Salinity intrusion in the Guapimirim estuary, Rio De Janeiro state, Brazil

Abstract

This work was conducted in the Guapimirim estuary, the main tributary of the Guanabara Bay. This system is located in a preserved area in the catchment basin of the bay, inside the Guapimirim Environmental Protection Area. The estuary presents a meandering channel with 3 meters mean depth. The aim of this work is to evaluate the salinity intrusion dynamics in response to the tide and freshwater discharge, as well as its effects on the water column structure and residence time. Surveys were performed to assess the salinity structure along the estuary main channel under different freshwater discharges (dry and rainy period) and tide (neap and spring). The results showed significant differences in the water column structure, presenting high stratification in neap tide and conditions homogeneous in spring tide. The salinity front (SF) showed a bigger displacement in the spring tide. Under highly stratified conditions, in neap tide, its displacement was bigger with smaller tidal amplitude. The location of SF inside of the estuary, in the high water, was influenced manly by freshwater discharge. The residence time in the Guapimirim estuary was longer in neap tide and dry period, presenting a good relationship with freshwater discharge.