Figure 13.23: Green Dragon Spring is a hot spring found at Yellowstone National Park. ( 4 )
groundwater. When the water table is close to the surface, wells can be a very convenient
method for extracting water. You may have made a very simple well by digging a hole in
the sand at the beach until you see a pool of water at the bottom. When the water table
is far below the surface, digging wells can be quite a challenge. Most wells use motorized
pumps to bring water to the surface, but many wells still require people to use a bucket to
draw water up.
Wells have been an important source of water for humans through the ages. Obviously, in
places that have little precipitation, wells are vital to life. Using groundwater at a faster rate
than it can be replenished by the water cycle, will cause the water table in an aquifer to fall.
A well using that groundwater might therefore go dry, as the water that supplies the well
gets used up. It is important to use water at a rate at which it can be naturally replenished.
In addition, humans must be careful not to pollute groundwater, since pollution can make
water supplies unusable by humans.
Lesson Summary
- Groundwater, water that infiltrates the ground, forms our largest source of readily
available freshwater. - The water table forms the top of the zone of saturation, where pore spaces in sediment
or rock are completely filled with water. - Aquifers are underground areas of sediment or rock that hold groundwater.
- In steep areas, where groundwater intersects the ground surface, a spring or seep can
form. - If groundwater is heated by magma, it can form hot springs and geysers.
- In order to access groundwater supplies, humans drill wells and pump water from the