WSP04330

• File Number: 8220.101.03
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 7/2/1990
• Title: CWCB Agenda Item #7, July 9-10-1990-Board Meeting - Legislation Concerning Glen Canyon Dam Operations
• Water Supply Pro - Doc Type: Board Memo

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POSITION PAPER ON H.R. 4498

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Colorado River Basin States' Governors' Representatives
for Colorado River Reservoir Operations
and the
Upper Colorado River Commission

June 4. 1990

Backqround on Glen Canyon Dam Operations

The operation of Glen Canyon Dam is essentially a twofold
procedure. First. the monthly and annual volumes of water to
be stored and released are determined annually based upon water
supply considerations. water delivery requirements. and the
avoidance of anticipated spills from Lake Powell. These
determinations. which are set forth in a projected plan of
operation each year (the annual operating plan or AOP). are
<1overned by. among other things. ,the Colorado River Compact.
the criteria set forth in section 602 of the Colorado River
Basin Project Act of 1968 (the 1968 Act). and the "Criteria for
Coordinated Long-Range Operation of Colorado River Reservoirs"
(the Coordinated. Long-Range Operating Criteria) promulgated
pursuant to section 602 by the Secretary of the Interior
(Secretary). in 1970. AOPs are developed by the Secretary in
consultation with the seven basin states as required by section
602(a)(3) of the 1968 Act,

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Second. given the'monthly volumes of water to be released.
within-the-month (i.e.. daily and weekly) fluctuations in
release patterns at Glen Canyon Dam are established in
accordance with power generation needs as determined by the
Western Area Power Administration. While the operational
parameters for fluctuating hydropower releases have been
expressly identified (i.e.. there currently are prescribed
minimum flows. maximum flows. and maximum rates at which
releases may be increased or decreased). formal power operating
criteria have not been promulgated.

Monthly and annual reservoir operations at Glen Canyon Dam
are of the most concern to the States' Representatives and the
Commission. Restrictions on within-the-month fluctuations for
power releases are of concern only if those restrictions
interfere with the volume of water to be released in any given
month.

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With respect to so-called "clear water flood releases" from
Glen Canyon Dam. adjustments were made in annual reservoir
operations starting in 1986-87 which reduced the probability
that sustained high flows in excess of powerplant capacity
would occur in the future. Formerly. such high. sustained
releases would have been expected to occur in one out of every
three to four years. That probability has now been reduced to

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