Amibara Project Design Report Summary

1. Project Overview

The Amibara Irrigation Project is a major development in Ethiopia's Awash Valley, designed to irrigate approximately 10,000 hectares of land for cotton cultivation and other crops. The project represents a central component of the broader Awash Valley development scheme.

Key Components:

• River diversion structure at Melka Sadi
• Main and primary supply canals
• Primary and secondary drainage systems
• Flood protection dykes (western and eastern)
• Road network and bridges
• Settlement villages and housing
• Administrative centers

2. Key Design Decisions

2.1 Single Diversion Structure

The report recommends using a single barrage at Melka Sadi rather than two structures (as previously proposed by Italconsult), citing:

• Estimated cost savings of Eth$2 million
• Alleviation of potential drainage problems in Melka Sadi area
• Simplified water control operations
• Unfavorable foundation conditions at the alternative Melka Marer site

2.2 Irrigation System Design

The irrigation layout utilizes:

• A central ridge for the primary supply canal
• Primary drains along eastern and western boundaries
• Secondary canals following contours
• Design duty of 1.68 l/sec/ha (overall irrigation efficiency of 69%)

2.3 Flood Protection

The western dyke is designed to protect against Awash River floods up to 2000 m³/sec:

• Economic analysis suggests optimal dyke height of 3-4 meters
• Clearance of riverside trees could reduce required height by 0.5-1m
• Eastern dyke protects against floods from Alledeghi plain

3. Implementation Strategy

3.1 Contract Structure

Contract Type	Description
Preliminary Works	Bush clearing, site investigations, link road construction
Buildings and Services	Settlers housing, AVA housing, administration buildings
Main Works	Barrage construction, canal works, flood protection, etc.

3.2 Labor Strategy

The report recommends labor-intensive methods where economically competitive:

• Excavation of secondary/tertiary canals by hand
• Construction of minor structures in masonry
• 90% reimbursement of increased labor costs to contractors

3.3 Phased Implementation

The project will be completed in three phases:

1. Phase I (by June 1976): 4,200 ha including AVA settlement farm
2. Phase II: Adjacent 4,400 ha including existing concessions
3. Phase III: Remaining 1,500 ha

4. Key Technical Data

4.1 Water Requirements

Project Area	Gross Area (ha)	Design Flow (cumecs)
Melka Sadi	5,100	5.5
Amibara	10,100	12.2
Bolhamo (potential)	8,900	10.8
Angelele (potential)	4,750	5.8

4.2 Flood Data

Design floods at Melka Sadi barrage site:

• 1000 cumecs: ~10,000 year return period
• 2000 cumecs: ~50 year return period

5. Appendices Summary

Appendix A: Existing Developments

Describes five existing developments in the project area including the Melka Marer Research Station, AVA settlement farms, and three large concessions.

Appendix B: Single vs. Two Diversion Structures

Detailed cost-benefit analysis favoring a single barrage at Melka Sadi with estimated Eth$2 million savings.

Appendix C: Effects of Angelele/Bolhamo Development

Potential modifications needed if these adjacent areas are developed, including increased canal capacities.

Appendix D: Western Dyke Design

Technical considerations for flood protection dyke alignment and height.

Appendix E: Groundwater Interpretation

Analysis suggesting silty loam subsoil may behave like clay, affecting drainage assumptions.

Appendix F: Contract Types

Detailed specifications for different contract packages including site investigations, link road, bush clearing, etc.

6. Decisions Required from AVA

1. Approval of proposed layout with single diversion structure
2. Approval of design criteria for irrigation, flood protection, etc.
3. Approval of implementation methods and program
4. Approval for Eth$20,000 force account expenditure for site access
5. Agreement on liaison procedures between AVA and Halcrows