Amibara Irrigation Project II Completion Report Summary
Project: Amibara Irrigation Project II
Location: Middle Awash Valley, Ethiopia (~740m altitude)
Completion Date: February 1988
Client: Water Resources Development Authority (WRDA), Ethiopia
Consultant: Sir William Halcrow & Partners Ltd, UK
1. Project Overview
The Amibara Irrigation Project II involved:
- Development of 7,244 ha of Awash flood plain
- Conversion of 3,056 ha from pumped to gravity irrigation
- Construction of irrigation infrastructure including weir, canals, drains, and buildings
The project was funded by multiple agencies: World Bank (IDA), European Development Fund (EDF), and African Development Bank (ADB).
2. Key Components
2.1 Main Structures
- Melka Sadi Weir: Rockfill structure with headworks (Plate 5)
- Primary Canal: 13.4 m³/s capacity reducing to 2.8 m³/s downstream
- Drainage System: Primary and secondary drains with outfall to Awash River
- Buildings: Project control center, housing, and farm headquarters
2.2 Contract Structure
| Contract Series | Description | Example Contracts |
|---|---|---|
| Series 1 | Preliminary works | 1E (Buildings), 1K (External works) |
| Series 2 | Main civil works | 2A (Weir), 2B (Melka Sadi irrigation), 2C (Amibara irrigation) |
| Series 4 | Housing and buildings | 4A (Admin buildings), 4B (Housing), 4C (Farm HQs) |
3. Design Highlights
3.1 Irrigation System
- Peak field gate design: 0.85 l/s/ha (later increased to 1.00 l/s/ha)
- Field layouts modified from ridged basin to furrow irrigation
- Tertiary canals: 41km in Melka Sadi, 63km in Amibara
- Field canals: 184km in Melka Sadi, 346km in Amibara
3.2 Key Design Challenges
- Indigenous population issues (Afar livestock grazing)
- Housing and facilities shortages
- Groundwater and salinity concerns
- Canal siltation problems
4. Construction Aspects
4.1 Major Works
- Rockfill weir construction (Plates 5-8)
- Canal and drain networks
- 144 tertiary-canal checks and 346 offtakes
- Land leveling averaging 450 m³/ha
4.2 Challenges
- Material shortages (cement, steel, timber)
- Contractor organizational issues
- Accommodation and transport shortages
- Delays in working drawings
5. Operation and Maintenance Recommendations
- Measures to reduce siltation in irrigation system
- Debris removal at Melka Sadi headworks
- Improved water management practices
- Implementation of water charges
- Future sub-surface drainage requirements
6. Key Lessons
- Need for better housing and facilities planning
- Importance of adequate survey data before design
- Benefits of local contractor participation
- Need for ongoing monitoring of groundwater and salinity
- Importance of operation and maintenance planning