Authors : T.T. Emberga, A.I. Omenikolo, A.I. Opara, S.O. Onyekuru and C.C. Agoha
Abstract: Comparative Assessment of Analytical models used for Aquifer geo-hydraulic Estimation in Imo River Basin Nigeria was carried out to determine the best geophysical models in estimating the hydraulic properties of aquifer systems. The Imo River Basin lies between Latitudes 4°38’N and 6°01’N and between Longitudes 6°53’E and 7°32’E and covers an area of about 9100 km2. The litho-stratigraphic units within the study area are Ajali Formation, Nsukka Formation, Imo Shale Formation, Ameki Formation and Benin Formation. The Da-Zarrock parameters (transverse unit resistance and longitudinal conductance) were used to determine aquifer hydraulic characteristics. A total of 569 Vertical Electrical Soundings (VES) using the ABEM terrameter (SAS) 4000 were acquired in the study area applying the Schlumberger electrode configuration and a maximum electrode spacing of 1000 m. Out of the 569 VES data points, 20 soundings (parametric soundings) were made at the vicinity of existing boreholes for comparative analysis and for quality control of the data. The hydraulic conductivity in the study area was estimated using Niwas and Singhal, Heigold model and the new geophysical model generated with an average of 13.19, 1.74 and 4.62 m/day, respectively. The study revealed a mean transmissivityTmean = 140.8 m2/day and a mean storativity of 5.3×10–5 for the aquiferous units in the Ajali Formation. A mean transmissivityTmean = 193.5 m2/day and mean storativity 5.54×10–5 were estimated in Ameki Formation. The Benin formation revealed a mean TransmissivityTmean of 784 m2/day and a mean storativity of 5.11×10–5. The aquifers in the Imo Shale Formation have a mean transmissivityTmean = 205.2 m2/day with a mean storativity of 3.48×10–5. The aquifers in the Nsukka Formation have a mean transmissivityTmean = 211.5 m2/day with a mean storativity of 4.8×10–4 while the aquifers in the Ogwasi/Asaba Formation have a mean transmissivityTmean = 100.2 m2/day with a mean storativity of 4.86×10–5. The average thickness of the aquiferous units in the study area is 39.8 m while that of the aquifer depth is 115.5 m. The mean values of aquifer resistivity and aquifer conductivity are 1963.2 Ωm and 0.00186 Sm–1, respectively.
T.T. Emberga, A.I. Omenikolo, A.I. Opara, S.O. Onyekuru and C.C. Agoha, 2021. Comparative Assessment of Analytical Models used for Aquifer Geo-Hydraulic Estimation in Imo River Basin, Nigeria. Online Journal of Earth Sciences, 15: 1-16.