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.  nSILT=0.40, nAQUIF=0.40, γDRY SILT=16000 N/m3, γWATER=9810 N/m3, initial hp=46 m, final hp=0 m, αAQUIF=10-7 m2/N, ß=4.4X10-10 m2/N

a.   What is the total stress acting on top of the aquifer?  The initial effective stress?  Answer in N/m2.

                  ans: σT = 4.38 x 106 N/m2         σE = 3.93 x 106 N/m2    

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 104 m3

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