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 July 7 to August 5, 2026. In the Andean headwaters of the Marañon, Napo, Ucayali, and Amazon (PE) rivers, 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 main course of the Solimões River and the Japurá River basin, both in “very dry” conditions, experienced rainfall below the climatological average, while the Coari, Içá, Javari, Juruá, Jutaí, and Tefé river basins had rainfall slightly above the climatological average for the period; the Purus River basin, meanwhile, had rainfall close to the climatological average for the period. The Madeira River and its main tributaries recorded rainfall above the climatological average: the Aripuanã River basin was classified as very rainy, the Ji-Paraná River basin as tending toward very rainy, the Beni, Madeira, and Mamoré river basins as rainy, and the Guaporé River as tending toward rainy. The Negro and Branco river basins recorded an intensification of negative precipitation anomalies compared to the previous period, being categorized as “tending toward extremely dry” and “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 very dry, while those in northeastern Pará were classified as tending toward extremely dry. On the right bank, the Tapajós, Teles Pires, and Xingu river basins recorded positive precipitation anomalies; although significant for vegetation, the average 30-day accumulated precipitation ranged from 11 to 38 mm in these basins. In contrast, the Abacaxis and Iriri river basins were classified as “tending toward dry” and “dry,” respectively, with accumulated precipitation between 28 and 34 mm, indicating a shortage of rainfall in this region. The Curuá Una and Juruena river basins experienced rainfall close to the climatological norm for the period. The main course of the Amazon River in Brazilian territory experienced rainfall below the climatological average, categorized as “dry.” It is important to note that negative precipitation anomalies extend from north to south across the basin, indicating intensifying drought conditions in the left-bank tributaries of the Amazon Basin—from the mountain range to the river’s mouth near Marajó Island.