WSP00824

• File Number: 8278.400
• Description: Title I - Mexican Treaty and Minute 242
• Basin: Colorado Mainstem
• Date: 1/1/1997
• Author: IBWC
• Title: Minute 242 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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Progress on U.S. Measures Provided for in Public Law 93-320

Beginning in late 1995, Mexico raised objections to peaks in salinity at the NIB and to the salinity
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 irrigation 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 1997 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 irrigate 93,860 acres in the area of the Mexicali Valley
. . u .. . in' Sonora known .as .theLeftBankunit; . Mexico is concerned-over reduced .cropyields 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 SIB 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 term, the International Task Force has narrowed the perceived
effects to a period of folii fuofilns bfthe year-and examiiiecl" scemmos o"factions. irideacn country tliaC
may be carried out to ameliorate salinity peaks during those periods. The two sides are soon
expected to complete internal consultations on feasible alternatives. The United States holds to the
obligations and rights assumed in Minute 242 to continue to make the land boundary deliveries with
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 ofthe Wellton-Mohawk drainage canal was damaged by flood waters from the Gila River.
The damages were repaired.

During 1997, 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

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