Design Of A Small Scale Irrigation Scheme For Arechek Village In Napak District, Uganda

ABSTRACT Irrigation is a technology that ensures a good soil-moisture balance resulting into a good environment for crop growth for the well-established irrigation systems This project covered the different sections which included the site visits, desk studies, topographic and geographic studies, nature of the land. The specific objective entailed the determination of pertinent parameters for the design, coming up with the system layout to ensure every farmer gets water and sizing of the pipelines. In addition, this project covered the design of laterals, mainlines, sub mainlines and the pump. The crop water requirement for the crops selected was estimated using the Penman Monteith method after incorporating CLIMWAT data into CROPWAT using climatic data for Moroto station and was found to be 5.22mm/day for cabbages. Irrigation scheduling and frequency have been calculated based on the CWR. Irrigation frequency was found to be 3 days and time of operation of system was found to be .2hours The layout of the area was drawn from Global Earth guided by topography, land use and existing infrastructure. Blocking of the area was done (dividing the area into manageable portions) for supply of water through distribution lines. The conveyance was designed for a total length of 150m with a diameter of 75mm, the mainline runs for 230m with diameter of 90mm.Each infield system has lateral line which serves 83 emitters on a row and this does for all, to cover 50m long and 50 m wide for all the 12plots of land (8.2acres of land).The application rate for the system was found to be 5.54mm/hr with an irrigation interval of 3days. In addition, the storage tank (reservoir) was to be 138m3 and the pump was found to be with a 5KWHpower to be able to pump water through the suction lift to the storage (reservoir tanks)

TABLE OF CONTENTS

DECLARATION.................................................................................................i

APPROVAL......................................................................................................ii

DEDICATION................................................................................................. iii

ACKNOWLEDGEMENT.....................................................................................iv

ABSTRACT......................................................................................................v

TABLE OF CONTENTS..................................................................................... vi

LIST OF FIGURES...........................................................................................ix

LIST OF TABLES .............................................................................................x

LIST OF ABBREVIATIONS ............................................................................... xi

CHAPTER ONE:INTRODUCTION ...............................................................1

1.1 Background ................................................................................................................ 1

1.2 Problem statement.................................................................................................... 2

1.3 Significance ................................................................................................................ 2

1.4 Objectives’ of the study ............................................................................................ 3

1.5 Scopes......................................................................................................................... 3

1.5.1 Geographical scope and site location ........................................................3

1.5.2 Content scope ........................................................................................4

1. 5.3 Time scope ...........................................................................................5

CHAPTER TWO: LITERATURE REVIEW.....................................................6

2.0 Review on the irrigation ......................................................................................... 6

2.1 Irrigation process ......................................................................................8

2.1.1 FAO Penman-Monteith method ................................................................8

2.1.2 Pan Evaporation method....................................................................................... 9

2.1.3 Blanely-Criddle Method.......................................................................................... 9

2.1.4 Evaporation Pan Method ..................................................................................... 10

2.2 Net depth of water application..................................................................10

2.3 Irrigation frequency................................................................................................. 11

2.4 Constant Head Method ............................................................................11

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2.5 Gross depth of water application........................................................................... 12

2.6 System Capacity ...................................................................................................... 12

2.7 Topography .............................................................................................................. 12

2.8 Set time (Ts)............................................................................................................ 13

2.9 Slope percent Soil Moisture Content..........................................................13

2.10 Soil Moisture Potential .......................................................................................... 13

2.11 Pipe size determination......................................................................................... 14

2.12 Total Head Requirements..................................................................................... 15

2.13 Pump selection....................................................................................................... 16

2.14 Components of drip irrigation system................................................................. 17

2.15 Conveyance system............................................................................................... 19

CHAPTER THREE: METHODOLOGY .........................................................23

3.1 Review of literature ................................................................................................. 23

3.2 Crop water requirement estimation ...................................................................... 23

3.3 Determination of the soil characteristics, moisture content............................... 23

3.4 Irrigation design parameters.................................................................................. 23

3.5 Determination of Irrigation water requirement ................................................... 24

3.6 Crop selection criteria ............................................................................................. 24

3.7 Details of the layout................................................................................................ 24

3.8 Pipe materials/ characteristics ............................................................................... 25

3.9 Pipeline Hydraulic design........................................................................................ 26

CHAPTER FOUR: RESULTS AND DISCUSSION........................................28

4.1 Data processing and analysis................................................................................. 28

4.2 Collection of Climatic data ...................................................................................... 28

4.3 Site sampling of soil ................................................................................................ 28

4.3.1 Soil sampling......................................................................................................... 28

4.4 Reference evapotranspiration (ETO)..................................................................... 30

4.5 Crop Water Requirements Crop water requirement presentation..................... 31

4.6 Potential Crop evapotranspiration (ETc).....................................................32

4.7 Generation of contour map .................................................................................... 34

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4.8 General Design Considerations .................................................................35

4.8.1 Hydraulics Design Considerations ...................................................................... 36

4.8.2 General considerations’ for the design;............................................................. 37

4.8.3 Irrigation requirement. ........................................................................................ 37

4.8.4 Leaching Requirement......................................................................................... 38

4.8.5 Net depth of water application.......................................................................... 38

4.8.6 Net irrigation requirement per crop ................................................................... 38

4.8.7 Irrigation frequency or interval, IF..................................................................... 39

4.8.8 Number of emitters per plant ............................................................................. 39

4.8.9 Pipe size determination ....................................................................................... 40

4.8.10 Design of laterals ............................................................................................... 41

4.7.11 Sub main line to the laterals............................................................................. 41

4.7.12 Mainline from pump to the elevated tanks ..................................................... 42

CHAPTER FIVE: CONCLUSION AND RECOMMENDATIONS.....................43

5.1 Conclusion .............................................................................................43

5.2 Recommendations ................................................................................................... 43

REFERENCES ................................................................................................44

APPENDICES ................................................................................................45

APPENDIX I: Project lay out ......................................................................................... 45

Project pump house....................................................................................................... 46