Question

a) A well is pumped at an equilibrium flow of 454 gpm to determine a confined aquifer permeability. The thickness of the aquifer is 100 ft and the drawdown in observation wells is noted as 3 ft and 9 ft at 100 ft and 10 ft respectively, from the pumped well, What is the permeability¿

b) Using the same data as a) exceptmconsider an unconfined aquifer that was totally saturated before pumping, what is an estimate of permeability¿

Answer 1

A. Confined aquifer

where:

K= permeability (ft/s)

Q = well discharge rate (ft3/s)
D = thickness of aquifer (ft)
r₁, r₂ = respective distances of the piezometers from the well (ft)
s₁, s₂ = drawdowns in the piezometers (ft)

Q = 454 gpm =1.0115 ft^3/s

r1=10 ft and s1=9 ft

r2=100 ft .S2= 3 ft

1.0115 = [2* pi* K* (10 - 3)] / ln (100/10)

K = 0.0053 ft/s

(B) for unconfiend aquifer

h1= D- s1= 100 - 10 =90 ft

H2 = D- S2= 100 - 3 = 97 ft

1.0115 = [ pi * K ( - )] / ln (10/100)

K = 0.000566 ft /s