Hydrochemistry of shallow groundwater and springs used for potable supply in Southern Brazil

Abstract

Landscape characteristics and access type may exert a strong influence on groundwater quality, thereby adversely affecting human health. The aim of this study was to evaluate groundwater quality in springs and shallow wells of rural areas in terms of hydrochemical properties and different water quality indexes by comparing distinct microregions, groundwater sources (springs and shallow wells), and surrounding properties (e.g., presence of livestock, presence of fences, other protection structures, and restrictions on human access). Physical–chemical, chemical, and microbiological parameters were analyzed over 12 months between 2013 and 2014 in the Marombas River basin located in Santa Catarina State, Southern Brazil. Land use and landforms played an important role in controlling groundwater hydrochemistry in rural areas. The type of groundwater source (springs or shallow wells) did not influence water quality, although springs tended to be more susceptible to bacterial contamination, especially in areas with livestock in the surroundings. Chemical relationships allowed classifying these waters as predominantly calcium–magnesium bicarbonate or calcium–magnesium chloride, the latter being the most common in the study region. Groundwater was acidic, with low dissolved salt content, large range in dissolved oxygen concentrations, low turbidity, and presence of fecal coliforms in most studied months. Results indicate that water might be affected by septic tank leakage associated with wastewater and output from agricultural fields, given precarious installation and conservation conditions of springs and shallow wells in this region. When comparing the results with drinking water standards established by Brazilian Health Ministry, 70% of springs and shallow wells were found not suitable for consumption, especially due to organoleptic properties, high aluminum concentrations, and presence of fecal coliforms. Water quality indexes demonstrated that groundwater is suitable for agricultural uses (irrigation, livestock, and fish farming) and drinking, if treated via disinfection, filtering, or boiling before consumption. Nevertheless, use of this water resource, especially without any treatment—as is currently common among users—raises concerns related to its susceptibility to spread waterborne diseases, and lack of information among water users regarding procedures to improve water quality.