Avaliação da vulnerabilidade natural dos aquíferos em Santa Maria - RS

Abstract

The amount of existent water in the nature is finite and your readiness reduces gradation due to the growth population ally to the intensification of the activities of pollutant character. Like this, this work presents a study on the natural vulnerability of the aquifers in the Municipal district of Santa Maria southern Brazil. For the accomplishment of this work it was used the referring data to the underground wells of the Municipal district obtained through the website from the Companhia de Pesquisas e Recursos Minerais (CPRM), these allowed the assembly of spreadsheets starting from the uses excel software containing the following parameters: acronym and numbering of the well, geographical coordinate, altitude (m), well depth (m), exploitation (m3/h), static level (m), aquifer type (free, confined, other), well type, litology, uses of the waters, total dissolved solids (TDS mg/L) and electric conductivity (μS/cm) groundwater. Some visited points, such as, put of fuels and lava-fast they complemented the cadaster executed by Garcia (2004). For the determination of the risk of contamination of the aquifers based on the methodology developed by FOSTER and HIRATA, 1993 and FOSTER et al. 2003, denominated GOD method. A characterization of the natural vulnerability of the area felt starting from three parameters: G = degree of confinement of the underground water; O = occurrence of the general litology of the area; and, D = Depth of the static level. Starting from these three parameters, it was obtained the following classes of vulnerability index: the – 0.1 despise; enter 0.1 – 0.3 low; enter 0.3 – 0.5 media; of 0.5 – 0.7 high and enter 0.7 – 1.0 the extreme class. For determination of the risk of contamination of the groundwaters, it was needed the mapping of the points of interest and of the evaluation of the contamination potential points existent in the study area mainly put of fuels and lava-fast. For the data espacialization of the isovalues cartograms was elaborated through the use of the Surfer 8 software. 194 wells of groundwater were analyzed registered by SIAGAS/CPRM site, and 13 wells registered in field work. As the presence of TDS, was obtained: 149 wells that presented fresh water, 19 wells waters brackywish and 1 well saline water. With relationship to the vulnerability index for the Municipal district of Santa Maria, of the 171 simulate wells, it was obtained the following classes: despise - 6 wells representing 3.5% of the total; low - 4 wells representing 2.4% of the total; media - 47 wells representing 28.4%; high - 112 wells representing 65.8% and it extreme - only 1 well representing 1% of the total. With relationship to the location of the load contaminate, it is observed that most of the positions of fuels and lava-fast they are located in the high vulnerability area, what characterizes as area of risk of contamination of the groundwaters. Deserving a special attention on the part of the proprietors policy agents in relation to the pontential risk of groundwater contamination. The need is pointed out of promoting a better soil occupation and use planning of the activities installed in Santa Maria, as form of protection of the groundwater promoting the maintainable use of this mineral resource for actual and the future generations.