Unconfined aquifers occur when permeable materials that allow water to slowly seep through them are at the land's surface. The upper boundary of an unconfined aquifer is the water table. The water table is the interface between the saturated and unsaturated zones. Below the water table, all the pores in the ground are filled with water, while above the water table, some pores are filled with water and some are filled with air.
Confined aquifers are also known as artesian aquifers. Confined aquifers occur when permeable materials that allow water to flow through them are overlain by impermeable materials that do not. This means that the pressure of the water in a confined aquifer is higher than the pressure of the water at the land's surface. This can cause the water in a confined aquifer to rise up to the surface, forming an artesian well.
