Q: What is Ground Water?
A: Ground water is simply 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 are called aquifers. Aquifers may be small and very localized, or may be very extensive.
Water in aquifers comes from rain and melted snow that filter down through the soil. As the water moves down, plants consume a portion, some is evaporated, and the soil retains a little. The rest seeps down -usually very slowly - to add water to the aquifer.
The amount and quality of ground water varies from place to place in the United States and within any given state, because geology, climate, and land use are different. Even on a local level, wells a few hundred feet apart may give very different water yields and have different water chemistry.