Impacts of Interannual Rainfall Variability and Intensification of the
Hydrologic Cycle on Groundwater in a Micro-Watershed in the Amazon
Rainforest
Abstract
Climate change in the Amazon includes the intensification of the
hydrological cycle in association with the increase of extreme events.
This study aims to identify the impacts on groundwater (GW) within a
pristine micro-scale catchment in the Central Amazon related to the
observed alterations on hydrological cycle. Precipitation and GW levels
from seven piezometers distributed along a hydrological transect
covering three zones (lowland, slope and plateau) were collected for the
period 2001-2021. External (evapotranspiration, GW storage and climate
patterns) and computed (annual recharge) data were used to strengthen
the analyses. We identified a generalized growth trend in all
compartments (rainfall, evaporation and water table). There was a
heterogeneity in water table fluctuations and annual recharge, depending
on distance from creek channel and water depth. Surface processes
influenced shallows piezometers associated with rapid overflow and low
recharge. Conversely, deep piezometers involved slower processes related
to water movement, and were more representative of regional GW. Those
presented larger seasonal and inter-annual fluctuations, annual recharge
and positive trend than shallow piezometers. Besides, all piezometers
showed large inter-annual variations in recharge. The El Niño-Southern
Oscillation (ENSO) influenced GW level, recharge and storage: positive
phase contributed to lower all variables, with recovery in during
neutral and negative phase. The larger positive trends in the deeper
piezometers are a sign of the resilience of the Alter do Chão aquifer,
subject to anthropogenic pressure. As water table play a key-role in
shaping the structure and productivity of Amazon forests, further
hydro-ecological studies should be conducted to gather information about
the fate of GW-dependent Amazonian ecosystems.