If discharge occurs through a well, that well is a flowing artesian well. When the withdrawal of groundwater in an aquifer exceeds the recharge rate over a period of time, the aquifer is considered to have overwithdrawal. There are two possible effects from the overwithdrawal of water from an aquifer. First, when the amount of fresh water being pumped out of an aquifer in a coastal area can not be replaced as fast as it is being withdrawn, saltwater migrates towards the point of withdrawal. This movement of saltwater into zones previously occupied by fresh water is called saltwater intrusion.
Saltwater intrusion can also occur in inland areas where briney water underlies fresh water.
Secondly, in some areas, overwithdrawal can make the ground sink because groundwater pressure helps to support the weight of the land. This is called subsidence. Sinkholes are an example of this effect.