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Friday, December 6, 2013

U.S.-Mexico Water Sharing: Background and Recent Developments - R43312


Nicole T. Carter
Specialist in Natural Resources Policy

Clare Ribando Seelke
Specialist in Latin American Affairs

Daniel T. Shedd
Legislative Attorney

The United States and Mexico share the Colorado River and Rio Grande pursuant to binational agreements. Compliance with these agreements becomes more complicated and controversial as water demands near or exceed available supplies and when drought and high heat further reduce availability and increase demand. 

Colorado River.
The Colorado River flows through seven U.S. states before reaching Mexico, and 97% of the basin is in the United States. A 1944 Water Treaty requires that the United States annually provide Mexico with 1.5 million acre-feet (AF) of Colorado River water, which represents about 10% of the river’s average flow. Binational disputes have arisen over water quantity, quality, and conservation. Under the Treaty, disputes can be resolved through amendments, called “minutes.” Minute 242 from 1973 requires that the salinity of Colorado River water deliveries not exceed a specified limit. Minute 319, agreed to in 2012, provides for a bilateral basin water management, storage, and environmental enhancement effort. 

Rio Grande.
The Rio Grande is governed by two separate agreements. Deliveries to Mexico in the northwestern portion of the basin (near El Paso/Ciudad Ju├írez) occur under a 1906 Convention, while deliveries for the southeastern portion (which is below Fort Quitman, Texas) are laid out in the 1944 Water Treaty. The 1906 Convention requires an annual delivery to Mexico of 60,000 AF, which can be proportionally reduced based on drought conditions. The United States is not required to make up for reduced deliveries. From 1939 to 2013, deliveries to Mexico were reduced in 31% of the years, including in 2012 and 2013.

Under the 1944 Water Treaty, Mexico has rights to two-thirds of the flows of six Mexican Rio Grande tributaries. The one-third delivered to the United States must average at least 350,000 AF per year, measured in five-year cycles. The United States is entitled to all flows from U.S. tributaries. If Mexico fails to meet its five-year delivery obligations because of “extraordinary drought,” which the Treaty does not define, deficiencies are to be made up during the next fiveyear cycle. Mexico met its delivery obligations until the region’s 1994-2003 drought.

As of October 2013, which marked the end of the third year of the October 2010 to October 2015 cycle, Mexico’s delivery of Rio Grande water to the United States exceeded the 350,000 AF annual target and reduced its debt for the cycle to roughly 288,000 AF (27%) based on a target Rio Grande delivery schedule. The 2011-2013 drought conditions in the basin raised tensions as water constraints intensified. Mexico’s deliveries in the second year of the cycle, covering most of 2012, were less than 30% of the target. Since late 2012, the Mexican and U.S. sections of the entity charged with providing binational solutions to issues that arise during application of the treaties have been regularly meeting to discuss Mexico’s water debt. Summer precipitation in 2013 provided some relief; this precipitation along with changes in reservoir management resulted in a significant decline in Mexico’s water debt by October 2013. 

Legislative Responses
. Some Members of Congress have expressed concerns about the adequacy of Mexico’s 1944 Water Treaty compliance, U.S. efforts to hold Mexico to its treaty obligations, and the resulting economic impacts. Various bills (e.g., H.R. 1863, H.R. 2307, S. 1125), as well as H.R. 2642 (2013 farm bill, as passed by the House), include provisions to require additional reporting on Mexico’s efforts to meet its Rio Grande water deliveries and on implementation of Minute 319 related to the Colorado River.

Date of Report: November 19, 2013
Number of Pages: 20
Order Number: R43312
Price: $29.95


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