The Mexican Water Treaty
The possibility of a future Treaty with Mexico concerning
Colorado River waters was recognized in
Article III(c) of the Colorado River Compact of 1922. This
provided that any right to the use of such
waters accorded Mexico shall be supplied first from surplus
over and above the aggregate of the
quantities specified in paragraphs III(a) and (b), and if
insufficient, then the deficiency shall be borne
equally by the Upper and Lower Basins and whenever
necessary the States of the Upper Division
shall deliver at Lee Ferry water to supply one-half of the
deficiency so recognized in addition to that
provided in paragraph (d). It was assumed at that time that
a surplus of 2 maf annually would be
available. (The respective obligations of the Basins under
this provision is still subject to different
interpretations.)
The possibility of a Treaty was again mentioned in the
Boulder Canyon Project Act of 1928. Section
20 provided that nothing in the Act shall be construed as a
denial or recognition of any rights, if any,
in Mexico to the use of waters of the Colorado River
System. In 1922 Mexico used 500,000 acre-
feet of Colorado River waters annually. By 1935, when
Hoover Dam was finished, Mexico used
750,000 acre-feet annually. By 1944 that use had risen to
1.5 maf annually. Efforts to negotiate an
agreement with Mexico failed in 1930 when Mexico claimed
4.5 maf and the United States offered
750,000 acre-feet. However, negotiations initiated in 1941
did result in the 1944 Treaty. That Treaty
linked the waters of the Rio Grande River (much of whose
waters originate in Mexico but is used in
the United States) with the Colorado River waters (all of
which originates in the United States).
Impetus to a Treaty was provided by the scheduled
organizational meeting of the United Nations and
by the fact that Mexico was a wartime ally of the United
States.
The Committee of Fourteen (two representatives from each of
the seven Basin States) had proposed
deliveries to Mexico of 800,000 acre-feet each year when
releases from Lake Mead total 10 maf plus
a percentage change when Lake Mead releases were more or
less than 10 maf. Of the seven Basin
States California and Nevada opposed the 1.5 maf adopted by
the two countries. The other Basin
States supported it in order to limit Mexico before her
increasing uses invaded their share of
Compact water.
Article 10 of the Treaty guarantees to Mexico a minimum
quantity of 1.5 maf of Colorado River
water annually, to be delivered in accordance with
schedules furnished in advance by Mexico. The
need for the schedules was to require Mexico to take
minimum flows, which comprised leakage from
Imperial Dam and return flows below Imperial Dam that could
not be controlled in any event. If
there is a surplus, as determined by the United States, an
additional 200,000 acre-feet may be
provided, but Mexico acquires no rights to more than 1.5
maf.
In the event of an extraordinary drought, Mexican
deliveries will be reduced in the same proportion
as consumptive uses in the United States are reduced. Even
in the drought years of 1976-77 this
provision was not utilized nor is it settled whether water
in storage in United States reservoirs may
be protected or must be released to satisfy the Treaty
obligation.
The question of the quality of the water has been a source
of controversy. Article 10 refers to
"waters of the Colorado River, from any and all sources.
Article 11 states that the waters to be
delivered shall be made up of the waters of the river,
"whatever their origin..." The United States has
construed the Treaty to mean that Mexico can be given
waters of any quality; i.e., return flow or
seepage, whether usable or not. The Mexican view is that
the water has to be usable and of a quality
equal to that delivered to the United States users.
Mexico was required by Article 12 to construct a diversion
structure below the upper boundary line,
which it did by building Morelos Dam, and protective works
to prevent damage to United States
lands. The United States was to build a regulating dam
which it did by constructing Davis Dam.
Article 13 dealt with flood control plans. Article 15
contained schedules of deliveries.
Article 24(d) authorized the International Boundary and
Water Commission to settle all differences
that may rise in the "interpretation or application of this
Treaty, subject to the approval of the two
Governments." This provision was relied upon by Ambassador
Brownell after negotiating Minute
No. 242 to explain why Senate approval was not sought in
the final and permanent solution to the
salinity problem. The Ambassador stated that the approval
of the United States Government to the
required authorizing legislation and congressional
appropriation of funds would satisfy the provisions
of the Treaty. On April 18, 1945, the Senate ratified the
Treaty with reservations. On November
27, 1945, President Truman proclaimed the Treaty in force
as of November 8, 1945.
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