Water table aquifers
Water table aquifers are the saturated portions of the upper soil profile located above a confining layer. The saturated soil must be of such composition (e.g., sand and/or gravel) that the water can be easily withdrawn. (A saturated, clayey soil does not meet the definition of an aquifer.)
Confining layers may be represented by bedrock layers or clay-rich soil layers. These layers severely impede downward movement (percolation) of infiltrated water. As a result, snowmelt or rainfall that enters the soil (infiltrates) accumulates in the soil above the confining layer causing a saturated soil condition. The water surface at the top of the saturated zone is called "the water table."