An artesian well allows water to rise to the surface that has
traveled through porous rock from a higher elevation. This pumpless
well seems to defy gravity because the pressure that builds up
between layers of rock gets relieved when the water finds a path to
the open air. For nearly a thousand years, people have drilled
wells to drink such cold, filtered water that doesn't need to be
hauled up from the depths. An aquifer provides the water source for
an artesian well. An aquifer is the layer of permeable rock, like
limestone or sandstone, that absorbs water from an inlet path at
high elevation such as the top of a mountain. The water source
might be fed by snowmelt or precipitation. Porous stone is
sandwiched between a top and bottom layer of an impermeable
substance like clay soil or shale rock. This keeps the water
pressure high, so that when you get to a point below the entryway
of the flow, there is enough pressure to bring the water up.
Natural springs form in the same way when a gap in the impermeable
rock, maybe triggered by an earthquake, allows the water to rise to
the surface. Entire cities have relied on giant underground
aquifers to provide fresh, cold water when there are no
above-ground rivers. In 1126, monks used a rod with a sharp end,
called a bore, to penetrate a layer of impermeable rock. Their
percussive drilling, just hammering on the end of the bore, broke
through with sheer human force. The water that rose had percolated
through the pores of the rock, so that many contaminants have been
filtered out, and it proved safer to drink than standing or river
water. Nowadays, if a town or residency needs water closer to the
top of a mountain, they might lie above the line where there is
enough pressure to push the water all the way to the surface. In
this case, the aquifer can be accessed by drilling a relatively
shallow well and then pumping the water up to ground level. Our
well-drilling has progressed from hammers and bores, to machinery
that twists a giant drill into the ground. Sometimes, if the
pressure is especially strong, because the well is lower in
elevation, the water might thrust up like a fountain, and form a
geyser. This particular artesian spring is less dramatic than a
geyser, but it still provides a steady source of fresh, clear
water.
In order to log this cache, please complete
the following tasks:
1. Take a picture of the water outflow location with yourself or
your GPSr in the picture, and
2. Measure the water flow in units per minute. For example, record
the time it takes to fill a litre, gallon, quart or whatever size
container you have, and convert that result to give a "gallons per
minute" waterflow.
They say drinking from the
well has driven some locals mad....