GG381 Lecture Notes - Pore Water Pressure, Vadose Zone, Specific Storage
Document Summary
Groundwater is important for a transport mechanism, as well as storage of freshwater. The total storage of groundwater on earth is ~ 8(10)6 km3, which exceeds the capacity of all the world"s rivers and lakes. This ground water is largely confined between grains of sediments, soils, and in small fissures in rock formations. Near the surface these spaces are partly filled with air, which is known as the vadose zone (zone of aeration). Below the vadose zone, where the pore spaces are saturated, lies the water table. The water table can establish at the level at which the pore water pressure in the ground equals the air pressure of overlying air (standard air pressure 101. 325 kpa). The volume of soils that can be occupied by water is known as porosity. If a column of soil 1 metre high has a porosity of p=0. 4, the water itself would be a column 0. 4 m high.