Abstract

The impact of certain unregulated land-use activities harms the quality of water resources and reduces the sufficiency of drinking water in many developing countries. This study aimed to capture the impact of such activities and evaluate the specific groundwater vulnerability using a modified DRASTIC approach. The DRASTIC-L_uP_a was proposed and implemented for Aba City, Nigeria by incorporating land-use and the impact of pumping layers to the “intrinsic” DRASTIC parameters. The results of the analysis revealed that the area classified as “low” was 15 and 79.1% as “medium” and 5.9% as “high” vulnerability classes for the DRASTIC. Whereas for the DRASTIC-L_uP_a model 3.2% for “low”, 54.3% for “medium”, 41.8% for “high” and 0.7% for “very high” were found. The transitions in the vulnerability classes of areas displaying “high” and “very high” found in the DRASTIC-L_uP_a model represent the impact of urban hotspots observed in the area. This result implies that groundwater protection measures should be implemented in the area designated with “low” and “medium” vulnerability classes and used for abstracting clean water for drinking purposes. The proposed model enhances the predictability and guarantees better transferability of the approach in urban settings with similar urban trends.

Key words: Drinking water, DRASTIC, groundwater, groundwater vulnerability assessment, Nigeria.

Abbreviation

AVI, Aquifer vulnerability index; COP, concentration of flow, overlaying layer and precipitation; DEM, digital elevation model; DRASTIC, depth to the water, net recharge rate, aquifer material, soil type, topography, impact of vadose and hydraulic conductivity; DRASTIC-L_uP_a, depth to the water, net recharge rate, aquifer material, soil type, topography, impact of vadose, hydraulic conductivity, land-use and impact of active pumps; EPIK, Epikarst, protective cover, infiltration conditions, Karst network development; GLEAMS, groundwater loading effects  of  agricultural  management systems; GOD, groundwater hydraulic confinement, aquifer overlaying strata resistivity and depth to the water table; HSPF, hydrological simulation program Fortran; MODFLOW, MODular groundwater FLOW model; SEEPAGE, system for early evaluation of pollution potential from agricultural groundwater environments; SINTACS, Soggienza-depth to groundwater (S); Infiltrazione - effective Infiltration (I); Non saturo -unsaturated zone attenuation capacity (N), Tipologia della copertura - Soil overburden attenuation capacity (T); Acquifero - Saturated zone features (A), Conducibilità - Hydraulic Conductivity (C), and Superficie topografica - Topographic surface slope (S); SRTM, shuttle radar topographic mission; SWAT, soil and water analysis tool; TPH, total petroleum hydrocarbon; WQI, water quality index.