8128

• UCREFRP Catalog Number: 8128
• Author: U.S. Bureau of Reclamation.
• Title: Operation of Glen Canyon Dam\
• USFW Year: 1995.
• Copyright Material: NO

Description of Alternatives
the Year-Round Steady Flow Alternative and to retain the pattern of
historic monthly releases under the Existing Monthly Volume Steady Flow
Alternative.
Existing Monthly Volume Steady Flow Alternative
Minimum Maximum Allowable daily Ramp
releases releases fluctuations rate
(cfs) (cfs) (cfs/24 hrs) (cfs/day)
8,000 Monthly ±1,000 2,000 between
volumes months
prorated
Minimum
Flow
Monthly Release
Volume
The Existing Monthly Volume Steady Flow Alternative was developed to
provide steady flow on a monthly basis while continuing to maintain
flexible monthly release volumes to avoid spills and maintain conservation
storage. Steady flows were included each month with the goal of
protecting or enhancing downstream resources, especially the aquatic
ecosystem that exists downstream from the dam.
This alternative would have the same annual and monthly operating plan
as the No Action Alternative, but releases would be steady within months.
Also, beach/habitat-building flows would modify monthly release
volumes when Lake Powell is drawn down.
Both minimum and maximum flows would be within plus or minus
1,000 cfs of the mean monthly release. Based on analysis of historical
releases, minimum flows rarely would be below 8,000 cfs (476,000-acre-
foot monthly volume).
The scheduled monthly release volumes would be the same as the
monthly volumes under the No Action Alternative. Based on the
period 1963-89, February has the lowest monthly median release volume
(556,000 acre-feet---equivalent to 10,000 cfs), and August has the highest
monthly median release volume (903,000 acre-feet-equivalent to
14,700 cfs).
Glen Canyon Dam EIS Summary 29