes7 Yes Yes No 

Nonflow 

Humpback chub refuge(s) 

Use of 0 to 2 refuges 

N/A Yes Yes Possibly 

Nonflow 

Humpback chub population augmentation planning 

Unknown 

N/A9

Yes, planning efforts toward implementation, as needed 

Yes, planning efforts and implementation No 

 48
Flow or 

nonflow treatment 

Treatment description 

Potential range of variable 

Workshop environmental triggers strategy1

Science Planning Group option A 

Science Planning Group option A variation 

Science Planning Grooption B 

Flow and nonflow 

Mini-field experiments1

0

Unknown No11 Yes Possibly Yes 

Experimental design 

Factorial, reverse or forward titration 

Forward titration 

with min. 4-yr treatments 

Reverse titration Reverse titration Factorial 

1Environmental triggers approach. This option was described as the best combination of learning and resource protection by the sci

in the April 2007 workshop. The participants noted a recent increase in chub recruitment that is coincident with warmer water temp

from lower Lake Powell elevations, and the mechanical predator removal program. The goal of this option is to continue some of tto have lead to resource improvement while maintaining flexibility for uncertain future events. Some additional alternatives were d

summary represents what participants believe is the best alternative. The name is taken from the fact that the participants described 

responsive to environmental changes. For example, if basin hydrology increased, increasing the level of Lake Powell and thereby ltemperatures, the participants would favor responding to that variable by offering more steady flows beginning about the time of thfavor humpback chub and other native fishes. Another example is that if multiple years of warmwater releases were observed to be warm water-adapted nonnative fishes, then the participants would recommend releasing cooler water. This is also the primary reasthat part of the TCD design effort include development of an engineering option that allows for releasing cooler water. In the latter trigger indicating this action would be an increase in warmwater nonnative fishes. 

2The participants recommended that warmer temperature water be released to encourage survival, growth, and spawning of humpb

of the warmer water was dependent on the resource response desired. If managers wish to encourage survival and growth of humpb

the LCR, mainstem temperatures should be increased beginning about July 15, at the time that these fish are washed from the LCR 

during flooding events. If managers want to encourage mainstem spawning of humpback chub, mainstem warming would need to oJune 1. In the absence of a temperature control device, the primary means for warming the mainstem, at least in shallow nearshore 

flow fluctuations, so this treatment is recommended. 

3The participants favored the use of beach/habitat-building flows as a tool both for conserving sediment and cultural resources, and 

shallower nearshore and backwater environments in the mainstem. The warmer water found in such habitats, especially after the suthought to be very beneficial to humpback chub, based on laboratory and field observations of this species. The overall significanchumpback chub recruitment is currently unknown⎯especially in the case of LCR recruitment. 

4The participants did not identify any ecological or scientific benefit, whether for learning or resource protection, associated with im

larger flow fluctuations relative to the core science questions provided by the managers. 

5The participants thought that increased release temperatures provided by a TCD could be of great benefit to humpback chub. They 

importance of having a cool temperature release device as a component of the TCD. This importance is associated with the increas

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

 50

warmwater fishes as predators on and competitors with native fishes. If cool releases were available as a management tool, they co

control of nonnative fishes. 

6The participants found that the efforts to control rainbow trout and associated nonnatives (2003−06) had been relatively successfu

continued suppression of nonnatives was warranted because this is a less expensive or risky alternative to letting this populations rproposed for a full experimental option with block treatments. They were concerned, however, that control of warmwater nonnativmore difficult than control of coldwater nonnative fishes. To address this risk, the participants recommended increased efforts to m

and to develop effective control methods, both of which will require appropriate gear types and protocols. 

7In their discussions, the participants assumed that the National Park Service would proceed with translocation of humpback chub f

Colorado River to other tributaries in Grand Canyon National Park. The participants thought that this was a potentially useful efforhumpback chub distribution in Grand Canyon, thereby decreasing the risk from a catastrophic loss. The participants thought that huor more tributaries would support the Grand Canyon population by reducing the risk of catastrophic loss, but did not expect that a saggregation, as called for in the 1995 Biological Opinion, could be successfully established in a tributary alone. They thought that 

would be necessary to expansion/establishment of a second Grand Canyon humpback chub spawning aggregation. Participants also 

belief that a TCD would likely be necessary to ensure long-term sustainability of a second spawning aggregation in the mainstem. 

8For option C: Ancillary projects not considered part of the main experiment; implementation decision includes consideration of co

experiment. 

9The workshop participants did not specifically address the need for offchannel rearing and augmentation of humpback chub. They 

current analysis that the Grand Canyon humpback chub population is generally stable at this time. 

10Mini experiments are short-term field experiments that do not confound main experimental treatment effects. For option C: These 

considered undefined concepts and would be incorporated if defined and not in conflict with the main experiment. 

11The workshop participants were wary of the results of tests conducted in the field for short periods of time (termed “mini field ex

observed that antecedent conditions will be very important to organisms, so tests must be temporally separated to allow for comparconditions. They also observed that humpback chub do not reproduce until approximately their fourth year of life and that the first particularly sensitive to environmental conditions, so it is important that experimental conditions thought to favor humpback chub 

years or more to identify impacts to more than one year class of humpback chub. Alternatively, the invited science workshop particfavorably of the value of laboratory experiments as one tool to help resolve questions about the response of aquatic organisms to en

conditions, including water temperature and habitat stability.
Appendix C. Summary of Post-Workshop Telephone Conference 

Call (April 26, 2007)

It was clear at the end of the workshop that managers involved with developing 

the environmental impact statement for a long-term experimental plan of operation for 

Glen Canyon Dam would require more clarification from the participants about how the 

environmental triggers approach they proposed could be implemented. During a postworkshop teleconference between managers and scientists that took place on April 26, 

2007, participants attempted to clarify their proposal by answering three questions about 

the triggers. 

Managers’ triggering question 1⎯If (Lake Powell) reservoir releases continued to 

be warm after 2009, would participants still recommend steady flow tests during 

the summers of 2009–12 (presumably on the basis that such steady flows were 

designed to warm habitats)? 

The participants recommended the continued evaluation in 2008 and 2009 of the 

biological responses of humpback chub to experimental treatments implemented in 2003–

06, including mechanical removal of nonnative fishes and warming dam releases. The 

workshop participants and the USGS Grand Canyon Monitoring and Research Center are 

operating under the assumption that no flow-regimen changes can be implemented until 

2009, given the constraints of the Annual Operating Plan, and environmental compliance 

activities (that is, compliance with the National Environmental Policy Act) that would 

have to accompany any changes. If this is correct, the first summer in which steady flows 

could be implemented is 2009. It was anticipated that the modified low fluctuating flow 

(MLFF) would be the continuing flow regime in the summers of 2007 and 2008. This 

was why the participants recommended initiation of a multiyear treatment of steady flow 

testing beginning in summer 2009. Steady flows were deemed to be a means of 

continuing downstream warming in nearshore habitats, if dam releases turned colder 

again without a temperature control device in place. However, steady flows under 

continued warm releases could be expected to provide further benefit for native fishes, 

while also providing a learning opportunity. For example, scientists could learn how 

much of a limiting factor the MLFF alternative had been (if at all) on humpback chub 

reproduction and rearing in the mainstem during the previous several years (2003–08), 

given the recent naturally warmer dam releases. 

The summer releases of 2003–06 provided testing of the effects of warm releases 

with fluctuations (the MLFF release schedule), and, based on the constraints noted above, 

MLFF releases will likely continue in 2007 and 2008. The apparent resource responses to 

those conditions have been, and will continue to be, documented and evaluated annually 

by scientists. Managers will presumably assess these annual resource updates and 

compare responses to management objectives in making a recommendation by spring 

2009 whether or not to implement a multiyear treatment of steady flow testing. There has 

been minimal testing of warm, steady flows, especially during the summer months, with 

the exception of the summer of 2000. The workshop participants observed that summer 

steady flow testing was likely to benefit both native fish and sediment conservation 

between at least July and October (and perhaps even more so starting in June). Steady 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

flows that began in June could be expected to not only increase survival of humpback 

chub produced in the Little Colorado River, but also may encourage additional mainstem 

spawning and rearing. In short, a multiyear treatment of steady, warm summer flows has 

not been tested; these flows can be expected to provide resource benefits and learning 

opportunities, and the participants suggest that such flows be tested for a minimum of 

four consecutive years at the first available opportunity. This suggestion seems to be in 

line with the stated purpose and need of the long-term experimental plan (LTEP) 

environmental impact statement (EIS). 

A return to fluctuating flows could also be warranted if nonnative fish monitoring 

indicates that warmwater nonnatives are increasing and likely to explode in abundance. 

Participants acknowledged that managers may be justified if they decided to forego 

steady flow testing in 2009 altogether under continued natural warmer 

releases⎯particularly if priority resources had responded in ways that had met their 

objectives between 2003 and 2008. Hence, a “stay the course” policy beyond 2008 may 

be appropriate on the basis of the adaptive management response to updated resource 

conditions, as determined through monitoring and modeling. The same approach could be 

used for sediment resources and steady flows. This approach is advocated by workshop 

participants as in keeping with the spirit of adaptive ecosystem assessment and 

management. 

Obviously, value-based issues related to both resource benefit and learning must 

be considered in deciding to implement future steady flow tests over multiyear periods, 

and the participants did not believe they could provide further input on this topic without 

clearer articulation of resource objectives (desired future conditions) from the managers. 

Managers’ triggering question 2⎯If the TCDs were not built and [Lake Powell] 

reservoir releases returned to colder temperatures in 2013, would the participants 

recommend continuing steady flows to warm humpback chub habitats or allow 

cool releases and MLFF as a contrasting treatment? 

Cold dam releases with MLFF fluctuations were applied to the Colorado River ecosystem 

almost continuously between 1991 and 2002, with the exception of 2000, when the low 

summer steady flow test was implemented. Resource responses (especially relating to 

humpback chub and other native fish) were observed, recorded, evaluated, and published. 

If managers believed that replication of such operations carried out during this time (a 

period coincident with declining humpback chub population) would be of value⎯perhaps 

to document that such conditions do not favor humpback chub⎯then additional replicate 

testing of cold releases and MLFF may be warranted. The participants did not believe 

that managers would support such replication, believing instead that learning 

opportunities with this treatment appear limited. They spoke favorably of learning 

opportunities, but not to the detriment of resources, so participants generally agreed with 

a strategy for releasing steady summer and fall flows (to promote warmer nearshore 

habitats) to benefit humpback chub until warmer releases could be achieved through use 

of a TCD (a device that they strongly recommended be built and tested, but with the 

ability to release cooler water if naturally warm releases persisted under protracted 

drought). 

 52
The participants could not identify known detrimental effects to humpback chub 

from continued release of MLFF in late fall through early spring months, but saw no 

evidence that such diurnal fluctuations provided benefit to native fishes or other 

downstream resources, either. They did acknowledge that fluctuating flows are known to 

increase sediment losses from the ecosystem and may limit the effectiveness of future 

BHBF tests to rebuild and maintain sandbar habitats by depleting the system of sediment. 

The workshop participants emphasized the importance to native fishes, especially 

humpback chub, of warm water and so identified that steady summer to fall releases 

known to warm downstream, nearshore habitats would be particularly important to 

implement over multiple years as a test if the TCD were not built. They expressed little 

belief or hope that a second humpback chub spawning aggregation in the mainstem could 

be established or maintained without a TCD. 

Managers’ triggering question 3⎯If humpback chub responses were positive 

during any of these block-type treatments, then would participants recommend 

continuing the treatment or changing the treatment as planned in the scientists' 

proposed schedule? 

The workshop participants favored taking advantage of learning opportunities whenever 

possible, but not to the detriment of resources, especially the endangered humpback chub. 

They felt strongly that enough aspects of the fish’s life history in Grand Canyon are 

known that some recommendations can be made. This seems to be an especially 

important consideration to observe until such time that humpback chub status meets or 

exceeds management objectives, which is yet to be fully documented. The participants 

noted that, in the presence of warmer water and control of nonnative fishes, the response 

of humpback chub was encouraging, although an increase of the population had not yet 

occurred, and the second spawning aggregation called for in the 1995 Biological Opinion 

had not yet been established. The workshop participants recognized the need for more 

specific management goals to direct scientific recommendations. As applied to this 

question, this means that a “positive” response is not quantified, and so a quantified 

response to the question is difficult to provide. However, if the block treatment approach 

can be implemented without negative impacts to the resources, then the learning that can 

be achieved is desirable. Participants also acknowledged that the much hoped for “causeeffect” answers that may be of critical interest to some managers may not be possible to 

produce in the complicated, noncontrolled experimental setting found in the Colorado 

River ecosystem.

A major recommendation from the workshop participants to managers was to do 

as much as possible in the near term to clearly identify (prior to experimentation) (1) 

desired future conditions (with an objective method for evaluating alternative 

management treatments), (2) models that will be used to evaluate ecosystem resource 

responses as new data become available (such as continued use of age structure markrecapture estimates, but also other shorter term methods), and (3) a clear suite of 

proposed treatments along with definite limits on how they could be implemented and a 

rigorous monitoring program for providing managers with frequent resource updates 

(particularly for use in evaluating possible responses of warmwater nonnative fish under 

warmer and more stable habitat conditions, if tested). The participants also favored 

 53
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

micro- and mesoscale experiments that would shed additional light on predator-prey 

interactions, and temperature, flow, and sediment effects on both native and nonnative 

species. Many of the inferences about the effects of the dam on humpback chub and other 

native species are from lab studies, and this mode of learning could be highlighted more 

strongly as an alternative if the goal of humpback chub conservation is to take precedence 

over ecosystem manipulation. 

 54
Appendix D. Participants Abbreviated Curricula Vitae or 

Biographies 

Kevin Bestgen, Ph.D. 

Director 

Larval Fish Laboratory 

Department of Fishery and Wildlife Biology 

Colorado State University 

Education 

Ph.D., 1997, Fishery and Wildlife Biology, Colorado State University 

M.S., 1985, Fishery and Wildlife Biology, Colorado State University 

B.A., 1981, Biology, Saint Cloud State University, Minnesota 

Current Research 

Current research includes investigations of dispersal, survival, population abundance, and 

recruitment patterns of endangered cypriniform fishes in the Colorado River system. 

Other interests include effects of river regulation on aquatic biota, fish screening and 

passage evaluations, longitudinal gradient analysis of stream biota, stream fish 

community ecology, taxonomy and biology of larval fish, and long-term monitoring of 

stream fish communities. Most of my work is at the interface of ecology and 

management, particularly related to endangered fishes. 

Recent Publications 

Bestgen, K.R., Zelasko, K. A., Compton, R. I., and Chart T., in press, Survival, condition, 

habitat use, and predation on stocked bonytail in the Green River, Colorado and Utah: 

Southwestern Naturalist. 

Johnson, B.M., Martinez, P.J., Hawkins, J.A., and Bestgen, K.R., in press, Ranking 

relative predatory threats by nonnative fishes in the Yampa River, Colorado via 

bioenergetics modeling: North American Journal Fisheries Management. 

Walford, C.D., and Bestgen K.R., in press, Establishment of Iowa darter Etheostoma 

exile in the Yampa River, Colorado: Southwestern Naturalist. 

Olden, J.D., Poff, N.L., and Bestgen, K.R., 2008, Trait synergisms and the rarity, 

extirpation, and extinction risk of native fishes in the Lower Colorado River Basin: 

Ecology, v. 89, no. 3, p. 847–856. 

Bestgen. K.R., 2008, Effects of water temperature on growth of razorback sucker larvae: 

Western North American Naturalist, v. 68, no. 1, p. 15–20. 

 55
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Michael James Bradford, Ph.D.

Research Scientist 

Freshwater Ecosystems Section, Fisheries and Oceans Canada 

Cooperative Resource Management Institute, Simon Fraser University 

Education 

Ph.D., 1991, McGill University, Montreal, QC 

M.S., 1984, Biology, Simon Fraser University, Vancouver, B.C. 

B.S., 1980, Biology, Simon Fraser University, Vancouver, B.C. 

Current Research 

Current research activities include risk assessment and risk management frameworks for 

fish habitat management, effects of flow regulation on stream ecosystems and salmonid 

fishes, conservation of threatened salmon populations, and ecology of juvenile chinook 

salmon in the Fraser and Yukon Rivers. 

Recent Publications 

Cleary, J.S., M.J. Bradford and D. Janz, in preparation, Seasonal and spatial variation in 

lipid and triacylglycerol levels in juvenile chinook salmon (Oncorhynchus 

tshawytscha) from the Bridge River, British Columbia, Can. J . Fish. Aquat. Sci. 

Bradford, M.J., von Finster, A., and Milligan, P., 2008, Life history, habitat, and the 

production of chinook salmon from the upper Yukon Basin, in C. Kruger and C 

Zimmerman, eds., Sustainability of the Arctic-Yukon-Kuskokwim salmon fisheries: 

Amer. Fish. Soc. 

Bradford, M.J., and Heinonen, J.S., 2008, Low flows, instream flow needs and fish 

ecology: Canadian Water Resources Journal.

Decker, A.S., Bradford, M.J., and Higgins, P.S., 2008, Rate of biotic colonization 

following flow restoration below a diversion dam in the Bridge River, British 

Columbia. Rivers: Research and Management. 

Bradford, M.J., Duncan, J., and Jang, J.W., 2008, Downstream migrations of juvenile 

salmon and other fishes in the upper Yukon River: Arctic. 

 56
Lewis G. Coggins, Jr., Ph.D. 

Fishery Biologist 

U.S. Geological Survey 

Southwest Biological Science Center 

Grand Canyon Monitoring and Research Center 

Education 

Ph.D., 2008, Fisheries and Aquatic Science, University of Florida 

M.S., 1997, Fisheries, University of Alaska, Fairbanks 

B.S., 1990, Ecology and Evolutionary Biology, University of Arizona 

Current Research 

Current research activities include design of experimental management policies and 

monitoring protocols that yield information on system behavior useful to inform 

successful management of fisheries, with particular interest in developing novel 

quantitative approaches to both predict and observe resource response to management 

actions. 

Recent Publications 

Coggins, L.G., Jr., Catalano, M.J., Allen, M.S., Pine, W.E., III, and Walters, C.J., 2007, 

Effects of cryptic mortality and the hidden costs of using length limits in fishery 

management: Fish and Fisheries, v. 8, p. 196–210. 

Coggins, L.G., Jr., Pine, W.E., III, Walters, C.J., and Martell, S.J.D., 2006, Age 

structured mark recapture analysis (ASMR): a VPA based model for analyzing age 

structured capture-recapture Data: North American Journal of Fisheries Management, 

v. 26, p. 201–205. 

Coggins, L.G., Jr., Pine, W.E., III, Walters, C.J., Van Haverbeke, D.R., Ward, D., and 

Johnstone, H.C., 2006, Abundance trends and status of the Little Colorado River 

population of Humpback Chub: North American Journal of Fisheries Management, v. 

26, p. 233–245. 

Paukert, C.P., Coggins, L.G., Jr, and Flaccus, C.E., 2006, Distribution and movement of 

humpback chub in the Colorado River, Grand Canyon, based on recaptures: 

Transactions of the American Fisheries Society, v. 135, p. 539–544. 

Yard, M.D., Bennett, G.E., Mietz, S.N., Coggins, L.G., Jr., Stevens, L.E., Hueftle, S., 

Blinn, D.W., 2005, Influence of topographic complexity on solar insolation estimates 

for the Colorado River, Grand Canyon, AZ: Ecological Modelling, v. 183, p. 157–172. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

David L. Garrett, Ph.D. 

Executive Director, Glen Canyon Dam Adaptive Management Program Science Advisors 

Principal, M3 Research 

Biography 

Dr. Garrett’s academic training is in biology, forestry, economics, and systems 

science. He has conducted and managed natural resource science programs in every 

major ecological region of the United States. As a U.S. Department of Agriculture 

scientist and science center leader, he began applying systems and management science 

approaches to forest restoration and wood energy programs in the Southeast, North 

Central, and New England regions. 

During the last 25 years, he has focused on ecosystem approaches to forest 

resource management, forest restoration science, and riverine ecosystem restoration 

science and monitoring in the Rocky Mountain, Southwest, Pacific Northwest and Alaska 

regions. These efforts have included landscape-level terrestrial and riverine restoration 

assessments, improved restoration treatment methods and prescriptions, system models to 

evaluate restoration research and monitoring, restoration management applications for 

watersheds 5,000 to 30,000 acres in size, and applied science and management programs 

for terrestrial landscapes 100,000 to 200,000 acre in size and a variety riparian and 

riverine systems. 

Dr. Garrett has focused on Southwest forest and riverine ecosystem restoration 

during the past 10 years. In 1996, he was requested by the Secretary of the Interior to 

work collaboratively with stakeholders and scientists to develop a management and 

science program that would advance understanding of downstream resource impacts 

stemming from the operation of Glen Canyon Dam. This effort resulted in the Glen 

Canyon Dam Adaptive Management Program. 

As a dean at Northern Arizona University, Dr. Garrett developed the university’s 

College of Ecosystem Science, where he worked with the faculty to create a wide range 

of programs to advance ecosystem approaches to forest and watershed riparian science 

and management. Programs in terrestrial and riparian restoration science and teaching 

continue to provide national leadership today. 

During the last 5 years, as principal of M3 Research, a restoration science 

consulting firm, Dr. Garrett has focused on both forest and river restoration programs. He 

directs the Science Advisory Board that advises the Glen Canyon Dam Adaptive 

Management Program on science and management restoration programs in the Colorado 

River. Through M3 Research, Dr. Garrett works with county, State, and Federal leaders 

in New Mexico, Arizona and, Colorado on issues of forest and riparian-area restoration. 

Most recently, Dr. Garrett has completed forest restoration assessments on the Kiabab 

and Apache Sitgreaves National Forests, Ariz., and Lincoln National Forest, N. Mex. 

Dr. Garrett has authored more than 100 science papers, reports, and models. As a 

consultant, he conducts research, workshops, lectures; he also contributes papers and 

reports on both terrestrial and riverine restoration programs and projects. He is actively 

involved at the State, regional, and national level on restoration programs.

 58
Theodore A. Kennedy, Ph.D.

Aquatic Ecologist 

U.S. Geological Survey 

Southwest Biological Science Center 

Grand Canyon Monitoring and Research Center 

Education 

Ph.D., 2002, Ecology, University of Minnesota 

B.S., 1994 Ecology, California Polytechnic State University at San Luis Obispo 

Current Research 

Current research involves the development of a research program on the aquatic food 

base that will clarify the role that food plays in determining the distribution, growth, and 

condition of fish in the Colorado River. 

Recent Publications 

Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2005, Eradication of invasive saltcedar 

(Tamarix ramosissima) along a desert springbrook increases native fish density: 

Ecological Applications, v.15, p. 2072–2083. 

Kennedy, T.A., and Hobbie, S.E., 2004, Salt cedar invasion (Tamarix ramosissima) alters 

organic matter dynamics in a desert stream: Freshwater Biology, v. 49, p. 65–76. 

Kennedy, T.A., Naeem, S., Howe, K.M., Knops, J.M.H., Tilman, D., Reich, P., 2002, 

Biodiversity as a barrier to ecological invasion: Nature, v. 417, p. 636–638. 

Levine, J., Kennedy, T.A., and Naeem, S., 2002, Neighbourhood-scale effects of species 

diversity on biological invasions and their relation to community patterns, in Naeem, 

S., Loreau, M., and Inchausti, P., eds., Biodiversity and ecosystem functioning: 

syntheses and perspectives: Oxford University Press, p. 114–124. 

Raffaelli, D., van der Putten, W.H., Persson, L., Wardle, D.A., Petchey, O.L., Koricheva, 

J., van der Heijden, M., Mikola, J., and Kennedy, T., 2002, Multi-trophic dynamics and 

ecosystem processes, in Naeem, S., Loreau, M., and Inchausti, P., eds., Biodiversity 

and ecosystem functioning: syntheses and perspectives: Oxford University Press, p. 

147–154. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Josh Korman—Workshop Facilitator 

Systems Ecologist 

Ecometric Research Inc. 

Education 

Ph.D, in progress, Zoology, University of British Columbia, Vancouver, B.C. 

M.S., 1989, Biological Oceanography, University of British Columbia, Vancouver, B.C. 

B.S., 1984, Biology, McGill University, Montreal, Quebec 

Current Research 

Current research activities include statistical analysis of environmental and fisheries data, 

development of computer simulation models for resource management, experimental design 

for environmental monitoring, fisheries stock assessment (analysis and field work), and 

development of decision support system software. 

Recent Publications 

Korman, J., Melville, C.C., and Higgins, P.S., 2007, Integrating multiple sources of data 

on migratory timing and catchability to estimate escapement for steelhead trout 

(Oncorhynchus mykiss): Can. J. Fish. Aquat. Sci., v. 64, p. 1101–1115. 

Korman, J., Wiele, S.M., and Torizzo, M., 2003, Modelling effects of discharge on 

habitat quality and dispersal of juvenile humpback chub (Gila Cypha) in the Colorado 

River, Grand Canyon: Riv. Res. Applic., v.12, p. 1–23. 

Korman, J., Ahrens, R.N.M., Higgins, P.S., and Walters, C.J., 2002, Effects of observer 

efficiency, arrival timing, and survey life on estimates of escapement for steelhead 

trout (Oncorhynchus mykiss) derived from repeat mark-recapture experiments: Can. J. 

Fish. Aquat. Sci., v. 59, p. 1116–1131. 

Korman, J., and Higgins, P.S., 1997, Utility of escapement time series data for 

monitoring the response of salmon populations to habitat alteration: Can. J. Fish. 

Aquat. Sci., v. 54, p. 2058–2097. 

Korman, J., Peterman, R.M., and Walters, C.J., 1995, Empirical and theoretical analyses 

of time-series bias in stock-recruitment relationships of Sockeye salmon (Oncorynchus 

nerka): Can. J. Fish. Aquat. Sci., v. 52, p. 2174–2189. 

 60
Theodore S. Melis, Ph.D. 

Physical Scientist 

U.S. Geological Survey 

Southwest Biological Science Center 

Grand Canyon Monitoring and Research Center 

Education 

Ph.D., 1997, Geosciences, University of Arizona 

B.S. and M.S., 1990, Geology, Northern Arizona University 

Current Research 

Current interests involve the design and implementation of scientific investigations 

associated with biology, physical, and cultural resource monitoring and research in 

support of the Glen Canyon Dam Adaptive Management Program. 

Recent Publications 

Wright, S.A., Schmidt, J.C., Melis, T.S., Topping, D.J. and Rubin, D.M., in press, Is there 

enough sand? Evaluating the fate of Grand Canyon sandbars, GSA Today, Geological 

Society of America. 

Melis, T.S., Topping, D.J., Rubin, D.M. and Wright, S.A., 2007, Research furthers 

conservation of Grand Canyon sandbars, U.S. Geological Survey Fact Sheet 2007-

3020, 4p. 

Rubin, D.M., Chezar, H., Harney, J.N., Topping, D.J., Melis, T.S., and Sherwood, C.R., 

2006, Underwater microscope for measuring spatial and temporal changes in bedsediment grain size: U.S. Geological Survey Open-File Report 2006–1360, 

http://pubs.usgs.gov/of/2006/1360/ 

Rubin, D.M., Chezar, H., Topping, D.J., Melis, T.S., and Harney, J., 2007, Two new 

approaches for measuring spatial and temporal changes in bed-sediment grain size: 

Sedimentary Geology, 7 p., doi: 10.1016/j.sedgeo.2007.03.020. 

Rubin, D.M., Chezar, H., Harney, J.N., Topping, D.J., Melis, T.S., Sherwood, C.R., 2007, 

Underwater microscope for measuring spatial and temporal changes in bed-sediment 

grain size, Sedimentary Geology, doi: 10.1016/j.sedgeo.2007.03.020 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Randall Peterson 

Environmental Resources Division Manager, Upper Colorado Region 

Bureau of Reclamation 

Biography 

Mr. Peterson graduated from the University of Utah in 1978 with a bachelor’s degree in 

Civil Engineering. He has worked in the Department of the Interior with the Bureau of 

Reclamation for the past 30 years, working extensively on hydrologic estimations and 

risk-based decision making. For 15 years he led Reclamation’s operation of the mainstem 

Upper Colorado River Basin reservoirs, including Glen Canyon Dam. He was 

instrumental in modifying the operation of Glen Canyon Dam following the flood years 

of the 1980s to reduce the frequency of uncontrolled flooding, and in the mid-1990s led 

the negotiation of an agreement between the Department of the Interior and the Colorado 

Basin States allowing the 1996 test of the Beach/Habitat Building Flow, the widely 

publicized spike flow from Glen Canyon Dam. He has co-chaired the Colorado River 

Management Work Group, a public involvement group which is involved in the operation 

of the entire Colorado River reservoir system, and served as program manager of the 

Glen Canyon Dam Adaptive Management Work Group, a science-based collaborative 

effort which seeks to protect the resources of the Grand Canyon while meeting the project 

purposes of the dam. He is currently the Upper Colorado regional office environmental 

resources division manager. 

 62
William E. Pine III, Ph.D. 

Assistant Professor 

Department of Fisheries and Aquatic Sciences 

University of Florida 

Education 

Ph.D., 2003, Zoology, North Carolina State University, Raleigh, North Carolina 

M.S., 1999, Fisheries Science, University of Florida, Gainesville, Florida 

B.S., 1997, Fisheries Management, Auburn University, Auburn, Alabama 

Current Research 

Primary research responsibilities are related to evaluating how riverine fish populations 

respond to modified flow regimes related to minimum flow and level regulations or to 

hydroelectric dam operations. Additional areas of research include developing new estimation 

techniques for evaluating trends in animal populations and estimating population vital rates. 

Recent Publications 

Pine, W.E., III, Martell, S.J.D., Jensen, O.P., Walters, C.J., and Kitchell, J.F., submitted, 

Effects of post-release mortality of the efficacy of length limits and catch-and-release 

policies: a case study of blue, white, and striped marlin, Canadian Journal of Fisheries 

and Aquatic Sciences. 

Pine, W.E., III, Martell, S.J.D., Walters, C.J., and Kitchell, J.F., submitted, 

Counterintuitive responses of fish populations to management: some common causes 

and implications for predictions based on ecosystem modeling, Fisheries. 

Martell, S.J.D., Pine, W.E., III, and Walters, C.J., in press, Parameterizing age-structured 

models from a fisheries management perspective, Canadian Journal of Fisheries and 

Aquatic Sciences. 

Coggins, L.G., Jr., Catalano, M.J., Allen, M.S., Pine, W.E., III, and Walters, C.J., 2007, 

Effects of cryptic mortality and the hidden costs of using length limits in fishery 

management, Fish and Fisheries, v. 9, p. 196–210. 

Pollock, K.H., and Pine, W.E., III, 2007, The design of field studies to estimate catch and 

release mortality, Fisheries Ecology and Management, v.14, p.1–8. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Roger Pulwarty, Ph.D. 

Director, National Integrated Drought Information System 

Physical Scientist (Climatologist), National Oceanic and Atmospheric Administration, Physical 

Sciences Division 

Education 

Ph.D., 1994, Climate, University of Colorado, Boulder 

BS, 1986, Atmospheric Sciences, York University 

Current Research 

Climate impacts assessment, climate analysis, and applications research for adaptation 

and climate services development. 

Recent Publications 

Pulwarty, R., and S. Cohen, 2007, Communicating scientific information: Moving within 

and beyond climate impact assessments: Global Environmental Change. 

Pulwarty, R., Simpson, C., and Nierenberg, C., 2007, The Regional Integrated Sciences 

and Assessments Program: Crafting regional assessments for the long haul, in Knight, 

C., and Jager, J., eds., Integrated regional assessments: Cambridge Press. 

Pulwarty, R., Trotz, N., and Nurse, L., 2007, Risk and Criticality: Caribbean Islands in a 

Changing Climate: in Bataglia A., and Hare, W., eds., Key vulnerable regions and 

climate change: Potsdam Institute Potsdam. 

Pulwarty, R., Wilhite, D., Diodato, D., and Nelson, D., 2007, Drought in changing 

environments—Creating a Roadmap: Vehicles and Drivers Natural Hazards Observer. 

Pulwarty, R., Olanrewaju, S., and Zorba, P., 2007, Communicating agro-climatological 

information, including forecasts, for agricultural decisions, in Stigter K., ed, Guide to 

agro-meteorological practices: WMO Commission for Agricultural and Meteorological 

Practices and the International Society for Agricultural Meteorology Geneva, 40 p., 

http://www.wmo.ch/web/wcp/agm/RevGAMP/chap18-draft.pdf. 

 64
Dale M. Robertson, Ph.D. 

Research Hydrologist 

U.S. Geological Survey 

Wisconsin Water Science Center 

Glen Canyon Dam Adaptive Management Program Science Advisor 

Education 

Ph.D., 1989, Oceanography and Limnology, University of Wisconsin, Madison 

M.S., 1984, Oceanography and Limnology, University of Wisconsin, Madison 

B.S., 1981, Biology, Chemistry, and Mathematics; St. Norbert College, DePere, 

Wisconsin 

Current Research 

Research deals with understanding the influence of environmental factors, watershed 

management strategies, and in-lake management alternatives on the water quality of 

lakes, reservoirs, and rivers; modeling water quality and the effects of artificial 

destratification; modeling regional loading; and examining ice cover as a climatic 

indicator. 

Recent Publications 

Robertson, D.M., and Schladow, S.G., 2008, Response in the water quality in the Salton 

Sea to changes in phosphorus loading: An empirical modeling approach: 

Hydrobiologia, v. 604, p. 5–19.

Robertson, D.M., Schladow, S.G., and Holdren, G.C., 2008, Long-term changes in the 

phosphorus loading to and trophic state of the Salton Sea: Hydrobiologia, v. 604, p. 

21–36. 

Robertson, D.M., Garn, H.S., and Rose, W.J., 2007, Response of calcareous Nagawicka 

Lake, Wisconsin, to changes in phosphorus loading: Lake and Reservoir Management, 

v. 23, p. 298–312. 

Robertson, D.M., Graczyk, D.J., Garrison, P.J., Wang, L., LaLiberte, G., and Bannerman, 

R., 2006, Nutrient concentrations and their relations to the biotic integrity of wadeable 

streams in Wisconsin: U.S. Geological Survey Professional Paper 1722, 139 p. 

Robertson, D.M., Saad, D.A., and Heisey, D.M., 2006, A regional classification scheme 

for estimating reference water quality in streams using land-use-adjusted spatial 

regression-tree analysis: Environmental Management, v. 37, no. 2, p. 209–229. 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

David J. Topping, Ph.D. 

Research Hydrologist 

U.S. Geological Survey 

Southwest Biological Science Center 

Grand Canyon Monitoring and Research Center 

Education 

Ph.D., 1997, Geological Sciences, University of Washington, Seattle, Washington 

M.S., 1991, Geological Sciences, University of Washington, Seattle, Washington 

B.S., 1988, Earth, Atmospheric, and Planetary Sciences; Massachusetts Institute of 

Technology, Cambridge, Massachusetts 

Current Research 

Research focuses on the physical interactions between the flow, upstream sediment 

supply, channel geometry, and bed-sediment grain size. Centerpiece of research has been 

the investigation of sediment transport in rivers with intermittent, limited supplies of 

sediment. Key scientific impact from this work has been to show that in many settings 

changes in bed grain size can play important roles in regulating sand transport. In certain 

settings, such as the regulated Colorado River in Grand Canyon, grain-size changes may 

be as or more important than flow changes in regulating sand transport. These findings 

contradict conventional sediment-transport paradigms, in which water discharge is 

typically considered the de facto dominant regulator of sand transport. 

Recent Publications 

Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., Melis, T.S., Wright, S.A., 

Kaplinski, M., Draut, A.E., and Breedlove, M.J., 2006, Comparison of sedimenttransport and bar-response results from the 1996 and 2004 controlled-flood 

experiments on the Colorado River in Grand Canyon: CD-ROM Proceedings of the 8th

Federal Inter-Agency Sedimentation Conference, Reno, Nevada, April 2–6, 2006, 

ISBN 0-9779007-1-1. 

Topping, D.J., Rubin, D.M., and Melis, T.S., 2007, Coupled changes in sand grain size 

and sand transport driven by changes in the upstream supply of sand in the Colorado 

River: Relative importance of changes in bed-sand grain size and bed-sand area: 

Sedimentary Geology, 24 p., doi: 10.1016/j.sedgeo.2007.03.016. 

Topping, D.J., Wright, S.A., Melis, T.S., and Rubin, D.M., 2007, High-resolution 

measurements of suspended-sediment concentration and grain size in the Colorado 

River in Grand Canyon using a multi-frequency acoustic system: Proceedings of the 

Tenth International Symposium on River Sedimentation, August 1–4, 2007, Moscow, 

Russia, v. 3, p. 330–339. 

 66
Melis, T.S., Topping, D.J., Rubin, D.M., Wright, S.A., 2007, Research furthers 

conservation of Grand Canyon sandbars: U.S. Geological Survey Fact Sheet 2007-

3020, 4 p. 

Wright, S.A., Schmidt, J.C., Melis, T.S., Topping, D.J., and Rubin, D.M., in press, Is 

there enough sand? Evaluating the fate of Grand Canyon sandbars: GSA Today. 

 67
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Harold M. Tyus, Ph.D. 

Senior Research Associate 

Center for Limnology 

Cooperative Institute for Research in Environmental Studies 

University of Colorado 

Glen Canyon Dam Adaptive Management Program Science Advisor 

Education 

Ph.D., 1971, Zoology, N.C. State University 

M.S., 1969, Zoology, N.C. State University 

B.S., 1964, Chemistry and Biology, Florida Southern College 

Current Research 

Biology and ecology of freshwater fishes. Conservation and management of native and 

endangered fishes. Colorado River fishes. 

Recent Publications 

Portz, D.E., and Tyus, H.M., 2004, Fish humps in two Colorado River fishes: An induced 

morphological response to cyprinid predation?: Environmental Biology of Fishes, v. 

71, p. 233–245. 

 Tyus, H.M. and Saunders, J.F., III, 2000, Nonnative fish control and endangered fish 

recovery: lessons from the Colorado River: Fisheries, v. 25, no. 9, p. 17–22. 

 U.S. Fish and Wildlife Service, 1998, Razorback sucker Xyrauchen texanus recovery 

plan (Prepared by H. M. Tyus, University of Colorado): Bethesda, MD, Fish and 

Wildlife Reference Service (U.S. Govt. Printing Ofc. #1999-12-1591B). 

 Tyus, H.M., 1992, An instream flow philosophy for recovering endangered Colorado 

River fishes: Rivers v. 3, p. 27–36. 

 Karp, C.A., and Tyus, H.M., 1990, Behavior and interspecific interactions of Colorado 

squawfish Ptychocheilus lucius, and five other fish species: Copeia, v. 1990, p. 25–34. 

 68
Richard A. Valdez, Ph.D. 

Senior Aquatic Biologist 

SWCA Environmental Consultants 

Education 

Post-Doctorate, 1997, Aquatic Stream Ecology, Utah State University, Logan 

Ph.D., 1975, Fisheries Ecology, Utah State University, Logan 

M.S., 1971, Fisheries, Utah State University, Logan 

B.S., 1968, Wildlife Management, New Mexico State University, Las Cruces 

Current Research 

Research efforts focus on fisheries biology in aquatic ecosystems of western North 

America, including fish population dynamics, abundance estimators, recruitment models, 

stock assessment, population viability analysis, design and implementation of monitoring 

programs. 

Recent Publications 

Price-Stubbs Fish Passage—Technical assistance to U.S. Fish and Wildlife Service 

(USFWS) on design and implementation of fish passage on the Price-Stubbs Dam of 

the Upper Colorado River near Grand Junction, CO (2007–present). 

Green River Study Plan—Chairman of Committee to develop a long-term study plan for 

the Green River as part of the Flaming Gorge Dam EIS for USFWS (2006–07). 

Nonnative Fish Workshop—Facilitator for three annual Nonnative Fish Workshops for 

the Upper Colorado River Basin at request of USFWS (2005–07). 

Yampa River Nonnative Fish Strategy—Author and coordinator for developing strategy 

at request of Implementation Committee for Upper Colorado River Recovery Program 

(2007–present). 

Glen Canyon Dam Environmental Impact Statement (EIS)—Member of Science Panel 

and writing team for Long-Term Experimental Plan EIS for Bureau of Reclamation 

(2006–present). 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Carl Walters, Ph.D. 

Professor 

Fisheries Centre 

University of British Columbia 

Education 

Ph.D., 1969, Colorado State University, Fort Collins, Colorado 

M.S., 1967, Colorado State University, Fort Collins, Colorado 

B.S., 1965, Humboldt State College, Arcata, California 

Current Research 

Current research is on the theory of harvesting in natural resource management; the 

development of rapid techniques for teaching systems analysis and mathematical 

modelling to biologists and resource managers, using problem-oriented workshops and 

seminars; and active field research program on the responses of aquatic communities to 

disturbances such as removal of selective species by introduced fish populations and 

enhancement of productivity through fertilization. 

Recent Publications 

Allen, M.S., Walters, C.J., and Myers, R., 2008, Temporal trends in voluntary release of 

largemouth bass, with fishery implications: North American Journal of Fisheries 

Management, v. 28, p. 418–427. 

Walters, C., Martell, S.J.D., and Christensen, V., 2007, An Ecosim model for exploring 

ecosystem management options for the Gulf of Mexico: implications of including 

multistanza life history models for policy predictions: Bull. Mar. Sci. 

Walters, C., Hilborn, R., and Parrish, R., 2007, An equilibrium model for predicting the 

efficacy of marine protected areas in coastal areas: Can. J. Fish. Aquat. Sci., v. 64, p. 

1009–1018. 

Walters, C., and Christensen, V., 2007, Adding realism to foraging arena predictions of 

trophic flows in Ecosim ecosystem models: shared foraging arenas and bout feeding: 

Ecol. Modeling, v. 209, p. 342–350. 

Martell, S., Pine, W., and Walters, C., 2007, Parameterization of age-structured models 

from a management oriented perspective: Can. J. Fish. Aquat. Sci. 

 70
Scott A. Wright, Ph.D. 

Research Hydrologist 

U.S. Geological Survey 

California Water Science Center 

Education 

Ph.D., 2003, Civil Engineering, University of Minnesota 

M.S., 1997, Civil Engineering, University of Iowa 

B.S., 1994, Civil Engineering, University of Iowa 

Current Research 

Surface water, sediment transport, and water-quality monitoring, modeling, and research 

related to the effects of Glen Canyon Dam on the Colorado River ecosystem in Marble 

and Grand Canyons. 

Recent Publications 

Anderson, C.R., and Wright, S.A., in press. Development and application of a water 

temperature model for the Colorado River ecosystem below Glen Canyon Dam, 

Arizona, Proceedings of the American Institute of Hydrology Annual Meeting and 

International Conference, April 22–25, Reno, NV. 

Voichick, N., and Wright, S.A., 2007. Water-temperature data for the Colorado River and 

tributaries between Glen Canyon Dam and Spencer Canyon, Northern Arizona, 1988 – 

2005, U.S. Geological Survey Data Series 251, 24p., http://pubs.usgs.gov/ds/2007/251/. 

Snyder, N.P., Wright, S.A., Alpers, C.N., Flint, L.E., Holmes, C.W., and Rubin, D.M., 

2006, Reconstructing depositional processes and history from reservoir stratigraphy: 

Englebright Lake, Yuba River, northern California: J. Geophys. Res., v. 111, F04003, 

doi:10.1029/2005JF000451. 

Curtis, J.A., Flint, L.E., Alpers, C.N., Wright, S.A., and Snyder, N.P., 2006, Use of 

sediment rating curves and optical backscatter data to characterize sediment transport 

in the upper Yuba River watershed, California, 2001–03, U.S. Geological Survey 

Scientific Investigations Report 2005-5246, http://pubs.usgs.gov/sir/2005/5246/, 74 p. 

Ganju, N.K., Schoellhamer, D.H., Murrell, M.C., Gartner, J.W., and Wright, S.A., 2006, 

Constancy of the relation between floc size and density in San Francisco Bay, in Maa, 

J.P., Sanford, L.P., and Schoellhamer, D.H., eds., Estuarine and Coastal Fine Sediment 

Dynamics 8: Elsevier Academic Press.

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Appendix E. Responses to EIS Cooperator Questions

Representatives from some of the agencies cooperating with Reclamation in the 

development of the long-term experimental plan (LTEP) environmental impact statement 

(EIS) had questions during the first few months of 2007 regarding resources affected by 

Glen Canyon Dam operations. The questions are presented below, ranked in order of 

importance in relation to future experimental designs. 

Following the workshop, GCMRC scientists developed concise answers to these 

questions based on the discussions and results of the workshop. Questions 11 through 14 

were not addressed at the workshop. 

1. What are the factors limiting humpback chub reproduction and rearing in the 

main channel of the Colorado River below Glen Canyon Dam? 

Current mainstem Colorado River water temperatures are too low in the summer and fall 

to support large-scale expansion of the Grand Canyon humpback chub population 

(Valdez and Masslich, 1999; Clarkson and Childs, 2000); warmer summer and fall water 

temperatures are needed. This finding is supported by numerous investigations on the 

deleterious effects of suboptimal water temperature on swimming performance, predator 

avoidance (Ward and others, 2002; Ward and Bonar, 2003), growth (Robinson and 

Childs, 2001), and reproduction (Kaeding and Zimmerman, 1983) of native fish species. 

As a result, water temperature is potentially the most important factor limiting expansion 

of the Grand Canyon humpback chub population (Clarkson and Childs, 2000; Kaeding 

and Zimmerman, 1983). The recent stabilization of the population appears to be 

consistent with the observation that warmer water benefits native fishes, although some 

increase in humpback chub recruitment likely began before the onset of the warmest 

recent mainstem water temperatures (Melis and others, 2006). 

2. Have humpback chub population estimates stabilized or increased recently, 

and if so, why (warm water, nonnative control, other factors)? 

Current abundance estimates for the Little Colorado River population of 

humpback chub suggest that the adult population size may have stabilized at a new, lower 

level beginning in 2000 (Melis and others, 2006). As described by Coggins and others 

(2006a), these estimates are generated using the age-structured mark-recapture (ASMR) 

model, which is an open-population framework that updates all current and past 

population estimates as new information is incorporated. As a result, estimates of past 

abundance may change with incorporation of new data. For instance, the adult population 

estimate was 4,356 adult fish in 2001, which was produced using the ASMR3 model with 

the data available through 2002 and with constant adult mortality (Coggins and others, 

2006b). The 2001 adult abundance estimate using the same model but considering data 

through 2005 was 4,474 fish (Melis and others, 2006). The difference in point estimates 

is predominantly a result of updating estimates of mortality rate and can lead to 

differences in absolute estimates, particularly in the most recent years of the assessment. 

As noted by Melis and others (2006), much of this discrepancy is the result of uncertainty 

in mortality rate estimation, resulting from large decreases in sampling intensity during 

the mid to late 1990s. As more years of consistent sampling accrue since this lapse, 

 72
uncertainty in mortality rate should decrease. However, it is important to note that point 

estimate updating, particularly for the most recent years, will always occur as more 

information on individual cohorts becomes available. 

 The participants agreed that the Grand Canyon humpback chub population 

possibly benefited from both warmer mainstem water temperatures and the removal of 

nonnative fishes, especially rainbow trout, near the mouth of the Little Colorado River 

(Melis and others, 2006). Although this conclusion is based predominantly on general 

ecological principles and knowledge of Colorado River native fish life history, benefits to 

native fauna have been documented as a result of nonnative control efforts elsewhere 

(Ruzycki and others, 2003; Vredenburg, 2004). Resolution as to which of these factors is 

more important to humpback chub conservation is intellectually appealing, but would 

require greater experimentation than the participants recommend. For example, one 

approach to determining the relative importance of nonnative fish removal to the 

conservation of humpback chub would be to discontinue nonnative control efforts and 

allow the nonnative populations to increase without bound. If the current stabilization of 

the humpback chub population (Melis and others, 2006) continued while release water 

temperatures remained elevated, it would suggest that temperature was a more important 

factor than nonnative removal. However, the participants cautioned against employing 

such an approach, with its emphasis on learning about resource protection. A number of 

the participants have firsthand experience with the deleterious effects of nonnative fish 

populations on native species (Bestgen and others, 2006; Pine and others, 2007; Olden 

and others, 2006; Tyus and Saunders, 2000), experiences that suggest that it is important 

to keep these species under control while they are still relatively small proportions of the 

total fish population (Bestgen and others, 2007). When nonnative populations expand 

quickly, it may be impossible to reduce or contain them. Therefore, the participants 

agreed that as the GCDAMP moves into the future, there may be cases where resource 

protection and reducing risk (Francis and others, 2007) will have to be emphasized at the 

expense of determining specific cause-and-effect relationships. The participants did not 

eschew learning altogether, strongly advocating for it whenever possible, but not at the 

expense of rare resource protection, particularly in the case of the humpback chub. 

3. Will warming dam releases positively affect listed or special status species in 

the Colorado River ecosystem (including humpback chub and effects of nonnative 

species)? 

Future releases of warm water could occur naturally (Seager and others, 2007) as 

the result of prolonged drought conditions and reduced flows from Glen Canyon Dam, or 

with the operation of a temperature control device, or both. It is widely believed that 

warmwater conditions may benefit Colorado River native fish, but it is also likely that 

some nonnative fish may benefit from a changed thermal regime (Moyle and Light, 

1996). Warmwater nonnative fishes are widely regarded as a major threat to humpback 

chub and other native fishes in the Colorado River Basin in general, and Grand Canyon in 

particular (Tyus and Saunders, 2000). 

Because the expansion or invasion of warmwater species is potentially more 

detrimental than the current salmonid-dominated nonnative community (Minckley and 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Deacon, 1991; Lentsch and others, 1996; Bestgen and others, 2006; Bestgen and others, 

2007), the participants recognized that an option to cool the dam release temperatures 

may be critical to help control warmwater nonnative fish. The participants called for an 

expanded, aggressive program to better understand the composition of the Grand Canyon 

fish community, including impacts from the natural warming of 2002–06. They 

underscored the need to detect any changes in nonnative abundance so as to address 

negative impacts with additional actions, as needed. 

4. Can the decline in sediment resources since 1990 be reversed using “flow” 

options with remaining downstream sand supplies from tributaries (Paria and Little 

Colorado Rivers and lesser tributaries)? 

On the basis of previous studies, sandbars and associated habitats have apparently 

decreased since closure of Glen Canyon Dam, owing primarily to the fact that 84–94 

percent of the natural sand supply is now trapped within the reservoir behind the dam 

(Wright and others, 2005). It is also known that 1996 Record of Decision releases from 

the dam are capable of transporting new sediment supplies entering the ecosystem from 

downstream tributaries in relatively short periods—days to months—under dam releases 

associated with average to wetter hydrology of the upper Colorado River Basin (Rubin 

and others, 2002). Such dam operations also export remnant sandbars that remain from 

the period before dam closure. Schmidt and others (2004) report that about 25 percent of 

the sandbar area between river miles 0 and 87 was lost to ongoing erosion between 1983 

and 2000. 

In response to this information, sediment scientists have suggested an 

experimental option for managers to consider that could reverse sandbar erosion. The 

proposed experimental approach depends upon the ability of managers to release shortduration spike flows of 42,000 to 45,000 cfs within weeks to a few months of tributary 

floods that add new sand to the Colorado River ecosystem (Rubin and others, 2002; 

Wright and others, 2005; Topping and others, 2006). To determine whether declines in 

sediment resources can be reversed with flows, such future tests presumably need to 

occur, at least initially, at the same frequency that significant new tributary sand supplies 

are added to the river. The participants accepted that future sediment testing would likely 

be part of any proposed long-term experimental design and saw no reason why such tests 

could not be conducted as part of the environmental triggers strategy. 

5. Will high flow experiments promote conservation of high priority AMP 

biological resources (for example, native fishes, native riparian vegetation, aquatic 

food base, rainbow trout)? 

6. What effect do powerplant releases (ramp rates, fluctuating and steady) have 

on listed or special status species (including humpback chub) in the Colorado River 

ecosystem? 

In the opinion of the participants, high and/or fluctuating releases from Glen 

Canyon Dam would not result in ecological benefits. There was no resource benefit 

 74
identified from such flows for native fish, sediment conservation, or other natural 

resources (Gloss and others, 2005). The participants did note that there is evidence 

humpback chub may be able to tolerate some flow fluctuations, particularly if 

fluctuations occurred in winter months; however, winter fluctuations may not be 

consistent with sediment conservation, and the winter life-history stages of Grand 

Canyon humpback chub have received little study. Indeed, the recently observed 

population stabilization of adult humpback chub has occurred in the presence of the 

modified low fluctuating flow regime. The assertion that fluctuating flows could provide 

additional food to rainbow trout and humpback chub assumes that these species are 

dependent on drifting aquatic vegetation and invertebrates produced below Glen Canyon 

Dam. The assumption that these fish are limited by available food resources is currently 

being investigated. Limited fluctuations, such as beach/habitat-building flows, may, at 

least temporarily, disadvantage nonnative fish, especially small-bodied species (Minckley 

and Meffe, 1987; Valdez and others, 2001); this hypothesis needs further testing. In 

conclusion, fluctuations did not appear to be of any benefit to native fishes (other than 

their potential to disadvantage nonnative fishes if necessary) and have been shown to 

accelerate the export of sediment out of Grand Canyon (Rubin and others, 2002; Wright 

and others, 2005). 

7. Can the decline of humpback chub be reversed by expanding the current 

range of humpback chub into suitable unused historical habitat within GRCA/GLCA 

(tributaries/mainstem)? 

The participants concluded translocations could support expansion of humpback 

chub in Grand Canyon. In the opinion of the participating experts, the tributary stream 

with the best likelihood of success for such a project is Bright Angel Creek; however, 

they thought that other tributaries could also be successful in establishing humpback chub 

(Valdez and others, 2000). Translocating some humpback chub to Bright Angel Creek 

would likely require complete removal of all nonnative fishes first with chemical 

treatment, which may be difficult or impossible in a national park. There was general 

agreement among the participants that groups of humpback chub in small tributary 

streams would be unlikely to be considered additional populations because of the limited 

numbers of individuals that could be maintained in waterways of that size (Valdez and 

others, 2000). The participants concluded that if a second population were to be 

established in Grand Canyon, success was much more likely in the mainstem (somewhat 

independent of the Little Colorado River-based population) than in any one tributary 

stream. The participants generally agreed that such translocations were unlikely to cause 

any important confounding of humpback chub monitoring or population modeling. 

8. If the answer to core question 4 is yes, then will such enhanced sediment 

conservation promote in situ preservation of archaeological sites? 

(NOTE: Core question 4. Can the decline in sediment resources since 1990 be 

reversed using “flow” options with remaining downstream sand supplies from tributaries 

[Paria and Little Colorado Rivers and lesser tributaries]?) 

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USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Participants did not specifically discuss the issue of promoting in site preservation 

of archaeological sites other than to note that sediment supplies above the zone of 

inundation need to be maintained to provide any benefits to these higher elevation, 

sediment-dependent resources. The main mechanism for achieving these objectives 

would appear to be periodic beach/habitat-building flows conducted during sedimentenriched conditions. 

9. How can invasive or nonnative species be eliminated, reduced, or controlled in 

the Colorado River ecosystem? 

The participants noted that the first step in addressing this question would be a 

better understanding of which nonnative fish species threaten the native fishes in Grand 

Canyon and where they occur. This understanding can only be developed with a more 

robust sampling program for nonnative species; the participants recommended that the 

existing program be expanded as soon as possible. 

The participants also strongly recommended the inclusion of a temperature 

control device design that allows for the release of cool water in addition to warm water. 

The most important reason for including this design option was to allow for the release of 

cool water to limit the expansion and success of warmwater nonnative fish, in case their 

numbers increase to levels that threaten native fishes. 

10. If the answer to core question 4 is yes, then will such enhanced sediment 

conservation promote conservation of recreation beaches and campable area? 

(NOTE: Core question 4. Can the decline in sediment resources since 1990 be 

reversed using “flow” options with remaining downstream sand supplies from tributaries 

[Paria and Little Colorado Rivers and lesser tributaries]?) 

Participants did not specifically discuss the question of using “flow” options with 

downstream sand supplies other than to note that sediment supplies above the zone of 

inundation need to be maintained to provide any benefits to these higher elevation, 

sediment-dependent resource categories. The main mechanism for achieving these 

objectives would appear to be periodic beach/habitat-building flows conducted during 

sediment-enriched conditions. 

References

Bestgen, K.R., Zelasko, K.A., Compton, R.I., and Chart, T., 2006, Response of the Green 

River fish community to changes in flow and temperature regimes from Flaming Gorge 

Dam since 1996 based on sampling conducted from 2002 to 2004: final report, 

Colorado River Recovery Implementation Program Project Number 115, Larval Fish 

Laboratory Contribution 144, 129 p. 

Bestgen, K.R., Zelasko, K.A., Wilcox, C.T., 2007, Non-native fish removal in the Green 

River, Lodore and Whirlpool Canyons, 2002–2006, and fish community response to 

altered flow and temperature regimes, and non-native fish expansion: final report, 

 76
Colorado River Recovery Implementation Program Project Number 115, Larval Fish 

Laboratory Contribution 149, 84 p. 

Clarkson, R.W., and Childs, M.R., 2000, Temperature effects of hypolimnial-release 

dams on the early life stages of Colorado River Basin big-river fishes: Copeia, v. 2000, 

no. 2, p. 402–412. 

Coggins, L.G., Jr., Pine, W.E., Walters, C.J., and Martell, S.J.D., 2006a, Age-structured 

mark-recapture analysis: a virtual-population-analysis-based model for analyzing agestructured capture-recapture data: North American Journal of Fisheries Management, v. 

26, p. 201–205. 

Coggins, L.G., Jr., Pine, W.E., III, Walters, C.J., Van Haverbeke, D.R., Ward, D., and 

Johnstone, H.C., 2006b, Abundance trends and status of the Little Colorado River 

population of humpback chub: North American Journal of Fisheries Management, v. 

26, p. 233–245. 

Francis, R.C., Hixon, M.A., Clarke, M.E., Murawski, S.A., and Ralston, S., 2007, Ten 

commandments for ecosystem-based fisheries scientists: Fisheries, v. 32, no. 5, p. 217–

233. 

Gloss, S.P., Lovich, J.L, and Melis, T.S., eds., 2005, The state of the Colorado River 

ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, 220 p. 

Kaeding, L.R., and Zimmerman, M.A., 1983, Life history and ecology of the humpback 

chub in the Little Colorado and Colorado Rivers of the Grand Canyon: Transactions of 

the American Fisheries Society, v. 112, p. 557–594. 

Lentsch, L.D., Muth, R.T., Thompson, P.D., Hoskins, B.G., and Crowl, T.A., 1996, 

Options for selective control of nonnative fishes in the upper Colorado River Basin: 

Salt Lake City, Utah, Utah Division of Wildlife Resources Publication 96-14. 

Melis, T.S., Martell, S.J.D., Coggins, L.G., Jr., Pine, W.E., III, and Andersen, M.E., 

2006, Adaptive management of the Colorado River ecosystem below Glen Canyon 

Dam, Arizona: using science and modeling to resolve uncertainty in river management 

in Specialty Summer Conference on Adaptive Management of Water Resources, 

Missoula, Mont., 2006, CD-ROM Proceedings (ISBN 1-882132-71-8): Middleburg, 

Va., American Water Resources Association. 

Minckley, W.L., and Deacon, J.E., eds., 1991, Battle against extinction: Tuscon, Ariz., 

University of Arizona Press, 517 p. 

Minckley, W.L., and Meffe, G.K., 1987, Differential selection for native fishes by 

flooding in streams of the arid American Southwest, in Matthews, W.J., and Heines, 

D.C., eds., Ecology and evolution of North American stream fish communities: 

Norman, Okla., University of Oklahoma Press, p. 93–104. 

Moyle, P.B., and Light, T., 1996, Fish invasions in California: do abiotic factors 

determine success?: Ecology, v. 77, no. 6, p. 1666–1670. 

Olden, J.D., Poff, N.L., and Bestgen, K.R., 2006, Life-history strategies predict fish 

invasions and extirpations in the Colorado River Basin: Ecological Monographs, v. 76, 

no. 1, p. 25–40. 

 77
USGS Workshop on Scientific Aspects of the Long-Term Experimental Plan for Glen Canyon Dam, April 10–11, 2007, Flagstaff, Arizona

Pine, W.E., III, Kwak, T.J., and Rice, J.A., 2007, Modeling management scenarios and 

the effects of an introduced apex predator on a coastal riverine fish community: 

Transactions of the American Fisheries Society, v. 136, p. 105–120. 

Robinson, A.T., and Childs, M.R., 2001, Juvenile growth of native fishes in the Little 

Colorado River and a thermally modified portion of the Colorado River: North 

American Journal of Fisheries Management, v. 21, p. 809–815. 

Rubin, D.M., Topping, D.J., Schmidt, J.C., Hazel, J., Kaplinski, M., and Melis, T.S., 

2002, Recent sediment studies refute Glen Canyon Dam hypothesis: Eos, v. 83, no. 25, 

227-728, p. 273, 

http://www.gcmrc.gov/library/reports/physical/Fine_Sed/Rubin2002.pdf, accessed 

February 22, 2008.

Ruzycki, J.R., Beauchamp, D.A., and Yule, D.L., 2003, Effects of introduced lake trout 

on native cutthroat trout in Yellowstone Lake: Ecological Applications, v. 13, no. 1, p. 

23–37. 

Schmidt, J.C., Topping, D.J., Grams, P.E., and Hazel, J.E., Jr., 2004, System-wide 

changes in the distribution of fine sediment in the Colorado River corridor between 

Glen Canyon Dam and Bright Angel Creek, Arizona: Grand Canyon Monitoring and 

Research Center final report, cooperative agreement no. 1425-98-FC-40-22640, 

http://www.gcmrc.gov/library/reports/physical/Fine_Sed/Schmidt2004.pdf, accessed 

February 22, 2008. 

Seager, R., Ting, M., Held, I., Kushnir, Y., Lu, J., Vecchi, G., Huang, H.-P., Harnik, N., 

Leetmaa, A., Lau, N.-C., Li, C., Velez, J., and Naik, N., 2007, Model projections of an 

imminent transition to a more arid climate in southwestern North America: Science, v. 

316, p. 1181–1184. 

Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., Melis, T.S., Wright, S.A., 

Kaplinski, M., Draut, A.E., and Breedlove, M.J., 2006, Comparison of sedimenttransport and bar-response results from the 1996 and 2004 controlled-flood 

experiments on the Colorado River in Grand Canyon, in Federal Inter-Agency 

Sedimentation Conference, 8th, Reno, Nevada, April 2–6, 2006CD-ROM Proceedings 

(ISBN 0-9779007-1-1). 

Tyus, H.M, and Saunders, J.F., III, 2000, Nonnative fish control and endangered fish 

recovery: lessons from the Colorado River: Fisheries, v. 9, p. 17–24. 

Valdez, R.A., Carothers, S.W., Douglas, M.E., Douglas, M., Ryel, R.J., Bestgen, K.R., 

and Wegner, D.L., 2000, Research and implementation plan for establishing a second 

population of humpback chub in Grand Canyon: Grand Canyon Monitoring and 

Research Center final report, 80 p. 

Valdez, R.A., Hoffnagle, T.L., McIvor, C.C., McKinney, T., and Leibfried, W.C., 2001, 

Effects of a test flood on fishes of the Colorado River in Grand Canyon, Arizona: 

Ecological Applications, v. 11, no. 3, p. 686–700. 

Valdez, R.A., and Masslich, W.J., 1999, Evidence of reproduction by humpback chub in 

a warm spring of the Colorado River in Grand Canyon, Arizona: The Southwestern 

Naturalist, v. 44, no. 3, p. 384–387. 

 78
 79

Vredenburg, V.T., 2004, Reversing introduced species effects: experimental removal of 

introduced fish leads to rapid recovery of a declining frog: Proceedings of the National 

Academy of Science, v. 101, no. 20, p. 7646–7650. 

Ward, D.L., and Bonar, S.A., 2003, Effects of cold water on susceptibility of age-0 

flannelmouth sucker to predation by rainbow trout: The Southwestern Naturalist, v. 48, 

no. 1, p. 43–46. 

Ward, D.L., Maughan, O.E., Bonar, S.A., and Matter, W.J., 2002, Effects of temperature, 

fish length, and exercise on swimming performance of age-0 flannelmouth sucker: 

Transactions of the American Fisheries Society, v. 131, p. 492–497. 

Wright, S.A., Melis, T.S., Topping, D.J., and Rubin, D.M., 2005, Influence of Glen 

Canyon Dam operations on downstream sand resources of the Colorado River in Grand 

Canyon, in Gloss, S.P., Lovich, J.E., and Melis, T.S., eds., The state of the Colorado 

River ecosystem in Grand Canyon: U.S. Geological Survey Circular 1282, p. 17–31. 
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