The role of aquifer heterogeneity in the anthropogenic uplift of Venice

Recent numerical analyses indicate that injecting seawater into a 600–800 m deep brackish aquifer underlying Venice might induce a land uplift of a few tens of centimetres over 10 years, with a significant mitigation of the floods that periodically plague the city. In real porous media, however, the hydraulic conductivity of the injected formation may exhibit a strong heterogeneity which could impact on the uniformity of the expected heave. The present paper investigates the influence of such heterogeneity on the vertical displacements predicted at the ground surface during seawater injection. A Monte Carlo simulation is carried out assuming a log-normal stationary distribution for the hydraulic conductivity with a sensitivity analysis performed on its variance. The results indicate that differential displacements larger than those currently experienced in Venice are never attained irrespective of the possible, highly uneven aquifer expansion, because of the smoothing effect exerted by the overburden.