WSP10281

• File Number: 8278.300
• Description: Title I - Mexican Treaty
• Basin: Colorado Mainstem
• Date: 9/1/1991
• Author: Anne DeMarsay CRBSCF
• Title: The Brownell Task Force and the Mexican Salinity Problem - A Narrative Chronology of Events
• Water Supply Pro - Doc Type: Publication

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10 reaching an agreement,' but in early ]972 the Mexican government rejected U.S. proposals.
In June ]972 President Echeverria arrived in Washington with a stronger demand: parity.
Mexicali Valley farmers should receive water of the same quality as American water users
served by Imperial Dam, then about 870 ppm.

President Nixon responded in a joint communique issued June] 7, in which he promised to: ])
take action immediately 10 improve the quality of water going to Mexico; 2) appoint a special
representative to find a "permanent, definitive and just" solution to the salinity problem and
report to him by the end of the year; and 3) submit a U.S.-approved proposal to President
Echeverria for consideration and approval. The mwc was directed to draw up and sign a
Minute containing this program!

In preparation for the Mexican President's visit, the Office of Management and Budget (OMB)
and the Departments of State and the Interior, briefed President Nixon on possible diplomatic
courses of action and short- and long-term measures to reduce salinity levels of water delivered
to Mexico. In the short run, bypassing some portion of return flows and replacing it with better
quality water from another source seemed the only practical means. Long-term solutions fell
into four categories: ]) continuing to bypass Welllon-Mohawk return flows and substituting less
saline water from other sources (including "new water" from weather modification and other
augmentation technologies then under study); 2) eliminating salt loading by totally or partially
shutting down the project; 3) desalting all or part of the return flows; and 4) regulating salinity
according to state-by-state water quality standards, restricting irrigation or requiring more
efficient on-farm water management practices where necessary.

Before the Echeverria visit, the simplest and least expensive course of action appeared to be to
continue to bypass-and substitute better quality water for-some portion of the return flows,
while the issue of an acceptable salinity level was resolved diplomatically. After the
Wellton-Mohawk project reached salt balance, the U.S could undertake more costly or
controversial measures to permanently maintain the negotiated salinity level. This approach had
several advantages: it would have given Mexico an immediate reduction in salinity, preserved
the legal positions of both parties during negotiations over ultimate salinity levels, and deferred
capital expenditures or politically unpopular decisions. The Colorado Basin states had been
willing to support the equivalent salt balance concept; presumably they would have agreed to the
use of substitution water from a source within the Basin for a limited period.'O

Minute No. 24], the interim Minute required by the joint communique, was signed on July 14.
It reflected the approach described above: the U.S agreed to bypass 118,000 acre-feet of
Well ton-Mohawk drainage per year, replacing it with additional water released from Imperial
Dam. This action would have reduced the salinity level at Morelos Dam from 1,240 ppm (under
Minute No. 218, the interim 1965 agreement) to 1,140 ppm-the salt balance level, though the
term was not mentioned. Mexico, however, asked the U.S. to bypass the remaining 100,000
acre-feet of drainage without substitution, which resulted in a salinity level of about 950 to 1000
ppm.

Here the diplomatic situation became murky. Why did Mexico agree to let the U.S. limit its
efforts, even in the interim, to guaranteeing a level of salinity corresponding 10 that resulting