The State of São Paulo was authorized, on an exceptional basis, to increase water abstraction from the Paraíba do Sul River basin – which supplies neighboring Rio de Janeiro. The measure is to reinforce the Cantareira system, which supplies water to around 10 million people in the São Paulo metropolitan region. The request was made by Sabesp (Basic Sanitation Company of the State of São Paulo).
The decision is part of an agreement signed between the 3 states through which Paraíba do Sul passes: São Paulo, Rio de Janeiro and Minas Gerais. The National Water and Basic Sanitation Agency, responsible for managing Brazil’s water resources, was also part of the agreement.
Due to the drought, the Cantareira system operates in the “attention range”, with 39% of capacity, which raises concerns about the water supply in Greater São Paulo.
In the attention range, Sabesp can capture up to 31 m³/s, slightly below the normal capture volume of 33 m³/s, as a way of balancing the reservoirs of the Piracicaba, Capivari and Jundiaí rivers.
According to a statement released by the government of Rio de Janeiro, the measure aims to “help the Cantareira system”.
Paraíba do Sul
The Paraíba do Sul River basin extends over a total area of 61,500 km², with 14,000 km² in São Paulo, 20,700 km² in Minas Gerais and 26,900 km² in Rio de Janeiro.
The water from Paraíba do Sul is responsible for nourishing the Guandu system, which supplies the metropolitan region of Rio. In addition to this purpose, the river has other uses, such as irrigation and supplying the reservoir of 4 hydroelectric plants.
According to the government of Rio de Janeiro, authorization for São Paulo capture “does not compromise Rio de Janeiro’s supply logistics”.
The agreement determines that:
- the maximum annual volume of water that can be transferred from the reservoir of the Jaguari hydroelectric plant to the Atibainha reservoir, part of the Cantareira System, increases from 162 hm³ to up to 268.28 hm³ and a maximum collection flow of 8.5 m³/s;
- Sabesp is responsible for promoting the necessary solutions to mitigate possible impacts on water use resulting from the reduction in levels in the reservoirs of the Jaguari, Santa Branca, Paraibuna and Funil hydroelectric plants, caused by the removal of additional volume;
- The authorization is valid until December 31, 2026, but may be suspended if Cantareira recovers its level and reaches 60% of capacity.
History
According to ANA, authorization for São Paulo to expand abstraction in the Paraíba do Sul basin has already occurred in exceptional situations, such as in 2021 and 2025, years in which there was also a persistence of drought.
Just over 10 years ago, the States came to “face each other” over the need to capture water.
São Paulo proposed interconnecting the basins to guarantee supply to Cantareira, but Rio de Janeiro reacted, stating that the measure could compromise Rio de Janeiro’s water security.
In 2015, the Federal Supreme Court resolved the interstate crisis.
This text was originally published by Agência Brasil on June 27, 2026. The content is free for republication, citing the source, and was adapted to the standard of Poder360.
