ENVIRONMENTAL IMPACT ASSESSMENT (EIA) OF KWARA STATE POLYTECHNIC DAM ENVIRONMENTAL IMPACT ASSESSMENT OF KWARA STATE POLYTECHNIC DAM

ENVIRONMENTAL IMPACT ASSESSMENT (EIA) OF KWARA STATE POLYTECHNIC DAM (FINAL REPORT)

ENVIRONMENTAL IMPACT ASSESSMENT OF KWARA STATE POLYTECHNIC DAM

By

Y.O. Oyebode, K.A. Dauda, M.R. Baiyeri, R.O. Asonibare, J.O. Abdulkadir, M.O. Idris, and W.S. Lawal

Project Report submitted to the Tertiary Education Trust (TET Fund) on the project entitled ‘’Environmental Impact Assessment of Kwara State Polytechnic Dam’’. Kwara State Polytechnic, Ilorin, Kwara State, Nigeria.

May, 2013

1

EXECUTIVE SUMMARY The Nigeria’s Environmental Impact Assessment (EIA) Decree provides that all projects of certain scales and locations must have an EIA study carried out so as to ensure the attainment of the country’s environmental objectives. Even though the construction of Kwara State Polytechnic Dam started long before the official promulgation of the EIA decree, it happens to fall within this project category. Land and water resources development are set out deliberately to ameliorate social, health and environmental situations, yet there are many serious problems suggesting the contrary. Many of these problems stem from inadequate x-ray of environmental impact of the project before commencement. This study was carried out by seven professionals from different area of specializations in the Polytechnic to assess the impact of Kwara State Polytechnic Dam on the local environment and vice versa, as well as to propose appropriate mitigation measures against the adverse impacts, enhancement measures for the positive impacts and monitoring plans. Kwara State Polytechnic Dam is located at the South East Wing of Kwara State Polytechnic Ilorin main campus, in Moro Local Government Area of Kwara State. It is approximately located between latitude 080 33 16.4 N, longitude 040 38 04.2 E and latitude 080 33 38.4 N and longitude 040 38 20.6 E of Greenwich Meridian.

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The project area is at kilometer 10 off old Ilorin- Jebba road. The Polytechnic is having boundary with Ilorin East Local Government. In addition to the above, the study also considered such broad issues such as: (i) The impact of fertilizer and other agro-chemicals on crop yields, fish population, weed and pest control, contamination of surface and groundwater. (ii) The reservoir operation, with emphasis on the extent and rate of sedimentation, control measures and effect of sedimentation on the reservoir operation. (iii) The impacts of irrigation on the water table and the effects of waterlogging and salinization on the irrigation practices. (iv) The major wild life species inhabiting the study area, including fish species in the reservoir and the impact of the project on their population and management. (v) The existing species of algae in and around the reservoir, the main agricultural and aquatic weed species present, the effects of their growth on the dam, as well as control measures required and cost implication. (vi) The epidemiological evidence of water related diseases, including a survey of water bodies associated with or found in or near the project area.

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The main findings of this research study are as follows: (a) Findings on irrigation system and impacts (i) The gross area of the operational land for farming in the project site is 8,638 m2. (ii) The effective rainfall (Re) values obtained for the months of August, October, November, 2012 were; 0.03mm, 1.90mm and 0.86mm, respectively, and for the month of January and February, 2013 were; 0.69mm and 0.99mm, respectively. (iii) The typical values of Net Irrigation Water Requirement (NIR) of the seven selected crops in the project area ranged from 0.05 to 0.67 mm/day and Gross Irrigation Water Requirement (GIR) ranged from 0.12 to 0.82 mm/day. (iv) Reservoir operation has not been defined by the Polytechnic Authority since the project had been handed over by the Contractor (John Stone Limited, Lagos) in 1977 to the Polytechnic Management. (iv) During the Rapid Rural Appraisal (RRA) trip, there is no particular cropping pattern adopted by the farmers, but a cropping pattern was derived by the team from the information given by farmers. (v) At the irrigated fields, the information gathered that the application of agro-chemicals by farmers which is said to be most useful is no longer available. The agro-chemicals are not readily available and affordable at the moment farmers use ash as alternative pesticides and insecticides, and animals manure in place of inorganic fertilizer.

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(vi) In the surrounding area of the dam (Northern, Southern and Eastern side) the water table has risen to about 20m below ground surface as a result of the presence of the reservoir. The future negative effect that should be prepared for, will take its tolls on the building foundations in the area, especially girl’s hostel. (vii) At the downstream area of the dam (Western side) there is no hydraulic conductivity between the reservoir behind the dam and the aquifer system. (viii) The water inside the dam remains odourless throughout the period of study. (ix) Water in the various locations in the dam maintains a Ph value in the range of 6.2 to 7.0 with no significant changes. (x) The variations of parameters such as nitrate, sulphate and Magnesium due to farming activities are not significantly affected. (xi) Alkalinity varies greatly downstream of the dam due to high level of domestic detergents from washing and bathing. (xii) In order to establish water quality studies, quantitative values from analysed chemical parameters were compared with Food and Agriculture Organisation of United Nations (FAO) and it is apparent that most of the parameters considered pose no significant threat to irrigation. (xiii) Sodium, Sulphate and Chloride are the parameters commonly found in the water samples and their values are far away from the recommended WHO’s standard. This indicated that there are no negative

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impacts due to these elements because their values obtained from the analyses are very small. (xiv) The chemical compositions of ground water (dug well and borehole) are not varying greatly from the dam water. This indicated that underground water in the study area is not significantly different from the water in the reservoir. The following mitigation measures are recommended on irrigation system and impacts: (i) Planting of Cashew or Cashew orchard should be established at the Northern side of the dam. (ii) Soil map and irrigation map at scale of 1:10,000 should be produced so as to produce a ‘crop rotation map’ for proper agricultural planning. (iii) A well equipped soil and water testing laboratory should be provided and operate for regular monitoring of soil and water in the study area (iv) The Polytechnic Authority should put in place an arrangement for control of usage of agro-chemicals in the project area. (v) Excessive irrigation of the soil profile should be avoided and specially drilled Piezometer and observation of ground water level in production wells should be part of the monitoring system. (vi) Employing an appropriate cropping pattern. (vii) Crop rotation and manuring should be adopted for the replacement of nutrients instead of fertilizer application. (viii) Cultivating crops with salinity tolerance.

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(ix) Avoiding the use of salty water for irrigation farming. (x) Using nitrogen fixing cover crops. (xi) Using organic fertilizer instead of inorganic fertilizers. (xii) Selecting chemicals with least potential negative impacts. (xiii) Limiting the pest and diseases infestations by the use of resistant species. (xiv) Controlling the use of chemicals generally in the dam area. (b) Findings on hydrographic analysis and reservoir sedimentation (i) The main causes of erosion in the project area are: light textured nature of the soil, de-vegetation of the land, continuous cultivation of land and land topography (sloppy land). (ii) The initial capacity of the dam since the time of construction (1975) was 2Mm3. The estimated capacity of the dam since 2005 was 1.9976 Mm3. The period from 2005 till September, 2012 is 7 years and the estimated volume as at 2012 which is the period of this research is 0.0178 Mm3. The difference in capacity within this period is 1.9644 Mm3 (1.9822Mm3 - 0.0178 Mm3). (iii) It was found that annual sedimentation rates ranged from 1% to 60% and about 40% of the dam was predicted to be completely filled with sediment within 25 years. (iv) The end products of the hydrographic survey are the available digital maps of the dam which include; Contour maps, Wireframe maps,

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Surface maps, and Vector direction maps of the dam using surface, boundary and bed coordinates. (v) The estimated volume of water in the dam during the first hydrographic survey in September, 2012 was

, the volume

of water during the second hydrographic survey in February, 2013 was and the volume difference is 2,613.5533 m. The following mitigation measures are recommended on erosion control and the rate sedimentation: (i) De-vegetation around the dam area should be discouraged to prevent the top soil from exposing the erosion. (ii) Extensive bush burning around the project area should be avoided. (iii) Removal of the total sediment load from the dam is currently required because the capacity of the dam has greatly reduced due to the sediment accumulation since the construction of the dam. (iv) Buffer zone of at least 4m round the dam should be established to protect the soil structure from being disturbed by human activities. (v) Proper operation and maintenance of this dam is required to ensure the integrity of environmental quality associated with the project. (vi) Monitoring and follow-up studies are needed to safeguard the environment as part of the routine operation of the dam.

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(vii) It is recommended that a continual post-implementation monitoring of the project on the environment should be made mandatory. (c) Findings on ecological environment and impacts (i) The all-season-wet environment due to impoundment of the dam has enhanced the growth and spread of agricultural weeds. These weeds compete with crops and serve as temporary hosts for insect pests, which transmitted diseases common to both the weeds and field crops. (ii) At the irrigation area, farmers have complained of fungi, tomato horn worm, aphids of peppers and caterpillars and these infections have brought about stunted growths of crops and poor harvests in some cases. Individual farmer usually brought their seeds and inputs from other places across the state. This implies that such inputs come along with their pests and diseases. (iii) The construction of the dam has brought about changes in the natural vegetation. The vegetation was submerged by reservoir, but also some percentage of project land was initially cleared to give way for construction of the dam. This single act has no doubt resulted in the loss of some of flora and fauna. (iv) Turbidity of the dam water appears to be low, except for the presence of submerged vegetation, which may tangle fishing nets or pose

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navigational hazards. Such submerged vegetation is also a loss in terms of forests and potential habitats. (v) Some of the larger species of wildlife face the danger of elimination because of the human interference and poaching due to hunters and farmers. (vi) Birds and aquatic life are increasing because of the new favourable environmental conditions from impounded reservoir. Certain species have been forced out of the area at the same time that certain species have either multiplied or have been joined by same species from elsewhere (vii) In the project area villagers have indicated the presence of pythons, which are alien to that geographic area. The emergence of Pythons may mean a corresponding reduction in the population of rats and Squirrels on which they prey. (viii) Frogs, Toads and Mosquitoes are reported to have increased in and around the dam. (ix) There are two categories of livestock rearers around the project area, namely; the villagers and Fulani nomads. Villagers keep mainly poultry, goats and sheep, while Fulani nomads keep cattle stocks.

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The following mitigation measures are recommended on ecological environment and impacts: (i) Carry out regular environmental reviews at every four years to be undertaken by the EIA research team, to assess and identify potential trouble spots within the project and to take immediate action on significant impacts before the cost of corrective measures. (ii) There is the need to educate the communities living around the project area on the values of resources conservation, maintenance culture and effective community participation for the overall sustainability of the project. (iii) Buffer strips of the proposed Cashew orchard (Plantation) be maintained by the Polytechnic along the Northern side of the reservoir. (iv) At the downstream of the dam, it is recommended that a recreation centre be developed which would contribute a sort of amenity resources for recreationists visiting the dam, while at the same time protecting the soils in this area from erosion. The Polytechnic Authority should explore the possibility of developing tourist facilities at the downstream end of the dam. (v) There is need to protect the few animal species of the area from the pressure of poaching through the enlightment programme to educate the people on the need to conserve the wildlife and fishery resources.

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(vi) The Polytechnic Authority should take the census of pastoralists within the project area with a view to identifying herds distribution, size, water requirements and migration routes. (vii) The egg pod survey of certain pests in the project area should be carried out to determine the population and viability of those eggs in soil that would emerged to attack crop seedlings. (viii) Monitoring of the pressure, distribution, biology and ecology of weeds, crop pests and diseases as well as forecast of outbreaks in fields and their immediate surrounding should be carried out by the Polytechnic Authority. (ix) Farmers should be taught to regulate input to and release of nutrients (Nitrogen, Phosphorus and Potassium), from fields so as to avoid excessive weeds growth in the reservoir. (x) The soil should be properly tilled to expose soil pests and pathogens to unfavourable weather conditions. (d) Summary of findings and recommendations on aquatic ecology and fisheries impacts (i) An intervention programme involving the training of trainers, seminars for water users, distributions of posters and handbills in the surrounding communities to enlighten them on the objectives and potentials of the dam project, the benefits and its hazard effects is very essential.

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(ii) An integrated approach involving experts in related disciplines e.g. Biologist, Agriculturalist, Irrigation and Water resources Engineer, Medical expert, Sociologist, GIS expert, Economist and Environmentalist who are familiar with adult training programme and capacity building will be required to carry out the intervention programme suggested above. (iii) Polytechnic Authority should constitute a committee of experts to look into the ways of improving the welfare of water users especially the farmers through the provision of some incentives e.g. Gloves, Boots to protect them from the risk of contacting water borne diseases during their operations. This will help in promoting a cordial relationship between the water users and the Polytechnic. (iv) The use of under sized net below 2 inches (5cm) for fishing in the dam should be discouraged to retain small size fishes within the reservoir. The indiscriminate catch-ability of traps on the fish population can be mitigated through training programme. (v) The use of toxic substances or chemicals including natural plants to catch fish should be discouraged and attract stiffer penalty. (vi) There is a need to stock the dam with fingerlings of different species to increase the population of fishes.

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(vii) Design diagram and documents of the dam were no longer available due to lack of proper documentation after which the project was handed over to the Polytechnic by the contractor. Redesigning of the dam is suggested to produce new diagram and documents for documentation. (e) Findings on socio-economic impacts and gender issue (i) The dam has brought in an increased prevalence of water-borne diseases. (ii) Majority of youth has moved to urban areas for better employment opportunity. (iii) Most of the women are quickly aged due to intensive farm activities. (iv) Financing children education to higher level has been found difficult because of subsistence nature of their agricultural practices. (v) While farming plays a dominant role in poverty alleviation and food security, it does not generate sufficient household income regardless of farm size. The following mitigation measures are recommended on socioeconomic impacts and gender issue: (i) Two mitigation measures on population are recommended, first, a workable enlightment programs on safe water use, and on physical and reproductive health education should be developed.

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(ii) The development of 100ha of irrigation farm for the Polytechnic should be accelerated. (iii) Reservoir fisheries development can be materially enhanced by removing from the dam annually for ten years a specified number of submerged trees which are at present constituting a major hindrance to economically viable fishing activities at the dam. (iv) The interaction between Kwara State Polytechnic and the communities within should be strengthened in order to know their areas and magnitudes of need. (f) Findings on health impacts and sanitation (i) The RRA exercise revealed that six diseases are prevalent to varying degrees and number of cases within the project area such as cholera (2), typhoid (53), bacillary dysentery (25), amoebiasis (30), ascaiasis (20) and yellow fever (2). (ii) The two diseases considered most serious in the study area are malaria and typhoid, with 1,600 cases and 54 cases, respectively. (iii) For the above mentioned diseases, the methods of control employed between year 2011 and 2012 were: health education on personal hygiene, distribution of mosquito nets to the people and expanded programme of immunization, and this was very effective.

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(iv) Oke-Apon community has a total population of about 50 inhabitants. The source of drinking water well and tap. Open dumping of refuse is practiced and majority of the people use bush for defecation and Malaria is a common disease which is prevalent throughout the year round. (v) Agbede is a community of about 70 in Population. Open dumping of refuse and bush for defecation are the methods used. Sources of water supply for drinking are open dug wells. People are commonly suffered from different diseases such as malaria and typhoid as well as problems arising from snake bite, leech and other biting insects. (vi) Water treatment plant has about ten Staff of the Polytechnic working there and the Source of water for drinking is from a tap located within the treatment plant. (vii) One of the female hostels is about 120m distance to the dam. The sources of water supply for drinking and domestic uses are borehole and tap. The common diseases are malaria, typhoid and occasionally diarrhea. Open dumping of refuse is practiced. Toilets (Septic tanks) are available in every block for defecation. (viii) Agricultural Engineering Experimental farm has the population of nine workers. The source of water for irrigation purpose is from the dam. Presently, there is no dug well, borehole or tap for drinking unless pure water/bottle water.

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Common diseases are malaria and typhoid as well as problems arising from bites by Leech, Snakes and other biting insects in the farm. Open dumping of refuse is also practiced and the farm workers use bush for defecation. The following mitigation measures are recommended on health and sanitation issues: (i) Periodic clearing and desilting of sediments and snails that can cause Schistomiasis be made as part of the operation and maintenance (O&M) activities of the dam. (ii) Stocking of the reservoir with fish and insects species that feed on the diseases-vector snail should be undertaken. (iii) Chemical control of the snail by using larvacides should be considered. (iv) Monitoring and evaluation of the dam should be done continually, in order to know the success and failures achieved, and this is the responsibility of the Polytechnic Authority. (v) Polytechnic Authority should handle disease surveillance and notification at every year with honesty. (vi) Health education should be communicated to create awareness on the damages of bathing, washing and drinking from the reservoir.

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(vii) Refuse disposal facilities should be provided for the people around the project area. (viii) Evaluation of silt materials deposited into the reservoir at every 5

year.

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ACKNOWLEDGEMENT We wish to express our sincere gratitude to the Tertiary Education Trust (TET) Fund for providing funding and support which made it possible for this study to be completed. Special appreciation is extended to the Rector, Kwara State Polytechnic, Ilorin; Alhaji Mas'ud Elelu, who provided critical guidance in the face of difficulties in the implementation of the research project. His understanding of the research environment in which the research team operated was inspirational to the team. The Deputy Rector Administration; Dr. F.A.J. Bello, the Deputy Rector Academic; Mr. J. A. Ajiboye, the Registrar; Mr. M.O. Salami and the Bursar; Alhaja A. Muhammed of the Kwara State Polytechnic, Ilorin, and the entire members of the Polytechnic Management for providing inputs during formal meetings and at an individual level provided information when requested to do so. The guidance provided by the Polytechnic Management, their patience and tolerance are highly appreciated. The support provided by Mr. M.A. Daramola, Director of the Academic Planning Unit (APU) of the Academic Planning Unit of the Kwara State Polytechnic, Ilorin, throughout the study is highly appreciated. As a member of Polytechnic Management, he provided specific comments that went beyond expectation.

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The staff of the Polytechnic Water Treatment Unit was instrumental in providing information and attending to the logistics such as keeping of research materials at the dam site. Special appreciation is extended to Mr. Akoda, aka. Baba Odo and his colleagues for their unwavering support. Special thanks to the Security Unit of the Kwara State Polytechnic for their support in securing our Canoe and Paddles on the project site throughout the period of this research. The completion of this study would not have been possible without the willingness of farmers at the various farms to provide the required information. We appreciate their sacrifice and contributions. Dr. M.O. Olabanji at Kwara State Polytechnic Medical Centre played a significant role in the data collection phase of the research. His participation during the period of research contributed in no small way to the successful completion of the study. Finally, we wish to acknowledge the contribution of the community leaders around the project area especially Agbede and Oke-Apon Village, for their role in providing necessary assistant during our Rapid Rural Appraisal (RRA) visit. Their good gesture made it possible for the research team to hold meetings with their community.

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TABLE OF CONTENT Cover page

i

Title page

ii

Executive Summary

iii

Acknowledgment

xx

Table of content

xxii

List of Tables

xxxi

List of Figures

xxxiv

List of Plates

xxxvi

Acronyms EIA Research Team

x1 x1iii

CHAPTER I 1. Introduction

1

1.1 Research objectives

4

1.2 Location of the study area

6

1.3 Scope of the study

7

21

CHAPTER II 2. Study approach and methodology

9

CHAPTER III 3. Physical characteristics of the project area

15

3.1 Climate

15

3.2 Geology and hydrogeology

15

3.3 Soils

16

3.4 Hydrology

18

3.5 Water availability and balance

18

3.5.1 Irrigation water requirement

19

3.5.2 Domestic raw water supply

19

3.5.3 Ecological requirement

19

3.6 Groundwater availability

20

CHAPTER IV 4. The irrigation system and impacts

21

4.1 Introduction

21

4.2 Water resources (dam)

24

22

4.3 Irrigation system

25

4.4 Water quality

26

4.5 Irrigation water requirements

28

4.6 Cropping pattern

36

4.7 Salinity

37

4.8 Agro-chemicals

38

4.9 Water table level

39

4.10 Water quality impacts

39

4.11 Ground water impacts

42

4.12 Hydrological impacts

42

4.13 Irrigation water and soil monitoring

43

4.14 Agro-chemical monitoring

44

4.15 Summary of findings and recommendations

44

4.16 Cost implication of mitigation measures and monitoring plans

46

CHAPTER V 5. Hydrographic analysis and reservoir sedimentation

47

5.1 Soil erosion

47

23

5.2 Rate of sedimentation

50

5.3 Perimeter survey of the project area

51

5.3.1 Reconnaissance survey

54

5.3.2 Beaconing

56

5.3.3 Line clearing

57

5.4 Data acquisition

57

5.4.1 Hydrographic surveying

58

5.4.2 Data sources

62

5.4.3 Materials and software selection

62

5.4.4 Control check

63

5.5 Geometric data acquisition

64

5.5.1 Traversing

64

5.5.2 Data processing

67

5.5.3 Downloading of data

68

5.5.4 Traverse adjustment

68

5.5.5 Graphic plotting of boundary

69

5.6 Products generation and analysis of results

70

24

5.6.1 Products generation

70

5.6.2 Analysis of results

76

5.6.3 Accuracy

76

5.6.4 Linear accuracy in perimeter traverse

76

5.6.4 Volume calculation

78

CHAPTER VI 6. Ecological Environment and impacts

90

6.1 Natural vegetation

91

6.2 Wildlife

92

6.3 Livestock management

92

6.4 Weeds

94

6.5 Pests and diseases

99

6.6 Ecological impacts

100

6.7 Mitigation measures (Recommendations)

102

CHAPTER VII 7. Aquatic ecology and fisheries impacts

105

7.1 Introduction

105

25

7.2 Fishes and fisheries activities

106

7.3 Observations

110

7.3.1 Water diseases and vectors

110

7.3.2 Mollusc

111

7.4 Water characteristics

112

7.5 Summary of findings and recommendations

113

CHAPTER VIII 8. Socio-economic impacts and gender issue

115

8.1 Introduction

115

8.2 Population

118

8.3 Employment

118

8.4 Settlement pattern

119

8.5 Existing crop production

120

8.6 Women’s participation

124

8.7 Summary of socio-economic impacts

125

8.8 Mitigations and enhancement measures

125

8.9 Monitoring plans

126

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8.10 Costs implication

127

CHAPTER IX 9. Health impacts and sanitation

128

9.1 Introduction

128

9.2 Water borne diseases

129

9.3 Field responses to questionnaire

130

9.4 Responses to RRA exercise

131

9.4.1 Oke-Apon community

131

9.4.2 Agbede community

132

9.4.3 Water treatment plant

132

9.4.4 Female hostel

133

9.4.5 Agricultural engineering experimental farm

133

9.5 Monitoring and follow-up studies

135

9.6 Mitigation measures

135

9.7 Monitoring plans

136

9.8 Cost implications of mitigation measures and monitoring plans

137

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CHAPTER X 10. Monitoring plans and cost estimates

138

10.1 Introduction

138

10.2 Monitoring plans

139

10.2.1 Physical environment

139

10.2.2 Terrestrial and aquatic ecologies

140

10.2.3 Health and sanitation issues

140

10.2.4 Socio-economic aspects

141

10.3 Operation, maintenance and monitoring cost of the dam

141

References

143

Appendix I

150

Appendix II

153

Appendix III

156

Appendix IV

157

Appendix V

162

Appendix VI

165

Appendix VII

175

28

Appendix VIII

177

Appendix IX

184

Appendix X

185

29

LIST OF TABLES S/N

TABLE

PAGE

1

Main features of the operation land

24

2

Reference crop Evapotranspiration

28

3

Crop Evapotranspiration of selected crops in the study area

30

4

Typical values of NIR and GIR for the selected crops in the study area

38

5

Cropping pattern

39

6

Salt tolerance of crops expressed as the ECe at 250 for yield potentials of 50%, 75%, 90% and 100% as compared to growth in normal soils

40

7

FAO water quality standards

42

8

WHO drinking water standards

44

9

Chemical compositions of ground water from borehole and dug well in the study area

10

45

Cost implication of mitigation measures and monitoring plans respect of soil and the use of agro-chemicals

49

30

11

Coordinates of control points

66

12

Angular and distance measurements for control checks

68

13

Back computation for control checks

69

14

Abstracts of coordinates of boundary Beacons

74

15

Backward computation of the perimeter survey

75

16

Coordinates of KWPT 702(closing station)

85

17

Comparing new and old coordinates

86

18

Distribution of Terrestrial weeds during wet season in August, 2012

19

103

Distribution of Terrestrial weeds during dry season in February, 2013

107

20

Pests and diseases identified on the field in the project area

109

21

Summary of ecological impacts on natural vegetation, wildlife, livestock and crops

22

111

Cost implication of mitigation measures and monitoring plans in respect of vegetation, wildlife, weeds and ecological imbalances

115

31

23

Physico-chemical characteristics of water in the project area

123

24

Existing cropping cycle in the project area

132

25

Cost implication of population and employment mitigation

26 27

measures and monitoring plans

138

Diseases and their corresponding host in the study area

142

Cost implications of mitigation measures and monitoring plans on health and sanitation

148

32

LIST OF FIGURES S/N

FIGURE

PAGE

1

Satellite imagery of Kwara State Polytechnic

7

2

Satellite imagery of Kwara Polytechnic dam

7

3

Plan showing the perimeter survey of the dam

57

4

A Typical survey Beacon

62

5

Types of Traverse

73

6

Contour map of the dam using boundary coordinates

78

7

Wireframe of the dam using boundary coordinates

78

8

Surface map of the dam using boundary coordinates

79

9

Vector Direction map of the dam using boundary coordinates

79

10

Contour map of the dam using boundary and bed coordinates

80

11

Wireframe of the dam using boundary and bed coordinates

81

12

Surface map using boundary and dam bed coordinates

82

13

Contour map using surface coordinates

83

14

Wireframe map using surface coordinates

83

15

Surface map using surface coordinates

84

33

16

The cross-sectional diagram of two reading

95

17

3-D diagram of the 1st reading

96

18

3-D diagram of the 2nd reading

97

19

1st and 2nd reading showing relationship of three longitudinal view

20

97

Representations of the 1st and 2nd readings showing DTM, Wireframe and contour map of the dam

98

34

LIST OF PLATES S/N

TITLE

PAGE

1

Photograph of EIA research team

2

Geophysical investigation at northern side of the dam

13

3

Geophysical investigation at eastern side of the dam

13

4

Geophysical investigation at southern side of the dam

14

5

Infiltration test on the field at southern side of the dam using a double ring infiltrometer

6

10

17

Soil sampling operation on the field at northern side of the dam in the study area

9

15

Soil sampling operation on the field at southern side of the dam in the study area

8

15

Infiltration test on the field at eastern side of the dam using a double ring infiltrometer

7

iii

Surface runoff around the project area Vegetable field owned by a farmer in the study area

18 19 25

35

11

Water sampling operation at southern side of the dam in the project area

12

Water sampling operation at downstream of the dam in the project area

13

19

54

Rill erosion has blocked one channel by sediment deposition at downstream of the dam

18

54

Rill erosion has gradually exposing underground pipeline in the study area

17

53

Rill erosion has gradually exposing the roots of trees after washing away of top in the study area

16

53

Rill erosion has gradually increasing in size at the downstream of the dam

15

26

Soil erosion encroaching on the main road of the Polytechnic at the downstream of the dam

14

26

55

Positioning of Canoe on the dam for hydrographic survey operation

64

Hydrographic survey of the dam by research team

65

36

20

Geospatial data capturing operation using GPS

65

21

A slow moving vessel during hydrographic survey of the dam

66

22

Hydrographic survey operation using a slow moving vessel

66

23

Pastoral Fulani’s and their herds around the dam

102

24

Cattle grazing at the northern side of the dam

102

25

Weed sampling operation during the wet season in the study area

26

107

Weed sampling operation around the dam during the dry season

109

27

A crest linear wooden canoe cruising along the dam

118

28

A fish caught from the dam (Citharinus Latus)

120

29

A fish caught from the dam (Clarias Anguillaris)

120

30

Different fish species caught from the dam

121

31

Fishes caught from the dam (Tilapia Zilli)

121

32

A fish caught from the dam (Tilapia Melanopleura)

122

33

Snail found around the project area (Bilinus species)

123

34

RRA interview with farmers using the questionnaire

129

37

35

RRA meeting with community leader at Oke-Apon

129

36

Children at their parents farm in the study area

132

37

A woman during farming operation in the study area

136

38

RRA with staff working at water treatment plant

144

39

RRA with workers at Agricultural Engineering Experimental Farm

145

38

ACRONYMS 1

KWPT

- Control Point

2

KC

- Crop Coefficient

3

Recci

- Reconnaissance

4

ETo

- Reference Evapotranspiration

5

EIA

- Environmental Impact Assessment

6

ETc

- Crop Evapotranspiration

7

UNCED -United Nations Conference on Sustainable Development

8

FAO

- Food and Agriculture Organization of United Nations

9

IAIA

- International Association for Impact Assessment

10

NAEP

- National Association of Environmental Professionals

11

LNRBDA - Lower Niger River Basin Development Authority

12

GIR

- Gross Irrigation Water Requirement

13

NIR

- Net Irrigation Water Requirement

14

Ieff

- Irrigation System Efficiency

15

Reff

- Effective Rainfall

16

Re

- Monthly Effective Rainfall

39

17

Rt

- Monthly Rainfall

18

D

- Net Depth of Irrigation

19

RRA

- Rapid Rural Appraisal

20

ECe

- Electrical Conductivity

21

SAR

- Sodium Adsorption Ratio

22

TDS

- Total Dissolved Solid

23

BOD

- Biological Oxygen Demand

24

COD

- Chemical Oxygen Demand

25

GIS

26

SURCON - Surveyor Council of Nigeria

27

R of O

- Right of Occupancy

28

C of O

- Certificate of Occupancy

29

ICID

- International Commission on Irrigation and Drainage

30

WHO

- World Health Organisation

31

O&M

- Operation and Maintenance

32

IITA

- Geographic Information System

- International Institute for Tropical Agriculture

40

33

SEERAD - Scottish Executive Environmental and Rural Affairs

Development 34

M.A.N.R

- Ministry of Agriculture and Natural Resources

35

APU

- Academic Planning Unit

EIA RESEARCH TEAM The following are the names, area of specializations and plate 1 showing the research team members. NAME

AREA OF SPECIALIZATION

1. Y.O. Oyebode

Irrigation and Drainage Engineering

2. K.A. Dauda

Water Resources Engineering

3. M.R. Baiyeri (Mrs.)

Soil and Water Conservation Engineering

4. J.O. Abdulkadir

Fisheries and Aquatic Ecology

5. W.S. Lawal

Agronomy

6. M.O. Idris

Epidemiology

7. R.O. Asonibare

Surveying and Geo-informatics

41

Plate 1: Photograph of EIA research team

42

CHAPTER ONE 1. INTRODUCTION The meaning of the term ‘environment’ is a ‘surrounding’. It is derived from the English word ‘environ’ which means ‘to surround’ or ‘to encircle’ (Barthwal, 2012). The environment consists of the components of the biosphere in which all life exists. Therefore, it encompasses the air, water, soil and related ecosystems. It also includes the flora, fauna and landscape as well as the natural and cultural heritage. Mainstreaming the environment also involves considering the human interactions and impacts on the biosphere, both positive and negative (ADB, 2003). One of the main achievements of the United Nations Conference on Sustainable Development (UNCED) dubbed the Earth Summit in Rio de Janeiro, Brazil in 1992 was the adoption of Agenda 21, a blueprint of environmental principles, policies and actions required to be taken by all countries into the 21st Century. A key supporting Instrument of Agenda 21 was the Rio Declaration on the Environment, a set of principles to guide environmental conduct. Therefore, the Federal Government of Nigeria enacted the Environmental Impact Assessment (EIA) Act No. 86 of 1992 as a demonstration of her commitment to the Rio Declaration (Ameyan, 2008). In Nigeria, Environmental Impact Assessment (EIA) must be carried out prior to the construction of a dam, irrigation and agricultural projects.

43

The Federal Ministry of Environment of Nigeria has laid down procedures for conducting the Environmental Impact Assessment, enforces the EIA Decree, sets out the requirements, and methods for conducting EIA (Biogeochem Associate Limited, 2004). The Nigeria’s Environmental Impact Assessment (EIA) Decree provides that all projects of certain scales and locations must have an EIA study carried out so as to ensure the attainment of the country’s environmental objectives. Even though the construction of Kwara State Polytechnic Dam started long before the official promulgation of the EIA decree, it happens to fall within this project category. EIA is a tool for decision-makers to identify potential environmental impacts of proposed project, to evaluate alternative approaches, and to design and incorporate appropriate prevention, mitigation, management and monitoring measures (FAO, 2011). It is a process comprising of a series of steps such as screening, scoping, prediction and mitigation, management and monitoring, and audit. The EIA process makes sure that environmental issues are raised when a project or plan is first discussed and that all concerns are addressed as a project gains momentum through to implementation (FAO, 1995). The eight guiding principles governing the entire process of EIA are: participation, transparency, certainty, accountability, credibility, costeffectiveness, flexibility and practicality (ESCAP, 2012).

44

Environmental assessment should lead to development decisions informed by knowledge of the range of potential environmental and social impact; directly, indirect, interactive and cumulative. Projects that move forward with little or no consideration of such impacts are leading to an increasing number of protests, in some cases violent (Jennifer, 2008). Land and water resources development are set out deliberately to ameliorate social, health and environmental situations, yet there are many serious problems suggesting the contrary. Many of these problems stem from inadequate x-ray of environmental impact of the project before commencement. There are various reasons why an evaluation of an existing project may be required. Increasingly, International funding agencies are recognizing the need to undertake evaluations, five or ten years after implementation, of projects which have been funded. Such evaluations are generally broad in scope, concentrating particularly on the physical and economic performance of the project, but most evaluations also include a requirement for an environmental assessment in their terms of reference (Wallingford, 1993). The environmental parameters to be evaluated may include biophysical, social and economic parameters. Major categories within a broad environmental checklist would include air, water, geology, soils, natural vegetation, wildlife and fisheries resources, heritage resources, land use

45

on adjoining property, community conditions with the potential to be affected by the environmental aspects of the project (Government of Saskatchewan, 2000). The main purpose of EIA is to facilitate the systematic consideration of environmental issues as part of development decision-making. It does so primarily by assembling and analyzing information on the potential environmental effects of specific development proposals and how they can be best prevented or mitigated (Hussein et al., 2004). There is a danger that the advances in environmental protection and enhancement achieved through the use of EIA in developed nations will prove inadequate on a global scale unless a similar level of attention is given to the application of EIA in developing countries (Christopher, 2003). Therefore, the purpose of this study is to evaluate the impact of Kwara State Polytechnic Dam on the local environment and vice versa. 1.1 RESEARCH OBJECTIVES The main objectives of this study are to assess the impact of Kwara State Polytechnic Dam on the local environment and vice versa, it will seek to identify and predict the ecological, health and social (environmental) consequences of the project and to plan appropriate mitigation measures to prevent, protect, reduce and possibly eliminate the present or potential problems and to enhance the positive ones.

46

The specific objectives are to determine: (i) the water table level around the project area through geophysical investigation. (ii) the physical, chemical and biological properties of the water in dam and through laboratory analysis of water samples. (iii) the physical and chemical characteristics properties of the soil around the project area. (iv) the present volume and area of the dam through hydrographic survey and analysis. (v) the types of terrestrial plants and animals in the project area. (vi) the aquatic plants and animals present in dam and those around the project area. (vii) the infiltration rates of the soil around the project area. (viii) the physical and chemical characteristics properties of the underground water around the project area.

47

1.2 LOCATION OF THE STUDY AREA The study area is located at the South East Wing of Kwara State Polytechnic Ilorin main campus, in Moro Local Government Area of Kwara State. It is approximately located between latitude 080 33 16.4 N, longitude 040 38 04.2 E and latitude 080 33 38.4 N and longitude 040 38 20.6 E of Greenwich Meridian. The project area is at kilometer 10 off old Ilorin- Jebba road. The Polytechnic entrance is between Elekoyangan and Oke-Ose village along the road. The Polytechnic land was carved out of the present Moro Local Government area of Kwara State. The Polytechnic is having boundary with Ilorin East Local Government. Figure 1 is the satellite imagery of the Polytechnic and Figure 2 is the imagery of the Polytechnic Dam.

Figure 1: Satellite imagery of Kwara State Polytechnic, Ilorin

48

Figure 2: Satellite Imagery of Kwara State Polytechnic Dam Source: www.Googlemap.com 1.3 SCOPE OF THE STUDY The scope of the study is to address the following specific aspects: (i) The impact of fertilizer and other agro-chemicals on crop yields, fish population, weed and pest control, contamination of surface and groundwater, as well as indirect environmental factors that may affect the quality of water entering the reservoir. (ii) The reservoir operation, with emphasis on the extent and rate of sedimentation, control measures and effect of sedimentation on the reservoir operation and comparison of initial design capacity with the present situation.

49

(iii) The impact and effects of irrigation on the water table and land subsidence and the effect of water-logging/ salinisation on the irrigation practices, including cause, estimation of yield reduction, area lost and control measures required. (iv) The major wild life species inhabiting the study area, including fish species in the reservoir and the impact of the project on their population and management, as well as crop pests and diseases associated with the irrigation practices, including the control measures and cost involved. (v) The existing species of algae in and around the reservoir, the main agricultural and aquatic weed species present, the effects of their growth on the dam, as well as control measures required and cost implication. (vi) The epidemiological evidence of water related diseases, with particular emphasis on schistosomiasis, malaria, sleeping sickness, guinea worn and water contact practices of the population around the project area and the effects of infections on farmers’ productivity as well as preventive measures required to reduce the incidence. In addition to the above, the study also considered the formulation of the necessary actions to be taken in order to mitigate against the present problems and risks identified, and suggested costs of the recommended plans and actions. It also drew up plans for monitoring further environmental changes around the project area and their cost estimates.

50

CHAPTER TWO 2. STUDY APPROACH AND METHODOLOGY The concern with methodology to address scientific and policy issues encountered in environmental impact assessment (EIA) has been ongoing since 1970. The attention given to this subject is illustrated by the inclusion of technical sessions on methods at most meetings sponsored by professional societies, such as the International Association for Impact Assessment (IAIA) and the National Association of Environmental Professionals (NAEP), (Larry and Barry, 1997). For quantitative as well as qualitative assessment of environmental impacts we need a strong database. The data will be concerned to various aspects of environment such as the physical environment; land, air, water, forests, noise, animals, birds, roads, buildings, e.t.c., social environment; people, their habits, culture, social customs, values, e.t.c., economic environment; employment/unemployment, economic activities, income levels, income distribution, taxes, government policies, e.t.c., and aesthetic environment; historical/archaeological monuments, places of tourists interest, temples and other religious places, scenic areas, and other natural landscapes, e.t.c. (Barthwal, 2012). The approach used in this study consisted of preliminary data collection, reconnaissance surveys, field studies and data collection. These were

51

followed by laboratory analyses of field samples, data interpretation and analysis and report writing. Before embarking on the field trip, all available data and basic information on the project were gathered. Such information included feasibility and design reports, photographs and location maps showing the key features of the project and served as a prerequisite for identification and establishment of suitable measures to mitigate the potential level of the adverse environmental impact of the project. The team members visited the project area and undertook a preliminary evaluation of the major aspects of the project to fine-tune strategies for further data collection and investigations. Further visits to the project location were also undertaken to collect field data and carry out studies of situations on the ground. All field activities were undertaken simultaneously. Water samples were collected in August, October and November, 2012, and January and February, 2013 at specific locations along the dam both at upstream, middle and downstream, and from domestic open well at the nearby village, borehole at girls’ hostel. With regards to soils, samples were also collected in August, October, November, 2012 and January and February, 2013. One sample point from the North, one from the South and two samples points from the Eastern side of the dam. The objective in the present EIA study is to

52

measure parameters that might indicate changes introduced as a result of the irrigation practices around the dam. Some physical characteristics of both soil samples and water samples in August, October, November, 2012 and January and February, 2013 were determined on the field while other physical as well as chemical and biological characteristics were determined from laboratory analyses. The parameters for evaluation included: texture, hydraulic conductivity, infiltration rates, water holding capacity, available moisture content, soil reaction, cation exchange capacity, total exchangeable bases, base saturation, electrical conductivity, available phosphorus, organic carbon, total nitrogen and organic matter. Geophysical investigation of groundwater was carried out in August, October, November, 2012 and January and February, 2013 to evaluate water table levels around the project area. One point each at Northern, Southern and two points at Eastern side of the dam, using resistivity meter. Plate 2, 3 and 4 show the geophysical investigation activities at Northern, Eastern and Southern side of the dam, respectively and the result of the investigations are presented in Appendix IV.

53

Plate 2: Geophysical Investigation at Northern side of the dam

Plate 3: Geophysical Investigation at Eastern side of the dam

54

Plate 4: Geophysical Investigation at Southern side of the dam

The infiltration tests were also conducted (plate 5 and 6) using double ring infiltrometer around the dam area (One point at Northern, Southern and Eastern), to investigate the infiltration rates of the soil in the project area and these were carried out in August, October, November, 2012 and January and February, 2013 and the results of the tests are presented in

55

Appendix VII. The estimated average infiltration rates of the soils at the North, South and Eastern side of the dam are 907.8mm/hr, 488.8mm/hr and 911.1mm/hr, respectively.

Plate 5: Infiltration Test on the field at Southern side of the dam using a double ring Infiltrometer

Plate 6: Infiltration Test on the field at Eastern side of the dam using a double ring Infiltrometer

56

CHAPTER THREE 3. PHYSICAL CHARACTERISTICS OF THE PROJECT AREA 3.1 CLIMATE The climate of the project area can be divided into two distinctive seasons namely: a rainy season from April to October and a dry season from November to March. The rainy season is traditionally the farming period. The annual average rainfall of the region is about 1503 mm. During this period, average precipitation far exceeds potential evaporation in most of the years. Average annual relative humidity in the region is 70.73%. Highest annual mean monthly temperature is 31.52 oC while the lowest is 29.62 oC. Eighteen years of daily maximum and minimum temperature data from Lower River Niger Development Authority Meteorological station were utilized for this project. 3.2 GEOLOGY AND HYDROGEOLOGY Geologically, the project area is underlain by rocks of the crystalline Nigeria Basement complex, principal among which are granites and gneiss. These rocks were emplaced in Precambrian times and have over time been subjected to tectonic activities characterized by large changes in temperature and pressure resulting in features like joints, faults and fractures within the Basement complex rocks. Such fractures are those that influence the groundwater in crystalline rocks especially if they exist at depth and are over laid by a thick superficial cover (overburden).

57

Although there are no visible outcrops in the area worked upon, outcrops exist in the adjoining areas such as Kwara Polytechnic-Oke Oyi and Kwara Polytechnic –Oloru roads. This is clear index to the fact that on a regional projection such rocks exist at depth beneath the thick superficial cover that is predominant in the area. This is of immense hydro-geological interest in this investigation. 3.3 SOILS The soils in the project area have undergone repeated cycles of pedogenesis under varying climatic conditions in geologic times. This situation allows for soil classification in the area mainly on the basis of pedogenetic processes. Three types of soil were recognized, namely: Lithosols, Cambisols, and Alluvial soils. Plate 7 and 8 show the soil sampling operations on the field using soil auger at Southern and Northern side of the dam, respectively. The results of the chemical analyses through August, October, and November, 2012 and January and February, 2013, are presented in Appendix I.

58

Plate 7: Soil sampling operation on the field at Southern side of the dam in the study area.

Plate 8: Soil sampling operation on the field at Northern side of the dam in the study area.

59

3.4 HYDROLOGY The inflow of water into Kwara State Polytechnic Dam depends to a large extent on the contribution of the original river tributary upon which the dam was built, seasonal rainfall and to a less extent on the runoff from immediate surroundings of the dam. Plate 9 shows the surface runoff around the project area. The average run-off coefficient of the catchment area of the dam throughout the period of observation (JanuarySeptember) has been estimated as 3.85 in the study conducted (Isiaka, 2000).

Plate 9: Surface run-off around the project area 3.5 WATER AVAILABILTY AND BALANCE Irrigated agriculture in the project area is largely dependent on the reliability and adequacy of its water supply of usable quality. Sound planning of water budget ensures that efficient utilization of available

60

water resources remains protected from environmental pollution. The total water demand from Kwara State Polytechnic Dam will include irrigation water requirement, raw water collected by the villagers for domestic use, treated water supply to the offices, hostels, staff quarters, medical center, staff canteen and ecological water requirement. 3.5.1 Irrigation Water Requirement Blaney-Criddle method was used for estimating the crop water requirement of various crops grown in the project area. The individual crop water requirements as well as future cropping patterns were considered in evaluating the total crop water requirement for the project area. 3.5.2 Domestic Raw Water Supply The Kwara State Polytechnic Dam is intended to supply raw water to the Polytechnic community, Surrounding villages and the downstream users, with priority for irrigation water requirement. 3.5.3 Ecological Requirement It is extremely difficult to determine the water requirements of wildlife in the project area because very little or no information is available in the literature. It is suggested that a key factor for sustaining the local ecosystem in terms of water requirement is to maintain the downstream release of 25% of dam capacity. This suggestion is informed by the fact that ecological requirement should in fact include downstream release for livestock, wildlife, forestry and maintenance of biodiversity.

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3.6 GROUNDWATER AVAILABILITY The communities around the project area relied much on functional wells and boreholes for their domestic water supply. The relationship of perennial streams and springs with the groundwater flow characteristics of the project area could not be ascertained for lack of records.

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CHAPTER FOUR 4. THE IRRIGATION SYSTEM AND IMPACTS 4.1 INTRODUCTION The benefits of irrigation have resulted in lower food prices, higher employment and more rapid agricultural and economic development. The spread of irrigation has been a key factor behind the near tripling of global grain production since 1950. But irrigation and water resources development can also cause social and environmental problems (Claudio, 1996). Irrigation development brings about changes in soil physical and chemical characteristic properties. The impacts of irrigation on soils vary, depending on the inherent soil characteristics, irrigation water quality and the irrigation methods employed. Soil contamination and soil erosion could result from removal of topsoil (and nutrients) in land clearance and from excessive water use on poorly structured and sandy soils. These give a general loss of productivity as a result of progressive deterioration of soil fertility. The increasing use of fertilizers and changes in irrigation water quality brings about changes in cation exchange capacity and the nutrient status of the soil (Afremedev Consultancy Services Limited, 2000). A variety of measures is available for mitigating the negative impacts of irrigation and enhancing environmental benefits where these are achievable.

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Some of these are technical or site specific but many could also involve policy changes and adjustments to the institutional management of water at national and regional levels (David et al., 2000). In this study, three land use characteristics were identified such as nonirrigated, irrigated and under-developed fields. Four observation points were located during the field work, the first point was at the Northern side of the dam, the second point at the Southern side of the dam, the third and fourth points were both located at the Eastern side of the dam (Upstream). Soil physical properties were analysed in the laboratory for parameters such as particle size distribution (texture), moisture contents, hydraulic conductivity and infiltration rate using double ring Infiltrometer on the field. Chemical properties were also analysed for parameters such as Ph in water, Ph in potassium chloride, electrical conductivity, exchangeable cations (Mg2+, Na+, Mg2+, K+, SO4+, and Cl), exchangeable sodium, exchangeable acidity, exchangeable phosphorus and total ammonium nitrogen. Continuous cultivation under irrigation leads to a progressive breakdown of soil into finer particles, such as silt and very fine sand that are lost to erosion by irrigation water. The following methods were employed for the soil analyses: (i)The particle size analysis was done by hydrometer method, employing sodium hexametaphosphate {(Na ( HPO4)6) calgon as the dispersing agent.

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(ii) Organic carbon by using Walkey Black method, involving oxidation of organic matter with potassium chromate and sulphuric acid. From the organic carbon data, organic matter content was then calculated. (iii) Total Nitrogen was determined by modified micro Kjedahl method. (iv) The PH by using glass electrode PH meter in soil-water and soil-KCL filtrates. (v) Available phosphorus by Bray I method. (vi) The exchangeable acidity by titrating filtrates of soil samples treated with potassium chloride and sodium hydroxide and phenolphthalein as indicator. (vii) The exchangeable cations by flame analyser after extraction with neutral ammonium acetate. Results of the soil particle size analysis indicated that the soils of the project area are generally very light-textured with sand percentage averaging more than 80% and are presented in Appendix V. The available soil moisture contents around the project area were determined by oven drying method and the results are presented in Appendix VI. Soil reactions also vary from moderately acid (Ph: 6.1-5.6) to slightly acid (Ph: 7.0-6.7), this indicated that soil acidity factors are presently not pronounced in the study area. The dominant cations are Na, K, Mg, P, and the soil fertility status of the study area is very poor with CEC

65

averaging 0.0 cmol/kg of soil. The areas under irrigation presently show more nutrient cations than other areas. This can be attributed to the effect of added organic and inorganic fertilizers. The results of soil analyses for the month of August, October and November, 2012 and January and February, 2013 are presented in Appendix I. 4.2 WATER RESORCES (DAM) The main source of water for irrigation practices around the project area as well as potential source of raw water supply to the entire community is the Kwara State Polytechnic Dam and it is an earth-fill dam located at Kwara State Polytechnic permanent site which was constructed by John Stone Construction Company Limited in 1975 and commissioned to operation in 1977. The main dam consists of an earth-fill embankment approximately 236.98m long, about 70m wide, with a maximum height of 4.3 m. The dam has been built on top of a foundation of up to 40m of alluvial sand. The embankment consists of a thick impervious core with transition zones, coarse earth-fill shells and an outer protective layer. The intake works for raw water to treatment plant is located within the operational section and consists of blue double cell plastic drums with concrete gravity. The water is pumped to the treatment plant for treatment before being distributed within the Polytechnic community.

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4.3 IRRIGATION SYSTEM Irrigation water is being supplied from the upstream of the dam to Agricultural Engineering and Water Resources experimental farm by pump through the main pipe, laterals and distributaries’ pipes. Water is collected from the Southern side of the dam for irrigation practices by some farmers around the project area, using buckets and watering cans. The main features of the operation lands are shown in Table 1 and Plate 10 is a vegetable farm owned by one farmer in the study area. Table 1: Main features of the operation land Operation Land

Description

Size ( L x B)

North

Vegetative area

236.9 x 20 = 4738 m2

South

Farmers’ area

210 x 15

=3150 m2

East

Experimental farm area

25 x 30

=750 m2

Gross Area

= 8638 m2

Irrigation system checklist has been developed and administered to a Senior Irrigation Officer from the department of Agricultural Engineering and Water Resources, Institute of Technology, Kwara State Polytechnic, Ilorin, in order to gather some information regarding the irrigation practice in the study area (Appendix VII).

67

Plate 10: A vegetable field owned by one farmer in the study area 4.4 WATER QUALITY Water samples were collected both from surface and groundwater sources for quality analysis (plate 11 and 12). One sample from the upstream, one from the middle and one from downstream of the dam, in August, October, November, 2012, and January and February, 2013. One sample from borehole and one sample from the open well around the project area, in August, October, November 2012, and January and February, 2013. The analytical results of the soil samples are presented in Appendix II. This is to characterize the physico-chemical parameters in the reservoir and the surrounding area.

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Plate 11: Water sampling operation at Southern side of the dam in the project area

Plate 12: Water sampling operation at downstream of the dam in the project area

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4.5 IRRIGATION WATER REQUIREMENT (i) Reference Crop Evapotranspiration (ETO) Reference Crop Evapotranspiration (ETo) is the rate at which water if available, would be removed from the soil and plant surfaces of a specific crop arbitrary called a reference crop (Jensen et al., 1990). The height of the grass reference should be at least 8cm and not more than 15cm (Doorenbos and Pruitt, 1977). There are three empirical methods to estimate reference crop Evapotranspiration (ETo) and these are; temperature based methods, radiation based methods and combination based methods (Jacob and Satti, 2001). Among these approaches, a temperature based method was chosen, which is the Blaney-Criddle model. Eighteen years record of climatic data from Lower Niger River Basin Development Authority Meteorological Station (LNRBDA, 2012), was used in Blaney-Criddle equation to compute the crop water requirements. The Blaney-Criddle model is of the form {Soil Conservation Services (SCS), 1995}. ETo = p (0.46 T + 8)

(1)

Where; ETo = Reference Crop Evapotranspiration, mm/day T = Mean daily temperature in 0C over the month considered p = Mean daily percentage of total annual daytime hours

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Table 2 summarized the climatic data used and the reference crop Evapotranspiration computed. Table 2: Reference Crop Evapotranspiration (ETo) Year

Min. Temp. OC

Max. Temp. OC

ETo mm/day

1995

13.01

17.45

4.05

1996

15.77

24.17

4.64

1997

20.68

24.35

6.82

1998

21.04

31.70

5.44

1999

22.29

32.21

5.54

2000

21.40

32.84

5.53

2001

22.95

32.90

5.63

2002

23.70

33.03

5.68

2003

15.67

22.04

4.50

2004

23.34

30.84

5.52

2005

22.98

33.60

5.67

2006

23.19

32.61

5.63

2007

21.67

32.58

5.53

2008

22.03

31.86

5.51

2009

22.52

31.78

5.53

2010

21.58

31.86

5.48

2011

21.56

30.18

5.50

2012

21.57

31.02

5.49

(ii) Crop Evapotranspiration (ETC) The Crop Evapotranspiration (ETc) is the amount of water needed by a certain crop to grow optimally and it is mainly depended on the climate, crop type and the growth stage of the crop (FAO, 1986). The reference crop is often coupled with crop coefficient (Kc) to determine the Crop

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Evapotranspiration (ETc). The equation for the computation of Crop Evapotranspiration (ETc) is given by; ETc = ETo x Kc

(2)

Where; ETc = Crop Evapotranspiration, mm/day ETo = Reference Crop Evapotranspiration, mm/day (Kc) = Crop Coefficient Source: FAO (1986) Typical values of crop Evapotranspiration (ETc) obtained are shown in Table 3 for Vegetable, Tomato, Maize, Onion, Pepper, Sorghum and Groundnut. These values are useful as a guide in selecting the amount and frequency of irrigation of a particular crop by farmers in the project area.

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Table 3: Crop Evapotranspiration (ETc) of selected crops in the study area. (1) Vegetables (Average Kc = 0.86) Year

Min. Temp. OC

Max. Temp. OC

ETo mm/day

ETc mm/day

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

13.01 15.77 20.68 21.04 22.29 21.40 22.95 23.70 15.67 23.34 22.98 23.19 21.67 22.03 22.52 21.58 21.56 21.57

17.45 24.17 24.35 31.70 32.21 32.84 32.90 33.03 22.04 30.84 33.60 32.61 32.58 31.86 31.78 31.86 30.18 31.02

4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

0.32 0.37 0.55 0.44 0.44 0.44 0.45 0.45 0.36 0.44 0.45 0.44 0.44 0.44 0.44 0.44 0.44 0.44

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(2) Tomato (Average Kc = 0.79) Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Min. Temp. OC 13.01 15.77 20.68 21.04 22.29 21.40 22.95 23.70 15.67 23.34 22.98 23.19 21.67 22.03 22.52 21.58 21.56 21.57

Max. Temp. OC 17.45 24.17 24.35 31.70 32.21 32.84 32.90 33.03 22.04 30.84 33.60 32.61 32.58 31.86 31.78 31.86 30.18 31.02

ETo mm/day 4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

ETc mm/day 3.20 3.67 4.60 4.30 4.38 4.37 4.45 4.49 3.56 4.36 4.48 4.48 4.37 4.35 4.37 4.33 4.35 4.34

(3) Maize (Average Kc = 0.88) Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Min. Temp. OC 13.01 15.77 20.68 21.04 22.29 21.40 22.95 23.70 15.67 23.34 22.98 23.19 21.67 22.03 22.52 21.58 21.56 21.57

Max. Temp. OC 17.45 24.17 24.35 31.70 32.21 32.84 32.90 33.03 22.04 30.84 33.60 32.61 32.58 31.86 31.78 31.86 30.18 31.02

ETo mm/day 4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

ETc mm/day 3.40 3.90 5.73 4.57 4.65 4.65 4.73 4.77 3.78 4.64 4.76 4.73 4.65 4.63 4.65 4.60 4.62 4.61

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(4) Onion (Average Kc = 0.80) Year 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Min. Temp. OC 13.01 15.77 20.68 21.04 22.29 21.40 22.95 23.70 15.67 23.34 22.98 23.19 21.67 22.03 22.52 21.58 21.56 21.57

Max. Temp. OC 17.45 24.17 24.35 31.70 32.21 32.84 32.90 33.03 22.04 30.84 33.60 32.61 32.58 31.86 31.78 31.86 30.18 31.02

ETo mm/day 4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

ETc mm/day 3.24 3.71 5.46 4.35 4.43 4.42 4.50 4.54 3.60 4.42 4.54 4.50 4.42 4.41 4.42 4.38 4.40 4.39

(5) Pepper (Average Kc = 0.75) Year Min. Temp. OC Max. Temp. OC 1995 13.01 17.45 1996 15.77 24.17 1997 20.68 24.35 1998 21.04 31.70 1999 22.29 32.21 2000 21.40 32.84 2001 22.95 32.90 2002 23.70 33.03 2003 15.67 22.04 2004 23.34 30.84 2005 22.98 33.60 2006 23.19 32.61 2007 21.67 32.58 2008 22.03 31.86 2009 22.52 31.78 2010 21.58 31.86 2011 21.56 30.18 2012 21.57 31.02

ETo mm/day 4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

ETc mm/day 3.04 3.48 5.12 4.08 4.16 4.15 4.22 4.26 3.38 4.14 4.25 4.22 4.15 4.13 4.15 4.11 4.13 4.12

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(6) Sorghum (Average Kc = 0.71) Year Min. Temp. OC Max. Temp. OC

ETo mm/day

ETc mm/day

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

3.59 3.29 4.84 3.86 3.93 3.93 4.00 4.03 3.20 3.92 4.03 4.00 3.93 3.91 3.93 3.89 4.13 3.90

ETo mm/day 4.05 4.64 6.82 5.44 5.54 5.53 5.63 5.68 4.50 5.52 5.67 5.63 5.53 5.51 5.53 5.48 5.50 5.49

ETc mm/day 3.00 3.43 5.05 4.03 4.10 4.09 4.17 4.20 3.33 4.09 4.20 4.17 4.09 4.08 4.09 4.06 4.07 3.90

13.01 15.77 20.68 21.04 22.29 21.40 22.95 23.70 15.67 23.34 22.98 23.19 21.67 22.03 22.52 21.58 21.56 21.57

17.45 24.17 24.35 31.70 32.21 32.84 32.90 33.03 22.04 30.84 33.60 32.61 32.58 31.86 31.78 31.86 30.18 31.02

(7) Groundnut (Average Kc = 0.74) Year Min. Temp. OC Max. Temp. OC 1995 13.01 17.45 1996 15.77 24.17 1997 20.68 24.35 1998 21.04 31.70 1999 22.29 32.21 2000 21.40 32.84 2001 22.95 32.90 2002 23.70 33.03 2003 15.67 22.04 2004 23.34 30.84 2005 22.98 33.60 2006 23.19 32.61 2007 21.67 32.58 2008 22.03 31.86 2009 22.52 31.78 2010 21.58 31.86 2011 21.56 30.18 2012 21.57 31.02

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(iii) Net Irrigation Water Requirements (NIR) The average net irrigation water requirement is the difference between the crop water requirement (ETC) and the effective rainfall (Reff). Thus: NIR= Crop Water Requirement (ETC) – Effective Rainfall (Reff)

(4)

Source: Jacob and Satti (2001) The effective rainfall was calculated using an empirical equation for the one-dimensional irrigation model developed by Soil Conservation Service (SCS) of the United States. The working equation is given by: Re= (0.70917 x Rt

0.82416

– 0.11556) (10

0.024264 x U)

(5)

Where; Re= monthly effective rainfall depth, inches Rt= monthly rainfall, inches U= crop Evapotranspiration (ETo) predicted by Blaney Criddle method (0.531747 + 0.295164 x D – 0.057697 x D2 + 0.003804 x D3) and D= Net depth of irrigation, inches Source: Jacob and Satti (2001) The effective rainfall (Re) values obtained for the months of August, October, November, 2012 were; 0.03mm, 1.90mm and 0.86mm, respectively, and for the month of January and February, 2013 were; 0.69mm and 0.99mm, respectively.

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(iv) Gross Irrigation Water Requirements (GIR) The gross irrigation water requirement was calculated by dividing the net supplemental irrigation values obtained by the irrigation system efficiency of 50%. Thus: GIR = NIR/Ieff

(6)

Where; GIR= Gross Irrigation Water Requirement (mm/day) NIR= Net Irrigation Water Requirement Ieff = Irrigation System Efficiency Source: Jacob and Satti (2001) Typical values of NIR and GIR obtained were shown in Table 4 for the selected crops. Table 4: Typical Values of NIR and GIR for selected crops in the area S/N

Crop

NIR

GIR (mm/day)

1 2 3 4 5 6 7

Vegetables Tomato Maize Onion Pepper Sorghum Groundnut

0.17 0.05 0.53 0.09 0.45 0.67 0.60

0.23 0.71 0.12 0.82 0.76 0.29 0.66

4.6 CROPPING PATTERN During the Rapid Rural Appraisal (RRA) trip, the cropping pattern derived from the information given by farmers is presented in Table 5. There is no particular cropping pattern adopted, but the farmers are at

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liberty to design their own cropping pattern. However, a cropping pattern was designed for the purpose of computing crop water requirement in consultation with the farmers. Table 5: Cropping pattern S/N

Crop

Area (%)

Planting date

Harvesting date

1 2 3 4 5 6 7

Beans Tomato Maize Onion Pepper Sorghum Groundnut

20 5 30 5 10 20 10

17/04 06/10 28/04 10/11 08/11 09/05 05/04 Dates (Day/Month)

10/07 20/03 05/09 15/05 08/03 28/10 25/07 At 100% intensity

4.7 SALINITY Continuous use of irrigation water containing excessive quantities of salts usually gives rise to soil salinity and alkalinity. Salinity effects on plants are measured by the electrical conductivity and this can be a detrimental to plant growth as shown in Table 6. At the end of this study, it was observed that none of water samples analyzed poses any danger of salinization to the irrigated land in the study area. The results of water analyses also revealed that the Ph of all samples fall in neutral zone and Sodium ion concentration is very low to cause salinity in the study area. Therefore, hazards due to salinity, alkalinity and acidity are unlikely to occur now in the study area.

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Table 6: Salt tolerance of crops expressed as the ECe at 25o for yield potentials of 50%, 75%, 90% and 100% as compared to growth in normal soils S/N

Crop

1 2 3 4

Maize Beans Tomato Onion

Yield potential (%) and ECe (mmhos/cm) No yield 50% 75% 90% 100% 10.0 7.9 3.8 2.5 1.7 6.5 3.6 2.3 1.5 1.0 12.5 7.6 5.0 3.5 2.5 7.5 4.9 2.8 1.8 1.2

Source: FAO (1979) 4.8 AGRO-CHEMICALS At the irrigated fields, the information gathered that the application of agro-chemicals by farmers which is said to be most useful is no longer available. The agro-chemicals are not readily available and affordable at the moment; therefore, farmers use ash as alternative pesticides and insecticides, and animals manure in place of inorganic fertilizer. The use of agro-chemicals i.e. inorganic fertilizers enriches surface waters with nitrogen or Phosphorus that will promote algae growth. Therefore, the use of such materials should be accompanied with proper training and extension regarding the selection of the correct chemical, its dosage, time of application and possible residual effect. It is hoped that with improved economic situation and more enlightment, farmers would be able to afford and apply the correct doses at the right times.

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4.9 WATER TABLE LEVEL In the surrounding area of the dam (Northern, Southern and Eastern side) the water table had risen to about 20m below ground surface as a result of the presence of the reservoir. However, the development of this dam appears beneficial to the people initially, to the present time as far as domestic water supply was concerned. The future negative effect that should be prepared for, will take its tolls on the building foundations in the area, especially girl’s hostel. At the downstream area of the dam (Western side) there is no hydraulic conductivity between the reservoir behind the dam and the aquifer system. The results of Geophysical investigation through the month of August, October and November, 2012, and January and February, 2013 are presented in Appendix IV. 4.10 WATER QUALITY IMPACTS The following observations were made from the compared mean values obtained for the months of August, October, November 2012, and January and February 2013, from the analyses: (i) The water remains odourless. (ii) Water in the various locations maintains a Ph value in the range of 6.2 to 7.0 with no significant changes. (iii) The variations of parameters such as nitrate, sulphate and Magnesium due to farming activities are not significantly affected. (iv) Alkalinity varies greatly downstream due to high level of domestic detergents from washing and bathing.

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Table 7: FAO Water Quality standards S/N

1 2 3 4 5 6 7

Parameters

Salinity (ms/m) SAR(me/l) Chloride (mg/l) NO3-N (mg/l) HCO3 (mg/l) TDS (mg/l) Boron (mg/l)

Level of problem

Remark

None

Moderate

Severe

3.0

Low Moderate High Low Moderate Low None

Source: FAO (1985) SAR means sodium adsorption ratio and was calculated using the equation proposed by FAO (1985): SAR =

(7)

Where, Na, Ca and Mg are sodium, calcium and magnesium in me/l, respectively. In order to establish water quality studies, quantitative values from analysed chemical parameters were compared with Food and Agriculture Organisation of United Nations (FAO) (Table 7). It is apparent that most of the parameters considered pose no significant threat to irrigation. The results of water analyses through August, October and November, 2012 and January and February, 2013 are presented in Appendix II. Similarly, the results of the water samples were also compared with the World Health Organization Standard (WHO) in Table 8.

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Table 8: WHO drinking water standard S/N 1 2

Parameter/Substance Aluminum Ammonia

Symbol Al NH3

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Antinomy Arsenic Barium Boron Cadmium Chloride Copper Cyanide Fluoride Lead Manganese Mercury Nickel Nitrate Sodium Sulphate Uranium Zinc

Sb As Ba B Cd Cl Cu CN F Pb Mn Hg Ni NO3 Na SO4 U Zn

Health based standard 0.2mg/l