Study Reveals Insufficient Rainwater to Sustain Guarani Aquifer Amid Drought and Overuse

A study by São Paulo State University (UNESP) in Brazil highlights a critical issue: rainwater cannot replenish the Guarani Aquifer due to overuse and drought. This aquifer is vital for water supply in the region, supporting urban areas, agriculture, and tourism.

Published in the journal Isotopes in Environmental and Health Studies, the research reveals that the amount of rainwater collected is less than what is withdrawn for various human activities. The Guarani Aquifer, spanning Brazil, Paraguay, Uruguay, and Argentina, is the world’s largest cross-border groundwater reservoir, covering about 1.19 million square kilometers. While it stores around 30,000 cubic kilometers of water, over-extraction poses a threat to its sustainability.

The study focuses on groundwater levels, rainfall, and isotopic analysis of different water sources. It found that rainwater contributes only 20% to spring water discharge, indicating that the aquifer primarily depends on older groundwater. The researchers identified a concerning trend: as rainfall decreases and evaporation rises, the aquifer’s water level is falling.

São Paulo state consumes approximately 80% of the water from the Guarani Aquifer. There is urgent need for management strategies to ensure sustainable use, especially given the context of climate change and severe droughts experienced from 2014 to 2021.

Researchers emphasize that understanding how the aquifer is replenished is key. They propose ongoing monitoring and management to ensure the aquifer can continue to support the population, which relies on its resources.