T.T.  Emberga, A.I.  Omenikolo, A.I.  Opara, S.O.  Onyekuru, C.C.  Agoha, 
    Comparative Assessment of Analytical Models used for Aquifer Geo-Hydraulic Estimation in
Imo River Basin, Nigeria,
    Online Journal of Earth Sciences,
    Volume 15,Issue 1,
    2021,
    Pages 1-16,
    ISSN 1991-7708,
    ojesci.2021.1.16,
    (https://makhillpublications.co/view-article.php?doi=ojesci.2021.1.16)
    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&deg;53&#146;E and 7&deg;32&#146;E and covers an area of about 9100 km<sup>2</sup>.
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
transmissivityT<sub>mean</sub> = 140.8 m<sup>2</sup>/day and a mean storativity
of 5.3&times;10<sup>&#150;5</sup> for the aquiferous units in the Ajali
Formation. A mean transmissivityT<sub>mean</sub> = 193.5 m<sup>2</sup>/day
and mean storativity 5.54&times;10<sup>&#150;5</sup> were estimated in Ameki
Formation. The Benin formation revealed a mean
TransmissivityT<sub>mean</sub> of 784 m<sup>2</sup>/day and a mean
storativity of 5.11&times;10<sup>&#150;5</sup>. The aquifers in the Imo Shale
Formation have a mean transmissivityT<sub>mean</sub> = 205.2
m<sup>2</sup>/day with a mean storativity of 3.48&times;10<sup>&#150;5</sup>. The
aquifers in the Nsukka Formation have a mean
transmissivityT<sub>mean</sub> = 211.5 m<sup>2</sup>/day with a mean
storativity of 4.8&times;10<sup>&#150;4</sup> while the aquifers in the
Ogwasi/Asaba Formation have a mean transmissivityT<sub>mean</sub>
= 100.2 m<sup>2</sup>/day with a mean storativity of 4.86&times;10<sup>&#150;5</sup>. 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 &#937;m and 0.00186 Sm<sup>&#150;1</sup>,
respectively.
    Keywords: Da-Zarrock parameters;geo-hydraulic;transmissivity;aquifer storativity