Groundwater Chemistry and Modeling of Aquifer Depth around Uburu-Okposi Salt Lakes, South Eastern Nigeria

Abstract 

The study area comprised Uburu and Okposi towns in Ohazara Local Government Area, Ebonyi state and it lies between latitudes 60 00’N and 60 05’N, and longitudes 70 44’E and 70 50’E. The area belongs to the saline hydrogeological groundwater basin of Albian Asu River Group in Cross River Basin. Three major outcrops of saline groundwater in the study area are: Umuchime- Uburu lake, Ivu-Ezizo and Amaechi-Okposi lakes. The saline lakes support long production of salts by rural women via local means. 20 water samples from the lakes, dug-wells and boreholes were analyzed to determine the hydrogeochemical constituents of the area. Values of total dissolved solids (TDS) in the samples range between 130 and 256,100mg/l. Calcium(Ca2+), magnesium (Mg2+) and sodium (Na2+) show significant concentrations of cations between 6 and 1440mg/l, 2 and 245mg/l and, 7 and 1231mg/l respectively. Chloride is the most dominant anion and it ranges between 1000 and 1,153640mg/l. Total dissolved solids (TDS), chloride (Cl- ) and calcium (Ca2+) concentrations are observed to be above objectionable limits for drinking water in the area. The chemical constituents revealed two saline groundwater types in the area; Ca-Cl and Mg-Cl waters. The Ca2+ and Mg2+ constituents generated hard water in the study area. The calculated sodium absorption ratio (SAR) indicated depletion of sodium in the water and, as a result, the saline groundwaters are suitable for irrigation. Vertical Electrical Soundings revealed that the saline groundwaters with low resistivities are in the less permeable medium like clay, plastic shale and siltstone units. The best aquifers observed are the permeable sandstone units at the depth of 20m and fractured shale at 53m depth.

TABLE OF CONTENT

Content Page

Declaration i

Certification ii

Dedication iii

Acknowledgements iv

Table of content v

List of figures ix

List of tables x

List of plates xi

List of appendices xii

Abstract xiii

CHAPTER ONE – Introduction

1.1 Background of the study 1

1.2 Statement of the problem 3

1.3 Objectives of the study 3

1.4 Scope of the study 3

1.5 Study Area 4

1.5.1 Location 4

1.5.2 Physiography and drainage pattern 9

1.5.3 Climate and vegetation 9

1.5.4 Geologic setting 9

CHAPTER TWO – Review of literature

2.1 Salinity of groundwater 14

CHAPTER THREE – Research methodology

3.1 Field investigations/procedures 15

3.1.1 Water physical parameter 15

3.1.2 Static water levels 15

3.1.3 Water sampling 19

3.1.4 Vertical electric sounding 21

3.2 Laboratory procedures 21

3.2.1 Physical parameters 21

3.2.2 Chemical parameters 22

3.3 Data Analysis 25

3.3.1 Hydrochemical data 26

3.3 Geophysical data 31

CHAPTER FOUR – Results and Discussions

4.1 Physiochemical Parameters 47

4.1.2 Origin of ions 48

4.2 Hydrochemical facies/ water types 50

4.3 Mineral Saturation 56

4.4 Domestic and Irrigation Application 59

4.4.1 Drinking and Domestic use 59

4.2.2 Irrigation Applications 62

4.5 Geoelectric Studies 64

4.5.1 Uburu Geoelectric Model 68

4.5.2 Okposi Geoelectric Model 64

CHAPTER FIVE – Summary and Conclusion

5.1 Summary of the study 81

5.2 Conclusions 83

5.3 Recommendation 83

 References 84

 Appendix One A 89

Appendix One B 99