Author(s): Adolfo J Cardozo; Luis P. Thomas; Margarita Portapila; Beatriz M. Marino; Martín Romagnoli
Keywords: Quequén Grande; Hydrodynamic modelling; Estuaries
Abstract: The microtidal coastal plain Quequén Grande River estuary (Buenos Aires, Argentina) is 3-5m deep in its middle and upper sections while a deep-water harbour is located in its 2km-long lower section. Here the original shape was substantially modified by means of frequent dredging to provide favourable navigational conditions, the widening and stabilization of the banks, and the construction of piers and two important jetties to protect the port from the storms and waves. Minor falls located about 15km inland mark the estuary head and impose special boundary conditions to the flows. These features make it important to analyse the dynamics of the currents and sediment transport in order to prevent the possible degradation of the aquatic system. In this work, numerical solutions obtained using the FVCOM hydrodynamic computational open code model of oceanic circulation are presented. The results are calibrated and validated with field measurements performed during complete tidal cycles and with data provided by fixed monitoring stations. The dynamics of the saline intrusion and sediment transport is determined varying the magnitude of the river discharge and the tidal height in representative ranges of the estuary parameters, thus contributing to the global understanding of the estuarine behaviour. The findings of the numerical simulation compensate the scarce systematic measurements due to the wide range of the river flow and the morphologic and structural changes that occurred in the lower sector, mostly in the last decades. The practical importance of this study resides in its contribution to the comprehension of the transport of particulate matter, whose settling implies continuous dredging operations to maintain the 12-14m depth in the lower sector, and the eventual upstream dispersion of pollutants released into the waters from an urban area placed in the last kilometres of the estuary, which may cause serious ecologic and economic consequences.