How California's Atmospheric Rivers Will Change the Colorado River

An atmospheric river has caused an onslaught of rain in California, drenching the south of the state and causing severe flooding.

The historic storm ripped across the state at the weekend and through Monday, killing at least three people. It is being classed as a "1,000-year flood," which means that they are on a scale that has a 1 in 1,000 chance of occurring in any given year.

According to the National Weather Service, the heaviest rainfall in the region was in Bel Air, located in Los Angeles County with a total of 11.81 inches in the last few days. To put it into perspective, the average yearly rainfall for Los Angeles is 18.67 inches.

The rain and subsequent flooding could mean good things for the water crisis gripping the southwestern U.S., though—especially the Colorado River and its basin if the precipitation reaches the upper basin.

The Upper Colorado River basin covers Colorado, New Mexico, Utah, and Wyoming, while the lower basin covers Arizona, California, and Nevada.

If the moisture unleashed from the atmospheric river reaches the Upper Colorado River Basin, it could improve its flows which have been incredibly low in recent years.

"Precipitation, especially in the form of snowfall, over the Rocky Mountains is going to be helpful," Becky Bolinger, an assistant state climatologist at Colorado Climate Center at Colorado State University, told Newsweek. "Water supply forecasts have been a bit lower this winter so far, as snowpack started late and has lagged behind a bit. But storms like this will boost the supply forecast—maybe not to 100 percent of average, but better at least."

A map of from the USDA on the snowpack for the San Juan mountains in southwest Colorado, which feeds into tributaries of the Colorado River, shows just how much has accumulated so far this year. So far, the levels are lower than normal.

"The black line shows the accumulation of snowpack this winter so far, compared to normal, which is the green line. The San Juan mountains have been struggling to get up to average," Bolinger said.

"We've had one bump from the last round of storms. I would expect after the next round of storms this week, the black line will be in-line with the average line. But as you can see, we'll still have a couple more months to go, and more accumulations are needed to hit the normal peak snowpack in early April before it starts melting."

Experts keep a close eye on the snowpack levels and the health of the Colorado River because the southwest has been on the brink of a water crisis in recent years due to severe drought in the area.

It is one of the most important rivers across the southwestern United States and northern Mexico, providing water for around 40 million people.

Although snowpack levels have been decent over the last year due to an unusual amount of precipitation in the state, that does not mean the river is completely out of the woods. It remains to be seen what 2024 has in store for the Colorado River and its reservoirs.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about the Colorado River? Let us know via science@newsweek.com.