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

and even if it were, the mean annual salt pickup would still lie within the

confidence limits (which will be discussed later).

Clearly, the unaccounted flow is due to all of the budget components in

varying amounts, but mainly the streamflow measurements, which represent over

95% of the total inflows and outflows in the budget. Therefore, adjusting

the streamf10ws to eliminate the unaccounted flow is a legitimate procedure

for reducing the error associated with unaccounted flow. Because the exact

contribution to the unaccounted flow of each of the stations is unknown, half

of the unaccounted flow is arbitrarily allocated to the incoming streamflows

and half to the river outflows, which results in a flow weighted average

quality being assigned to the ficticious outflow.

Recommended Budget

The most accurate estimate of salt pickup in Grand Valley is thought to be

provided by adjusting the flow as discussed above, and using the State Line

gage as the outflow station (see Tables 10 and 11, and Figure, 5). Adjusting

the flow is reco1lUDended because it is be lieved that the maj ori ty of the

unaccounted flow is due to sources other than estimation errors in

precipitation and consumptive use. That is, it is thought that most of the

unaccounted water has salt associated with it, and hence, adjusting the flows

such that the unaccounted flow is zero will yield the most ac:curate salt

pickup estimate.

The State Line gage is recommended as the outflow station for a number

of reasons. First of all, the State Line gage is much nearer to the area of

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