Application of self-organizing maps and GIS: spatial analysis of hydrochemistry of the aquifers in a Brazilian medium-size city

Abstract

The objective of this study was to identify hydrochemical spatial patterns of groundwater;n northeastern Brazil (Itabuna-BA). For this, the self-organizing maps and the GIS were applied in secondary data (major ions and electrical conductivity), with the purpose of analyzing the patterns and zoning the sectors with different hydrochemical characteristics. The aquifers of the study area are fractured, medium-low hydrogeological potential and relative lithological-geochemical variability. With the subsidy of spatial statistics and multivariate statistics, three distinct sectors (1, 2 and 3) were identified in the zone of greatest concentration and effective use of groundwater wells. Sector 3 presented water with higher salinity and greater geochemical complexity, being these brackish and salted, suggesting a greater control of the chemical weathering of sienitic rocks. The waters in the other sectors occur predominantly in another geochemical context (granulites and metatonalites), being brackish and freshwater, presenting correspondence with the observed ionic load. Zoning, subsidized by artificial neural networks and GIS, has the potential to contribute effectively to groundwater management. For Itabuna, the findings presented here may subsidize to a master plan that contemplates policies that promote the protection and conservation of aquifers that regulate the use of certain types of water and carry out investments in sanitation and water treatment.

Keywords

• Gestão de recursos hídricos. Aquíferos fraturados. Qualidade da água. Segurança hídrica.