The flow was expected to intensify and reach a peak Thursday of an additional 4,200 cubic feet per second.
"You just see visually quite clearly a much larger volume of water in the river and there's quite a buzz about it," said Terry Fulp, regional director of the Lower Colorado Region for the U.S. Bureau of Reclamation.
Farms, businesses and homes in seven U.S. states — Arizona, California, Colorado, Nevada, New Mexico, Utah, Wyoming — rely on the Colorado River, as do the Mexican states of Baja California and Sonora.
In 2012, the two countries that share the river water agreed on ways to share the pain of droughts and bounty of wet years, a major amendment to a 1944 treaty. Part of that agreement called for restoration of the Colorado River delta.
"Today we are witnessing what appears to be a paradigm shift in the way we manage water," said Jennifer Pitt, director of the Colorado River Project, who helped negotiate the one-time flood. "Historically in the West, everyone has approached water with an 'us against them' mentality. Now we're talking about how we can share water, conserve water, and invest in new water projects and the health of the river itself. It's truly refreshing."
The release of water was aided through water conservation projects by the U.S. and Mexico, according to the International Boundary and Water Commission. Officials from those two countries were scheduled to be at the Morelos Dam on Thursday for an event to mark the restoration effort.
Experts will monitor the flood to determine its effects on the environment.