›› Margaret Hantiuk
With our rainy winters, local gardeners soon find out that there is not really a water shortage here; but with our dry summers, we do need lots of water, and the issue is a storage problem. The ideal solution is a large cistern (100 gallon minimum) hooked up to your roof downspouts. It is astonishing how much water is shed off a roof in our winter rains. If a large cistern is not an option, then several rain barrels hooked up to your downspouts or a series hooked up together to a main downspout can store a surprising amount of rainwater.
When setting up a larger collection system (over 100 gallons), it is worth checking out the NPC (national plumbing code) and the municipal bylaws. These are presently being reviewed and updated in Victoria. There is a credit on the table for homeowners who collect rainwater instead of letting it run into the storm water system. Storm water runoff can overwhelm the city infrastructure and is full of contaminants, but allowing rainwater to seep down through the soil structure filters it while increasing the groundwater for tree roots (www.victoria.ca/stormwater).
A small pump—there are solar-powered ones—can be set up to run an irrigation system or hoses and sprinklers off your rain barrels. Pumps are more efficient than a gravity-fed system, which works for short distances only. The barrels must be enclosed so that mosquitos do not have entry, and so it is safe for children and pets. An overflow valve or a proper downspout connection kit is necessary so that the excess can be siphoned off, preventing backflow. If you have a large system, the bylaws may require you to hook it up to the storm sewer for your overflow. Large cisterns might require a permit and extra insurance. Be careful to not allow drainage near basement windows, doors, or your neighbours! In the fall, before the winter rains appear, clean out the system.
Stability is vital; usually barrels are elevated on a concrete pad or 6” of compacted road base gravel. Brace them if necessary. One litre of water requires about one kg of support, so they are best left on the ground.
If collecting off of a roof, ensure that there are no lead gutter strips, moss killers, treated wood, or new asphalt shingles if you are planning to irrigate a food garden (these things are otherwise okay for lawns and ornamentals). Filters, which work for bio-toxins but not for heavy metals, are available, and screens are needed to keep out debris.
Another option for collecting rainwater is to avoid impermeable paving materials such as concrete and asphalt. Rather, use ½” screened gravel or wood chips for garden paths and pavers or gravel for driveways and walkways.
Building a swale or rain garden is another option for collecting rainwater. Different than lined ponds, a rain garden is simply a shallow depression lined with permeable materials such as rock, plants, and compost. Rainwater collects naturally and is filtered as it seeps back into the soil. They can be planted attractively with bog plants.
There are many retail outlets that now sell everything you need to set up a good rainwater collection system, and there are professionals that can help you set it up. Check out Canarm’s professional association at www.canarm.org.