Drought and flood extremes on the Amazon River and in northeast Brazil, 1790-1900

Abstract Recent severe droughts, extreme floods, and increasing differences between seasonal high low flows on the Amazon River may represent a twenty-first-century increase in amplitude of hydrologic cycle over Basin. These precipitation streamflow changes have arisen from natural ocean–atmospheric variability, deforestation within drainage basin River, or anthropogenic climate change. Tree-ring reconstructions wet-season extremes, substantiated with historical accounts river levels northeast Brazil found Brazilian Digital Library, indicate that recent river-level extremes been equaled possibly exceeded during preinstrumental nineteenth century. The “Forgotten Drought” 1865 was lowest rainfall total reconstructed tree-rings eastern 1790 to 2016 appears one stream observed era according first-hand descriptions by Louis Agassiz, his colleague João Martins da Silva Coutinho, others. Heavy rains flooding are described most tree-ring-reconstructed wet including complete inundation “First Street” Santarem, Brazil, 1859 overtopping Bittencourt Bridge Manaus, 1892. tree-ring estimates observations flow anomalies not variability Significance Statement Proxy evidence for century floods droughts yet range hydroclimatic variability.