Effect of wind and river discharge on water quality indicators of a coastal lagoon

It is well known that some factors could effectively control the hydrodynamics of Brazil's largest coastal lagoon (Patos Lagoon coastal system); however the knowledge about the effects of such factors on its water quality indicators (WQI) is scarce. Therefore, our aim is to assess the relative importance of the main factors that control the hydrodynamics of the Lagoon (wind and river discharges) on spatial and temporal variations of water quality indicators, being these indicators the suspended solids, dissolved oxygen, total inorganic nitrogen and chlorophyll-a. With this knowledge we can indicate areas with greater or lesser susceptibility to water quality deterioration. We applied the MOHID 2D numerical model to assess the combined effect of winds and river discharge on WQI throughout the entire lagoon system. Our results indicate that winds combined with river discharge affect the spatial-temporal variation of the WQI, with the largest variations occurring under high river discharge and southwest winds, especially in the estuarine area. Regardless of the magnitude of the incoming discharge, the spatial variations are similar for the same winds. Sub-areas with homogeneous conditions are observed independently of the hydrodynamic forcings. (C) 2020 Elsevier B.V. All rights reserved.