Produção Nacional
Os aqüíferos da bacia hidrográfica do Alto Tietê: disponibilidade hídrica e vulnerabilidade à poluição
2001; Sociedade Brasileira de Geologia; Volume: 31; Issue: 1 Linguagem: Inglês
10.5327/rbg.v31i1.916
ISSN2317-4889
AutoresRicardo Hirata, Luciana M. R. Ferreira,
Tópico(s)Groundwater and Isotope Geochemistry
ResumoThe Upper Tiete basin (BAT) is the most densely populated (17.5 million people) hydrologic unit in Brasil. Although superficial resources provide almost the totality of water for the public system, groundwater plays a key role for complementary and private water supply of the region. A coarse estimation has demonstrated that 9 thousand wells are exploiting more than 315 million cubic meters per year (Mm-/a). The BAT involves: i) pre-Cambrian basement rocks (4238 km 2 ), corresponding to Embu Complex, Sao Roque and Serra do Itaberaba groups, and granitoids; and ii) Paleogen and Neogen sediments of the Sao Paulo sedimentary basin (1452 km 2 ), including Taubate Group (Resende, Tremembe, Sao Paulo, and Itaquaquecetuba formations), and neo-Cenozoic deposits. This geologic context defines the Crystalline (SAC) and Sedimentary (SAS) aquifer systems. In this work, four new units are suggested: Sao Paulo and Resende aquifers, associated to SAS, and Granitoid Rock and Metasedimentary Rock aquifers, associated to SAC. The SAS units are unconfmed to locally semi-confined, isotropic, heterogeneous aquifer with granular porosity. The Sao Paulo and Resende aquifers present low (Q/s=0.5 m 3 /h/m) and low-medium (Q/s=0.9 m 3 /h/m) productivity respectively. The SAC units are unconfmed, anisotropic, heterogeneous aquifers with fractured porosity. Due to limited areal expression, the Tremembe and Itaquaquecetuba formations are not considered in this study. The Granitoid Rock Aquifer is constituted by granitoid and gneiss and presents low productivity (Q/s=0.2 m 3 /h/m). The Metasedimentary Rock Aquifer includes quartzite, mica-schist, amphibolite and carbonated rock, with low-medium productivity (Q/s=1.4 m 3 /h/m). It is believed that the higher productivity is due to rock double-porosity. A very extensive work to identify the groundwater pollution risk analyzed the interaction between the aquifer pollution vulnerability map and contaminant load that is, will be or might be applied on the subsurface as a result of human activity. The most dangerous activities were related to 449 industrial plants (mainly metal processing and mechanical engineering), 38 open dumps and 52 urban unsewered sanitation districts. 134 gas station presented underground fuel leakage.
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