assessing irrigation conveyance losses: case studies of ahero & bura irrigation schemes

ASSESSING IRRIGATION CONVEYANCE LOSSES:

CASE STUDIES OF AHERO & BURA IRRIGATION SCHEMES

A COLLABORATIVE RESEARCH PROJECT BETWEEN NIB AND UON

ByGichuki F., Maina D., S. M. Muturi and Wanjogu R. K.

Date: 13th JUNE 2013

Ahero, Bura and Mwea Irrigation Schemes case studies

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PRESENTATION OUTLINE Introduction Objectives Methodology Research results Acknowledgements

AIS & BIS water loss study-NIB & UON

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INTRODUCTION Irrigation in Kenya faces serious challenges which

have negatively affected the productivity, profitability and sustainability of most irrigation schemes. The following is a partial listing of the main challenges High pumping costs; High levels of siltation; unpredictable flooding & drought High conveyance and application losses; High mismatch between water demand and supply; Inadequate drainage of excess water and removal of excess

salts; and Inequity in water delivery in different irrigation blocks and

irrigated fields. Inadequate irrigation skills among farmers and other

stakeholdersSource: NIB Strategic Plan 2008-2012


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NIBS STRATEGIC DECISIONS NIB has prioritized research on irrigation water

loss and has consequently included it as a global PC target FY 2012/13. This is a logical step in any water management improvement initiative

Cognizant of these challenges, NIB + UON – College of Architecture and Engineering have developed a comprehensive research program to improve performance of irrigated agriculture through better irrigation water management.

Phase I of the research will focus on water conveyance losses


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AIS & BIS water loss study-NIB & UONGOALS OF NIB-UON RESEARCH COLLABORATION

Specific goal RationaleReduced water loss

Reducing water loss will secure water for expansion of irrigated area, enhancing equitable distribution, reduce operation and maintenance costs and avail water for downstream users

Enhance equitable water distribution

Enhancing equitable water distribution will reduce water use conflicts and enhance payment of operation and maintenance fees

Reduce operation and maintenance costs

Reducing costs will enhance recovery of operation and maintenance fees

Enhance production and profitability

Enhanced production and profitability will enhance poverty reduction outcomes of irrigated agriculture

Reduce environmental degradation

Enhance sustainability through reduced in-scheme land and water degradation and by securing water for downstream ecosystems.

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AIS & BIS water loss study-NIB & UONRATIONALE FOR CONVEYANCE SYSTEM RESEARCH:

Low efficiency (30-70%) of conveyance and distribution system with major implications on:Scheme water intake sub-systemOperation and maintenance of

conveyance sub-systemOn-farm sub-system

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OBJECTIVESOverall goal: To generate and enhance utilization of data,

information and knowledge on irrigation water management in ways that promote innovation and effective and efficient utilization of the resources.

Specific objectives To quantify conveyance and distribution water

losses in Ahero, Bura and Mwea Irrigation Schemes

Formulate strategies and plans for performance improvements


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AIS & BIS water loss study-NIB & UONKEY ISSUES THAT WILL ADDRESSED

1. Assess performance and opportunities and constraints for improving performance;

2. Identify innovative solutions that will enhance the performance of the water delivery and water application sub-systems;

3. Evaluate technical performance of the innovative solutions;

4. Evaluate costs and benefits of performance improvements;

5. Formulate strategies and plans for performance improvements;

6. Identify investment priorities; and 7. Propose financing/ options.

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METHODOLOGY: SYSTEM CHARACTERIZATION Task 1: Digitizing the network


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KEY OUTPUTS: SYSTEM CHARACTERIZATION


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UCA Length(km) Area(ha) Canal density m/ha

U1 6.76 136.48 49.56U2 5.25 110.18 47.64U3 6.73 134.16 50.16U4 4.63 105.07 44.10U5 5.14 126.65 40.58U6 3.30 59.94 55.01U7 5.69 107.73 52.80U8 5.23 120.94 43.24U9 3.65 70.10 52.04U10 3.16 61.18 51.60U11 2.49 44.41 56.03GrandTotal 64.48 1,076.85 59.88

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UCA Length (km)

Area (ha) Canal densitym/ha

MainCanal 69.01 2,641.55 26.12U1 27.54 196.32 140.27U2 29.04 550.74 52.72U3 33.19 433.09 76.63U4 53.80 1,044.01 51.53U5 16.74 361.64 46.29U6 6.40 55.73 114.83Total 166.71 2,641.55 63.11

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UCA Length(km) Area(ha) Canallengthm/haMIAD 7.77 90.00 86.34M10 3.51 33.00 106.27M9 5.92 51.00 116.04M11 2.98 48.00 61.99M17 8.92 139.00 64.14M12 5.06 77.00 65.66M13 4.19 68.00 61.58M14 8.11 106.00 76.48M15 4.84 47.00 103.03M16 10.88 132.00 82.43H18 8.99 115.00 78.19H20 6.96 115.00 60.49H19 8.17 111.00 73.65M5 6.64 75.00 88.57M6 7.16 64.00 111.88M7 3.29 49.00 67.24M8 2.20 25.00 87.98M1 9.05 80.00 113.16M2 3.24 41.00 79.01M3 4.67 53.00 88.17M4 10.47 132.00 79.28H1 4.44 73.00 60.77H6 13.13 111.00 118.28H7 7.79 83.00 93.86H8 7.97 96.00 83.06H2 7.30 92.00 79.32H3 8.20 108.00 75.96H4 6.02 90.00 66.92H5 17.23 156.00 110.47W7 6.64 60.00 110.69W1 12.40 130.00 95.39W2 14.44 195.00 74.05W3 11.37 173.00 65.71W7 6.52 61.00 106.94W4 14.40 132.00 109.06W5 10.94 163.00 67.09W6 22.04 206.00 106.97K1 21.24 208.00 102.10K2 13.86 165.00 84.01K3 15.70 132.00 118.96K4 12.63 145.00 87.08K5 16.54 148.00 111.73K6 10.97 111.00 98.87K7 9.05 131.00 69.08K8 3.32 30.00 110.70

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METHODOLOGY: LOSS ASSESSMENT


Canal loss mainly comprise of seepage, evapotranspiration (EVT) & leakages

The water balance (inflow/outflow) method will be used for quantifying canal loss-this will not interrupt irrigation program

Seepage rates will be measured using inflow/outflow, ponding and seepage meter methods

Calibration and possibly repair of all measuring/regulating canal structures will be necessary to facilitate flow measurements-critical in this study

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Ponding methodTo eliminate the effect of wind, the rate of drop should be measured at each end of the pool and averaged. Staff or hook gauges attached to existing structures or stakes driven into the canal bed should be used as shown in the figure below.

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PRELIMINARY RESULTS: LOSS ASSESSMENT


Distance from point [m]

Depth [m]

Width [m]

Area [m^2]

Velocity 1 [cm/s]

Velocity 2

[cm/s]

Velocity 3

[cm/s]

Average

Velocity at Point [cm/s

]Discharge [m^3/s]

2.3 0 0 0 0 0 0.00 0.0002.1 0.25 0.2 0.05 23.5 24.1 20.2 22.60 0.0111.8 0.42 0.3 0.126 51.9 50.4 49.5 50.60 0.0641.5 0.47 0.3 0.141 44.2 40.3 39.5 41.33 0.0581.2 0.43 0.3 0.129 27.7 28 28.5 28.07 0.0360.9 0.35 0.3 0.105 22.1 22.1 21.6 21.93 0.0230.6 0.2 0.3 0.06 4.1 3.9 2 3.33 0.0020.4 0 0.2 0 0 0 0 0.00 0.000

Total Discharge [m^3/s] 0.195

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PRELIMINARY RESULTS: LOSS ASSESSMENT


Site Offtake

Gross loss m/day

Efficiency

% loss to closed offtakes

Gross loss due to

INFILTRATION and EVAPO.

mm/day % %

Site 1 Site 2 0.094 0.98 0.70 28.05Site 3 0.358 0.89 0.80 71.53 Site 4 Site 5 0.470 0.88 0.85 70.48 Site 6

Site 7 0.707 0.51 0.90 70.73Site 8 Site 9 0.177 0.85 0.50 88.33

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METHODOLOGY: WATER BALANCE MODELING Thiba system linkages


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METHODOLOGY: WATER BALANCE MODELING Elements of the water balance model


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PRELIMINARY RESULTS: WATER BALANCE MODEL


Unit IWR m3/day SL m3/day EL m3/day

Main Canals - 179.56 359.11

U1 11,792.28 32.47 64.94 U2 9,519.29 24.94 49.89 U3 11,591.65 33.99 67.99 U4 9,078.19 22.41 44.82 U5 10,942.63 25.11 50.23 U6 5,178.76 18.20 36.39 U7 9,308.14 27.12 54.24 U8 10,449.02 24.95 49.89 U9 6,056.82 16.48 32.97 U10 5,285.65 14.72 29.44 U11 3,837.36 12.04 24.08

Grand Total 93,040 432

864

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ON-GOING SIMULATION STUDIES Design, operation and maintenance issues for example what

is the effect of changes on cropping calendar and system layout


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ACKNOWLEDGEMENT The implementing team comprising of Dr. F.

Gichuki, R. Wanjogu, A. Owilla, D. Maina and S. Muturi wish to thank the General Manager, NIB for funding this project

Thank you
