The Colorado River once flowed all the way to Mexico, spreading out in a massive delta ending in the Gulf of California.
This created vital wetlands that sustained both marine and terrestrial life.
However, over the last 60 years, dams on the Colorado River and rerouting of water into farmland and orchards stopped this historic flow.
The Colorado River delta, once lush with marshlands, is completely dry. The river's water is only allocated for human uses, and only flows to the sea only during years with exceptional spring floods. (Photo by Osvel Hinojosa-Huerta/Pronatura)
This week that all changed.
Over the last few years, a team of scientists in Mexico and the U.S. worked together to get approval to open the water flow into the delta once again.
University of Arizona scientists Karl Flessa and Ed Glenn are part of that team, which created an 'engineered spring flood' that started on Sunday March 23.
Other than a few wet years, according to U of A, the Colorado River has not flowed to the Gulf since 1960.
The Colorado River channel in Mexico is now filled with shrubs rather than water. The pools of water in the channel come from groundwater and from water seeping into the riverbed from nearby agricultural fields. The river no longer reaches the sea. (Photo by Karl Flessa/University of Arizona)
The manmade flood is still a far cry from the water amounts that used to flow into the delta.
According to U of A, the flood waters will be less than one percent of the river's annual flow.
"We're trying to simulate a spring flood, even though the amount of water is small compared to the natural spring floods of the era before the dams, when the river regularly flowed over its banks and formed extensive wetlands and forests of cottonwoods," Flessa said.
The flood is a result of an agreement between Mexico and the United States called Minute 319, a 2012 addition to the 1944 U.S.-Mexico Water Treaty.
The water in the Colorado River flow is divided up between Mexico, Arizona, California, Nevada, New Mexico, Utah, Colorado, and Wyoming.
The new agreement "identifies criteria for sharing of future water shortages and surpluses between the two countries, allows storage of Mexican water in Lake Mead and funds improvements to Mexican irrigation infrastructure" says the University of Arizona.
This is not the only manmade flood for the river delta. More water will be released during the five-year program that will monitor how the natural vegetation of the delta responds to the availability of more water.
Healthier vegetation creates habitats for marine, bird, and other wildlife native to the area.