Monitoring groundwater storage in a fractured volcanic aquifer system

The use of groundwater resources is under increasing pressure to meet the demands of the society. Despite this, the understanding of its availability is still limited when compared to other water reserves. The aquifer studied was the volcanic Serra Geral Aquifer System (SASG) located in a humid subtropical region. This research aims to explore in a pioneering way the large-scale hydrogeological processes taking place at the SASG using a unique and complementary tool of intensive field monitoring, remote sensing data, and hydrological modeling. Results showed a fast response of groundwater levels to rainfall, with an average of 29 days of lag times. We also identified areas in the southern region of the basin with higher depletion rates, with GRACE results indicating a negative trend (- 57 mm year^-1) associated with a major recharge event that occurred in the region before the period monitored. Also, the interflow calculated using the MGB hydrological model showed that the flow within the limits between the soil and the volcanic rocks (different in hydraulic conductivity) varies spatially, influencing the baseflow of rivers as for slopes and soil capacity to store water.