The ParaÃÂba do Sul (), or simply ParaÃÂba, is a river in southeast Brazil. It flows west to northeast from its farthest source at the source of the river Paraitinga to the sea near Campos dos Goytacazes. The river receives its name when it meets the river Paraibuna at the Paraibuna dam.
Its main tributaries are the rivers Jaguari, Buquira, Paraibuna, Preto, Pomba and Muriaé. These last two are the longest and join the main river and from the mouth respectively .
The valley of the ParaÃÂba do Sul ranges from the latitudes 20ð26' and 23ð39'S and the longitudes of 41ð and 46ð30'W and covers an area of about distributed over three states. The main economic activities are industry and cattle raising.
Presently only two parts of the river can be navigated:
Elsewhere navigation is hampered by various obstacles; waterfalls, rapids, sections with great declivity and various hydroelectric works with no locks. Other factors impeding navigation are the existence of highway and railway bridges, the proximity of roads and railways following the riverbank and the location of several cities on its banks.
The ParaÃÂba Valley is very fertile and has always been a region of relatively dense population. Cities located on or near the river are
Unlike rivers in northern Brazil where seasonal variations in water temperature generally are relatively limited, those in southern Brazil, such as ParaÃÂba do Sul, exhibit distinct differences between winter and summer. During a survey of the river in Lorena, São Paulo, the water varied from in the summer to in the winter. The pH is neutral and generally fluctuates between 6 and 8.
The ParaÃÂba do Sul basin is home to just above 100 native fish species with most in the families Loricariidae, Characidae and Trichomycteridae. About 40% of the fish species in the river basin are endemic (the genus Oligobrycon is entirely restricted to the basin) and new species have been discovered in recent years, including the small catfish Pareiorhina hyptiorhachis that only was scientifically described in 2013.
As a consequence of flowing through one of the most densely populated and industrialised parts of Brazil, the ParaÃÂba do Sul suffers from pollution. Studies of the native cichlid Geophagus brasiliensis have found that levels of some heavy metals exceed the limits set by the Brazilian Food Legislation. Other threats are dams and the approximately 70 introduced species, including 46 species of non-native fish and the parasitic copepod Lernaea cyprinacea. Several native species (e.g., Brycon insignis, Pogonopoma parahybae and Steindachneridion parahybae) are seriously threatened, and a general fall in abundance and species richness has been observed. Some, such as the endemic Hypostomus auroguttatus, have successfully adapted to the changes. The catfish Potamarius grandoculis is only known from the vicinity of the mouth of the ParaÃÂba do Sul and Doce Rivers, but it may already be extinct.
Other threatened species in the ParaÃÂba do Sul basin are the bivalves Diplodon dunkerianus, D. expansus and D. fontaineanus, and the Hoge's side-necked turtle (Mesoclemmys hogei).
A national conservation plan with recommendations for the river basin was published in 2010.