WSP06606

• File Number: 8278.400
• Description: Title I - Mexican Treaty and Minute 242
• Basin: Colorado Mainstem
• Date: 1/1/1996
• Author: IBWC
• Title: Minute 242 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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levels in waters delivered at the land boundary. The International Boundary and Water Commission,
United States and Mexico, is addressing these matters through an International Task Force
arrangement involving the federal water agencies of each country. The effort is for adjustments in
operational practices at those periods where high salinity is a significant problem for Mexico.

Mexico utilizes the treaty waters diverted at Morelos Dam for irngation and domestic uses in the
Mexicali Valley and conveys some of these waters via aqueduct to Tecate and Tijuana. Mexico's
concern with an occasional salinity peak comes at those times when Mexico's water delivery
demands are low. Beginning in early 1995, the International Task Force exchanged information
regarding operations in the United States and Mexico. Salinity readings during 1996 indicate
insignificant peaks at this delivery point.

Mexico utilizes some of the NIB delivered waters along with water from wells near San Luis, Sonora
for mixing the drainage waters that the United States continues to deliver at the SIB. Mexico uses
this combination of waters to irngate 93,860 acres in the area of the Mexicali Valley in Sonora
known as the Left Bank unit. Mexico is concerned over reduced crop yields and deteriorating soil
quality and increased ground water salinity. In this case also, the International Task Force met
several times to exchange information on United States operations and Mexico's management of the
-,delivered waters. Mexico, in this respect, requested that all its treaty deliveries be made at the NIB.
This proposal was not practical to the United States in that the United States is not able to prevent
all these drainage waters from discharge to Mexico at the sm and continues to have the right to
make these deliveries as part of the treaty volume. Further, this would require release of stored
water in the United States that is fully appropriated. Finally, there is the need to better understand
the problem in the Mexican irrigation system and all the factors that influence increasing soil and
groundwater salinity and lower crop yields.

As a matter of cooperation in the near te~ the International Task Force has narrowed the perceived
effects to a period of four months of the year and examined scenarios of actions in each country that
may be carned out to ameliorate salinity peaks during those periods. The two sides are soon
. _ _ _ _ _ ~~p~~ted t09,g~ple!e_in!~rn~ -,~~~s_ultati~I!~~I! fe~sibl~ ~lt~~atiy~~:_ ~~_l!nited_States holds to the
obligations and rights assumed in Minute 242 to continue to make the land boundary deliveries witli - --
the salinity in the waters customarily delivered at that point.

The Yuma Desalting Plant (YDP) has been off-line since the first part of 1993, when the concrete
lining of the Wellton-Mohawk drainage canal was damaged by flood waters from the Gila River.
The damages were repaired.

During 1996, the YDP continued to be on standby status while the U.S. Bureau of Reclamation
reviewed alternatives for complying with the salinity differential.

Groundwater

Point 5 of Minute No. 242 provides that:

''Pending the conclusion by the Governments of the United States and
Mexico of a comprehensive agreement on groundwater in the border
areas, each country shall limit pumping of groundwaters in its

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