What Is Ground Water?

Ground water is water below the land surface that fills the spaces between grains of sediment and rocks, or fills cracks and fractures in the rock. Saturated zones in sediment such as sand and gravel, and in fractured rock formations, that receive, store, and transmit water to wells and springs are called aquifers.

Clean and plentiful ground water is a vital resource for personal and economic health everywhere in the United States. Each day, over 130 million Americans get their drinking water from ground water. About 40 million are supplied from individual home wells.


The Hydrologic Cycle

Water in aquifers comes from rain and melted snow that filters through the soil. As the water moves down, plants consume a portion, some is evaporated, and some is retained by the soil. The rest seeps downwards, usually very slowly, to add water to the aquifer. This process is part of the hydrologic cycle. The amount and quality of ground water varies from place to place both within individual states and from state to state, because geology, climate, and land use are different.

• natural factors, such as the type of rock, gravel, sand or soil
• or by pollution, for example, from poorly managed agriculture, individual septic systems or community waste disposal sites.

Public education about contamination, and community involvement in protecting aquifers, can help ensure safe drinking water throughout the United States.


Potential Threats to Ground Water

Most well water is good quality because of the filtering process in the soil and the long travel time underground between the water occurring as rain and eventually reaching a well. However, in addition to possible pollution from agriculture, industry and transportation, even contamination sources in our homes can pose threats to ground water.

Incorrect disposal of common household chemicals (polish, thinners, paints, etc.,) excess use of lawn and garden chemicals, faulty or overloaded septic tanks, or an accidental spill during an automobile driveway oil change, can wreak havoc with drinking water safety. The more informed that residents are, the better are the prospects for protecting ground water.

*This information section has been provided courtesy of the American Ground Water Trust. This information is copyrighted and reproduction or distribution is prohibited without the express consent of the American Ground Water Trust.