Much of our water supply comes from groundwater, a key natural resource that travels mostly unseen beneath the surface of the Earth. In fact, in New Jersey and throughout the United States, groundwater is the primary source of drinking water for about half of the population. Ground water is essential to our everyday lives. We obtain most of this water from individual domestic wells or public water supplies which tap into aquifers porous rock formations capable of holding and transporting ground water.
Depending on the location, aquifers containing groundwater can either be a few feet below the surface to several hundred feet underground. Under normal conditions, aquifers are replenished naturally by rainfall that soaks into the Earth and seeps down to the water table, the top layer of groundwater. Some groundwater is untouched for years, even centuries, before it is used.
Contrary to popular belief, groundwater is not a flowing underground stream or lake. Groundwater moves at an irregular pace, seeping from less porous to more porous soils, from shallow to deeper areas and from places where it enters the Earth's surface to where it is discharged or withdrawn. Solar energy will evaporate water from surface water bodies, like oceans, streams, lakes and - perhaps most easily seen - puddles. And as clouds accumulate the evaporated water, rain falls to the Earth to restart the hydrologic cycle.