Application of improved stratigraphic modified Lorenz plot and flow zone indicator in discriminating the Igbo-Etiti aquifer into hydraulic flow units, eastern Nigeria

Abstract

Discriminating the Igbo-Etiti aquifer sequence into hydraulic flow units was carried out employing integrated method. The method demonstrated an excellent potentiality in delineating and classifying the aquifer into hydraulic flow units (HFU). Results of electrical resistivity survey identified five geoelectric layers in the study area. The fourth layer with the aid of the layer's geologic unit characteristics and borehole lithology was delineated as the aquifer layer. Results from improved stratigraphic modified Lorenz plot (ISMLP) identified the slope, angle and percentage contributions of the established HFUs to range from 0.0029 to 3.1455, 0.1660° to 72.364° and 1.3–76.2% respectively. ISMLP result analysis delineated a total of five (5) classes of hydraulic flow units. These classes of HFUs based on efficiency ranking and classification, range from barrier unit with tight flow capacity efficiency to super conductive unit with good flow capacity efficiency. Results of ISMLP delineated group 4 HFU (G4 HFU) with a total flow capacity percentage contribution of 5.6% as a super conductor unit and the best flow capacity efficiency unit in the study area. G2 HFU described to be a conductor unit was identified as the dominant class of HFU in the study area with a total flow capacity contribution of 76.2% to the overall aquifer flow capacity. Results from flow zone indicator (FZI) method revealed a total of five (5) hydraulic flow units with FZI unique values of 16, 17, 18, 19 and 20. FZI results, identified HFU3 and HFU4 as the most occurring HFU in the aquifer layers, with HFU1 and HFU2 outlined as the least occurring HFU. The integrated approach successfully and uniformly identified five (5) classes of HFUs in the study area. Dykstra-Parson's coefficient of 0.618 revealed very high heterogeneous aquifer layers.