Identification of parameters in semiconfined aquifers

A method is presented for identification of parameters from pumping tests, in semiconfined aquifers with storage release from the aquitard. Four parameters are to be evaluated, namely: the transmissivity of the aquifer; the storage coefficient of the aquifer; the leakage coefficient of the aquitard; and the storage coefficient of the aquitard. The Neuman and Witherspoon solution for the drawdown, valid for all time intervals, is used and this solution is not amenable to the graphical procedure. The optimisation problem is solved by the sensitivity analysis technique. The method has the merit of utilising the field data for all times without classifying them into small and large time intervals. A computational procedure for evaluating the drawdown integral is presented. Two illustrative examples are presented to demonstrate the application of the method.