|Groundwater is water
underground in saturated zones beneath the land surface.
It fills the pores and fractures in underground materials such as
sand, gravel, and other rock.
If groundwater flows from rock materials or can be removed by pumping
from the saturated rock materials in useful amounts, the rock materials
are called aquifers. Groundwater moves slowly in an aquifer.
As a result, water could remain in an aquifer for hundreds or thousands
Groundwater is the source of about 40% of water used for public
supplies and about 38% of water used for agriculture in the United