The relentless advance of global climate change poses an increasingly severe threat to Brazil’s groundwater reserves, according to a comprehensive study conducted by researchers at the University of São Paulo’s Institute of Geosciences and the National Institute for Space Research. The investigation, recently published in Environmental Monitoring and Assessment, reveals that shifting climate patterns and rising temperatures may drastically reduce the natural replenishment rates of the country’s vital aquifers by the end of the 21st century. Given that more than half of Brazil’s population depends either fully or partially on groundwater, these findings hold profound implications for the nation’s water security and ecosystem stability.
Groundwater, a critical component of the hydrological cycle, resides beneath the Earth’s surface in geological formations known as aquifers. This subterranean reservoir, fed primarily by the slow infiltration of rainwater through the soil, sustains wells, springs, rivers, and various ecosystems. In Brazil, groundwater serves as the primary or supplementary source of drinking water for over 112 million individuals, representing roughly 56% of the population. Consequently, any decline in aquifer recharge rates could have cascading socio-economic and environmental repercussions.
To quantitatively assess how climate change scenarios will impact groundwater availability, the researchers employed a sophisticated water balance model that integrates geospatial processing techniques with climate projection data derived from the Coupled Model Intercomparison Project Phase 6 (CMIP6). This state-of-the-art dataset, curated by the World Climate Research Program, synthesizes global climate model outputs to project future temperature, precipitation, runoff, and aquifer recharge trends from 2025 through 2100. Through this modeling approach, the study evaluated two primary greenhouse gas emission trajectories—one representing a moderate pathway and the other an extreme, pessimistic scenario.
The analysis uncovered a stark possibility: aquifer recharge in Brazil could face severe reductions, particularly in the Southeast and South regions. These areas are projected to become significantly drier under almost every modeled scenario, placing immense pressure on groundwater reserves. Professor Ricardo Hirata, lead author of the study, highlights that this geographic disparity will reshape water distribution nationwide as regional precipitation patterns evolve. The anticipated rise in average temperatures varies considerably across scenarios, ranging from approximately 1°C to nearly 3.7°C by century’s end.
Intriguingly, the study forecasts that shifts in rainfall characteristics could be as consequential as changes in precipitation volume. While some regions such as the North and parts of the eastern coast may experience average declines in rainfall, others including the South and the northeastern states of Ceará, Piauí, and Maranhão could see sporadic increases. However, this variability in precipitation timing and intensity does not translate into effective groundwater recharge. Intense, concentrated rainfall events promote surface runoff, which rapidly carries water away rather than allowing it sufficient time to infiltrate and replenish aquifers. Conversely, prolonged dry spells interrupt the steady percolation process necessary for aquifer sustenance.
The hydrological lag time inherent to aquifer recharge further complicates the picture. Water that penetrates the soil surface often requires several months to traverse the vadose zone and reach the saturated zone beneath. According to Hirata, “it can take two or three months for precipitation to move 10 to 15 meters through soil to the water table.” Brief, intense rainfall episodes thus fail to contribute meaningally to recharge, as water is unable to infiltrate deeply before evaporating or running off.
Quantitatively, the scenarios suggest that aquifer recharge could drop by as much as 666 millimeters annually in severely impacted regions. The Bauru-Caiuá Aquifer System in the Central-West region—the country’s largest continuous aquifer—faces a potential recharge reduction of nearly 28%. Other aquifers critical to the national water supply—including Guarani, Furnas, Serra Geral, Bambuí Cárstico, and Parecis—are also projected to incur significant recharge deficits, threatening the stability of water resources for millions.
Despite the mounting evidence for an emerging groundwater crisis, public policy and environmental discourse in Brazil have largely overlooked the subterranean dimension of water resources. Groundwater’s invisibility in climate change discussions belies its strategic importance: during recent drought periods, cities reliant on groundwater experienced far less water stress than those dependent on surface sources. Current data reveal that approximately 3 million drilled wells and 2 million dug wells extract between 550 to 600 cubic meters of water per second, predominantly for agriculture, industry, and residential use. Yet regulation and sustainable management of this essential resource remain nascent.
São Paulo presents a telling microcosm of this dynamic. While officially only 1% of the city’s public water supply comes from aquifers, an estimated 13,000 private wells pump around 11 cubic meters per second, supplying about 25% of water demand during crisis periods. This paradox underscores how private groundwater extraction, though often viewed critically, plays a crucial social role by alleviating pressure on municipal networks primarily serving lower-income populations.
Addressing the looming threat to Brazilian aquifers requires innovative and proactive measures. The study emphasizes managed aquifer recharge (MAR) as a promising solution. MAR encompasses various techniques designed to enhance the infiltration of rainwater or treated wastewater into aquifers, either through surface infiltration basins, small dams, or direct injection systems, such as those employed in Madrid. These engineered interventions help restore groundwater levels while leveraging the natural soil filtration capacity to purify recharged water, thereby safeguarding water quality.
Interestingly, urban infrastructure can inadvertently contribute to aquifer recharge. Isotope analyses from São Paulo’s central region indicate that nearly half the recharge in that area results from leaks in aging water supply and sewage networks. This phenomenon suggests that, while often considered a liability, network leakage may provide a net positive effect, replenishing underground stores and highlighting the complex interplay between urbanization and natural systems.
This pivotal research, funded by the São Paulo Research Foundation (FAPESP), is part of a broader initiative under the “SACRE – Integrated Solutions for Resilient Cities” thematic project. The study not only underscores the urgency of integrating groundwater considerations into climate resilience planning but also showcases the critical role of multidisciplinary collaboration in addressing one of Brazil’s most pressing environmental challenges.
Looking ahead, Professor Hirata’s ongoing commitment to groundwater stewardship has been recognized through prestigious awards, reflecting decades of pioneering work on this often-neglected water resource. His authoritative publication, “Groundwater and its Environmental and Socioeconomic Importance for Brazil,” further elucidates the myriad ways subterranean water governs ecological balance and human well-being.
Ultimately, Brazil stands at a crossroads where scientific insight must translate into concrete action to preserve its aquifers amidst rapidly changing climatic conditions. Without a decisive shift toward sustainable groundwater management—including broader implementation of managed recharge strategies and infrastructure modernization—the country risks water scarcity crises with far-reaching consequences for urban populations, agriculture, and natural ecosystems. The research serves as a clarion call for policymakers, scientists, and society alike to recalibrate their approach to groundwater—as a linchpin of resilience in an uncertain climate future.
Subject of Research: Climate change effects on groundwater recharge and sustainability in Brazil
Article Title: Climate change impacts on groundwater: a growing challenge for water resources sustainability in Brazil
News Publication Date: 21-Jun-2025
Web References:
- https://link.springer.com/article/10.1007/s10661-025-14235-8
- https://revistapesquisa.fapesp.br/en/aquifer-depletion-threatens-forests-and-rivers/
References:
- Coupled Model Intercomparison Project Phase 6 (CMIP6) climate data
- Hirata et al., “Groundwater and its Environmental and Socioeconomic Importance for Brazil”
Image Credits: IBGE School Geographic Atlas
Keywords: Groundwater, Hydrology, Climate change, Water supply, Precipitation, Sewage treatment
