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Comment by tzs | Hacker News Reader

> So, next time you see a truckload of hay going west on the freeway give it a wave!

> Wave goodbye to $13,000 worth of scarce water that was sold to agribusiness for just $1,000 and is now headed overseas on that truck

Actually there is only about $0.65 worth of water headed overseas on that truck because while it takes 5 or 6 acre feet of water to grow an acre of alfalfa only 0.005% of that water actually ends up in the part of the plant that is harvested and ends up on that truck.

Where does the other 99.995% end up? I have no idea because every single article I've seen about water use in agriculture fails to cover what happens to that water.

All I've been able to find is that almost all of it goes into the air around the farms via evapotranspiration. But what happens after that?

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As far as I can tell, there are four things that can happen to the water:

- it runs off or trickles away - probably negligible here

- it evaporates before it's absorbed by the plant - mostly due to wasteful irrigation practices. Unless you're doing drip-irrigation or similar, this is where most of your water will end up

- it's absorbed by the plant and used in photosynthesis to make sugar and eventually other molecules - this is what's on the truck, but by mass it's negligible

- it's absorbed by the plant and used for nutrient transfer - this is what happens to most water plants consume. In simplified terms, capillary action drives water up the plant, bringing nutrients with it; evaporation removes water at the leaf so that new water comes in

According to Wikipedia the last effect (Transpiration) accounts for 97–99.5% of water actually used by the plant [1]

1: https://en.wikipedia.org/wiki/Transpiration

Of moderate significance: it can seep downwards and become groundwater.

> But what happens after that?

Eventually, rain. Usually somewhere else.

> Actually there is only about $0.65 worth of water headed overseas on that truck because while it takes 5 or 6 acre feet of water to grow an acre of alfalfa only 0.005% of that water actually ends up in the part of the plant that is harvested and ends up on that truck.

Apple doesn't give me a discount on my Macbook to account for the material they burned/trashed during its manufacture.

Well, water isn't really "used". It eventually always evaporates and falls back down to earth. It's only used if some chemical process alters the molecule in some reaction.

The problem is 100% of the original water is no longer where you need it, not that some percentage gets into the plant or not.

The cost of water is all about moving it and/or filtering it. The analogy that it's a water export oversees applies when you think that they'd have to move that water from somewhere else otherwise to grow that alfalfa. Not that the alfalfa "has" the water.

Also, moving insane amounts of water to the desert for an incredibly water hungry plant, because desert land is cheap, and the moving of that water is underpriced... is kind of insane.

It's an irrelevant distinction.

If the water went into the alfalfa and 100% of it evaporated, leaving bone-dry hay going to the middle east, then the hay is still the only remaining symbol of $13,000 worth of water you used to have, and sold for $1000.

Where the exact losses are within the industry is entirely unimportant.

If I use 74 tons of 24 karat gold to create one plant - I don't care much about how much gold is in the plant. I care about how much less gold I have now.

It depends a lot on where the farm is, how much they irrigate, and when they irrigate. But often something like >90% of the water goes back into the ground, where it will eventually make its way back into the aquifers and rivers.

It's why often farm water usage is not nearly as bad as it superficially seems, and why farm water usage of a river can be multiples of the actual river flow

That’s a good point, to be useful to plants the water has to get into the ground. From there it’s either evaporating or moving into aquifers.

If that is true, then why are there so many hundreds of HN users talking about crazy water usage by farms?

(In this and the past few hundred posts related to this topic that made it to the front page.)

Because this defense doesn't solve the issue that the water is being used faster than it's being replenished. The biggest issue with this is on wells which are sucking so much water out of the ground it's collapsing the ground itself, in ways that are likely permanently lowering the water capacity of the ground. Even if it doesn't the run-off water isn't going back into those deep aquafers.

https://blogs.agu.org/geospace/2019/03/19/western-droughts-c...

Perhaps it's the same reason that in the Yudkowsky vs Hotz podcast yesterday, Hotz didn't know what a gelding was despite being incredibly smart -- zero farm experience.

I mean, farms come in a lot of varieties. Entirely possible for one to be successful at cranberry farming but know little about many/most/all animals (that don’t attack their crops).

To be fair, geldings aren't really a part of modern farm life. Steers and barrows are still common if you're in livestock, maybe wethers, but horses are more a hobby and only coincidentally associated with farms.

Eventually making it back into aquifers could mean that in 500 years it mostly ends up in an aquifer near somewhere 500 miles down river/wind or something similarly unhelpful to the region in the short term.

> It's why often farm water usage is not nearly as bad as it superficially seems, and why farm water usage of a river can be multiples of the actual river flow

It's bad enough that not only is a huge share of river water used, but that the actual ground is sinking in the Central Valley from depletion of groundwater resources:

https://en.wikipedia.org/wiki/Central_Valley_land_subsidence

> But often something like >90% of the water goes back into the ground, where it will eventually make its way back into the aquifers and rivers.

That's not the case in the lower Colorado basin. If it was, there would not be a problem.

I'm not familiar with that area, but considering it's not coastal it seems hard to believe the water is simply wasted once it goes into the ground in the lower Colorado basin.

Imperial county is not actually that far from the mouth of the Colorado... Except that, for practical purposes, it does not have a mouth any more, on account of all the water being taken from it.

My guess is that most of what sinks into the ground from agriculture makes its way to a saline aquifer. Some of it may end up in the Salton Sea, which itself is very saline and also shrinking.

Sure, 90% is an overestimate of the portion of water applied for irrigation that returns as recharge to the groundwater system.

However that number is not zero in the Lower Colorado River basin. I work in groundwater modeling for various clients in the desert southwest, the number we assume for agricultural return flow recharge varies based on crop type and other factors. 90% is an overestimate, 0% is an underestimate

What's a ballpark figure for alfalfa in Imperial county?

Clearly not the case in the San Joaquin valley, there is massive subsidence and the Kern river and Tulare lake disappeared (notably exception is this year due to exceptional snowfall).

> It's why often farm water usage is not nearly as bad as it superficially seems, and why farm water usage of a river can be multiples of the actual river flow

This is beside the point.

The issue is the reservoirs. If the reservoirs and sources are being depleted faster than they replenish then their levels go down.

The water crises are about the reservoirs and sources going down. We don’t care how much farmers use in absolute numbers as long as it’s not overwhelming the capacity of the systems to replenish themselves.

When we pay $1,000+ per pill for our newest cancer drug we are not paying $1,000 for the few micrograms of active ingredients. Same in agriculture, when we say, "It takes 5 gallons of fuel to produce 1 gallon of soybean oil" we don't mean of course that there is ANY fuel IN the soybean oil (WE HOPE!). Same with water, we say it takes about 1 gallon of water to grow 1 almond, again, there is not actually 1 gallon of H20 in each almond.

> When we pay $1,000+ per pill for our newest cancer drug we are not paying $1,000 for the few micrograms of active ingredients.

My usual statement is that the first (approved) microgram costs a billion dollars, the rest of the doses are basically free. Commence pricing games to sort that out.

There's a big difference between fuel and water.

When that 5 gallons of fuel is used to produce 1 gallon of soybean oil the fuel is consumed. It undergoes a chemical transformation that results in it becoming non-fuel.

When 1 gallon of water is used to grow 1 almond, only a very tiny amount of the water undergoes a chemical transformation into non-water. The rest (over 99.9% of it) remains as water at the almond farm.

It is no longer in easily accessible pipes or storage tanks, instead becoming water vapor in the air or moisture in the soil, but it is still water. It is going to end up eventually in someplace where it will be usable.

In Imperial County, a lot of it ends up in the Salton Sea, where the nutrients it carries from the farms eutrophicate the water, the resulting algal blooms kill most of the fish, leaving rotting carcasses all over the shoreline, and also downstream killing a bunch of migratory birds that normally stop there to eat and now have no food.

It’s simple: It starts the journey back to rainwater and then reservoirs, but it takes a long time.

If you deplete the reservoirs and sources faster then the cycle replenishes them, you eventually have a problem when they get too low.

Abnormally hot or dry years become disasters if you’ve depleted your reservoirs too much.

That is the problem.

Also, water evaporating off a plant in California is not guaranteed to make it back into the Californian water system.

They use flood irrigation. How Efficient is Flood Irrigation? Flood irrigation is 50 to 60% water efficient, meaning 50 to 40% of water released in a flood irrigation system is lost either to runoff or rapid soil infiltration. Flood irrigation is the least water-efficient irrigation system.

https://www.agrivi.com/blog/modern-management-of-centennial-....

And then you have to imagine that these places are hitting 110+ degrees recently, so they lose even more water.

I would imagine some percentage drains into the soil. Not all the remaining water will be absorbed by the root system of the alfalfa plants

Such a flawed argument I don't know where to start

I have the same kind of issue with people arguing that beef production uses to much water. In The Netherlands. One of the wettest deltas on earth. Where it rains almost daily and cattle mostly drinks surface water that normally gets drained to the sea.

I’m an environmentalist myself, but repeating statistics without asking yourself if they are relevant is useless.

In this case though, the farms are using up water that doesn’t get replenished. You don’t need any statistics to show that this is not sustainable.

https://oec.world/en/profile/bilateral-product/bovine-meat/r...

> In 2021, Netherlands imported $1.77B in Bovine Meat, becoming the 5th largest importer of Bovine Meat in the world.

Maybe they're talking about the global impact?

Yes, and many are concerned with the biggest issue from beef production, not how much they consume but how much waste they produce, mostly methane.

True, but that’s not my point.

And we exported $2.56B according to that source. If you have leave people guessing on what your statistics mean, they’re useless.

We have a harbor, everything that goes to Europe is counted as import and export. What does that mean for these numbers? Nobody knows.

And the beef that is imported is probably from Ireland and the UK. Do they have deserts there? So even that number is useless.

You’re just another example of someone repeating statistics that only lead to irrelevant discussions.

> And we exported $2.56B according to that source.

If I have two babies, but murder one person, the net increase isn't really what folks will focus on. Environmental concerns with the beef industry are global because, as those import/export numbers show, it's a global industry. The Netherlands may be a good place to raise cattle water-wise, but unless you're gonna grow them all there, it doesn't really remove their impact elsewhere.

You’re mixing up different arguments making it impossible to respond.

It's the same argument throughout; that "people arguing that beef production uses to much water" in the Netherlands aren't necessarily scoping their discussion to just the Netherlands, but the global beef industry and its impacts.

"But it's wet here!" really misses their point.

Politicians here used it as a real argument during discussions about Dutch beef production. And sadly it went unchallenged. It’s still often repeated by people who are overly fanatic.

https://en.wikipedia.org/wiki/Induced_demand

Link dropping without context is just rude. Abusing statistics to make an invalid point is annoying no matter the actual goal.

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