vital to human life and to plant and animal life. The volume of groundwater is much larger
than the volume of water in rivers and lakes, but it lies hidden beneath the land surface
in aquifers. About 90 percent of the earth’s readily available freshwater is stored as
groundwater, slowly percolating through the pore spaces and fractures of rocks near
the earth’s surface. Large regions of the world depend on groundwater for their water
supply, particularly in rural areas, because aquifers are spatially extensive.