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Are there good figures on how much of that water is “wasted” and how much ends up replenishing groundwater reservoirs? Utah isn’t that close to the Pacific so t

by User23 5y ago

Are there good figures on how much of that water is “wasted” and how much ends up replenishing groundwater reservoirs? Utah isn’t that close to the Pacific so that water has a lot of opportunities to do something other than flow into the ocean.

fooey 5y ago
I don't know any numbers, but we're over 100 all summer, so I imagine it mostly evaporates. Flood irrigation here is just as bad as if they were doing it in Phoenix or Las Vegas
- brewdad 5y ago
  Many of the old neighborhoods and a few remaining urban farms are flood irrigated in Phoenix. The small city park in my old neighborhood was also flooded once a week to keep the grass green all summer.
ajross 5y ago
Virtually all agricultural irrigation evaporates. It doesn't even run off into local streams (which you can verify by, heh, the lack of local streams in the Utah desert), much less seep into the ground. Underground aquifers fill over decades and centuries, and in this environment, almost always laterally, not from seepage from rainfall. I think the demand for proof needs to go the other way, honestly. Presumptively this water is pretty clearly "wasted".
- D13Fd 5y ago
  I think the question is how much less water would be used with a modern irrigation system rather than flood irrigation.
  - tfigment 5y ago
    Ostensibly you could grow hydroponically and have very little waste but order of magnitude cost increase in power needs. Every other solution falls in between I guess.
    - ashtonkem 5y ago
      Electricity is orders of magnitude easier to move than water, and its price is dropping too.
- User23 5y ago
  > Virtually all agricultural irrigation evaporates. It doesn't even run off into local streams (which you can verify by, heh, the lack of local streams in the Utah desert), much less seep into the ground. The evaporation figures I can find range from 30% to 50%, which is hardly virtually all. I've never been to the Utah desert, but in the California desert I've dumped out water and watched it disappear into the ground. The absence of streams only indicates that seepage and evaporation together get all of the water that would otherwise flow in them. > Underground aquifers fill over decades and centuries, and in this environment, almost always laterally, not from seepage from rainfall. I think the demand for proof needs to go the other way, honestly. Presumptively this water is pretty clearly "wasted". Unconfined aquifers will fill as fast as rainfall can seep in, which depending on the area can be a lot less than decades. How is letting the Colorado flow into the Pacific more of a "waste" than using that water to grow food and letting the excess seep into the water table and fall as rain on the other side of the Rockies?
  - ajross 5y ago
    Those figures are for water that doesn't enter the plants, though. All that water, except for a tiny fraction represented in the shipped output (nuts, whatever) still ends up locally in the air. And "disappearing into the ground" is absolutely not water entering an aquifer! All you get is wet dirt. Which then... dries out. Again, this isn't how aquifers work. There's no free lunch here. Growing plants in a desert under the open sky requires a staggering amount of water. It just does. If you want to push efficiency measures look at greenhouses.
    - User23 5y ago
      > Again, this isn't how aquifers work. Are you confusing confined aquifers and unconfined aquifers? That's exactly how unconfined aquifers work. Where I live the wells never go dry because every time it rains they are replenished. Maybe the desert doesn't have unconfined aquifers and that's why you're so strident on this? I really don't know, but I'm curious so please elucidate if you can.
deleted 5y ago
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by User23 5y ago

fooey 5y ago

I don't know any numbers, but we're over 100 all summer, so I imagine it mostly evaporates. Flood irrigation here is just as bad as if they were doing it in Phoenix or Las Vegas

brewdad 5y ago
Many of the old neighborhoods and a few remaining urban farms are flood irrigated in Phoenix. The small city park in my old neighborhood was also flooded once a week to keep the grass green all summer.

ajross 5y ago

Virtually all agricultural irrigation evaporates. It doesn't even run off into local streams (which you can verify by, heh, the lack of local streams in the Utah desert), much less seep into the ground. Underground aquifers fill over decades and centuries, and in this environment, almost always laterally, not from seepage from rainfall. I think the demand for proof needs to go the other way, honestly. Presumptively this water is pretty clearly "wasted".

D13Fd 5y ago
I think the question is how much less water would be used with a modern irrigation system rather than flood irrigation.
- tfigment 5y ago
  Ostensibly you could grow hydroponically and have very little waste but order of magnitude cost increase in power needs. Every other solution falls in between I guess.
  - ashtonkem 5y ago
    Electricity is orders of magnitude easier to move than water, and its price is dropping too.
User23 5y ago
> Virtually all agricultural irrigation evaporates. It doesn't even run off into local streams (which you can verify by, heh, the lack of local streams in the Utah desert), much less seep into the ground. The evaporation figures I can find range from 30% to 50%, which is hardly virtually all. I've never been to the Utah desert, but in the California desert I've dumped out water and watched it disappear into the ground. The absence of streams only indicates that seepage and evaporation together get all of the water that would otherwise flow in them. > Underground aquifers fill over decades and centuries, and in this environment, almost always laterally, not from seepage from rainfall. I think the demand for proof needs to go the other way, honestly. Presumptively this water is pretty clearly "wasted". Unconfined aquifers will fill as fast as rainfall can seep in, which depending on the area can be a lot less than decades. How is letting the Colorado flow into the Pacific more of a "waste" than using that water to grow food and letting the excess seep into the water table and fall as rain on the other side of the Rockies?
- ajross 5y ago
  Those figures are for water that doesn't enter the plants, though. All that water, except for a tiny fraction represented in the shipped output (nuts, whatever) still ends up locally in the air. And "disappearing into the ground" is absolutely not water entering an aquifer! All you get is wet dirt. Which then... dries out. Again, this isn't how aquifers work. There's no free lunch here. Growing plants in a desert under the open sky requires a staggering amount of water. It just does. If you want to push efficiency measures look at greenhouses.
  - User23 5y ago
    > Again, this isn't how aquifers work. Are you confusing confined aquifers and unconfined aquifers? That's exactly how unconfined aquifers work. Where I live the wells never go dry because every time it rains they are replenished. Maybe the desert doesn't have unconfined aquifers and that's why you're so strident on this? I really don't know, but I'm curious so please elucidate if you can.

deleted 5y ago

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