Unsaturated Zone 3 : The zone immediately below the land surface where the pores contain both water and air, but are not totally saturated with water. These zones differ from an aquifer, where the pores are saturated with water
US Department of the Interior, US Geological Survey USGS, Water Science Glossary of Terms, http://ga.water.usgs.gov/edu/dictionary.html (Some of this information is courtesy of the Nevada Division of Water Resources - the detailed water glossary at VA, USA 2009. http://water.nv.gov/programs/planning/dictionary/) , (ND/ Flood - Amer) {491}