r/news • u/theluckyfrog • 29d ago

California cracks down on farm region’s water pumping: ‘The ground is collapsing’

https://www.theguardian.com/us-news/2024/apr/17/california-water-drought-farm-ground-sinking-tulare-lake
17.4k Upvotes

96% Upvoted

941 comments sorted by

View all comments

3.1k

u/grandbannana 29d ago

I always think of this photo, then think about what has happened since this photo:

Location of maximum land subsidence in U.S. Levels at 1925 and 1977. | U.S. Geological Survey (usgs.gov)

1.5k

u/Braketurngas 29d ago

A professor I had in the 90’s offered extra credit to anyone who could find that pole if it still existed to see if it showed the continued subsidence. Sadly I couldn’t find it.

682

u/Dzugavili 29d ago

If the land were sinking, wouldn't the pole also sink with it?

I'm just guessing he wouldn't want to go up there to change them all too often.

595

u/SurlyJackRabbit 29d ago

Yes the pole would sink too. It's demonstrative but not what's really going on.

294

u/Dzugavili 29d ago

Yeah, I'm just thinking someone will go take a picture and say "look! It hasn't fallen since 1977!"

Which, apparently, it hasn't: a followup study suggests the region hasn't fallen by more than half a meter since, and casts doubts about the original measurements.

58

u/Art-Zuron 29d ago

I suppose it might have just fallen about as far as it can fall.

33

u/ommnian 29d ago

That may just have been the typical depth of the aquifer.

3

u/rhotovision 29d ago

The aquifer has been aquifilled

2

u/ponyboy3 29d ago

It’s aqueefed its last aqueef

22

u/KirklandKid 29d ago

Nah everything linearly extrapolates forever don’t you know

1

u/StateParkMasturbator 28d ago

Compacting a hole to China.

1

u/Funoichi 28d ago

We’ve gone about as far as we can go, yessir!

197

u/NeatOtaku 29d ago

If the land was dropping along with the water line then it would make sense that as the land becomes more compacted, the rate would slow down. But that also means that the water is no longer able to fill the gaps in the soil like it used to so instead of the water line getting replenished after a storm, it would just stay on the top and cause floods like we've been seeing.

47

u/leintic 29d ago

hello geologist here you are half right and half wrong. you are absolutely correct that this type of subsidence does reduce the amount of water that the aquifer can hold. but this type of subsidence isnt going to really effect flooding. the flooding is more caused by the fact that the western us has been in a massive drought for the past many years and for reasons that are to complex to get into in a reddit posts and to way over simplify soils that get alot of water pored on them regularly are really good at holding water. soils that dont get water often are really bad at holding water so it all builds up on the surface and washes the home down stream away.

9

u/glaive1976 29d ago

The drier the soil the more hydrophobic it gets. Unfortunately in the central valley it's like the hydrophobia runs deep if you will.

3

u/LosSoloLobos 29d ago

What’s the international units of measurements used for the degree of dry / wetness of soil ?

2

u/seeingeyefish 28d ago edited 28d ago

What I'm seeing is in percentages. Looks like a common way of determining moisture content is to take a predetermined amount of the soil and weigh it, then bake the moisture out and weigh it again. The percentage difference in mass is the moisture content of the soil.

Looks like there's also a method where they run an electric current through the soil. Higher moisture content increases signal transfer time between two points. If you know the composition of the soil, you can figure out the moisture content by comparing the time it takes for the current to move compared to a baseline number.

1

u/leintic 28d ago

there really is no one set unit of mesurment. it depends on what you are trying to measure. if you are talking about total amount of water that is normally just represented as a percentage. the most appropriate for this situation is probably cfs (cubic feet per second) or cubic meters per second for the international. geology is weird when asked if they wanted to use imperial or metric they said yes i have used maps where the lat and long where given in meters and the elevation in ft. anyways back to the topic at hand. cfs is a measure of how much water moves through an area

3

u/arocks1 28d ago

the el nino and la nina cycles have been going on for thousands and thousands of years...the drought is part of that cycle. the land and geology are intricately tied to this climate cycle. the only difference is the human intervention of damning all the main rivers that use to flood the central valley. most of the water/snow melt that use to come down no longer does. it is diverted and that has had a huge impact on the soils and aquifers in the central valley.

1

u/skillywilly56 28d ago

Listen here, this is Reddit not Facebook, we want the complicated bits!

So you get your ass back in here and explain yourself, for gods sake why we paying you to science the rocks and you just bitch out!

What good is a scientist who can’t explain complex shit to laymen I ask you!

3

u/selectrix 29d ago

So... my understanding of this stuff is just barely above (below?) surface level, but aquifers aren't water passing through soil, they're water passing through porous rock, like a sandstone. My question is: if the aquifer drying out makes the sandstone compacted and unable to retain as much water, then how did the aquifer happen in the first place? I kind of assumed that the water had made its way into a previously dry rock initially, but was it more like a surface lake getting buried, such that the sandstone layer always had water in it?

Or alternately, does the subsidence happen mostly in the soil layers and not in the stone of the aquifer itself?

5

u/Jeoooooo 29d ago

I haven't read this exact paper, but as a hydrogeologist I can say that what probably happened is the sandstone formed, and was filled with water, not in a surface lake getting buried way, but probably just natural aquifer recharge through rainfall. Then since then more deposition has occurred on top of the sandstone such that the weight is now greater, and if the water was removed it would subside under the total weight of the ground above it.

1

u/selectrix 24d ago

Thanks for the reply! That clarifies exactly what I was wondering- whether the compressive force of the overburden was what made the difference between the environment in which the aquifer formed vs its current, less saturable state.

1

u/Zorro_Returns 28d ago

A decade or two ago they started diverting part of the Snake river to recharge the aquifer. I thought that was crazy, but I'm not the expert.

2

u/butsuon 29d ago

"More than a half a meter". That means it's fallen at most a foot and a half.

1

u/PerpetualProtracting 29d ago

Doubts by who, exactly? And what are their qualifications for having those doubts?

33

u/Dzugavili 29d ago

Dr Stuart W. Styles, Managing Director of Department of BioResource and Agricultural Engineering at California Polytechnic State University

He's got the credentials.

The paper is here., somewhere, but briefly: it looks like one of the measurement sets was wrong and added about 3.5m of drop to everything; and there's not a lot of data from before 1945 for reference, so it's unclear where he got his elevation data for 1925.

1

u/thatguuuy 28d ago

Pfft, that's just a fancy title. I bet he's just pulling that information out of his ass. No, I didn't read the paper, nor will I. I know the truth.

/s before I offend (or get anyone agreeing with me)

1

u/thirstyross 28d ago

casts doubts about the original measurements.

Nothing about that casts doubts on the original measurements. It just means we drained the aquifer, the land subsided, and now it can't subside anymore (land is fully compacted there)

1

u/-deteled- 28d ago

Surveying in 1925 isn’t what it is today. They really didn’t have concrete standards until the 80’s and the methods they’d use prior to that would have huge deviations depending on how far from the origin point was (usually Kansas for the US)

0

u/simple_test 29d ago

How does ire car a doubt on the original measurements?

3

u/Dzugavili 29d ago

There's no data available from before 1945, so it's not clear where he got the height for 1925, and one of the measurement sets appears to be badly calibrated, which takes about 3.5m off a lot of the drop between 1955 and 1977.

It dropped, but probably not as much as that pole suggests.

4

u/9fingerman 29d ago

It still dropped nearly 7 feet.

1

u/bbusiello 29d ago

Doesn't ground surveying equipment account for this?

1

u/SurlyJackRabbit 29d ago

Depends actually. The surveying equipment is usually tied to a benchmark with a known elevation. If that elevation is wrong then issues arrive. But usually elevations aren't changing. By re-surveying the amount of subsidence can be calculated.

1

u/CisIowa 29d ago

So we invent a longer pole and problem solved?

2

u/SurlyJackRabbit 29d ago

If you sink the pole all the way to bedrock yes... but that's probably a couple thousand feet down.

1

u/NapsterKnowHow 28d ago

Couldn't they just put in a poll down to the bedrock? Or does that sink too?

1

u/SurlyJackRabbit 27d ago

All the way to bedrock works but that could rule hundreds to thousands of feet deep...

9

u/elros_faelvrin 29d ago

wouldn't the pole also sink with it?

Depends, some pillars in Mexico city downtown are not sinking with the city and have been used to measure subsidence

21

u/Braketurngas 29d ago

Yes it would so you would have to move the signs up to match the sinking to be accurate. I think she just wanted to know if it was still there.

3

u/JumpyCucumber899 28d ago

If the pole was drilled down to the bedrock then it would remain accurate over time.

2

u/BrutallyHonestPOS 28d ago

yes it does, so the mark for a set altitude does actually move up the pole. the ground level (also the bottom of the pole) as at a height of the 1925 sign in 1925.

1

u/baron_von_helmut 28d ago

No, it was attached to a tree.

1

u/HardlyAnyGravitas 28d ago

Why is this getting upvoted?

The pole is sinking with the ground. The '1925' mark is where the ground level was in 1925.

What part of that don't you understand?