RE: Definition of perched water. Water that is perched above an impermeable layer, or one of very low permeability, overlying one that is permeable. In other words, without the impermeable layer, the water would not be there.
http://www.eng-tips.com/viewthread.cfm?qid=315718
If there is no phreatic surface in the clay, then you have a perched water table above the clay and zero pressure head in the clay (i.e., only elevation head). If all there is is elevaton head, then that defines a vertical gradient of unity.
http://www.eng-tips.com/viewthread.cfm?qid=315718
Quick Answer. A perched water table is an accumulation of groundwater located above a water table in an unsaturated zone. The groundwater is usually trapped above a soil layer that is impermeable and forms a lens of saturated material in the unsaturated zone. Continue Reading.
https://www.reference.com/science/perched-water-table-e2c85cae1fec4d9c
Perched facet joint. Dr Craig Hacking ◉ and Dr Charudutt Jayant Sambhaji et al. Perched facet joint is a vertebral facet joint whose inferior articular process appears to sit 'perched' on the ipsilateral superior articular process of the vertebra below.
https://radiopaedia.org/articles/perched-facet-joint
a pole or rod, usually horizontal, serving as a roost for birds. 2. any place or object, as a sill, fence, branch, or twig, for a bird, animal, or person to alight or rest upon. 3. a high or elevated position, resting place, or the like. 4. a small, elevated seat for the driver of any of certain vehicles.
http://www.dictionary.com/browse/perch
Aquifers that contain perched groundwater i.e. bodies of groundwater separated from an underlying body of groundwater by an unsaturated zone. A perched aquifer occurs above the regional water table and is generally a relatively small body of water with an impermeable base under which lies an unsaturated zone.
https://www.dwaf.gov.za/Groundwater/Groundwater_Dictionary/introduction_perched_auifers.htm
Cross section showing the water table varying with surface topography as well as a perched water table. The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. The water table is the surface where the water pressure head is equal to the atmospheric pressure (where gauge pressure = 0). It may be visualized as the surface of the subsurface materials that are saturated with groundwater in a given vicinity.
https://en.wikipedia.org/wiki/Water_table
RE: Definition of perched water. Here's a simple explanation. Sometimes there's a clay layer or some rock or some sort of barrier between the surface and way down where the groundwater is. So when it rains, the water leaks down and pools on top of that barrier, instead of making it down to the groundwater, making a falsely high layer of groundwater.
http://www.eng-tips.com/viewthread.cfm?qid=315718
A perch is a temporary resting place. In the middle of climbing a tree, you might find a good perch on a high branch. Bet some birds will be perching there too. Perch has many different meanings. A bird perch is a little stick it can balance on, and the armrest of the couch can offer you a perch during a party. It's also the name of a kind of fish with spiny fins. And it's also an old measurement of 16.5 feet.
https://www.vocabulary.com/dictionary/perch
6. (Textiles) a frame on which cloth is placed for inspection. 7. (Units) obsolete or dialect a pole. vb. 8. (usually foll by on) to alight, rest, or cause to rest on or as if on a perch: the bird perched on the branch; the cap was perched on his head. perch. perch1. n. 1. a pole or rod, serving as a roost for birds. 2. any place or object for a bird, animal, or person to alight or rest upon. 3. a high or elevated position, resting place, or the like. 4. a small, elevated seat for the driver of any of certain vehicles.
http://www.thefreedictionary.com/perch
what is perched
Perched is a pole or rod, serving as a roost for birds. Perched is a pole or rod and serving as a roost for birds.