Time- and frequency-domain determination of aquifer hydraulic properties using water-level responses to natural perturbations: A case study of the Rongchang Well, Chongqing, southwestern China

Effective management of groundwater resources requires accurate estimates of aquifer hydraulic parameters. One approach for estimating these parameters is to use aquifer water-level responses to natural perturbations, such as barometric pressure and earth tides. In this study, the time-and frequency-domain methods of barometric pressure and earth tide response are used to estimate aquifer hydraulic properties (transmissivity and specific storage), and taking the Rongchang well in Southwest China as an example in application. The results show that the specific storage and transmissivity estimated by the four different methods vary widely, with specific storage ranging from 8.43x10-7 -4.68x10-5/m and transmissivity ranging from 6.90x10-7 -3.40x10-6 m2/s. However, the differences in aquifer transmissivity are smaller than the aquifer specific storage. The trans-missivity obtained by the slug test is one order lager than those from Barometric (frequency), Barometric (time) and Tidal-Turnadge methods, and two orders of magnitude greater than those of Tidal-Merrit method. The Ss value obtained by the Barometric (time) method is closer to the results of the slug test, while the Ss values obtained by the other three methods are one or two orders of magnitude smaller than the slug test results. In the Tidal-Turnadge method, the uncertainty in the effective porosity introduces an additional uncertainty in the results. The errors in the calculation process are minor in comparing to the uncertainties caused by the model assumptions. For the Rongchang well, the tidal response method averages the hydraulic properties on a larger area than that of CBP model.