Technologies

Infiltration ditches and ponding banks [Namibia]

Ovala

technologies_2989 - Namibia

Completeness: 92%

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

Farm Middelplaats

Namibia

SLM specialist:
SLM specialist:

Pringle Hugh

Ecosystem Management Understanding

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

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

Yes

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?

No

1.5 Reference to Questionnaire(s) on SLM Approaches (documented using WOCAT)

2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Construction of contour ditches and ponding banks/ bunds to trap rainwater for infiltration. Improved growth of plants and replenishment of groundwater is promoted, while safely discharging excess water to avoid erosion. Integrated with other technologies that treat the root causes of rangeland degradation - rather than a stand-alone technology.

2.2 Detailed description of the Technology

Description:

The technology can be applied in rangeland: (a) where rainfall runoff occurs, (b) where the soil is deep enough to dig contour ditches and construct ponding banks, (c) where there is a low slope over a wide enough area for safe discharge of overflow during intense rain, (d) where valuable plants can benefit from the extra infiltrated rainwater, (e) where the costs of earthmoving can be rapidly recovered through sale of extra production and, very importantly, (f) where the root causes of rangeland degradation have been addressed, usually through management of grazing and fires.
In the appropriate area, contour lines are marked out by laser or dumpy level - or mapped by drone. Where bush is dense, it may be necessary to clear narrow contour strips, leaving larger trees in place. Ditches are dug up to 50cm deep by mechanised grader or backhoe (a digger attached to a tractor), or manually by pick and spade. The soil should first ideally be ripped where the bund is formed, to ensure a firm foundation. To stabilise the bund, it should be compacted, and creeping (stoloniferous) herbaceous plants encouraged to colonise it. When ditches are full, water is discharged through spillways within the bund. These spillways are formed by lowering the bund to about half its height (i.e. 25 cm) for a distance of 10 metres. Water overtops the spillways and flows across the soil surface to the next bund in the sequence. Spillways are set near alternating ends of shorter ditches for water to zigzag its way down through the landscape, but along longer ditches the spillways are set approximately 200 metres apart. There are other configurations, including one where excess runoff flows around the end of the bund and along another channel constructed immediately below the bund. It can then spill out of this channel, evenly over the soil surface below. Where bunds meet roads or tracks, a hump is made in the road to prevent water crossing and causing damage but instead channelling the road runoff into contour ditches.
Since the channel is never exactly on the contour, water starts to flow over the lowest section. This results in self-reinforcement over time because herbaceous plants establish more densely at that point, resulting in more sediment being trapped there. To avoid spillage around each end of the ditch, the bund is shaped to form a short upslope wingwall. Organic material can be placed in the ditch, or in larger sediment traps within the ditch, to improve nutrient cycling.
Infiltration ditches were constructed at vertical intervals of 0.5 m on a 30 ha, densely bushed portion of the Middleplaats farm. Trees were planted below the ditches to grow into a “fruitful landscape”. Species included broad 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 fruit bearing trees, such as Sclerocarya birrea and Berchemia discolor, or trees with edible leaves, such as Moringa oleifera. Tree seedlings were raised in a nursery. Fencing around the 30ha had to be strengthened to protect the seedlings from oryx. It was also necessary to water the seedlings for one to two years until well established. Ponded water encourages natural growth of herbaceous plants, and to encourage this some grasses were transplanted there.

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

Specify the spread of the Technology:
  • evenly spread over an area
If precise area is not known, indicate approximate area covered:
  • 0.1-1 km2

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:
  • Ranching
Animal type:
  • cattle - non-dairy beef
Comments:

Main animal species and products: Beef cattle and game animals

Number of growing seasons per year: 1
Livestock density: 10ha/LSU averaged out over time and not continuous

3.4 Water supply

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

3.5 SLM group to which the Technology belongs

  • agroforestry
  • pastoralism and grazing land management
  • water harvesting

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

Technical specifications (related to technical drawing):

Contour strips were cleared by bulldozer at 0.5m vertical intervals on land with a gradient of approximately 1.0%. A line was ripped approximately 0.6m deep, over which soil was heaped to form a bund by a grader while excavating a ditch on its upper side to hold rainwater at a depth of approximately 0.5m. Spillways were created by lowering a 10m length of the bund. Spillways were staggered between ditches to zig-zag the spilled water slowly through the landscape. A variety of tree seedlings were planted alongside the structures to make use of the extra water, providing tall canopies, “chop-and-drop” mulching, and edible leaves or fruits.

Author:

Ibo Zimmermann

Date:

21/07/2017

4.2 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

4.3 Establishment activities

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

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 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
Total costs for establishment of the Technology in USD 177092.0

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. Maintenance of ditches and bunds by grader Rainy season

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
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
Total costs for maintenance of the Technology in USD 5600.0

4.7 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?

Yes

Specify:

The water is only slightly brackish

Is flooding of the area occurring?

No

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 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)?
  • 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 increase or decrease 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 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?

Yes

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

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

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 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
When were the data compiled (in the field)?

2017

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 online information

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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