Theis Step-Test Solution for Confined Aquifers

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Theis Step Test
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Theis Step Drawdown Test Solution for Confined Aquifers

Description

A mathematical solution by Theis (1935) is useful for determining the hydraulic properties (transmissivity and storativity) of confined aquifers. Analysis involves matching the solution to water-level displacement data collected during a step test. The Theis step test solution also includes linear and nonlinear well losses for the pumping well (Jacob 1947; Rorabaugh 1953; Ramey 1982).

AQTESOLV for Windows provides visual and automatic methods for matching the Theis step test solution to pumping 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 Theis step test solution:

	aquifer has infinite areal extent
	aquifer is homogeneous, isotropic and of uniform thickness
	pumping well is fully or partially penetrating
	flow to pumping well is horizontal
	aquifer is confined
	flow is unsteady
	water is released instantaneously from storage with decline of hydraulic head
	diameter of pumping well is very small so that storage in the well can be neglected

Solution Options

AQTESOLV for Windows provides the following options for the Theis step test solution:

	variable pumping rates
	multiple pumping wells
	multiple observation wells

References

Theis, C.V., 1935. The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using groundwater storage, Am. Geophys. Union Trans., vol. 16, pp. 519-524.

Jacob, C.E., 1947. Drawdown test to determine effective radius of artesian well, Trans. Amer. Soc. of Civil Engrs., vol. 112, paper 2321, pp. 1047-1064.

Ramey, H.J., 1982. Well-loss function and the skin effect: A review. In: Narasimhan, T.N. (ed.) Recent trends in hydrogeology, Geol. Soc. Am., special paper 189, pp. 265-271.

Rorabaugh, M.J., 1953. Graphical and theoretical analysis of step-drawdown test of artesian well, Proc. Amer. Soc. Civil Engrs., vol. 79, separate no. 362, 23 pp.