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Slug tests

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Slug tests

The slug test dialog window calculates drawdown/recovery of water table during slug tests after instantaneous slug removal/input. The dialog window is opened by selecting menu "File > Hydrogeologist workbench > Slug test".

 

"Slug test" dialog box.

 

Explanatory table

"so, m" text box

Initial (instantaneous) change of water level in a test well

"t, min" text box

Time of water level recovery (in minutes)

"s, m" text box

Information field showing calculated water level during recovery

"to, min" text box

Duration of slug removal  (in minutes). When the assigned value is higher than 0, the conceptual scheme applies correction for non-instantaneous slugs

"k, m/day" text box

Aquifer hydraulic conductivity

"S, --" text box

Confined storage coefficient

"rc, m" text box

Radius of casing for a test well

"m, m" text box

Aquifer thickness

"rw, m" text box

Radius of a test well

"Underdamping" option

Enables calculation of slug tests with decreasing oscillations of the drawdown function. This oscillations may occur in deep aquifers with high permeability

"Lc, m" text box

Hight of water in well casing

"T, m^2/day" text box

Transmissivity of aquifer. This is an axillary field. If a value is entered in this field, the hydraulic conductivity is automatically updated

"a, m^2/day" text box

Hydraulic diffusivity of aquifer. This is an axillary field. If a value is entered in this field, the storage coefficient is calculated

"Ss, 1/m" text box

Specific storage of aquifer. This is an axillary field. If a value is entered in this field, the storage coefficient is calculated

Key button functions are explained in section "Aquifer tests".

 

In this dialog window time entry in minutes is required for user's convenience. Hydrographs are also plotted in minutes format.

To calculate the drawdown during slug tests, solutions of Cooper and Picking are applied. Picking solution is used when text box "to, min" contains "0" value.

 

When the "Underdamping" option box is checked, the following solution is used:

where g – gravity acceleration value.

 

References

Van der Kamp G. Determining aquifer transmissivity by means of well response tests: The underdamped case // Water Resources Research. 1976. Vol. 12, N 1. P. 71–77.