Contour Bunding Technique (CBT): Contour Bunds for Water Harvesting

CBT: Nurturing Crops, Conserving Soil, and Cultivating Resilience

The “Contour Bunding Technique (CBT)” is a farming method that helps deal with the problems of not having enough water and soil being washed away in dry farming, especially in Africa’s dry areas. This method uses a series of small walls, built in certain patterns along the curves of the fields. These walls make small areas that collect water. They stop water from running off, help catch more rain, store more water, and let water sink deep into the ground. By reducing water running off the surface and stopping soil from being washed away and ditches from forming, CBT greatly improves the soil’s ability to hold water. This is a simple but professional way to explain the concept.

This technology is TAAT1 validated.

8•7

Scaling readiness: idea maturity 8/9; level of use 7/9

Cost: $$$ 9 USD

Drawing contour line per ha

40 %

Runoff reduction

20 %

Sediment loss dicrease

IP

Open source / open access

Problem

Water Scarcity: In dryland farming, there is often a shortage of water due to irregular and insufficient rainfall. This makes it difficult to grow crops and sustain agriculture.
Soil Erosion: In dry areas, the soil is easily washed away by wind and water. This leads to the formation of gullies and the loss of fertile topsoil, which negatively impacts the health and productivity of the soil.

Solution

Strategic Wall Placement: The small walls, or bunds, are built along the natural curves of the fields. This design helps to trap runoff water that would otherwise be lost.
Creation of Micro-Catchments: These bunds create small water collection areas, or micro-catchments, that help to capture and store more rainwater.
Deep Water Infiltration: By trapping the water, the technique allows for deep water infiltration into the soil, enhancing the soil’s water retention capacity.
Soil Erosion Prevention: The bunds also help to prevent soil erosion and gully formation by reducing the speed and volume of surface runoff.

Key points to design your business plan

For Farmers

For a farmer who wants to use the Contour Bunding Technique (CBT) in their farm, here are the steps:

Understand the Benefits: Learn about the advantages of CBT, such as improved crop production, soil fertility, and watershed management.
Get Trained: Attend training sessions on how to use land surveying equipment and methods for constructing cost-effective bunds.
Analyze Your Farm: Understand the water movement across your farm landscape to determine the best placement of bund structures.
Gather Resources: Ensure you have access to necessary resources such as animal-drawn or motorized ploughs, low-cost stone resources, and seedlings of fast-growing trees for building and reinforcing bunds.
Implement CBT: Start constructing the bunds along the contour lines of your farm. Remember, the bunds should be arranged in specific patterns to create micro-catchments that can intercept runoff, increase rainfall capture, and promote water storage and deep infiltration.
Monitor and Adjust: After implementation, monitor the effects of CBT on your farm, such as changes in crop yields, soil health, and water management. Use this information for continuous improvement.

Adults 18 and over: Positive high

The poor: Positive high

Under 18: Positive low

Women: Positive high

Climate adaptability: Highly adaptable

Farmer climate change readiness: Significant improvement

Biodiversity: Positive impact on biodiversity

Carbon footprint: Much less carbon released

Environmental health: Greatly improves environmental health

Soil quality: Improves soil health and fertility

Water use: Much less water used

Countries with a green colour: Tested & adopted
Countries with a bright green colour: Adopted
Countries with a yellow colour: Tested
Countries with a blue colour: Testing ongoing

Countries where the technology is being tested or has been tested and adopted
Country	Testing ongoing	Tested	Adopted
Burkina Faso	–No ongoing testing	Tested	Adopted
Chad	–No ongoing testing	Tested	Adopted
Ethiopia	–No ongoing testing	Tested	Adopted
Kenya	–No ongoing testing	Tested	Adopted
Mali	–No ongoing testing	Tested	Adopted
Niger	–No ongoing testing	Tested	Adopted
Nigeria	–No ongoing testing	Tested	Adopted
Senegal	–No ongoing testing	Tested	Adopted
Sudan	–No ongoing testing	Tested	Adopted
Tanzania	–No ongoing testing	Tested	Adopted
Zimbabwe	–No ongoing testing	Tested	Adopted

This technology can be used in the colored agro-ecological zones. Any zones shown in white are not suitable for this technology.

Agro-ecological zones where this technology can be used
AEZ	Subtropic - warm	Subtropic - cool	Tropic - warm	Tropic - cool
Arid
Semiarid		–		–
Subhumid	–	–	–	–
Humid	–	–	–	–

Source: HarvestChoice/IFPRI 2009

The United Nations Sustainable Development Goals that are applicable to this technology.

Goal 2: zero hunger

Goal 13: climate action

The first step involves a collaborative field visit by farmers and a technician to assess slope direction, water movement, local practices, community regulations, and neighbor relationships, preventing unwanted water drainage and fostering cooperation.
The second step is to identify contour lines using land surveying tools and mark them temporarily.
Bunds are constructed either manually or with an ox-drawn plough, typically requiring three to four plow passes to create a sufficiently tall bund (e.g., 50-80 cm).
The standard distance between bunds is 50 meters on slopes less than 1.6%, and it ranges from 20 to 30 meters when the slope is between 1.6% and 5%.
Fast-growing tree seedlings are planted at 3-meter intervals on the crest of the bunds to reinforce them and enhance their stability.
Soil bunds require regular maintenance and strengthening using a plough or hand hoe to ensure their effectiveness.