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 program

Half-Moon Technology: A Strategic Framework for Development Partners

The Half-Moon Technology offers a transformative approach to land restoration and climate-resilient agriculture in dryland areas. This framework guides development partners in scaling up the use of half-moon pits for soil fertility enhancement, water conservation, and increased agricultural productivity. By integrating financial, institutional, capacity-building, and technical components, the framework ensures that half-moon interventions are sustainable, inclusive, and community-driven, while addressing key challenges faced by vulnerable farming communities.

Steps for Effective Half-Moon Implementation for Development Partners

Define the Vision and Strategic Objectives
Develop a Financial and Resource Mobilization Strategy
Assess Capacity and Technical Needs
Conduct a Needs Assessment and Contextual Analysis
Implement Monitoring and Data Collection Systems
Integrate Half-Moon Interventions into Broader Development Policies
Monitor, Evaluate, and Scale

Real Impact Assessment Data

Recent studies from J-PAL and CGIAR's Standing Panel on Impact Assessment (SPIA) provide robust evidence of the effectiveness of half-moon (demi-lune) water harvesting pits in improving agricultural productivity, water use efficiency, soil health, and land restoration in the Sahel:

Increased Yields: Millet yields rose by 300–400% in Niger and Burkina Faso using half-moons compared to flat planting (ICRISAT; SPIA 2023).
Improved Water Efficiency: Half-moons doubled water retention, reducing water stress for crops by 2–3 weeks (SPIA; J-PAL 2022).
Land Restoration: Farmers reclaimed 0.3 additional hectares on average and were 33% less likely to abandon land (J-PAL, 2022).
Higher Income: Annual household income increased by USD 34–37 due to improved yields (J-PAL, 2022).
Soil Fertility Gains: When combined with organic matter (e.g., manure, crop residues), nutrient uptake increased significantly.

Evaluation Design (Aker & Jack, 2021)

Study conducted in 180 randomly selected villages in Niger, involving 2,861 participants, with equal gender representation.
Participants were randomly assigned to 5 groups: training only, early unconditional cash transfer (UCT), conditional cash transfer (CCT), late UCT, and a control group.
CCTs (USD 0.40 per half-moon) and training significantly increased adoption.
Researchers also monitored spillover effects among 670 uninvolved neighbors, many of whom also adopted the technique.

References

Aker, J. C., & Jack, K. (2021). Harvesting the Rain: The Adoption of Environmental Technologies in the Sahel (No. w29518). National Bureau of Economic Research.
https://doi.org/10.3386/w29518
Aker, J. C., Jack, K., & Wichman, C. (2022). Demi-Lunes for Resilience: Evidence from Niger. J-PAL, Abdul Latif Jameel Poverty Action Lab.
https://www.povertyactionlab.org/evaluation/demi-lunes-resilience-evidence-niger
CGIAR Standing Panel on Impact Assessment (SPIA). (2023). Evidence for the Impact of CGIAR Research: Niger Country Study.
https://cas.cgiar.org/spia/publications/evidence-impact-cgiar-research-niger
ICRISAT. (2020). Harnessing the potential of water harvesting techniques in the Sahel: The case of demi-lunes in Burkina Faso and Niger. International Crops Research Institute for the Semi-Arid Tropics.
https://www.icrisat.org

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