Impact of increased river discharge on water renewal in a tropical estuarine-bay system

Abstract

As economic development progresses and anthropogenic pressures intensify, estuaries become increasingly vulnerable, exhibiting higher levels of pollution, enhanced eutrophication, and reduced dissolved oxygen, which compromises the sustainability of these coastal environments. This study sought to better understand these features by applying the hydrodynamic, transport, and water quality modules of the image.pngmodel to evaluate water renewal in a tropical estuarine-bay System, Guaratuba Bay, located on the coast of Paraná, in southern Brazil, and its implications for oyster farming. Two scenarios were simulated: (i) the current condition, with regionalized river discharges; and (ii) an increased river discharge scenario, with tripled river discharges, identifying a decrease in salinity. The results indicated that water renewal is strongly influenced by river discharge and tidal dynamics, the renewal being more efficient in the inner part of the bay. In the scenario with increased river discharge, a significant reduction in water age was observed throughout the bay, indicating greater renewal efficiency. However, this intensification also resulted in a substantial decrease in salinity, especially in the inner and intermediate regions, where values dropped below 15 psu in the second scenario. Although water renewal may potentially favor the dilution of pollutants, a sharp reduction in salinity could compromise the viability of aquaculture, such as oyster farming.

Keywords: estuaries, oyster farming, salinity, SisBaHiA.