User's guide of Proceessing Modflow 5.0

272 Processing Modflow
6.4.4 The Hantush and Jacob Solution - Transient Flow to a Well in a Leaky
Confined Aquifer
Folder: \pm5\examples\calibration\calibration4\
Overview of the Problem
This examples demonstrates how to approach leaky confined aquifers. A leaky confined aquifer
is overlaid and/or underlaid by geologic formations, which are not completely impermeable and
can transmit water at a sufficient rates (Fig. 6.41). Hantush and Jacob (1955) give an analytical
solution to describe the drawdown with time during pumping with a well in a leaky confined
aquifer. In addition to the assumptions in the Theis solution, the analytical solution require two
assumptions - the hydraulic head in the overlying oder underlying aquifer is constant during
pumping in the leaky confined aquifer and the rate of leakage into the pumped aquifer is
propertional to drawdown.
In this example, a pumping well withdraws water at a constant rate from the leaky confined
aquifer. The drawdown of the hydraulic head is monitored with time at a borehole 55m from the
pumping well. The borehole is located in the leaky confined aquifer. The initial hydraulic head
is 8 m everywhere. Specific yield and effective porosity are 0.1. The other aquifer parameters
are given in Fig. 6.41. The analytical solution for this case is given in Table 6.6.
Your task is to construct a numerical model, calculate the drawdown curve at the borehole
and compare it with the Hantush-Jacob solution. Note that the parameters for the confined leaky
aquifer are the same as the previous example, so we can compare the results of these two
examples.
Table 6.6 Analytical solution for the drawdown with time
Time (s) drawdown (m) Time (s) drawdown (m)
123 0.0067 4932 0.336
247 0.03 12330 0.449
352 0.052 24660 0.529
493 0.077 35228 0.564
1233 0.168 49320 0.595
2466 0.25 123300 0.652
3523 0.294
6.4.4 Transient Flow to a Well in a Leaky Confined Aquifer