WSP08576

• File Number: 8210.140.20
• Description: Colorado River Basin Organizations and Entities - Colorado River Basin States Forum - California
• State: CA
• Basin: Western Slope
• Date: 7/13/1967
• Author: CO River Board of CA
• Title: Annual Report 1965-66
• Water Supply Pro - Doc Type: Annual Report

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Table 6

PROBABILITY OF MEAN ANNUAL VIRGIN flOWS
COlORADO RIVER AT LEE FERRY
BASED ON IB96-1965 PERIOD OF RECORD
(Millions of Acre-feet)

Onc-vear Auw________.
lO-year mean. _, _ ____
70-vear mcan__ _ ____

&(I-paanl
Charlet Inlnva!
12.0-17.8"
13,7-\6,2
H,J-l~.6

[)()-ptr(rllt
Chant''' /nlrTf.a!
7 8-22. It
11.8-18.0
13.4-164

p

N01'C: The a\"erJge Au,," or midpoint \~Iu" for ea.ch imcn'JI is 14 9 millIon
a.(",e-feel.
.. 25% chalice of flow leu tha.n 12.0 or more Ih..n 17.S million :lefe-fecl.
t 5% chance 01 flow 1e5; than 7.8 or more lhan 22 1 m,11ioo iere-fect.

Criteria for Long-range Operation
of Reservoirs

Section 601 of H.R. 4671, as approved b~' the
Subcommittee on Irrigation and Reclamation on
June 27, 1966, would direct the Secretary of
the Intcrior to establish equitable criteria for
the coordinated long-range operation of thc
reservoirs constructed under authotin' of the
Boulder Canyon Project Act, thc 'Colorado
River Storage Act, and H.R. 467]. These cri-
teria would be prepared and reviewed annually
in consultation with representatives of the seven
Colorado River Basin states and would be con-
sistent with the Law of the River.
The language was developed in a series of
exhaustive intcrbasin negotiations. Inclusion of
such language in the bill was deemed essential
by Upper Basin spokesmen who were concerned
that the operation of the reservoirs could be
detrimental to Upper Basin interests because of
(I) lack of specific operating proccdures in the
filling criteria for Lake Powell, promulgated b~'
the Secretary of the Interior on April 4, 1962.
and (2) lack of official interpretation of certain
provisions of the Colorado Rivcr Compact,
particularly article III, paragraphs (c), (d) and
(e). These provisions require: III (c) that obli-
gations to "lexico be met first out of surplus
and then by sharing of the burden of any de-
ficiencies equally between the Upper and Lower
Basin, III (d) that the states of the Upper Divi-
sion shallnClt cause the flow of the ri,'er at Lee
Ferry to be depleted below 75 million acre-feet
in any ten-year period, and III (c) that the
states of the Upper Division shall not withhold
water and the States of the Lower Division shall
not require the delivery of water which cannot
reasonably be applied to domestic and agricul-
tural uses.

The objective of Section 601 of H.R. 467] is
to avoid uncertainties caused by varying inter-
pretations of the Compact and to providc for a
sharing between basins of the benefits of wet
I'ears and the burden of drawdowns during
droughts.
Studies wcre made and analyzed bv the Board
staff and the Department of ", ater Resources to
appraise different suggcsrions as to operating
principles and criteria and to determine which
would most nearly optimize total production of
hydroelectric power and still be consistent with
water supply objecrives. The studies showed
that operation of Lake Powell under a rigid rule
curve as originally proposed b)' the Upper
Basin, based upon the Lee Ferry deliluy obli-
gation of Article III (d) and the advent at any
point in time of the most critical drought in
history would not only (I) require the main-
tenance of progressively larger quantities of
holdover storage in Lake Powell at the expense
of storage in Lake I\kad, as Upper Basin deple-
tions increase, but would also (2) limit the reg-
ulatory capability of Lake Powell and possibl~'
(3) result in excessive spills from Lake Powell
and thereby a loss of power production.
California representatives urged the use of a
probability approach as being more equitable for
deretInining the amount of storage to be re-
tained in the Upper Basin reservoirs at any time.
Plate IO illustrates this concept. It shows that on
the basis of the 1896-1965 average water suppl~-
there is better than a 25 percent chance that the
major reservoirs on the river will be full b,' the
end of 1975 and that on the basis of the 1922-
1965 average there is a ten percell[ chance that
the reservoirs will be full b,' rhat time. The "ear
] 97 5 is significant since it' is projected that the
Central Arizona Project will put a large new
demand on the river then.
As a result of thc studies and negotiations,
Section 601 of the bill approved by the House
commirree contained a list of priorities to gOl'-
em the storage of water in storage units of the
Colorado River Storage Project and releases of
water from Lake Powell. The priorities are (I)
releases in accordance with article III (c) of
the Compaet, (2) releases in accordance with
article III (d), and (3) accumulation of stor-
age in the upper basin and releases to meet uses
specified in artiele III (e). Compromise lan-
guage was agreed upon in Sec. 601 (b) (3)

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