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Vol. 9  No. 11



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Slug Tests

Slug tests can be used as an alternative to aquifer tests. There are many advantages to conducting a slug test;

  • they can be less expensive to conduct

  • they can be performed in small diameter monitoring wells

  • they can be performed in areas with hydraulic conductivities too low for a pumping test

There are a variety of slug test analysis methods, this newsletter will highlight three of the common methods:

In all cases, the slug test is conducted by inserting a volume of water or a slug into the well, which then causes the water table to rise to a maximum height above the initial water level (Ho). The water level will then decrease as the water drains into the aquifer, and this decrease is monitored in order to determine the hydraulic properties of the aquifer. It is also possible to bail out a volume of water and monitor the rising of the water table back to the initial water level.

Cooper-Bredehoeft-Papadopulos Method

The Cooper-Bredehoeft-Papadopulos method is applied to confined aquifers that are completely penetrated by an open borehole or well screen. The results of the slug test are plotted on semilogarithmic paper with time (log scale) and the ratio of measured head to maximum head (H/Ho) on the arithmetic scale. The plot is then matched against a series of type curves.

(From Fetter, 1994)

Click on image to see full size

The vertical time-axis, t1, which overlays the vertical axis for Tt/rc2=1.0 is then selected and the transmissivity (T) is found from:


        Where rc is the well casing radius.

Hvorslev Method

The Hvorslev Method is used for piezometers that do not fully penetrate an aquifer. As with the Cooper-Bredehoeft-Papadopulos method, H/Ho is plotted against time, however in this method time is the arithmetic scale, and H/Ho on the log scale. In this case, the time-drawdown data should plot in a straight line.

(From Fetter, 1994)

Click on image to see full size

The time associated with H/Ho=0.37 (To) is then used in the equation below to determine the hydraulic conductivity (K) of the aquifer:


Where r is the well casing radius, Le is the length of the well screen, and R is the radius of the well screen.

Bouwer and Rice Method

The Bouwer and Rice Method has been highlighted in a previous newsletter, and includes a slug test calculator. Click here to read more.


Domenico P.A. and Schwartz, F.W. (1998). Physical and Chemical Hydrogeology. Published by John Wiley & Sons, Inc. New York, NY.

Fetter, C.W. (1994). Applied Hydrogeology; Third Edition.  Published by Prentice-Hall, Inc., Englewood Cliffs, NJ.


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  • Solinst Waterlevel Meter - 100 ft waterlevel meter
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