The Hydrographic Region II

For management purposes, the State of Rio de Janeiro is divided into nine Hydrographic Regions, determined by Resolution No. 107 of May 22, 2013 of the State Water Resources Council (CERHI-RJ). Each of them has its own Basin Committee, which works together with the State Institute for the Environment (INEA), the water agencies and CERHI-RJ itself, in favor of planning the use of water resources in these regions.

The Hydrographic Basins of the Guandu, Guarda and Guandu-Mirim rivers, the area of ​​influence of the Guandu-RJ Committee, make up Hydrographic Region II.

Guandu River Basin

The Guandu River drains a basin with an area of ​​1,385 km² and its entire route, to the mouth, totals 48 km. It is originally formed by the Ribeirão das Lages river, which became known as the Guandu river after its confluence with the Santana river. Its main tributaries are the Macacos, Santana, São Pedro, Poços e Queimados and Ipiranga rivers. Its final rectified course is called the São Francisco Channel.

Guandu is divided into two branches, having, in both, dams that belong to CEDAE. Joined to the east arm, is the Guandu lagoon. The rivers of Poços, Queimados and Ipiranga flow into it.

Downstream from the CEDAE island, the Guandu crosses a small stretch of rocky bed, forming a rapid. Then, it heads southwest and travels for about 9 km until it enters the São Francisco channel and continues for another 15 km until it flows into Sepetiba Bay.

Much of the Guandu comes from an important source: the Paraíba do Sul river. At Light’s hydroelectric plant, downstream from Santa Cecília, water is transposed through forced canalization at the plants. This movement causes about 60% of the waters of Paraíba do Sul to find the Ribeirão das Lajes River, which, in turn, flows down to form the Guandu and supply Rio de Janeiro.

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Guarda River Basin

The Guarda River Hydrographic Basin covers an area of ​​346 km², and neighbors, on the right bank, the Guandu River basin. Its main source is the Valão dos Bois, a channel about 35 km long and with a drainage area of ​​131.4 km². It can be said that the Guarda river begins after the confluence of the Valão dos Bois with the Piloto river and develops along approximately 7 km to its mouth, in the Bay of Sepetiba.

Its main tributaries are the Piloto, Cai Tudo and Itaguaí rivers. In the final stretch, the Guarda River presents, on its banks, strips composed of typical mangrove vegetation. From the vicinity of the old Rio-São Paulo road, the Guarda river runs through the urban area of ​​Campo Lindo and the large sand exploration zone of the “Polígono de Piranema”, receiving the Valão do China on the left bank, which crosses the neighborhood of Campo Lindo, and, soon after, an agricultural area.

During the floods, several caves are flooded by the waters of the Valão dos Bois, when the fragile dikes break. The Valão dos Bois canal flows into the Rio da Guarda.

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Guandu-Mirim River Basin

The Guandu-Mirim river basin covers an area of ​​about 190 km². The Guandu-Mirim river is born in the Serra do Medanha, named Guandu-do-Sena, formed by several sources. Soon after, it changes its name to the Prata do Medanha river until its confluence with the Sapê river, when it changes its name to Guandu-Mirim. Its waters enter the D. Pedro II channel and, later, the São Francisco Channel, where they flow into the Sepetiba Bay.

Its main tributaries are the Guandu do Sapê, Cabenga, dos Cachorros and Campinho rivers.

The current D. Pedro II-Guandu channel represents the diversion of the former course of the Guandu-Mirim river, whose bed marked the boundary between the former states of Rio de Janeiro and Guanabara, which ran out through the São Francisco Channel. With this modification, while the Guandu-Mirim river currently marks the border between the cities of Nova Iguaçu and Rio de Janeiro, the former riverbed, which is now dry, remains a political boundary between the municipalities.

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