WSP08103

• File Number: 8278.400
• Description: Title I - Minute 242
• Basin: Colorado Mainstem
• Date: 1/1/2002
• Author: INBWC
• Title: Minute 242 2002 Annual Report
• Water Supply Pro - Doc Type: Annual Report

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levels in waters delivered at the land boundary. The IBWC 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 signiticant
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, Begilming in early 1995, the International Task Force exchanged information
regarding operations in the United States and Mexico. Salinity readings during 2002 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 Southerly
Land Boundary (SLB). Mexico uses this combination of waters to irrigate 93,860 acres (38,013
hectares) 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 SLB 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 four months of the year and examined scenarios of actions in each country that
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 shall
continue to meet its legal obligations as described in Minute No. 242 by continuing 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 of the Wellton-Mohawk drainage canal was damaged by floodwaters from the Gila River.
The damages were repaired.

During 2002, the YDP continued to be on standby status while the USBR reviewed alternatives for
complying with the salinity differential.

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