Mechanical interaction between the Río de La Plata and the coastal aquifer system in the Northeast of the Province of Buenos Aires, Argentina

In this work the tidal-induced method is applied with the goal of analyzing the mechanical interaction between the Río de La Plata and the Puelche and Paraná coastal aquifers in Buenos Aires Province, Argentina. From this analysis, the hydraulic diffusivities and conductivities of the aforementioned aquifers were estimated. Applying a non-invasive technique that uses a natural signal instead of traditional pumping tests is key due the high levels of pollution of the surface waters in the study region. The amplitude and the phase-shift of the main components observed in the signals are used to estimate the hydraulic diffusivity by using van der Kamp (1972) solution for confined aquifers. Using different tidal components allows to obtain additional information about the heterogeneities of the aquifer. The results suggest that the Paraná aquifer presents an increase in the hydraulic diffusivity with the distance from the coast, while the Puelche aquifer is more homogeneous. Hydraulic conductivity values can be calculated from the elastic parameters of the formations. To obtain average conductivity values, a weighted average of the estimates obtained for each frequency was carried out. The hydraulic conductivity value corresponding to the Puelche aquifer is within the range of values obtained through pumping tests, while the estimate corresponding to the Paraná aquifer constitutes a contribution to the hydrogeological knowledge of the region since this aquifer has been little studied.