5 ms·

> Add to that the fact that almost all of the freshwater consumed by the twenty-two million people of Southern California is imported, much of it pumped long di

by markbnj 11y ago

> Add to that the fact that almost all of the freshwater consumed by the twenty-two million people of Southern California is imported, much of it pumped long distances, over mountains, from Northern California The author's conclusion may very well be correct for all I know, but I think it is somewhat misleading to say that the water is "pumped long distances." There are points where it is pumped, but one of the things that makes the system so fascinating from an engineering standpoint is how much of it relies on gravity, including massive siphons that literally pull the water over mountain ranges.

function_seven 11y ago
> including massive siphons that literally pull the water over mountain ranges. I don't think that is physically possible. Water won't siphon more than 33ish vertical feet. It will just draw a vacuum in the pipe. EDIT: Found a good link. The word "siphon" is quoted on every use in this link, suggesting that they're not actual gravity-powered siphons. See #10. http://www.kcet.org/news/redefine/revisit/commentary/concrete-and-chaparral/a-self-guided-tour-of-the-los-angeles-aqueduct.html http://www.kcet.org/news/redefine/revisit/commentary/concret... EDIT2: Ok, they are gravity-powered, but not by the "pulling" action of the water on the downslope side of the siphon, as much as by the pushing action of the previous downward slope feeding into the siphon. Technically, it's still a siphon i guess, just operating at higher than atmospheric pressure.
- stcredzero 11y ago
  Siphons that are an inverted U have this limit. However, siphons that are a U shape have been in use in aqueducts since Roman times. (There is even an old Scientific American article specifically about them.) Of course, these aren't relevant for getting over mountains, though they are very relevant in mountain ranges for crossing gorges and steep valleys.
  - function_seven 11y ago
    Yeah, I just went on an edit frenzy after you replied. Thanks.
tricolon 11y ago
> massive siphons that literally pull the water over mountain ranges Where's the best place to start reading more about this?
- markbnj 11y ago
  I don't know if I could tell you the best place, but this seems like a good start: https://en.wikipedia.org/wiki/California_State_Water_Project https://en.wikipedia.org/wiki/California_State_Water_Project I became interested while living in LA twenty or so years ago. The whole system represents a monumental engineering achievement, whatever its political, ecological, social, etc., implications. Edit: that page doesn't discuss siphons much, as they are part of the aqueduct components of the system, but reading through it my twenty year-old impressions seem off. Siphons do play a big role in getting water over some heights, but there is a lot of pumping too. On the other hand they generate power from the flow at several places, so who knows how it all balances out?
  - URSpider94 11y ago
    It balances out poorly, and that's the author's point. Quite a bit of energy is wasted in water free-flowing downhill (in the sense that it can not be recovered).
pacificmint 11y ago
You are correct that it's only being pumped in places, but that doesn't really change the fact how much energy we are using to move water. A fifth of energy usage in California is water related, and a fifth of that is for pumping, over 10TWh anually.
- markbnj 11y ago
  Yes, I think the author was correct and I was wrong. However as I mentioned in another reply I don't know what the net is on the power usage.
- mentat 11y ago
  Citation? I find that an incredible figure.
  - pacificmint 11y ago
    Sorry for the late reply. The 19% power figure comes from the PUC. Here are some links: http://www.kqed.org/news/science/climatewatch/waterandpower/waterneedspower.jsp http://www.kqed.org/news/science/climatewatch/waterandpower/... This one goes into more detail and picks that 19% number apart. Also quotes the 10TWh number: http://blogs.kqed.org/climatewatch/2012/06/10/19-percent-californias-great-water-power-wake-up-call/ http://blogs.kqed.org/climatewatch/2012/06/10/19-percent-cal...
    - mentat 11y ago
      Thanks

by markbnj 11y ago

function_seven 11y ago

> including massive siphons that literally pull the water over mountain ranges. I don't think that is physically possible. Water won't siphon more than 33ish vertical feet. It will just draw a vacuum in the pipe. EDIT: Found a good link. The word "siphon" is quoted on every use in this link, suggesting that they're not actual gravity-powered siphons. See #10. http://www.kcet.org/news/redefine/revisit/commentary/concrete-and-chaparral/a-self-guided-tour-of-the-los-angeles-aqueduct.html http://www.kcet.org/news/redefine/revisit/commentary/concret... EDIT2: Ok, they are gravity-powered, but not by the "pulling" action of the water on the downslope side of the siphon, as much as by the pushing action of the previous downward slope feeding into the siphon. Technically, it's still a siphon i guess, just operating at higher than atmospheric pressure.

stcredzero 11y ago
Siphons that are an inverted U have this limit. However, siphons that are a U shape have been in use in aqueducts since Roman times. (There is even an old Scientific American article specifically about them.) Of course, these aren't relevant for getting over mountains, though they are very relevant in mountain ranges for crossing gorges and steep valleys.
- function_seven 11y ago
  Yeah, I just went on an edit frenzy after you replied. Thanks.

tricolon 11y ago

> massive siphons that literally pull the water over mountain ranges Where's the best place to start reading more about this?

markbnj 11y ago
I don't know if I could tell you the best place, but this seems like a good start: https://en.wikipedia.org/wiki/California_State_Water_Project https://en.wikipedia.org/wiki/California_State_Water_Project I became interested while living in LA twenty or so years ago. The whole system represents a monumental engineering achievement, whatever its political, ecological, social, etc., implications. Edit: that page doesn't discuss siphons much, as they are part of the aqueduct components of the system, but reading through it my twenty year-old impressions seem off. Siphons do play a big role in getting water over some heights, but there is a lot of pumping too. On the other hand they generate power from the flow at several places, so who knows how it all balances out?
- URSpider94 11y ago
  It balances out poorly, and that's the author's point. Quite a bit of energy is wasted in water free-flowing downhill (in the sense that it can not be recovered).

pacificmint 11y ago

You are correct that it's only being pumped in places, but that doesn't really change the fact how much energy we are using to move water. A fifth of energy usage in California is water related, and a fifth of that is for pumping, over 10TWh anually.

markbnj 11y ago
Yes, I think the author was correct and I was wrong. However as I mentioned in another reply I don't know what the net is on the power usage.
mentat 11y ago
Citation? I find that an incredible figure.
- pacificmint 11y ago
  Sorry for the late reply. The 19% power figure comes from the PUC. Here are some links: http://www.kqed.org/news/science/climatewatch/waterandpower/waterneedspower.jsp http://www.kqed.org/news/science/climatewatch/waterandpower/... This one goes into more detail and picks that 19% number apart. Also quotes the 10TWh number: http://blogs.kqed.org/climatewatch/2012/06/10/19-percent-californias-great-water-power-wake-up-call/ http://blogs.kqed.org/climatewatch/2012/06/10/19-percent-cal...
  - mentat 11y ago
    Thanks