What are the two types of aquifers?

• A. Confined and Unconfined
• B. Shallow and Deep
• C. Perched and Artesian
• D. Primary and Secondary

Answer: (A)

Groundwater storage is classified by whether there is an impermeable boundary above the aquifer. In a confined aquifer, water is trapped between impermeable layers, so it is pressurized and can rise in a well without pumping (an artesian condition). In an unconfined aquifer, the upper surface is the water table and directly interfaces with the atmosphere, with recharge from the surface and pumping drawing down the water table.

Shallow vs deep describes how far the aquifer lies from the surface, not the fundamental type. A perched aquifer is a localized body of water above the main water table, not a general category of aquifers. Artesian refers to the pressure condition within a confined aquifer, not a separate type. Primary and secondary relate to porosity concepts, not the main way aquifers are classified.