Modeling Groundwater Recharge in the Guarani Aquifer's Recharge Zone: Integrating SWAT+ with Multi-Scale Remote Sensing and Field Data

Abstract Submission: The Guarani Aquifer System (GAS), one of the world's largest groundwater reservoirs, spreads Argentina, Brazil, Paraguay, and Uruguay, supplying freshwater to over 15 million people. Despite its vast potential, 80% of the reservoir's water is confined, and the small recharge areas face challenges such as over-extraction, contamination from agricultural and industrial activities, and climate change impacts. This study focuses on modeling water balance dynamics and recharge rates in a critical recharge area for the GAS, using the latest version of the Soil and Water Assessment Tool (SWAT+) model. SWAT+ model was implemented in the Ibicuí River basin (42,650 km²) to evaluate the spatial and temporal variability of groundwater recharge, simulating hydrological processes and interactions within the watershed. Model outputs were validated comparing with data from the Gravity Recovery and Climate Experiment (GRACE) satellite and 19 field-monitored piezometers from the Integrated Groundwater Monitoring Network (RIMAS). The integration of GRACE satellite data - offering a large-scale perspective on water storage changes - with localized piezometer measurements significantly enhances the model’s ability to capture groundwater fluctuations. This combined approach provides valuable insights into recharge mechanisms, the effects of land use changes, and potential vulnerabilities to groundwater depletion due to climate change and human activities. The findings could contribute critical data to guide the sustainable management of the GAS recharge areas, informing policies aimed at preserving this transboundary water resource for sustainable long-term uses.

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