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 15 to October 14, 2026. In the Andean headwaters, rainfall was below climatological norms: the Marañon and Ucayali river basins were classified as “tending toward extremely dry,” the main course of the Amazon River in Peruvian territory was classified as “tending toward very dry,” and the Napo River basin was classified as “dry.” Rainfall below the climatological average characterized the Juruá River basin (tending toward extremely dry conditions), the Purus River basin (very dry), the Javari River basin (tending toward very dry conditions), the Jutaí and Tefé River basins, the main course of the Solimões River (dry), and the Içá and Coari River basins (tending toward dry conditions). The Japurá River basin experienced rainfall close to the climatological average for the period. With positive precipitation anomalies, the Guaporé River basin was classified as “tending toward rainy”; while the Beni and Ji-Paraná river basins (classified as “very dry”), the Aripuanã and Madeira river basins (classified as “tending toward very dry”), and the Mamoré river basin (classified as “dry”) exhibited negative precipitation anomalies. The Branco and Negro river basins continued to experience negative precipitation anomalies and were categorized as very dry and tending toward 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 very dry conditions, while 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, Iriri, and Tapajós river basins were classified as “tending toward extremely dry,” the Teles Pires and Xingu basins as “tending toward very dry,” and the Abacaxis and Juruena River basins as “dry.” 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 distributed across the Amazon Basin, intensifying drought conditions in nearly all of the monitored basins. At this time, the onset and spread of the drought are already evident from the Andean headwaters, the tributaries of the Solimões River, the Negro and Branco River basins, and the Eastern Amazon, with strong indications of the influence of the El Niño event established in the Pacific Ocean; impacts on the region’s hydrological regime are already being observed.