|
<br />Allowable Daily Flow Fluctuations - 5,000 cfs/24 hours for monthly release volumes less
<br />than 600,000 acre-feet, 6,000 cfs!24 hours for monthly release volumes of 600,000 to
<br />800,000 acre-feet, and 8,000 cfs!24 hours for monthly release volumes over 8,000 acre-feet.
<br />
<br />,',
<br />,~ I
<br />
<br />::
<br />
<br />"
<br />,
<br />
<br />Maximum Ramp Rates - 4,000 cfslhr when increasing, and 1,500 cfslhr when decreasing.
<br />
<br />";
<br />
<br />Emeriencv Exception Criteria - Normal powerplant operations will be altered temporarily
<br />to respond to emergencies. These changes in operations typically would be of short duration
<br />(usually less than 4 hours) and would be the result of emergencies at the dam or within the
<br />interconnected electrical system. Examples of system emergencies include:
<br />
<br />,,:
<br />
<br />'.>.
<br />
<br />I. Insufficient generating capacity
<br />
<br />2. Transmission system: overload, voltage control, and frequency
<br />
<br />~
<br />';<,
<br />~~
<br />
<br />3. System restoration
<br />
<br />J
<br />~
<br />','
<br />~
<br />~
<br />
<br />4. Humanitarian situations (search and rescue)
<br />
<br />"
<br />(~:
<br />
<br />Flood Frequencv Reduction Measures - The frequency of unanticipated flood flows in
<br />excess of 45,000 cfs will be reduced to no more than I year in 100 years as a long-term
<br />average. This will be accomplished initially through the Annual Operating Plan 'process and
<br />eventually by raising the height of the spillway gates at Glen Canyon Dam 4,5 feet.
<br />
<br />,',"
<br />
<br />,,;
<br />
<br />"
<br />;";..
<br />"
<br />
<br />"
<br />
<br />Habitat Maintenance Flows - Habitat maintenance flows are high steady releases within
<br />powerplant capacity (33,200 cfs) not to exceed 14 days in March, although other months will
<br />be considered under the AMP. Actual powerplant release capacity may be less than 33,200
<br />cfs under low reservoir conditions. These flows will not be scheduled when projected storage
<br />in Lake Powell on January 1 is greater than 19,000,000 acre-feet, and typically would occur
<br />when annual releases are at or near the minimum objective release of 8,230,000 acre-feet.
<br />Habitat maintenance flows differ from beach/habitat-building flows because they will be
<br />within powerplant capacity, and will occur nearly every year when the reservoir is low.
<br />
<br />)..~
<br />
<br />t-.
<br />
<br />:.:':
<br />-".';'
<br />
<br />',.
<br />:~">i:
<br />,
<br />: ~}
<br />
<br />~~
<br />~~t
<br />,....,
<br />
<br />Beacbmabitat-Buildin~ Flows - These controlled floods will occur as described in the EIS
<br />(steady flows not to exceed 45,000 cfs, duration not to exceed 14 days, up-ramp rates not to
<br />exceed 4,000 cfslhr, and down-ramp rates not to exceed 1,500 cfs/hr) except instead of
<br />conducting them in years in which Lake Powell storage is low on January 1, they will be
<br />accomplished by utilizing reservoir releases in excess of powerplant capacity required for
<br />dam safety purposes. Such releases are consistent with the 1956 Colorado River Storage
<br />Project Act, the 1968 Colorado River Basin Project Act, and the 1992 Grand Canyon
<br />Protection Act.
<br />
<br />~'~
<br />~~
<br />,':">;.
<br />:'~
<br />
<br /><:;-
<br />
<br />I
<br />
<br />Is! Bruce Babbitt
<br />Secretary of the Interior
<br />
<br />February 24.1997
<br />Date
<br />
|