BOARD01350

• Board Meeting Date: 1/24/2006
• Description: WSP Section - Colorado River Issues - Development of Opearations for Lakes Powell and Mead under Low Reservoir Conditions, including the Development of Lower Basin Shortage Criteria
• Board Meetings - Doc Type: Memo

.

.

.

Modeling of Reservoir Management Strategies
for Lakes Powell and Mead

Figure ~-15
Probability of Lake ~Icad Elcution Below 1000

'''"'

~

~-

,
_N<YmII.SoflllSl>cwtClr9nai
__~ClngonaI.SoflllSl>onOng.nal
--I-!>plIlOr9M!-SlapSl>on"""
_H)Ot'Id~.Sl""SI>onrW2
~H;bn<l~I.SlepSl>on..,..r.l
~ =

-1
- ~

.", -I

"'"
l "'"
! ""
,
,
il "'"
,
~ ",.,
.
~
< "'"
"'"
",.,

~

j--
-+-

'"'
''''''

~

2010

"'''
C.I"ndarYe.r

"''''

2025

Figure 4-15 shows the probability of Lake Mead dropping below 1000 ft. The probability of Lake I\-tcad
going below 1000 fl is first observed in 2016 under Step Shortage Original. olle year carlier than under
the Step Shortage revisions.

4.2.2 Summary of Findings
Based on the Step Shortage revisions that were tested. a key finding is that Lake ~kad is more sensitive
to the elevation at which a shortage starts rather than the pattern of shortage.

4.3 Hybrid with Step Shortage rev1

After studying the results of the two sensitivity analyses presented in this section, the Technical
Commiuee detemlined that balancing releases should not be made from lake Powell before a shortage
had been triggered in the lo\ver Basin. With this in mind. a sensitivity analysis was perfomled that
examined the Hybrid strategies combined with the Step Shortage revl strategy. Under Step Shortage
rev! a shortage is first triggered at a Lake Mead elevation of 1100 11. This ensures that balancing
releases occur I) at the same time as a lower Basin shortage as in Hybrid revl and red or 2) al1er a
Lower Basin shortage has been triggered as in Hybrid Original and rev2.

29

Working Oral!. \'crsion 2. January. 2006