Hydrodynamic numerical simulation at the mouths of the Parana and Uruguay rivers and the upper Rio de la Plata estuary: A realistic boundary condition

A hydrodynamic numerical study at the mouths of the Paraná and Uruguay rivers and the upper Río de la Plata is presented in this paper. Water Quality Mapping numerical model was implemented and realistic and very simple boundary conditions were specially developed for this complex estuarial system. A set of numerical experiments were carried out using different constant discharges for the Paraná and Uruguay rivers but unrealistic currents were generated. In order to obtain more realistic results, a set of numerical simulations were carried out imposing water level timeseries at the open boundaries. M₂, S₂, K₁ and O₁ harmonic constants were used to generate water levels at Zárate (Paraná river), Nueva Palmira (Uruguay river) and the eastern boundary of the domain (La Plata–Colonia). A mean water level equal to zero was set between La Plata and Colonia. Positive mean water levels (0.3–0.4 m) were imposed at Zárate and Nueva Palmira to simulate the hydraulic slope of both rivers and, consequently, to generate realistic and unsteady discharges. These boundary conditions, built by means of the addition of a mean water level and the astronomical tide, significantly improve the simulated currents at the northernmost region of the RDP estuary.