A new method for determining hydrogeological parameters of aquifer from recovery data is proposed. The possible difference between releasing water coefficient of aquifer in the stage of water level declining and water storage coefficient as water level rising is taken into consideration. In order to derive the equations for estimating the hydrogeological parameters of aquifer

the same simplification way for two well functions describing two drawdowns is taken; one of these drawdowns is caused by continuous pumping

and the other is caused by imagined recharge with the same pumping rate after pumping stops. This means that the first three terms in the series expressions of the Theis’ well functions are taken as simplified expresses of well function

and the simplified condition is that two dimensionless times are and . Under such simplifications

transmissivity

water storage and releasing water coefficients may be estimated simultaneously. According to the differences between storativity and releasing coefficient

the deformation reversibility of tested aquifer between discharge stage and recharge stage may be judged. Finally

an example is given to show the application procedure of the proposed method.