Confined Aquifer

An aquifer is a layer of soft rock, like limestone or sandstone, that absorbs water from an inlet path. Porous stone is confined between impermeable rocks or clay. This keeps the pressure high, so when the water finds an outlet,it overcomes gravity and goes up instead of down without the need for pumping. In this case is the presence of an artesian well.
The Great Artesian Basin is the largest and deepest artesian basin in the world, occupying 23% of the Australian continent.

Great Artesian Basin