Modeling Dynamic Processes of Mondego Estuary and Ó bidos Lagoon Using Delft3D

Estuarine systems currently face increasing pressure due to population growth, rapid economic development, and the effect of climate change, which threatens the deterioration of their water quality. This study uses an open-source model of high transferability (Delft3D), to investigate the physics and water quality dynamics, spatial variability, and interrelation of two estuarine systems of the Portuguese west coast: Mondego Estuary and & Oacute; bidos Lagoon. In this context, the Delft3D was successfully implemented and validated for both systems through model-observation comparisons and further explored using realistically forced and process-oriented experiments. Model results show (1) high accuracy to predict the local hydrodynamics and fair accuracy to predict the transport and water quality of both systems; (2) the importance of the local geomorphology and estuary dimensions in the tidal propagation and asymmetry; (3) Mondego Estuary (except for the south arm) has a higher water volume exchange with the adjacent ocean when compared to & Oacute; bidos Lagoon, resulting from the highest fluvial discharge that contributes to a better water renewal; (4) the dissolved oxygen (DO) varies with water temperature and salinity differently for both systems. On the one hand, for Mondego Estuary during winter the DO levels mainly fluctuate with salinity. On the other hand, for & Oacute; bidos Lagoon, DO distribution is determined by both water temperature and salinity. During summer, the high residence time and water temperature limit the DO levels in both systems. The high transferability and superior stability of Delft3D make this model a foundation for realistic simulation and research of distinct estuarine systems, giving support to their maintenance and restoration.

Automated summary

This study utilizes the Delft3D model to investigate the physics and water quality dynamics of two estuarine systems on the Portuguese west coast, showcasing high accuracy in predicting local hydrodynamics and water quality. The model results highlight the importance of geomorphology and dimensions in tidal propagation, as well as differences in water volume exchange and dissolved oxygen variations between the two systems. Overall, the high transferability and stability of Delft3D make it a valuable tool for realistic simulation and research of estuarine systems, supporting their maintenance and restoration.