# Tietê River environmental and flooding incidents > Live situation record from CLSTR: https://clstr.news/situations/tiet-river-environmental-and-flooding-incidents > Updated: 2026-09-19T11:00:00.000Z. Sources: 4. Developments: 2. The Tietê River in São Paulo has experienced significant environmental and structural issues due to water fluctuations and heavy rainfall. In early September, a ‘black water’ phenomenon near Salto resulted in dead fish being found in the river. Local authorities and dam management agencies debated whether the dark coloration was caused by floodgate operations displacing sludge and sewage or by increased flow from recent rains stirring up organic matter on the riverbed. By mid-September, heavy rainfall caused the river to overflow at rates exceeding twice its normal maximum limit. This flooding impacted various neighborhoods in the São Paulo metropolitan area and the interior. In Salto, floodwaters deposited large quantities of debris and plastic waste into the historic Lavras Hydroelectric Plant, prompting concerns over both environmental pollution and the preservation of the early 20th-century site. Observers have suggested the intensity of these events may indicate an intensification of flooding due to climate change. ## Timeline ### 2026-09-19: Rio Tietê flooding causes urban damage and pollution in São Paulo Flooding of the Tietê River in São Paulo has caused severe urban inundation and deposited significant amounts of waste into the historic Lavras Hydroelectric Plant. 2 sources. https://clstr.news/cluster/rio-tiet-flooding-causes-urban-damage-and-pollution-in-so-paulo ### 2026-09-03: Rio Tietê dead fish found in Salto after black water phenomenon Dead fish were discovered in the Tietê River near Salto, Brazil, after a ‘black water’ phenomenon caused by displaced organic matter and sewage following recent rains. 2 sources. https://clstr.news/cluster/rio-tiet-dead-fish-found-in-salto-after-black-water-phenomenon --- Cite as: Tietê River environmental and flooding incidents. CLSTR, https://clstr.news/situations/tiet-river-environmental-and-flooding-incidents