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 August 18 to September 16, 2026. In the Andean headwaters, negative precipitation anomalies were concentrated in the Napo River basin, which was classified as “very dry,” and in the main stem of the Amazon River in Peruvian territory, which was classified as “dry.” The Marañon and Ucayali river basins were classified as “normal.” The following basins experienced rainfall below climatological norms: the Japurá and Juruá rivers, characterized as being in a dry condition, and the Içá and Purus rivers, characterized as tending toward dry conditions; meanwhile, the Coari River basin was in a rainy condition. The Javari, Jutaí, and Tefé river basins, as well as the main course of the Solimões River, recorded rainfall close to the climatological average for the period. With positive precipitation anomalies, the Mamoré River basin was classified as rainy; the Beni and Guaporé River basins were classified as tending toward rainy conditions; while the Aripuanã and Ji-Paraná River basins showed negative precipitation anomalies. The Madeira River basin was classified as normal. The Negro and Branco river basins continued to experience negative precipitation anomalies and were classified as tending toward dry and tending toward extremely dry conditions, respectively. 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 extremely dry,” and the basins in northeastern and northwestern Pará were classified as “very dry.” On the right bank, the Curuá Una and Tapajós river basins were characterized by rainfall below climatological norms and classified as “tending toward extremely dry,” the Abacaxis basin as “very dry,” and the Iriri basin as “dry,” with cumulative precipitation ranging from 3 to 24 mm, confirming the scarcity of rainfall in this region; while the Juruena, Teles Pires, and Xingu 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, contributing to the intensification of drought conditions 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.