Investigating the Representative of Aquifer Transmissivity Determined by Passive Response Methods: A Comparison With Time-Dependent Hydraulic Parameters Inferred From Different Stages of Pumping Tests

Aquifer pumping tests represent a standard method for estimating hydraulic characteristics, with practitioners often focusing on late period drawdown data because these are less affected by within- and near-borehole effects (e.g., borehole-storage and skin effects). Alternatively, groundwater responses to natural forcing (e.g., barometric pressure and earth tides) provide a passive method for estimating aquifer parameters at a low cost. However, to the best of our knowledge, no studies have compared parameters calculated from different periods within a pumping test with those from passive methods. Herein, we compare the aquifer transmissivity estimated using both active and passive methods in two wells located in the Beetaloo Region of Northern Australia. The active method estimates aquifer transmissivity during three periods (i.e., the early, middle, and late periods) of an aquifer pumping test, while the passive method employs groundwater responses to barometric-pressure and earth-tide fluctuations. We find that the range of best-fit aquifer transmissivity is 1.18 x 10(-5)-1.79 x 10(-5) m2/s and 1.73 x 10(-5)-2.14 x 10(-5) m(2)/s for OW1 and OW2, respectively. The transmissivity estimated from the barometric pressure response method is the largest. The aquifer transmissivity using barometric pressure responses are consistent with early- and middle-period estimates. This suggests that barometric pressure responses are more sensitive to within- and near-borehole effects. The scales of the tidal response method are smaller than those of the pumping test method.