AQUIFERS

Water infiltrates and percolates downward through soil and/or rock formations eventually reaching a saturated area. If the saturated area can supply a reasonable amount of groundwater to water supply wells the saturated area is defined as an aquifer.

• There can be more than one aquifer below the surface in any location.
• The top of the saturated area in an aquifer is known as the water table or the static water level of a well.
• There are two types of aquifers:
  • An unconfined aquifer is one that is located in a permeable formation (e.g., sand or gravel) where the water table is free to rise and fall depending on factors such as the amount of rainfall.
  • A confined aquifer is situated below an impermeable layer such as rock or clay. If these impermeable layers are higher than the surrounding water table in another aquifer, they are defined as perched aquifers.

Aquifers exist in two types of geologic formations:

• Unconsolidated formations are made up of sand and/or gravel.
• Consolidated formations are rock formations such as sandstone, dolomite, or limestone.