Avaliação do índice de vulnerabilidade na bacia hidrográfica do Rio Santa Maria - RS

Abstract

The water is a natural resource and it s essential to the maintenance the lives of the planet. But, it is also used to develop many economic activities. It s found at the nature in different quantities that had presented variations in time, space and in scale. However, the quality degradation is high. The general aim of this study was to stablish and map the natural aquifers vulnerabilities Hydrographic Santa Maria River Basin, at Rio Grande do Sul State, southern of Brazil. The methodology used was named GOD Foster et al., (2003), based on three parameters: Grade of groundwater confinement, Occurrence of litologies above saturated zone and, Depth of water table level, using information from existing data. The data base prepared and than simulated with SURFER 6.0. presented maps and discussed results related to countries areas, total or partially belonged to this basin. Dom Pedrito, Lavras do Sul and São Gabriel were located on crystalline rocks belong to Escudo Uruguaio Sul Riograndense, forming fractured aquifers. On the other side, Sant Ana do Livramento, Cacequi and Rosário do Sul were located on sedimentary rocks that belong to Guarany Aquifer System/GAS. According to information from IBGE (2000) around 257,986 people lived in this basin. Cacequi and Sant Ana do Livramento were totally supplied by groundwater. The level of information about well was punctually and scarce. We had 528 well records accessible, but only 341 had all the parameters necessary to use in the methodology. At Sant Ana do Livramento were plotted the principal potential points of contamination. The vulnerability index obtained had the predominance of the High class, at the central portion of the basin. The second was Medium class, and the Small class occurred at isolated points at the North and East and West border. The two classes with minor spatial representation were Despicable and Extreme. Therefore this study provides many parameters related with the use and manage of the groundwater and its relations related with National and State environmental policy. This methodology presented some limitations, but was good, rapid and efficient to map areas susceptible to contaminations. This information will be used by integrated politic of groundwater.