Modeling Dynamic Processes of Mondego Estuary and Óbidos Lagoon Using Delft3D

Abstract

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 Óbidos 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 Óbidos 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 Óbidos 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.

Modeling Salinity Propagation in Cikarang Bekasi Laut Channel, Bekasi Regency, West Java Province, Indonesia

“…Again, the average salinity was lower due to the freshwater supply in the channel. The behaviour of the salinity observed in the presented model was in line with findings from other studies on cases in Indonesia [16], Vietnam [27], and Portugal [28]. Salinity highly depends on the monsoonal season, where the wet season significantly reduces the salinity reached in the river.…”

Dynamics of Water, Salt, and Nutrients Exchange at the Inlets of Three Coastal Lagoons

“…The water volumes leaving the lagoon during ebb were found higher in most of the cycles. The same phenomena was observed at the Mondego estuary [35], Vassova lagoon [9], and Obidos lagoon [35], where the residual water volumes were found positive. Specifically, in the Agiasma lagoon, the ebb residual volumes were significantly higher compared to the flood residual volumes.…”

“…They concluded that the surface water inflow decreased during the last 30 years, which led to the increase of residence time. On the other hand, in the Mondego estuary and Obidos lagoon, the residence time varied from 2 days in winter to 5 days in summer and 3 days in winter to 4 days in summer, respectively [35]. The residence time is lower during winter due to higher river discharge.…”

Evaluation of future estuarine floods in a sea level rise context

“…Predictive skills are between 0.973 and 0.999 for all domains (not shown in Table 5 ). The RMSE and predictive skill values obtained are very similar to those obtained in previous numerical modeling works 65 , 71 , 73 , 80 showing an excellent accuracy of the hydrodynamic models developed in reproducing the long-wave propagation.…”

“…Tides are predominantly semidiurnal, however the propagation of the tidal wave within each coastal system has different features. In Ria de Aveiro, Mondego and Ria Formosa, the tidal amplitude is dampened upstream and its phase increases due to the shallow depths and narrower channels they present 59 , 70 , 71 . Tagus and Sado estuaries show an opposite behavior with a slight amplification of the tidal amplitude in the inner regions of the estuaries 64 , 66 .…”