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International study points to an increase of up to 60% in flow in floodable areas of the lower Amazon, with risk of impacts on fish, floodplain, erosion, riverside communities, and the ecological balance of the region
The flow of the Amazon has grown significantly in floodplains and tributaries of the lower river in recent decades, with an increase of up to 60% in areas such as Lago Grande do Curuai, in Santarém. The study, conducted by researchers from Brazil, France, and the United Kingdom, warns of impacts on biodiversity, riverside communities, and the floodplain forest.
Amazon flow increases more in floodable areas
The Amazon River, recognized as the longest and most voluminous on the planet, is undergoing increasingly intense hydrological changes.
The research analyzed data from 1970 to 2023 and identified a significant increase in water flow in the floodplains of the lower Amazon.
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The survey was led by hydrologist Alice Fassoni de Andrade, from the University of Brasília. The team used satellite images, water level measurements, and computational models to reconstruct the river’s behavior in four large plains between Manaus and Santarém.
Between 2005 and 2023, the average flow of the Amazon increased by 4.7% compared to the previous period. In some regions, however, the increase was much greater.
In Lago Grande do Curuai, in Santarém, the growth reached 60%, a percentage considered surprising by the researchers.
River has volume comparable to the largest in the world
With about 6,900 kilometers in length, from the Peruvian Andes to the Atlantic Ocean, the Amazon forms the largest river basin on the planet.
In Óbidos, in Pará, approximately 800 kilometers from the mouth, the average flow reaches 160 thousand cubic meters per second.
This volume is comparable to the sum of the seven largest rivers in the world. During part of the year, the waters advance over extensive floodplain areas, bringing sediments and essential nutrients to the functioning of the Amazonian ecosystems.
In recent years, extremes have become more frequent. The historic floods of 2009 and 2021 caused the flow in areas like the Parintins plain to exceed 40,000 cubic meters per second, almost matching the average flow of the Congo River in Africa.
Technology helped measure changes in the lower Amazon
Measuring the flow of a river with the dimensions of the Amazon is a complex task. The National Water and Basic Sanitation Agency continuously monitors the river level at different stations, while the Geological Service of Brazil conducts direct measurements a few times a year.
These measurements use ultrasound equipment to calculate the water velocity at different depths. From this data, scientists have calibrated models capable of estimating water flow over time.
The team also developed a detailed hydrodynamic model of a 1,100-kilometer stretch of the Amazon.
The analyzed area covers almost 40,000 square kilometers. In expeditions carried out in 2022, researchers measured almost 17,000 cubic meters per second in the Lago Grande do Curuai, a value similar to that of the Mississippi River.
Floodplain may feel greater effects than the main river
Researchers observed that small changes in the flow of the main river can generate much larger changes in the floodplains.
This occurs because these areas are shallow and react quickly to small rises in water level.
With more water circulating, the speed of runoff increases. This process can intensify erosion, sediment transport, and changes in floodplain ecosystems, which depend on the balance between flood, drought, vegetation, and aquatic species.
Ecologist Leandro Castello warns that fish adapted to calmer waters, such as pirarucu, tucunaré, and acará-açu, may face difficulties under the new hydrological conditions. Floodplain vegetation also plays an important role in reducing the strength of currents.
Aquatic trees and plants help reduce the impacts of floods on riverside communities. Researchers warn, however, that few areas of these forests are protected by conservation units.
The results reinforce projections from the Intergovernmental Panel on Climate Change, which indicate an intensification of droughts and floods in the Amazon associated with global warming.
Scientists advocate for more monitoring of floodplains and public policies to protect the floodplain and the populations that depend on the river.
This article was prepared based on information from a study conducted by researchers from Brazil, France, and the United Kingdom, with data, numbers, and statements preserved as per the consulted material.
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