Obtaining the steady-state drawdown solutions of constant-head and constant-flux tests

Abstract

The solutions of constant-head and sonstant-flux tests are commonly used to predict the temporal or spatial drawdown distribution or to determine aquifer parameters. Theis and Thiem equations, for instance, are well-known transient and steady-state drawdown solutions, respectively, of the constant-flux test. It is known that the Theis equation is not applicable to the case where the aquifer has a finite boundary or the pumping time tends to infinity. On the other hand, the Thiem equation does not apply to the case where the aquifer boundary is infinite. However. the issue of obtaining the Thiem equation from the transient drawdown solution has not previously been addressed. In this paper, the drawdown solutions for constant-head and constant-flux tests conducted in finite or infinite confined aquifers with or without consideration of the effect of the well radius are examined comprehensively. Mathematical verification and physical interpretation of the solutions to these two tests converging or not converging to the Thiem equation are presented. The result shows that there are some finite-domam solutions for these two tests that can converge to the Thiem equation when the time becomes infinitely large. In addition, the time criteria to give a good approximation to the finite-domain solution by the infinite-domain solution and the Thiem equation are investigated and presented. Copyright (C) 2008 John Wiley & Sons, Ltd.