Aug 162010

The Río Colorado formed a vast delta in the otherwise arid Sonoran desert in northern Mexico where it enters the Sea of Cortés (Gulf of California, see map.) The delta wetlands created ideal conditions for a rich variety of wildlife. The river enters Mexico at the Southerly International Boundary where a gauging station records the river’s discharge. This river is one of the most altered river systems in the world.

Map of the Colorado delta

Map of the River Colorado delta. All rights reserved.

The amount of water reaching Mexico has declined dramatically as a result of the Hoover and Glen Canyon dams and other diversions of Colorado River water in the USA. The few years of higher flows in the 1980s coincide with flood releases from US dams when they had been filled by heavy rains.

The river’s drastically reduced annual discharge violates a 1944 treaty under which the USA guaranteed that at least 1750 million cubic meters would enter Mexico each year via the Morelos diversionary dam in the Mexicali Valley. The Río Colorado wetlands have been reduced to about 5% of their original extent, and the potential water supply for the rapidly-growing urban centers of Mexicali, Tijuana, Tecate and Rosarito has been compromised.

The map and description above come from Geo-Mexico: the geography and dynamics of modern Mexico.

If you are interested in learning more about this river, a great place to start is the recently published book about the Colorado River called Running Dry: A Journey From Source to Sea Down the Colorado River (Jonathan Waterman; National Geographic Books, 2010). Waterman hiked and paddled the length of the river from the Rocky Mountain National Park to its delta in the state of Baja California, Mexico.

For excerpts from the book, see Running Dry on the Colorado and Mighty Colorado River dribbles through Mexico.

Peter McBride, a photographer, accompanied Waterman on his two year trek. His evocative photographs will appear in the book The Colorado River: Flowing Through Conflict (Westcliffe Publishers), due out in September. See Down the Colorado (slideshow) for some examples of his Colorado River photos.

Rivers, reservoirs and water-related issues are discussed in chapters 6 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico. Ask your library to buy a copy of this handy reference guide to all aspects of Mexico’s geography today! Better yet, order your own copy…

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