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Performance assessment of water distribution in large scale irrigation

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Presentation on theme: "Performance assessment of water distribution in large scale irrigation"— Presentation transcript:

1 Performance assessment of water distribution in large scale irrigation
Case study of Chokwe Irrigation System in Mozambique by Claudio Julaia Prof. Bart Schultz PhD, MSc (UNESCO-IHE) Abraham Mehari Haile PhD, MSc (UNESCO-IHE)

2 Sequence of presentation
Introduction Study area description Problem statement and research questions Methodology Results and Discussion Conclusion and Recommendations

3 1. Introduction Agriculture continues to be a fundamental instrument for sustainable development and poverty reduction Irrigation is of great importance to minimize crop failure and improve crop yields Agriculture is by far the largest user of water Increasing the productivity of water in Agriculture results in easing competition for scarce resources, prevention of environmental degradation and provision of food security

4 2. Study area description
Located 230 km northwest of Maputo The main social and economic activity in the district agriculture and livestock Chokwe - priority region for Mozambique, important irrigation infrastructures, improve the food security and autonomy of the country Main crops grown: rice (wet season), maize and tomato (wet and dry season) Small farmers ( ha); Medium farmers ( ha); Big farmers (areas > 20 ha)

5 2. Study area description (Cont.)
Secondary drain Main drain Secondary canals Main canals Limpopo river

6 2. Study area description (Cont.)

7 3. Problem statement Limpopo river suffers from frequent droughts, which leads to regional crop production insecurity The short but intense rainy seasons are not enough to provide perennial water to the Limpopo River and tributaries Limpopo river shared by 4 countries Water scarcity problem in the Limpopo River Basin requires interventions at regional, national and local levels Producing more crop per less drop by improving the allocation and delivery of water in irrigation systems

8 3.1 Research questions What are the current operation rules of water distribution? What is the influence of different gate operation on the operational performance of the irrigation system? How can the performance indicators be adjusted to provide better results on the operational performance?

9 4. Methodology Selection of secondary canals: 15 secondary selected
Data collection: canal cross section, canal bed levels, daily water levels, discharge delivered, size of cultivated area, structures dimensions, interviews Required discharges computed through CROPWAT model Computation of performance indicators

10 4. Methodology Performance indicators: Adequacy Efficiency
Dependability Equity

11 4. Methodology (cont.) Water delivery schedules: fixed and flexible studied through CROPWAT model Flow simulations through DUFLOW model Scenarios for improvement of system operation performance: options for structure operations Location in the system Scenario 1 Scenario 2 Scenario 3 Intake 11 gates opened 0.4 m 8 gates opened m 8 gates opened m First regulator 8 gates opened 0.5 m 6 gates opened m 5 gates opened m

12 5. Results and discussion
Cropping pattern: wet season major crops are rice, maize and tomatoes; major crops dry season are maize, tomato and other vegetables; Performance indicators for wet and dry season (current situation): Irrigation season Performance indicators Adequacy Efficiency Dependability Equity Wet season 0.94 0.38 0.12 Dry season 1.00 0.14 0.0

13 5. Results and discussion (cont.)
Possible scenarios to improve water delivery performance: operational scenarios for water delivery

14 5. Results and discussion (cont.)
Scenarios Water saved (MCM) Additional area irrigated (ha) Wet season Dry season Scenario 1 15 10 1020 2680 Scenario 2 22 16 1520 4530 Scenario 3 28 1930 6150

15 5. Results and discussion (cont.)
Possible scenarios to improve water delivery performance: operational scenarios for water delivery

16 5. Results and discussion (cont.)
Comments on indicators proposed by Molden and Gates Yield reduction (%) for Maize Tomato Rice Fair adequacy (PA = 0.83/0.84) 1 Poor adequacy 1 (PA = 0.76) 4 Poor adequacy 2 (PA = 0.44) 9 13 15

17 5. Results and discussion (cont.)
Water delivery schedules

18 6. Conclusions Current operation rules results in over-supply
The operation of 8 gates opened 0.7 m at the intake and 5 gates opened 0.25 m at first regulator improved the efficiency from 0.38 to 0.55 The water saved under scenario 3 could be used to irrigate additional 1930 and 6150 ha in dry and wet season respectively. The efficiency indicator shows that the water is used more efficiently during the wet season than dry season The current thresholds of performance indicators proposed by Molden and Gates are not sufficiently informative

19 7. Recommendations The system should operate under lower water levels than actual (proposed in scenario 2 or 3) mostly during the late stages of the crops and during dry season The proposed irrigation schedule in each secondary canal should be followed The threshold for adequacy indicator, category “poor” and “fair” proposed by Molden and Gates should be revised and in correlation with the crop yield Capacity strengthens of farmers, irrigation specialists should be considered

20 Thank you for your attention

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