Class Note 12 Groundwater Vasey's Paradise in the Grand Canyon. A stream is issuing from a small cavern in the Redwall Limestone near river level. Groundwater is liquid water that lies in the subsurface in fractures in rocks and in pore space between grains in sedimentary rocks.
Porosity is the percentage of open space in a rock.
Permeability is the ability of fluids to flow through rock. It depends on the connectivity of the pore space. Permeable rocks include sandstone and fractured igneous and metamorphic rocks and karst limestone. Impermeable rocks include shales and unfractured igneous and metamorphic rocks. The water table is the natural level of liquid ground water in an open fracture or well.