Modelling stream-groundwater interactions in the Querença-Silves aquifer system

Streamflow in the Central Algarve, during dry seasons, is primarily base-flow. The stream network is also affected by water losses along influent reaches in wet seasons, across streambeds and karstic swallow holes. The representation of these streams in a finite element groundwater flow model allowed an investigation of the factors controlling the spatial distribution of the stream-groundwater interactions. After calibration of transmissivity, the implemented model provided a reliable representation of the equipotential surfaces of the aquifer, accommodating the values of the regional scale water balance. The subsequent introduction of the stream network in the model allowed the identification and systematisation of the parameters and variables needed to improve the conceptualisation of the river-aquifer relations at the local scale. The use of models combined with collected data contributes to the optimisation of monitoring networks and promotes the understanding of the boundary conditions at the regional and local scale.