Now, with a new executive order, President Donald Trump is directing federal agencies to essentially assert control over critical sections of that system, claiming mismanagement as he tries to assign blame for the wildfires in Southern California.
"Well, it's a lot of things. It's a very sweeping executive order that attempts to exempt the federal water delivery system from federal law and state law and also attempts to sort of eviscerate state control of state water resources," said Jon Rosenfield, research biologist with the environmental group San Francisco Baykeeper.
First, it helps to understand that California's water system has a kind of split personality, starting with some major dams being run by federal agencies, others by the state, along with two massive canal systems, flowing side by side in stretches. The state water project delivers much of its water to Southern California, while the federal project is a major supplier to agricultural areas in the Central Valley. For more than half a century, they've worked in a delicate balance, with coordinated agreements.
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That is, possibly, until now.
"And because these systems are so interrelated and because they have needed to coordinate so much, having one partner say we're not going to play by the rules anymore puts a tremendous burden on the other partners and really puts the entire water distribution system at great risk," Rosenfield said.
However, in the executive order, Trump directed federal agencies to deliver more water in a section called "Overriding Disastrous California Policies." And to "deliver more water and produce additional hydropower, including by increasing storage and conveyance, and jointly operating federal and state facilities, to high-need communities, notwithstanding any contrary State or local laws. The Bureau of Reclamation shall take all available measures to ensure that State agencies - including the California Department of Water Resources - do not interfere with the Bureau of Reclamation's operation of the project to maximize water delivery..."
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"These may be inconvenient environmental regulations. These are regulations, by the way, that are benefiting not just Delta communities but Bay Area communities that really rely on the San Francisco Bay Delta system for drinking water and other purposes. So, these protections are in place and in place for everybody," said John Buse, senior counsel with Center for Biological Diversity
He argues that water management had nothing to do with the Southern California wildfires. He believes it will take time to see what elements of the order actually go into effect and expects lawsuits will follow to protect water quality and the Endangered Species Act.
"This is one of many fairly far-reaching and, we think, overreaching executive orders. So, we're going to have to keep an eye on things and try to hold tight. See what comes out," Buse said.
With control of vast amounts of California water, potentially in the balance, environmental groups say one major concern is maintaining enough flow through the Delta to push back salt water and keep drinking water supplies protected.