The Geophysical Limit of the SAGA Aquifer
The SAGA system, discovered by Francisco de Assis Matos de Abreu (UFPA) in September 2025, contains over 160 trillion cubic meters of groundwater. This volume exceeds that of the Guarani Aquifer by more than 30%, constituting a geophysically isolated water reserve from the surface cycle. Its existence has been confirmed by satellite gravimetry and high-resolution electromagnetic tomography data. The system functions as a reservoir with a critical buffer capacity for the Amazon basin, but recharge occurs exclusively through atmospheric flow known as the ‘flying river’, generated by forest transpiration.
The anthropogenic pressure on the system manifests in two directions: reduction of tree cover and increased water extraction for agricultural use. According to Earth System Models (ESMs) from CMIP6, the combined contribution of physiological CO2 and deforestation is responsible for 48% of the decline in surface humidity in the Amazon by 2100. This reduces the flow rate of the ‘flying river’, compromising the natural recharge of SAGA. The physical limit is not a political indicator, but an ecological threshold that can be verified: if recharge falls below 75% of the historical average for two consecutive years, the aquifer enters a phase of irreversible depletion.
Hydrological Pressure and Overcoming Mechanisms
The current rate of water extraction in the agricultural areas of northern Brazil is estimated at 14 billion cubic meters per year, with an average annual increase of 3.7% between 2015 and 2025. This pressure does not immediately translate into depletion of the SAGA aquifer, but alters the recharge dynamics. Satellite data show a 48% reduction in surface moisture during the SSP3-7.0 period, with a cumulative effect that results in a decrease in forest transpiration of approximately 22%. This decrease directly contracts the ‘flying river’ atmospheric flow, reducing the amount of vapor available for condensation and groundwater recharge.
The SAGA system is not isolated from the global climate. Marine thermal anomalies, such as those recorded in the equatorial Pacific during 2025-26, alter the patterns of atmospheric circulation that feed the Amazon. The El Niño event caused an increase in sea surface temperature up to +3°C compared to the historical average in the Mediterranean, with indirect effects on trans-equatorial humidity currents. This climate change further reduces the availability of atmospheric water, accelerating the process of exceeding the critical threshold.
The Ecosystemic Impact of Water Depletion
The impact of the loss of water recharge extends beyond the simple reduction of groundwater reserves. The SAGA system is closely connected to the surface hydrological cycle through underground rivers and infiltration zones. Its degradation compromises the entire water network of the Amazon basin, influencing primary productivity, migratory fish communities, and riparian habitats. The absence of groundwater recharge reduces the minimum flow in rivers during dry periods, with direct consequences for biodiversity.
According to Amazon Waters Alliance (2023), 17 species of migratory fish in the basin, including the Amazonian migratory catfish, depend on specific hydrological conditions for spawning and larval development. The loss of groundwater recharge alters flood and drought cycles, reducing the reproductive capacity of species by up to 50% in the long term. Furthermore, soil erosion increases by 42% when the underground water system is compromised, as tree roots lose the necessary hydraulic stability to maintain soil profiles.
The Intervention Window and the Critical Indicator
Analysis of satellite data suggests a limited operational window: if groundwater recharge falls below 75% of the historical average for two consecutive years, the SAGA system enters an irreversible depletion phase. The available time to intervene is estimated at less than 8 years starting from 2026, with a 91% probability that this threshold will be exceeded by 2034 if no structural mitigation measures are implemented. The cumulative effect of deforestation and climate anomalies reduces the resilience of the system, making complete recovery impossible even with reforestation interventions.
The critical parameter to monitor is the ratio between atmospheric ‘flying river’ flow and groundwater recharge. If this ratio falls below 0.75 for two consecutive years, the action threshold is triggered: activation of the natural credit mechanism must be blocked until the pre-critical condition is restored. The goal is not the financial value of the credits, but the physical conservation of the water resource.
According to the Amazon Waters Alliance, “Maintaining the integrity of the SAGA aquifer system is essential to ensure the continuity of ecosystem services at a regional scale. Its degradation is not only a water problem, but a collapse of the ecological resilience of the Amazon basin.”
Photo by Rajiv Bajaj on Unsplash
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