Homework Assignment 6—Darcy’s Law, Aquifer Characterization
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