INTERPRETING RECOVERY DATA FROM PUMPING TESTS

The shape of hydrographs of the recovery of well water levels for pumping tests in confined aquifers is shown to depend on well storage. This demonstration suggests that the standard method of interpretation of such recovery curves, as described in Todd, will not give accurate values unless the time after start of recovery is greater than about 25R(c)2/T (see text for notation). Further, it is also demonstrated that if a leaky (low permeability) layer lies above or below the pumped aquifer the recovery curves can be modified significantly and are liable to misinterpretation.