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<br />1.308
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<br />16. DISCUSSION OF UPPER BASIN SUMMARY .
<br />
<br />that they are, it may be necessary to evaluate the 'Waters of the Colorado
<br />. River System" as of their places of origin and utilization, which has not been
<br />attempted in the Report. It will be necessary to determi.ne or evaluate the
<br />natural losses which took place from river channels and from lands prior to
<br />their conversion to reservoir and irrigated areas. And in general to segregate
<br />the waters of the Colorado River System into categories of consumed and un-
<br />consumed quantities, with further segregations of the consumed quantities
<br />accordingly as the same may be beneficial consumptive use under the provisions
<br />of the Compact, or non-beneficial.
<br />
<br />Commenting that since the average annual flow at Lee Ferry in the 1931-
<br />1940 period, had no upstream diversion been made, would have been 12,234,000
<br />acre feet, the Report says: 'after deducting from this the 7,500,000 acre feet
<br />allocated to the Upper BaSin, only 4,734,000 acre feet would have remained for
<br />the Upper Basin," and hence full depletion of 6,908,000 acre feet could have
<br />been made therefor, only if, at the beginning of the decade, the Upper Basin
<br />had holdover storage sufficient to permit releases of 2,174,000 acre feet
<br />annually throughout the ten-year period. Previouely herein the suggestion has
<br />been made that, when Upper Basin depletions including reservoir losses attain
<br />a normal average of 7,643,000 acre fest annually, the drought cycle average
<br />may be substantiaDw less than 6,908,000 acre feet per year.
<br />
<br />In any event, using the Bureau figure of 6,908,000 acre feet, and
<br />recalling that 831,000 acre feet thereof is reservoir evaporation loss, it
<br />might be said that, when all the potential irrigation and exportation projects
<br />listed in the Report are constructed and in operation, to cause depletions of
<br />6,603,000 acre feet in a normal cycle, such depletions will decline to 6,077,000
<br />acre feet per year in a drought cycle, and will thereby deplete the flow at
<br />Lee Ferry to 6,157,000 acre feet per year during such a drought cycle, unless
<br />in the meantime sufficient storage capacity shall have been constructed up-
<br />stream from Lee Ferry, and filled during favorable years and cycles, to permit
<br />of net releases during the assumed drought decade averaging 1,343,000 acre
<br />feet each year, in addition to providing for evaporation losses from such
<br />reservoirs estimated at 831,000 acre feet per year.
<br />
<br />In the event further invsstigations should disclose that, with irrigation
<br />and exportation depletions averaging 6,603,000 acre feet under normal condi-
<br />tions, the depletions under drought conditions will be less than 6,077,000
<br />acre feet, then the necessary storage capacity to insure the delivery of
<br />75,000,000 acre feet each consecutive tan-year period would be reduced below
<br />the amount shown in the Report, with corresponding reductions in reservoir
<br />evaporation losses.
<br />
<br />Inasmuch as all the potential main river power projects listed in the
<br />Report will generate power in amounts greatly in excess of future (1980)
<br />market requirements of the Upper Basin, such projects should not be constructed
<br />until there is need for the replacement storage capacity of reservoirs involved
<br />in the main river power projects. Such a need will not arise until more than
<br />half of the irrigation and exportation program outlined in the Report for the
<br />Upper Basin has been completed.
<br />
<br />(24)
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