GGU-PUMPTEST: Theis recovery method

The theoretical principles are described in Langguth/Voigt on pages 171 to 175. The example file "Theis recovery.pvs" can be found in the program's example folder.

This method entails a drawdown in a well with a constant pumping rate. Recovery begins after switching off the pump in the extraction well. The recovery course is measured in a nearby monitoring well.

The following data is required for this method:

• the pumping duration until the pump is switched off;

• the constant pumping rate until the pump is switched off;

• the aquifer thickness H;

• the specification of confined or unconfined aquifer;

• the course against time of the recovery h.

After defining the input values they are entered against

(dt + tp)/dt

dt = time difference until 1^st measurement
tp = pumping duration

and the best-fit curve for this function determined; from this, the permeability can be calculated.

Example:

This is the example for Gauge 11b in Langguth/Voigt. After switching off the pump the following recovery is measured in Gauge 11b:

Table 5 Recovery values in Gauge 11b

In the menu item "File/New", press the "Theis recovery" button and then go to the menu item "Edit/Edit values". Change the number of values to "17" and enter the measured data from the above Table 5.

Navigate through the table using the "Forw." button in order to enter further values. Go to the "Evaluation/Theis recovery" menu item.

Enter the values in the dialog box and confirm with "OK".

The "a" and "b" values describe the course of the best-fit curve through the data. The "r" value is the correlation coefficient, representing the quality of the best-fit curve. Below this, the permeability and the transmissivity are given.

The solution given in Langguth/Voigt is:

• T = 8.4 · 10^-3 m²/s

The minor differences are due to the purely visual evaluation employed by Langguth/Voigt.

If you adopt the result text, it is entered into the "Result text" box in the form.