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I would like to attempt to build a well-type structure in a woodland area. This woodland is mainly inhabited with Silver Birch and Sycamores and there is a shallow stream running down off of a moorland around 80ft from where the well would be ideally placed, but this can move.

My thoughts are that due to the prevalence of water there is likely to be a body of water underneath the ground simply through the natural process of infiltration.

So my questions are the following:

1) Am I likely to come across water if I dug this well?

2) How deep will I have to dig before I reach water or impermeable ground?

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    $\begingroup$ Geological & hydrological conditions vary greatly all over the world. There is no standard depth, from the surface of the Earth to the top of a water table. $\endgroup$ – Fred Jul 21 '18 at 9:31
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    $\begingroup$ Yeah this will be totally dependent on the local geology, You can drill wells very close together and have one normal and one completely dry with the right strata. $\endgroup$ – John Jul 22 '18 at 6:27
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I live in Colorado, USA. All gas stations must have shallow wells drilled around the gasoline tanks to monitor for gasoline tank rupture leaks. The tanks usually lie above the water table so any gas leaks will travel to the water table and start flowing on top of the groundwater. One hundred percent contamination happens when a flashlight is shined down the well and a gasoline sheen is seen on the water. Less contamination is measured by sampling the water. The depth to the water table is also measured.

The point I am getting to, is that all gas stations in Colorado have to be measured every three months and the results sent to the State. I would suggest that you check for a gas station near where you live and get a recent published water report that you can study. One of the maps is a water table depth map. The map will have a contour map with the depth below surface contours and arrows perpendicular to contour lines that show the direction of groundwater flow.

I would suggest for you to see if your State or Provence has a similar contamination monitoring program. This would give you an idea how the water table behaves in your area. If you go to your nearest gas station and look for circular steel plates about 6 inches in diameter placed flush on the ground around the tanks, gas pumps, and parking lot, then you will know if the station is monitored. The top of the plate has a filled in triangle with the triangle points touching the circle circumference. Sometimes the plate has a warning that says "DO NOT FILL". The the steel plate and map symbol looks like Unicode symbol U1F7D5.

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Without seeing the details of the topography, you are correct in your assumption that water will infiltrate down past the tree root-zone to the water table. The shallow groundwater will likely form a local flow system, discharging to the stream, although some may form a deeper system that forms a regional aquifer.

If the groundwater is discharging to the stream you may be looking at relatively shallow depth to water when you are in the valley that close. It depends a lot on the amount of rainfall that recharges the groundwater and the topography, as well as the soil and rock type. It is impossible to say from the information you have given on what the depth to bedrock will be.

That being said, these shallow flow systems can have poor quality water and can even be affected by contaminants from the stream (e.g. when it floods).

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