“Noteworthy discoveries gleaned from analysis of an unconfined-aquifer test” by A.F. Moench (USGS)

Modifications of a conventional analytical model for flow to a well in an unconfined aquifer allow for improved accuracy in estimates of unconfined-aquifer parameters and improved understanding of flow processes in unconfined aquifers. The improvements are a consequence of the faithful replication by model simulation of drawdown measurements made in observation piezometers during an aquifer test. Using data from a detailed aquifer test conducted in Cape Cod, MA it is shown why, when using conventional analytical models, specific storage is commonly overestimated and specific yield is commonly underestimated. Contrary to popular belief, saturated thickness is found to be one of the estimable parameters and specific yield is found to be a time-invariant property of the aquifer. These and related ‘noteworthy discoveries’ will be discussed.