Suggestions for studies related to groundwater captation in the Bauru Group, tectonic considerations

Abstract

The main scope of this paper is to improve the studies of underground water collection processes in order to set suggestions for the Bauru Group, which covers the Paraná basaltic flows as an independent aquifer. The reported area spreads from 49º30' to 50º00' (longitude W) and 20º45' to 21º30' (latitude S) and is comprised of three geologic unities, as follows: on the base are the basaltic flows; above it comes the Bauru Group; on the top are lying the quaternary sediments. The basaltic surface topographic map calls for a general dip from N-NE to S-SW, and it express structural alignments, within great "highs" and "lows". The Bauru aquifer isopach lines show increasing thichness to SW-NE, and no alignments are noticed, but we have thicker compartiments against thinner ones. The watertable depends on the Bauru Group lithofacies variation. Acid water prevails on the majority of the wells (pH between 5,5 and 6,0) but some of them are brackish and depend on the carbonatic cement contents. The cistern hydrostatic level varies from few centimeters to tens of meters in depths measures and spring flows run from few to ten thousand liters per hour. Finally, it seems that the São José dos Dourados, the low Tietê river course, the Peixe and Santo Anastácio rivers are closed to structural alignments.