The sinking of California
The ground is literally sinking beneath our feet in California.
Over more than a century, the state’s inhabitants have sucked up vast quantities of water from underground basins to fill our drinking glasses and irrigate the Central Valley’s croplands.
A resulting dip in the valley floor, through the phenomenon known as subsidence, represents what some hydrologists have called the single largest human alteration of the Earth’s topography.
In some places, the ground has dropped as much as 30 feet since the early 1900s.
“It really is a pretty widespread problem,” said Doug DeFlitch, chief operating officer of the Friant Water Authority, which serves the eastern side of the San Joaquin Valley.
The sinking has forced pipelines, roads, bridges and even homes out of alignment.
It’s also sharply diminished the flow of gravity-fed canals that rely on subtle changes in elevation to move water to farms and cities.
The Delta-Mendota and the Friant-Kern canals, both serving the San Joaquin Valley, and the California Aqueduct, serving Southern California, have all seen substantial declines in their carrying capacity.
And it’s getting worse. During the latest drought, hydrologists recorded subsidence of roughly a foot or more a year in the valley.
Last year’s wet winter was a godsend. But even after the record rain, parts of the eastern San Joaquin Valley sank further this year, said Michelle Sneed, a hydrologist with the U.S. Geological Society.
She added, “That just doesn’t bode well.”
The state’s water managers have been looking at quick fixes that involve tweaks to the canals’ engineering. But they are also now thinking long-term.
In 2014, Gov. Jerry Brown signed a groundwater management act that required water officials to minimize subsidence when drawing up their plans.
Sneed, who has studied subsidence in California for more than two decades, called it a landmark moment.
“We’ve had surface water governance for 100 years,” she said. “It took another 100 and a severe drought to get some legislation to start using groundwater sustainably. I mean, that’s amazing to me that that happened.”
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