Theis Step-Drawdown Test Solution for Nonleaky Confined Aquifers
Description
A mathematical solution by Theis (1935) is useful for determining the hydraulic properties (transmissivity and storativity) of nonleaky confined aquifers. For step-drawdown tests, the Theis solution is modified to include linear and nonlinear well losses occurring at the pumping well (Jacob 1947; Rorabaugh 1953; Ramey 1982). Analysis involves matching the solution to drawdown data collected during a step-drawdown test.
AQTESOLV provides
visual and
automatic methods for
matching the Theis solution with well loss 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 Theis step-drawdown test solution:
- aquifer has infinite areal extent
- aquifer is homogeneous, isotropic and of uniform thickness
- control well is fully or partially penetrating
- flow to control well is horizontal
- aquifer is nonleaky confined
- flow is unsteady
- water is released instantaneously from storage with decline of hydraulic head
- diameter of control well is very small so that storage in the well can be neglected
Solution Options
AQTESOLV provides the following options for the Theis step-drawdown 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.
See also: solution methods, pumping tests