During early pumping times (Fig. a), conduit linear flow (conduit or wellbore storage effect) is characterized by a straight line with a slope n = 1 on the diagnostic plot. After a transition flow period, the system may or may not exhibit a bi-linear flow period (Fig. b), indicated by a one-fourth-slope straight line that lasts as long as the conduit boundaries do not affect the flow pattern. As time increases, the flow in the matrix becomes one-dimensional (horizontal, parallel and perpendicular to the conduit) as illustrated on Figure c. On a diagnostic plot, the slope of the derivative curve is n = 0.5. As pumping continues, the flow pattern can change from parallel flow to pseudo-radial flow (Fig. d). During this period, the pumped water originates from farther away and the local effect of the finite-length conduit tends to disappear. The drawdown curve tends to the Jacob straight line with a slope n = 0 of the derivative at late times, but this would arise only if the duration of the pumping test is very long. This four-period flow-pattern geometry makes it impossible to interpret such drawdown curves with classical techniques. The corresponding typical drawdown and derivative curves (diagnostic plot) are illustrated on Fig. e.