Modelling scenarios of contaminant transport in an equivalent porous medium

Groundwater represents the largest supply of drinking water in the world (25-40%). Increasing urban development and increasing industrial activities, growing water demand due to climate change, and the consequent increase in urban runoff volumes due to the presence of sealed surfaces are causing ad-verse effects on groundwater both quantitatively and qualitatively. To address water stress, Managed Aquifer Recharge (MAR) represents an engineered ap-proach to water security. MAR techniques aim to recharge the aquifer under controlled conditions for the purpose of subsequent recovery or as a barrier to prevent seawater intrusion. The reuse of urban water to implement this strate-gy is adopted from the perspective of environmental sustainability. However, the presence of residual contaminants in the injected stream challenges the feasibility of this solution because it may affect human health. In this context, the site modeled in the present work is located adjacent to the municipality of Avetrana, a place in which a confluence will be built from a channel in order to collect stormwater and floodwater thus protecting the town. The case study has a high level of hydraulic disturbance that makes it necessary to evaluate the vulnerability to pollution of the karst aquifer, which is characterized by a low anti-pollution capacity and therefore very fragile. As a result, it was necessary to perform a numerical simulation of groundwater flow and mass transport in the affected area. FEFLOW software, based on the finite element method, was used to determine the three-dimensional numerical groundwater model. The groundwater flow field was obtained by inputting boundary conditions and pa-rameters derived from hydrogeological field surveys and literature review. Spe-cifically, the methodology involved developing the conceptual hydrogeologic model of the aquifer and then modeling the mass transport of a hypothetical contaminant under different scenarios. Considering that the input conditions in the transport model represent ex-treme and occasional situations, the modeling performed showed that the geo-logic structure represents a potential barrier to pollution. To sum up, the purpose of this study was to make the model a good approx-imation of the groundwater system and to provide reference to prevent pollu-tion in karst aquifers.