April 05, 2015
Overpumping California Ground Water Reduces Storage Capacity
In California's Central Valley a drilling frenzy to get more water for farms is reducing the future water storage capacity of underground formations..
Scientists say some of the underground water-storing formations so critical to California’s future — typically, saturated layers of sand or clay — are being permanently damaged by the excess pumping, and will never again store as much water as farmers are pulling out.
Southern San Joaquin Valley ground water is most severe in overdraft.
California's problem is hardly unique. At current rates the Kansas section of the Ogallala aquifer will be depleted by 2040 and nationally the rate of draining of aquifers has accelerated since 2000 to more than double the average 20th century rate. You can check out a US Geological Service national map of aquifer depletions.
These depleted aquifers put us at much greater risk should a really long and big drought hit the West. If we hit a drought that lasts for a decade or two we will not have fully stocked aquifers to fall back on. Since I expect humans to do foolish and short-sighted things on a massive scale I have an interest in whether massive expensive engineering projects could help in a mega-drought. I'd like to know more about the cost of doing that since a warming planet makes mega-droughts more likely.
Randall Parker, 2015 April 05 07:03 PM
If you can only pump the aquifer once, do you really lose something? If you never pumped it out, you wouldn't have that water.
Normally I'm not so cynical about this but in the light of "Greens" favoring coal-fired power over nuclear I am inclined toward satire regarding anything they might value.
So, if they ever arrive at the point where they have water to return to it, they use some variant of fracking to restore the capacity. Seems like a non-issue. Compared to, say, massive sinkholes opening up under homes and businesses, which is probably a more realistic consequence of emptying the aquifer.
I have to say, my immediate reaction was, 'exactly how can you 'damage' a layer of sand by pumping the water out of it? The NYTimes does not provide any support for this claim, except that it was made by 'experts'. I call bullshit. I can see how you would DEPLETE it, lower the amount of water remaining, or how you could even get subsistence of the surface, and damage to roads/bridges/whatever. But that sand isn't going to be hurt by drying out. As soon as a few wet years arrive, the acquifir is going to fill back up.
Clay is more complicated. If clay dries up, it does get hard. You take a piece of pottery clay in a ceramics class, and leave it out, it will turn into a rock. Throw that lump of air dried clay into a bowl of water, though and it will gradually turn back into clay again. It will take awhile, but we are talking hours/days not years/decades. So, yes, you could have some temporary failure to absorb water in a clay layer. But permanent damage? Again, I call bullshit.
The only way permanent damage could happen with clay would be if the surface of the clay layer was convex (and so if that top convex layer gets dry it becomes impermeable and sheds all water quickly from there on out). But that sounds like a self eliminating situation. If the layer had that basic geometry, it never would have accumulated water in the first place.
I'm betting those 'experts' are professional environmental alarmists. ie, not geologists impartially evaluating the evidence, but 'activists' -- people, who for political reasons are looking for arguments to support their case - plausible or not. Their case of course being, everywhere and always, development is bad.
I just wonder what the Chinese and Indians are going to do for their almonds?
To believe or not to believe ... the environmentalist wackos have cried "wolf" so many times.
"Scientists say some of the underground water-storing formations so critical to California’s future "
Scientists say a lot of things that aren't neccessarily so .. especially in the environmental sciences ...
I distinctly recall photographs taken from the air of large chevron shaped ponds connected to channels connecting in turn to the Colorado River that were intended to recharge an aquifer somewhere in California. These ponds had large bore well shafts drilled in the bottom that ended in the aquifer being recharged. The Ogalala is not being recharged because the water courses that charged it millions of years ago have eroded the river bottoms so far up stream that the rivers no longer follow the same course and no water now no longer gets to the aquifer.
We need to line the California coast with 4th generation safe efficient Thorium powered desalination plants. Then it wouldn't matter how many people moved into California from other countries. We'd have plenty of water for them to drink.
dlr - it's more complicated than that. You *can* damage the capacity of an aquifer by pumping water out of it. This is not my expert opinion, because I'm not being paid, but I am a licensed geotechnical engineer in California. This is not just scare stories by environmentalists.
Even a pure clean sand aquifer will lose some capacity if it's pumped, but the amount lost is small. But there aren't many clean sand aquifers - most have sand, silt. and clay. The clay is the big problem. Naturally-deposited clay has a very open structure, and can hold *lots* of water. (Bay Mud can have more water by weight than clay, and still have enough strength to recognize as a solid.) As the clay is compressed, that structure collapses, but there are still plenty of openings to hold water. Once collapsed, there's still potential for deformation as the pressure increases. Pumping water out of an aquifer increases the soil pressure, so there's deformation. *Some* of that deformation bounces back when you relieve the pressure (which happens when water goes back into the aquifer), but not all.
Mostly, you don't get permanent loss of capacity until you pump past the lowest level that the aquifer has previously been drawn down to. But once there, you do lose some capacity.
This *isn't* the problem in the Oglalla aquifer system. There, the problem is that there's essentially no natural recharge (as David Adair points out above), so while the capacity of the Oglalla is being slightly impaired, the much bigger problem is that the existing capacity isn't being recharged at anything like the rate it's being used at.
However, the water shortage California is experiencing is still mostly a political problem, not a technical problem. The water "rights" that a lot of farmers (and some other users) have do not include the right to *sell* the water. It's use it or lose it. So farmers have very little incentive to invest in water-saving equipment. Compounding the proble, there are two major Federal agencies, and the State of California, who have some say in the matter, so changing things to allow farmers to sell their water would take *more* than an Act of Congress.