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 1 to September 30, 2026. In the Andean headwaters, negative precipitation anomalies were concentrated in the Marañon and Ucayali river basins, which are experiencing conditions tending toward dry, and in the Napo basin, which is in a dry condition. The main course of the Amazon River within Peruvian territory is in normal conditions. Precipitation below climatological norms characterized the Japurá and Juruá river basins, which were in a dry condition, and the Içá, Purus, and Tefé river basins, which were in a condition tending toward dry. The Coari (tending toward very wet) and Javari (tending toward wet) river basins exhibited positive precipitation anomalies. The Jutaí River and the main course of the Solimões River experienced rainfall close to the climatological average for the period. With positive precipitation anomalies, the Guaporé River basin was characterized as tending toward wet conditions, while the Aripuanã, Beni, and Ji-Paraná river basins exhibited negative precipitation anomalies. The Madeira and Mamoré river basins were categorized as normal. The Branco and Negro river basins continued to experience negative precipitation anomalies and were categorized as tending toward extremely dry and 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 in the northeastern and northwestern parts of the state of Pará were classified as “very dry.” On the right bank, rainfall was below climatological norms: the Curuá Una River basin (tending toward extremely dry conditions), Tapajós (very dry), Iriri (tending toward very dry), Abacaxis (dry), and Xingu (tending toward dry), while the Juruena and Teles Pires river basins were classified as normal. The main course of the Amazon River within Brazilian territory experienced rainfall below the climatological average and was classified as very dry. Negative precipitation anomalies are concentrated over the eastern Amazon, causing drought conditions to intensify in the left-bank tributaries of the basin. At this time, the spread of drought to right-bank tributaries in Brazilian territory is already predominant under the influence of the established El Niño event in the Pacific Ocean.