Located downstream of Québec City, Île d'Orléans marks a transition zone for the River’s waters.
The River’s three waters
In the St. Lawrence, salinity levels vary.
Between the mouth of the St. Lawrence and the mouth of the Saguenay, it is almost as salty as the water of the Atlantic Ocean.
However, between Lake Ontario and Île d’Orléans, the water contains no salt. It is freshwater.
Between the two? We find a mixture of freshwater and saltwater coming from the ocean. These waters are called brackish.