9628

• UCREFRP Catalog Number: 9628
• Author: Gloss, S. P., J. E. Lovich and T. S. Melis.
• Title: The State of the Colorado River Ecosystem in Grand Canyon - A Report of the Grand Canyon Monitoring and Research Center 1991-2004.
• USFW Year: 2005.
• USFW - Doc Type: \
• Copyright Material: NO

of the ecosystem, including the economic importance of
the ecosystem, hydroelectric power generation, cultural
resources, and camping beaches. In each case, the infor-
mation is then used to discuss the management options
available to decision makers and the public based on the
best scientific information available. In large measure,
this report represents the first comprehensive assessment
of how effectively the MLFF alternative is allowing the
Secretary of the Interior to meet the resource manage-
ment goals of the Grand Canyon Protection Act of 1992.

Place Names and Units

Throughout the report, "Grand Canyon" is used
broadly to refer to the Colorado River corridor between
Glen Canyon Dam and the western boundary of Grand
Canyon National Park, including Glen, l\hrble, and
Grand Canyons. The study area is referred to as the
"Grand Canyon ecosystem." The Colorado River is
discussed in terms of four distinct sections: Lees Ferry

1982 Glen Canyon Environmental
Studies created to study effects
of Glen Canyon Dam operations

1983 Glen Canyon Dam releases more
than 92,000 cfs to stop Lake Powell
from overtopping Glen Canyon Dam

Overview 11

reach, Marble Canyon, upper Grand Canyon, and lower
Grand Canyon. The "Lees ferry reach" extends from the
downstream end of Glen Canyon Dam to Lees Ferry, and
"l\iIarble Canyon" extends from Lees Ferry to the mouth
of the Little Colorado River. For this report, "upper
Grand Canyon" refers to the river corridor that extends
from the mouth of the Little Colorado River to the Grand
Canyon gaging station (Topping and others, 2003), while
"lower Grand Canyon" extends from the Grand Canyon
gaging station to the western boundary of the park.
In this report, U.S. customary units are used for all
measurements to facilitate understanding by the general
reader. Metric equivalents are provided in parentheses
after the U.S. customary units for all measurements except
for river now, the standard measure of which is cubic
feet per second, and river mile, which is used to describe
distances along the Colorado River in Grand Canyon
(Stevens, 1990). The use of the river mile has a histori-
cal precedent and provides a reproducible method for
describing location: Lees Ferry is the starting point, as

1984 One of the last razorback
suckers (Xyrauchen texanus)
seen in Grand Canyon is caught
and released at Bass Rapids

1987 National Research Council completes
review of Glen Canyon Environmental Studies,
publishing River and Dam Management: a
Review of the Bureau of Reclamations Glen
Canyon Environmental Studies