Wednesday, July 18, 2018

A Sign of the Times - Water and Arsenic

There's your problem.

52 years worth of subsidence in California's San Joaquin Valley. And there's been another four decades of subsidence since this image.

Now the water-strapped Central Valley has another scourge - arsenic.

Towns across the Central Valley region of California have had tap water arsenic levels above the federal limit for almost two decades, levels that research suggests can raise the risk of a variety of cancers and lower IQ in children. During the same period, locals and scientists have noticed another odd phenomenon: the valley is sinking, at rates as fast as 25cm a year. Now it seems that the two problems are connected.

...Over the past century, groundwater levels in some places have fallen as much as 200 meters during drought conditions, according to the United States Geological Survey. The subsequent changes in water pressure alter underground architectures, leading to a sometimes-surreal slumping of land by as much as 10 meters.

...The same subsurface change in pressure can suck arsenic out of layers of clay and into groundwater, like a sponge being squeezed, said Dr Scott Fendorf, a professor of earth science at Stanford University and a co-author of a new study on the subject. “When we’re overdrafting the aquifer, the two things happen simultaneously.”
The article discusses the perils and tribulations of the people of the Central Valley in their pursuit of clean, consumable freshwater. What is not mentioned is what the arsenic is doing to the crops they're growing and selling. 


Toby said...

Are Californians beginning to accept recycling water as an option yet? Or is that still to icky to contemplate?

The Mound of Sound said...

I still don't think they're at the point where severe conservation measures will be embraced - until the next mega-drought, that is.

Purple library guy said...

At that rate it's all going to be moot when they just run out of groundwater, drought means rivers from elsewhere are mostly out of water before they reach California, they get nothing from snowpack, and agriculture (and maybe habitation) in much of California becomes impossible. If you got no water, it won't be laced with arsenic, and if you produce no vegetables, they won't have arsenic on them.
In a big swath of the southern US, it seems like climate change drought is happening simultaneously with running out of "fossil" groundwater--something of a "perfect storm" that could render huge areas uninhabitable.