BOARD01635

• Board Meeting Date: 3/26/1945
• Description: Table of Contents and Minutes
• Board Meetings - Doc Type: Minutes

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extent. ,Colorado says that data for drouth conditions, and suo';normal cy-
cles such as 19~1-194o, are important. out says that such data should ap-
pear separately from virgin flow estimations. Due to the uncertainties as
to when another such cycle of years may be encountered. and as to what then
may be the status of development, Color~o says th.t so-called virgin flows
for such an assumed dromh cyCle will 'be Jilisleading;'imd-Will not indicate
the streamflows available for irrigation. pcwer. and other purposes. unless
accompanied by reservoir operation studies to show, the effect~ of stream-
flow' regulation and the additional supplies of ""ter thereby made available
during euoh a period of years. Colorado suggests the inclusion in the Re-
port of such reservoir operation studie.. on virgin flow conditions to show
the regulating effect at Lee Ferry and the International Boundary, of mass
operations of reservoirs above those pointa.

20. Virgin flow' quantities shown in the Report are the sum of: (a)
the average annual streamflows recorded at (or scheduled for) the desig-
nated gaging station; plua (b) the allowances for upstream "depletions"
in the average year of the swne period. - said "depletions" being the quan-
tities of water estimated to have been withheld from the stream by the di-
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version. use and storage of ""ter from and in the natural drainage basin
upstream from the designated station. Neither the recorded streamflows nor
the "depletion" allowances. of the historio period. are shmm in the Report.
Colorado suggests that, for two key stations, the Report. should contain
detailed information concerning both items; and that the key stations should
be, Colorado Ri Vel" at Lee Ferry and, Internati onal Boundary.

21. Colorado points out that since "depletions" are a part of the es-
tinated "virgin flows," an understanding of what is meant by "virgin flows"
depends in part on the meaning of "depletions. III which are defined in
general as the differences between diversions and returns; and that evapo-
ration loeses from existing and potential main-stem reservoirs are entered
as depletions. but are not measurable by the difference between diversione
and returns. A proper definition of "depletions" would include both the
manner of calculation, or the factora employed' in the estimations, and the
place of evaluation, whether at the places where such "depletions" occur.
- or in terms of their resulting effects at points downstream. The data
presented are inconsistent in this respect. and therefore are not direct-
lY,cornparable. Upper Basin depletione appear to have been evaluated as of
the places where they occur. whereae in the Boulder and Gila divisions of
thl! Lower Basin. the upstream "depletions" appear to have. been credited
with the estimated salvage of water or reductions in natural conveyance
losses attributable to the diminished volumes and regulated character of
the flows resulting from upstream development. Colorado urges that both
basins be treated alike.

22. The recorded streamfloWll at designated gaging stations are the
unconsumed outflows from the upstream drainage basin. that were not with-
held from the stream either by man-made "depletions" or by natural losses
of water. In oaloulating the "virgin flows" of the Report. the man-made
"depletions" were added to the recorded outflows. and the natural losses
were ignored. Thus "virgin flows" may be said to indicate the streamflows
that might have been recorded during the average year of a similar olimatic