5 ms·

I’m very naive in this space. What percent of water extracted makes its way back into the water table and how long does it take? I assume you lose some to the p

I’m very naive in this space. What percent of water extracted makes its way back into the water table and how long does it take? I assume you lose some to the plant that is harvested and some to evaporation. But how much makes it back?

owyn 3y ago
I am too but the answer is zero, and nobody knows but probably a long time. The whole Central Valley is like 30 feet lower now. A bit of rain isn't going to fix that.
scheme271 3y ago
Probably just a fraction. A lot probably evaporates and anything that the plant absorbs and incorporates just goes away when crops are harvested and shipped elsewhere.
e40 3y ago
From what I’ve read, it takes a very, very long time to replenish the water table. Eons.
contravariant 3y ago
I'd see what the Dutch water suppliers have to say about it, pumping up ground water and managing the water table is kind of their thing.
- cutemonster 3y ago
  Apparently pumping up, yes, managing, less. See this comment here: https://news.ycombinator.com/item?id=39732506 https://news.ycombinator.com/item?id=39732506 > ... ground water shortages. Reason: farmers like irrigating their land (much of it below sea level) with ground water because it is cheap ...
  - contravariant 3y ago
    It should be noted however that this shortage is happening because the water suppliers are refusing to pump up more water than is sustainable. This is rather different from the free-for-all depicted in this article, and is in fact what I mean by managing the ground water.
    - yencabulator 3y ago
      They are refusing because of the previous over-pumping.
ramraj07 3y ago
Each aquifer is differen: some recharge quite fast with two rain seasons. Others take thousands of years.
westurner 3y ago
What are some solutions for water table depletion and how comparably sustainable are they? How much water is extracted from air by PV panels that output H2O, and what are the impacts? Do drilling and fracking consume lots of water and create holes through aquifers? Do holes in aquifers cause aquifers to drain out to lower chambers of the earth? Historically, people have moved to where the water is. Is there a subsurface ocean on Earth or Mars? Is there enough of a thermal gradient between very deep wells and surface water to generate energy? How many humans operating humanoid robots operating construction equipment does to take to build irrigation canals? Perhaps helpful new solar distillation tech for #Goal6 #CleanWater: - "Desalination system could produce freshwater that is cheaper than tap water" (2023) : "Extreme salt-resisting multistage solar distilation with thermohaline convection" (2023) https://news.ycombinator.com/item?id=39507692 https://news.ycombinator.com/item?id=39507692 Perhaps there are already sustainable salt-tolerant plants without GM; algae, kelp, sargassum There is plenty of salt water on Earth. Does life on earth depend upon and/or derive from ocean thermohaline cycles?
- fredrikholm 3y ago
  > What are some solutions for water table depletion and how comparably sustainable are they? Water harvesting has been successfully applied to thousands of villages in India and parts of northern Africa. The Paani Foundation is especially amazing, as they annually lift hundreds of villages from dry wells and tanker dependence to tens of feet of water in wells and ponds in as little as one rain season using nothing but planning and cheap labour (the villagers).
- westurner 3y ago
  I see videos of successful bund dig operations; digging half-craters to catch water apparently keeps the water from flashing off. Tilling turns topsoil to dirt due to solar radiation. No-till farming methods like residue mulching prevent soil depletion and retain water in topsoil; in order to create healthy soil as an output. Hugelkultur is basically residue mulching and rainwater catchment. Removing all of the trees reduces the level of water in the air and soil. What sorts of agricultural machines can service bunds, raised beds, and hugelkultur mounds instead of rows?
heavyset_go 3y ago
You can think of the water as ancient. It's been there for a while and it took a long time to get there.
dreamcompiler 3y ago
The water in most of the big US aquifers is at least 10,000 years old. There are some exceptions like the Edwards Aquifer in Texas but for most, rainwater is irrelevant. The water was put there by glaciers during the last ice age and once it's gone, it's gone forever. This is why most groundwater pumping is properly called water mining.
- lifeisstillgood 3y ago
  I simply assumed it was refilled by rain … darn half remembered geography lessons! Amazing - if it was a mineral or metal then there would be a mining company charging market rates for the mining … what is happening in this case?
  - owyn 3y ago
    It's a pretty great deal if you are a farmer. In California, you have unlimited rights to pump water from your own land, which extends to the ground underneath. So they just keep drilling deeper. Such a great system for the people who own land, I have no idea why anyone would complain about it...
WithinReason 3y ago
FTA: "Irrigation is responsible for around 70 percent of the global underground water withdrawals, which are estimated at more than 200 cubic miles per year. This exceeds recharge from rainfall by nearly 70 cubic miles per year." So 65% makes it back.
- _heimdall 3y ago
  These numbers could be wildly innacurate. We have no good way of measuring this at scale and end up using modeling to answer these questions. Models are only as food as the inputs though, and we don't know what we don't know.
_heimdall 3y ago
In the real world these systems are way too complex to have specific answers like this. We simply don't know, and have no way of knowing for sure. The best, and my opinion only reasonable, answer to that kind of scenario is to just not intervene. We shouldn't be sucking water out of aquifers at such a scale that the water level drops when we have no idea of the long term impacts.

owyn 3y ago

I am too but the answer is zero, and nobody knows but probably a long time. The whole Central Valley is like 30 feet lower now. A bit of rain isn't going to fix that.

scheme271 3y ago

Probably just a fraction. A lot probably evaporates and anything that the plant absorbs and incorporates just goes away when crops are harvested and shipped elsewhere.

e40 3y ago

From what I’ve read, it takes a very, very long time to replenish the water table. Eons.

contravariant 3y ago

I'd see what the Dutch water suppliers have to say about it, pumping up ground water and managing the water table is kind of their thing.

cutemonster 3y ago
Apparently pumping up, yes, managing, less. See this comment here: https://news.ycombinator.com/item?id=39732506 https://news.ycombinator.com/item?id=39732506 > ... ground water shortages. Reason: farmers like irrigating their land (much of it below sea level) with ground water because it is cheap ...
- contravariant 3y ago
  It should be noted however that this shortage is happening because the water suppliers are refusing to pump up more water than is sustainable. This is rather different from the free-for-all depicted in this article, and is in fact what I mean by managing the ground water.
  - yencabulator 3y ago
    They are refusing because of the previous over-pumping.

ramraj07 3y ago

Each aquifer is differen: some recharge quite fast with two rain seasons. Others take thousands of years.

westurner 3y ago

What are some solutions for water table depletion and how comparably sustainable are they? How much water is extracted from air by PV panels that output H2O, and what are the impacts? Do drilling and fracking consume lots of water and create holes through aquifers? Do holes in aquifers cause aquifers to drain out to lower chambers of the earth? Historically, people have moved to where the water is. Is there a subsurface ocean on Earth or Mars? Is there enough of a thermal gradient between very deep wells and surface water to generate energy? How many humans operating humanoid robots operating construction equipment does to take to build irrigation canals? Perhaps helpful new solar distillation tech for #Goal6 #CleanWater: - "Desalination system could produce freshwater that is cheaper than tap water" (2023) : "Extreme salt-resisting multistage solar distilation with thermohaline convection" (2023) https://news.ycombinator.com/item?id=39507692 https://news.ycombinator.com/item?id=39507692 Perhaps there are already sustainable salt-tolerant plants without GM; algae, kelp, sargassum There is plenty of salt water on Earth. Does life on earth depend upon and/or derive from ocean thermohaline cycles?

fredrikholm 3y ago
> What are some solutions for water table depletion and how comparably sustainable are they? Water harvesting has been successfully applied to thousands of villages in India and parts of northern Africa. The Paani Foundation is especially amazing, as they annually lift hundreds of villages from dry wells and tanker dependence to tens of feet of water in wells and ponds in as little as one rain season using nothing but planning and cheap labour (the villagers).
westurner 3y ago
I see videos of successful bund dig operations; digging half-craters to catch water apparently keeps the water from flashing off. Tilling turns topsoil to dirt due to solar radiation. No-till farming methods like residue mulching prevent soil depletion and retain water in topsoil; in order to create healthy soil as an output. Hugelkultur is basically residue mulching and rainwater catchment. Removing all of the trees reduces the level of water in the air and soil. What sorts of agricultural machines can service bunds, raised beds, and hugelkultur mounds instead of rows?

heavyset_go 3y ago

You can think of the water as ancient. It's been there for a while and it took a long time to get there.

dreamcompiler 3y ago

The water in most of the big US aquifers is at least 10,000 years old. There are some exceptions like the Edwards Aquifer in Texas but for most, rainwater is irrelevant. The water was put there by glaciers during the last ice age and once it's gone, it's gone forever. This is why most groundwater pumping is properly called water mining.

lifeisstillgood 3y ago
I simply assumed it was refilled by rain … darn half remembered geography lessons! Amazing - if it was a mineral or metal then there would be a mining company charging market rates for the mining … what is happening in this case?
- owyn 3y ago
  It's a pretty great deal if you are a farmer. In California, you have unlimited rights to pump water from your own land, which extends to the ground underneath. So they just keep drilling deeper. Such a great system for the people who own land, I have no idea why anyone would complain about it...

WithinReason 3y ago

FTA: "Irrigation is responsible for around 70 percent of the global underground water withdrawals, which are estimated at more than 200 cubic miles per year. This exceeds recharge from rainfall by nearly 70 cubic miles per year." So 65% makes it back.

_heimdall 3y ago
These numbers could be wildly innacurate. We have no good way of measuring this at scale and end up using modeling to answer these questions. Models are only as food as the inputs though, and we don't know what we don't know.

_heimdall 3y ago

In the real world these systems are way too complex to have specific answers like this. We simply don't know, and have no way of knowing for sure. The best, and my opinion only reasonable, answer to that kind of scenario is to just not intervene. We shouldn't be sucking water out of aquifers at such a scale that the water level drops when we have no idea of the long term impacts.