By Roberta Attanasio
For six million years, the Colorado River ran from the Rocky Mountains to the Gulf of California—through 1,450 miles of mountains, deserts, canyons, and the lush delta in Mexico. Now, it no longer reaches the sea. The once vast and fertile delta of the river is dry—a parched wasteland.
In 1931, the United States Bureau of Reclamation built the first of a series of large dams along the lower Colorado River, which now provides water to two states in Mexico and 30 million people in seven U.S. states. Until the 1950s, the delta was still a network of freshwater and marine wetlands with meandering river channels—an opulent habitat for a very diverse and thriving wildlife. Then, things changed fast—the water slowed to a trickle. Peter McBride, author of The Colorado River: Flowing Through Conflict, said in 2010 “I spent two weeks walking the most parched, barren earth you can imagine. It’s sad to see the mighty Colorado River come to a dribble and end some 50 miles north of the sea.”
There are good news, though—we may be getting back some of the lost opulence. Minute 319—an amendment to the 1944 Water Treaty between Mexico and the United States—calls for a pulse flow (a large one-time release of water) that will improve surface water and groundwater conditions as well as natural vegetation and wildlife.
On March 23, the pulse flow will be released from Lake Mead, the largest reservoir in the United States, and will continue for nearly 2 months, sending water down the lowermost Colorado River. Although the pulse represents just 0.7% of the 18.5 billion cubic meters that once reached the gulf each year, research teams from United States and Mexico universities, agencies and environmental groups expect a quick response, as the newly released water creates new habitats for seedlings, while flushing salts from the soil. After the pulse ends on May 18, researchers will measure seed germination and seedling survival at different time points. Later, they will rely on aerial photographs or satellite images to monitor tree growth.
However, Minute 319 is expected to accomplish much more, as “It establishes new rules in sharing Colorado River water while providing immediate plans to address current challenges along the river during the next five years. Equally important, the pact sets the stage for how the two nations might work in the future to establish a long-term management policy for the Colorado River.”
The amendment comes after years of negotiations and meetings. Now, the United States and Mexico, for the first time, have set criteria to share both water surpluses and water shortages. For example, Mexico has limited water storage capacity—thus, it will store some of its Colorado River water in Lake Mead. In exchange, the United States will send less water to Mexico when droughts occur in the states served by the river.