Evaluation of Water Use at Sagana Irrigation Scheme in Nyeri District (
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I' EVALUATION OF WATER USE AT SAGANA IRRIGATION SCHEME IN NYERI DISTRICT (. ais tbesis AccErs XIIV" DEGUT V b al ed \SU A c<,r ' ONlVKftSlTV By Sifuma John B.sc Agricultural Engineering University of Nairobi — 9 O. 30197 A thesis submitted to the University of Nairobi in partial fulfilment of the requirement for the degree of Master of science in Soil and Water Engineering. August 1997 DECLARATION I, hereby, declare that this thesis is my original work and has not been presented for a degree in any other university. Sifuma John Date This thesis has been submitted for examination with my approval as the university supervisor. Date 1 DEDICATION Dedicated to my late father, Jasper. I . Sifuma. 11 APPRECIATION I would like to extend my appreciation to the following people; Mr Macharia Githumbi and other farmers in Sagana Irrigation Scheme for their cooperation and support during my data collection; the coordinator SIDP, Dr.Scheltema for availing the scholarship; the Ministry of Agriculture for granting me study leave; my university supervisor Dr.F.N Gichuki for his support, guidance, and encouragement during the entire course and research work; my colleagues in the Ministry of Agriculture for their support during my field work and report preparation. Finally, I would like to thank my wife Leah and my son Jeff for their support and patience during my absence. To all mentioned above, God bless you. i n Table of Contents DECLARATION ...................................... i DEDICATION........................................ ii APPRECIATION ...................................... iii LIST OF FIGURES AND T A B L E S ..........................viii LIST OF A N N E X E S .................................. ix LIST OF A B B R E V I A T I O N S ............................ X ABSTRACT .......................................... xi 1. INTRODUCTION ...................................... 1 1.1 IRRIGATION DEVELOPMENT IN KENYA .............. 1 1.2 JUSTIFICATION AND OBJECTIVES ............... 3 1.2.1 Justification ..................... 3 1.2.2 O b j e c t i v e s ................... 4 2. LITERATURE REVIEW ................................ 5 2.1 EVALUATION OF IRRIGATION SCHEMES .......... 5 2.1.1 Causes of poor performance .... 5 2.1.2 Evaluation methodology ....... 6 2.1.3 Evaluation criteria ............... 8 2.1.4 Performance improvement ....... 10 2.2 WATER U S E .................................... 11 2.2.1 Cropping patterns and crop water requirement........................ 11 2.2.2 Yield response to water and f e r t i l i z e r ....................... 16 2.3 IRRIGATION EFFICIENCY ....................... 19 2.4 SCHEME WATER REQUIREMENTS ................. 22 IV 2.4.1 Irrigation requirements ........... 22 2.4.2 Effective rainfall ............... 23 2.4.2 Field irrigation scheduling.... 23 2.4.3 Available river f l o w ....... 24 3. METHODOLOGY ...................................... 2 6 3.1 SITE D E S C R I P T I O N ............................ 26 3.1.1 l o c a t i o n .................... 26 3.1.2 Topography and s o i l s ....... 26 3.1.3 Cl im a t e ...................... 28 3.1.4 Background information ........... 28 3.1.5 Farming s y s t e m .............. 29 3.1.6 Irrigation system ................. 30 3.2 OPTIMAL CROPPING SYSTEM FOR SAGANA IRRIGATION SCHEME ...................................... 33 3.2.1 Determining the optimal cropping p a t t e r n ...................... 33 3.2.1.1 Climatic data analysis .... 33 3.2.1.2 Selection of suitable crops . 33 3.2.1.4 Market p r i c e s ............ 35 3.3 RESPONSE OF FRENCH BEANS TO DIFFERENT WATER APPLICATION DEPTHS AND FERTILIZERS RATES . 37 3.3.1 Experimental site description ... 37 3.3.1.1 Location................... 37 3.3.1.2 Soil t e x t u r e .............. 37 3.3.1.3 Soil water retention ........ 40 3.3.1.4 Topography................. 41 3.3.1.5 Experimental layout ........ 43 v 3.3.1.6 Land preparation ............. 43 3.3.1.7 Planting and pre-irrigation . 43 3.3.1.8 Plant protection ............. 44 3.3.1.9 Irrigation water application and irrigation scheduling .... 45 3.3.2 Data collection............. 47 3.3.2.1 Soil moisture determination . 47 3.3.2.2 Crop h e i g h t ............ 47 3. 3.2.3 Crop c o v e r .............. 4 8 3.3.2.4 Irrigation depth measurement . 48 3.3.2.5 Crop y i e l d .............. 49 4. RESULTS AND DISCUSSION............................ 50 4.1 DEVELOPMENT OF OPTIMAL CROPPING SYSTEM FOR SAGANA IRRIGATION SCHEME ................... 50 4.1.1 Climatic d a t a ............... 50 4.1.2 Soil d a t a ................... 51 4.1.3 Crop selection ............ 51 4.1.4 Farmers preferences and responses based on questionnaire .... 53 4.1.5 Tentative Cropping Calendar .... 54 4.1.6 Market p r i c e s ............... 55 4.1.6 Optimal cropping pattern ........ 55 4.2 RESPONSE OF FRENCH BEANS TO DIFFERENT WATER APPLICATION DEPTHS AND FERTILIZERS RATES . 61 4.2.1 Rainfall and irrigation.... 61 4.2.2 Crop height and crop cover .... 62 4.2.3 Crop y i e l d ................. 64 vi 4.2.4 Soil moisture content ............. 67 4.2.5 Yield response to water and f e r t i l i z e r ....................... 68 5. CONCLUSIONS AMD RECOMMENDATIONS ................. 70 5.1 CONCLUSIONS.................................. 7 0 5.2 RECOMMENDATIONS.............................. 71 6. REFERENCES........................................ 72 vii LIST OF FIGURES AND TABLES Figure Page 3.1 Location of Sagana Irrigation Scheme ............... 27 3.2 Distributary system for Sagana Irrigation Scheme . 32 3.3 Determination of optimal cropping system and crop water requirements....................... 34 3.4 Location of experimental plots ..................... 38 3.5 Experimental layout ................................ 42 3.6 Experimental plot with operating sprinklers .... 45 4.1 Averaged climatic data for Sagana State lodge Meteorological station................................. 50 4.2 Average market prices for horticultural crops . 56 4.3 Optimal cropping pattern ........................... 57 4 .4 Crop height ...................................... 62 4.5 Crop cover ........................................ 63 4.6 Crop yield at different water levels and fertilizer rates .................................... 65 A. 7 Crop coefficients (Kc ) for French b e a n s .........96 Table 1.1 Irrigated crop hectarage in Kenya in 1990 ......... 2 4.1 Temperature requirements for selected crops .... 52 4.2 Growing seasons for selected crops ................. 52 4.3 Farmers preferences ............................... 53 4 . 4 Months with peak produce p r i c e s ................. 55 4.5 Distribution of crops in optimal cropping pattern . 56 4.6 Averaged reference crop evapotranspiration (ET0) and effective rainfall ......................... 58 4.7 Cropwater requirements, effective rainfall and irrigation requirements ....................... 59 4.8 Monthly irrigation requirements and permitted abstraction for Sagana irrigation scheme .... 60 4.9 Amount of water applied .......................... 61 4.10 Yield of French beans (Kg/ha) ........................64 4.11 Analysis of variance for crop yields ............. 66 4 . 12 Farmers y i e l d s .................................... 66 4.13 Change in soil moisture s t o r a g e ..................67 4.14 Crop evapotranspirat i o n .......................... 68 4.15 Computed yield response factors (Ky ) 69 LIST OF ANNEXES Annex 1: Soil d a t a .................................... 77 A.1.1 Soil test report for Sagana Irrigation S c h e m e .......................................77 A.1.2 Field capacity, permanent wilting point and bulk d e n s i t y ............................ 78 A.1.3 Total available soil w a t e r ..................78 A.1.4 Texture analysis ............................ 79 Annex 2: Questionnaire and list of farmers ............ 80 A.2.1 List of f a r m e r s ............................ 82 vi ii A. 2.2 Crops grown by f a r m e r s ..................... 83 Annex 3: River flow d a t a ........................ 84 A.3.1 Analysis of low flows for River Sagana (RGS-4AA01) 84 A . 3.2 Monthly low flows for River Sagana .... 85 Annex 4: Crop market prices (for horticultural produce, Karatina Market) ............................ 86 A.4.1 Average monthly prices for Onion ........ 86 A.4.2 Average monthly prices for Capsicum ... 86 A.4.3 Average monthly prices for Cabbage .... 86 A.4.4 Average monthly prices for Carrot .... 86 Annex 5: Climatic Data for Sagana Meteorological S t a t i o n ............................... 87 A.5.1 Temperature, Humidity, Sunshine hours, and Windrun data(1971 - 1986) ............ 87 A.5.2 Rainfall and Pan evaporation data (1971 — 1986) 88 A . 5.3 Average monthly effective rainfall as related to average monthly rainfall . 88 Annex 6: Cropwater requirements computed using CROPWAT 89 A.6.1 Cropwater requirements and effective r a i n f a l l .................................... 89 A.6.2 Cropwater requirements for French beans 89 A.6.3 Cropwater requirements for French beans . 90 A.6.4 Cropwater requirements for Capsicum ... 90 A.6.5 Cropwater requirements for Carrot .... 91 A.6.6 Cropwater requirements for Cabbage .... 91 A.6.7 Cropwater requirements for Onion ......... 92 A.6.8 Cropwater requirements for Maize ......... 92 A.6.9 Cropwater requirements for Potato .... 93 Annex 7: Soil Water Balance Sheet (Plot E21 at Water level 1) and crop coefficient........ 94 A.7 Soil water balance for plot E 2 1 ........... 94 Annex 8: Crop evapotranspiration and Y i e l d s ........ 97 A.8.1 Depth of irrigation in individual subplots 97 A. 8.2 Crop yield and evapot ranspiration at each p l o t .........................................98 Annex 9: Crop Height .................................. 99 A. 9 Crop height at each p l o t ................... 99 Annex 10: Crop c o v e r .................................. 100 A.10 Percentage crop ground cover at each plot 100 Annex 11 Irrigation schedule for the optimal cropping s y s t e m ............................... 101 A.11.1 Irrigation schedule details for French beans ............................ 102 A.11.2 Irrigation schedule details for French beans ...........................