WSP09250

• File Number: 8278.400
• Description: Title I - Mexican Treaty and Minute 242
• Basin: Colorado Mainstem
• Date: 1/1/1970
• Author: IBWC
• Title: Minute 242 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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d) The average annual salinity of the total annual quantity af Colorado River
waters delivered to Mexico from above Imperial Dam reduced from 910 ppm
in 1965 to 852 ppm in 1970, a totol of 58 ppm. The salinity decreased
about 111 ppm from 1965 to 1967, and then increased an average of
about 18 ppm per year for the past three years.

The above -cited records support the view that progress has been made during the
5-year agreem~nt --Minute No. 218 -- towards a solution of the salinity problem.

8. Minute No. 218 Extended One Yeor

On November 15, 1970, the 5-year term of Minute No. 218 expired.

On November 16, 1970, the Governments of the United States and Mexico, through
the U. S. Ambassador to Mexico and the Mexican Secretary of Foreign Relations,
respectively, agreed by an exchange of notes to extend Minute No. 218 until
November 15, 1971, with the unde,rstanding that the extension may be superseded
by a new agreement reached prior to November 15, 1971. This extension was
agreed upon by the two Governments to allow the new administration in Mexico
which took office December 1, 1970, time to acquaint itself fully with the problem.

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9. Related Matters

0) New Wells in Yuma Area. The 12 new wells on the Yuma Mesa and the
conduit and outfall to discharge to the Colorado River at a point about
6 miles above Morelos Dam have been installed. The possible utilization
of these wells is pending a new agreement with Mexico for solution of
the salinity problem.

Early in the 5th year, use of the Yuma Mesa wells was anticipated during
the year in order to effect a reduction in salinity to Mexico. However, such
use was not found necessary.
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b) Yuma Ground Water Iv\odel Studies. The analog model studies and report
of the Yuma area ground water system, by the U. S. Geological Survey
laboratory in Phoenix, Arizona, were completed during the past year and
the results presented to the Mexican Engineers on February 4, 1970. The
model demonstrates that the source of such woters as flow underground to
Mexico is from United States irrigation of its lands and that the effects
of pumping of the 12 wells on the Yuma Mesa on such ground water flows
to Mexico would not be significant.

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c) Mexico's RehabiJ"itation Plans. The rehabilitation of the Mexicali Valley irri-
gation and drainage system, which was initiated in June, 1969 and includes
concrete lining of the canal system, continues to progress. It is reported that,
to date, about 27 miles of canals have been lined, and that the rehabilitation
is about 15 per cent complete.