Geohydrological unit (A) (history)

Indication of hydrological units associated with the evaluation of the groundwater measurement network (A = Freatic package). Phreatic groundwater is groundwater that stands on top of a first poorly permeable soil layer (e.g. clay), in relatively good permeable soil. The first groundwater that one encounters when digging is freatic. However, in sandy soils with clay and loam lenses, there may be a water level above the phreatic groundwater.