| Summary: | Ria de Aveiro lagoon is a complex shallow water system located in the northern coast of Portugal. The interaction between tides and river flow, in particular the significant freshwater contribution from Vouga river for most of an average year, induces longitudinal salinity gradients, justifying Ria de Aveiro classification as a typically estuarine environment. The adjustment of saline patterns induced by climate change may have consequences in the ecological equilibrium of this environment. Saline intrusion due to SLR and river flow decrease may induct saline stress in the fertile lowlying lands of Baixo Vouga and saline intrusion in aquifers. In this context, this study intends to answer to the question: How do seasonal saline distribution patterns are expected to adjust to climate change in Ria de Aveiro lagoon? Only recently the scientific community began to explore this issue through numerical modeling studies applied to estuarine environments worldwide. The MOHID 2D numerical model was used to simulate reference and future scenarios. The numerical grid used was updated with 2012 data and includes low lying adjacent lands, so that marginal flooding could be simulated. The hydrodynamic and the salt and heat transport models were calibrated with the RMS errors and Skill values reflecting the good performance of the model in reproducing salt transport processes. As main contributors to water salinity patterns adjustment in an estuarine environment, mean sea level and river flow from main tributaries at wet and dry conditions were adopted as variables of this study. Thus, three Future scenarios for wet (A) and dry (B) conditions were defined: A1 and B1 to evaluate the isolated effect of local SLR projected; A2 and B2 considering the projected changes at daily average river flow of the main tributaries; and A3 and B3 combining SLR and river flow changes projected, therefore, the more realistic ones. Projections for the end of XXI century are based on A2 SRES scenario. It can be concluded that in wet season projected scenarios the increase in saline concentration is more significant than for the dry season ones, being that increase more significant in the lagoon upstream regions. However, in dry season future scenarios the saline intrusion tends to go further inland due to the negligible freshwater inflow projected. The results obtained, in particular: the salinity concentration increase and the salt inland intrusion; the upstream saline increase as consequence of river flow projected reduction; and the larger salinity increase in upper lagoon regions, are in accordance with the ones achieved in the majority of the studies related to SLR impact in estuaries salinity, found in literature. This study could be expanded to other estuarine environments and other variables with influence in ecology of these environments.
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