Modelagem da potencialidade hídrica e vulnerabilidade a contaminação das águas subterrâneas da sub-bacia do rio Siriri, Estado de Sergipe: um estudo com base em geotecnologias

Abstract

The present research aims to produce models of potentiality and vulnerability to contamination groundwater of sub-basin of the river Siriri using procedures in Geotecnologies. The spatial modeling of groundwater includes steps that allow an adequate approximation of the real environment in sub-surface. In the research these steps consist in collect existing data and information, collection of new data and processing, interpretation, integration and modeling. Images from the Landsat-TM satellite and digital terrain model were used in order to complement the geological information contained in the pre-existing maps, extracting the structural lineaments, important in the transmissibility between the surface and sub-surface. To create the model of groundwater potentiality were considered modeling procedures based on knowledge that uses selected data from empirical knowledge or evidence to characterize the factors that influence the phenomenon. The factors or criteria used were: rainfall , use and land cover, soil type, slope, drainage density, lineament density and permeability of rocks. The AHP (Analytic Hierarchy Process) assisted in the integration of these factors, in evaluation of parameters and weights assigned, aiming to ensure the development of criteria, sub-criteria and weights of importance to generate the model of groundwater potentiality. Thus, the analysis of the factors was realized in order to assign weights to their respective classes, as well as to each factor, according to the decision rules previously defined in the context of the objective to be achieved. The modeling in environment of Geographic Information System allowed the definition of five classes of potential: very low, low, moderate, high and very high. The modeling of groundwater vulnerability to contamination was performed by the method "GOD" because of its simplicity and ease implementation. The cartographic procedures for preparation of the groundwater vulnerability map, involved maps algebra operations applied to the following themes: geological map and map of static level wells variation. The general assessment and the model creation consisted in definition of five classes of vulnerabilities: negligible, low, medium, high and extreme. Besides vulnerability, was applied the methodology POSH of classification potentially contaminating activities for the preparation of the statement of danger contamination from the land uses of study area. The modeling in environment of Geographic Information System allowed the definition of five classes of groundwater potential: very low, low, moderate, high and very high. The aquifers Sapucari and Barreiras stands out with biggest flows. The general assessment and creation of model of vulnerability consisted in the definition of five classes: negligible, low, medium, high and extreme. The aquifers formed by the beach sediments and the alluvial and Barreiras are the most vulnerable to contamination, with classes of extremely and high vulnerability, which implies the need for studies of water quality and planning of land use. By linking the maps of vulnerability and danger of contamination, it is observed the presence of activities with high potential for contamination in areas of high and extreme vulnerability.