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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Agenda Item 23h .GCAMP
January 14, 2000
Page 2 of3

release to the Lower Basin has been 10.5 million acre-feet or more; will in excess of the
8.23 million acre-feet presently required under the operating criteria.

Issue

The Grand Canyon Monitoring and Research Center (GCMRC) and others on the
Adaptive Management Work Group (AMWG) would like to take advantage of high
reservoir storage conditions in Lake Powell and are looking for a way to make another
BHBF or to cause a research flow in excess of the 45,000 cfs release allowed under the
Record of Decision. A release of approximately 48,000 cfs is the most that can be made
from Glen Canyon (8 generators and 4 bypass tubes running full) without using the
emergency spillways. The minimum release that can be made through the emergency
spillway gates on one side is about 7,000 cfs (Both gates on one side have to be opened
enough to allow for proper operation and generate the swiping action at the outlet).

Ontion

A forth criteria could be added to the "Hydrologic Triggers" presently in place. The
additional criteria would go something like this.

· Ifreleases from Glen Canyon Dam are projected to be in excess of 10.5
million acre feet for the water year after receiving the April I forecast, and
development of a 1.12 million acre foot release month is possible without
reducing hydropower releases below a set amount (suggest 8,000 cfs as a
minimum). A BHBF with a peak of no more 45,000 cfs is possible and may
be made for research purposes; so long as such release does not increase the
projected volume to be released from Lake Powell during the remainder of
that water year.

Discussion

It requires approximately 1.12 million acre-feet during a given month' to generate a
45,000 cfs peak with any type ofrealistic ramping rates up to and down from that peak
and to maintain an acceptable baseflow during the remainder of that month for power
generation purposes. Attached is the Lake Powell page from a recent 24-month study
and a potential release hydro graph for a 1.12 million acre-foot month that demonstrates
the opportunity that exists. The downside too this proposal is that we are providing yet
another way for water to bypass the power plant at Glen Canyon, which we have
maintained, is contrary to the law of the river. Conversely, this proposal would be
consistent with the goals of the 1992 Grand Canyon Protection Act and it would support
the efforts of the GCMRC at a time when reservoir conditions are fairly full without
increasing the risk to upper basin water supply protection. The only losses are the
hydropower generation and revenue from water that bypasses the power plant.