Definition

1. Adjective: (of groundwater or a well) Describing a condition where water rises under its own pressure to a level significantly above the local water table but does not reach the ground surface to flow freely. It is an intermediate state between a non-flowing (water-table) well and a freely flowing artesian well.

Usage

The term subartesian is a technical adjective used almost exclusively in geology, hydrology, and well drilling. It describes the specific hydraulic condition of a water-bearing aquifer and the wells that tap into it. * It modifies nouns like well, condition, aquifer, pressure, or water. * A subartesian well requires a pump to bring water to the surface, unlike an artesian well which flows spontaneously.

Examples

• Adjective:
  • The drilling company discovered a subartesian aquifer that could supply the town's needs if pumped.
  • We hit a subartesian zone at 150 feet; the water rose 30 meters in the casing but did not overflow.
  • The subartesian condition indicates the aquifer is under sufficient pressure to lift the water column but not enough to cause a surface flow.

Advanced Usage

• The term is used in contrast to artesian (freely flowing) and water-table (non-pressurized) conditions. It describes a confined aquifer where the potentiometric surface (the level water would rise to in a well) is above the top of the aquifer but below the ground surface.

Variants and Related Words

• Artesian (adj): Describing a well or aquifer where water pressure is sufficient to cause the water to rise above the ground surface without pumping.
• Potentiometric surface (n): An imaginary surface representing the level to which water will rise in a tightly cased well tapping a confined aquifer.
• Confined aquifer (n): An aquifer bounded above and below by impermeable layers (aquitards), which can create artesian or subartesian pressure.

Synonyms

• Non-flowing artesian: A more descriptive technical synonym.
• Semi-artesian: An occasionally used, less formal synonym.

Antonyms

• Artesian (in the context of a flowing well).
• Water-table (describing an unconfined, non-pressurized aquifer).

Adjective

1. (of water) rising naturally in a well to a height appreciably above that of the surrounding water table but not flowing out of the well