Determination of unconfined aquifer hydraulic properties from recovery test data

This paper analyzes the sensitivity of drawdown to four hydraulic parameters in unconfined aquifers: horizontal and vertical hydraulic conductivity K-r and K-z, storage coefficient S, and specific yield S-y. Sensitivity coefficients indicate that the sensitivity varies with time for each aquifer parameter, and K-r, K-z, S, and S-y are identifiable from recovery test data. An inverse method was used to calculate the four parameters from residual drawdowns. Results of application examples demonstrate that residual data provide valid information in the determination of unconfined aquifer hydraulic parameters.