It flows north for about 320 kilometres (200 mi) before emptying into the Baía de São José to the south of the state capital.

[5] The lower reaches of the river flow through the 1,535,310 hectares (3,793,800 acres) Upaon-Açu/Miritiba/Alto Preguiças Environmental Protection Area, created in 1992.

In September 2015 the committee meet to discuss the proposal for a state Rio Preto and Riacho Estrela Environmental / Biological Reserve.

[2] A study published in 2006 found that human activity in the municipality of Chapadinha had caused serious problems, particularly projects to produce soybeans.

State Representative Bira do Pindaré reported on the hearing to the legislature, including the finding that a company was extracting sand illegally in the municipality of Presidente Juscelino.