Prospecting Potential Groundwater Zones through Geotechnology and Statistics Techniques in the Grande River Basin, Bahia,Brazil

The source of the Grande river and its tributaries on the left bank are located in a tropical region adjacent to the humid valley of the Tocantins river, with rainfall that favors the continuity of the rivers. In the middle and east part of the basin, the predominance is of the semi-arid climate, as well as typical of the middle São Francisco basin, with irregular rainfall that does not contribute to the supply of the rivers. It is noteworthy that most of the tributaries of the hydrographic basin are intermittent. The Grande river basin is part of two important hydrogeological systems, the Group Bambuí system and the Urucuia system (SAU), which is the most important system in the western region of Bahia, as well as one of the most important in the São Francisco river basin, as well as the entire brazilian Northeast region, in addition to being one of the most relevant in the country, since it is a strategic source of water. Such hydrogeological systems are directly responsible for supplying the hydrographic basin in its dry periods. The Brazilian semi-arid region, with its limited water resources, is currently classified as a critical dry and water-poor area. This study aims to identify potential areas of groundwater in the aforementioned hydrographic basin, located in the middle eastern portion of the São Francisco river basin, in the State of Bahia. Integrating geological and hydrogeological analyses, remote sensing, geographic information systems (GIS) and multicriteria statistical evaluation (AHP) techniques. It is intended to create thematic layers in a GIS where values will be assigned using appropriate weights and classifications in relation to their relative contribution to the occurrence of groundwater through multicriteria assessment techniques. These layers include lithology, geomorphology, lineament density, drainage density, soil texture, precipitation, and slope. The final groundwater potential map is composed of five classes of groundwater potential: very high, high, moderate, low and very low. The validity of the results of this GIS-based model was performed by superimposing existing wells, analyzing the statistical probability of the existence of groundwater. The single parameter sensitivity test was performed to evaluate the influence of the signaled weights on the groundwater potential model, and new effective weights will be derived after the analysis, as a way to calibrate the model, and the ROC analysis was applied to validate the model

Keywords :Groundwater, Grande River Basin, AHP, Prospecting, Statistical probability, GIS