The mouth of the Sao Francisco River was an almost obligatory stopping point for Portuguese and other nationalities' caravels that sailed along the Brazilian coast for centuries because of its fresh water, which flowed into the Atlantic Ocean, as well as to replenish supplies of local fruit and wood for ship repairs. This paradise was a source of inspiration for artists and people who lived off its abundance of fresh water, generous agricultural harvests and plentiful fishing. Unfortunately, the development advocated in the 20th century planned and built major works on the Sao Francisco River with an emphasis on economic issues, without thinking about social and environmental aspects. Thus, today the mouth of the Sao Francisco River presents problems such as the advance of the salt wedge, which cause conflicts. The study of the environmental hydrodynamics of the mouth of the Sao Francisco River is opportune because it enables a better understanding of the environmental and social problems that unbalance the environment. Prof. Dr. Antenor de Oliveira Aguiar Netto.