Dougherty-Babu Solution for a Step Test in a Confined Aquifer

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Dougherty-Babu Step Test
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Dougherty-Babu Solution for Step-Drawdown Tests in Confined Aquifers

Description

A mathematical solution by Dougherty and Babu (1984) is useful for determining the hydraulic properties (transmissivity, storativity and hydraulic conductivity anisotropy ratio) of confined aquifers. Analysis involves matching the solution to water-level displacement data collected during a pumping test. The Dougherty-Babu solution accounts for wellbore storage effects in a finite-diameter, partially penetrating well with wellbore skin. Moench (1988) extended the method to account for anisotropic conditions. The Dougherty-Babu 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 Dougherty-Babu solution to step-drawdown 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 Dougherty-Babu step test solution:

	aquifer has infinite areal extent
	aquifer is homogeneous, anisotropic and of uniform thickness
	pumping well is fully or partially penetrating
	flow to pumping well is horizontal when the pumped well is fully penetrating
	aquifer is confined
	flow is unsteady
	water is released instantaneously from storage with decline of hydraulic head

Solution Options

AQTESOLV for Windows provides the following options for the Dougherty-Babu step test solution:

	large-diameter pumping wells
	variable pumping rates
	multiple pumping wells
	multiple observation wells
	partially penetrating wells
	boundaries

References

Dougherty, D.E and D.K. Babu, 1984. Flow to a partially penetrating well in a double-porosity reservoir, Water Resources Research, vol. 20, no. 8, pp. 1116-1122.

Moench, A.F., 1988. The response of partially penetrating wells to pumpage from double-porosity aquifers, Proceedings of the International Conference on Fluid Flow in Fractured Rocks, Atlanta, GA, May 16-18, 1988.

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.

Bear, J., 1979. Hydraulics of Groundwater, McGraw-Hill, New York, 569p.