The Rio Grande River Basin, with its tributaries, form part of the municipality, with the ""Rio Grande arm"" of the Billings Reservoir and Dam which is its most significant geographical feature, covering a total of 127 square kilometres (49 sq mi). It is named after Asa White Kenney Billings, the United States hydroelectric engineer who was instrumental in building it. The reservoir supplies about 1.8 million people, and also is used for fishing and swimming. In addition to Rio Grande da Serra and Sao Paulo, the Billings sub-basin includes Diadema, Ribeirao Pires, Santo Andre, and Sao Bernardo do Campo. Besides the Rio Grande and Billings Reservoir and dam, the municipality has a lot of streams and creeks, such as the streams of Figueira, Cloro, and Piolzinho.