Cooper-Jacob Solution for Confined Aquifers

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Cooper-Jacob Solution for Confined Aquifers

Description

A mathematical solution by Cooper and Jacob (1946) is useful for determining the hydraulic properties (transmissivity and storativity) of confined aquifers. Analysis involves matching a straight line to water-level displacement data as a function of the logarithm time since the start of pumping.

AQTESOLV for Windows provides visual and automatic methods for matching the Cooper-Jacob solution to pumping test data. This easy-to-use and intuitive software promotes rapid and accurate determination of aquifer properties. The program even checks the time criterion for evaluating the validity of the Cooper-Jacob approximation.

AQTESOLV also includes Jacob's correction for partial dewatering of water-table aquifers, thereby allowing use of the Cooper-Jacob solution for unconfined aquifers.

For variable rate pumping tests, the implementation of the Cooper-Jacob solution in AQTESOLV is equivalent to the method of Birsoy and Summers (1980) which applies the principle of superposition to the Cooper-Jacob approximation of the Theis equation.

Assumptions

The following assumptions apply to the use of the Cooper-Jacob solution:

	aquifer has infinite areal extent
	aquifer is homogeneous, isotropic and of uniform thickness
	pumping well is fully
	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
	values of u are small (i.e., r is small and t is large)

Solution Options

AQTESOLV provides the following options for the Cooper-Jacob solution:

	variable pumping rates
	multiple observation wells

References

Birsoy, Y.K. and W.K. Summers, 1980. Determination of aquifer parameters from step tests and intermittent pumping data, Ground Water, vol. 18, pp. 137-146.

Cooper, H.H. and C.E. Jacob, 1946. A generalized graphical method for evaluating formation constants and summarizing well field history, Am. Geophys. Union Trans., vol. 27, pp. 526-534.