# Butler and Zhan Slug Test Solution for Confined Aquifers

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A mathematical solution by Butler and Zhan (2004) is useful for determining the hydraulic conductivity, specific storage and hydraulic conductivity anisotropy ratio of **confined** aquifers. The solution accounts for inertial effects in the well and oscillatory (underdamped) response. Analysis involves matching a type curve to water-level displacement data collected during a slug test.

AQTESOLV provides visual and automatic methods for matching the Butler and Zhan solution to slug test data. This easy-to-use and intuitive software promotes rapid and accurate determination of aquifer properties.

## Assumptions

The following assumptions apply to the use of the Butler and Zhan method:

- aquifer has infinite areal extent
- aquifer is homogeneous and of uniform thickness
- aquifer potentiometric surface is initially horizontal
- control well is fully or partially penetrating
- a volume of water, V, is injected or discharged instantaneously from the control well
- aquifer is confined
- flow is unsteady
- water is released instantaneously from storage with decline of hydraulic head

## Solution

Options

AQTESOLV provides the following options for the Butler and Zhan solution for underdamped slug tests:

- partially penetrating wells
- hydraulic conductivity anisotropy
- observation wells

## References

Butler, J.J., Jr. and X. Zhan, 2004. Hydraulic tests in highly permeable aquifers, Water Resources Research, vol. 40, W12402, doi:10.1029/2003WR002998.