Multi straight line analytical method for estimating aquifer parameters from recovery test data

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 u1<0.2 and u2<0.2. Under such simplifications, transmissivity, water storage and releasing water coefficients may be estimated simultaneously. According to the differences between storability 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. (10 refs.