WSP05341

• File Number: 8278.100
• Description: Title I - Yuma Desalting Plant
• Basin: Colorado Mainstem
• Date: 12/23/1992
• Author: USDOI/BOR
• Title: Yuma Desalting Plant - Alternatives for the Interim Period
• Water Supply Pro - Doc Type: Publication

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220,000 af per year to a low of 118,500 af per year. While the program
demonstrated an overall positive effect, a cause-and-effect relationship
for individual measures has never been established. All permanent
measures implemented by the WMIDD are still in use, although no active
Federal program is currently in operation.

Factors Affecting Increased Pumping

Ground-water drainage pumping has increased to about 145,000 af
annually. This increased drainage pumping is related to several
factors.

- More acreage is double-cropped than when the program was
initiated.

- In recent years, irrigation efficiency has declined to
. 58 percent.

- To stay within its annual consumptive use right, WMIDD may
be mining ground water to increase its return flow. As
consumptive use is defined as diversions minus return flow,
should WMIDD increase its return flow by pumping more ground
water into the drain, it would reduce the consumptive use
charged against its entitlement.

- If the District fails to continuously monitor ground-water
levels during the year, it may inadvertently pump more than
the minimum needed. In addition, WMIDD projects how much
water it will divert by the end of the year. If weather
conditions change during the later part of the year, or if
farmers change their historic irrigation trends, the
diversions required at the end of the year may be greater
than was projected, and ground-water pumping could be
increased to stay within their consumptive use requirement.

- Pumping may be increased to lower high ground-water areas
resulting from insufficient drainage pumping the previous
year.

- As irrigation efficiency levels decline, greater pumping
is required to maintain satisfactory ground-water levels
compatible with farming.

- High ground-water levels resulting from Gila River inflows
can require the District to pump excess ground water for
several years to lower ground-water levels to the levels
that existed prior to the Gila River flows.

Reclamation is concerned about the recent increases in ground-water
pumping and intends to take measures to ensure that drainage pumping not
exceed that deemed essential to prevent crop damage. Section 101(f)(I)
of Public Law 93-320 authorized the Secretary to accelerate the
cooperative program with WMIDD to improve irrigation efficiency.

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