What is the natural flow of groundwater from the earth's surface called?

The natural flow of groundwater from the earth's surface is referred to as a spring. A spring occurs when groundwater flows to the surface naturally, typically due to pressure changes or geological formations that allow water to escape from an aquifer.

In this context, an aquifer is a geological formation that can store and transmit water, but it does not denote the actual spring phenomenon. An artesian well is a specific type of well that taps into an aquifer under pressure, leading to the water rising on its own without the need for pumping; however, it is not a natural flow from the surface like a spring. The water table represents the upper surface of the saturation zone, below which all the spaces are filled with water, but it does not describe the outgoing flow of water. Therefore, the term best describing the natural outflow of groundwater at the surface is indeed a spring.