For the first time in more than a decade, water from the Colorado River has reached the sea as scientist released an experimental flood that restored the historic waterway's delta.
After flowing from the Rocky Mountains to the Gulf of California for millions of years, the river has not regularly reached the sea for more than 50 years as its water was diverted and dammed for agriculture and to slake the thirst for drinking water in faraway cities.
The last time water naturally coursed through the river's vast delta region was 16 years ago.
In March of this year, however, 105,000 acre-feet of water was released from the Morelos Dam on the United States-Mexico border, with the river once again reaching the sea on May 15.
The experiment was the result of an agreement between the U.S. and Mexico governments and was intended to restore the desiccated region's native vegetation and attract wildlife.
Since the release, which lasted 8 weeks, researchers have been monitoring the river's lower reaches and delta region with sensors on the ground and orbiting in satellites.
The previous dry stretches of the river and its delta have seen greener vegetation, the germination of new vegetation along the river and a temporary rise in the water table, the monitoring has found.
"The pulse reversed a 13-year decline in vegetation," said Pamela Nagler of the U.S. Geological Survey's Southwest Biological Science Center in Tucson, Arizona.
Results of the experiment were reported this week in San Francisco at the annual meeting of the American Geophysical Union.
While just a small amount of water actually reached the Gulf of California -- most of it soaking into the ground within some 35 miles downstream of the dam -- water flowing into groundwater stores restored vegetation downstream even in areas not directly seeing water flow, the researchers said.
In addition to the vegetation, both resident and migratory birds likely benefited from the experimental flooding, says Karl Flessa, a geoscientist at the University of Arizona and co-chief scientist of the project team.
The Colorado River delta is situated on the Pacific Flyway, a significant migratory flight route in the western U.S., and "birds traveling north and south presumably will benefit from the increased quality of the habitat there," he says.
