(CNN) A group of California water agencies that together consume the largest proportion of lower Colorado River water each year are offering to voluntarily cut their usage in an effort to save the river basin and stave off a larger crisis.
But one expert tells CNN the figure being floated doesn't go nearly far enough.
On Wednesday, the four water agencies -- Metropolitan Water District of Southern California, Imperial Irrigation District, Coachella Valley Water District and Palo Verde Irrigation District -- proposed cutting their annual allotment of river water by 400,000 acre feet, or around 130 billion gallons.
The agencies also said that to make the cut, they would "would need to utilize funding opportunities" from the recently passed federal climate law, which contained $4 billion in drought relief funding.
"Given dire drought conditions across the region and dangerously low reservoir levels, we firmly believe that all water users within the Basin must take immediate voluntary actions to stabilize water supplies in the Basin's major reservoirs," the letter from the agencies stated.
The fact that California is offering to voluntarily cut some water is encouraging, Arizona water expert Sarah Porter said. But Porter, the director of the Kyl Center for Water Policy at Arizona State University, told CNN that 400,000 a year is not even 10% of California's total allocation -- and certainly not enough to save the Colorado River.
California has claim to nearly 60% of the lower Colorado River allotment.
"It's meaningful, but it won't get us over the finish line at all," Porter said. "It's a good step in the right direction, but it won't be enough to get to the goal of 2 to 4 million acre-feet."
In June, US Bureau of Reclamation Commissioner Camille Touton called for Western states to come up with a plan to slash 2-4 million acre-feet of Colorado River water usage to protect the system from collapsing. States are still negotiating a voluntary agreement, but talks have been contentious and it's unclear if or when they will produce a result that meets Touton's goal.
If states cannot come up with a voluntary plan, Touton has said the federal government will step in and make unilateral cuts.
"They all know they're in a very difficult negotiation," Porter said. "It's going to take more discussion to get where we need to go."
California Natural Resources Agency spokesperson Lisa Lien-Mager told CNN the number from the water agencies isn't a final offer, and could change depending on what kind of federal money is on the table. Another important factor for California is federal money to help save the Salton Sea.
"This is the number we wanted to put out there because we felt it was time to move the ball," Lien-Mager said. "We want to understand what the federal funding is going to look like. We want to make sure those things are going to work for us to enable this conservation to happen."
In August, the federal government announced the Colorado River will operate in a Tier 2 shortage condition for the first time starting in January as the West's historic drought has taken a severe toll on the river basin and lakes Mead and Powell -- the country's largest reservoirs.
The Tier 2 shortage means Arizona, Nevada and Mexico will have to further reduce their water usage beginning in January. Of the impacted states, Arizona will face the largest additional cuts -- 592,000 acre-feet -- or approximately 21% of the state's yearly allotment of river water.
California has not yet been forced to make mandatory cuts to its Colorado River water usage.