The regularization of flow on low São Francisco River is related with the dams built in its course. This paper evaluates the magnitude of flow changes caused by building of Sobradinho reservoir. It was used permanence curves to level and discharge as tool of analysis. The distance studied was 197 km from the gage station Piranhas, AL, to the mouth of the river in the Atlantic Ocean. It was used series of level and discharge of four stations wherein rating curves were corrected through Reference Levels of the IBGE. The building of Sobradinho caused a decrease percentual average of 6 to 12% in the greatest water levels (C5) and an increase of 20 to 32% in the smallest water levels (C95). There was a decrease of 9% in the maximum discharge (Q5) and an increase of 27% in the minimum discharge (Q95). The discharges Q5 and Q95 were respectively 5,652 and 1,231 m³ s -1 at Pão de Açúcar station for the period after Sobradinho. The results show that the regularization of the flow regime after the building of Sobradinho minimized the effects of greatest floods in the downstream areas, but the traditional activities of the riverine populations such as fishing, navigation and agriculture has been gradually affected.
Permanence curves; regularization of flow; dam
