WSP07957

• File Number: 8276.100
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/21/1983
• Title: Grand Valley Salt Pickup Calculations - Draft Report
• Water Supply Pro - Doc Type: Report/Study

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CHAPTER II

GRAND VALLEY RIVER BUDGET

percent to State Line is less than four percent. On the othE!r hand, the best

quality components are precipitation and consumptive use. Precipitation,

however cannot be responsible because it is measured and small, and cannot

reasonably be off by 60%. Nor can the consumptive use be soley responsible

because some years have an unaccounted flow nearly as largess the

consumptive use, and a near zero value of annual consumptive use is

unreasonable.

Nevertheless, it is informative to allocate all of the unaccounted flow

to consumptive use to establish a maximum possible downward effect of the

flow adjustment on salt pickup.

The result of allocating all unaccounted flow to consun~tive use is the

same as not adjusting the flow at all (see Tables 4 and 5, and Figure 4). A

better method of investigating the effect of the consumptive use estimates is

to scale up the consumptive use such that the resulting average unaccounted

flow is zero (see Tables 6-9). Hence, some years will have positive

unaccounted flow and some negative, but the average will be zero. To this

end, all monthly consumptive use values were scaled up by 20.93%, and then

for the sake of analysis, scaled down by the same percentage. The resulting

consumptive use estimates are thought to be conservative upper and lower

bounds of the actual value. The mean annual salt pickup values using these

bounds on consumptive use are represented by the innermost pair of lines

straddling the best estimate mean in Figure 5. For all this, there is no

reason to believe that the original estimate of consumptive, use is incorrect,

II-13