Swales & Berms (Earthworks) โ€” FarmPal

Contour swales capture rainwater runoff and infiltrate it into the soil, recharging groundwater and hydrating downhill plantings. The permaculture water harvesting workhorse.

Cost Range
$0 (hand-dug) to $500+ (machine-dug)
Water Yield
Depends on catchment area can capture thousands of gallons per storm

Key Points

  • ๐Ÿ’งSwales are level trenches on contour water sits and infiltrates, never flows
  • ๐Ÿ’งBerms (downhill mound from digging) are planted with productive trees/shrubs
  • ๐Ÿ’งMust be perfectly level (use A-frame or laser level)
  • ๐Ÿ’งTrees planted on berms access deep subsoil moisture stored by swales
  • ๐Ÿ’งMost effective on slopes of 2-15% grade

Installation Steps

  1. 1Map contour lines on your property using A-frame level or water level
  2. 2Mark swale locations perpendicular to slope, following contour exactly
  3. 3Dig trench 12-18 inches deep, 18-36 inches wide
  4. 4Pile excavated soil on downhill side (this is the berm)
  5. 5Check level constantly water must sit evenly along entire length
  6. 6Plant berm with deep-rooted perennials, fruit trees, nitrogen fixers
  7. 7Mulch swale bottom heavily to prevent erosion during overflow
  8. 8Add spillway at one end for overflow during extreme events

Practical Checklist

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Supplies

Safety Steps

Testing & Verification

Tips

  • ๐Ÿ’กGeoff Lawton's "Greening the Desert" project proves swales work even in arid climates
  • ๐Ÿ’กPlant nitrogen-fixing trees (black locust, autumn olive) on berms to build soil
  • ๐Ÿ’กSwales on contour paired with food forest plantings = self-irrigating orchards
  • ๐Ÿ’ก2025 research: swale systems increased soil moisture by 40% compared to untreated slopes
  • ๐Ÿ’กStart small one swale above your garden can dramatically reduce irrigation needs