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/m³, γ_WATER=9810 N/m³, initial h_p=46 m, final h_p=0 m, α_AQUIF=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: σ_T = 4.38 x 10⁶ N/m² σ_E = 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