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 8 to October 7, 2026. In the Andean headwaters, rainfall was below normal: the Marañon and Ucayali river basins were in very dry conditions, while the main course of the Amazon River in Peruvian territory and the Napo River basin were in dry conditions. Rainfall below the climatological average characterized the Juruá River basin as very dry, the Purus River basin as tending toward very dry, and the Içá, Japurá, Javari, Jutaí, and Tefé river basins, as well as the main course of the Solimões River, as tending toward dry. The Coari River basin experienced rainfall close to the climatological average for the period. With positive precipitation anomalies, the Guaporé River basin was classified as rainy; meanwhile, the Beni and Ji-Paraná river basins (tending toward very dry conditions), the Madeira River basin (dry), and the Aripuanã River basin (tending toward dry conditions) exhibited negative precipitation anomalies. The Mamoré River basin was categorized as normal. The Branco and Negro river basins continued to experience negative precipitation anomalies and were categorized as tending toward extremely dry and tending toward dry, respectively. On the left bank of the Amazon River in Brazilian territory, negative precipitation anomalies continued to predominate: the basins in northeastern Amazonas and northwestern Pará were classified as “tending toward very dry,” and the basins in northeastern Pará were classified as “very dry.” On the right bank, rainfall was below climatological norms: the Curuá Una River basin was classified as “tending toward extremely dry,” the Iriri and Tapajós basins as “very dry,” the Abacaxis, Teles Pires, and Xingu basins as “dry,” and the Juruena River basin as “tending toward dry.” The main course of the Amazon River within Brazilian territory experienced rainfall below the climatological average and was categorized as “very dry.” Negative precipitation anomalies are distributed across the Amazon Basin, intensifying drought conditions across much of the monitored basins. At this time, the establishment and spread of the drought are already evident from the Andean headwaters, the tributaries of the Solimões River, the Branco River basin, and the Eastern Amazon, with strong indications of the influence of the El Niño event established in the Pacific Ocean.