Technologies

Gabion check dam [Tunisia]

Ouvrage en gabion

technologies_1400 - Tunisia

Completeness: 76%

1. General information

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

Key resource person(s)

SLM specialist:

Mongi Sghaier

Institut des Régions Arides IRA

Tunisia

SLM specialist:
SLM specialist:

Chniter Mongi

Commissariats Régionaux au Développement Agricole CRDA

Tunisia

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Institut des Régions Arides de Médenine (Institut des Régions Arides de Médenine) - Tunisia
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Commissariats Régionaux au Développement Agricole (CRDA) - Tunisia

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. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

The technology of check dam is a technique consisting of binding different gabion cages filled with small stones together to form a complete flexible gabion unit.

2.2 Detailed description of the Technology

Description:

In order to slow down the water flow in the wadi courses and improve its infiltration into deeper soil layers and geologic formations, small check dams are installed on the wadi beds. They are usually positioned in series, with a spacing of 100-500m. These dams are made of gabion.
The gabion technique has been first introduced in the civil engineering domain. They are largely used since then and found many applications.
A gabion is a cage which has a cubic shape filled with stony material of suitable diameter enclosed in metal grating keeping the stones together and stops them from moving under the pressure of water. The gabion is normally the name of the cage only but it is also used frequently for the whole structure itself. The technique of gabion check dam consists in binding different cages together to form a complete gabion unit. The average height varies from 1 to 4 m and its length is a function of the width of the wadi bed (Royet, 1992).

2.3 Photos of the Technology

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

Country:

Tunisia

Region/ State/ Province:

Medenine

Further specification of location:

Beni Kedhache - Bhayra

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

This technique is practiced in the Jeffara plain as well as in the mountain region.

2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • through projects/ external interventions
Comments (type of project, etc.):

In the provinnce of Medenine, the first gabion check dams used for groudwater recharge and spreading have been constructed starting from 1985.

3. Classification of the SLM Technology

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

Cropland

Cropland

  • Tree and shrub cropping
Number of growing seasons per year:
  • 1
Specify:

Longest growing period in days: 180Longest growing period from month to month: Oct - Mar

Grazing land

Grazing land

  • Extensive grazing land
Comments:

Major land use problems (compiler’s opinion): -Degradation of soil and land cover
-Loss of water and soil ressources
-Flooding

Major land use problems (land users’ perception): Loss of water resources by flow out from the watershed

Future (final) land use (after implementation of SLM Technology): Cropland: Ct: Tree and shrub cropping

Constraints of wadi beds: floods

3.3 Has land use changed due to the implementation of the Technology?

Has land use changed due to the implementation of the Technology?
  • Yes (Please fill out the questions below with regard to the land use before implementation of the Technology)
Land use mixed within the same land unit:

Ja

Cropland

Cropland

  • Tree and shrub cropping
Grazing land

Grazing land

Comments:

Constraints of wadi beds: floods

3.5 SLM group to which the Technology belongs

  • water harvesting
  • irrigation management (incl. water supply, drainage)

3.6 SLM measures comprising the Technology

structural measures

structural measures

  • S5: Dams, pans, ponds
Comments:

Main measures: structural measures

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
  • Wr: riverbank erosion
  • Wo: offsite degradation effects
Comments:

Main type of degradation addressed: Wg: gully erosion / gullying

Secondary types of degradation addressed: Wt: loss of topsoil / surface erosion, Wr: riverbank erosion, Wo: offsite degradation effects

Main causes of degradation: deforestation / removal of natural vegetation (incl. forest fires) (intensity)

Secondary causes of degradation: over-exploitation of vegetation for domestic use, overgrazing (degradation of land cover), Heavy / extreme rainfall (intensity/amounts)

3.8 Prevention, reduction, or restoration of land degradation

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

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

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

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Gabion check dam is made of galvanised blocks filled with stones.

Location: Jeffara plain. Medenine, Tunisia

Date: January 2009

Technical knowledge required for field staff / advisors: high

Technical knowledge required for land users: moderate

Main technical functions: increase of groundwater level / recharge of groundwater

Secondary technical functions: increase of infiltration, increase / maintain water stored in soil, water harvesting / increase water supply, water spreading, sediment retention / trapping, sediment harvesting

Dam/ pan/ pond
Vertical interval between structures (m): 3-5
Spacing between structures (m): 100-500
Height of bunds/banks/others (m): 1-4
Width of bunds/banks/others (m): 4-6
Length of bunds/banks/others (m): 30-100

Construction material (stone): The average length varies between 15 and 30 cm

Construction material (other): Gabion: Galvanised cages of 1 to 3 m3.

Slope (which determines the spacing indicated above): 3-8%

Lateral gradient along the structure: <1%

Specification of dams/ pans/ ponds: Capacity 5000-15000m3

Catchment area: 1-3 ham2

Beneficial area: 30-100ham2

Other specifications: The whole structure has the form of a spillway.

Author:

Ouessar M., Medenine, Tunisia

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):

Tunisian Dinars

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

1.3

Indicate average wage cost of hired labour per day:

10.00

4.3 Establishment activities

Activity Timing (season)
1. Topographic survey and selection of the site
2. Digging of the basement
3. Gabion installation

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 Dam 1.0 5000.0 5000.0 100.0
Construction material Construction material dam 1.0 5000.0 5000.0 100.0
Construction material Gabion cages dam 1.0 10000.0 10000.0 100.0
Total costs for establishment of the Technology 20000.0
Total costs for establishment of the Technology in USD 15384.62
Comments:

Duration of establishment phase: 1.5 month(s)

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. Repair of breaks each 1 to 2 years
2. Reconstruction After heavy floods (once in 5-10 years)

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 dam 1.0 500.0 500.0 100.0
Construction material construction material dam 1.0 500.0 500.0 100.0
Construction material Gabion cages dam 1.0 1000.0 1000.0 100.0
Total costs for maintenance of the Technology 2000.0
Total costs for maintenance of the Technology in USD 1538.46
Comments:

Machinery/ tools: Generally, the work is manual but tractors can be used too.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

construction materials

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:

Dry period from April to September

Agro-climatic zone
  • 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.

5.4 Water availability and quality

Ground water table:

5-50 m

Water quality (untreated):

poor drinking water (treatment required)

Comments and further specifications on water quality and quantity:

Availability of surface water: excess, medium, poor/ none (The wadi is almost always dry)
Water quality (untreated): Poor drinking water (treatement required) (from cisterns and wells) but good drinking water if pumped in the deep aquifer (100-300m)

5.5 Biodiversity

Species diversity:
  • medium

5.6 Characteristics of land users applying the Technology

Off-farm income:
  • > 50% of all income
Relative level of wealth:
  • average
  • rich
Individuals or groups:
  • groups/ community
Gender:
  • men
Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly common / average land users

Difference in the involvement of women and men: Historically, the hard work is done by men.

Population density: 10-50 persons/km2

Annual population growth: < 0.5%

30% of the land users are rich and own 50% of the land.
60% of the land users are average wealthy and own 30% of the land.
10% of the land users are poor and own 20% of the land.

Off-farm income specification: Off-farm incomes come from migration, construction works, commerce, tourism sector, administration or informal activities.

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

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

Land ownership:
  • state
Land use rights:
  • communal (organized)
Water use rights:
  • communal (organized)
Comments:

Generally, this technology is applied in the wadi beds which is considered as state owned but the local community can have access.

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

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

Socio-cultural impacts

Improved livelihoods and human well-being

Comments/ specify:

Recharge of groundwater (water less salty and more available) and protection against the floods.

Ecological impacts

Water cycle/ runoff

water quantity

decreased
increased

water quality

decreased
increased

surface runoff

increased
decreased

groundwater table/ aquifer

lowered
recharge
Soil

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

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

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
Hydrological disasters
How does the Technology cope with it?
general (river) flood well

6.4 Cost-benefit analysis

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

slightly negative

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:

positive

Comments:

Gabion chech dams are financed by the State

6.5 Adoption of the Technology

Comments:

Comments on acceptance with external material support: This technology is supposed to be implemented solely by the government agencicies but in some cases the farmers can make use of it.

Comments on spontaneous adoption: This technology is supposed to be implemented solely by the government agencicies but in some cases the farmers can make use of it.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Efficient structures

How can they be sustained / enhanced? Regular and good maintenance
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Robust and flexible structures

How can they be sustained / enhanced? Regular and good maintenance

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?
They can not be fully exploited by the farmers Change regulations.
Very expensive and cost not affordable by normal farmers Continue subsidising by the government.
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Accumulation of sediments Desilting

7. References and links

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Yahyaoui, H., Chaieb, H., Ouessar, M. 2002. Impact des travaux de conservation des eaux et des sols sur la recharge de la nappe de Zeuss-Koutine (Sud-est tunisien). TRMP paper n° 40, Wageningen University, The Netherlands, pp: 71-86.

Available from where? Costs?

IRA - Medenine; DGRE - Tunis

Title, author, year, ISBN:

Boufelgha et al. 1998. Comportement des ouvrages CES dans le bassin versant d’oued Koutine lors de la crue d'Octobre 1998. Rapport interne, CRDA, Médenine

Available from where? Costs?

CRDA Médenine

Title, author, year, ISBN:

Chniter et al. 2007. Comportement des ouvrages CES dans le bassin versant d’oued Oum Zessar lors de la crue de 22 Février 2007. Rapport interne, CRDA, Médenine

Available from where? Costs?

CRDA Médenine

Title, author, year, ISBN:

Sghaier, M., Mahdhi, N., De Graaff, J., Ouessar, M. 2002. Economic assessment of soil and water conservation works: case of the wadi Oum Zessar watershed in south-eastern Tunisia.TRMP paper n° 40, Wageningen University, The Netherlands, pp: 101-113.

Available from where? Costs?

IRA

Title, author, year, ISBN:

Mahdhi, N., Sghaier, M, Ouessar, M. 2000. Analyse d’impacts des aménagements de CES en zone aride: cas du bassin versant d’Oued Oum Zessar. Technical report, WAHIA project, IRA, Tunisia.

Available from where? Costs?

IRA

Title, author, year, ISBN:

Yahyaoui, H., Ouessar, M. 2000. Abstraction and recharge impacts on the ground water in the arid regions of Tunisia: Case of Zeuss-Koutine water table. UNU Desertification Series, 2: 72-78.

Available from where? Costs?

IRA

Title, author, year, ISBN:

Ouessar M. 2007. Hydrological impacts of rainwater harvesting in wadi Oum Zessar watershed (Southern Tunisia). Ph.D. thesis, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium, 154 pp.

Available from where? Costs?

IRA - Médenine;

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