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)

DESIRE (EU-DES!RE)

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

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

1.3 Conditions regarding the use of data documented through WOCAT

When were the data compiled (in the field)?

10/06/2011

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

Yes

1.5 Reference to Questionnaire(s) on SLM Approaches

2.1 Short description of the Technology

Definition of the Technology:

A recharge well comprises a drilled hole, up to 30-40 m deep that reaches the water table, and a surrounding filter used to allow the direct injection of floodwater into the aquifer.

2.2 Detailed description of the Technology

Description:

The main worldwide used methods to enhance groundwater replenishment are through recharge basins or recharge wells. Though groundwater recharge aiming at storage of water in the periods of abundance for recovery in times of drought has a long history dating back millennia, the recharge wells began to be used only in the twentieth century, especially during the Second World War following concerns on attacks of the water supply facilities. Its use was extended later to sea intrusion control, treated waste water, water harvesting in the dry areas, and strategic water storage.

Purpose of the Technology: Recharge wells are used in combination with gabion check dams to enhance the infiltration of floodwater into the aquifer. In areas where the permeability of the underlying bedrock in front of a gabion is judged too low, recharge wells could be installed in wadi (ephemeral river) beds. Water is retained by the gabion check dam and it flows through the recharge well allowing accelerated percolation into the aquifer.

Establishment / maintenance activities and inputs: A recharge well consists of a long inner tube surrounded by an outer tube, the circumference of which ranges between 1 and 2 m. The area between the tubes is filled with river bed gravel which acts as a sediment filter. Water enters the well through rectangular-shaped openings (almost 20 cm long and a few mm in width) located in the outer tube, and it flows in the inner hole having passed through the gravel and the rectangular shaped openings of the dill hole. The above-ground height is around 2 to 3 m whereas the depth is linked to the depth of the water table (normally up to 40 m). The drill hole connects directly with the aquifer, where it is connected either directly with the water table or indirectly via cracks. Pond volume is dependent on the size of the gabion check dam but generally ranges between 500 and 3000 m3. The filtered water can directly flow into the aquifer at a rate exceeding what would occur naturally through the soil and the underlying strata.
The design should be conducted primarily by a hydrogeologist and a soil and water conservation specialist in order to determine the potential sites and the required drilling equipment. Drilling needs to be carried out by a specialized company.
Depending on the geological setting, the overall cost is around 5000 to 10000 US$. The recharge wells are used to recharge the deep groundwater aquifers, which are mainly exploited by government agencies. However, private irrigated farms are benefiting indirectly by increased groundwater availability.

Natural / human environment: This technique has been first tried for the replenishment of the Zeuss-Koutine aquifer (south east Tunisia).

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:

• 10-50 years ago

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• through projects/ external interventions

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

Comments:

Major land use problems (compiler’s opinion): Runoff water loss, riverbank erosion, flooding risk, aridity

Major land use problems (land users’ perception): water loss

Constraints of wadi beds

3.3 Further information about land use

Number of growing seasons per year:

• 1

Specify:

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

3.4 SLM group to which the Technology belongs

• water harvesting
• ground water management

3.5 Spread of the Technology

Specify the spread of the Technology:

• evenly spread over an area

If the Technology is evenly spread over an area, indicate approximate area covered:

• 10-100 km2

3.6 SLM measures comprising the Technology

Comments:

Main measures: structural measures

3.7 Main types of land degradation addressed by the Technology

Comments:

Main type of degradation addressed: Ha: aridification

Secondary types of degradation addressed: Wr: riverbank erosion, Wo: offsite degradation effects, Hq: decline of groundwater quality

Main causes of degradation: over abstraction / excessive withdrawal of water (for irrigation, industry, etc.)

Secondary causes of degradation: disturbance of water cycle (infiltration / runoff), 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
• reduce land degradation

Comments:

Main goals: prevention of land degradation

Secondary goals: mitigation / reduction of land degradation

4.1 Technical drawing of the Technology

4.2 Technical specifications/ explanations of technical drawing

Schematic representation of the main components of a recharge well. The flood water retained behind the gabion check dam flows through the outer tube and the gravel filter into the water table. Clogging of the filter is one of the major problems to be considered and solved.

south east Tunisia

Date: January 2009

Technical knowledge required for field staff / advisors: moderate

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

Secondary technical functions: control of concentrated runoff: retain / trap, water harvesting / increase water supply

Structural measure: Casting tube
Spacing between structures (m): 100-500
Depth of ditches/pits/dams (m): 30-40m
Width of ditches/pits/dams (m): 0.5-1m

Structural measure: Filter

Construction material (other): Plastic/iron: the casting tube, Gravel: for the filter

4.3 General information regarding the calculation of inputs and costs

other/ national currency (specify):

TND

Indicate exchange rate from USD to local currency (if relevant): 1 USD =:

1.3

4.4 Establishment activities

	Activity	Type of measure	Timing
1.	Drilling	Structural
2.	Installation	Structural

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	7000.0	7000.0
Construction material		ha	1.0	1000.0	1000.0
Total costs for establishment of the Technology					8000.0

Comments:

Duration of establishment phase: 3 month(s)

4.6 Maintenance/ recurrent activities

	Activity	Type of measure	Timing/ frequency
1.	Desilting of the filter	Structural	Ounce in 1-3years (floods)
2.	Repairs	Structural

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	500.0	500.0
Construction material		ha	1.0	100.0	100.0
Total costs for maintenance of the Technology					600.0

4.8 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Labour is the most determining factor affecting the costs.

5.1 Climate

5.2 Topography

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 fertility is very low
Soil drainage / infiltration is medium
Soil water storage is medium

5.4 Water availability and quality

Comments and further specifications on water quality and quantity:

Seasonal fluctuations: Availability of surface water is poor/none but with periods of excess (e.g. flood)

5.5 Biodiversity

5.6 Characteristics of land users applying the Technology

Indicate other relevant characteristics of the land users:

Population density: 10-50 persons/km2
Annual population growth: 0.5% - 1%
70% of the land users are average wealthy and own 75% of the land.

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:

• communal (organized)

Water use rights:

• communal (organized)

Comments:

The recharge wells are used to recharge the deep groundwater aquifers which are mainly exploited by the government agencies. However, private irrigated farms could benefit indirectly, by increased groundwater availability.

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Water availability and quality

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Other ecological impacts

6.2 Off-site impacts the Technology has shown

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

Other climate-related consequences

Other climate-related consequences

	How does the Technology cope with it?
reduced growing period	well
extreme floods	not well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

Comments:

Long-term benefits are slightly reduced due to silting problems.

6.5 Adoption of the Technology

Of all those who have adopted the Technology, how many have did so spontaneously, i.e. without receiving any material incentives/ payments?

• 0-10%

Comments:

Comments on acceptance with external material support: It is solely constrcuted by the government agencies.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Replenishment of the aquifer How can they be sustained / enhanced? Good selection of the site and drilling methods

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Enhance groundwater level and quality (reduce salinity)

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?
Retain water for dowstreams users	Proper watershed management plan

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view	How can they be overcome?
Silting up of the filter	Maintenance of the filters.
Malfunction due to aquifer geometry and characteristics	Good selection of the sites

7.2 References to available publications

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, CRDA-Medenine, UNU

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 (Médenine: Sud-est tunisien). TRMP paper n° 40, Wageningen University, The Netherlands, pp: 71-86.

Available from where? Costs?

IRA, Wegeningen University (NL),

Title, author, year, ISBN:

Temmerman, S. 2004. Evaluation of the efficiency of recharge wells on the water supply to the water table in South Tunisia. Graduation dissertation, Ghent University, Belgium.

Available from where? Costs?

IRA, Gent University (BE)

Title, author, year, ISBN:

Genin, D., Guillaume, H., Ouessar, M., Ouled Belgacem, A., Romagny, B., Sghaier, M., Taamallah, H. (eds) 2006. Entre la désertification et le développement : la Jeffara tunisienne. CERES, Tunis, 351 pp.

Available from where? Costs?

IRA, IRD

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, Gent University (BE)