ABSTRACT
Detailed hydro -geophysical and hydro-geochemical studies were carried out in part of the Niger Delta Basin Nigeria. The objectives were to map and provide evidences that the coastal aquifers in the study area have been intruded by saltwater and to establish analytical/empirical relationships between resistivity and geochemical parameters. Twenty three vertical electrical sounding (VES) data employing the Schlumberger electrode configuration were acquired in different parts of the study area, with a maximum electrode separation of 500m. The VES data were modelled with the OFFIX 3.1 software. The interpreted VES curves revealed mainly the QH, KH, KHKH, AK, QQ, KHK, HKH, QQH and HK curve types. Aquifer resistivity across the study area ranges from 39.7Ωm to 19033.9 Ωm while aquifer depth varies between4.5m and 83.9m. Aquifer thickness is variable in the study area with values ranging between2.4m and 78.1m. The Dar-zarrock parameters revealed that the longitudinal conductance(S) and transverse resistance(R) have mean values of 0.319 Sm and 55311.74Ωm2respectively. The mean concentrations of the cations including chloride (Cl-), bicarbonate, nitrate (NO3-),and sulphate are given as 90.73 mg/l,22.33 mg/l,0.90 mg/l, and 14.70 mg/l respectively. Similarly, analysis of the mean concentrations of the anions revealed that iron (Fe2+), potassium (K+),magnesium (Mg2+),calcium, and sodium of 0.24 meg/l, 0.899348 mg/l,, 8.126783mg/l, 8.528 mg/l, and 3.848783mg/l respectively. Hydrogeochemical facies identified in the study area includes Ca-Mg-Cl, Mg-Ca-Cl, Ca-Mg-Cl,and Ca-Na+K-Cl facies type. The low resistivity values revealed in different parts of the study area is indicative of areas contaminated by saltwater intrusion. In addition, since the average chloride concentration across the study area (which is a major component of saltwater) is greater than 40mg/l, and the Cl- /HCO3- ratio is greater than two, it is therefore believed that there is serious salt water encroachment within the study area.
Keywords: Salt water intrusion, coastal aquifers, hydrogeophysical, hydrogeochemical, vertical electrical sounding, Niger delta
CHAPTER ONE: INTRODUCTION
1.1 Background Information
1.2 Statement of Problem
1.3 Aim and Objectives of the Study
1.4 Justification of Study
1.5 Scope of the Study
1.6 Location and Physiograph of the Study Area
1.6.1 Location of the Study Area
1.6.3 Vegetation
1.6.4 Relief
1.6.5 Climate
1.6.6 Drainage 7
1.6.7 Soils 8
1.6.7.1 Soil Erosion 8
1.7 Geology of the Study Area 8
1.8 Hydrogeology of the Study Area 13
1.9 Stratigraphysical Succession of the Niger Delta 14
CHAPTER TWO: LITERATURE REVIEW
2.1 Review of Previous Studies 15
2.2 Surface Geophysical Survey 18
2.3 Theoretical Framework 20
2.3.1 Ghyben-Herzberg Relation 20
2.3.2 Saltwater intrusion 24
2.4 Cause and Impact of Saltwater Intrusion 25
2.4.1 Groundwater Extraction 27
2.4.2 Canals and Drainage Network 27
2.4.3 Effect of Saltwater Intrusion on Water Supply 28
2.5 Sources of Saltwater 29
2.6 Freshwater-Saltwater Interactions 30
2.6.1 The Transition Zone 31
2.7 Detecting and Monitoring Saltwater Occurrence and Intrusion 33
2.9 Review of Geochemistry Analysis 35
2.10 Physico-Chemical Analysis of the Water Sample 36
CHAPTER THREE: METHODOLOGY
3.1 Materials and Methodology 37
3.1.1 Materials 37
3.1.2 Methodology 38
3.2 Data Collection 39
3.2.1 Vertical Electrical Sounding [VES] 40
3.2.1 Schlumberger array for Resistivity Survey 41
3.3 The Dar- Zurrouk Parameters (DZP) 44
3.3.1 Aquifer Hydraulic Characteristics from Surface
Electrical Resistivity 44
3.4 Geochemistry survey/Analysis. 46
3.4.1 Analytical techniques 46
3.5 Methods for measuring salinity 47
3.5. Computer Software 48
3.5.1 Spatial Distribution Maps 48
3.6 Data Processing 48
3.6.1 Iso-Resistivity Modeling 49
3.6.2 Irrigation Water 49
3.6.2.1 Sodium Absorption Ratio (SAR) 49
3.6.2.2 Sodium Percentage 50
3.6.2.3 The Magnesium Absorption Ratio (MAR) 50
3.6.2.4 Residual Sodium Carbonate (RSC)
51
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3.6.2.5 Kelly’s Ratio (Kr) 51 3.6.2.5 Pollution Index (P1) 51
3.6.3: Qualitative Curve Description 52
3.6.4. Hydrogeochemical facies and classification 53
3.6.4.1 Stiff Diagrams 53
3.6.4.2 Piper Diagram 55
3.6.4.3 Durov Diagrams 56
3.6.4.4 Schoeller Diagrams 56
CHAPTER FOUR: RESULTS AND DISCUSSION
4.0 Results Presentation 57
4.1 Resistivity Results, Analysis and Discussion 57
4.1.1 Iso-Resistivity of the Study Area 62
4.2 Geochemical Results, Analysis and Discussion 76
4.2.1 Ionic Ratio and Irrigational Water 79
4.2.2 Hydrogeochemical facies and classification 101
4.3 Correlation of Resistivity and Geochemical
Data of the study areas 120
4.4 Discussion of Results 123
CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion
5.2 Recommendations
5.3 Contribution to Knowledge
References
APPENDIX
Chukwuemeka, C (2021). DELINEATION OF SALTWATER INTRUSION ZONE IN PARTS EASTERN OF NIGER DELTA USING RESISTIVITY AND GEOCHEMICAL DATA. Afribary. Retrieved from https://afribary.com/works/delineation-of-saltwater-intrusion-zone-in-parts-eastern-of-niger-delta-using-resistivity-and-geochemical-data
Chukwuemeka, Choko "DELINEATION OF SALTWATER INTRUSION ZONE IN PARTS EASTERN OF NIGER DELTA USING RESISTIVITY AND GEOCHEMICAL DATA" Afribary. Afribary, 23 Feb. 2021, https://afribary.com/works/delineation-of-saltwater-intrusion-zone-in-parts-eastern-of-niger-delta-using-resistivity-and-geochemical-data. Accessed 25 Apr. 2024.
Chukwuemeka, Choko . "DELINEATION OF SALTWATER INTRUSION ZONE IN PARTS EASTERN OF NIGER DELTA USING RESISTIVITY AND GEOCHEMICAL DATA". Afribary, Afribary, 23 Feb. 2021. Web. 25 Apr. 2024. < https://afribary.com/works/delineation-of-saltwater-intrusion-zone-in-parts-eastern-of-niger-delta-using-resistivity-and-geochemical-data >.
Chukwuemeka, Choko . "DELINEATION OF SALTWATER INTRUSION ZONE IN PARTS EASTERN OF NIGER DELTA USING RESISTIVITY AND GEOCHEMICAL DATA" Afribary (2021). Accessed April 25, 2024. https://afribary.com/works/delineation-of-saltwater-intrusion-zone-in-parts-eastern-of-niger-delta-using-resistivity-and-geochemical-data