Regional Groundwater Modeling of the Guarani Aquifer System

Roger D Gonçalves,Elias H Teramoto,Hung K Chang

doi:10.3390/w12092323

Roger D Gonçalves, Elias H Teramoto + Show 1 more

Open Access

https://doi.org/10.3390/w12092323

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Journal: Water	Publication Date: Aug 19, 2020
Citations: 13	License type: CC BY 4.0

Affiliation: Universidade Estadual Paulista (Unesp)

Abstract

The Guarani Aquifer System (GAS) is a strategic transboundary aquifer system shared by Brazil, Argentina, Paraguay and Uruguay. This article presents a groundwater flow model to assess the GAS system in terms of regional flow patterns, water balance and overall recharge. Despite the continental dimension of GAS, groundwater recharge is restricted to narrow outcrop zones. An important part is discharged into local watersheds, whereas a minor amount reaches the confined part. A three-dimensional finite element groundwater-flow model of the entire GAS system was constructed to obtain a better understanding of the prevailing flow dynamics and more reliable estimates of groundwater recharge. Our results show that recharge rates effectively contributing to the regional GAS water balance are only approximately 0.6 km3/year (about 4.9 mm/year). These rates are much smaller than previous estimates, including of deep recharge approximations commonly used for water resources management. Higher recharge rates were also not compatible with known 81Kr groundwater age estimates, as well as with calculated residence times using a particle tracking algorithm.

Highlights

The Guarani Aquifer System (GAS) is one of the largest groundwater reservoirs in the world, representing a transboundary system that encompasses four countries in Latin America: Argentina, Brazil, Uruguay and Paraguay (Figure 1)
Most groundwater recharge in the outcrop zones is discharged into local watersheds, with only minor amounts reaching the confined part of GAS to form deep recharge
Because of the strategic importance of the Guarani Aquifer System and the increased demand for water, more precise operational criteria should be defined for the sustainable use of GAS groundwater within the context of water management

Summary

Introduction

The Guarani Aquifer System (GAS) is one of the largest groundwater reservoirs in the world, representing a transboundary system that encompasses four countries in Latin America: Argentina, Brazil, Uruguay and Paraguay (Figure 1). The GAS comprises a sequence of sandy layers of Triassic-Jurassic age, deposited in continental, aeolian, fluvial and lagoon environments, above a regional erosional surface (dated to 250/Ma) and below an extensive layer of Cretaceous basalts (dated to 145–30/Ma) in the basins of Paraná (Brazil and Paraguay), Chaco-Paraná (Argentina) and North (Uruguay) [2]. Despite the continental scale of GAS, groundwater recharge is restricted to narrow outcrop zones, mainly along its western and eastern borders (Figure 2). Most groundwater recharge in the outcrop zones is discharged into local watersheds, with only minor amounts reaching the confined part of GAS to form deep recharge. Other studies [7,8] showed that deep recharge comprises only 10 to 15 mm/year, which represents a scant 1 to 2% of annual rainfall

Results

Discussion

Conclusion