1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Book project: SLM in Practice - Guidelines and Best Practices for Sub-Saharan Africa (SLM in Practice)

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

Book project: Water Harvesting – Guidelines to Good Practice (Water Harvesting)

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

UNESCO - IHE (UNESCO - IHE) - Netherlands

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Ja

2.1 Short description of the Technology

Definition of the Technology:

Spate irrigation is a traditional water diversion and spreading technology.

2.2 Detailed description of the Technology

Description:

Spate irrigation has a long history in Eritrea and still forms the livelihood base for rural communities in arid lowlands of the country.

Purpose of the Technology: It is a traditional water diversion and spreading technique under which seasonal floods of short duration – springing from the rainfall-rich highlands – are diverted from ephemeral rivers (wadis) to irrigate cascades of leveled and bunded fields in the coastal plains.

Establishment / maintenance activities and inputs: The diversion structures include the following elements: (1) the ‘agim’, a temporary 3-4 m high river diversion structure on the low-flow side of the wadi, made from brushwood, tree trunks, earth, stones and/or boulders, erected to divert a large part of the flow during a spate flow to adjacent agricultural fields; (2) a primary, and several secondary, distribution canals; unlined, bordered by earthen embankments; convey and spread the floodwater to the irrigable fields; (3) the fields, rectangular shaped, of about 1–2 ha, separated by earthen bunds. Floodwater is distributed from field to field: when a field is completely flooded (to a depth of about 0.5 m), water is conveyed to the immediate downstream field by breaching one of the bunds. This process continues until all the water is used up. Arable fields need to be flooded several times. The water soaks deep into the soil profile (up to 2.4 m) and provides moisture sufficient for two or even three harvests: crop growth is entirely dependent on the residual soil moisture. The main crop grown is sorghum; maize is the next most important. Sedimentation is as important as water management: With each flood, soil is built up by depositing rich sediment on the fields. Due to the force of the floods, the diversion structures are frequently damaged and/or washed away. Reconstruction and maintenance are labour-intensive and require collective community action.

Natural / human environment: Elaborate local regulations, organization and cooperation at the community level are prerequisites for successful management of spate irrigation systems.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

2.6 Date of implementation

If precise year is not known, indicate approximate date:

• more than 50 years ago (traditional)

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• as part of a traditional system (> 50 years)

Comments (type of project, etc.):

Spate irrigation is an indigenous technology, originally introduced from Yemen

3.1 Main purpose(s) of the Technology

• improve production
• reduce, prevent, restore land degradation

3.2 Current land use type(s) where the Technology is applied

Comments:

Livestock is grazing on crop residues

3.3 Further information about land use

Comments:

Water supply: post-flooding

3.4 SLM group to which the Technology belongs

• irrigation management (incl. water supply, drainage)
• surface water management (spring, river, lakes, sea)

3.5 Spread of the Technology

Comments:

Total area covered by the SLM Technology is 160 m2.

Current spate irrigation area in Eritrea is 16’000 hectares. Potential area is estimated at 60’000–90’000 hectares.

3.6 SLM measures comprising the Technology

Comments:

Main measures: structural measures

4.1 Technical drawing of the Technology

4.2 Technical specifications/ explanations of technical drawing

Cross section of an agim (top left); Components of a traditional spate irrigation system: (1) agim; (2) main distribution canal; (3) irrigated fields; (4) earthen embankments. Arrows indicate the water flow

Technical knowledge required for field staff / advisors: high

Technical knowledge required for land users: high

Main technical functions: control of concentrated runoff: drain / divert, increase of infiltration, water harvesting / increase water supply, water spreading

Diversion ditch/ drainage
Depth of ditches/pits/dams (m): 4.00

Construction material (earth): earth

Construction material (stone): stones

Construction material (wood): brushwood, tree trunks

4.4 Establishment activities

	Activity	Type of measure	Timing
1.	Construction of diversion structure (agim)	Structural	before rainy season
2.	Construction of main distribution canal	Structural	before rainy season
3.	Construction of secondary distribution canals	Structural	before rainy season
4.	Leveling of fields	Structural	before rainy season
5.	Establish embankments around fields and within fields	Structural	before rainy season

4.5 Costs and inputs needed for establishment

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Labour	ha	1.0	24.0	24.0
Equipment	Animal traction	ha	1.0	36.0	36.0
Total costs for establishment of the Technology					60.0

4.6 Maintenance/ recurrent activities

	Activity	Type of measure	Timing/ frequency
1.	Reconstruction / repair of diversion structures (2-4 times / year; collective community action)	Structural	2-4 times / year
2.	Desilting / repair of distribution canals	Structural	annual
3.	Raising of bund heights due to silting up of fields	Structural	annual
4.	Flood fields (community action, during highland rainy season: July-September). Most likely a field receives 3 irrigation turns, on a bi-weekly interval between any 2 turns	Structural	rainy season (july-september)
5.	Soil tillage (15 cm deep; using oxen-drawn plough) to break capillary uplift of soil water and to create evaporation barrier	Structural	end of flooding season

4.7 Costs and inputs needed for maintenance/ recurrent activities (per year)

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Labour	ha	1.0	24.0	24.0
Equipment	Animal traction	ha	1.0	36.0	36.0
Total costs for maintenance of the Technology					60.0

Comments:

Machinery/ tools: scouring and tillage implements, shovels

The costs were calculated per unit = 10 m long agim (1 m high, 3 m wide), constructed with mixed material (stones, earth, brushwood)

4.8 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Data on labour inputs for construction/maintenance of canals and field bunds are not included, therefore not included in the tables above. Costs for agim reconstruction are 40% of establishment. Total maintenance costs depend on the number of reconstructions during normal spate season (2-4 times). The yearly cost (establishment and maintenance) reaches US$ 60-156.

5.1 Climate

5.2 Topography

Comments and further specifications on topography:

Altitudinal zone: 101-500 m a.s.l. (200 m.a.s.l.)

5.3 Soils

If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

Soil texture is medium (loam to silt loams)
Soil fertility is very high (alluvial silts formed by annual sedimentation)
Soil drainage/infiltration is good

5.4 Water availability and quality

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly disadvantaged land users

Difference in the involvement of women and men: water management carried out communally, crop management individually

5.7 Average area of land owned or leased by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• state

Land use rights:

• individual

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Income and costs

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

	Season	Type of climatic change/ extreme	How does the Technology cope with it?
annual temperature		increase	well

Climate-related extremes (disasters)

Meteorological disasters

	How does the Technology cope with it?
local rainstorm	well
local windstorm	well

Climatological disasters

	How does the Technology cope with it?
drought	well

Hydrological disasters

	How does the Technology cope with it?
general (river) flood	well

Comments:

The technology is tolerant to climatic extremes (adapted to unpredictable heavy floods)

6.4 Cost-benefit analysis

Comments:

no data

6.5 Adoption of the Technology

Comments:

There is a strong trend towards spontaneous adoption of the Technology

Comments on adoption trend: Spontaneous spread takes place throughout the lowlands. Current spate irrigation area in Eritrea is 16’000 hectares. Potential area is estimated at 60’000–90’000 hectares.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Spate irrigation forms the livelihood base for rural communities in arid lowlands of the country

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view	How can they be overcome?
Highly labour-intensive and time consuming maintenance; water diversion structures are frequently breached / washed away by heavy floods; canals are obstructed through deposition of boulders, gravel and coarse sediments.	To overcome all 3 problems, recommendations focus on building permanent flood diversion and distribution structures which:
Great demand for wood: huge numbers of trees are annually needed for (re-)constructing diversion structures	(1) withstand the force of heavy floods and divert the water effectively;
Irrigation efficiency is only about 20% because of the difficulty of controlling large amounts of water in a short period of time (and often at night) and because water is lost by percolation, seepage and evaporation	(2) eliminate the need to cut trees
	(3) reduce human and animal labour inputs
	(4) increase productivity; Lining the main canals with cements would reduce water loss by percolation and seepage. Proper leveling of basin fields helps to distribute the floodwater uniformly

7.2 References to available publications

Title, author, year, ISBN:

Abraham Mehari H, Van Steenbergen F, Verheijen O, Van Aarst S:Spate Irrigation, Livelihood Improvement and Adaptation to Climate Variability and Change

Title, author, year, ISBN:

Mehretab Tesfai Stroosnijder L:The Eritrean spate irrigation system

Title, author, year, ISBN:

Berhane Haile G, Van Steenbergen F: Agricultural Water Management in Ephemeral Rivers: Community Management in Spate Irrigation in Eritrea; in African Water Journal

7.3 Links to relevant information which is available online

Title/ description:

Abraham Mehari, Depeweg, H, Schultz B (2005): Hydraulic Performance Evaluation of The Wadi Laba Spate Irrigation Systemin Eritrea, in Irrigation and Drainage. 54: 389–406

URL:

www.interscience.wiley.com

Title/ description:

Berhane Haile G: Community Spate Irrigation in Bada, Eritrea n Mehretab Tesfai, Stroosnijder L (2000): The Eritrean spate irrigation system

URL:

linkinghub.elsevier.com/retrieve/pii/S0378377400001153