Technologies

Soil faced deep trench bunds [Ethiopia]

Nay Hamed Amik Metrebwi Zala

technologies_1197 - Ethiopia

Completeness: 78%

1. معلومات عامة

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

Key resource person(s)

SLM specialist:
SLM specialist:

Sibhatleab Mulugeta

Mekelle University

Ethiopia

SLM specialist:

Weldearegay Kifle

Mekelle University

Ethiopia

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Mekelle University (Mekelle University) - Ethiopia

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:

نعم

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Compacted soil bund constructed following a contour using a soil excavated from deep trenches on the up-slope side.

2.2 Detailed description of the Technology

Description:

Soil faced deep trench bund is constructed by excavating trenches of 1 m deep, 0.5 - 1 m wide and 2 - 3.5 m long with spacing between trenches of 0.3 - 0.5 m along the contour and using the excavated soil to construct a compacted bund downslope. The smaller dimensions are usually used in cultivated lands while the larger are implemented in grazing lands.

Purpose of the Technology: Soil faced deep trench bund decreases slope length, runoff velocity and soil loss; and increases runoff harvesting, soil moisture and groundwater recharge.

Establishment / maintenance activities and inputs: Construction of soil faced deep trench bund involves alignment of a contour, excavation of trenches, construction and compaction of bund and planting grass, while the maintenance involves dredging of sediment from the trenches and use it for reinforcing the embankment.

Line level, tape meter, digging hoe, shovel and grass are needed for the establishment and maintenance.

Natural / human environment: The technology is implemented in moderate (5 - 8%) and hill (8 - 16%) slopes and in medium and heavy soil types of at least 1 m depth. It reduces runoff amount and velocity thereby decreasing soil loss and desertification/land degradation. It also improves soil moisture availability and groundwater recharge by encouraging lateral and vertical movement of water respectively.

It is mostly constructed using communal labour and there is an encouraging trend of spontaneous adoption. The technology is witnessed to be increasing crop and fodder production thereby improving the livelihood of the land users. It, however, is labour intensive and slightly reduces farm size.

2.3 Photos of the Technology

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

بلد:

Ethiopia

Region/ State/ Province:

Tigray

Further specification of location:

Kilte Awlaelo

Specify the spread of the Technology:
  • evenly spread over an area
If precise area is not known, indicate approximate area covered:
  • 10-100 km2

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • through projects/ external interventions

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

  • reduce, prevent, restore land degradation

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

Cropland

Cropland

  • Annual cropping
  • Perennial (non-woody) cropping
Annual cropping - Specify crops:
  • cereals - barley
  • cereals - maize
  • cereals - sorghum
  • oilseed crops - sunflower, rapeseed, other
  • wheat, teff
  • elephant grass
Number of growing seasons per year:
  • 1
Specify:

Longest growing period in days: 150 Longest growing period from month to month: June - November

Grazing land

Grazing land

Intensive grazing/ fodder production:
  • Cut-and-carry/ zero grazing
  • Improved pastures
Comments:

Major land use problems (compiler’s opinion): Soil erosion, overgrazing, decline of soil fertility and productivity.

Major land use problems (land users’ perception): Soil erosion, reduced soil depth, fertility and productivity.

3.4 Water supply

Water supply for the land on which the Technology is applied:
  • rainfed

3.5 SLM group to which the Technology belongs

  • cross-slope measure
  • ground water management

3.6 SLM measures comprising the Technology

vegetative measures

vegetative measures

  • V2: Grasses and perennial herbaceous plants
structural measures

structural measures

  • S2: Bunds, banks
Comments:

Main measures: structural measures

Secondary measures: vegetative measures

Type of vegetative measures: aligned: -contour

3.7 Main types of land degradation addressed by the Technology

soil erosion by water

soil erosion by water

  • Wt: loss of topsoil/ surface erosion
  • Wg: gully erosion/ gullying
biological degradation

biological degradation

  • Bc: reduction of vegetation cover
Comments:

Main type of degradation addressed: Wt: loss of topsoil / surface erosion

Secondary types of degradation addressed: Wg: gully erosion / gullying, Bc: reduction of vegetation cover

Main causes of degradation: soil management, overgrazing, Heavy / extreme rainfall (intensity/amounts), population pressure

Secondary causes of degradation: crop management (annual, perennial, tree/shrub) (Crop residues are removed during harvesting), over-exploitation of vegetation for domestic use, change of seasonal rainfall, droughts, land tenure, poverty / wealth, education, access to knowledge and support services

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • reduce land degradation
  • restore/ rehabilitate severely degraded land
Comments:

Main goals: mitigation / reduction of land degradation
Secondary goals: rehabilitation / reclamation of denuded land

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Soil faced deep trench bunds are structures constructed by excavating trenches following the contour and using the excavated soil to establish compacted bund on the lower side.

Location: Tigray. Kilte Awlaelo

Date: 10/10/2014

Technical knowledge required for field staff / advisors: moderate

Technical knowledge required for land users: low

Main technical functions: control of dispersed runoff: retain / trap, reduction of slope length

Secondary technical functions: increase of infiltration, increase / maintain water stored in soil, increase of groundwater level / recharge of groundwater, sediment retention / trapping, sediment harvesting

Aligned: -contour
Vegetative material: G : grass
Number of plants per (ha): 1600
Vertical interval between rows / strips / blocks (m): 1 - 1.2
Spacing between rows / strips / blocks (m): 10 - 15
Vertical interval within rows / strips / blocks (m): 0.5

Grass species: Elephant grass is mostly planted on the bunds in a single row at spacing of 0.5 m.

Slope (which determines the spacing indicated above): 6.5 and 12%

Gradient along the rows / strips: 0%

Bund/ bank: level
Vertical interval between structures (m): 1 - 1.2
Spacing between structures (m): 10 - 15
Depth of ditches/pits/dams (m): 1
Width of ditches/pits/dams (m): 0.5 - 1
Length of ditches/pits/dams (m): 2 - 3.5
Height of bunds/banks/others (m): 0.75 - 1
Width of bunds/banks/others (m): 0.3 - 1.2
Length of bunds/banks/others (m): 60 - 100

Construction material (earth): Soil excavated from the trenches is used to construct bunds

Slope (which determines the spacing indicated above): 6.5 and 12%

Lateral gradient along the structure: 0%

Vegetation is used for stabilisation of structures.

Author:

Eyasu Yazew, P.O.Box 231, Mekelle University, Mekelle, Ethiopia

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):

Birr

If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:

18,0

Indicate average wage cost of hired labour per day:

2.50

4.3 Establishment activities

Activity Timing (season)
1. Purchase of elephant grass June/July
2. Grass plantation July
3. Contour alignment, marking trench dimensions, trench excavation and construction and compaction of bund January - May

4.4 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 2119,0 2119,0 60,0
Equipment Tools ha 1,0 44,0 44,0
Plant material Seedlings ha 1,0 36,0 36,0
Total costs for establishment of the Technology 2199,0
Total costs for establishment of the Technology in USD 122,17
Comments:

Duration of establishment phase: 48 month(s)

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. Dredging of deposited sediment from trenches and compacting it on the bund January - May

4.6 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 1,0 833,0 833,0 100,0
Total costs for maintenance of the Technology 833,0
Total costs for maintenance of the Technology in USD 46,28
Comments:

Machinery/ tools: Digging hoe, shovel (Costs are included in the structural measures), Line level, tape meter, digging hoe, shovel

The cost was calculated for an average bund length and spacing of 80 m and 12.5 m respectively, which would result in a construction of 10 bunds per ha. In addition, an average trench length and spacing between trenches along the contour of 2.75 m and 0.4 m was considered respectively resulting in 25 trenches per bund and 250 trenches per ha.

The excavation of one deep trench and construction of the corresponding bund requires 3 person days during establishment while maintaining it needs 1.5 person days per year. A single row of grass is planted on the bunds at 0.5 m interval and a person is assumed to plant about 100 seedlings per day. The cost calculation rates apply to 2012. Accordingly, the price of single elephant grass is 0.4 Birr and the daily labour wage is 40 Birr for light work such as grass planting and 50 Birr for medium work such as trench excavation.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Labour, slope, landuse, soil depth.

5. Natural and human environment

5.1 Climate

Annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Specifications/ comments on rainfall:

Average rainfall of 450-550 mm, Main rainy season from Mid-June to August

Agro-climatic zone
  • semi-arid

Thermal climate class: subtropics

5.2 Topography

Slopes on average:
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
Landforms:
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitudinal zone:
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.
Comments and further specifications on topography:

Slopes on average: An average slope of 6.5% is taken for moderate slope and 12% for hill slope.

5.3 Soils

Soil depth on average:
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil):
  • medium (loamy, silty)
  • fine/ heavy (clay)
Topsoil organic matter:
  • medium (1-3%)
  • low (<1%)
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 depth on average: The deep trench should usually be 1 m deep.
Soil texture: Medium (ranked 1) and fine/heavy (ranked 2, Appropriate in case of grazing lands.)
Soil fertility: Low (ranked 1) and medium (Clay soils in rehabilitated grazing lands, ranked 2.)
Topsoil organic matter: Low (more in cultivate lands, ranked 1) and Medium (more in grazing lands, ranked 2)
Soil drainage/infiltration is medium (ranked 1) and poor (in clay soils, ranked 2)
Soil water storage capacity is medium (ranked 1) and high (ranked 2)

5.4 Water availability and quality

Ground water table:

5-50 m

Availability of surface water:

poor/ none

Water quality (untreated):

for agricultural use only (irrigation)

5.5 Biodiversity

Species diversity:
  • low

5.6 Characteristics of land users applying the Technology

Market orientation of production system:
  • subsistence (self-supply)
Off-farm income:
  • less than 10% of all income
Relative level of wealth:
  • poor
  • average
Individuals or groups:
  • groups/ community
Level of mechanization:
  • manual work
  • animal traction
Gender:
  • women
  • men
Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly common / average land users
Population density: 100-200 persons/km2
Annual population growth: 2% - 3%
10% of the land users are rich and own 10% of the land.
60% of the land users are average wealthy and own 55% of the land (35 birr/person/day).
30% of the land users are poor and own 35% of the land.

5.7 Average area of land used by land users applying the Technology

  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Is this considered small-, medium- or large-scale (referring to local context)?
  • small-scale
Comments:

Average land holding is 0.6 ha per household.

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

Land ownership:
  • state
Land use rights:
  • communal (organized)
  • individual

5.9 Access to services and infrastructure

health:
  • poor
  • moderate
  • good
education:
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
markets:
  • poor
  • moderate
  • good
energy:
  • poor
  • moderate
  • good
roads and transport:
  • poor
  • moderate
  • good
drinking water and sanitation:
  • poor
  • moderate
  • good
financial services:
  • poor
  • moderate
  • good
Mobile communication:
  • poor
  • moderate
  • good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

crop production

decreased
increased

fodder production

decreased
increased

fodder quality

decreased
increased

animal production

decreased
increased

production area

decreased
increased
Income and costs

farm income

decreased
increased

workload

increased
decreased

Socio-cultural impacts

food security/ self-sufficiency

reduced
improved

health situation

worsened
improved
Comments/ specify:

Increased investment in health as a result of increased income.

community institutions

weakened
strengthened

SLM/ land degradation knowledge

reduced
improved

situation of socially and economically disadvantaged groups

worsened
improved

Improved livelihoods and human well-being

decreased
increased

Ecological impacts

Water cycle/ runoff

harvesting/ collection of water

reduced
improved

surface runoff

increased
decreased

groundwater table/ aquifer

lowered
recharge
Soil

soil moisture

decreased
increased

soil cover

reduced
improved

soil loss

increased
decreased

6.2 Off-site impacts the Technology has shown

water availability

decreased
increased

downstream flooding

increased
reduced

downstream siltation

increased
decreased

damage on neighbours' fields

increased
reduced

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:

positive

Long-term returns:

positive

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:

positive

Long-term returns:

very positive

6.5 Adoption of the Technology

If available, quantify (no. of households and/ or area covered):

8735

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 51-90%
Comments:

27% of land user families have adopted the Technology with external material support

2541 land user families have adopted the Technology with external material support

73% of land user families have adopted the Technology without any external material support

6194 land user families have adopted the Technology without any external material support

There is a moderate trend towards spontaneous adoption of the Technology

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Reduce soil erosion and increase soil fertility

How can they be sustained / enhanced? Continuous maintenance and excavation of sediment
Increase soil moisture and yield

How can they be sustained / enhanced? Planting grass, sunflower and other fodder plants on the bund to increase conservation as well as economic benefits
Reduce surface runoff, increase water storage in trenches and recharging downstream springs

How can they be sustained / enhanced? Continuous maintenance and excavation of sediment
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Decreased slope length, reduced runoff amount and velocity and soil erosion

How can they be sustained / enhanced? Continuous maintenance of the structures and controlled grazing of the grass
Increase in rainwater harvesting, soil moisture and groundwater recharge

How can they be sustained / enhanced? Continuous maintenance of the structures
Increase in crop and fodder production

How can they be sustained / enhanced? Planting improved and high yielding crop and fodder varieties

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?
Reduced farm land Increase the productivity of the bunds.
Increased labour requirement Mass mobilization and/or increased incentives to households.
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Labour intensive Mass mobilization and improving the design.
Reduced farm land Increasing the spacing and reduce dimension of bunds without compromising their effectiveness.

7. References and links

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Staff members of the Kilte Awlaelo Wereda Office of Agriculture and Rural Development

Title, author, year, ISBN:

Carucci, V. (2000). Guidelines on Water Harvesting and Soil Conservation for Moisture Deficit Areas in Ethiopia:the productive use of water and soil. First draft manual for trainers, Addis Ababa, Ethiopia.

Title, author, year, ISBN:

Lakew, D., Carucci, V., Asrat, W. and Yitayew, A. (2005). Community Based Participatory Watershed Development: A guideline. Part I, first edition, Ministry of Agriculture and Rural Development, Addis Ababa, Ethiopia.

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