Homework
Assignment 6—Darcy’s Law, Aquifer Characterization

From
Fetter:

Chapter
3: 9, 11, 15

Chapter
4: 9, 11

1. A horizontal aquifer is 60 m thick and
overlain by 220 m of saturated silt. n_{SILT}=0.40,
n_{AQUIF}=0.40, γ_{DRY}_{
SILT}=16000 N/m^{3}, γ_{WATER}=9810
N/m^{3}, initial h_{p}=46 m, final h_{p}=0 m, α_{AQUIF}=10^{-7} m^{2}/N,
ß=4.4X10^{-10} m^{2}/N

a. What is the total stress acting on top of the
aquifer? The initial
effective stress? Answer in N/m^{2}.

ans: σ_{T}_{
}= 4.38 x 10^{6} N/m^{2} σ_{E}_{
}= 3.93 x 10^{6} N/m^{2}

b. How much water was pumped to account for the
46 m decline in head? Figure your answer
for a aquifer surface area of 100 m x 100 m.

ans: Vw = 2.71 x 10^{4}
m^{3}

c. What is the storativity
of the aquifer?

ans: S = 5.90 x
10^{-2}

d. What is the change in aquifer thickness
caused by the drop in head?

ans: db =
-2.71 m