WSP11719

• File Number: 8220.101.10.D
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 10/19/1994
• Title: CWCB Agenda Item 21 ‎(c)‎ - Experimental Flow ‎(Spike Release)‎ - Flood Frequency Reduction
• Water Supply Pro - Doc Type: Board Memo

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OffICE OF THE EXKUTIVE DIRECTOR

STATE OF COLORADO

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Department of Natural Resources
131 ) Sherman Street. Room 71 B
Denver, Colorado 80203
Phone, [phone]
TOO, (3031 866.3543
fAX, 13031 866-2115

DEPARTMENT OF
NATURAL
RESOURCES

September 23, 1994

Roy Romer
Cove"""
lames S. Lochhead
Executive DiteccO(

Charles A. Calhoun
Bureau of Reclamation
Upper Colorado Regional Office
125 South State street, Room 6107
Salt Lake city UT 84138-1102

Ronald w. Catt.1ny
Deputy Director

Re: Glen Canyon Dam operations

Dear Charlie:

It has recently come to my attention that, in response to comments
to the DEIS on Glen Canyon Dam Operations, the Bureau of
Reclamation is contemplating modifying the preferred alternative
identified in the DEIS. This modification would eliminate the
proposed permanent installation of flashboards at the Dam.
Instead, the Bureau would reduce' "flood frequency" by reserving
additional exclusive flood control space in the reservoir, using
lower storage levels. The term "flood frequency" is used as
shorthand to refer to operations under section 602{a)(3) (iii) of
the 1968 Colorado River Basin Project Act, which requires that the
Secretary avoid anticipated spills from Lake Powell (there is no
authorized flood control function for Glen Canyon Dam) .

The state of Colorado has previously commented on this aspect of
the preferred alternative in its April 11, 1994, letter to
Reclamation on the DEIS. Colorado recognized that reserving
additional "flood control space" would effectively reduce the long-
term yield to the Upper Basin, and water users in both the Upper
and Lower Basin would be adversely affected. By reducing storage
capacity, equalization releases would be made sooner, there would
be fewer possibilities of surplus determinations, and additional
water would be bypassed to Mexico. Colorado stated in its comments
that "the onlv acceptable way to gain. additional flood control
storage in Lake Powell is by raising the height of the spillway
gates as recommended by the Bureau of Reclamation. . ." Colorado
supported Reclamation I s recommendation under the preferred
alternative. Finally, we are concerned that this reduction in
system yield would reduce. the flexibility of the Bureau to adjust
reservoir operations consistent with the Law of the River, to meet
fish, wildlife, endangered species and recreational needs in the
Upper Basin. The DEIS does in fact recognize the reduction in

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