A well is an opening in the earth which may be drilled or dug to reach water which collects underground. This collection of water is called the water table. The water may exist in basins formed of clay or various types of rock, or it may be a running stream deep in the earth. After an opening has been drilled, a pipe is lowered to reach the water. A pump is then installed at the surface to supply the power to lift the water up through the pipe. A PUMP may be operated by hand or by some other mechanical means.
When the underground water seeps into a basin-like reservoir where hard rock layers press upon it, the water will escape or forcibly flow when the underground reservoir is tapped. This is called hydrostatic pressure and no other power is needed to bring the water to the surface. This is an artesian well.
The name "artesian" comes from the Artois region in northern France where natural artesian wells were observed in Roman times. Today the term "artesian well" is generally applied to a well that has been drilled into any underground basin of water that is under pressure from the enclosing rock.
The water from an artesian well is likely to be pure because it has been filtered through sand and semiporous rocks. Such a well may tap a source of water in a region which is otherwise very dry, such as the Sahara Desert or the interior of Australia. In these places, artesian wells make crop irrigation possible.
Because some artesian wells go down as far as five thousand feet, their water temperature gives scientists a clue to the interior heat of the earth.
