BOARD01635

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

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(1) The word "depleted" here refers to natural losses, sinoe by
definition there were no man-made "depletions" under virgin oonditione,
and might better read "reduoed" or "diminished."

(2) A "growing stre8.lll'" down to the Blaok Canyon seotion does
not mean that natural losses are absent above that point. or Dlay be ignor-
edas in the Report. On the contrary it means only that inflows to the
main river. or contributions from tributary streams and areas. are great-
er in 'amount than the quantities of water lost in oonveyanoe. Similarly.
a losing river in the desert region does not mean that there were no
tributary oontributions under virgin oondi tions. or that they may be dis-
regraded. Instead, it means that natural 'losses frOll\ the main-river'
ohannels _re greater in amount than the tributary inflows (exoept at
times of flood).

(3) With "virgin 1'10"8" of 2,282,000 aore-feet at Phoenix and
1,271,000 acre feet at Dane, the conveyance loss would be 1,011.000 aore
feet plu& all the virgin-tributary inflow, to the river section.

(4) The indioated net gain from Lee Ferry to le.guna Dam, ao-
cording to the above table, is leO.OOO acre feet, Since the contribu-
tions reported fram Little Colorado and Virgin Rivers together emount to
648,000 acre feet, the table implies that natural losses under virgin
oonditions Vlere 468,000 acre feet. Colorado questions; the accuraoy of
the estimates for the two reported tributaries. and says that misoellane-
ous tributary drainage areas were ignored. Under so-called virgin oondi-
tions the tributary o ontributions, between Lee Ferry and Laguna DIllll (as
estimated by ColoradO engineers) averaged 495.000 aore feet from the Little
Colorado River, 392,000 aore feet fram the Virgin River, 413.000 acre feet
from miscellaneous drainages between Lee Ferry and Boulder Dam, and 200,000
acre feet from miscellaneous streams (including'~t!~s River) and areas
between Boulder Dam and Laguna Dam. Assuming that -total figure of 1.500.000
acre feet, of the net gain between Lee Ferry and Laguna Dam'is 180.000 aore
feet. as shoVltl in the above table. the natural conveyanoe lose would aver-
_.~age 1,320,000 acre feet annually along that river section under virgin
- conditions.

(5) Fran the instances above mentioned it is apparent that
natural conveyance losses in the Colorado River Basin involve substantial
quantities of water, and it seeme self-evident that such losses under so-
ee.lled "virgin conditions," when stre8lllflcms were maximum arid ...holly un-
regulated, woul~ have been greater than thoee observed and calculated
from reoords during the historic period. Colorado suggests that estimates
'of natural losses should be made by the Bureau of Reolam6tion, and sh ould
appear in the Report. oovering so-called virgin conditions. cr the oondi-
tions of the period of record, or both. As estimated by Colorado engi-
neers during the period 1908-1942 (...hen man-made depletions averaged
1,952,000 acre feet per year above Lee Ferry. and 2,911,000 acre feet be-
low Lee Ferry. and when the recorded fllm at the Internatioli Boundary
averaged 12.683,000 acre feet annually), the natural oonveyance loeses
averaged 870.000 acre feet above Lee Ferry, and 2,~.000 acre feet below
Lee Ferry. or totalled 3,;10,000 acre feet annually in the Colorado