ABSTRACT
The Guarani Aquifer System (the SAG based on Portuguese abbreviation) is one of the largest aquifer systems in the world (second after the Nubian Sandstone Aquifer). It is a transboundary aquifer, since it extends to four countries including Brazil, Argentina, Uruguay, and Paraguay (Araujo et al., 1999). In São Paulo state (Brazil), the Guarani system comprises the Botucatu and Piramboia aquifers (Fig. 10.1), which are confined by the underlying Passa Dois and Rio do Rastro aquitards and the overlying Serra Geral Formation. The aquifer is dipping towards the west, e.g., towards the Paraná River (Fig. 10.2). The Piramboia Formation consists of silty-clay sandstones of aeolian and fluvial origin; the Botucato Formation is composed of well-sorted sandstones of aeolian origin with dominating quartz plus feldspar and micas (Hirata et al., 2011). Cation exchange capacity is around 1 meq/100 g. Average value of hydraulic conductivity of the most productive Botucato Aquifer is 1.5 × 10−4 m s−1 with resulting average transmissivity of 3.9 × 10−3 m2 s−1. Calculated flow velocities are low due to low hydraulic gradients, in the order of tens of meters per year (Sracek and Hirata, 2002). Flow in São Paulo state is also towards the Paraná River (Fig. 10.1). Discharge zone of the SAG is not well known, but is located out of the study area in São Paulo state and probably out of Brazil in Uruguay and Argentina (Araujo et al., 1999).
