| Abstrakt: |
This research presents a preliminary approach on the natural vulnerability evaluation of shallow aquifer units to surface pollutants in the easternmost part of Dahomey Basin, within southwestern Nigeria. This was carried out using the geoelectric sounding method and Dar Zarrouk longitudinal conductance for effective groundwater management. A total number of 48 vertical electrical soundings were conducted over the study area to delineate the depth range of the shallow aquifer units and assess the groundwater vulnerability to near-surface contaminants. The results of the geoelectric sounding enabled the delineation of shallow to intermediate aquifer units. The aquifer system occurs at a depth ranging from 5.7 to 97.3 m, with an aquifer thickness between 9.8 and 107.2 m. The pseudo-thickness map also reveals that there are thin to moderate overburden thicknesses covering the aquifer unit in the study area. The thickness of these overburden layers range from 5 to 88.9 m and are characterized by lateritic sand, pure clay of resistivity between 0 and 50 Ωm, sandy clay of resistivity between 50 and 70 Ωm, and clayey sand between 70 and 91.8 Ωm serving as a protective cover to the aquifer units. Longitudinal unit conductance of the area reveals values between 0.013 and 10.36 mho/m and it indicates that almost 75% of the areas have weak/poor protective capacity of the overburden to the aquifer units. From the combination of all the results, the study area is divided into low, moderate, and high groundwater protective zones with overburden thickness of < 10 m, between 10 and 30 m, and > 30 m, respectively. Water treatment is therefore encouraged before consumption to mitigate the effect of groundwater pollution. [ABSTRACT FROM AUTHOR] |
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