Numerical Characterization of the Douro River Plume

Abstract

The Douro is one of the largest rivers of the Iberian Peninsula, representing the most important buoyancy source into the Atlantic Ocean on the northwestern Portuguese coast. The main goal of this study is to contribute to the knowledge of physical processes associated with the propagation of the Douro River plume. The general patterns of dispersion in the ocean and how the plume change hydrography and coastal circulation were evaluated, considering the main drivers involved: river discharge and wind. Coastal models were implemented to characterize the propagation of the plume, its dynamics, and its impact on coastal circulation. Different numerical scenarios of wind and river discharge were analyzed. The estuarine outflow is sufficient to generate a northward coastal current without wind under moderate-to-high river discharge conditions. Under easterly winds, the propagation pattern is similar to the no wind forcing, with a northward current speed increasing. A southward coastal current is generated only by strong westerly winds. Under upwelling-favorable (northerly) winds, the plume extends offshore with tilting towards the southwest. Southerly winds increase the velocity of the northward current, being the merging of the Douro and Minho estuarine plumes a likely consequence.