Abstract
Human pressure on the water resources provided by natural wetlands has
intensified in Brazil due to an increase in agricultural land equipped
with irrigation. However, the amount of water stored in these areas, and
its contribution to aquifer recharge is unknown. The objectives of this
study were to determine the amount of water that can be retained in a
natural wetland surrounded by farmland, and to propose a model of
groundwater recharge. We used remote sensing techniques involving
Unmanned Aerial Vehicle (UAV) to map the area and highlight the wetland
internal morphology, using RGB orthomosaic and its respective digital
surface model. According to the topography of the study area three
compartments were defined. Compartment 1, corresponding to the external
border of the wetland, can store 313,121.00 m³ of water; compartment 2
and 3 can store 85,923.20 m³ and 17,952.10 m³, respectively. The 2D
inversion and a pseudo-3D model produced from Electrical Resistivity
Tomography (ETR) data were used to visualize the subsurface geologic
structure and hydrologic flow paths. Our results showed the direct
interactions between groundwater (GW) and surface water (SW) in the
center of the wetland (compartment 3), which constitutes the aquifer
recharge zone with vertical infiltration. As the depth increases,
infiltration and water flow deviates laterally in the southwest and
northeast direction. The wetland is characterized as an unconfined
aquifer that plays an important role in the hydrogeological dynamics of
the catchment. Remotely sensed very high-resolution images allied with
geophysical techniques allowed complete surface and subsurface imaging
and offered visual tools that contributed to understanding the
hydrodynamic of the wetland.
Keywords: hydrodynamics; water resources; tropical wetlands;
hydropedology; resistivity; aerial photogrammetry; water conservation;
aquic soil.