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 11 to September 9, 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 in 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 Içá, Japurá, and main course of the Solimões rivers, characterized as “dry,” and the Jutaí, Juruá, and Tefé rivers, characterized as “tending toward dry”; while the Coari River basin was characterized as “tending toward wet.” The Javari and Purus river basins 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, Ji- Paraná, and Madeira river basins were categorized as normal. The Negro and Branco river basins continued to experience negative precipitation anomalies and were categorized 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 northeastern Pará were classified as “tending toward extremely dry,” and the basins in northwestern Pará were classified as “very dry.” On the right bank, the Curuá Una River basin was characterized by below-normal rainfall and classified as “tending toward extremely dry,” the Abacaxis and Tapajós basins as “very dry,” and the Iriri basin as “tending toward dry,” with cumulative precipitation ranging from 4 to 17 mm, confirming the scarcity of rainfall in this region; while the Teles Pires River basin showed a “tending toward rainy” condition. The Juruena and Xingu river basins were categorized as “normal.” The main course of the Amazon River within Brazilian territory experienced rainfall below climatological averages, categorized as tending toward extremely dry conditions. Negative precipitation anomalies are advancing from north to south across the basin, indicating the intensification of drought conditions in the left-bank tributaries of the Amazon basin—from the mountain range to the river’s mouth near Marajó Island; at this time, the spread of the drought over tributaries on the right bank within Brazilian territory is already dominant under the influence of the El Niño event that is taking hold in the Pacific Ocean.