Represa Guarapiranga is a large urban reservoir located in the southern area of the city of São Paulo, in the state of São Paulo, Brazil. Originally constructed in 1906 by the São Paulo Tramway, Light and Power Company to support electrical energy production at the Parnaíba Hydroelectric generating plant, the reservoir began serving as a potable water source in 1928 and today supplies water to approximately 3.5 million people in the Greater São Paulo metropolitan region. The reservoir is fed primarily by the Rio Guarapiranga along with numerous smaller rivers and streams that traverse the municipalities of São Paulo, Itapecerica da Serra, and Embu-Guaçu, draining a catchment area of 631 km² (244 sq mi). With a maximum length of 19.17 kilometers (nearly 12 miles), Guarapiranga is one of the most significant bodies of water in the metropolitan region and supports a variety of recreational activities, including fishing, water sports, and boating. Despite its urban setting and the pressures that come with it, the reservoir remains a productive and popular fishing destination for local anglers.