Interactions and exchanges between surface water, groundwater, and the atmosphere are some of the most relevant functions that regulate environmental characteristics in wetlands. These functions depend on environmental attributes such as topography, geological-geomorphological setting and, in the case of coastal wetlands, the relationship with tidal flows. The aim of this work is to analyse the water flows in different landscape units of the wetland in the coastal plain of the Río de la Plata estuary within the Parque Costero del Sur biosphere reserve. For this purpose, monthly water balances and groundwater level measurements were compared with daily precipitation and tidal height data from the Río de la Plata estuary. The results show how water dynamics in the wetland responds to different geological-geomorphological and climatic controls. The main inlets and outlets of water, as well as the flow exchanges, vary according to the different landscape units, forming a complex system on which the main ecological features depend.Centro de Investigaciones del MedioambienteCentro de Investigaciones Geológicas