A Stochastic Analysis of Pumping Tests in Laterally Nonuniform Media

Conventional pumping test analysis methodology assumes that aquifer transmissivity is invariant in space. The ramifications. of this assumption are examined for_ hypothetic~! ~nits who~e va~ations in transmissivity are considered to be reasonable representatmns of vanatmns possible m natural systems. The dependence of pumping test transmissivity on spatial (angular and radial) and temporal location of observations and the method of drawdown analysis is assessed. The dependence on the angular position of an observation well appear~ of little significance. Dependence on radial position, however, can be strong. The dependence on the interval of time used in the pumping test analysis is only important in highly variable systems. Methods of drawdown analysis that yield identical estima~es in uniform units yield differing estimates in nonuniform ones as a result of a difference in data-fitting procedures. A reasonable estimate of transmissivity at a regional scale can ?e obtained from a Cooper-Jacob analysis applied at a large duration ofpurnpage. In general, convent1o~al approaches for pumping test analysis should be viable in the nonuniform aquifers of the type considered here.