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CT: Seepage faces occur commonly in unconfined groundwater flows. Accurate estimation of the seepage face height is important in both steady-state and transient problems. Earlier modeling studies of water flow dynamics neglected the unsaturated zone but accounted for its contribution to the saturated zone (i.e., zone below the water table) using the specific yield concept. More recent studies use the more realistic variably-saturated representation of water flow, which is based on Richard’s equation. Such a representation removes the artificial treatment of the water table as a sharp interface between the saturated zone and the unsaturated zone; the water table is merely the locus of points where the gauge pressure of the water is zero. Variably-saturated numerical models have since been used to investigate seepage problems under steady state and transient regimes.

S: NJIT – http://centers.njit.edu/nrdp/areas/seepage.php (last access: 2 December 2014)

N: 1. seepage (n): 1825, from seep (1790, variant of sipe (c.1500), possibly from Old English sipian “to seep,”) + -age (word-forming element in nouns of act, process, function, condition, from Old French and French -age, from Late Latin -aticum “belonging to, related to,” originally neuter adjectival suffix, from Latin -atus, pp. suffix of verbs of the first conjugation).
face (n): c.1300, “the human face, a face; facial appearance or expression; likeness, image,” from Old French face “face, countenance, look, appearance” (12c.), from Vulgar Latin facia (source also of Italian faccia), from Latin facies “appearance, form, figure,” and secondarily “visage, countenance,” which probably is literally “form imposed on something” and related to facere “to make”
2. When pumping occurs from a well in an unconfined aquifer, a seepage face develops between the elevation where the water table intercepts the well face and the water level in the well. The existence of a seepage face often leads to well yields which are less than values determined by conventional analysis.
3. Section of the soil surface, at a level below the phreatic surface, through which water seeps out of saturated soil into the air at atmospheric pressure.

S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=seepage&searchmode=none; http://www.etymonline.com/index.php?allowed_in_frame=0&search=face&searchmode=none (last access: 2 December 2014). 2. TERMIUM PLUS (last access: 2 December 2014). 3. GDT (last access: 2 December 2014).

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CR: aquifer, capillary zone, geothermal energy, geothermics.