Abstract

The increasing frequency of extreme climate events in the Amazon has affected several components of the hydrological cycle. This study evaluates the impacts of alterations on the hydrological cycle on groundwater (GW) in a pristine micro-scale catchment in Alter do Ch & atilde;o Aquifer, in Central Amazonia. Precipitation and Groundwater levels (GWL) distributed along a hydrological transect covering three zones (plateau, slope and lowland) were measured for 21 years (2001-2021). Measured variables (evapotranspiration, GW storage and climate patterns) and computed annual recharge were analysed. Results indicate an overall increasing trend in rainfall, evapotranspiration and GWL, with marked spatial heterogeneity. Shallow GW was strongly influenced by surface processes, showing rapid responses and lower recharge, while deep GW exhibited slower dynamics, larger seasonal and inter-annual fluctuations, higher recharge and more pronounced positive trends. ENSO significantly influenced GWL, recharge and storage.