BOARD00004

• Board Meeting Date: 1/26/2000
• Description: WSP Section - Colorado River Basin Issues - Glen Canyon Adaptive Management Program - Proposed Hydrologic Trigger for Releases in Excess of Glen Canyon Power Plant Capacity ‎(Informational Item)‎
• Board Meetings - Doc Type: Memo

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STATE OF COLORADO

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Colorado Water Conservation Board

Department afNatural Resources
1313 Sherman Street, Room 721
Denver, Colorado 80203
Phon" [phone]
FAX, [phone] MEMORANDUM

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TO:

Colorado Water Conservation Board Members

Bill Owens
Governor

FROM:

Randy Seaholm ~
Chief, Interstate Streams Investigations

Greg E.Walcher
Executive Director

Peter H. Evans
eWeB Director

DATE:

January 14,2000

Dan McAuliffe
Deputy Director

SUBJECT: Agenda Item 23h, January 26-27, 2000 Board Meeting-
Colorado River Basin Issues - Glen Canyon Adaptive Management
Program - Proposed Hydrologic Trigger for Releases ,in Excess of Glen
Canyon Power Plant Capacity (Informational Item)

Backl!:round

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The Glen Canyon Adaptive Management Program has adopted hydrologic triggering
criteria which when exceeded will allow a "Beach Habitat Building Flow" (BHBF or
Spike Flow) to occur. The triggers are as foIlows:

· Storage in Lake Powell exceeds target storage of21.5 million acre-feet; or
· The January I forecast for unregulated spring inflow into Lake Powell for the
January-July period exceeds 13 million acre-feet (about 140 % ofnonnal); or
· Releases from Glen Canyon will exceed 1.5 million acre-feet for the month.

When these triggers are exceeded, releases are allowed to go up to 45,000 cfs under the
Glen Canyon Environmental Impact Statement-Record of Decision for the purpose of
moving sediment out of the main channel and up on to the banks fonning new beaches in
Grand Canyon. A BHBF release of 45,000 cfs exceeds the power plant release capacity
of approximately 31,500 cfs.

The states strongly resisted allowing the first BHBF to occur, but finally relented on the
basis that this was a one-time occurrence for research purposes unless the hydrologic
triggers subsequently developed and listed above were exceeded. The hydrologic triggers
are such that Lake Powell is virtually guaranteed to be at or above target storage (21.5
million acre-feet as opposed to 25 million acre-feet, which is full) and that a release to
avoid uncontrolled spills from the reservoir is likely required. These criteria are such that
inflow to Lake Powell must be on the order of 140% of nonnal for a BHBF to occur.
Furthennore, these criteria are such that no BHBF has been triggered since the" test
. flow" in 1996 even though the reservoirs have been fairly full and the Upper Basin