Analyzing Aquifer Test Data From a Bounded Aquifer

Rural and exurban municipalities that dependent on resident owners' wells are vitally interested in preventing failure of the groundwater supply during the inevitable drought. These municipalities have been given the mandate by the State to “ .. insure(ing) that new developments incorporate adequate provisions for a reliable, safe and adequate water supply to support intended uses within the capacity of available resources.” In particular, these towns that depend on on-lot wells are particularly vulnerable to overdrawing their groundwater without means to predict neither the potential for nor the extent of an emergency. Short term testing to predict long term behavior is fraught with prediction limitations and errors.

In the usual analysis of pumping data, the assumption is made that one of the variations of the Theis family of equations can be used to interpret and extrapolate aquifer pumping data. The assumptions required for the use of Theis equations produce solutions that are at odds with data obtained by aquifer tests in fractured rock geologies and their use can under predict the long term impact of groundwater withdrawal. This paper proposes an aquifer test analysis that explores the applicability of the test to long term predictions. It further recommends a conservative maximum groundwater withdrawal rate that would be consistent with prudent long term municipal planning.