Comparative analysis of techniques for estimating geohydraulic properties and aquifier vulnerability in Imo River Basin, SouthEastern Nigeria
| dc.contributor.author | Emberga, Terhemba Theophilus | |
| dc.date.accessioned | 2026-03-24T13:31:55Z | |
| dc.date.available | 2026-03-24T13:31:55Z | |
| dc.date.issued | 2019 | |
| dc.description | This thesis is for the award of Doctor of Philosophy (PhD.) in Geophysics | |
| dc.description.abstract | Comparative Analysis of Techniques for Estimating Geohydraulic properties and Aquifer Vulnerability in Imo River Basin, Southeastern Nigeria was carried out to determine the most suitable and cost effective techniques for the determination of hydraulic properties and groundwater vulnerability in the Imo River Basin. The basin which lies between Latitudes 4° 38' and 6° 01' N and Longitudes 6° 53' and 7° 32' E with an area extent of about 9100 km is underlain by the Ajali, Nsukka, Imo Shale, Ameki, Ogwashi-Asaba and Benin Formations. Five hundred and sixty-nine (569) vertical electrical soundings (VES) using the ABEM Terrameter (SAS) 4000 with maximum electrode spacing of 1000 m were acquired in the study area. Thirty (30) parametric soundings out of the entire VES data points were carried out in the vicinity of existing boreholes for comparative analyses and quality control. Twenty (20) sandstone samples collected from the six (6) formations were sieved and the resulting data processed to obtain hydraulic conductivities of aquiferous units. Comparatively, Da-Zarrock parameters (transverse unit resistance and longitudinal conductance) were used to determine aquifer depth, thickness and hydraulic characteristics from VES Data. Additionally, estimates of hydraulic conductivity were made using the techniques of Niwas & Singhal and the Heigold’s method. A New model that is Novel and formation sensitive was also developed using resistivity and existing pumping test data. The mean aquifer resistivity revealed 1397.96 in Ajali, 2116.92 in Ameki, 2188.15 in Benin, 632.55 in Imo shale,1355.08 in Nsukka and 2072.91Ω m in Ogwasi-Asaba Formations while the mean aquifer thickness in Ajali revealed 40.83, while those in Ameki were 42.68, 39.38 in Benin, 26.78 in Imo Shale, 36.34 in Nsukka and 37.39 m in Ogwasi-Asaba. The study also revealed the aquifer thickness of 122.04 in Ajali, 121.86 in Ameki, 114.46 in Benin in 73.73 in Imo shale, 36.92 in Nsukka and 109.66m in Ogwasi- Asaba. The results of the hydraulic conductivity and that generated with the model revealed average values of 13.19, 1.74 and 4.62 m/day respectively. The hydraulic conductivity values estimated using the empirical formulae of Hazen, Kozeny-Carman, Breyer, Slitcher and USBR have mean values of 1.55, 256.8, 0.58, 2.82 and 0.046 m/day respectively. These results were validated with the existing pumping test data using Artificial Neural Networks. Mean Transmissivity (Tmean) and Storativity values computed from the hydraulic conductivity data revealed values of 140.8 m2 /day and 5.3 × 10-5 , respectively for the aquiferous units in the Ajali Formation. In the same vein, Tmean of 193.5 m2 /day and mean storativity of 5.54× 10-5 were estimated for Ameki Formation aquifers, while Benin Formation aquifers revealed Tmean of 784m2 /day and mean storativity of 5.11 x 10-5. The aquifers in the Imo Formation have a mean transmissivity Tmean = 205.2 m2/day with a mean storativity of 3.48× 10-5 . The aquifers in the Nsukka Formation have a mean transmissivity Tmean = 211.5 m2 /day with a mean storativity of 4.8 × 10-4 while the aquifers in the Ogwasi/Asaba Formation have a mean transmissivity Tmean = 100.2 m2 /day with a mean storativity of 4.86 × 10- 5 . The vulnerability of the aquifers evaluated using Geologic (DRASTIC and GOD) and Geophysical (Integrated Electrical Conductivity, IEC) models generated vulnerability maps which displayed areas within the northern part of the study area to have low and moderate vulnerabilities while the southern part has aquifers with high vulnerability to pollution. The estimated percolation time of contaminants using IEC model revealed that it will take contaminants from several months to about 25 years to get to the groundwater system in the study area. The good correlation of hydraulic conductivity results between the new model and existing pumping data implies that generated model can substitute the laborious and expensive pumping tests of boreholes in areas with similar geologic formations. | |
| dc.identifier.citation | Emberga, T. T. (2019). Comparative analysis of techniques for estimating geohydraulic properties and aquifier vulnerability in Imo River Basin, Southeastern Nigeria [Unpublished Doctoral Thesis]. Federal University of Technology, Owerri, Nigeria | |
| dc.identifier.uri | https://repository.futo.edu.ng/handle/20.500.14562/2470 | |
| dc.language.iso | en | |
| dc.publisher | Federal University of Technology, Owerri | |
| dc.rights | Attribution-NonCommercial-ShareAlike 4.0 International | en |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-sa/4.0/ | |
| dc.subject | Geohydraulic | |
| dc.subject | vertical electrical sounding | |
| dc.subject | aquifer resistivity | |
| dc.subject | aquifer vulnerability | |
| dc.subject | sieve analysis | |
| dc.subject | pumping test | |
| dc.subject | Department of Geology | |
| dc.subject | da-zarrock parameters | |
| dc.subject | artificial neural network | |
| dc.title | Comparative analysis of techniques for estimating geohydraulic properties and aquifier vulnerability in Imo River Basin, SouthEastern Nigeria | |
| dc.type | Doctoral Thesis |