Technologies

Sub-surface drainage on irrigated lands [South Africa]

Ondergrondse dreinering, brakdreinering, natdreinering (Afrikaans)

technologies_1126 - South Africa

Completeness: 71%

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:

Richter Francois

Department of Agriculture, Western Cape, Wellington

South Africa

SLM specialist:

Smit Jan

Department of Agriculture, Western Cape, Wellington

South Africa

SLM specialist:

Steyn Francis

Department of Agriculture, Western Cape, George

South Africa

SLM specialist:

Oliver Gert

Department of Agriculture, Western Cape, Moorreesburg

South Africa

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Dept. of Agriculture, Western Cape (Dept. of Agriculture, Western Cape) - South Africa

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:

Drainage of saturated and salinised soils by means of sub-soil drainage pipes

2.2 Detailed description of the Technology

Description:

There is a lot of soil, wind and water erosion in this area. River erosion, not related to this SWC, is a problem over the whole area (on average 20 t/ha/y). Sheet and gully erosion occurs on commercial land. The whole area along the rivers varies up to 50 km.

In some places drainage is inadequate and water-logging occurs. A system of sub-soil perforated pipes with surrounding filters was installed. Pipes laid at spacing determined according to the site conditions.
The overall purpose was to limit the level of the water table in the soil profile and remove salts, to provide an adequately aerated zone in the soil for a crops’ root system.

The system must be planned by a suitably trained person and constructed by an expert.

Drainage pipes must be flushed at least annually and roots removed whenever present.

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:

South Africa

Region/ State/ Province:

Western Cape Province

Further specification of location:

Southern Cape, Boland, Swartland

Specify the spread of the Technology:
  • evenly spread over an area
If the Technology is evenly spread over an area, specify area covered (in km2):

240,0

If precise area is not known, indicate approximate area covered:
  • 100-1,000 km2
Comments:

Total area covered by the SLM Technology is 240 km2.

Technology also applied in other provinces. Boland 60% under agriculture and from this 20% under this technology. Swartland mainly wheat, 10% under irrigation and from this 20% is already drained. Southern Cape: 20% irrigated of which 20% is drained, 95% commercial farmers. Other parts in SA: KwaZulu/Natal (Pongola), Free state (Rietriver, Orange River), Northern Cape (Vaalharts, Douglas, Upington), Eastern Cape (Fish River, Sundays River, Langkloof)

2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • less than 10 years ago (recently)

2.7 Introduction of the Technology

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

Holland, USA - literature

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

  • Tree and shrub cropping
Tree and shrub cropping - Specify crops:
  • citrus
  • grapes
  • pome fruits (apples, pears, quinces, etc.)
Number of growing seasons per year:
  • 1
Specify:

Longest growing period in days: 120; Longest growing period from month to month: Sep - Mar

Comments:

major food crop: Deciduous fruit/citrus
other: Grapes

Major land use problems (compiler’s opinion): Bad management (over irrigation). The washing of soil from one land to the other. High winter rainfall.

Major land use problems (land users’ perception): Loss of crop production due to saturation/salinisation of soil. Not putting money back what would be expect, because not enough growth, reduced crop roots deeper in soil and no growth in the area, slanted growth - salinised soils.

3.5 SLM group to which the Technology belongs

  • irrigation management (incl. water supply, drainage)

3.6 SLM measures comprising the Technology

structural measures

structural measures

  • S7: Water harvesting/ supply/ irrigation equipment

3.7 Main types of land degradation addressed by the Technology

chemical soil deterioration

chemical soil deterioration

  • Cs: salinization/ alkalinization
physical soil deterioration

physical soil deterioration

  • Pw: waterlogging
Comments:

Secondary types of degradation addressed: Cs: salinisation / alkalinisation

Main causes of degradation: other natural causes (avalanches, volcanic eruptions, mud flows, highly susceptible natural resources, extreme topography, etc.) specify (Rising water tables - As result of over irrigation, leaking dams and canals)

Secondary causes of degradation: education, access to knowledge and support services (Lack of knowledge - Build dams & canals that leak, over irrigation)

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

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

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Technical knowledge required for field staff / advisors: high

Technical knowledge required for land users: moderate

Main technical functions: Removal of salts from soils, Decrease water table, Increase of soil aeration

Structural measure: subsurface drains
Vertical interval between structures (m): n/a
Spacing between structures (m): 40-80
Depth of ditches/pits/dams (m): 1.5-2.5
Length of ditches/pits/dams (m): 300

Construction material (other): Plastic perforated pipe with crushed stone filter

Slope (which determines the spacing indicated above): 2%

Lateral gradient along the structure: 2%

4.2 General information regarding the calculation of inputs and costs

Specify currency used for cost calculations:
  • USD
Indicate average wage cost of hired labour per day:

15.00

4.3 Establishment activities

Activity Timing (season)
1. Dig trench 150m/day, dry season Dec-Apr
2. Lay pipe 150m/day, dry season Dec-Apr
3. Place filter material 150m/day, dry season Dec-Apr
4. Build manholes 150m/day, dry season Dec-Apr
5. Backfill trench 150m/day, dry season Dec-Apr

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 Install drainage system persons/day/ha 10,0 15,0 150,0 75,0
Equipment Machine use ha 1,0 450,0 450,0 75,0
Construction material Stone ha 1,0 100,0 100,0 75,0
Construction material Pipes ha 1,0 240,0 240,0 75,0
Construction material Manholes ha 1,0 250,0 250,0 75,0
Other Contractor overheads ha 1,0 200,0 200,0 75,0
Total costs for establishment of the Technology 1390,0
Total costs for establishment of the Technology in USD 1390,0
Comments:

Duration of establishment phase: 12 month(s)

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. Flush pipes with water All year/2 times a year
2. Cut roots in pipes When required/
3. Clean manholes All year/2 times a year (was reduced)

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 Maintenance ha 1,0 25,0 25,0 100,0
Total costs for maintenance of the Technology 25,0
Total costs for maintenance of the Technology in USD 25,0
Comments:

Length of pipe (grid at 60 m spacing - i.e. pipe that average team lays in one day)

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

Suitability of soil for drainage (greater depth and permeability = lower costs.

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:

501-750 mm is closer to the mountain

Agro-climatic zone
  • semi-arid

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.

5.3 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):
  • coarse/ light (sandy)
  • medium (loamy, silty)
Topsoil organic matter:
  • 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 fertility is medium - low

Soil drainage / infiltration is medium

Soil water storage capacity is low

5.6 Characteristics of land users applying the Technology

Market orientation of production system:
  • mixed (subsistence/ commercial)
  • commercial/ market
Off-farm income:
  • less than 10% of all income
Relative level of wealth:
  • average
  • rich
Level of mechanization:
  • mechanized/ motorized
Indicate other relevant characteristics of the land users:

Population density: 50-100 persons/km2

Annual population growth: 1% - 2%

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

Off-farm income specification: Most of them are only farmers.

Level of mechanization: Tractors, trailer, plough, crop sprayers

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
Comments:

Average area of land owned or leased by land users applying the Technology: Also 100-500 ha, but production capacity on all is really the same

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

Land ownership:
  • group
  • individual, titled
Land use rights:
  • communal (organized)
  • individual

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

crop production

decreased
increased

land management

hindered
simplified
Comments/ specify:

During rainy season (winter) tractor can drive on field without getting stuck in the mud, but construction process and maintenance of intercrops farming activities (negligble)

Income and costs

farm income

decreased
increased
Other socio-economic impacts

on farm employment

decreased
increased
Comments/ specify:

due to higher workload

input constraints

increased
decreased
Comments/ specify:

Construction must be financed

Socio-cultural impacts

community institutions

weakened
strengthened

SLM/ land degradation knowledge

reduced
improved

Ecological impacts

Water cycle/ runoff

surface runoff

increased
decreased

excess water drainage

reduced
improved
Soil

soil cover

reduced
improved
Comments/ specify:

Less bare soil

Other ecological impacts

soil fertility

decreased
increased

restoration of original topsoil aeration

reduced
improved
Comments/ specify:

Most of this soils have originally been saturated

6.2 Off-site impacts the Technology has shown

reliable and stable stream flows in dry season

reduced
increased

downslope salinatation

improved
reduced

6.4 Cost-benefit analysis

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

slightly positive

Long-term returns:

very positive

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

very positive

Long-term returns:

very positive

6.5 Adoption of the Technology

  • 11-50%
If available, quantify (no. of households and/ or area covered):

50 percent of all households in this area

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 11-50%
Comments:

50% of land user families have adopted the Technology with external material support

Comments on acceptance with external material support: estimates

50% of land user families have adopted the Technology without any external material support

Comments on spontaneous adoption: estimates

There is a moderate trend towards spontaneous adoption of the Technology

Comments on adoption trend: More and more farmers are coming to do ditch drainage because there's more money available, if waiting period is more than 3 months the service from government is free of charge.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Greatly improved crop yield
Improved access for mechanisation
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Greatly improved crop yield
Improved access for mechanisation

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?
Initial capital outlay
Slight decreased in run-off water quality
Insufficient information on soil properties
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Initial capital outlay
Slight decreased in run-off water quality
Insufficient information on soil properties

7. References and links

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Drainage Works for Western Cape (Afrikaans). July 1988.

Available from where? Costs?

HE King

Title, author, year, ISBN:

National Drainage Manual (Afrikaans)

Available from where? Costs?

NDA - photostat costs

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