Protective capacity assessment of a shallow aquifer at the eastern part of Ado-Ekiti, southwestern Nigeria

Abstract

Vertical Electrical Soundings (VES) survey has been undertaken at the eastern part of Ado-Ekiti, southwestern Nigeria to assess the aquifer protective capacity of the overburden units of the area. The Schlumberger electrode array was adopted with a maximum current electrode spread (AB) of 300 m. Thirty-six (36) VES points was occupied and processed through a partial curve matching technique and 1-D forward modeling computer-assisted software. The interpretation revealed H, A, KH and HA-type curves and three major geoelectric layers overlying the resistive basement. The groundwater potential and overburden protective capacity maps were prepared. The groundwater in the area was categorized into high, medium and low groundwater potential zones. About 80% of the study area falls within the moderate/low groundwater potential zone while the remaining 20% constituted the high groundwater potential zone (Agric Olope area). Hence, the groundwater potential rating of other areas is considered to be low. The values of longitudinal conductance (ranging from 0.01 to 2.01 mhos) of the area enabled the overburden units to be rated into good, moderate and weak protective capacity. About 75% of the area falls within the good/moderate rating while 25% constitutes the weak/poor protective capacity rating (Agric Olope area), suggesting that the groundwater around Agric Olope is vulnerable to contamination.