Early in the spring of your gardening life, when your herbs and veggies are still small, there’s a certain parent-like charm about trotting around with a watering can or hose, tenderly pouring a life-giving puddle around their little roots. But as your garden grows and your water bills mount up, you quickly realize: there has to be a better way!
And that’s when a design to passively irrigate your gardens, without a drop of city water, begins to sound like a really good idea. Or perhaps you’re looking to stop those water bills before they get started…
Coming in with an ambitious vision for our suburban permaculture homestead, we knew what we were getting into. With a food forest and backyard layout of herb and vegetable gardens, plus a passive solar greenhouse whose thirsty wicking beds had already made a sizeable dent in our budget, we were going to need a large and steady supply of water.
Tracking Our Water To Its Sources
So our first job was to identify where our property already had water coming in…and as with most suburban properties, the primary sources were from roof runoff.
This aerial view shows the major features of the Avis Calgary homestead.
We identified three sources of rainwater runoff that could irrigate our greenhouse and backyard gardens:
- From the west side of our roof, 20,000 litres sluiced down.
- From the downspout of our garage roof, we gained 15,000 to 16,000 litres of water yearly.
- On the east side, 3,000 litres per year ran off the hip roof of our house and our outdoor kitchen.
The question was – how could we direct the water from these sources to go where we needed it? And that was the start of an unobtrusive water capture, storage, and distribution system that transformed our backyard into a self-irrigating oasis in the midst of a very conventional Calgary neighbourhood!
Rob Avis gives a tour of the water-harvesting features of his family’s first permaculture property.
An Aquatic Ecosystem Cleaning Roof Runoff
We started with the runoff from the west side of our house. At the lowest corner of the roof, opposite our back porch, we funnelled the water into a downspout and connecting pipe, leading it quietly under the steps and into a mini tire-pond for temporary storage.
If you were coming down the steps and into the garden, chances were that you’d walk right past that little retention pond – most people did! So what role did it play in our design?
Set up with wetland reeds and sedges we’d gathered from our bioregion, the tire pond became a mini aquatic ecosystem. As the stormwater flowed in, charged with nitrogen and trace elements from the atmosphere, the plants would take up the nutrients and minerals, cleaning the water. When the season was over, we’d cut down the plants and spread them on our gardens as weed-free mulch. Meanwhile, throughout the spring and summer, the pond would attract pollinators and beneficial insect predators…not to mention the birds that came to feast on them!
Verge Permaculture Design course co-instructor Carmen Lamoureux shares about the biodiversity made possible by a water feature in your property
Finding the Goldilocks Swale Solution
During a rain event, the retention pond would overflow into a system of swales that fed our backyard vegetable and herb gardens while providing walkways through the yard. Sounds simple, right? Not exactly! When you’re looking to convey water across X area, you first need to make sure your swales will convey and sink the water….but not too fast, and not too slow. It took a bit of experimentation before we identified the Goldilocks “just right” setup for conveying the water.
Originally, we’d simply used wood mulch in the swales, and it was great for sinking the water and enriching the soil. Moving the water? Not so much. So, we figured, stones would surely convey the water better, yes? With much labour, we removed the mulch, and replaced it with river-rock gravel…but to our disappointment, no, the gravel was not as effective as we’d hoped.
So what was the solution that would convey water through the gardens, while at the same time sinking water into the surrounding soil? The answer: perforated weeping tile on a bed of wood mulch, covered with wood mulch — conveyance plus absorbance. Bingo!
Out came the gravel, and in went the wood mulch and weeping tile. This, we found later, provided a surprise additional benefit: the wet mulch became an ideal habitat for worms, who would shuttle nutrients into the soil of our gardens, enriching the soil without need for further work on our part.
In time, of course, between the worms’ work and the passage of our feet over the swales, the mulch flattened out and began to break down. At that point, we’d simply bring in a new load of mulch and spread it over the old, continuing the cycle.
Rob tells the story of the swale experiments.
With our technology perfected, we turned to the 15,000 to 16,000 litres of water coming from our garage roof. As close as that roof overhang was to our gardens, harvesting the runoff was a simple matter: we extended the downspout outward at an angle, so it descended directly to the corner of our garden, where we joined it up with the weeping tile of another system of swale trails.
Culvert Containment
That left the 3,000 litres per year running off the hip roof of our house and our outdoor kitchen, which was running under the kitchen floor hardscape and causing all sorts of problems. And for this, we had two purposes in mind: irrigating the swale trails running through our kitchen garden, and irrigating our passive solar greenhouse, whose wicking beds had been thirstily guzzling municipal water for the past years (to the great pain of our budget!).
This was a narrow strip of lawn next to the house; swale trails were not an option here. So where could we sink the water? With the advice and help of Jordan Hoch of Gnome of My Own, we explored all the options and came upon the simplest, most elegant solution: an underground cistern below the patio paving between the house and the outdoor kitchen.
After digging down to clay to eliminate the possibility of frost heave, we double-lined the pit and laid down four massive culverts side by side, sloping toward the back wall, then covered them with the pavement of our patio. A gutter on the kitchen side captured the water from the patio pavement and led it down a slight slope to the back of the patio, where it funneled the runoff into the cistern.
Rob explains the mechanics of our underground rain cistern.
Now, when you’re living in a cold climate like ours – or any four-season climate – you always need to bear in mind the effect of winter weather on a water-harvesting system. Some means of draining the system is necessary to prevent freeze-thaw disasters. So we included a 12” perforated pipe from the pavement to the bottom of the cistern, with a submerged sump and hose allowing us to pump the water out at season’s end.
During the summer, however, that hose gave us access to water for the greenhouse wicking beds, as well as for washing hands and dishes in the patio kitchen. No more astronomical city water bills for outdoor water use!
Our Cistern Overfloweth
To allow the cistern to irrigate our swale trails, Rob drilled a hole through its underground containment wall and into the pond liner. Outside the wall, he plumbed it with a standpipe to set the level of the water in the tank and control overflow. From there, he ran a pipe to direct that overflow past our back porch steps and into a gravel lens, where a weeping tile pipe surfaced to convey the water through the swale trails.
Rob explains how our cistern linked up with the swale trails to feed our backyard gardens.
How Much Can You Save With Passive Irrigation?
When you add up the litres we use in irrigating our food forest, backyard gardens, and greenhouse wicking beds, the cost of city water alone – never mind the environmental impact during drought – could be potentially prohibitive for many homeowners!
Using the water provided by nature, however, with simple tools and retrofitting, you can save a fortune while creating an abundant supply of food for your family and neighbours.
Want to learn more? Check out our Essential Rainwater Harvesting book and tool HERE!
