Using Solver to Estimate Aquifer Parameters for Non-Leaky and Leaky Unsteady Confined Aquifer Tests

Aquifer testing of confined aquifers has been used for many years to aid with the determination of the key aquifer parameters, including transmissivity, storativity, and leakance. A myriad of published methodologies have been previously developed. Some of these solutions have led to the development of expensive, proprietary software. Others require development of complex numerical models, while still others require complex calculus using inverse Laplace transforms or numerical inversion. Two common aquifer testing problems are the determination of aquifer parameters for non-leaky and leaky confined aquifers. A simple alternative approach using new computer tools can be used to estimate the aquifer parameters for both non-leaky and leaky confined aquifers given transient drawdown data from a nearby observation well. The proposed alternative methodology uses Microsoft Excel and Solver to inverse model likely best-fit aquifer parameters. The approach does not require Visual Basic or Visual Basic Assistant (VBA) programming or numerical inversion. It adapts recently published analytical approaches and uses a simple least-squares error minimization approach using the sum of square terms in combination with the evolutionary genetic solution algorithm available in Solver. It is particularly useful for teaching undergraduate geoscience or engineering majors due to its accessibility. The results provided compare favorably to other published methods.