Nonsteady Flow for Wells with Decreasing Discharge

A solution for nonsteady flow to a well completely penetrating homogeneous elastic artesian aquifer is developed. Because a continuous lowering of the water level inside wells normally corresponds to a decreasing pumping rate, it is desirable to introduce this factor into the flow problem. Consideration is given to a discharge-time exponential function that approaches an approximately constant pumping rate. The solution for the drawdown is expressed in terms of the discharge and aquifer characteristics. Discharge parameters can be determined from pumping-rate test data. A graphical solution is developed for the determination of the aquifer characteristics. This graphical solution required the numerical computation and the tabulation of a variable well function that appears in the drawdown expression. Generally, the solution developed provides greater accuracy in the calculation of the aquifer characteristics and drawdown, especially for short-period pumping tests.