Portuguese 
The low water season of the Rio Negro may drive levels in Manaus to a range between 12.31 and 16.50 meters at the peak of the 2026 drought, according to scenarios released by Brazil’s Geological Service.
The projection uses historical series and different rates of descent observed in previous droughts. It is not a single predicted mark but a range conditioned to the river’s behavior in the coming weeks.
On August 31, the Manaus station recorded 24.19 meters. The calculation tracks the decrease until the end of October, a period used as a reference for the most severe scenarios.
If the drop follows the 2023 pattern, the estimate will reach 13.37 meters. A similar behavior to that of 2024 would lead to 16.32 meters, which is still considered low for Manaus.
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According to the alert published by the SGB, a scenario close to 2015 and in the lowest percentile could drop the river below 13 meters by October 31.
The institute also updated estimates for Tabatinga, on the Solimões River, and Itacoatiara, in Amazonas. The three stations help monitor how the low water wave advances through the basin.
Scenarios measure different rates of descent
Hydrological predictions do not function as a ruler that points to the exact level for October today. Rain, contributions from tributaries, and flow rates alter the trajectory daily.
Thus, technicians compare 2026 with years of known behavior. Each reference represents a curve of descent and generates a possible level for that future date.
The percentile indicates the position of a rate within the historical series. A low value describes conditions observed near the most severe extreme, not a certainty that it will occur.
In Tabatinga, the estimated interval ranges from 31 centimeters below to 1.78 meters. The local emergency level is set at 1.50 meters, placing some scenarios below this limit.
The city’s analysis uses data until the first half of October, when the flood usually begins in the region. This cycle occurs before the observed point in Manaus.
For Itacoatiara, the calculated range on October 31 goes from 57 centimeters to 3.32 meters. The method accounted for rates of descent recorded in years with significant El Niño impact.
At the end of August, Tabatinga was at 2.94 meters and Itacoatiara at 10.06 meters. These values formed the base observed to project trajectories.
A subsequent report indicated continuation of the low water season. Manaus dropped 85 centimeters in a week and 14 centimeters in the last 24 hours, reaching 24.04 meters during that monitoring.
Most stations remained close to normal or median for the period. The clearest exception was the Rio Branco Basin in Roraima, which was below the expected range.
These differences remind us that the Amazon does not lower simultaneously. Distance, tributaries, and local rain cause the low water to appear at different rates along the rivers.
Low water levels impact navigation, supply, and communities
The level in Manaus does not solely indicate a landscape; it interferes with the draft available, vessel approaches, and the connections of communities that rely on rivers.
When the channel becomes shallow, boats may reduce load or change routes. Slower trips and additional transfers raise the cost of transporting food, fuel, and other products.
Ports and terminals monitor the same information to organize operations. Inadequate safety margins increase the risk of grounding and limit the use of larger vessels.
In communities, the retreat of water extends the distance between homes and boats. Makeshift bridges and mud areas become part of daily life, impacting education, health, and commerce.
We see the photograph of the exposed riverbed, but the daily change is the data that guides decisions. A drop of several centimeters per day accumulates meters over weeks.
Forecasts help governments and businesses anticipate stock, transportation, and services. They do not eliminate uncertainty, but they provide time to prepare responses rather than react only at a critical level.
The SGB uses data from the National Hydrometeorological Network, overseen by the National Water and Basic Sanitation Agency and operated with partners. The continuity of measurements supports each update.
Models also carry uncertainties, as the service itself indicates. New rains or different descents from historical references can shift the final level inside or outside the range.
In addition to the main gauge, satellite images and measurements from other stations help to form the overall picture. A single point does not describe all the channels used by boats and communities.
Contingency plans can set levels to initiate gradual actions. Anticipating water, food, and fuel costs less than transporting urgent volumes when the draft already limits navigation.
I see the released range as a preparation tool, not as a headline of confirmed catastrophe. Its utility lies in demonstrating the size of the risk while there is still time to mitigate impacts.
Therefore, the number of 12.31 meters should not be treated as a confirmed destination. It represents the lower limit of a set of analyzed possibilities.
The range up to 16.50 meters still describes a low water season that deserves monitoring. Even less extreme scenarios can restrict channels and reach shallow areas before affecting the main gauge.
The coming weeks will reveal which descent curve is closer to 2026. Frequent bulletins will allow projections to be narrowed as the peak of the dry season approaches.
For Manaus and the interior, following the river is about monitoring the region’s transport infrastructure. Water defines routes where no equivalent road alternative exists.
Does your city already feel the effects of low water season in the Amazon rivers? Share in the comments.
