Changes in a large regulated tropical river: The Paraná River downstream from the Porto Primavera Dam, Brazil

Dams disturb in the fluvial dynamics by changing the natural cycle of the rivers, interfering with the transport-deposition processes and affecting river ecology. The Brazilian part of the Paraná Basin has the largest hydrometrical power potential of the country with more than 150 hydroelectric power dams that transformed the Paraná River and its tributaries in a succession of lakes. This research aims to analyze the changes in certain fluvial variables in the last natural downstream reach of the Upper Paraná River after closure of the Porto Primavera Dam. Data acquired before and after dam construction showed changes in water discharge, bank erosion, flood pulse, bed load grain size discharge, concentration of suspended load and bedform morphology and size. Those alterations generated changes in river ecology especially on fish reproduction, benthic community, and rotifers variety and density. A review of the obscure regional literature, generally in Portuguese, is also presented.