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 28 to August 26, 2026. In the Andean headwaters, negative precipitation anomalies were concentrated in the Napo River basin, which was classified as “extremely dry,” and in the main stem of the Amazon River in Peruvian territory, which was classified as “very dry.” The Ucayali River basin was classified as “rainy,” while the Marañón River basin was classified as “normal”. The main course of the Solimões River and the Coari, Içá, and Japurá river basins experienced rainfall below climatological norms, in contrast to the Purus River basin, which was characterized as tending toward wet conditions. The Javari, Juruá, Jutaí, and Tefé river basins experienced rainfall close to the climatological norm for the period. With positive precipitation anomalies, the Beni River basin was classified as very rainy; the Aripuanã and Mamoré basins as tending toward very rainy; the Ji-Paraná basin as rainy; and the Guaporé basin as tending toward very rainy. While the Madeira River basin was characterized as normal, the low climatological rainfall indices favor the occurrence of positive precipitation anomalies. The Negro and Branco river basins continued to experience negative precipitation anomalies and were classified as tending toward very dry and extremely dry conditions, 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 Abacaxis (tending toward very dry), Curuá Una (very dry), Tapajós (dry), and Xingu (tending toward dry) river basins were characterized by rainfall below climatological norms, with cumulative precipitation ranging from 5 to 13 mm, indicating a shortage of rainfall in this region. On the other hand, the Juruena and Teles Pires river basins were characterized as tending toward rainy conditions, although the average 30-day rainfall totals ranged from 7 to 11 mm. The Iriri River basin recorded rainfall close to the climatological average for the period. The main course of the Amazon River within Brazilian territory experienced rainfall below the climatological average, categorized as very dry. Negative precipitation anomalies are spreading in a north-south direction across the basin, indicating worsening 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 drought is already spreading to tributaries on the right bank within Brazilian territory.