Sado estuary
River Sado is born in the lower Alentejo, at Serra da Vigia, and it travels a distance of 180 km until its mouth in the bay of Setúbal. The course of the Sado is unusually oriented from south to north and northwest. Sado enters its estuarine zone in Alcácer do Sal where the sea water salinity begins to be felt by the mixture of the river fresh water with the one of the salty ocean. The Sado estuary is the second largest in Portugal and the main one concerning biodiversity.