By Tripp Winters

Residual Drawdown The rise in the water level as pumping stops. Expressed as the original water level before the start of pumping and the water level measured at time t’.

Theis Recovery Method Usually only valid for confined aquifers that are fully penetrated by a well that is pumped at a constant rate Can be used for leaky & unconfined aquifers if limiting conditions are satisfied

Recovery Test after Constant Discharge Test

Theis’s Recovery Method for Leaky Aquifers After disregarding any storage affects in the confining aquitard, we express the RD (s’) at a distance ® from the well. If the pumping times are long, leakage through the confining aquitards will affect the water levels. If the times are short, Theis can be used to determine the transmissivity.

Theis’s Recovery Method for Unconfined Aquifers Only applicable for late-time recovery data At late-times, the effects of elastic storage have dissipated The RD data will ten fall on a straight line in the semi- log s’ versus t/t’ plot used in the Theis recovery Method

Theis’s Recovery Method for Partially Penetrating Wells Can be used if the pumping time is long The semi-log plot of s versus t yields a straight line with a slope identical to a completely penetrating well.

Recovery Test after a Constant Drawdown Test Theis method can be applied, provided that the discharge at the moment before the pump is shut down is used in equation :

Recovery Test After Variable-Discharge Test