CE 473/573 Groundwater
Fall 2012
Homework 9
Due Friday November 2
*53. A pump test is conducted in a leaky confined aquifer. The confining layer has a
thickness of 1.5 m, while the aquifer has a thickness of 10 m. The well is pumped at
1000 m3 /d, and it has a radius of 0.6 m. The drawdowns at 30 and 75 m from the
well are 0.4 m and 0.25 m, respectively. Determine the hydraulic conductivities of the
aquifer and the confining layer.
54. (From 2008 final) A well pumps water at 0.1 m3 /s from a aquifer with transmissivity
0.09 m2 /s that is overlain by a leaky layer of thickness 5 m. The radius of the well is
0.6 m.
a. The drawdowns measured at 50 and 150 m from the well are 0.36 and 0.18 m,
respectively. What is the hydraulic conductivity of the leaky confining layer.
(Hint: You might find the graph below to be useful.)
b. If the pumping rate were increased to 0.15 m3 /s, what would be the drawdown
at 50 m after a long time?
c. If the confined layer were an aquifuge, would the drawdown at 50 m (say) be
larger or smaller than the value in part a? Explain your answer.
0.7
0.6
0.4
0.3
0
0
K (150/λ) / K (50/λ)
0.5
0.2
0.1
0
50
100
150
200
250
300
λ (m)
350
400
450
500
*55. An aquifer with storativity 0.003 lies below an aquitard with thickness 5 m and conductivity 0.05 m/d. The unconfined aquifer above the aquitard has a head of 30 m for
a long time, and rain suddenly increases the head to 30.5 m. Compute the time for
the head in the leaky confined aquifer to reach 30.45 m.
*56. (Modified from exam 1, fall 2007) We will develop a detailed method of determining
properties of aquifers from wells, but for now use a crude approximation. Suppose a
well is pumped at 600 m3 /d for 1 day. The average drawdown (i.e., decline in head)
is 4.1 m over a circular area of radius 200 m. Estimate the storativity.