Water leaving an aquifer is called discharge water. Water that is pumped from a well is discharge water. Ground water might also discharge naturally as springs or into swamps, lakes, or rivers. Some wells, called artesian wells , do not need a pump. These wells are drilled into an artesian aquifer which is sandwiched between two impermeable layers.
Water enters an artesian aquifer in a permeable recharge zone which can be miles away from the well.
When a well is drilled into an artesian aquifer, pressure pushes water in the well above the top of the aquifer. If the pressure is high enough, water can flow from an artesian well. We can run out of ground water if more water is discharged than recharged. For example, during periods of dry weather, recharge to the aquifers decreases. If too much ground water is pumped during these times the water table can fall and wells may go dry.