Two decades of human- and climate-induced groundwater storage shifts in Brazil.

Brazil holds the world's largest reserves of renewable fresh water, yet recurrent water crises expose its growing vulnerability under extreme events. As the nation's groundwater demand increases, these reserves still are poorly monitored. Here, we present a data-driven spatiotemporal reconstruction of Brazil's groundwater behavior over the past two decades, integrating multi-satellite and in situ data into an artificial intelligence modeling framework. Results reveal groundwater variability, recharge, and emerging trends under climatological and anthropogenic stressors across the nation's ~8.5 million km2 of land. Brazil's mean groundwater recharge in aquifer outcrop zones during 2002-2023 was 223 ± 16 mm year-1, corresponding to ~12% of mean annual precipitation in those areas. When integrated over the analyzed outcrop extent, this corresponds to a natural recharge flux of ~1900 ± 136 km3 year-1. Persistent depletion or no recharge is observed in heavily exploited aquifers in eastern Brazil, further impacted by prolonged droughts and climate oscillations. Such aquifers present level declines mirroring patterns observed in intensively exploited aquifers in Bangladesh, India, Iran, and the US. As a world's major breadbasket, Brazil plays a vital role in global food security. Results presented here are therefore critical to the nation's sustaining agricultural productivity under increasing climate stress.