In his executive action, titled "Putting People over Fish: Stopping Radical Environmentalism to Provide Water to Southern California," Trump describes actions taken by the state during his first term that he said halted his administration from moving more water south "allegedly in protection of the Delta smelt and other species of fish." He accuses California of "wastefully" allowing water to flow into the Pacific Ocean and points to recent wildfires in Southern California as an example of why the region needs more water from the state's north.

Jay Lund, a professor of civil and environmental engineering at UC Davis, said the action is about Trump needing to "complain about California, and this gives him a reason without much reason."

"A lot of these water fights that play out at the federal level are like food fights in a cafeteria," he said. "Not a lot of good, productive thinking or action comes out of them."

Trump asserts that an "enormous" amount of water from Northern California snowmelt and rivers "flows wastefully into the Pacific Ocean," but Lund said the outflow plays an important role in the tidal ecosystem.

"The biggest reason that we have water flowing to the ocean is to keep the delta fresh enough so that we can export water to the south," Lund said. "We need to have some water flowing out to keep the salt out. Otherwise, we'd pump salty water to the farms and the cities."

The majority of the outflows occur during the wrong time of year when storms inundate the system, he said, and the state doesn't have the infrastructure to capture it -- nor is it always cost-effective to build such infrastructure. Lund also noted that 80% of human water use in California is for agriculture, with the remaining 20% going to cities.

Karrigan Börk, UC Davis law professor and interim director of the Center for Watershed Sciences, said that even if the Trump administration ends up wanting to get rid of environmental protections altogether, there'd be very little water left over for other uses.

"It would only free up maybe 12% more water on average and way less water during really dry years because those dry years require so much [water] to keep the delta fresh," Börk said.

Trump's action also says that "the recent deadly and historically destructive wildfires in Southern California underscore why the State of California needs a reliable water supply."

But Lund said the water shortages firefighters faced in Southern California had nothing to do with a lack of supply moving from north to south.

Southern California as a whole had enough water to fight the blazes, but he said there wasn't enough water in local storage because the fires required "a huge rate" of water use -- and with up to 100 mph winds driving flames through areas that hadn't seen rain since spring, virtually no water system would have been able to keep up.

"There was enough water in storage in Southern California to drown all the acres of fire in more than 20 feet of water," he said. "The fires were intense over a very large area for several days at a time. That's just way more than most any conceivable local water storage would be able to deliver."

Although some of the burned areas are likely connected to water systems that get some of their water from Northern California, Lund said, "the pipes are small relative to the huge rate that you need for water delivery when fighting fires of that size."

Börk compared the situation to everyone in a household taking a shower simultaneously, leaving too little hot water to go around.

"It's not that there's no water coming to your house; it's that the system in your house isn't set up to supply three showers at once," he said. "California, and especially L.A., had the water they needed. They just didn't have the plumbing to distribute it to the people who are fighting fires fast enough."

The action mentions that during Trump's first term, California sued to stop his "administration from implementing improvements to California's water infrastructure." Trump's plan, he said, would have "allowed enormous amounts of water" to flow south from Northern California.