Environmental Engineering Reference
In-Depth Information
A derivation of the formula is found in Sidebar 12.1. Here we describe a short
command sequence by which the piezometric head values in the vicinity of the well
are calculated. At first, the values of the input parameters have to be given:
h0 = 5;
T = 5.e-6;
Q = 1.e-4;
r0 = 0.1;
Afterwards the radius vector r is specified. For each radius within the vector the
lowering of the piezometric head h is calculated:
r = [0.1:0.1:20];
The following command initiates the computation of the desired values
according to formula ( 12.2 ):
h = h0 + (Q/(2*pi*T))*log(r/r0);
, log is the natural logarithm to the basis e . In the vector h we
now find all piezometric heads for the radii, given in the radius vector r .
For
In MATLAB
®
plot (r,h);
ylabel ('piezometric head [m]'); xlabel ('distance [m]');
The result is shown in Fig. 12.2 .
22
piezometric head [m]
20
18
16
14
12
10
8
6
distance [m]
4
0
5
10
15
20
Fig. 12.2 Drawdown of groundwater piezometric head in a confined aquifer due to pumping
(Thiem formula)
 
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