Conjunctive Use Model S-1

• Description: Conjunctive Use Model S-1
• State: CO
• Title: Conjunctive Use Model S-1
• Water Supply Pro - Doc Type: Report/Study

Conjunctive Use Model S -1
The Basin States Technical Team requested that Reclamation develop a conjunctive use
model in CRSS /Riverware, based on discussions at the meeting held in Phoenix on
January 21, 2005 and subsequent verbal communication between Technical Team
members from the Colorado River Basin States and Reclamation.
This model allows the annual release from Lake Powell to be reduced below 8.23 maf
under specified circumstances. This model also imposes a temporary equalization level
(at a level below 602(a) storage) at Lake Powell once annual releases have been reduced
below 8.23 maf. This model has been named S -l. The model builds off the work
Reclamation has put into the H -1 model which followed the logic used by the Central
Arizona Project (Henning et al) in their Interim Lake Powell Release Trigger spreadsheet
model.
A description of the algorithms and logic used in the S -1 model are contained in this
document. The S -1 model has been developed in CRSS/RiverWare (monthly model) and
also in CRSS light (annual model). S -1 uses Absolute Protection of 1,000 feet at Lake
Mead as the Lower Basin shortage strategy.
The S -1 model includes four adjustable parameters.
• Lake Powell Trigger (LPT) Elevation 9I 71.5'
Elevation trigger for reducing annual releases from Lake Powell
• Reduced Objective Minimum (ROM) release from Lake Powell e,/ k � �' " 7. 4Y
Annual release volume from Lake Powell when Lake Powell is below the
LPT Elevation and Lake Mead is above the Water Supply Trigger (WST)
elevation
• Water Supply Trigger (WST) Elevation at Lake Mead ie
Elevation trigger for abandoning the ROM release and returning to the
objective to release a minimum of 8.23 maf from Lake Powell
• Temporary Equalization Level at Lake Powell (TEL)>
Temporary equalization level at Lake Powell, a level that is below 602(a)
Storage
These four parameters in S -1 are all adjustable, to accommodate the investigation of
impacts on the Colorado River System under various combinations of values for these
four parameters.
Reclamation has run the model using two different LPT elevations: 3,560 feet and 3,575
feet. When Lake Powell is projected to be below the LPT elevation, on September 30,
the S -1 model reduces releases from Lake Powell below 8.23 maf to the ROM release
(unless Lake Mead is below the water supply trigger elevation).