Single-line diagram of the basins represented

Analysis of the Single-Line Diagram of the Shown Basins

The analysis of the unifilar diagram shows the distribution and classification of river basins according to the categorization of precipitation anomalies for the period between September 22 to October 21, 2026. In the Andean headwaters, rainfall was below normal: the Marañon and Ucayali river basins were classified as “tending toward extremely dry,” the Napo River basin as “tending toward very dry,” and the main course of the Amazon River in Peruvian territory as “dry.” Rainfall below the climatological average characterized the Juruá River basin (tending toward extremely dry conditions); the Javari, Jutaí, and Purus River basins (tending toward very dry conditions); the Içá, Tefé, and the main course of the Solimões River (dry); and the Coari River basin (tending toward dry conditions). The Japurá River basin experienced rainfall close to the climatological average for the period. The Ji-Paraná and Madeira river basins (in “very dry” conditions); the Aripuanã and Beni basins (tending toward “very dry”); and the Mamoré basin (dry) exhibited negative precipitation anomalies. The Guaporé River basin experienced rainfall close to the climatological average for the period. The Rio Branco river basin continued to experience significant negative precipitation anomalies and was classified as very dry. The Rio Negro basin recorded rainfall close to the climatological average for the period. On the left bank of the Amazon River in Brazilian territory, negative precipitation anomalies continued to predominate: the basins in northeastern Amazonas were classified as “tending toward very dry,” the basins in northwestern Pará State as “very dry,” and the basins in northeastern Pará State as “tending toward very dry.” On the right bank, rainfall was below climatological norms: the Curuá Una River basin was categorized as “tending toward extremely dry”; the Abacaxis, Iriri, and Teles Pires basins were categorized as “tending toward very dry”; and the Juruena, Tapajós, and Xingu basins were categorized as “dry.” The main course of the Amazon River within Brazilian territory continued to experience intensifying negative precipitation anomalies and was categorized as tending toward extremely dry conditions. Negative precipitation anomalies are distributed across the Amazon Basin, intensifying drought conditions across nearly all monitored basins. At this time, the advance of the drought is already evident from the Andean headwaters, the tributaries of the Solimões River, the Negro and Branco River basins, and the Eastern Amazon, with strong indications of the influence of the El Niño event established in the Pacific Ocean. Impacts on the region’s hydrological regime are already being observed, with major rivers remaining in a low-flow regime.