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Technologies
Inactive

Infiltration ditches and ponding banks [Namibia]

Ovala

technologies_2989 - Namibia

Completeness: 96%

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)

land user:

Kahl Uwe

+264 67 290004 / +264811486666

uwe2008@iway.na

Farm Middelplaats

P.O. Box 213 Otjiwarongo

Namibia

SLM specialist:
SLM specialist:

Pringle Hugh

+61 418415269

hpringle1@bigpond.com

Ecosystem Management Understanding

P.O. Box 8522 Alice Springs NT 0871

Australia

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)
Southern African Science Service Centre for climate change and Adaptive Land management (SASSCAL)
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Namibia University of Science and Technology ( NUST) - Namibia
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
German Federal Ministry of Education and Research (BMBF) - Germany

1.3 Conditions regarding the use of data documented through WOCAT

When were the data compiled (in the field)?

2017

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

Ja

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

Geen

1.5 Reference to Questionnaire(s) on SLM Approaches

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Construction of contour ditches and ponding banks to trap and infiltrate rainwater for improved growth of plants and replenishment of ground water, while gently spilling any excess water safely over wide areas to avoid erosion during intense rain. It must be integrated with other technologies that treat the root causes of rangeland degradation rather than used as a stand-alone technology to treat symptoms.

2.2 Detailed description of the Technology

Description:

The technology is applied in rangeland where runoff occurs during and soon after rain, where the soil is deep enough to dig contour ditches and construct ponding banks, where there is sufficient gentle slope over a wide enough area for safely spilling excess water during intense rain, where valuable plants can establish themselves or be grown to benefit from the extra infiltrated rainwater, where the costs of earthmoving can soon be recovered through sale of extra production from the valuable plants and, most importantly, where the root causes of rangeland degradation have been addressed, usually through management of grazing and fires. At the appropriate area, contour lines are marked out by any available technology such as laser or dumpy level or mapped by drone. Where bushes grow densely, it may be necessary to clear narrow contour strips while leaving larger trees in place. Ditches can be dug to any depth down to approximately 50cm by mechanised grader or backhoe (a loader or digger attached to a tractor), or manually by pick and spade. The soil should ideally first be ripped where dug soil for the bund will be heaped, to ensure a firm foundation for the heaped soil to form a bund. To stabilise the bund, it should be compacted and creeping herbaceous plants should be encouraged to grow on it. Where water is to be spilled if ditches are full, either less soil needs to be heaped there or, if the ditch is deep enough, the natural ground surface can serve as spillway by avoiding to heap soil on it. In situations where excess water can safely be spilled from outward curves of the down-slope side of a long ditch, the dug soil can be placed as a bund below the long sections of ditch where water does not need to spill. In situations where excess water should rather be spilled evenly over the whole length of ditch, then either a second ditch can be graded below the first ditch, with the dug soil heaped upslope, or all of the dug soil needs to be moved and put to use elsewhere. Such soil could be used for building humps to divert flowing water out of tracks and back into natural flow paths, or to construct banks that divert water flowing down shallow gullies into contour ditches. Since it is almost impossible to dig exactly on contour, water starts to spill over the slightly lower edges of the ditch before the volume of water flow increases sufficiently to spill over the whole edge of the ditch. This results in self reinforcement over successive rainfall periods because herbaceous plants grow more densely at the slightly lower edges due to the greater amount of water that previously spilled there, resulting in more sediment being trapped there and consequent raising of the soil level, also by puffing up of the soil from their root growth and exudates which feed soil organisms. Eventually the previously lower sections are raised higher than other sections of the ditch edge, where subsequent spills wet the soil more for denser plant growth, and this slow self-reinforcing effect continues indefinitely. To avoid spillage over the end of each ditch, a short upward curve is built in when digging the ditch and heaping the bund. Organic material can also be placed in the ditch, or in larger settling ponds along the ditch, to improve nutrient cycling. Infiltration ditches were constructed at intervals of 0.5m height on a 30ha densely bushed portion of Farm Middleplaats and trees were planted below the ditches to grow into a fruitful landscape. Species included large canopy trees such as Faidherbia albida and Acacia erioloba, shorter thornless trees for “chop and drop” mulching, such as Peltophorum africanum and Bolusanthus speciosus, and trees that produce fruits, such as Sclerocarya birrea and Berchemia discolor, or edible leaves, such as Moringa oleifera. The tree seedlings were raised in a nursery on the farm, and he fence around the 30ha had to be strengthened to protect the planted seedlings from oryx. In addition, it was necessary to water the seedlings in the landscape for the first year or two until well established, On another portion of the farm where bushes had previously been cleared and the soil was consequently less fertile, ponding banks of approximately 1m height were constructed, especially in locations where it appeared that water had ponded naturally in the past. The ponded water encourages growth of herbaceous plants, especially where soil is scraped from below the bank so that the soil on its upper side remains undisturbed. A few grasses were dug from a wetland and brought to the farm for later transplanting of propagules into the ponded areas.

2.3 Photos of the Technology

2.4 Videos of the Technology

Comments, short description:

https://www.youtube.com/watch?v=6C4V_Cib8ts
Only a short section in the film from 18m07s to 19m15s

Date:

08/04/2015

Location:

Farm Middelplaats and KAYEC campus, both in Namibia

Name of videographer:

Andrew Botelle

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

Country:

Namibia

Region/ State/ Province:

Otjozondjupa and Khomas Retions

2.6 Date of implementation

Indicate year of implementation:

2014

2.7 Introduction of the Technology

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

Projects involving students

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

  • improve production
  • reduce, prevent, restore land degradation
  • preserve/ improve biodiversity
  • create beneficial economic impact

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

Grazing land

Grazing land

Extensive grazing land:
  • Ranching
Main animal species and products:

Beef cattle and game animals

3.3 Further information about land use

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

Except for Initial watering of planted tree seedlings, which was necessitated by drought

Number of growing seasons per year:
  • 1
Livestock density (if relevant):

10ha/LSU averaged out over time and not continuous

3.4 SLM group to which the Technology belongs

  • agroforestry
  • pastoralism and grazing land management
  • water harvesting

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:
  • 0.1-1 km2

3.6 SLM measures comprising the Technology

vegetative measures

vegetative measures

  • V1: Tree and shrub cover
  • V2: Grasses and perennial herbaceous plants
  • V3: Clearing of vegetation
structural measures

structural measures

  • S2: Bunds, banks
  • S4: Level ditches, pits
management measures

management measures

  • M2: Change of management/ intensity level
  • M5: Control/ change of species composition

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
water degradation

water degradation

  • Hg: change in groundwater/aquifer level

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

Author:

Ibo Zimmermann

Date:

21/07/2017

4.2 Technical specifications/ explanations of technical drawing

Contour strips were cleared by bulldozer at 0.5m height intervals on land with a gradient of approximately 1:100. A line was ripped approximately 0.6m deep, over which soil was heaped for a bund by a grader when digging a ditch on its upper side to hold rainwater at a depth of approximately 0.5m. The ends were hooked upwards by approximately 2m to avoid spillage there, while spillways were created by lowering a 10m length of the bund and staggered between ditches to zig-zag the spilled water slowly down the landscape. A variety of tree seedlings were planted below ditches to provide tall canopies, chop-and-drop mulching and edible leaves or fruits, at intervals of approximately 5m.

4.3 General information regarding the calculation of inputs and costs

Specify how costs and inputs were calculated:
  • per Technology area
Indicate size and area unit:

30ha (contour ditches only)

other/ national currency (specify):

NAD

Indicate average wage cost of hired labour per day:

72 NAD

4.4 Establishment activities

Activity Type of measure Timing
1. Marking of contour lines Structural Dry season
2. Clearing of bush strips along contour Structural Dry season
3. Ripping along contour Structural Dry season
4. Digging ditch and heaping bund over ripline Structural Start of rains
5. Raising tree seedlings in nursery Vegetative Mostly dry season
6. Planting tree seedlings below ditches Vegetative Rainy season
7. Watering tree seedlings Vegetative Dry season
8. Strengthening fence around landscape to exclude oryx Structural When needed

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 Marking of contour lines Person days 6.0 72.0 432.0 100.0
Labour Raising tree seedlings in nursery Person days 20.0 72.0 1440.0 100.0
Labour Planting tree seedlings below ditches Person days 10.0 72.0 720.0 100.0
Labour Watering every 10 days in first year, except after rain Person days 150.0 72.0 10800.0 100.0
Equipment Strengthening fence to exclude oryx (Labour) Person days 100.0 72.0 7200.0 100.0
Equipment Bulldozer to clear strips and rip Bulldozer hours 89.0 850.0 75650.0 100.0
Equipment Grader to dig ditches and heap bunds Grader hours 35.0 650.0 22750.0 100.0
Equipment Diesel for bulldozer and grader Litres 1000.0 12.0 12000.0 100.0
Equipment Tractor & 7000 lt water trailer every 10 days in first year, except after rain Tractor days 30.0 1250.0 37500.0 100.0
Plant material 500 Plastic bags / seeds with soil to raise seedllngs Filled growing bags 500.0 4.0 2000.0 100.0
Construction material Fencing wire and posts to strengthen fence around fruitful landscape km of fencing 3.0 2200.0 6600.0 100.0
Total costs for establishment of the Technology 177092.0

4.6 Maintenance/ recurrent activities

Activity Type of measure Timing/ frequency
1. Maintenance of ditches and bunds by grader Structural Rainy 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
Equipment Grader cost to maintain the swales every 3 – 4 years Grader hours 8.0 700.0 5600.0 100.0
Total costs for maintenance of the Technology 5600.0

4.8 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

High cost of hiring or operating earthmoving machinery

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:

A single summer rainfall period over approximately four months per year

Indicate the name of the reference meteorological station considered:

Otjiwarongo

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.
Indicate if the Technology is specifically applied in:
  • not relevant
Comments and further specifications on topography:

Scattered rocky outcrops

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)
Soil texture (> 20 cm below surface):
  • coarse/ light (sandy)
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.

A calcrete layer is occasionally exposed at the soil surfacce

5.4 Water availability and quality

Ground water table:

5-50 m

Availability of surface water:

poor/ none

Water quality (untreated):

poor drinking water (treatment required)

Is water salinity a problem?

Ja

Specify:

The water is only slightly brackish

Is flooding of the area occurring?

Geen

5.5 Biodiversity

Species diversity:
  • medium
Habitat diversity:
  • medium

5.6 Characteristics of land users applying the Technology

Sedentary or nomadic:
  • Sedentary
Market orientation of production system:
  • commercial/ market
Off-farm income:
  • 10-50% of all income
Relative level of wealth:
  • average
Individuals or groups:
  • individual/ household
Level of mechanization:
  • manual work
  • mechanized/ motorized
Gender:
  • women
  • men
Age of land users:
  • middle-aged

5.7 Average area of land owned or leased 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)?
  • large-scale

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

Land ownership:
  • individual, titled
Land use rights:
  • individual
Water use rights:
  • 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

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

fodder production

decreased
increased
Comments/ specify:

Mainly Moringa oleifera

fodder quality

decreased
increased
Comments/ specify:

Moringa leaves

animal production

decreased
increased
Comments/ specify:

Moringa heavily browsed

non-wood forest production

decreased
increased
Comments/ specify:

Still saplings

product diversity

decreased
increased
Comments/ specify:

Moringa leaves and fruits of other species could be harvested

Water availability and quality

water availability for livestock

decreased
increased
Comments/ specify:

Livestock need less water after feeding on lush forage

Income and costs

expenses on agricultural inputs

increased
decreased
Comments/ specify:

High initial cost of earthmoving

diversity of income sources

decreased
increased
Comments/ specify:

Potential from Moringa

workload

increased
decreased
Comments/ specify:

To water saplings

Socio-cultural impacts

food security/ self-sufficiency

reduced
improved
Comments/ specify:

Nutritious Moringa leaves may be added to diets

health situation

worsened
improved
Comments/ specify:

If nutritious Moringa leaves are eaten

SLM/ land degradation knowledge

reduced
improved
Comments/ specify:

Learning from action research

Ecological impacts

Water cycle/ runoff

surface runoff

increased
decreased
Comments/ specify:

Slowed, spread and infiltrated by ditches and ponds

groundwater table/ aquifer

lowered
recharge
Comments/ specify:

From improved infiltration

Soil

soil moisture

decreased
increased
Comments/ specify:

Near ditches and banks

soil cover

reduced
improved
Comments/ specify:

In ditches and ponds

nutrient cycling/ recharge

decreased
increased
Comments/ specify:

Below ditches and ponds

soil organic matter/ below ground C

decreased
increased
Comments/ specify:

Through tree and grass roots

Biodiversity: vegetation, animals

Vegetation cover

decreased
increased
Comments/ specify:

In ditches and ponds

biomass/ above ground C

decreased
increased
Comments/ specify:

In ditches and ponds

plant diversity

decreased
increased
Comments/ specify:

In ditches and ponds

habitat diversity

decreased
increased
Comments/ specify:

Along ditches and ponds

Climate and disaster risk reduction

drought impacts

increased
decreased
Comments/ specify:

Along ditches and ponds

fire risk

increased
decreased
Comments/ specify:

Along ditches and ponds, due to increased grass

6.2 Off-site impacts the Technology has shown

downstream flooding

increased
reduced
Comments/ specify:

Through improved infiltration on the farm

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?
other gradual climate change Increased variability in temperature and rainfall increase well

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
local thunderstorm well
Climatological disasters
How does the Technology cope with it?
heatwave well
cold wave well
drought well
land fire moderately
Hydrological disasters
How does the Technology cope with it?
flash flood well
Biological disasters
How does the Technology cope with it?
insect/ worm infestation well

Other climate-related consequences

Other climate-related consequences
How does the Technology cope with it?
reduced growing period well

6.4 Cost-benefit analysis

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

negative

Long-term returns:

positive

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

slightly negative

Long-term returns:

positive

6.5 Adoption of the Technology

  • single cases/ experimental
Of all those who have adopted the Technology, how many have did so spontaneously, i.e. without receiving any material incentives/ payments?
  • 0-10%

6.6 Adaptation

Has the Technology been modified recently to adapt to changing conditions?

Ja

If yes, indicate to which changing conditions it was adapted:
  • climatic change/ extremes
Specify adaptation of the Technology (design, material/ species, etc.):

After noticing death of tree seedlings from extreme drought, the decision was taken to irrigate them until sufficiently well established to care for themselves.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Avoids wastage of rainwater lost as runoff from the farm and puts it to good use on the farm.
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Improved water and nutrient cycling, resulting in better plant growth and higher animal production.
Reduced erosion of soil

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?
Death of many tree seedlings By irrigating tree seedlings until they are sufficiently well established to care for themselves, which may take one or two years.
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
High cost of earthmoving Growing of high value plants to recoup costs as quickly as possible, such as Moringa and dates.

7. References and links

7.1 Methods/ sources of information

  • field visits, field surveys
  • interviews with land users

7.2 References to available publications

Title, author, year, ISBN:

Rainwater harvesting for drylands and beyond: Vol 2 – Water-harvesting earthworks, Lancaster, 0-977-246418

Available from where? Costs?

https://www.amazon.com/Rainwater-Harvesting-Drylands-Beyond-Vol/dp/0977246418 $28

7.3 Links to relevant information which is available online

Title/ description:

Planning and managing farm roads Manual

URL:

www.sasscal.org/downloads/Planning_and_managing_farm_roads_in_Namibia.pdf

Title/ description:

Rangeland Rehydration Field Guide

URL:

https://emulandrecovery.org.au/~emulandr/files/Rangeland-Rehydration-Field-Guide.pdf

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