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OCR for page 239
1 1
Glen Canyon Environmental Studies
Research Program:
Past, Present and Future
DUNCAN T. PAULSEN, Arizona State University, Tempe, Arizona
ABSTRACT: The present research program within the Grand Canyon
is a result of inadequacies of the initial Glen Canyon Environmental
Studies. These inadequacies were partially due to poor planning and
research design, but also to the high water conditions during the re-
search period. The results of the initial phase, GCES I, were reviewed
by a National Research Council committee which recommended, along
with the Glen Canyon Environmental Studies Executive Review Com-
mittee, that further studies be done on the effects of dam operations on
the Canyon resources. This led to establishment of GCES II which has
gone through an iterative process to develop testable hypotheses on the
effects of dam operations and other activities in the Canyon. Experi-
mental designs are being developed for research, and controlled re-
search discharges from the dam scheduled for the next 2 years. This
short-term research program has been developed to address the data
needs of the EIS which will select a dam operations alternative for the
future. It is recognized that this short-term research program will not
thoroughly explain the functions and responses of resources within the
Canyon, and that a long-term research and monitoring program is nec-
essary for evaluation of the EIS-selected alternative.
BACKGROUND: GLEN CANYON ENVIRONMENTAL
STUDIES I, 1982-1987
The Glen Canyon Environmental Studies (GCES I) were initiated in 1982
in response to potential changes in the Bureau of Reclamation's manage-
239
OCR for page 240
240
COLORADO RIVER ECOLOGY AlID DAM MANAGEMENT
ment of water flowing in the Colorado River through Glen Canyon Dam
because of upgrading of the dam's eight generators. The early history of the
Bureau was one of water storage for control of down stream flows, prima-
rily for irrigation. However, environmental concerns arising in the 1970s
raised questions about the Bureau's water management decisions, for ex-
ample, those dealing with operations of Glen Canyon Dam. Thus the Bureau
established the Glen Canyon Environmental Studies to develop data that
could be used to malice decisions on the operating criteria of the dam and the
environmental and legal requirements related to management of the Colo-
rado River.
GCES I, as a multi-agency effort, produced 33 technical reports based on
4-5 years of study. These reports were integrated into a composite final
report (USDI l98Sa) that addressed the question of how much impact the
present operations of Glen Canyon Dam had on the Grand Canyon ecosys-
tem, including downstream human activities. The executive summaries of
the technical reports were also combined into a single volume for ease of
reference (USDI, 1988b). The technical reports were presented in four ma-
jor groups, sediment, biology, recreation, and dam operations. The infor-
mation from each of these groups presented various levels of impact on
resources resulting from dam operations. GCES I was able to make a few
significant statements. These were:
Some aspects of the operation of Glen Canyon Dam have substantial
adverse effects on downstream environmental and recreational resources.
Flood releases cause damage to beaches and terrestrial resources. Un-
der current operations of the dam and lake storage, flood releases will occur
in about one of every four years.
Fluctuating releases primarily affect recreation and aquatic resources.
Modified operations could protect or enhance most resources.
In the end, it was realized that GCES I research had occurred during an
abnormal high water period and that the understanding of the relationships
between dam operations and downstream resources were incomplete.
DEVELOPMENT OF GLEN CANYON ENVIRONMENTAL
STUDIES II RESEARCH PROGRAM
In 1987, when GCES I had ended, there was concern that the research
program had not developed the information base necessary to evaluate the
operations of Glen Canyon Dam. Although the Glen Canyon Environmental
Studies Executive Review Committee had used the results of GCES I to
indicate that Glen Canyon Dam was causing an impact downstream, it did
not totally endorse some of the conclusions of GCES I and thought that
more research was necessary, especially on impacts of low-fluctuating flows,
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THE GCES PROGRAM: PAST, PRESENT, AND FUTURE...
241
endangered species, and power/recreation economics (USDI 1988c). The
request for more research under normal dam operating conditions for these
limited areas was supported by the Assistant Secretaries of Interior for
Water and Science, and Fish, Wildlife and Parks in June 198g.
At the time GCES I was being consolidated into a final report, a commit-
tee of the National Research Council's, Water Science and Technology
Board was funded by GCES I to review the whole program from research
initiation through the final integrated report. The report from this commit-
tee was completed at the same time as the Executive Review Committee's
report to the Secretary of Interior. The NRC review and recommendations
were a critical input to the future development of a research program on the
impacts of the operations of Glen Canyon Dam.
REVIEW OF GCES I BY THE NRC COMMITTEE
The 1986-1987 review of GCES I by the NRC, Water Science and Tech-
nology Board, Glen Canyon Environmental Studies Committee (National
Research Council, 1987) addressed inadequacies of the research program,
but also pointed out that GCES I had produced much valuable data that
would be useful to continued studies of the Grand Canyon ecosystem and
the operations of Glen Canyon Dam. Some of the major criticisms pre-
sented by the NRC committee include: (1) insufficient attention to early
planning, review of existing knowledge, and careful articulation of objec-
tives, (2) lack of distinction between science and management of the project,
with a need for a senior scientist and scientific oversight group established
at the beginning of the studies, (3) lack of soliciting the best scientific
talent to do the research, (4) inadequate consideration of economic conse-
quences of various management options, and (5) uncertain conversion of
research results into management options. The committee also stated that
ecological understanding of the system is paramount to making defendable
management decisions, the understanding in this case requiring a sustained
research effort because the river is in disequilibrium and operational deci-
sions will require continuous monitoring to ensure the desired environmen-
tal effects are being achieved.
Other pertinent points raised by the NRC committee were presented un-
der the various resources being studied in the Canyon. These include:
For aquatic resources: evaluate the quality of water at various potential
release levels in Lake Powell, include algal and invertebrate productivity in
future studies, perform focused studies on sediment movement, and develop
process-oriented models to understand sediments, water temperatures, nutri-
ent concentrations, and economic and power production.
For terrestrial biology: establish links to river productivity, and antici-
pate heterogeneity and match methods to temporal and spatial scales.
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242
COLORADO RIVER ECOLOGY AND DAM MANAGEMENT
· For sediment and hydrology: study tributary processes, include empiri-
cal approaches and modelling in hydrological studies, link sediment studies
to hydrological and biological monitoring, and institute geomorphic studies
to supplement hydraulic studies.
· For recreation: clarify cost/benefit tradeoffs between power generation
and recreation, broaden recreational constituencies, and avoid use of hypo-
thetical flows.
· For operations: initiate a feasibility study of changes in dam operations
and non-operation alternatives, and consider all management options.
INITIAL INTEGRATION PHASE OF GCES II
If GCES II was going to contribute to our understanding of the Grand
Canyon system, it had to develop a program that regarded the system as an
integrated whole, a point emphasized by the NRC committee. For example,
beach or sand bar aggradation or degradation is not only important as part
of a sediment dynamics study in the canyon, but it also is associated with
availability of backwaters for fish recruitment, or beaches for recreational
camping. The necessity of incorporating all of the activities and resources
in a comprehensive research plan required some form of integration of
researchers from the various disciplines studying the Grand Canyon or other
similar large river systems.
In July of 1989, over thirty five scientists and resource managers took a
2-week river trip through the Canyon with the explicit purpose of develop-
ing research needs for better understanding the Canyons ecological pro-
cesses and the human activities that impact and respond to these processes.
Working within the actual geographical setting enhanced the interchange
among the participants. There were those who came on the trip to espouse
a single concept or to protect a resource or preconceived idea. Fortunately,
the grandeur of the Canyon opened most minds and allowed a balanced
exchange amongst individuals from different backgrounds.
There were two goals of this river trip. The first was to develop research
questions by discipline, for example, what are the processes that control
eddy dynamics? The second was to have each discipline indicate the infor-
mation it might need from another discipline for a better understanding of
processes and responses within its area of interest.
By August 1989 a first draft research program had been developed. This
was the beginning of an iterative process with the final goal being a defini-
tive research program with hypotheses and research plans.
The August draft research program was considered too broad by most
participants. Too broad in the sense that it addressed most researchable
problems in the Canyon and was not specifically related to understanding
the impacts of the operations of Glen Canyon Dam. Some participants,
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THE GCES PROGRAM: PAST, PRESENT, AND FUTURE...
243
however, thought the August draft could have gone farther toward a total
ecosystem study of the Canyon based on the concept that in order to under-
stand the impacts, the total system should be thoroughly understood.
The initial research program for GCES II gave structure to identifying the
research needs. This was partitioned into three parts: (1) identification and
understanding of controlling variables within the system, (2) identification of
characteristics for crucial habitats of significant (high priority) resources or
resource uses, and (3) understanding the magnitude of the influence of the
controlling variables, in static or changing modes on the significant resources
or uses. Research guidelines for GCES II were established at this point. These
included (1) problem identification, (2) literature search, (3) problem refine-
ment, (4) research design, (5) research and analysis, and (6) monitoring.
The controlling variables were divided between those that are regulated
directly by the dam and its operations, and those that are regulated by other
factors in addition to dam operations. Dam dependent variables were such
factors as flow volume, flow fluctuations, ramping rates, and water quality
and temperature. Variables not associated directly with dam operations
were such factors as canyon geomorphology, sediment input and dynamics,
vegetation dynamics, nutrient dynamics, as well as anthropogenic variables
. . . .
such as recreat~ona activities.
Significant resources for which crucial habitat or environmental require-
ments need to be identified for research needs included: fish (exotic and
native, especially endangered species), aquatic food base, terrestrial vegeta-
tion, wildlife (especially threatened and endangered species), recreation,
cultural resources, water storage, and power production.
By expanding on the definitions of controlling variables and resource re-
quirements, information gaps were identified that would lead to research needs.
For example, for the dam-dependent variable "flow," the relationship between
the flow from the dam and flows at different points downstream are unknown,
or for the non-dam variable "sediment input," the contribution of sediment
from the many tributaries feeding into the Grand Canyon is unknown. Ex-
amples of gaps for resource requirements are: for fish, habitat requirements
for life stages and reproduction; or for cultural resources, requirements for
stability of archaeological sites near or below the high-water line.
The final phase of the first research program presentation was an integra-
tion of controlling and response variables. This took the form of (1) inter-
action among controlling variables such as flow and sediment dynamics,
and (2) resource response to controlling variables, such as fish habitat as a
function of flows.
After review of the first draft of the GCES II research program, it was
necessary to condense the program to points that might be useful in deci-
sion making in the managing the dam as well as other resources in the
Canyon. This became a necessity because decisions on dam operations
OCR for page 244
244
COLORADO RIVER ECOLOGY AND DAM MANAGEMENT
were now tied to an EIS, as of August 1989, and the time frame for infor-
mation gathering was initially set at a 2-year limit, a major reduction over
an earlier, 4-plus-year limit. To convince decision makers that many of the
resources and processes presented in the first draft of the research program
were part of decision making, that is, they connected the controlling vari-
ables to the crucial resource responses, a complex system diagram was
prepared (Figure 11-1) showing the various steps and processes between an
input or control variable and the desired state of a crucial variable. After
reviewing this figure, it becomes obvious that 2 years or less is an insuffi-
cient time frame to critically evaluate, through legitimate research, all re-
sponses between input (controlling variables) and the ultimate state of re-
source or use.
At this point, the Glen Canyon Environmental Studies research program
had reached a stage that required development of a double pronged ap-
proach. There was a need for a short-term research program that would
address the problems identified in the development of the initial research
program in order to achieve a data base that could be used to evaluate the
environmental consequences of the EIS alternatives. There was also a need
to develop a long-term research and monitoring program to enable a more
thorough development of ecosystem process models and to initiate a moni-
toring program that would be used to evaluate the dam operation alternative
selected through the EIS process. This long-term program is essential to the
success of the studies within the Grand Canyon, because the time necessary
to gain a high degree of confidence in the research models and results is
much greater than the time allotted for the short-term component of the
research program (Figure 11-2~. This does not mean that the short-term
research program should have been abandoned, but that our confidence in
the results from the short-term program will improve with the addition, over
. ~ . ~ .
time, ot more Information.
DEVELOPMENT OF SHORT-TERM RESEARCH HYPOTHESES
AND EXPERIMENTAL DESIGNS
The next step in development of the short-term research program was
development of short-term research questions that would lead to hypoth-
eses, again using an iterative process among Grand Canyon researchers and
resource managers. These questions were related to general issues dealing
with operations and management of Glen Canyon Dam and other resources,
a condensation of the control and response variables identified in an earlier
iteration of the research program. The general headings of these issues
were: (1) Effects of Dam Operations, (2) Effects of Recreation, (3) Effects
of Economic Balances, and (4) Potential Future Mitigation Alternatives in
Addition to Modification of Discharge Criteria.
OCR for page 245
245
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OCR for page 246
246
COLORADO RIVER ECOLOGY AND DAM MANAGEMENT
Flow Routing Model
(USGS)
Sediment Transport
Model (USGS)
Eddy Dynamics
Model (USGS)
Beach Erosion
Models (NPS)
Beach Surveys
(USGS)
Trophic Dynamics
Models (AGF,USGS)
Trout Stranding
(AGF)
Trout Population
Dynamics (AGF)
Eagle/Trout
Dynamics (BR,AGF)
Humpback Chub
Conserv. Meas.
(FWS, AGF, BR)
Cultural Resources
Responses
Recreation Response
and Impact Models
1990 1991 1992 1993 1994 1995 1996--
/ / / / / / / /
_______-------?
/ ( x ——_ _ _ _ _
Lees Ferry Angler --------------X
Access (BR subcont.)
Economic Models --------------X
(BR subcont.)
/
_ _
1990 1991 1992 1993 1994 1995 1996--
/ / / /
/
Mitigation
No change alternat.
Evaluation
Variable intake
Structure
Reregulation Dam
Beach Stabiliz.
Sediment Augment.
/ = research initiated
- - - - research ongoing or continued as monitoring
------- intensive research program
X = data and analysis at stage to be useful to EIS, (
? = data questionable whether useful to EIS
FIGURE 11-2 Anticipated research schedule and data usability.
)=incomplete
OCR for page 247
THE GOES PROGRAM: PAST, PRESENT, AND FUTURE...
247
The following listing of the short-term research questions (Table 11-1)
were developed based on general justification and information needs state-
ments. Research proposals addressing these questions have been prepared
by scientists from different agencies, for example, US Geological Survey,
National Park Service, Arizona Game and Fish Department, and the Bureau
of Reclamation. Some of the economic and endangered fish species re-
search will be done by non-agency scientists through development of pro-
posals responding to Bureau of Reclamation "Request for Proposals" (RFPs).
DEVELOPMENT OF CONTROLLED RESEARCH DISCHARGES
FROM GLEN CANYON DAM
Answering the questions and developing response curves and models for
the resources in the Canyon require conditions more controlled' than the
widely fluctuating daily (and seasonally) discharge flows from Glen Can-
yon Dam. Controlled research discharge flows are an obvious necessity.
The duration of the controlled discharges should be sufficient for the sys-
tem to reach an equilibrium with the discharge. A compromise was made to
use a 2-week period, although most scientists agreed that a 4-week period
was preferable. A dendrogram was used to determine the minimum number
of research discharges (Figure 11-3~. These were then placed into a sched-
ule to satisfy downstream water release requirements, and recreation and
power network considerations (Figure 11-4~. The research discharges in-
cluded not only controlled regular fluctuations, but also constant discharge
flows (with volumes equivalent to fluctuating discharges), and normal
operations fluctuating discharges (based on the same time period from 1989~.
The only replication of controlled discharges are the first two in July 1990
and July 1991 (see Figure 11-4~. If three replications were run for each
controlled discharge, the duration for each was increased to 4 weeks, and
additional discharges were selected to better test all variables, the research
discharge period would last approximately 18 years. This is obviously
unacceptable to all concerned. The compromise, for the meantime, has
been a composite period of approximately 6 months of controlled discharges.
This, perhaps, is erring on the short side. Results from the research under-
taken during the controlled discharges will be evaluated with this in mind.
DEVELOPMENT OF LONG-TERM RESEARCH AND
MONITORING NEEDS
Any short-term study of an ecosystem as complex as the Grand Canyon
is bound to be a failure if the research is viewed as the final answer to
understanding the system. The short-term study explained above was de-
veloped primarily to address potential EIS alternatives, not to fully under-
OCR for page 248
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OCR for page 249
THE GOES PROGRAM: PAST, PRESENT, AND FUTURE...
TABLE 11-1 Continued...
249
Q-ll.la. Does fishing activity, including boating, affect beach stability, especially in the
Lee's Ferry reach?
Q-ll.lb. What is the relationship between the trout population of the Lee's Ferry reach and
fishing activities, especially catch and release or keep relationships?
B. Effects of rafting and Camping Activities.
Q-12.1. How does rafting and camping affect other Canyon resources, especially the sedi-
ment volume of beaches?
III. Effects of Economic Balances.
A. Power Economics.
Q-13.1. If creating a more stable environment in the Canyon below Glen Canyon Dam
requires changes in power operations, what is the economic impact of these changes?
B. Recreational Economics.
Q-14.1. Are the economic benefits of downstream recreational activities as well as associ-
ated tourism services (e.g., lodging, airlines, restaurants, etc.) affected by operations of Glen
Canyon Dam?
C. Non-use Economics.
Q-15.1. Are there any non-use benefits that are attributable
environment in the Canyon below Glen Canyon Dam and if so would these values be affected
by changes in dam operations?
to the maintenance of a stable
IV. Potential Future Mitigation Alternatives in Addition to Modification of Discharge
Criteria.
A. Effects of "No Change" Altemative.
Q-16.1. Are there any greater economic or environmental costs to the "no change" alterna-
tive if compared to the other alternatives?
B. Effects of Variable Intake Structures
Q-17.1. If a variable intake structure is used on Glen Canyon Dam, what will be the effects
of intake at various levels on the downstream system?
C. Effects of A Reregulation Dam.
Q-18.1. If a regulation dam were constructed in the Canyon some where between Glen
Canyon Dam and Lee's Ferry, what would be the effects of the discharges from this dam on
the downstream system?
Q-18.2. What would be the impact of a reregulation dam on the Lee's Ferry reach if it is
constructed in this reach?
D. Effects of Beach Protection Devices.
Q-19.1. Is it possible to mitigate the degradation of camping beaches in the Canyon due to
dam operations using beach protection devices?
E. Effects of Sediment Augmentation.
No questions have been developed until methodology is identified.
OCR for page 250
248
COLORADO RIVER ECOLOGY AND Do MANAGEMENT
TABLE 11-1 Outline of Short-term Research Questions for Analyzing
Resource Responses.
I. Effects of Dam Operations
A. Effects of the Magnitude of Daily Discharge Fluctuations, Minimum Discharges, and
Rate of Change (Ramping) of Fluctuating Discharges.
Q-1.1. How significant are discharge fluctuations, minimum discharge and ramping in the
degradation or aggradation of beaches?
Q-2.1. Do discharge fluctuations, differences in minimum discharges, or different rates of
change in daily discharges (ramping rates) interact withother uses and components of the
Canyon to affect rates of sediment degradation?
Q-2.1a. What is the relationship between the effects of recreational use of beaches and the
magnitude in daily discharge fluctuations, daily discharge minima, or daily ramping rates?
Q-2.1b. What is the relationship between the role of vegetation as a beach stabilizer and the
magnitude of daily discharge fluctuations?
Q-3.1. How do daily discharge fluctuations, minimum discharges or ramping rates influence
the amount of sediment stored in or transported in the Canyon system?
Q-4.1. How do discharge fluctuations, minimum discharges and rates of change of fluctuat-
ing discharges affect trout?
Q-4.1a. What is the relationship between the rate of stranding of trout and the magnitude of
discharge fluctuations, minimum discharges, or the ramping rates?
Q-4.1b. What is the relationship between behavioral activity of rainbow trout and the mag-
nitude of daily discharge fluctuations, daily minimum discharges and ramping rates?
Q-5.1. How do discharge fluctuations, minimum discharges and rates of change of fluctuat-
ing discharges affect foraging success of wintering bald eagles?
Q-5.la. What is the relationship between trout availability, trout access, bald eagle presence,
bald eagle abundance or bald eagle foraging success in the mainstream or Nankoweap Creek
and the magnitude of daily discharges?
Q-6.1. How do dischare fluctuations and rates of change in fluctuating discharges affect the
population dynamics (including short-term abundance of early life stages and potential preda-
tion relationships) of native (especially the humpback chub) and introduced fish species in the
mainstem Colorado, including main stem backwaters and the confluence of the Little Colorado?
Q-7.1. How are water quality (nutrient availability and other characteristics), stream produc-
tivity (of algae and macroinvertebrates), and import-export rates or organic matter to and from
the Lee's Ferry reach influenced by the magnitude of discharge fluctuations, and the ramping
rates?
Q-8.1. How are recreational variables (angler safety and rafting safety, satisfaction, experi-
ential quality and economics) influenced by the magnitude of seasonal or daily discharge
fluctuations, minimum discharges or the ramping rates?
Q-9.1. Are there sufficient camping beaches during maximum normal operations discharges
from Glen Canyon Dam (i.e., 31,500 or 33,200 cfs) to satisfy the needs of the recreational
rafting community based on the NPS acceptable carrying capacity of the Grand Canyon system?
Q-10.1. Do dam operations (e.g., magnitude of stage, magnitude of discharge fluctuations
and/or ramping rates) affect the stability of cultural resource sites along the river in the Grand
Canyon?
II. Effects of Recreation.
A. Effects of Fishing Activities.
Q-11.1. Does fishing activity, including boating, in the Lee's Ferry reach affect other Can-
yon resources?
OCR for page 251
THE GOES PROGRAM: PAST. PRESENT, AND FUTURE...
30
u,
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o 20
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Hign
1 4
~ High
(8,000 cfs
Constant
(1 1,000 cfs)
Constant
28 2 1216 2630 1317 271 1115 2529 8 12 13 172731
June July August September October November December
Constant Flows _ Minimum Flows ~ Maximum Flows
High High
High High High High
High
31 1014 2428 7 11 1822
(1 5,000 cts)
Constant
2 6 1620 303
271 1115 2526
January February March April May June July
~ Constant Flows _ Minimum Flows t~ Maximum Flows
FIGURE 11-4 Research discharge flow schedules for 1990 and 1991.
stand all of the processes going on within the Canyon. As a result, it has
limitations, of which one of the most important may be misleading interpre-
tation of data. This can be avoided only if those doing the interpretation
recognize the limitation and place a wide band of uncertainty around their
conclusions.
EXPANSION OF THE SHORT-TERM RESEARCH PROGRAM
To ensure an adequate understanding of the Grand Canyon ecosystem,
the short-term research program must be continued in those areas for which
OCR for page 252
252
COLORADO RIVER ECOLOGY AND DAM MANAGEMENT
long-term data is essential. Models and response curves can be adequately
developed for some of the resources in a relatively short period of time, for
example, some of the economic models and recreational responses. Models
of other processes, such as sediment transport, eddy dynamics, and hump-
back chub population dynamics, require a much longer period of data col-
lection than that allotted under the short-term research program, even with
controlled, research discharges from the dam. The short-term research data,
along with those data generated under GCES I, can only be used, in areas
where long-term data are needed, to guide decision making in the EIS pro-
cess. This does not mean these data will not be useful, they will be useful
with limitations.
The need for an expanded research program can clearly be seen in Figure
11-2 which shows estimates of the time needed to generate useful informa-
tion for a thorough understanding of the Canyon system. This information
will be a necessary input into the understanding of the data generated from
a long-term monitoring program, a program essential to evaluating the ac-
curacy of the EIS decision-making process.
LONG-TERM MONITORING
A long-term monitoring program should be started along with the present
short-term research program and should continue, along with the long-term
research program, for some time after completion of the EIS. Monitoring is
used to determine the state of resources as well as their response to existing
conditions. Changes in the state of a resource indicates a beneficial or
detrimental response to controlling variables, such as dam operations. It is
the understanding of these changes for which the short and long term re-
search data will be used.
The long-term monitoring program should be organized in such a way as
to assure valid determination of changes taking place in the Canyon. This
means a regular schedule of measurements of both the sensitive and non-
sensitive resources. Some resources, such as camping beaches, should be
measured at least twice a year, while others, such as trout spawning and
stranding, might be measured just during that season when the response is
greatest. The resources to be monitored, as well as the timing and location
of monitoring, should be determined from data collected during GCES I,
GCES II and the long-term extension of the short-term GCES II studies.
However, monitoring should not wait until all crucial resources are identi-
fied and thoroughly understood or else some of these resources may be
permanently degraded or lost from the Canyon.
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CONCLUSIONS
The research program that has been ongoing in the Grand Canyon is
probably inadequate to thoroughly understand all of the functions of the
Canyon ecosystem. The program continues to develop and become more
integrated and sophisticated. There is increasing recognition that a longer
term research program is essential to develop the data that will allow an
adequate understanding of resource responses identified by a monitoring
program. It is also recognized that the monitoring program should be started
during the present short-term studies and that it should be a complex, data
rich program Hat will continue for years (a decade or more) after the completion
of the EIS, in order to evaluate the consequences of the selected EIS alter-
native for dam and Canyon management.
The Grand Canyon ecosystem is an unique resource that we should make
every effort to understand and protect.
REFERENCES
National Research Council. 1987. River and Dam Management: A Review of the Bureau of
Reclamation's Glen Canyon Environmental Studies. Water Science and Technology Board.
National Academy Press, Washington, D.C.
U.S. Department of Interior. 1988a. Glen Canyon Environmental Studies Report. Bureau of
Reclamation, Flagstaff, Ariz.
U.S. Department of Interior. 1988b. Glen Canyon Environmental Studies, Executive Summa-
ries of Technical Reports. Bureau of Reclamation, Flagstaff, Ariz.
U.S. Department of Interior. 1988c. Glen Canyon Environmental Studies, Executive Review
Committee final report. Bureau of Reclamation, Salt Lake City, Utah.
Representative terms from entire chapter:
canyon dam
