Demi-lune technology: Rainwater harvesting method

Catch the Rain, Grow with the Grain!

The Demi-lune (Half-moon) technology is a simple and effective rainwater harvesting method used in dry regions to improve crop growth and restore degraded land. It involves digging semi-circular pits (like a half-moon shape) that catch and hold rainwater. Each demi-lune usually has a diameter of 2 to 3 meters and a depth of 15 to 30 centimeters. The open side of the pit faces uphill, so when it rains, water runs into the pit and is trapped there.
Farmers place stones around the curve to keep the shape strong and prevent it from washing away. About 35 kg of compost or organic fertilizer is added inside to enrich the soil. The water and nutrients collected in the pit help crops grow well even in harsh, dry conditions.
This technique reduces soil erosion, improves soil fertility, and boosts crop yields, making unproductive land useful again.

This technology is TAAT1 validated.

9•9

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

Adults 18 and over: Positive high

It can offer significant advantages in terms of reducing water and fertilizer dependency, which can make farming easier in the long term.

The poor: Positive low

It can enhance food security, productivity, and climate resilience for poor communities. However, challenges like labor demands, limited resources, and knowledge gaps must be tackled. With adequate support and training, it offers a powerful tool to improve livelihoods.

Under 18: No impact

Youth may struggle to adopt the technology due to limited resources, knowledge, and capital, especially where extension services are weak.

Women: Positive medium

The technology boosts food production and water collection, reduces labor, and frees women’s time for other activities or education.

Climate adaptability: Moderately adaptable

It is a versatile, low-cost solution for improving crop productivity and resilience in a variety of climates, but its implementation must consider local environmental conditions to maximize its benefits.

Farmer climate change readiness: Moderate improvement

It strengthens farmers' ability to adapt to changing climates, recover from climate shocks, and maintain productivity in the face of increasing environmental stresses. It is particularly effective in semiarid and arid regions, where climate impacts are most severe.

Biodiversity: Positive impact on biodiversity

It contributes to healthier plants, more sustainable livestock systems, and the restoration of natural ecosystems, making it a valuable tool for climate-smart, biodiversity-friendly agriculture.

Carbon footprint: Much less carbon released

It contributes to net carbon sequestration over time, making it a climate-friendly solution that performs much better in terms of carbon balance than conventional, non-restorative practices.

Environmental health: Greatly improves environmental health

It turns degraded, unproductive lands into healthy ecosystems, restoring soil, water, and biodiversity, and contributing to long-term environmental resilience and sustainability.

Soil quality: Improves soil health and fertility

It rejuvenates degraded soils, increasing their fertility, moisture retention, and biological activity, leading to more productive and sustainable agricultural land.

Water use: Much less water used

It maximizes the use of available rainfall, allowing farmers to sustain crops with much less water than traditional practices, which is critical in drought-prone areas.

Problem

Water scarcity and irregular rainfall
In arid and semi-arid regions, rainfall is often scarce, erratic, and insufficient to sustain crop growth. This limits agricultural productivity and leads to frequent crop failures.
Soil degradation and erosion
Many dryland areas face severe soil degradation due to erosion, overgrazing, and deforestation. These factors strip the land of its fertility, making it difficult to cultivate crops or sustain vegetation.
Low agricultural productivity
Poor soil quality and lack of water retention result in low crop yields. Farmers struggle to produce enough food, which directly impacts food security and economic stability.
Lack of irrigation infrastructure
Remote and resource-limited communities often lack access to irrigation systems. Installing and maintaining such systems can be costly and technically challenging, leaving farmers dependent solely on unpredictable rainfall.
Nutrient-poor soils
Soils in degraded lands typically lack essential nutrients needed for healthy plant growth. This deficiency hampers crop development and increases the need for external fertilizers, which may not be affordable for smallholder farmers.
Biodiversity loss
Land degradation leads to a decline in plant and animal biodiversity. The loss of native vegetation and habitats diminishes ecosystem resilience and reduces the availability of resources for communities and wildlife.
Vulnerable livelihoods in drylands
Communities in drylands face persistent challenges in securing reliable sources of food, fodder, and income. Environmental stresses and lack of agricultural options make their livelihoods highly vulnerable to shocks.
Overdependence on chemical fertilizers
Farmers often rely on chemical fertilizers to compensate for poor soil fertility. This dependence can be costly, environmentally damaging, and unsustainable in the long term.

Solution

Improved water harvesting and retention
By capturing and storing rainwater in semi-circular pits, the technology maximizes water availability for crops even in dry spells. This helps mitigate the effects of water scarcity and irregular rainfall.
Soil restoration and erosion control
The pits slow down water runoff and trap sediments, preventing further soil erosion. Over time, the technique restores soil structure and fertility, rehabilitating degraded lands.
Enhanced agricultural productivity
By concentrating water and nutrients around plant roots, the half-moons create favorable conditions for crops to thrive. This leads to higher yields and more resilient farming systems.
Low-cost alternative to irrigation
Half-moons provide a simple, affordable method of rainwater harvesting that does not require expensive infrastructure. They are accessible to smallholder farmers and can be implemented using local materials and labor.
Enrichment of soil nutrients
Adding organic fertilizers or compost to the pits boosts soil fertility naturally. As a result, farmers reduce their reliance on chemical fertilizers, improving soil health and reducing costs.
Support for biodiversity
By restoring vegetation cover, half-moons create habitats that attract insects, wildlife, and beneficial microorganisms. This promotes greater biodiversity and ecosystem resilience.
Strengthened livelihoods and food security
The technology improves the reliability of agricultural production, providing farmers with more consistent food and income sources. This strengthens local livelihoods and reduces vulnerability to climate shocks.
Sustainable farming practices
The method encourages the use of natural materials and traditional knowledge, promoting sustainable and environmentally friendly agricultural practices.

Key points to design your project

Key Points to Design Your Project: Half-Moon Implementation Framework

The Half-Moon Implementation framework provides structured guidance for designing and scaling up the use of half-moon pits (demi-lunes) for land restoration and climate-resilient agriculture. It ensures a holistic approach by integrating financial, institutional, capacity-building, and technical aspects, making half-moon interventions sustainable, community-driven, and impactful. This framework helps governments, development organizations, and farming communities effectively adopt and expand the use of half-moons to enhance soil fertility, water harvesting, and agricultural productivity in dryland regions.

Steps for Effective Half-Moon Implementation

Define the Vision and Objectives

Set clear goals for half-moon adoption, aligned with national priorities such as land rehabilitation, food security, climate adaptation, and sustainable dryland farming.
Engage local communities to ensure ownership and long-term success.

Develop a Financial Sustainability Plan

Mobilize resources through government schemes, NGOs, and climate resilience funds.
Encourage cost-effective scaling by promoting farmer-to-farmer learning and cooperative models.

Assess Capacity and Technical Needs

Identify gaps in skills, training, and resources required for efficient half-moon construction and upkeep.
Provide practical training to farmers, extension agents, and local institutions for widespread adoption.

Conduct a Needs Assessment

Work with farmers, soil scientists, and local authorities to identify key challenges and anticipated outcomes.
Adapt half-moon designs to local contexts, considering soil type, rainfall, and crops.

Implement Data Collection and Governance Strategies

Set up monitoring systems to track crop yields, soil improvement, and water retention.
Integrate half-moon projects into broader land management strategies and national climate action plans.

Monitor and Evaluate Impact

Regularly evaluate the effectiveness of half-moon interventions using yield data, soil health metrics, and farmer feedback.
Refine approaches in response to climatic shifts, adoption patterns, and environmental outcomes.

By following this framework, decision-makers can establish resilient, scalable dryland farming solutions that promote soil restoration, improve food security, and strengthen climate resilience across vulnerable regions.

IP

Unknown

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
Morocco	–No ongoing testing	Tested	Adopted
Niger	–No ongoing testing	Tested	Adopted
Sudan	–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 1: no poverty

It helps increase income for smallholder farmers, contributing to poverty reduction.

Goal 2: zero hunger

It improves crop growth in areas with water scarcity, directly enhancing food security and agricultural resilience.

Goal 6: clean water and sanitation

The water harvesting aspect of the technology ensures better water retention, improving access to water for crops and livestock.

Goal 12: responsible production and consumption

The use of organic fertilizers and the reduction in the need for chemical inputs aligns with sustainable farming practices, contributing to responsible land and resource management.

Goal 13: climate action

By restoring degraded lands and improving water retention, this technology contributes to climate resilience, helping to combat soil erosion and reducing the impact of extreme weather events.

Goal 15: life on land

The technology supports land restoration, enhances biodiversity, and improves soil fertility, leading to healthier ecosystems.

Site Selection

Choose degraded or low-productivity land where water runoff is noticeable.
Preferably select gentle slopes (up to 5–15%) in arid or semi-arid areas.
Avoid areas with heavy rainfall to prevent waterlogging.

Marking the Pits

Mark out semi-circular shapes on the ground with the mouth of each half-moon facing uphill (toward the water flow).
Each half-moon should have a diameter of 2–3 meters.
Keep spacing in staggered rows so water can flow from one row to the next.

Digging the Pits

Excavate the pits to a depth of 15–30 cm.
Collect the excavated soil and pile it along the curved edge to build a small bund (mini-embankment).

Reinforcing the Structure

Line the curved bund with stones to prevent erosion and washout during rains.
Ensure the pit remains open and deep enough to trap water.

Adding Fertilizer/Compost

Apply around 35 kg of organic fertilizer or compost evenly inside each pit.
This boosts soil fertility and prepares the pit for planting.

Planting Crops or Trees

Plant seeds or seedlings inside the pit after the first rain or once moisture is available.
Suitable crops include millet, sorghum, legumes, trees, and fodder species.

Maintenance

Regularly check the pits, especially after heavy rains, to repair any damage to the bunds or stones.
Replenish organic material as needed to maintain soil fertility.

Additional Tips:

For larger-scale land restoration, combine half-moons with other rainwater harvesting techniques like Zai pits or contour bunds.
Engage community members for collective work, as the method is labor-intensive but highly rewarding.

Last updated on 13 May 2025