How do artesian wells work?

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Offline thedoc

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How do artesian wells work?
« on: 14/07/2015 02:50:01 »
John Gamel asked the Naked Scientists:
   
Here is a question for you: growing up in Alabama, I saw a lot of artesian wells, especially in the north-central part of the state. I know all water follows gravity, but most of these wells are on flat ground with no obvious hills around, so why is that water flowing? Some of those wells have been functioning for decades.

What do you think?
« Last Edit: 14/07/2015 02:50:01 by _system »

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Offline Bass

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Re: How do artesian wells work?
« Reply #1 on: 15/07/2015 05:02:10 »
Artesian wells flow because the groundwater is under enough pressure to bring it to the surface. Easy to imagine if you have an elevated recharge area, an impermeable cap, and some sort of pathway for the water to flow up (pipe or fracture in the rock).
« Last Edit: 15/07/2015 05:05:28 by Bass »
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Offline Colin2B

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Re: How do artesian wells work?
« Reply #2 on: 15/07/2015 11:17:50 »
John Gamel asked the Naked Scientists:
   
.....most of these wells are on flat ground with no obvious hills around, so why is that water flowing?

What do you think?
The hills or higher ground that provide the pressure might not be obvious. For example, London England sits over a chalk basin which provides artesian wells along the Thames. However, the area of chalk is around 160miles across and the chalk surfaces as hills which are to the N & S (Chilterns and North Downs), these are too far away to be obvious to the casual observer.
I'm not familiar with the geology of Alabama and only familiar with the geology of SE England through having walked there. A local geological map should help you to see what is happening.
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Offline evan_au

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