The 8 Rainwater Harvesting Principles

Every site is unique and much be approached with its own distinctive characteristics in mind. These are eight principles to utilize in conjunction with the permaculture principles and ethics when designing a rainwater harvesting system.
  1. Begin with long and thoughtful observation
    • Sit quietly, listen with all of your senses
    • Connect, think, imagine, plan
    • Comprehend and copy nature
  2. Start at the top--or highpoint--of your watershed and work your way down
    • Top of a roof or top of a mountain, for instance
  3. Start small and simple
    • Human scale
    • Technically and mechanically simple
    • Multiple small earthworks are easier to create and capture more water than one big dam
  4. Spread and infiltrate the flow of water - slow it! spread it! sink it!
  5. Always plan for an overflow route and manage that overflow as a resource
    • The overflow should be wide and flat to avoid erosion
  6. Maximize living and organic ground cover - create a living sponge
    • Focus on perennials, shrubs, and deep rooted plants that can utilize and cover the saturated soil
  7. Maximize beneficial relationships and efficiency by stacking functions - do more than just harvest water
  8. Continually re-assess your system - feedback loop
    • Observe, repair, improve, practice balanced maintenance, follow all of the principles together, celebrate abundance!

Calculating Available Water from Roof Catchment

A (ft²) x R (ft) = W (ft³)

A: area of roof footprint in square feet
R: rainfall in feet
W: volume of water in cubic feet
Note that 1 ft³ = ~ 7.5 gallons

Rainwater Harvesting Containers

  • Rainwater tanks should be shaded, painted, or otherwise covered to avoid plastic breakdown - growing plants on them can serve a dual purpose of shading/covering and producing something aesthetic and possibly edible
  • If your roof is made of old asphalt shingles, the water captured from it should only be used for landscaping, not drinking
  • Rainwater captured from tile or steel roofs should be okay for drinking
  • You don't necessarily want the first rain of the season in your tank - anything that's accumulated on your roof since the prior rainy season will wash into your tank
    • Design your system with a valve to shut off rainwater flow to your tank when you want to avoid runoff from the roof going into the tank - direct the overflow from this to somewhere specific in the landscape that is designed to accommodate it
    • Be sure to include screens to prevent debris from going into the tank, and clean out gutters
  • Tanks can be made of cement or can be designed in different shapes, such as a long, narrow fence that can serve dual purpose as fence and water catchment

Resources

Visit our Library for a list of recommended books, videos, articles, and websites.