However, if the ground material is impermeable, such as clay, shale, or igneous and metamorphic rock without fractures and little interconnected porosity, then instead of having an aquifer you have either an aquiclude or an aquitard. Aquicludes are also confined, which indicates that the water within is not able to flow freely and is placed under great pressure. When an overpressured confined aquifer is tapped into the water will rise above the level of the aquifer almost like a fountain, this is called an artesian well. On the other hand, aquifers are unconfined. Groundwater recharge is the process of adding water through human-induced or natural infiltration.
Water is filtrated in the ground during rain and flooding.
Wells and natural springs are a form of groundwater discharge, which simply is the return of water to the surface. Water leaves an aquifer by the pressure within and its surroundings, as well as, the water table above, which allows the water to move freely within the aquifer for use. The process of adding water to the ground and taking it away is an example of the water cycle. This continuous cycle replenishes the groundwater. In groundwater flow the precipitation infiltrates the surface.