TM 5-818-5/AFM 88-5, Chap 6/NAVFAC P-418
Point at which head is computed, or factor for drawdown in the vicinity of a gravity well
Mean absolute pressure inflow system
Absolute atmospheric pressure
Absolute air pressure at line of vacuum wells
Rate of flow to a fully penetrating drainage slot per unit length of slot, capacity, or rate of pumping, or
rate of surface water runoff
Rate of flow of air
Rated capacity of vacuum pump at atmospheric pressure
Rate of flow to a sand drain
Flow to well in an electroosmotic drainage system
Total surface water pump capacity
Rate of flow to a partially penetrating drainage slot per unit length of slot
Total flow to a wellpoint system
Total flow to a dewatering system
Flow to a well or wellpoint
Flow to an observation well
Flow to well i
Flow to well j
Flow to a partially penetrating artesian well
Rate of flow, or flow per unit length of section flow net
Limiting flow into a filter or well screen
Radius of influence of well, rainfall for assumed storm, or ratio of entrance to throat diameter in meas-
uring flow through a venturi meter
Distance from well to change from artesian to gravity flow
Radius of influence of well i
Radius of influence of well j
Distance from well to point P, or distance from a test well to an observation piezometer
Distance from image well to point P
Distance from well i to point P
Distance from well i to well j
Radius (effective) of a well
Radius (effective) of well j
Coefficient of storage, the volume of water an aquifer will release from (or take into) storage per unit of
surface area per unit change in head. (For artesian aquifers, S is equal to the water forced from stor-
age by compression of a column of the aquifer by the additional load created by lowering the artesian
pressure in the aquifer by pumping or drainage. For gravity flow aquifers, S is equal to the specific
yield of the material being dewatered plus the water forced from the saturated portion of the aquifer
by the increased surcharge caused by lowering the groundwater table.)
Extrapolated S value used in computations for nonequilibrium gravity flow
Distance from point P to image well i
Distance from image well i to well j
Specific yield of aquifer (volume of water that can be drained by gravity from a saturated unit volume of
material)
Height of bottom of well above bottom of aquifer
Duration of rainfall, coefficient of transmissibility in square feet per minute (the coefficient of perme-
ability k multiplied by the aquifer thickness D), or thickness of less pervious strata overlying a more
pervious stratum
Coefficient of transmissibility in gallons per day per foot width
Depth of water in well, or elapsed pumping time
Time for cone of drawdown to reach an impermeable boundary or a source of seepage
Elapsed pumping time since pump started
Elapsed time since pump stopped
Time at zero drawdown or at start of pump test
Argument of W(u), a well function
Volume of water in permeability test, volume of sample in specific yield test, velocity, or vacuum at
pump intake
B-3
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