Residence time patterns of Mirim Lagoon (Brazil) derived from two-dimensional hydrodynamic simulations

Abstract

Mirim Lagoon (ML) is a large choked lagoon connected to the Patos Lagoon estuary and eventually to Mangueira Lake. Together, these water bodies form the most extensive lagoon system in South America. ML is a transboundary basin shared by Brazil and Uruguay that serves as a water reservoir, providing freshwater for public supply and agricultural activities. This work evaluated the transport patterns and residence time of ML using numerical simulations forced by time series of the tributaries’ discharge and by reanalysis of atmospheric data. The results indicate a mean residence time of 180 days, and spatial and temporal variations of up to 100 days were presented. The discharge conditions and the wind regime are the causes of such high variability on the distribution of the residence time at Mirim Lagoon. This high variability indicates that specific periods are more susceptible to be impacted by exogenous contaminants.