4 ms·

I never quite got what "it takes x gallons" actually means. Where does the water go? Does it get sucked up by the plant somehow? Does the plant split the water

by rb2k_ 12y ago

I never quite got what "it takes x gallons" actually means. Where does the water go? Does it get sucked up by the plant somehow? Does the plant split the water into oxygen/hydrogen and those get bound to some other atom? Does it just disappear into the ground and end up as groundwater? Does it just evaporate and rain down somewhere else? Does it end up going to a river and ending up in the ocean as saltwater? (Actual question)

vacri 12y ago
It evaporates through the leaves of the tree, as the plant respires. One tree produces X amount of almonds/year, and requires Y amount of water to stay healthy. Y/X gives you the water-per-almond. Most of what makes up a tree's physical substance is pulled from the air, but it still needs some nutrients from the soil and water to move those nutrients in order to survive.
- Almaviva 12y ago
  So if it evaporates, as in the parent question, what does "requires 1 gallon of water" mean? One gallon goes back in the air, right? It will presumably end up as rain? So the net loss of water is 0, or am I missing something? Is there some loss that is permanent or slow to recover, here?
  - rb2k_ 12y ago
    I guess the main problem is that the rain might fall somewhere else that is not California and we now have to move that water back there because otherwise they'd run out.
  - danjayh 12y ago
    This would be true if they were actually getting rain, and they were using surface water, but that is not the case. They are in the middle of a drought, and they are using ground water, which replenishes very slowly.
  - thrownaway2424 12y ago
    I don't think anybody is claiming that California's drought is due to a violation of the principle of conservation of matter, however rain that falls on distant lands is surprisingly useless.
  - fiblye 12y ago
    It means that one gallon of water that could've been used elsewhere in California during the period of growth went into the clouds and is likely going to rain down a few thousand miles away. The point of the "n gallons of water per x fruit" is saying that one certain crop is incredibly inefficient with its water consumption, and it'd be better to use it on something else. It's like saying a bloated web browser consumes 500 MB of memory/tab. Your memory isn't gone forever after you use it, but so long as you're using that browser or growing that crop, it's draining that resource away from other applications. You probably only have 8-16 GB of memory to use at once, just like a region only has N gallons of water it can use at any one time.
  - analog31 12y ago
    In a localized sense, the loss is of the water that's readily available for use in that region. I suppose you could think of it as a sort of "debt," where you measure the loss in terms of energy or dollars required to restore the water at the rate it's being consumed, for instance through desalination. I suspect it's just simpler to call it "loss of water." Another way to think about it, is that farming has historically occurred in places where there are decent natural growing conditions: Climate, soil, and water. If you let the water go somewhere else, through evaporation and rainfall, then you might end up having to maintain growing conditions artificially by bringing the water to where there is decent climate and soil. And again, you could measure the cost of doing that as a "debt."
  - vacri 12y ago
    The water cycle has a net loss of 0, but only on a global scale. Water that is expired by a tree and ends up as vapour in the air does not precipitate straight out again, unless the air is already completely saturated (ie: it's already raining/snowing). That water will indeed come down again... somewhere. In general, something needs to change for the water vapour to turn into rain, like changing altitude from passing over a mountain (reducing temperature and pressure), or the air stream combining with a colder one. Deserts tend to be flat and featureless, so there's little in the way of atmospheric change as you pass through them. An interesting example of this is the continent of Australia - the most populated part is on a thin strip on the east coast as that's where the water and hence arable land is. But the air moves across the continent from the west - in general, the air crosses an entire continent before giving up it's water. It gives up that water because it hits the long strip of mountains slightly inland from the east coast, which changes the conditions appropriately. But until it hits those mountains, the entire overland journey is very consistent for the vapour, so it stays as vapour. There are several mechanisms at play here in dumping the water from vapour into rain - check out wikipedia, I couldn't do them all justice.
  - manicdee 12y ago
    That gallon of water used to water that tree right now is not available to me to shower, drink, or flush right now. The water becomes immediately unavailable until it returns to the ground as rain somewhere or someWHEN else. Sure, looking at the big picture the water is never actually "lost". Until you can plumb my domestic water into the clouds directly, the big picture is irrelevant. All that matters is the water that is available in a potable form for me to drink right now. In financial systems, we might come to an arrangement that I will pay you Friday for a burger Tuesday. With water, it doesn't work like that. If I don't have water now at the time I need it, there is no use promising me water late next week. And when it comes to a decision between me having a litre of water today for me to survive on, or saving your thousand-dollar almond tree, I will unashamedly pick me.
pmorici 12y ago
This USGS website explains the various forms of water loss... https://water.usgs.gov/edu/watercycleevapotranspiration.html https://water.usgs.gov/edu/watercycleevapotranspiration.html Assuming the farmers are irrigating efficiently then most of the water is being lost to evapotranspiration aka the plants sweating it out through their leaves. Almond trees let more water escape through their leaves than say a cactus might and that is why it takes more water to keep them healthy.
- rb2k_ 12y ago
  So I guess the main problem is that the rain might fall somewhere else that is not California and we now have to move that water back there because otherwise they'd run out.
  - tracker1 12y ago
    I still think that water desalinization improvements should see a lot more funding... and that cross-country water pipelines from the areas that commonly flood over, to the southwestern US should be started. Combined with wind and solar power, this can be used as a fuel source (hydrogen storage)... it's rather short sighted that such efforts haven't been made in this country starting years ago.
- deleted 12y ago
  [deleted]
- benihana 12y ago
  Can they not put plastic covers like that around the trees and capture water that way? Or does that kill the tree?

by rb2k_ 12y ago

vacri 12y ago

It evaporates through the leaves of the tree, as the plant respires. One tree produces X amount of almonds/year, and requires Y amount of water to stay healthy. Y/X gives you the water-per-almond. Most of what makes up a tree's physical substance is pulled from the air, but it still needs some nutrients from the soil and water to move those nutrients in order to survive.

Almaviva 12y ago
So if it evaporates, as in the parent question, what does "requires 1 gallon of water" mean? One gallon goes back in the air, right? It will presumably end up as rain? So the net loss of water is 0, or am I missing something? Is there some loss that is permanent or slow to recover, here?
- rb2k_ 12y ago
  I guess the main problem is that the rain might fall somewhere else that is not California and we now have to move that water back there because otherwise they'd run out.
- danjayh 12y ago
  This would be true if they were actually getting rain, and they were using surface water, but that is not the case. They are in the middle of a drought, and they are using ground water, which replenishes very slowly.
- thrownaway2424 12y ago
  I don't think anybody is claiming that California's drought is due to a violation of the principle of conservation of matter, however rain that falls on distant lands is surprisingly useless.
- fiblye 12y ago
  It means that one gallon of water that could've been used elsewhere in California during the period of growth went into the clouds and is likely going to rain down a few thousand miles away. The point of the "n gallons of water per x fruit" is saying that one certain crop is incredibly inefficient with its water consumption, and it'd be better to use it on something else. It's like saying a bloated web browser consumes 500 MB of memory/tab. Your memory isn't gone forever after you use it, but so long as you're using that browser or growing that crop, it's draining that resource away from other applications. You probably only have 8-16 GB of memory to use at once, just like a region only has N gallons of water it can use at any one time.
- analog31 12y ago
  In a localized sense, the loss is of the water that's readily available for use in that region. I suppose you could think of it as a sort of "debt," where you measure the loss in terms of energy or dollars required to restore the water at the rate it's being consumed, for instance through desalination. I suspect it's just simpler to call it "loss of water." Another way to think about it, is that farming has historically occurred in places where there are decent natural growing conditions: Climate, soil, and water. If you let the water go somewhere else, through evaporation and rainfall, then you might end up having to maintain growing conditions artificially by bringing the water to where there is decent climate and soil. And again, you could measure the cost of doing that as a "debt."
- vacri 12y ago
  The water cycle has a net loss of 0, but only on a global scale. Water that is expired by a tree and ends up as vapour in the air does not precipitate straight out again, unless the air is already completely saturated (ie: it's already raining/snowing). That water will indeed come down again... somewhere. In general, something needs to change for the water vapour to turn into rain, like changing altitude from passing over a mountain (reducing temperature and pressure), or the air stream combining with a colder one. Deserts tend to be flat and featureless, so there's little in the way of atmospheric change as you pass through them. An interesting example of this is the continent of Australia - the most populated part is on a thin strip on the east coast as that's where the water and hence arable land is. But the air moves across the continent from the west - in general, the air crosses an entire continent before giving up it's water. It gives up that water because it hits the long strip of mountains slightly inland from the east coast, which changes the conditions appropriately. But until it hits those mountains, the entire overland journey is very consistent for the vapour, so it stays as vapour. There are several mechanisms at play here in dumping the water from vapour into rain - check out wikipedia, I couldn't do them all justice.
- manicdee 12y ago
  That gallon of water used to water that tree right now is not available to me to shower, drink, or flush right now. The water becomes immediately unavailable until it returns to the ground as rain somewhere or someWHEN else. Sure, looking at the big picture the water is never actually "lost". Until you can plumb my domestic water into the clouds directly, the big picture is irrelevant. All that matters is the water that is available in a potable form for me to drink right now. In financial systems, we might come to an arrangement that I will pay you Friday for a burger Tuesday. With water, it doesn't work like that. If I don't have water now at the time I need it, there is no use promising me water late next week. And when it comes to a decision between me having a litre of water today for me to survive on, or saving your thousand-dollar almond tree, I will unashamedly pick me.

pmorici 12y ago

This USGS website explains the various forms of water loss... https://water.usgs.gov/edu/watercycleevapotranspiration.html https://water.usgs.gov/edu/watercycleevapotranspiration.html Assuming the farmers are irrigating efficiently then most of the water is being lost to evapotranspiration aka the plants sweating it out through their leaves. Almond trees let more water escape through their leaves than say a cactus might and that is why it takes more water to keep them healthy.

rb2k_ 12y ago
So I guess the main problem is that the rain might fall somewhere else that is not California and we now have to move that water back there because otherwise they'd run out.
- tracker1 12y ago
  I still think that water desalinization improvements should see a lot more funding... and that cross-country water pipelines from the areas that commonly flood over, to the southwestern US should be started. Combined with wind and solar power, this can be used as a fuel source (hydrogen storage)... it's rather short sighted that such efforts haven't been made in this country starting years ago.
deleted 12y ago
[deleted]
benihana 12y ago
Can they not put plastic covers like that around the trees and capture water that way? Or does that kill the tree?