Aquifer vulnerability mapping using SINTACS model: Implication for groundwater management in a granular sandstone formation

Indices of SINTACS were used to analyze the aquifer vulnerability of the Lafia Formation aquifer (central Nigeria). The assessment of the aquifer vulnerability of the Lafia Sandstone aquifer is essential because the aquifer constitutes the only aquifer in the region that supplies the water demand of the region for all purposes. The urban area is growing and as such, more domestic and industrial wastes are generated which are disposed of indiscriminately. Contemporaneously, agricultural activities are on the increase in the rural areas which generate agricultural wastes. The SINTACS model employs seven parameters (depth to water level, effective infiltration, unsaturated zone, soil media, aquifer media, hydraulic conductivity, and topographic slope), which were employed to produce vulnerability maps. The severe vulnerability index (VI) ranged from 139.79 to 209.19. The vulnerability mapping reveals that the water-bearing formation is highly vulnerable in the central and southern parts of the area, which account for 27.98% of the total area. The medium vulnerability area encompasses approximately 46.23% of the region and is the most prevalent vulnerability class and 25.79% of the area around the northern part of the area accounts for low vulnerability. Nitrate concentrations measured in groundwater of the area compared significantly with the vulnerability zones classified by the VI. Parameters for the unsaturated zone and depth to water level imposed the largest impact on the VI thus, during groundwater development, wells should be made to drill to greater depths, wells should be concentrated in the areas of low and medium vulnerability, and indiscriminate disposal of wastes should be discouraged.