"The pact represents a major departure from years of hard feelings in Mexico about how the U.S. manages the 1,450-mile river, which runs from the Rocky Mountains to Mexico. In 2001, U.S. states established rules on how to divide surpluses but set aside nothing for Mexico. Several years later, the U.S. government lined a border canal in California with concrete to prevent water from seeping through the dirt into Mexican farms."
A recent Washington Post article discusses the longstanding conflict between Mexico and the US over the shared Colorado River, and the recent effort from both countries to address the challenge cooperatively.
http://www.washingtonpost.com/business/us-mexico-sign-pact-on-new-rules-for-sharing-colorado-river-water-in-fight-against-drought/2012/11/20/4c4bc72c-3376-11e2-92f0-496af208bf23_story.html
http://www.washingtonpost.com/business/us-mexico-sign-pact-on-new-rules-for-sharing-colorado-river-water-in-fight-against-drought/2012/11/20/4c4bc72c-3376-11e2-92f0-496af208bf23_story.html