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 4 to September 2, 2026. In the Andean headwaters, negative precipitation anomalies were concentrated in the Napo River basin, which was classified as “tending toward extremely dry,” and in the main stem of the Amazon River within Peruvian territory, which was classified as “tending toward very dry.” The Ucayali River basin was classified as “tending toward wet,” while the Marañon River basin remained in “normal” conditions. The following basins experienced rainfall below climatological norms: the Coari River (tending toward extremely dry conditions), the Japurá and Tefé rivers (very dry conditions), the Içá, Javari, and the main course of the Solimões River (dry conditions), and the Jutaí River (tending toward dry conditions). The Purus River basin recorded rainfall close to the climatological average for the period. With positive precipitation anomalies, the Beni River basin was classified as tending toward very wet, and the Mamoré River basin as wet. The Aripuanã, Guaporé, and Ji- Paraná river basins were categorized as normal, while the Madeira River basin was characterized as tending toward dry conditions. The Negro and Branco river basins continued to experience negative precipitation anomalies and were classified as “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 and northwestern Pará were classified as tending toward extremely dry conditions, and the basins in northeastern Pará were classified as very dry. On the right bank, the Curuá Una (tending toward extremely dry), Abacaxis, and Tapajós (very dry) river basins, Iriri and Xingu (dry), and Juruena and Teles Pires (tending toward dry), with cumulative precipitation between 4 and 11 mm, indicating a shortage of rainfall in this region. 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 advancing rapidly from north to south across the basin, indicating intensifying drought conditions in the tributaries on the left bank of the Amazon basin, from the mountain range to the river’s mouth near Marajó Island. At this time, the advance of the drought into tributaries on the right bank within Brazilian territory is already noticeable.