What is the difference between an aquifer, groundwater and surface water?
Surface water is the water trapped above ground in marshes, lakes, streams, rivers, etc. Groundwater is surface water that saturates the tiny spaces between alluvial material (silt, sand, gravel, clay) or the crevices or fractures in rocks. It is water that is found below the surface of the zone of saturation (see definition of Water Table) that is under pressure equal to or greater than atmospheric pressure. An aquifer is the water found in underground layers of porous rock that are saturated from above or from structures sloping toward it. The most common kind of aquifer is an unconfined one where the water percolates into it through the land surface. A confined aquifer occurs when the underground system is between layers of dense clay or rock with low permeability. This water is usually very old in geologic terms. It is also usually under more pressure than unconfined aquifers. When tapped by a well, this water is forced up, often creating a flowing artesian well.
