WSP01381

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 2/2/1989
• Title: Hydrologic Determination 1988 - Water Availability from Navajo Reservoir and the Upper Colorado River Basin for Use in NM
• Water Supply Pro - Doc Type: Report/Study

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reach maximum. The CRSS model does not model the cal1 situation but rath
it indicates the quantity of the call by the amount it shorts the Lower
Basin delivery. Appendix III shows the results of the analysis. Using
these data, a frequency analysis was made which demonstrates both severit:
and frequency of a calI on the river at a demand level of 6.1MAF.

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The results indicate that the frequency of a cal1 of 100,O~0 acre feet or.
less is about 0.75 percent while that of a calI over 2 MAF is less than 0
percent.. This is shown on an incremental basis in Figure 2 and on a
cumulative basis in Figure 3. A general conclusion of this analysis is
that cal1s on the river are likely to occur only very rarely even at a 6.:
MAF demand level, but their effects could have significant impact to the
Upper Basin and their magnitude could range to over 100 percent of Upper
Basin depletion. Cursory examination of demands less than 6.1 MAF
indicates that both frequency and magnitude of calls on the river diminisl
rapidly below this demand level.

6. Other Considerations - Changes in Assumptions

To obtain a wider range of yield analysis results, various changes in bas:
a~sumptionswere made and the corresponding results arrayed with previous
work. In particular, the use of inactive storage pools and a change in
minimum delivery to the Lower Basin were examined in regards to the effec
on Upper Basin yield. In the mass balance analysis discussed above, the
total amount of system storage used during the drawdown period as
determined from the use of CRSS was 24.762 MAF. There remained in inacti
storage and minimum power pools another 3.012 MAF. If it is assumed that
this entire amount is available for use and that the length of the drawdo
period would be the same as previously determined, the amount of storage
adjusted for use in a mass balance analysis using annual data would be:

[(24.762 + 3.012)x25/25.5833) - 4.00 - 23.141 MAF.

Utilizing this value in the mass balance procedure along with a minimum
reI ease of 8.23 MAF at Glen canyon produces a firm yield (no shortages) 0
5.67 MAF for the Upper Basin. The results of add itiona 1 analysis which
relate yield to basin wide shortages and the probability of meeting a yie
given a particular shortage are shown in Figure 4. Because the data are
somewhat limited, it should be understood that these curves are only
approximate and only give an indication as to the probabilities involved.

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