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6.4.3 The Theis Solution - Transient Flow to a Well in a Confined Aquifer
Folder: \pm5\examples\calibration\calibration3\
Overview of the Problem
This example gives an approximation of the Theis solution with a numerical model. Given the
aquifer properties, transmissivity and confined storage coefficient, the Theis solution predicts
drawdown in a confined aquifer at any distance from a well at any time since the start of
pumping. The assumptions inherent in the Theis solution include:
(1) The aquifer is homogeneous, isotropic and of uniform thickness,
(2) The aquifer is confined between impermeable formation on top and bottom, and of infinite
areal extent.
(3) The initial piezometric surface is horizontal and uniform.
(4) The pumping rate of the well is constant with time.
(5) The well penetrates the entire aquifer and the well diameter is small.
(6) Water is removed from storage instantaneously with decline in head.
All of these assumptions, with the exception of infinite areal extent, can be represented by a
numerical model.
In this example, a fully penetrating well is located at the center of the model domain and
withdraws water at a constant rate. The drawdown of the hydraulic head is monitored with time
at a borehole 55m from the pumping well. The model parameters are listed below. Your task is
to construct a numerical model, calculate the drawdown curve at the borehole and compare it
with the analytical (Theis) solution.
Initial hydraulic head = 0.0 m
Transmissivity = 0.0023 m /s
2
Storage coefficient = 0.00075
Pumping rate = 4 × 10 m /s
-3 3
Total simulation time = 86400 s
Number of time steps = 20
Time step multiplier = 1.3
Number of SIP iteration paramters = 5
Convergence criterion of head change = 0.0001
Maximum number of iterations = 50
6.4.3 The Theis Solution - Transient Flow to a Well in a Confined Aquifer