Capturing Rainwater, No Barrels Needed

Well hello rain! After February fizzled into a big fat zero, I was worried our much hyped El Nino got stage fright and snuck away. Perhaps not so! It’s downright soggy as I write this. There’s slick sticky mud, standing water (I think those are called puddles, if I remember correctly), and moss growing on the north side of my fence. 

Last year, I began earnestly working on my backyard. It was a mostly blank slate, but I developed a design and began the framework for an edible landscape/food forest. An important part of that framework was to design for capturing rainwater, specifically the runoff from my roof. 

When most of us think of rainwater capture, we think of rain barrels, tanks, or cisterns. That’s ok, but it presents a couple of problems—cost and space. Installing a storage system that holds a meaningful amount of water gets expensive.  It would also take a proportionally large amount of space from my postage-stamp-sized property.  

The roof over my house, garage and porch cover roughly 1700 square feet. Half of that roof drains to downspouts in my backyard. In an average 18 inch rainfall year, >9000 gallons run off that half of the roof!  Even in a 12 inch year, that’s >6000 gallons. I want that water! More importantly, my landscape wants that water, and the last place that water should be going is down the street into the storm drain and sewer. So what’s the solution? 

Slow it, spread, it sink it, directly into the landscape. How? In my case, with swales. 

What’s a swale?  Think of it as a ditch on-contour, meaning that the ditch follows the contour of my property, making it level, with a level bottom.  Kind of like a long narrow pond.  When water runs off of my roof, it is directed into my swales, where rather than draining away, it slows, spreads, and sinks into the soil where it wicks into my adjacent beds, infiltrates below, and recharges our groundwater. 

Newly dug swale on-contour

It gets better though. Because my property is so flat, I had a lot of latitude for placement, and because I have limited space, I opted to place my swales in my pathways.  Wait, what? Yes, my swales are my garden paths. Once the swales were dug, I backfilled them with wood chips. The result is that my swales hold all the runoff while the wood chips keep the surface walkable. 

Swale-path completed, and just after a rain event

As a bonus, wood chips hold moisture like a sponge, slowly releasing it to the surrounding soil over time. They also act as a deep mulch, keeping water in the underlying soil, and they are a food source for beneficial fungi. The fungi decompose the wood over time leaving improved soil structure and rich humus behind. Isn’t nature just fantastic? 

The cost of this project was a length of drain pipe to divert the runoff, some time with a shovel and level, careful planning, and a load of free wood chips. 

The swales are in their second winter now, and are taking on all the rain fed into them without problem.  So far I’m thrilled with the results.