A good overview from the New York Times.
“As the weather warms, coronavirus cases continue to decline and vaccinated Californians gleefully plot their “shot girl summers,” I regret to inform you that the Golden State’s next big disaster is already upon us.
“Yes, I’m referring to the drought gripping much of the state.
“It’s a problem that scientists are expecting to get worse this year, particularly because tinder-dry conditions are likely to lead to another devastating — not to mention long — wildfire season. But experts say the outlook isn’t all bad.
“Nevertheless, California’s drought situation is something we’ll probably be talking about a lot in coming months. Here’s what you need to know.
“How bad is the water shortage?
“It’s not good. To put it simply: California relies on wet years to replenish its water supply during dry years. And while 2019 was a flood year, the past two years have been dry.
“Last year in particular wasn’t just dry, though. “It also set the all-time records for hottest summer, and our forests caught on fire,” said Jeffrey Mount, senior fellow with the Public Policy Institute of California’s Water Policy Center. “It was a scorcher.”
“Heat compounds the effects of dryness. During every dry year, more water evaporates into the atmosphere. Plants pump more water out of the soil to survive.
“That dry soil requires earlier and more irrigation, which is where the vast majority of California’s water goes, Mount said. (Some 80 percent of water used by businesses and homes in the state goes toward agricultural irrigation.) “This is very disruptive,” he said.
“And then there’s the matter of the Oroville Dam, where damage was discovered in 2017 that could have resulted in catastrophic flooding, effectively decreasing the capacity of what Mount described as the state’s most important reservoir.
“We went in with one hand tied behind our back,” he said.
“All that combined means that California is the water equivalent of three years into a dry cycle, even though we’re only in the second dry year, Mount said. And it’s all but certain we won’t get any more significant rain this season.
“What happens when there’s so little water?
“The same thing that happens when any valuable resource becomes scarce: There’s a scramble to use it.
“With the state’s reservoirs drawn down, farmers have been forced to turn to groundwater, Mount said. The problem is that, until recently, the state’s groundwater supplies weren’t regulated, so they haven’t had a chance to recharge.
“We have been using groundwater unsustainably for more than a century,” he told me. “That’s had a cascade of unintended and unwanted consequences: community wells drying up, land subsidence of many feet, the drying up of springs and wetlands.”
“Native plants and animals, especially fish, are struggling. And problems with groundwater supplies and quality end up disproportionately affecting poorer, rural communities — home to many farmworkers.
“Why did Gov. Gavin Newsom declare a drought emergency in only part of the state? And why are some pushing him to declare one statewide?
“Earlier this month, the governor declared a drought emergency in the Russian River Watershed, where he said the drought conditions were the most severe.”
Retrieved April 30, 2021 from What to Know About California’s Drought – The New York Times (nytimes.com)