Amibara Irrigation Project Water Management Manual Summary
Project Overview
The Amibara Irrigation Project in Ethiopia's Awash Valley covers 10,300 hectares (4,600 ha in Melka Sadi and 5,700 ha in Amibara) with gravity irrigation serving state farms and settlement projects. The manual provides comprehensive guidance on water management for this semi-arid region (average rainfall 533mm/year).
Key Components
| Component | Description |
|---|---|
| Diversion Weir | 4m high rockfill structure designed for 700 m³/s flood capacity |
| Main Canal | 25.5 km long, designed for 13.3 m³/s discharge |
| Distributary Network | 30 km secondary canals and 93 km tertiary canals |
| Drainage System | Main drain (29 km), secondary (13.4 km) and tertiary drains (74 km) |
| Flood Protection | 4.3 km western dyke (3m high) and 34 km eastern dyke (1.5m high) |
Water Management Principles
- Soil Characteristics: Two main soil types - alluvial (sandy loams to silty loams) and vertisols (silty clay to clay)
- Crop Water Requirements: Detailed calculations for 7 major crops using Penman method
- Irrigation Scheduling: Based on soil moisture balance, effective rainfall, and crop growth stages
- Furrow Irrigation: Primary method for row crops with specific guidelines on spacing, slopes, and flow rates
Key Calculations
| Crop | Water Requirement (mm/season) | Growing Period (days) |
|---|---|---|
| Bananas | 2,483 | 365 |
| Cotton (May planting) | 892 | 145 |
| Peppers | 813 | 160 |
| Maize | 624-685 | 140 |
| Onions | 571 | 120 |
Monitoring & Evaluation
The manual includes detailed procedures for:
- Soil moisture measurement (tensiometers, gypsum blocks, neutron probe)
- Infiltration rate determination
- Furrow irrigation evaluation
- Rain gauge network establishment (1 station per 600 ha)
Salinity Management
Leaching requirements calculated to maintain soil salinity below crop tolerance levels (e.g., ECe 7.7 mmhos/cm for cotton, 1.0 for bananas). Drainage system designed for 63mm/24hr rainfall (10-year return period).