WSP07975

• File Number: 8278.100
• Description: Title I - Yuma Desalting Plant
• Basin: Colorado Mainstem
• Date: 10/1/1987
• Author: USDOI/BOR
• Title: Yuma Desalting Plant Operations Study - Draft Special Report
• Water Supply Pro - Doc Type: Publication

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The computer model YDPSHORT.FOR was used to simulate hydrologic
conditions that would exist with the va~ious plans. Where
proposed modifications to the YDP or changes in operating
procedures would reduce effective YDP capacity, the capacity
(production) was fixed in the model and the model was allowed to
determine the amount of water that would need to be wasted
(bypassed) to meet the salinity differential requirements of the
Minute. In those cases where a plan would provide substitute
water, the amount of irrigation return flow requiring treatment
was reduced to compensate for the amount of the substitute water
as follows: if the salinity of the substitute water available to
the YDP differed from the salinity of the river at Imperial Dam,
the substitute water was added to the assumed unmeasured inflows
between Imperial Dam and NIB, otherwise releases from Imperial
Dam were increased by the amount of the substitute water
available, and the model was allowed to determine the plant
capacity required to meet the Minute and the amount of water that
could be bypassed.

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In order to determine the amount of substitute water needed to
completely eliminate production from the YDP, the model was run
to simulate an unlimited water supply at Imperial Dam and no
desalting plant. The model was further allowed to bypass any
amount of drainage water necessary to satisfy the salinity
differential of the Minute. The computer model YDPSHORT.FOR
indicated that about 116,000 acre-feet of substitute water would
be necessary to eliminate production from the YDP when the
salinity at Imperial Dam is 879 mg/L. To satisfy this
requirement, 6,000 acre-feet of pumped drainage from the South
Gila Drainage Pump Outlet Channels (between Imperial Dam and NIB)
was assumed to be bypassed along with the 110,000 acre-feet of
return flow. Thus, any plan yielding over 116,000 acre-feet per
year was considered to completely eliminate the need for YDP
production. This would require pumping the 6,000 acre-feet of
additional drainage water into the By-pass Drain.

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The impacts that individual plans have on YDP production are
noted in the detailed description of each plan.

DETERMINATION OF ANNUAL COSTS

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A detailed description of the annual costs is in Appendix C
attached to this report. The cost estimates for all of the
alternative plans are based on the following assumptions and
procedures:

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1. The capacity of the YDP (used for comparison purposes)
was based on the analysis by YDPSKORT.FOR using the yields
determined by personnel in the Lower Colorado Region.

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