EVALUATION OF THE VULNERABILITY AND QUALITY OF GROUNDWATER IN AREAS OF INFLUENCE OF THE GANGAN RIVER, IN SÃO LUÍS – MA

Abstract

Groundwater plays a key role in human supply, especially in regions with a scarcity of surface water resources. This study aimed to analyze the quality of water from wells for human consumption in the area of influence of the Gangan River, in the Turu neighborhood, in São Luís – MA, analyzing its compliance with Brazilian legislation, such as CONAMA Resolution No. 396/2008 and Ordinance GM/MS No. 888/2021. Physicochemical and microbiological analyses were carried out in three wells with different depths (60 m, 30 m and 48 m). The parameters analyzed included hydrogen potential (pH), chlorides, total solids, hardness, iron, total coliforms and Escherichia coli. From these data, the Natural Groundwater Quality Index (IQNAS) was calculated, which ranges from 0 to 100, where higher values indicate better water quality. For the analysis of the vulnerability of the aquifer, the GOD method was applied, which considers the type of aquifer, the lithology of the aquifer and the depth of the water table.  The results indicated that the Natural Groundwater Quality Index (IQNAS) was classified as "unacceptable" at all collection points, and the vulnerability of the aquifer was classified as low, according to the GOD evaluation method. Although the physicochemical parameters were in accordance with the potability standards, the presence of total coliforms was detected, which compromised the potability of the water for human consumption. This study highlights the importance of continuous monitoring of groundwater quality, aiming to ensure public health and the sustainability of water sources.