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 25 to September 23, 2026. In the Andean headwaters, negative precipitation anomalies were concentrated in the Napo River basin, which was experiencing drought conditions, and in the main stem of the Amazon River in Peruvian territory, which was showing a tendency toward drought. The Marañon and Ucayali river basins were classified as normal. Rainfall was below climatological norms in the Juruá (tending toward very dry conditions), Japurá, Jutaí, Purus, and Tefé river basins, as well as the main course of the Solimões River (dry conditions), and the Içá River basin, which was characterized as tending toward dry conditions, while the Coari River basin was classified as rainy. The Javari River basin recorded rainfall close to the climatological average for the period. With positive precipitation anomalies, the Guaporé and Mamoré river basins were classified as “tending toward rainy,” while the Aripuanã, Beni, and Ji-Paraná river basins showed negative precipitation anomalies. The Madeira River basin was categorized as normal. The Negro and Branco river basins continued to experience negative precipitation anomalies and were categorized as tending toward very dry and tending toward extremely dry, 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 conditions, and the basins in the northeast and northwest 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), Abacaxis (tending toward very dry), Iriri (dry), and Xingu (tending toward dry), with cumulative precipitation between 4 and 30 mm, confirming the scarcity of rainfall in the region; while the Juruena and Teles Pires river basins were categorized as normal. The main course of the Amazon River within Brazilian territory experienced rainfall below climatological averages and was categorized as tending toward extremely dry conditions. 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.