7423

• UCREFRP Catalog Number: 7423
• Author: U.S. Bureau of Reclamation.
• Title: Glen Canyon Environmental Studies Draft Report, September 1987.
• USFW Year: 1987.
• USFW - Doc Type: Washington, D.C.
• Copyright Material: NO

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Summary of Annual. Monthlv. and Hourlv Operations. The
following discussion and Table V-1 summarize the
considerations in developing annual, monthly, and
hourly water release schedules.

The volume of water released from Lake Powell each
month depends on the forecasted inflow, the annual
storage targets, and annual release requirements.
Demand for electrical energy is also considered and
accommodated as long as storage requirements are not
affected. Generally, fall and winter releases are
designed to meet the January 1 storage target. January
through July releases are scheduled to create space in
the reservoir so that the forecasted runoff will not
produce spills and will fill the reservoir in July.
Spring releases are designed to accommodate the
changes in inflow as they occur. July through
September releases are used to compensate for any
missed targets and to take aim on the January 1 target
of 22.6 maf of storage.

After these considerations have been satisfied, and if
there is any flexibility remaining to adjust monthly
releases, 'then seasonal variations in the power demand
may be considered. Power demand is highest during the
winter and the summer months. Therefore, higher
releases to generate more electricity are scheduled in
these months whenever possible. Greatest flexibility
to match monthly releases to power demand exists in
years of moderate runoff and reservoir conditions. If
minimum releases are required because of low reservoir
conditions or low expected inflow, there remains little
flexibility to accommodate changing power demands.
Likewise, if the reservoir is near full or the runoff
is extremely high, monthly releases are scheduled at or
near maximum capacity most of the time, again leaving
little flexibility for power generation.

Hourly releases are set to reach the monthly release
volumes, to maintain established minimum rates, and to
follow the pattern of energy demand. Demand for power
may change the rate at which water is released, but it
is never allowed to change the monthly volume of
release. Minimum releases currently maintained are
1,000 cfs during the winter and 3,000 cfs in summer.

Emergency conditions, such as river search and rescue
or failures in equipment, may cause severe departures
from the expected schedules. Generally these
departures are short~lived and the effects on water
conservation can be mitigated in a short time.