Summary Report ‎(Working Draft)‎ Modeling of Reservoir Management Strategies for Lakes Powell and Mead December 2005

• Description: Summary Report ‎(Working Draft)‎ Modeling of Reservoir Management Strategies for Lakes Powell and Mead December 2005
• State: CO
• Title: Summary Report ‎(Working Draft)‎ Modeling of Reservoir Management Strategies for Lakes Powell and Mead December 2005
• Water Supply Pro - Doc Type: Meeting

Modeling Results for
Colorado River Basin States' Modeling of
Colorado River and Reservoir Management Strategies
Step Shortage revision 1 incorporated an additional shortage step at Mead
elevation 1100 and modified the shortage pattern from the original. It was the
most aggressive step shortage strategy studied. Step Shortage revision 2 had an
additional shortage step at Mead elevation 1100 with the same shortage pattern as
the original below 1075. Step Shortage revision 3 had an additional shortage step
at Mead elevation 1100 with a slightly more aggressive shortage pattern than the
original below 1075.
2.1.2 Absolute Protection of Mead Elevation 1000 ft
The Absolute Protection strategy was done as a sensitivity analysis to the Step
Shortage approach. The objective of Absolute Protection is to keep Mead's water
level at or above a key elevation essentially 100 percent of the time. The concept
of protecting Mead at 1000 ft was introduced as an operational strategy at low
reservoir levels in the ISG -FEIS (Volume II, Attachment J) as "Level 2" shortage.
Mead elevation 1000 ft is the minimum water level for operating the lower intake
of the Southern Nevada Water Authority.
Under this strategy, shortages are applied in any year when Mead is projected to
be below 1000 ft at the end of the year. A mass balance is performed at the
beginning of the year to determine the quantity of water available for delivery to
keep Mead above 1000 ft. The amount of shortage is the difference between total
demands from Mead and the quantity of water available. The tradeoff is you take
larger shortages less often; whereas the Step Shortage approach takes smaller,
more manageable shortages more often.
2.2 Coordinated Management between Basins
It has been observed that when entering a drought Powell drops faster than Mead
because inflow is less than the minimum objective release. When coming out of a
drought, Powell recovers much quicker than Mead because inflows are greater
than the minimum objective release. Mead continues to decline until Powell has
recovered enough to make equalization releases. It is during the onset and
recovery of drought where an alternate operation may help both reservoirs.
Many operational strategies at Powell were studied. Of these, there were four
main concepts: Normal operations, Tiered Release, Balancing and Hybrid. This
section describes each of these concepts.
2.2.1 Powell Normal Operations
Powell is operated in accordance with the Long -Range Operating Criteria. Under
normal operations, Powell will equalize according to the 602(a) algorithm, or
release the 8.23 MAF minimum objective release if the 602(a) criterion is not
met. Details on Powell normal operations are located in Appendix C.
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