Tidal circulation at the Quequén Grande Estuary (Argentina) mouth.

CUADRADO, DIANA G; PERILLO, GERARDO M. E.

Birmingham

Congreso; XXII General Assembly International Association for the Physical Sciences of the Ocean,; 1999

IAPSO

The Quequén Grande Estuary is located at SW of the Buenos Aires Province, Argentina. TheQuequén Harbour, one of the most important harbours in Argentina, is placed at the mouth ofthe estuary. To accommodate the large cargo vessels that operate there, the estuary has beendredged to 12-m depth from the mouth to a distance of 2-km headward. Natural depths in theriver upstream of this limit are 2-4 m. Therefore, a major step separates both reaches. Wehypothesise that this abrupt change in depth introduce major disturbances in the tidalcirculation within the harbour. Profiles of current velocity and direction as well as salinity andtemperature were made for over a tidal cycle at three stations. One current station was placedover the step (riverside) another was placed immediately after the step (harbour side),whereas the third one was located at the harbour mouth. From the analysis of the data, wefound a three layer circulation system marked by a strong stratification of the water column. There is an upper layer (1-1.5 m thick) with almost freshwater during all the tidal cycle and withwater flowing seaward. A second layer is 2-3 m thick and has salinities that vary with tidalstage and with reversing current. Whereas, on the two stations located within the harbour,there is a lower layer 6-8 m thick in which the salinity is quite homogeneous on the order of 35and practically no currents. A situation that it is not observed in the river station. A possibleexplanation for the phenomena is the influence of the in the tidal wave propagation within theestuary that may induce a standing wave by reflection against the step. .