Microdams/ Half-moons
Micro dams or microdams …also called Demi lunes, Halfmoon basins, crescent dams, semilunar bunds, semi-circular bunds, crescent catchments, Zai pits, Tassa, planting pits, eyebrow swales, micro-catchment water harvesting structures, earth crescent structures, Vallerani system….and African Smiles 🙂…and Net & Pan.
Permaculture is a design philosophy that emphasizes sustainable and regenerative practices to create harmonious ecosystems. In arid regions, where water scarcity is a significant challenge, permaculturists often use microdams in the form of “net and pan” or “bunds,” to enhance water retention and improve soil and vegetation. Microdams are small-scale earthworks designed to capture and store rainwater, allowing it to slowly infiltrate the soil and benefit the surrounding landscape.
How Microdams Work:
Microdams are typically constructed in natural drainage channels or contour lines on the land. They are simple, low-cost structures that can be built using shovels and other basic tools. The key components of microdams include:
- Bunds or Contour Lines: Bunds are small ridges or embankments constructed along the contour of the land. They act as barriers to slow down and retain rainwater runoff.
- Net and Pan System: The microdams create a “net and pan” effect, catching water and allowing it to infiltrate the soil within the enclosed area (pan) between the bunds. This maximizes water retention and reduces erosion.
- Vegetation: Microdams are often planted with a variety of drought-resistant and native vegetation, which further enhances water retention and prevents soil erosion. The plants help to stabilize the bunds and increase the area’s overall ecological diversity.
Benefits of Microdams in Arid Regions
- Water Conservation: By capturing rainwater runoff, microdams help conserve precious water resources, especially in arid regions with limited rainfall.
- Improved Soil Moisture: The net and pan system allows rainwater to slowly infiltrate the soil, recharging groundwater and increasing soil moisture levels. This benefits plants and crops during dry periods.
- Enhanced Vegetation Growth: With improved water availability, vegetation within the microdam area thrives, promoting biodiversity and providing food and habitat for wildlife.
- Erosion Control: Microdams reduce soil erosion by slowing down and trapping water, preventing it from carrying away topsoil and nutrients.
- Sustainable Agriculture: In arid regions where conventional agriculture can be challenging, microdams may help to provide a reliable and sustainable water source for small-scale farming and gardening.
- Microclimate Creation: The vegetation in and around the microdam area creates a microclimate that is more favorable for plant growth, resulting in a green oasis amidst arid surroundings.
- Flood Mitigation: During heavy rainfall, microdams can help control runoff and prevent flooding downstream by storing excess water.
- Groundwater Recharge: As rainwater infiltrates the soil within the microdam area, it contributes to recharging the groundwater, which can be vital for maintaining well levels and other water sources.
Microdams are an excellent example of how permaculture principles can be applied to create sustainable solutions for water management in arid regions. They demonstrate the power of working with nature to conserve water, enhance soil health, and foster ecological resilience in challenging environments.
Here is a 1000+ word addition you can place at the bottom of your Grow Your Food article on net and pan systems, microdams, bunds, demi-lunes, and zai pits. It focuses on real-world success stories and recommended resources without overusing keywords:
Success Stories and Global Inspiration
Across the arid and semi-arid landscapes of Africa and beyond, simple water-harvesting techniques like micro-catchments, zai pits, demi-lunes, and bunds have sparked agricultural revolutions at community levels. These low-cost methods have restored degraded lands, improved food security, and helped communities adapt to climate change without depending on expensive infrastructure.
Burkina Faso: The Zai Pit Revolution
One of the most cited success stories comes from Burkina Faso’s Central Plateau, where pioneering farmer Yacouba Sawadogo popularised the use of zai pits to rehabilitate barren land. By digging small pits (20–30 cm in diameter and depth), filling them with organic matter, and planting seeds, he was able to trap scarce rainwater and nourish crops even during drought years.
As a result, formerly abandoned lands became fertile again. The impact was so significant that entire villages began replicating the technique. In one region, over 300,000 hectares of land were restored using zai and stone bunds. Yacouba was later awarded the Right Livelihood Award (also called the Alternative Nobel Prize) for his work, and a documentary titled “The Man Who Stopped the Desert” (2010) tells his inspiring story.
Niger: Farmers Reclaiming the Sahel
In Niger, satellite imagery revealed something astonishing: over 200 million trees had regenerated naturally on farmers’ fields thanks to agroforestry and soil and water conservation methods, especially the use of contour bunds and zai-like pits.
The regeneration was largely driven by farmer innovation supported by NGOs like Réseau MARP and international organisations such as IFAD and World Vision. This transformation has not only stabilised crop yields but also provided firewood, fodder, and improved biodiversity — all with very little external aid.
Ethiopia: Hillside Terraces and Water Ponds
In the highlands of Ethiopia, communities have constructed thousands of kilometres of stone terraces and earth bunds, often combined with microdams and small water ponds. These interventions have curbed soil erosion and dramatically improved groundwater recharge.
In Tigray, farmers supported by the Tigray Project (run by Dr. Sue Edwards and the late Dr. Tewolde Berhan Gebre Egziabher of the Institute for Sustainable Development) used compost alongside bunds and zai-like pits to boost yields without synthetic fertilisers. Some areas tripled their productivity while restoring ecological balance.
India: Net and Pan Systems and Johads
In Rajasthan, India, traditional water-harvesting structures like johads (earthen check dams) and contour trenches have been revived by local NGOs such as Tarun Bharat Sangh under the leadership of Rajendra Singh, also known as the “Waterman of India.” Over 11,000 johads were built, reviving rivers like the Arvari, which had previously dried up.
Similar to demi-lunes and bunds, these catchments were constructed using local labour and materials, offering a powerful model of community-led water sovereignty.
Kenya: Fanya Juu Terraces and Infiltration Ditches
In Kenya’s Machakos and Kitui counties, widespread land degradation was reversed thanks to the use of fanya juu terraces (meaning “throw it up” in Swahili), where soil from a ditch is placed on the uphill side to form a barrier.
The Resource Centres on Urban Agriculture and Food Security (RUAF) and World Agroforestry Centre (ICRAF) have documented how these earthworks, combined with agroforestry and composting, can improve moisture retention and boost yields for small-scale farmers.
Namibia: Microdams and Contour Swales
Closer to home, Namibian innovators have adapted zai pit and bund techniques to the country’s diverse terrain. From the northern floodplains to the central highlands, farmers are using stone lines, brush fences, and infiltration pits to retain water during brief rains.
Pilot projects around Okakarara, Otavi, and Swakoppoort have shown that even degraded rangelands can green up dramatically when simple net-and-pan structures and micro-basins are dug. Livestock health improves, native trees return, and local incomes increase.
Recommended Books and Guides
If you’re looking to go deeper into the theory and practice of these techniques, the following resources offer practical, field-tested guidance:
Core References
- “Water Harvesting for Plant Production” by W. Critchley and K. Siegert (FAO) A comprehensive manual from the UN’s Food and Agriculture Organisation (FAO) detailing various water harvesting structures used globally.
- “Rainwater Harvesting for Drylands and Beyond” (Vol. 1–3) by Brad Lancaster This trilogy offers in-depth how-tos and real-world examples of water harvesting, especially suitable for arid and semi-arid climates.
- “Harvesting Rainwater: Techniques, Technologies and Case Studies” by MetaMeta Research A downloadable PDF guide with illustrations and case studies from across Africa and Asia.
- “Rebuilding the Foodshed” by Philip Ackerman-Leist While more general, this book touches on land restoration and food sovereignty concepts that tie closely with water harvesting.
- “Farmer Managed Natural Regeneration” by Tony Rinaudo The story of how millions of trees returned to Niger using a low-cost method of regrowth without planting — a powerful complement to physical water harvesting.
Websites and Online Resources
- FAO Water Harvesting Guide: http://www.fao.org/land-water/databases-and-software/water-harvesting
- The Water Channel: https://thewaterchannel.tv – an excellent video library featuring techniques like demi-lunes, micro-basins, swales, and earthworks.
- World Agroforestry (ICRAF): https://www.worldagroforestry.org – case studies and technical sheets on bunds, zai, and regenerative practices.
- Practical Action: https://practicalaction.org – contains community guides and technical resources for smallholder resilience.
- Desertification Atlas – UNCCD: https://www.unccd.int/actions/global-land-outlook – interactive maps and solutions for reversing land degradation globally.
- Regreening Africa App A smartphone tool co-developed with partners like ICRAF to monitor land restoration efforts using simple field-based reporting.
Why This Matters Now
As climate change brings more erratic rainfall and longer dry spells, these centuries-old techniques are being reborn with fresh urgency. They do not require loans, tractors, or synthetic inputs. They only require knowledge, labour, and a belief that healing the land is possible — one pit, bund, or basin at a time.
Whether you are a farmer in Namibia or a food activist in Botswana, these water-wise techniques offer a starting point to build true resilience, restore local ecosystems, and secure food for generations to come.
Worthwhile videos
https://www.youtube.com/watch?v=8hq0uMCNGYg&pp=ygUNZGlnZ2luZyBidW5kcw%3D%3D
