WSP00007

• File Number: 8281.400
• Description: Colorado River Studies and Investigations -- Colorado River Depletion Projections
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 3/1/1969
• Title: Past Depletions
• Water Supply Pro - Doc Type: Report/Study

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years of low runoff the limited supply available for storage, diversion,

and use reflects a below normal depletion to the streamflow at Lee Ferry..

Conversely in years of high runoff the availability of water in greater

quantities at sites of uses and the extension of the supply throughout

the irrigation season reflects an above normal depletion at Lee Ferry.

.Due to the lack of detailed data, the depletion in each year was assumed

to vary from the average annual depletion in proportion to one-half the

variation of the virgin runoff at Lee Ferry in the same year. from the

1914-1945 mean annual virgin runoff of the Colorado River at Lee Ferry.

Column 4 presents the adjusted unit rates of depletion for each year.

These rates were determined by multiplying the 1914-1945 mean annual

irrigation depletion rate by the adjustment factor given in Column 3.

The 1914-1945 mean annual irrigation depletion rate above Lee Ferry was

assumed as the 1914-1945 mean annual upper basin depletion at Lee Ferry

(less the net trans-basin export depletion as measured at Lee Ferry)

divided by the 1914-19'15 mean acreage irrigated in the upper basin.

This rate includes the minor depletions resulting from domestic use and

past reservoir evaporation losses.

Column 5 is the product of the estimated irrigated acreage (Column

2) times the adjusted unit rate of depletion (Column 4) for each year and

represents aggregate in basin depletion each year.

Column 6 gives by years the depletion to the flow at Lee Ferry

l'esulting from upstream trans-basin exports. Trans-basin depletions at

sites~of-use were adjusted slightly to account for proportionate channel

~alvage above Lee Ferry. This was assumed proportional to the total