Water insecurity in Brazil isn’t just about declining rainfall. Researchers describe it as the weakening of natural climate regulation processes, a gradual shift with potentially far-reaching consequences.
Research from the University of São Paulo estimates that the Amazon deforestation accounts for roughly 74.5 per cent of rainfall reduction and 16.5 per cent temperature increase during the dry season.
The Amazon plays a central role in South America’s water cycle. Trees draw moisture from the soil and release it into the atmosphere, generating currents of humid air often described as “flying rivers”.
These invisible air currents carry rainfall far beyond the forest, sustaining agricultural regions, reservoirs, and major urban centres. For example, a large percentage of rainfall supplying São Paulo’s Cantareira water system depends on moisture originating in the Amazon.
For many Brazilians, these atmospheric water currents are invisible, but their effects shape when crops grow, reservoirs refill and whether rivers remain navigable.
According to Brazil’s National Water and Basic Sanitation Agency (ANA), on 30 January, the Cantareira system was reported to be operating at 22 per cent.
As forests shrink, scientists warn that this moisture recycling process weakens. Reduced tree cover means less moisture in the air, rainfall becomes more erratic, and rivers flows grow increasingly unstable. Some regions face prolonged drought, while others experience intense rainfall over shorter periods.
Researchers say these extremes aren’t isolated anomalies but signs of mounting ecological stress. Drier soil reduces groundwater recharge, while rivers respond more sharply to both drought and heavy rainfall.
Large-scale climate events, such as El Niño, La Niña, and warm conditions in the North Tropical Atlantic (NTA) only add to the strain, triggering floods or droughts that cascade through river systems and aquifers.
Along the Amazon’s waterways, communities are already feeling the consequences. Fish stocks are declining, drinking water is less unreliable, and river transport routes are disrupted during dry seasons, isolating villages and restricting access to food and essential supplies.
Brazil’s overlooked water source
While the Amazon often dominates headlines, scientists emphasise that the Cerrado plays an equally critical role in maintaining Brazil’s water balance. Covering roughly a quarter of the country, the biome feeds major river systems, including the São Francisco, Paraná and Tocantins.
Gatti stressed that the Cerrado biome is fundamental in sustaining Brazil’s water systems and river basins: “The Cerrado contains around 80 per cent of Brazil’s hydrographic basins. It functions like an upside-down forest, concentrated in deep root systems. These roots allow rainfall to infiltrate gradually and recharge groundwater reserves.
“When deforestation occurs, the natural buffering system disappears. Rainwater is no longer absorbed properly. The soil becomes exposed and water runs off instead of penetrating the ground.”
For generations, rural and Indigenous communities have depended on these groundwater-fed streams for farming, fishing and cultural practices tied to seasonal water cycles.
But the Cerrado is disappearing fast. Soy cultivation, cattle ranching, and large-scale monoculture have replaced vast areas of native vegetation. Shallow-rooted crops capture less water, reduce groundwater recharge and accelerate soil erosion. Streams that once supported rural farming communities are shrinking or disappearing altogether.
Expanding industrial pressure
Brazil’s agricultural sector has become a pillar of economic growth, but it has also intensified pressure on water resources.
Demand for irrigation is increasing, while fertilisers and pesticides frequently run off into river systems polluting the water, soil and wildlife. Globally, agriculture accounts for 70 per cent of freshwater use, a pattern reflected in Brazil’s agribusiness expansion.
Gatti emphasised the role of international commodity demand in sustaining deforestation: “It’s hypocritical to blame Brazil alone for failing to combat deforestation while countries such as the United States, those in Europe, China, the UK, and others continue to buy products linked to deforestation.
“If they stopped buying timber, meat, soy, corn and minerals produced in deforested areas, deforestation could end very quickly.”
Fires introduce another layer of risk. Burned landscapes absorb and release water unevenly, increasing flood risk during rainy periods and worsening drought conditions during dry months. Repeated fires are altering forest composition in parts of the Amazon, potentially weakening rainfall generation over time.
Gatti said: “In 2024, the Amazon recorded its highest carbon emissions on record due largely to fires. Brazil’s ministry of science, technology and innovation (MCTI) treats emissions from Amazon fires as net zero in its official methodology. Yet fires represent the Amazon’s largest source of carbon emissions.”
In 2024, fires burned across 3.3 million hectares of the Amazon, releasing roughly 791 million tons of CO₂, about what Germany emits in a year. For the first time, forest degradation from fire was overtaken deforestation as the Amazon’s top carbon culprit.
Mining operations further strain water systems. Rivers courses are sometimes diverted, forests cleared and waterways contaminated with chemicals, reducing the amount of safe freshwater available for drinking, fisheries, agriculture, transport and ecosystems.
Scientists warn that if deforestation and ecosystem degradation continue, river flows and rainfall patterns could become progressively less predictable, threatening agriculture and urban water supplies.
The United Nations University Institute for Water, Environment and Health (UNU-INWEH) describes this emerging challenge as “water bankruptcy”, a situation in which freshwater is consumed faster than nature can replenish it.
Experts warn that unequal access to water could deepen social inequality, fuel migration and increase the risk of conflict in vulnerable regions.
Political
Despite mounting scientific evidence, water scarcity is still widely perceived as a distant or regional problem in a country historically defined by abundance.
At the same time, policy decisions are reshaping the rivers themselves. Signed by Brazil’s President Luiz Inácio Lula da Silva in August 2025, Decree 12,600/2025 added the Tapajós, and Tocantins rivers (state of Pará), as well as the Madeira river (state of Amazonas) to Brazil’s privatisation pipeline to expand shipping along the Northern Arc.
Hydrologists and riverside communities warn that dredging riverbeds and removing rock to keep these routes open for larger cargo vessels could disrupt sediment movement and seasonal flood patterns.
In a basin already strained by intensifying droughts, these changes could further weaken water security for ecosystems and the people who depend on them.
Getirana highlighted that Brazil’s emerging water crisis is rooted in longstanding political and cultural practices: “Many of Brazil’s political and economic decisions have been based on the idea that it’s a water-rich country.
“Poor political decisions that resulted in negative impacts on the environment and water availability are not party- or ideology-related. It’s the culture in the country. It’s been happening for decades, maybe centuries, regardless who’s in power. Poor water management is rooted in Brazil’s culture.
“A political change needs, first, a mindset shift in the Brazilian population. Maybe a way to change that mindset is by demonstrating how poor management is impacting their livelihoods and finances.”
Gatti also warned that in Brazil, scientific research is often overlooked in policy development: “Scientific evidence isn’t reaching decision-makers. Promises of zero deforestation by 2030 risk being too late because parts of the Amazon may already be approaching ecological tipping points.
“Although Brazil has experienced political changes in leadership, structural land-use policies driving deforestation have remained largely unchanged.”
Recovery
Despite growing concern, some scientists emphasise that recovery remains possible.
Gatti explained that several measures could make a considerable difference to Brazil’s water security: “Zero deforestation across the entire country by 2027, not just in the Amazon, is essential to stabilise rainfall and water systems.
“Reducing cattle herd size, establishing limits on large monoculture farming and requiring forest restoration within agricultural landscapes would help reduce environmental pressure and water instability.
“Expanding agroforestry systems on a large scale could help restore ecological balance while maintaining agricultural productivity.”
Getirana argued that reforming water governance should be the first step in restoring Brazil’s water stability: “I believe that reforming water governance would be the baseline for other measures, such as restoring degraded land and tackling climate mitigation. Additionally, policies that prevent water from being polluted could have almost immediate impacts.”
Some researchers are examining whether recognition of rivers as living entities could provide stronger environmental protection. A project led by the University of Leeds is exploring how such legal frameworks might help prevent pollution, deforestation and industrial over-exploitation.
For communities along the Rio Negro and throughout Brazil’s interior, the crisis is already deeply personal. Rivers are less predictable, rainfall patterns are shifting and water quality is declining. Their daily experiences reflect a broader reality: Brazil’s water future depends on the survival of the ecosystems that sustain it.
Protecting Brazil’s forests may ultimately determine not only the country’s environmental future, but the stability of water systems that millions of people depend on every day.
This Author
Monica Piccinini is a regular contributor to The Ecologist and a freelance writer focused on environmental, health and human rights issues.