What defines a confined aquifer?

A confined aquifer is defined as a saturated formation situated between layers of low permeability, often referred to as aquitards or aquicludes. This setup creates a situation where the pressure in the confined aquifer increases, as the water is trapped under the impermeable layers. Because of this confinement, water in a confined aquifer can be under greater pressure than the water in an unconfined aquifer, which is exposed to atmospheric pressure and surface conditions. Understanding this characteristic is crucial for the management and extraction of groundwater resources, as it affects both the movement of water and the potential for contamination. The other options describe different aspects of groundwater systems or conditions that do not apply specifically to confined aquifers, which is why they are not accurate definitions.