Page 97 - Materials Chemistry, Second Edition

80 Practical Design Calculations for Groundwater and Soil Remediation

3.3 Groundwater Pumping
3.3.1 Steady-State Flow in a Confined Aquifer
Equation (3.10) describes steady-state flow of a confined aquifer (an artesian
aquifer) from a fully penetrating well. A fully penetrating well means that
the groundwater can enter at any level from the top to the bottom of the
aquifer.

Kb h ( 2 − h )
Q = 1 (AmericanPractical Units)
rr /)
528 log( 2 1
2.73 Kb h ( 2 − h )
= 1 (SIUnits) (3.10)
rr /)
log( 2 1
where
Q = pumping rate or well yield (in gpm, or m /day)
3
h , h = static head measured from the aquifer bottom (in ft or m)
1
2
r , r = radial distance from the pumping well (in ft or m)
2
1
b = thickness of the aquifer (in ft or m)
K = hydraulic conductivity of the aquifer (in gpd/ft or m/day)
2
Many assumptions were made to derive this equation. Several references
and other groundwater hydrology books provide more detailed treatment of
this subject [1, 3–5].
Hydraulic conductivity is often determined from aquifer tests (see Section
3.4 for details). Equation (3.10) can be readily modified to estimate the
hydraulic conductivity of a confined aquifer if steady-state drawdown, flow
rate, and aquifer thickness data are available.

r r/)
528 Qlog( 2
K = 1 (AmericanPractical Units)
bh( 2 − h )
1
r r/)
= Qlog( 2 1 (SIUnits) (3.11)
2.73 bh( 2 − h )
1
Another parameter, specific capacity, can also be used to estimate the
hydraulic conductivity of an aquifer. Let us define the specific capacity as

Q
Specific capacity = (3.12)
s w
where
Q = the well discharge rate (extraction rate), in gpm
s = drawdown in the pumping well, in ft
w