Aquifers
Aquifers
~ Any underground layer of rock or sediment that
holds water.
~ They can range in size from a small underground
patch of permeable material to an area the size of
several states.
Aquifers
Ogallala Aquifer
~ Lies beneath the plains of the Midwest, stretching from South
Dakota to Texas.
~ Millions of people obtain their drinking water from this
underground storehouse.
~ Provides water for crops and livestock.
https://www.youtube.com/watch?v=XXFsS94HF08
Ogallala Aquifer
~ Groundwater is actually in motion, seeping through the layers of rock.
~ How fast it moves depends largely on how steeply the aquifers slopes and
how permeable the rocks are.
~ Groundwater in some aquifers moves only a few centimeters a day.
~ At that rate, the water moves about 10 meters a year- less than the length
of a typical classroom.
~ May travel hundreds of km and stay in an aquifer for thousands of years
before coming to the surface again.
Groundwater to the surface
In places where the water table meets the ground
surface, groundwater seeps onto the surface. The
groundwater may feed a stream or pond, or form a
wetland. People can also bring groundwater to the
surface.
WELLS
~ People can obtain groundwater
from an aquifer by drilling a well
below the water table.
~ Because the bottom of the well
is in the saturated zone, the well
contains water.
~ Long ago people dug wells by
hand. They lined the sides of the
well with brick or stone to keep
the walls from collapsing.
~ To bring up water, they lowered
and raised a bucket.
~ Today wells are dug with welldrilling equipment.
~ Pumps bring up the
groundwater.
~ Pumping water out of an
aquifer lowers the water
level near the well.
~ If too much water is
pumped out too fast, the
well may run dry.
~ It will be necessary either
to dig deeper to reach the
lowered water table, or to
wait for rainfall to wait for
rainfall to refill the aquifer.
~ New water that enters
the aquifer from the
surface is called recharge.
ARTESIAN WELL:
~ Groundwater is trapped
between two layers of
impermeable rock or
sediment.
~ The water is under great
pressure from the weight of
the water above it.
~ If the top layer of rock is
punctured, the pressure sends
water spurting up through the
hole.
~ Water flows without
pumping from a well dug in
such an aquifer.
https://www.youtube.com/wa
tch?v=KMtEQqbi4CI
Slide 9
SPRINGS:
Places where groundwater bubbles or flows out
of cracks in the rock are called springs.
Most springs contain water at normal
temperatures, but some springs, like those in
Yellowstone, contain water that is warmed by
the hot rocks deep below the surface.
The heated water bubbles to the surface in hot
springs