Science Questions

How do you find water underground?

Sun, 15th Jun 2008

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Question

Yaldas asked:

How do you find water underground?

Answer

We asked our guest Richard Davies

All rocks, all sedimentary rocks contain water. What we’re really looking for is rocks that have porosity and permeability. So you can look at outcrops to find out which are the right suitable rock types and you can drill holes and hopefully intersect those rock types. All sediments contain water and it’s actually when they’re buried that you’re actually squeezing the water out very slowly. It’s really a matter of looking for the suitable rock types. For example, chalk beneath London is a suitable aquifer. It has been historically, anyway.

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yeldas asked the Naked Scientists: hi This is Yeldas. I am very much interested in how you find underground water? What do you think? yeldas, Thu, 8th May 2008

Hi Yeldas

Hydrology is the branch of geology devoted to water and water cycles.  JimBob has much more experience, but I'll give it a go:

Underground water (ground water) is formed when rainfall percolates into the ground.  The water moves downward from the surface through an unsaturated zone (voids are not completely filled with water) until it finally reaches the saturated zone.  The boundary between the unsaturated and saturated zones is called the water table.

The water continues to move downward and laterally along favorable geologic horizons called aquifers.  Aquifers must be both porous (have pore space) and permeable (the pore spaces must be connected).  Aquifers can be either open to the surface, or they can be confined (capped by impermeable rocks).

As you can guess, your question "how do you find ground water" is not always simple.  In areas covered with young gravels (such as river and stream valleys), finding ground water is often as simple as drilling a hole deep enough to hit the water table.  In other areas, knowledge of the local geology and aquifers, and the services of a hydrologist, are indispensable.  Subsurface hydrology and geology can be determined from nearby outcrops, wells, and geophysical methods.

Of course, there are people that claim to be able to find water using branches or metal rods, called water dowsers.  I've known dowsers that are able to predict water very well, and those who are complete frauds.  I don't know that anyone really knows the science behind dowsing (there's a prior thread on dowsing somewhere in TNS). Bass, Thu, 8th May 2008

Actually, for a hard rocker, ( it is my taste in music, not geology) you did quite well. I see nothing that needs to be added.

Let me guess - you have been at one time or another, dealing with subsurface water entering your mines.


JimBob, Fri, 9th May 2008

More like tracing indicator elements in groundwater to try to find deposits. Bass, Fri, 9th May 2008

OK, much more sophisticated stuff than I realized. Bravo - you know what a sand is !!! JimBob, Sat, 10th May 2008

Hang On !!

The answer is simple....send a probe across millions of miles to Mars and find out !!

QED neilep, Wed, 18th Jun 2008

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