Enable javascript in your browser's settings to view menus on this site.
General
Aquiclude A water-bearing layer of rock or sediment that is incapable of
transmitting water.
Aquifer A water-bearing layer of rock or sediment capable of transmitting
significant quantities of water.
Aquitard A water-bearing layer of rock or sediment that transmits small quantities
of water in relation to aquifers .
Artesian Aquifer A confined aquifer in which the water
level in wells rises above the top of the aquifer .
Confined Aquifer An aquifer whose upper and lower boundaries are
defined by aquicludes .
Drawdown Change in water level due to an external stress such as pumping.
Leaky Confined Aquifer A confined aquifer whose upper and/or
lower boundaries are defined by aquitards .
Unconfined Aquifer An aquifer in which the
water table forms the upper boundary.
Water Table The surface in a porous medium on which fluid pressure is equal to
atmospheric pressure.
Water-Table Aquifer See unconfined aquifer .
Hydraulic Properties
Aquifer Diffusivity (α)The ratio of transmissivity to
storativity , α=T/S. [L2 /T]
Hydraulic Conductivity (K)Constant of proportionality defining the specific discharge of a porous medium under a
unit hydraulic gradient , q=K*i. [L/T]
Hydraulic Gradient (i)Hydraulic head loss per distance, i=dh/dl. [dimensionless]
Porosity (n)Ratio of void volume (Vv ) to total volume (VT ) in a
rock or unconsolidated material, n=Vv /VT . [dimensionless]
Specific Discharge (q)Flow rate per unit cross-sectional area of aquifer , q=Q/A. Also known as Darcy
velocity or Darcy flux given by the product of
hydraulic conductivity and
hydraulic
gradient , q=K*i. [L/T]
Specific Storage (Ss )Volume of water released from storage from a unit volume of
aquifer per unit decline in hydraulic head. [1/L]
Specific Yield (Sy )Volume of water released from storage by an unconfined aquifer per unit surface
area
of aquifer per unit decline of the
water table . [dimensionless]
Storativity (S)Volume of water released from storage by a confined aquifer per unit surface area of
aquifer per unit decline in hydraulic head normal to surface, S=Ss b.
[dimensionless]
Transmissivity (T)The product of hydraulic conductivity and saturated thickness, T=K*b. [L2 /T]
Well Construction Details
Full Penetration A fully penetrating well has a perforated interval or screen extending over the full
saturated thickness of an aquifer .
Partial Penetration A partially penetrating well has a perforated interval or screen extending over a
portion of the saturated thickness of an aquifer .
