Abstract: In the pumping tests to determine hydrogeologic parameters, the residual drawdown are considered more reliable because of the automatically controlled flow rate to the well during the pump shut-off period. Some strict limits and assumptions in classical Theis well function and Theis recovery method induce that it’s not suitable to practice. In practice, leaky aquifers are more and their flow to well will reach steady soon, while the pump discharge often is unsteady after begin. The discharge in the steady flow is substitute into Hantush-Jacob leaky aquifer model; then the extended Kalman filter is used to compute the parameters such as transmissivity, storage coefficient and leakage coefficient. Comparing with historical and in-site data indicates that estimated data match well with pump test data.

Key words: leaky aquifer, single well, recovery, extended Kalman filter, hydrogeologic parameters