Groundwater

Larger, coherent accumulations of water in underground cavities are termed groundwater. The groundwater recharge results from precipitation water respectively free water seeping through the more or less permeable soil due to gravity until it is stopped by an impermeable layer. If there is enough hollow space the water accumulates on this impermeable layer (groundwater bottom) and forms a groundwater body, on top defined by the groundwater surface. If the underground cavity is filled the water may discharge e.g. as a spring or it may accumulate in the soil finding its way.