Evaluation of groundwater repositories in parts of Enugu, Eastern Nigeria via electrical resistivity technique

Abstract

Resistivity survey was carried out in Enugu North, Southeastern Nigeria, in order to evaluate the groundwater condition of the area. The inadequacy of surface water, proper knowledge of the aquifer and increasing population has affected the extraction and development of groundwater in the area. Resistivity, thickness, depth, curve frequencies and protection level were determined. The result revealed a total of 5–6 geoelectric layers with model curves exhibiting the following curve types: KHK taking about 10%; AAKQ, KHAK, KHAA, HKQ, HKQQ and HAA taking 12%, AAA, AKH, HAK and KHKQ taking 24% while AKQ and AAK take 20 and 34%, respectively. The aquifer is within the fourth and fifth layer considering the layer with the largest thickness with the fourth layer taking up to 84% of the aquifers in the study area. The overburden layer resistivity and thickness ranged from 589.8 to 85,094.8 Ωm and 8.9 to 99.5 m with mean values of 42,642.3 Ωm and 54.2 m, respectively. The contour maps were generated using Surfer software package version 15 which show the variation of overburden parameters. The study area was generally considered as having a high protective level as a result of the low values of geophysically based protection index of the aquifer layers and weak to fair GPI rating implying that the aquifer can be protected from infiltrating contaminants. However, high hydraulic conductivity and porosity suggest high groundwater potential and high infiltration of polluted geofluids.