Practice
Swale
Also known as: On-contour swale, Bioswale
A shallow ditch dug along a topographic contour line, with the excavated earth piled on the downhill side as a berm. Swales slow, spread, and sink rainfall into the landscape rather than letting it run off. A foundational permaculture earthwork; widely used in dryland restoration (Geoff Lawton's Greening the Desert work in Jordan), in rain-garden urban stormwater management, and in commercial farms practicing keyline design. The swale-and-berm assembly transforms steep, runoff-prone landscapes into water-retaining, plant-supporting terraces.
How swales work
A swale is dug along the contour — same elevation across its length. When rain falls upslope:
- Water flows downhill toward the swale
- Hits the swale and stops in the ditch
- Slowly infiltrates into [[soil|the soil]] under and around the swale
- The downhill berm is planted with trees, shrubs, or perennials that benefit from the captured water
In a heavy rain event, water fills the swale to capacity, then overflows around the berm in a controlled spillway. The next swale downslope catches what gets past.
Why they work
In conventional landscapes, rain flows downhill, eroding soil and concentrating in waterways before it has a chance to infiltrate. Swales reverse this:
- Water moves slowly across the landscape rather than fast downhill
- Infiltration time increases dramatically
- Soil moisture stays high under and downslope of the swale
- Trees planted on the berm tap the slow-flowing groundwater
- Runoff and erosion are dramatically reduced
Famous example
Geoff Lawton’s Greening the Desert — Jordan dryland restoration project. Swales dug along contours, planted with date palms and pioneer trees on the berms. Within years, severely-degraded land became productive [[food-forest|food forest]] with measurably-recharged groundwater. The video documenting this work has been viewed millions of times and inspired similar projects worldwide.
Variations
- Off-contour swale — slight gradient (1-2%) for areas needing both infiltration and slow conveyance
- Bioswale — urban stormwater swale, often with engineered media and specific drainage; common in green-infrastructure design
- Boomerang swale / half-pipe swale — small individual swales around tree-pits in arid zones
- Keyline-pattern swales — full-watershed swale system following keyline geometry
See also
Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.
- Shares approach with: [[keyline-design]] · [[water-cycle]]
- Member of: [[practice]]
Sources
- Permaculture: A Designers’ Manual, [[bill-mollison|Bill Mollison]] (1988)
- [[rainwater-harvesting|Rainwater Harvesting]] for Drylands and Beyond, Brad Lancaster (multiple volumes)
- Geoff Lawton’s Greening the Desert documentation
Rooted in life.
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