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Ancient water is no easy gift

There was big, very big, ground water news for California in 2016, but almost no one paid attention because it came in the midst of the most heated presidential campaign in modern memory. For those who did notice, it seemed almost like Christmas came early, at midyear.

The news was this: A Stanford University study found huge and previously unknown supplies of ground water far beneath the surface of the ever-thirsty Central Valley. At a minimum, the newfound water supply amounts to twice the amount pumped from Central Valley aquifers since California was settled, or about 270 million acre feet (one acre foot is the amount of water needed to cover an acre of land with one foot of water, or 325,851 gallons, weighing about 1,303 tons).

The total weight of all the water on hand amounts to about 2,700 billion tons, the Stanford researchers estimated.

This good news seemed to bring a sense of relaxation to big farms that have used more than 125 million acre feet of ground water over the last century or so (figures for ground water use are notoriously imprecise). But the efforts of water districts to draft new ground water rules under a 2014 state law nevertheless continued, and that turns out to be a good thing.

For getting the “new” supplies the researchers found by examining data from 35,000 water wells and 938 oil and gas wells turns out to be pretty complicated and uncertain.

For one thing, the suddenly discovered many, many millions of acre feet are not exactly staring anyone in the face. Most of them are pooled at depths between 1,000 and 10,000 feet below the face of the earth, the bulk at levels a mile or more down. A 400-foot water well now typically costs between $6,000 and $12,000 to drill, depending on the geology involved. Adding a well cap to keep the water supply free of vermin can cost thousands more. No one is quite clear how much a 9,000-foot well might run.

There’s also the likelihood that the water might be salty, as a rule of thumb says that the deeper it sits, the saltier the water. For sure, the deeper you go, the older the water you’ll find. Researchers have estimated much of the newly-found California supply might have been in place more than 20,000 years, so there’s a good chance it would have to be desalinated. It might also need to be purified in other ways, if residue from oil and gas drilling or fracking has trickled into it.

There could be a few other problems with pumping water up from thousands of feet underground. One is subsidence. The floor in many parts of the Central Valley today is about 30 feet lower than it was 1925, the result of groundwater pumping. Emptying deep-down basins of the water that has filled them for eons could see far more land sinking much farther. Even without using this water, the agricultural region has seen steady sinking every year for decades. Government pays billions of dollars every year to fix sinking bridges, cracking irrigation canals and buckling highways caused by subsidence.

Pumping that water also is a one-and-done deal. Since it would take much more than 50 years to refill basins that don’t collapse, this is water that can essentially be used once, and never again. Even if it’s a little cheaper to desalinate and clean than sea water, at least the oceans are rising these days — despite President-elect Donald Trump’s claim that climate change is a scam — unlike California’s ground water levels.

The upshot is that even though Californians now know there’s far more water underground than anyone thought possible a year ago, this is no easy-to-unwrap Christmas gift. Rather, it’s a supply that should only be exploited in a time of maximum desperation, a condition California has not come close to reaching.

And that means the pokey timetable of that 2014 ground water law should be speeded up, its 2030 deadline for meaningful regulations moved up by a period of at least five to seven years if the state is serious about conserving and replenishing accessible ground water found fairly close to the earth’s surface.

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