Natural Swimming Pools:
Multifunctional Tools for a Permaculture Landscape?
In Bill Mollison’s Permaculture: A Designers’ Manual, he says something along the lines of, “While we’re not using Chlorine to make mustard gas and poison our drinking water, we fill our pools with it and have a great time swimming around. Why would I want to immerse myself in a liquid that no other living thing can survive in?”
Natural swimming pools provide a completely biological method to create clean, clear swimming pools. They can be designed and built on nearly any scale, from small backyard pools to huge public swimming areas. Used extensively in Europe (especially Germany), they have yet to really take off in the US. Today I attended a seminar by James Robyn of BioNova Natural Swimming Pools, who gave a 400-slide overview of the systems and offered some basic design principles and guidelines. My complete set of notes from the day is available for free download here: Natural_Swimming_Pool_notes.
Basically, Natural Swimming Pools (NSPs) are just like normal pools or ponds that pump water slowly through “Regeneration Zones” – which are simply Constructed Wetlands. Using a gravel substrate 3 feet deep, a diversity of locally-adapted aquatic plants (including submerged, emergent, and floating plants) are planted at a density of 2-5 plants per square foot. Water should flow through the pools at a rate of 26 gallons per square foot of per day. Costs for constructing Natural Swimming Pools are roughly $100 per square foot – which apparently is similar to the cost of a conventional chemical pool.
From my perspective, a simple permaculture-inspired earth pond with a constructed wetland would serve exactly the same purpose. Especially if the pond was being used for multiple functions – agricultural irrigation, aquaculture & food production, light reflection, microclimate, etc. Better yet, take a walk to your nearby pond or creek and save the $80,000-250,000+ that one of these Natural Swimming Pools could cost you.
That said, if you have a design client dead-set on a pool, the comparable pricing and straightforward biological technology of Natural Swimming Pools is an attractive alternative to yet another unnatural chlorine-poisoned turquoise blotch on the landscape. Furthermore, NSPs offer the chance to add habitat diversity and plant species diversity — another way that ecological design can potentially enhance ecosystem health while meeting our human needs.
If you would like a Natural Swimming Pool consultation and feasibility assessment for your home or business from AppleSeed Permaculture LLC, please contact ethan[at]appleseedpermaculture.com.
Plants for Natural Swimming Pools
Note that I was quickly copying these off of slides in the presentation, so many spelling may be wrong. For some interesting tidbits about planting and substrates, you can download my complete notes from the talk here. You can also read Wikipedia’s “Organisms used in water purification” for some ideas.
Do you know any good books on Natural Swimming Pools? Can you correct any errors in these plant lists? Let us know in the comments.
- Typha spp. (cattail)
- Iris spp. (good for P uptake)
- Lythrum salicaria (Purple loosestrife)
- Eleocharis (spike rushes)
- Butomus umbellatus (flowering rushes)
- Baldellia ranunculoides (lesser waterplantain)
- Acorus spp. (blueflag)
- Caltha spp. (marsh marigold)
- Swamp hibiscus
- Myosotus spp. (?)
Deep Water Zone Plants
- Ranunculus spp.
- Myriophyllum verticillatum, spp.
- Elodea canadensis
- Potamogeton lucens
- Chara aspera
- Ceratophyllum spp.
- Water lillies
- Nymphoides pletata
- Ptamogeton natans (?)